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NATIONAL SECULAR SOCIETY
PHYSIOLOGY OB' TEDE HOME.
DIGESTION.
As it will be impossible for me in the small compass of four
lectures to deal with the structure and functions of every
organ of the body, I propose to select those an elementary
knowledge of which will be most useful in home life. Much
discomfort, much diminished vitality, much actual disease,
are caused by ignorance of the simplest facts about our own
bodies. How we digest, how we renew wasted material,
how we breathe—these are matters closely concerning every
one of us, and yet a majority of people are densely ignorant
about them, and a vast mass of unnecessary suffering is the
direct result of this ignorance. The object of these four
lectures will be to throw a little light on the functions of
digestion, circulation and respiration.
The most indifferent glance at the world of which we are
a part reveals to us two great classes of phenomena; we
see one kind of matter inert, passive, receptive, wrought
upon by influences surrounding it but not actively moulding
in return: clay, rock, metal, earth, all these are. examples
ready to our hands, and we label them non-living matter.
The man lying on the cliff distinguishes between himself
and the chalk on which he lies. He says, “ I live ; that
lives not.” The distinction may be accepted as a rough one,
although it would be hard enough to draw the exact line
which separates the living from the non-living, but for con
venience sake we separate off the palpably living, and we
call the science which deals with them Biology, the science
of living things (/?ios, life; Ao-yos, a discourse).
Oui' work falls under this title. But the man on the cliff
sees life around him other than his own ; there is life in the
trees, in the grass, in the flowers. Of living things there
are again too great classes, and though the student knows
that these again melt the one into the other, yet in the higher
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Physiology of the Home.
forms of each there is such great divergence that we label
them off separately once more, and call them severally
Animal and Vegetable, and the sciences which deal with
them Zoology (£oov, animal; Xoyos), and Botany (ftoravg, a
plant). Our work, again, falls under Zoology. We narrow
it down yet further by putting on one side all animals save
the highest, Man. And in studying man we find two great
classes of facts ; facts of Anatomy (ava, up ; re/zvo, I cut),
facts of structure, which have to do with the form, material,,
and position of the organs of the body; and facts of Physi
ology (^>vcris, nature: Aoyos), facts of function, which have
to do with the work discharged by the organs. Both these
last classes of facts will come under our notice, for though
I shall deal mainly with functions, it will be necessary to
touch briefly on the organs with which the functions are
connected.
If you take a rope and use it constantly the material
gradually wears away by friction until the rope is no longer
serviceable ; you throw it away and get a new one. If you
work your muscles constantly the material of your musclesgradually wears away; you do not, however, require to
throw them away and procure new ones. Why? The
material of the rope is worn away bit by bit, and is not
renewed ; the material of the muscles is worn away bit by
bit and is renewed. The wearing away of the muscle is as
real as the wearing away of the cord; a man weighed before
and after many hours of hard muscular exertion actually
weighs less at the end than he did at the beginning. Even
if he be idle the wearing away goes on, although less rapidly
than when he is actively exerting himself. The place of'
this lost material must be filled up, else the muscle will wear
out like the rope. The place of the wasted material isfilled up in the living; and the discomfort caused by the
blood exhaustion, consequent on repairing the waste, is
known as the sensations of hunger and thirst, and the
material is ultimately renewed by means of the food which
appeases the want.
There are four chief ingredients in organised bodies;
other substances also enter into them, but they are mainly
made up of these four. Of these, three are gases, and one
is a solid. The three gases are hydrogen, oxygen, and
nitrogen; the solid is carbon. These four substances are
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Physiology of the Home.
now before you, three are invisible, one is visible. But
the three invisible ones are easily distinguished from each
other by their properties. Without going fully into these—
as the Chemistry of Home will be dealt with by my suc
cessor—I can show you that each apparently empty bottle
contains a different substance. I apply a light to the first;
it burns ; it is hydrogen. I plunge a light into the second ;
the light is extinguished; it is nitrogen. I blow out a light
leaving a red spark, and place it in the third; the spark
bursts into a flame ; it is oxygen. We have then, here, four
different substances, from which we are to obtain muscle
and nerve, blood and sinew, by which we are to replace the
wasted materials in our bodies. The materials are scarcely
promising. A starving man would hardly thank us for our
three bottles and our lump of charcoal. But these four
substances, elements as they are called, useless for food at
present in their separate condition, have the useful property
of combining very readily. Three chief combinations, or
compounds, must be considered; water, carbonic acid, and
ammonia. For convenience sake we use only the first letter
of each element, instead of the full name. We have :
H
0
N
Hydrogen
Oxygen
Nitrogen
These form :
h2o
Water
co2
Carbonic Acid Gas
c
Carbon
H3N
Ammonia
And this is the first step towards our food-stuffs. The
water is at once utilisable, but the other two are not yet
food for us. But they are food for plants. The plants take
into themselves the CO2 , and expelling the oxygen retain
the carbon; they take the nitrogen from the ammonia and
from ammoniacal bodies, and within themselves they so re
combine them as to form food-stuffs suitable for animals.
You will notice that the first compounds are each made up
of two elements ; the next set, manufactured by the plants,
are mostly made up either of three or of four. They con
sist either of carbon, oxygen, and hydrogen, or of carbon,
oxygen, hydrogen, and nitrogen. The two great divisions
of food-stuffs depend on the presence or on the absence of
nitrogen.
Let us take the non-nitrogenous, or as they are some
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Physiology of the Home.
times called the non-azotised, first. They are the food-stuffs
containing only carbon, oxygen, and hydrogen. These are i
(1) All the starchy matters; if you look at thin slices,
sections, of potatoe, rice, sago, corn, and many other
vegetable productions, under the microscope, you will see
grains of starch in them ; that starch has been manufactured
by the plant and contains nothing but carbon, hydrogen,
and oxygen in certain definite proportions. Gum, and
other amyloids (from amylum, starch) are also found in
plants. (2) All the sugary matters : the sugar of every-day
life is obtained from the sugar-cane, the maple and the beet
root ; the sweetness of ordinary fruit is due to the
presence of another kind of sugar. Yet other kinds are
formed by animals, and are present in milk, in muscle, in
liver. (3) Fats and oils : some of these are formed in plants
—such as palm-oil; others in animals. Now the whole of
these three classes of food-stuffs have one main use when
taken into our bodies : they produce heat. I must again so
far trespass into chemistry as to tell you that heat is caused
by the union of oxygen with some other substance. When
oxygen enters into combination with other bodies heat is
always given out. The substances that we have been con
sidering part with oxygen very readily; they give it up as
they are decomposed inside the body, and thus animal heat
is maintained. Hence the necessity of starchy, sugary, and
oily food-stuffs; the colder the country the more need for
fatty articles of food. The Esquimaux finds the blubber of
the whale delicious ; the Arab would turn from it in disgust..
Why ? because the bitter cold of the North chills the body,,
and the body, in order to keep up the temperature necessary
to life, needs a large supply of fatty matter, which readily
yields up its oxygen for new combinations, that is which
gives the agent needful for the production of heat. On the
other hand the warmth of Arabia renders a comparatively
small amount of fatty matter necessary for the maintenance
of animal heat.
There are certain other food-stuffs, consisting of carbon,
oxygen, and hydrogen, which are mainly stimulating. Such
are the acids produced in fruits, the alcohols, and ethers.
These substances act rapidly on the body, but their effect is
not permanent. Brandy may appear to warm more imme
diately than a good meal, in which fat plays a part, but
�Physiology of the Home.
5
an hour afterwards the man who has taken the brandy will
be colder than before, while the man who has eaten, will
be thoroughly warm. Alcohol—generally termed spirits—
is invaluable where a stimulant is necessary, say in the
case of a person insensible from exposure to cold ; it is not
good as an ordinary article of diet.
I have said that the chief use of the starches, sugars, and
fats is as heat-producers ; the chief use of the second great
class of food-stuffs, the nitrogenous or azotised, is as tissue
formers, that is, as builders up of the various tissues of
the body. It may be well to note, in passing, that while
nitrogenous food-stuffs are primarily tissue-formei’s, they
do help, in small measure, to produce heat, and that while
non-nitrogenous food-stuffs are primarily heat-producers,
they also, to a small extent, aid in the formation of. tissue.
Nature refuses to be marked off by our sharp lines of
division, and in her order work of one kind glideth ever
into work of another.
In this great second class of food-stuffs, nitrogen—as the
name of the class implies—is always present in combina
tion with the carbon, hydrogen, and oxygen.. The chief
tissue-forming substances are albuminoids, like albumin,
the white of eggs, and gelatinoids, like gelatin, the soft
matter in bone. The albuminoids are some vegetable, some
animal. Albumin is present in vegetables generally ; legumin
is found in such vegetables as peas, beans, pulse, etc.;
gluten in cereals of all sorts. Hence the great value of
wheat and of beans of all kinds as articles of food. Animal
albuminoids are found in meat, blood, milk, and eggs.
Some nitrogenous food-stuffs, like some non-nitrogenous,
are stimulating. Among these we find Thein, the essential
characteristic of tea ; Caffein, that of coffee ; Theobromin,
that of cocoa. These, like alcohol, are stimulants, but the
nitrogen present in them adds to their nutritive power.
If you take these various food-stuffs, sugar, starch, fat,
albumin, and so on, and place beside them some muscle,
some nerve, some brain, and some blood, you still have the
problem before you: How is the food-stuff changed into the
materials which make up the body ? In their solid form
these substances are useless. There are no openings,
whereby solid matter can pass into the blood and reach the
tissues ; all nourishing matter passes into the blood by a
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Physiology of the Home.
process called osmosis. Osmosis means passage through a
membrane. If you take a bladder and fill it with sugar
and water, and then place it in a vessel of pure water for
an hour, you will find at the end of the hour that the
water in the vessel is sweet. Some of the sugary water
has passed out of the bladder into the vessel, while some of
the pure water has, in turn, passed into the bladder. This
exchange of liquids through a membrane which has no holes
in it is called osmosis. By osmosis all the nutritive part of
our food passes into the absorbent vessels, and it is, there
fore, absolutely necessary that it shall be dissolved, that it
shall be in solution, otherwise it cannot be taken up and
used in the reparation of tissue. The next lecture will deal
with the organs of digestion ; at present I want only to show
you the changes that take place in the food.
Take, first, the sugars. These are soluble in water.
Place a piece of sugar in cold water inside a bladder; place
the bladder in water. The sugar will dissolve, and by
osmosis will pass into the water outside. We can prove its
presence there by adding to the water copper sulphate and
caustic soda, and then heating: if sugar be present, a
red-brown powder is precipitated. The sugar is, then, very
easily prepared for osmosis; it dissolves in simple water.
But the starch presents a difficulty. I have here some
starch that has been placed in a bladder with water, and
surrounded by water for twenty-four hours. But the water
outside is as pure as when placed there. The starch has
not passed through; we test the water by pouring in a
little iodine, a substanee which gives a purple re-action with
starch; we find nothing. Starch, then, as starch, is useless
in the body. But in this second bladder starch has been
placed, mixed with saliva, with the fluid poured into the
mouth while we are eating. We test the water outside, and
we find it is not pure water; it gives the characteristic
re-action for sugar. What, then, has happened ? The
saliva has turned the insoluble, and therefore useless, starch
into soluble sugar, ready to be taken up and used in the
body. Whenever you eat bread this change goes on in the
■mouth. Hence the importance of thoroughly chewing the
food, and the importance of checking children when they
eat too fast. If bread is “ bolted,” the starch in it remains
starch ; it is useless for nutrition. It is true that there is
�Physiology of the Home.
T
another fluid (from the pancreas, or sweetbread) which
takes up the work left undone by the saliva, but if the saliva
has not done its share too much work is thrown on the
other ; hence discomfort, and indigestion.
The fats are not affected by the saliva, and they pass
through the stomach unaltered. They become very finely
divided, made into “ an emulsion ” as it is called, in the
upper part of the small intestine, and so become capable of
osmosis.
The albuminoids are insoluble in their native state, but
are acted upon in the stomach by the gastric juice, and are
turned into what are called peptones. Peptones are merely
albuminoids, so far as their composition is concerned, but
their properties have been changed. You know that if you
boil an egg the white “ sets ” ; but white of egg which has
been standing in gastric juice will not “set”; it is not
affected by heat. White of egg will not pass through a
membrane, and therefore cannot be absorbed ; but white of
egg, after standing in gastric juice, can pass through, and
can be absorbed. Albuminoids, then, are changed in the
stomach itself into the soluble form of peptones, and become
ready to be taken up.
The food-stuffs, thus rendered soluble, are absorbed by a
large number of little vessels which project into the small
intestine; these vessels run togethei’ into one large one ; the
large one opens into a vein, and in this way the nourishing
part of the food passes into the blood. The blood carries it
to all the tissues of the body, and each tissue takes up the
kind of material that it requires to make good what it has
lost, and so the tissues, constantly wasting, are as constantly
built up again.
It will now be very plain to you that the quantity and the
quality of food required will vary very much according to
the age and the work of the person dealt with, and will vary
also with the climate in which he lives. A man who works
hard, and therefore uses up his tissues quickly, will require
more food than an idle man. An ordinary man in good
work requires daily about 44,500 grains of food, and of this
4,000 grains should be carbon and 300 nitrogen (Huxley)..
He may choose for himself the form in which he will take
them. To live entirely on meat is not good, for 1,000 grains
of meat contain (roughly) 100 of carbon and 30 of nitrogen,.
�Physiology of the Home.
so that it would be necessary to eat some 6 lbs. of meat to
get carbon enough, although 1^ lbs. give sufficient nitrogen.
'On the other hand, if you live only on bread, you must
eat twice as much carbon as you require in order to
get enough nitrogen. In either case the system is
overworked by more matter being put into it than is re
quired. A mixed diet of animal and vegetable food is the
-diet recommended by Physiology. Animal food seems
especially necessary for the reparation of nervous tissue, but
further experiment is wanted before we can lay down
■exactly the kind of food needed for the reparation of each
tissue of the body.
The food of children should be, above all things, nourish
ing and easily digestible. The corn-flours so largely sold for
children’s food are mostly deficient in gluten, while rich in
starch, and are not, therefore, sufficiently tissue-forming.
The same is true of ordinary white bread. Milk, whole
meal bread, beans of all sorts, oatmeal, and fruit, with com
paratively little meat, form the most wholesome diet for
■children.
The mineral constituents of food have been omitted in
this rough sketch; with the exception of salt, they are
■taken in as part of ordinary animal and vegetable food,
and are found unaltered in the various tissues. The chief
of these are : Sodium Sulphate and Sodium Phosphate in
the blood and secretions; Potassium Chloride, Potassium
Sulphate, and Potassium Phosphate in the muscles; Cal
cium Carbonate, Calcium Phosphate, and Magnesium
Phosphate in the bones; Iron Oxide in the blood.
PRICE ONE PENNY.
London: Printed by Annie Besant and Charles Bradlaugh,
28, Stonecutter Street E.C.
�PHYSIOLOGY OF THE HOME.
ORGANS OF DIGESTION.
------ --------
In speaking last week of facts of Zoology, we divided them
into two classes:—Anatomy, which includes all facts of
.structure; Physiology, which includes all facts of function.
Our work this week is chiefly anatomical; we are to deal
with the Organs of Digestion.
Let us be sure, first, that we understand the words we are
using. What is an organ ? What is digestion 2
An organ is any special portion of a body which is set
.apart for any special kind of work. In the lowest animals
all parts of the body do all kinds of work equally well. The
Amoeba, for instance, grasps, eats, digests, breathes all over
its body. There are no special portions set apart for special
work : that is, there are no organs. A little higher up in
the scale a mouth appears, and a bag that receives the food.
Instead of taking in food all over, the food is taken in at
the mouth. The mouth is the organ for food-reception, and
so on. The higher the animal, the more complete is this
division of labor, and the organs become more and more
different, more and more perfect in the discharge of their
particular work.
Digestion is, to borrow Dr. Aveling’s definition, “ the
preparation of food for absorption.” Absorption is the
taking up of digested food, in order that it may be carried
to the blood, and so reach the tissues ; digestion is getting
the food ready for absorption, so changing it that it may be
fit to be taken up.
To sum up, “ organs of digestion ” are specialised parts of
the body which prepare food for absorption.
All the changes undergone by the food during digestion
take place in the alimentary canal. Aliment is merely
another name for food, and the alimentary canal is the tube
.along which the food passes. This tube begins at the
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Physiology of the Home.
mouth and ends at the anus, and is about 30 feet in length.
You will remember that there are no openings in it save
these two, excepting, of course, the openings into it of ducts,
little tubes, from its own appendages. Imagine, then, a long
tube, expanding at one end into the mouth, expanding again,
some way down, into the stomach ; twisting and turning very
much as the small intestine ; expanding for the third time to
form a little side-bag, the cæcum ; widening to make the
large intestine which encircles the small, and the short com
paratively straight rectum. This canal has three coats : one
is of mucous membrane, and forms the lining of the canal,
so that it comes into contact with the food ; the middle one
is of fibrous tissue, and serves to connect the important
inner and outer coats ; the outer coat is muscular. This
last coat is composed, excepting in the stomach, of two
layers of muscles. One layer is of fibres running round the
tube ; the other layer is of fibres which run lengthwise along
the tube. Now muscle has one great quality, it contracts.
If you take a piece of indiarubber and pull it, it yields to
your pull and stretches ; when you let go, it springs back.
You say it is elastic ; it lengthens easily and shortens again
when released, or you may shorten it by pressure and it will
lengthen when released. This is just what muscle does; it
stretches readily and contracts readily. Hence the use of
the two layers in the muscular coat. The circular layer
contracts, and makes the tube narrower and longer; the
longitudinal layer contracts, and makes it shorter and wider.
We shall see presently how useful these contractions are.
The alimentary canal has, further, various appendages con
nected with it, each appendage having its own definite
function. Having thus briefly described it as a whole, let
us now turn to details.
The Mouth and its Appendages.—The mouth is nearly
oval in shape, and is the organ which receives the food, and
in which digestion begins. The soft red lining is the
mucous coat. The chief appendages are the tongue, the
teeth, and the salivary glands. The Tongue may be dismissed
in a sentence : it is a thick strip of muscle, the organ of
taste, and serves to turn the food about in the mouth so as
to submit it to the action of the teeth, and finally to roll it
into a ball and pass it backwards to the top of the gullet.
The teeth are the organs of mastication ; their work is to
�Physiology of the Home.
3
■crush and bruise the food, to break it up. The use of this
is Obvious. If a cook is going to make soup, she does not
throw the bones in whole : she breaks them up into pieces,
so that all parts of them may come into immediate contact
with the water, and thereby more quickly and readily yield
up their useful components. What the cook does to the
bones, the teeth do to the food. By breaking it up, all
parts of it come into contact with the saliva and more
readily submit to its action. How necessary this is, you will
remember from last week. The teeth, however, are not all
alike ; the first set, or milk-teeth—cut during infancy are
twenty in number. These teeth begin to develop m the
seventh week of fœtal life ; a little groove appears, running
along the jaw, and in this groove. grows up a ridge of soft
(mucous) tissue ; parts of this ridge die off, and so leave
little projecting pieces, called papillæ ; each of these repre
sents a future tooth. I have not time to describe all the
changes that go on ; it must suffice to. tell you that the sides
of the groove bend over and close in the papillæ, so that
when the child is born you see no groove and no papillæ,
but only the smooth surface of the gum. The. papillæ
■develop into teeth, hard matter being laid down in them,
and they cut their way through. The permanent teeth have
been forming at the same time, and move gradually round
underneath the milk-set. The latter fall out from about
the sixth year onwards, and the permanent teeth come
■through ; they are supposed to be complete about the twentyfirst year, when the “wisdom teeth ” ought to be. through.
There are 32 permanent-teeth ; 8 incisor, or cutting teeth,
the “ front teeth ” ; 4 canine, the long pointed teeth on
either side, above and below ; 20 “ double teeth, for
grinding. The canine teeth are for tearing, and are. of no
particular use to us, but they are interesting as showing our
descent from animals who tore their food. A glance at a
picture of a double tooth shows the structure of all ; you
see the fang, which is imbedded in a depression (called an
alveolus) and holds the tooth firmly in its place ; then comes
the neck, the narrower part, and then the crown, visible
above the gum. This crown is covered with enamel, the
hardest tissue in the body, which protects the tooth from
injury. If this gets worn away, or injured, the softer parts
underneath rapidly decay. Hence the importance of keep
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Physiology of the Home.
ing the teeth thoroughly clean, and of not taking into the
mouth substances which injure the enamel. Inside the
tooth is a cavity filled with pulp and with a nerve running
into it. Toothache constantly arises from the hard part
of the tooth getting worn through, and this nerve becoming
exposed. When this happens, the only thing to do is to
have the nerve killed and the hole filled up—stopped, it is
called: the remainder of the tooth may thus be saved.
The Salivary glands are six in number—-three pairs, the
parotid, submaxillary, and lingual. Each of these consists
of masses of cells, or vesicles, and from these masses of
vesicles go ducts which run together to form a larger duct,
which opens into the mouth. A gland is an organ which
secretes. To secrete (from secreto) is to separate one thing
from another, to take out one kind of substance and leave
the rest. The cells, or vesicles, of the gland do the work,
and they take out of the blood substances which are needed
for use in the body, or sometimes which need to be expelled
from the body. The salivary glands secrete saliva, and they
pour this substance into the mouth and there it works, as
we saw last week, on the starchy constituents of food.
From the mouth the food passes over the windpipe,
which is closed by a sort of trapdoor, into the pharynx, thepart just behind the mouth. From the pharynx a tube,
about nine inches long, goes to the stomach, and this tube is
called the (esophagus. And now comes in the use of our two
muscular layers. Food which leaves the pharynx does not
tumble down into the stomach. It is seized by a ring of the
circular fibres, which contract on it; when they let it go,
the next ring seizes it, and so it is handed on step by step
till it reaches the stomach. Some of you may have seen a
conjurer drink water while standing on his head, and may
have wondered how it got up, instead of down, to his
stomach. It is the circular rings of the oesophagus that do
all the work, and as the food is handed on to ring after ring, it
makes no difference whether it goes upwards or down
wards.
The Stomach. The oesophagus opens into the stomach,,
the expanded part of the alimentary canal, the opening
being closed except when food is passing by a ring called a
sphincter muscle. The stomach is like a bag, larger on the
left side than on the right, and lies across the body just.
�Physiology of the Home.
5
below the liver. As it is part of the alimentary canal it
has, of course, the regular three coats, but the muscular
coat has three layers instead of two, and in addition to the
longitudinal and circular it has also a layer of oblique fibres,
and when all these are contracting and lengthening a kind
of churning motion is given to the contents of the stomach,
and the food is turned over and about, and thoroughly
mixed. In the lining, or mucous coat, there are a number
of little glands of different kinds, which secrete fluids and
pour them into the stomach. The most important of these
are the peptic glands, which secrete the gastric juice.
When albuminous matter arrives in the stomach, this
gastric juice is secreted and is poured out; the movements
of the stomach mix the juice well up with the food, and
the changes we spoke of, and which you saw last week, take
place. As the gastric juice does its work the soluble
portions of food—called chyme—are pumped out of the
stomach into the small intestine. They pass through
another sphincter muscle, the pylorus or door keeper, and
until the stomach digestion is finished, this muscle will not
allow any solid matter to pass. When the stomach has
completed its work neither food nor chyme remains in it; it
is left perfectly empty, and the secreting action of the glands
stops entirely.
The Small Intestine and its Appendages. The small
intestine is about twenty feet long, and is divided into three
districts, the duodenum, jejunum, and ileum. In the duode
num, active digestion continues. Into this part of the intes
tine are poured the secretions from the liver and pancreas,
as well as fluids secreted by little glands in its own lining
mucous membrane. The liver is the large organ which
you see covering the stomach, and lying to the right side of
the abdominal cavity. It secretes the bile, and as it secretes
constantly while the bile is only used intermittently, the bile
is stored up in the pear-shaped organ attached to the liver,
called the gall-bladder. The exact work of the bile is still
rather a matter of dispute. It appears to act as a stimulant
to the intestine, it is to some extent an excrementitious
product—that is, a waste fluid carrying off matters injurious
to the body—and it is also certainly antiseptic—that is, pre
vents decomposition. The pancreas lies partly in the fold
of the abdomen and secretes the fluid which, as we saw last
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Physiology of the Home.
week, makes an emulsion of the fats and oils, and also
finishes work left undone by the saliva in turning starch into
sugar. The pancreatic fluid runs down a little duct, and
joins the duct from the liver, the two opening together into
the duodenum.
The jejunum is so called because it is generally found
empty after death, the ileum because it is much twisted. All
these three parts of the small intestine are thickly studded
with villi, little projections like the finger of a glove, which
stick out into the canal of the small intestine. Each villus
has a little tube, or tubes, in it, called lacteals, and all these
are plunged into the digested food—now called chyle—and
suck it up as fast as they can. They absorb the nutritive
matter, the fluid passing through their delicate walls, as you
remember, by osmosis. As the villi continue to suck up the
fluid, the contents of the intestine become more and more
solid ; they are slowly passed along by the muscular move
ments of the intestine until they arrive at the cæcum.
The Large Intestine.—The large intestine commences
at the cæcum, and is about five feet long. The cæcum itself
is a mere blind bag, small in man, but large in many of the
lower animals. So far as we know, it serves no useful
purpose in man, but it is occasionally the cause of disease,
by lodging hard particles which give rise to inflammation.
When the digested food reaches the cæcum, it has yielded
up most of its nutritive material, and the remaining matter
is useless, and has to be expelled from the system. The
large intestine, here called the colon, passes first upward
(ascending colon), then turns to the left and crosses the
body (transverse colon), turns downwards (descending colon),
and then makes a remarkable S-like turn (sigmoid flexure).
Throughout its length it is sacculated—drawn into little
bags, or sacculi—and as the superfluous portion of the food,
now called fæces, passes along it, being carried on as before
by the muscular movements of the intestine, it gets lodged
in the sacculi, and is so prevented from falling back between
the contractions. This muscular movement—peristaltic
action, as it is termed—may be very easily seen by pinching
the intestine of an animal which has been lately killed : a
slow wave of movement will run along it. The last six or
eight inches of the intestine are named the rectum, and
extend from the sigmoid flexure to^the anus. The rectum
�Physiology of the Home.
7
is not sacculated, increases in diameter as it descends, and
ends in a sphincter muscle.
You may reasonably ask, what causes all these move
ments, whereby the food is propelled along the alimentary
canal, from mouth to anus? We are not conscious of these
muscular contractions, noi’ are they, mostly, under the
control of the will. When a morsel of food has reached
the top of the oesophagus it passes out of our power. We
do not even feel it pass down the oesophagus unless it is very
hot, very cold, or actively injurious. Unhappily our time is
too brief to allow us to go fully into this interesting question.
It must suffice to say that muscle left to itself does not
contract.
But distributed to all these muscles of the
alimentary canal are a number of fine cords called nerves.
When the nerve contracts it moves the muscle, and all the
muscular movements are the result of nervous action.
But you may again ask : What causes the nervous action ?
It is a property of nerve to respond to a stimulus. When
the nerve responds to an external stimulus, and responds
without sensation—that is, the stimulus causes action, but
we are unconscious of the action—such nerve-action is called
reflex. Reflex action is action caused by external stimulus,
and performed without sensation. The whole of the move
ments of the oesophagus, stomach and intestines are reflex.
The stimulus is the food pressure. The food presses against
the delicate nerve fibres; the nerve-fibres, responding to
this stimulus, are set in motion; moving, they move the
muscles to which they are distributed, and the muscles con
tract. The food is pushed on by the contraction, presses
against fresh nerve-fibres, and so on. If the nerves are
destroyed, the muscular contractions stop, showing that the
muscles do not contract of themselves. Destroy the nerves,
and the food may press for ever against. the muscles with
out causing them to contract.
We must now return, in conclusion, to the small intestine,,
and see what becomes of the chyle. We have already seen
that each villus contains a tube or tubes ; these minute tubes
run into glands (mesenteric glands) in the mesentery, the
thin membrane that connects together the folds of the
intestine, and here the chyle undergoes considerable changes.
Corpuscles—small rounded bodies that we shall speak moreof when we come to deal with the blood—make their
�8
Physiology of the Home.
appearance, the constituents of fibrin are formed, and the
chyle changes in color from white to a pale reddish-yellow.
This modified chyle is collected in a triangular cavity or
cistern (yreceptaculum, chylC), which lies at the back of the
body, against the backbone. From this cistern a duct
(thoracic duct) runs up along the backbone as far as the
root of the neck, being from eighteen to twenty inches in
length ; at the top it turns to the left and arches downwards,
entering the blood system at the junction of the internal
jugular and subclavian veins, and pouring its contents into
the blood.
We have thus traced our food from its four primary
elements until it reaches the blood, which is to carry it to
repair the tissues, and have briefly sketched the organs
which work upon it and change it. The next lecture will
deal with the organs to which the food is now committed,
and with the way in which the blood nourishes the body.
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�PHYSIOLOGY OF THE HOME.
CIRCULATION.
We defined an organ last week as “ any special portion of a
body which is set apart for any special kind of work.” The
first things we have to consider to-night are the Organs of
Circulation, the special portions of the body concerned in
the circulation of the blood.
The organs of circulation are of four kinds : the heart,
the arteries, the capillaries, the veins.
The Heart.—The heart lies obliquely between the lungs
in the upper half of the trunk, the apex pointing forward
and rather to the left, the broad upper end being in the
middle line of the body. The average adult human heart is
about 5 inches long, 2^ inches thick, and 3|- inches broad in the
widest part. It is conical in shape and hollow, and is divided
within into four compartments, the right and left auricles,
and the right and left ventricles. A septum (septum, a fence)
runs from base to apex, completely dividing the right side
from the left, so that there is no communication possible
between the two sides in a healthy person. This septum has
an auricle and a ventricle on either side of it, and each
auricle communicates with the ventricle of its own side.
The material of the heart is muscle, of which you will
remember the chief characteristic is contractility. The
muscular walls are not of the same thickness throughout;
those of the auricles being considerably thinner than those
of the ventricles, and the wall of the right ventricle being
thinner than that of the left. You all know that exercise
strengthens muscles ; the arm of a blacksmith is larger and
harder than that of a writer, and when we find that there
is so great a difference between the walls of these cavities
we may feel sure that the greater thickness is the result of
greater work. The work of the heart is to propel the blood,
and the propulsion of the blood outside the heart falls wholly
on the ventricles ; the muscular walls of the ventricles,
being more used, generation after generation, have become
permanently thicker than those of the auricles; similarly,
while the right ventricle has only to propel the blood round
�2
Physiology of the Home.
the lungs, the left has to drive it all round the body, hence
the muscular wall of the left is thicker than that of the
right. The openings (auriculo-ventricular orifices) between
each auricle and the ventricle of its own side are oval in
shape and surrounded by a fibrous ring. The openings are
guarded by valves, folds of the lining membrane of the heart,
which are in such a position that they can completely close
the aperture. On the right side the valve is composed of
three triangular segments (tricuspid valve, from tres, three,,
and cwspzs, a point), while the similar valve on the left
side has two (mitral valve, so-called from its supposed
resemblance to a mitre). The description of one of these
valves will serve for both. The segments of the tricuspid
valve are attached by their bases to the fibrous ring, their
points being free. From these free points and from the
surface on the ventricle side, go thin cords of tendon, a
fibrous inelastic tissue, and these cords (cAonfe tendinaf are
attached to little muscular pillars (musculi papillares} three
or four in number, projecting from the inner wall into thecavity of the ventricle. These cords are long enough to
allow the segments of the valve to join each other and com
pletely close the auriculo-ventricular opening ; they are not
long enough to allow the points of the valves to be pushed
up into the auricles. We shall now be able to understand
what happens when the heart “ beats,” that is contracts and
expands ; the “ beat ” is caused by the apex of the heart
striking against the wall of the chest. Imagine the heart
empty, or, if you are wise, get a bullock’s heart and experi
ment ; imagine some fluid pouring into the right auricle, till
it is full; the auricle contracts and presses on the fluid; the
fluid tries to escape, and the easiest way out of the auricle
is through the opening into the ventricle ; it pours through,
the valve yielding readily and being flattened against the
walls of the ventricle by the rush from above ; the ventricle
becomes full and begins to contract, forcing the fluid once
more to escape. Meanwhile the segments of the valve have
been pushed up as the ventricle fills until they nearly meet,
and the fluid, pressed by the contraction of the ventricle,
pushes against them and completely closes them; it con
tinues to push against them, but the chordce tendince
prevent them from going upwards any further, and the
fluid is compelled to escape into an open tube, called
the pulmonary artery, leading out of the ventricle. A very
sharp hearer might say : “As the ventricle contracts the-
�Physiology of the Home.
3
sides come nearer together, and therefore the valve would
gradually rise into the auricle if pressed from below.” Quite
so, if the cords were attached directly to the wall of the
ventricle, but yon will remember that they are attached not
to the wall, but to little pillars projecting from the wall,
and as these also are of muscle they contract at the same
time as the wall, and becoming shorter keep the cords tense.
There are not many adaptations more beautiful and more
remarkable than this, so to speak, compensating contraction.
Arteries.—An artery is a vessel, a tube, which carries
¡blood away from the heart. This tube has three coats, a
lining of serous membrane, a fibrous, better termed a
muscular coat, and an outer of a very simple tissue, called
•connective. The middle coat is thick and strong in the
large arteries, hence these are exceedingly elastic. Two
great arteries rise from the heart, the pulmonary (^pulmo, a
lung) from the right ventricle, the aorta from the left. The
pulmonary divides and sends a branch to each lung; these
branches divide again and again within the lung. These
. are the only arteries in the body that contain impure blood.
The aorta sends branches all over the body, to the head,
trunk, and limbs, and these contain pure blood, keeping
-every tissue in working order.
Capillaries.—The arteries, after dividing in this fashion,
open at length into the capillaries (capillus, a hair), minute
vessels varying in diameter from 1/isoo to 1/gooo of an inch.
These capillaries form a fine, close network, the meshes of
which vary very much in size. The network is closest
wherever nourishment is most required and most rapidly
■used, for the actual work of nutrition goes on in the capil
laries. In some parts the space between the capillaries is
. actually less than the diameter of a capillary, so that the
nourishing blood is brought into the very closest contact
with every part of the tissues. When I add that the wall
of a capillary is a very delicate homogenous membrane, you
will see how easily the tissues can, by osmosis, take out of
the blood whatever they require.
Veins.—A vein is a vessel which carries blood towards
the heart. Like the artery, it has three coats, but the
middle one is very thin, and in consequence of this the veins
■ are but slightly elastic. Another great distinction between
arteries and veins is the valves found in most of the latter.
These valves are folds of the lining, shaped much like
watch-pockets, with the opening directed towards the heart
�4
Physiology of the Home.
If, therefore, the blood be flowing towards the heart, the
valves are pressed against the walls of the vein, and offer
no impediment to the circulation. But if the blood begin
to flow back, the pockets at once fill, become distended,
and bar the passage. The use of this is obvious. Blood
has to return to the heart from the lower part of the
body against, the force of gravity, and these valves prevent
it from falling backwards. The veins begin where the
capillaries end, just as the capillaries begin where the
arteries end. The veins nearest the capillaries are very
minute ; they join to make larger ones, join again and
again, until at last all the blood from the lower part of
the body is gathered in the inferior vena cava, and all the
blood from the upper part, except from the lungs, into the
superior vena cava, and these two pour their contents into
the right auricle. All the blood from the lungs is poured
into the left auricle by four pulmonary veins.
Course of Circulation.—We can now trace the course
of the blood. We divide the circulation of the blood into
two systems—the greater, or systemic, and the lesser, or
pulmonary circulation. We will take the greater first.
Blood that has been aerated in the capillaries of the lungs
is poured into the left auricle through the pulmonary
veins. It passes through the auriculo-ventricular opening
into the left ventricle. As the heart contracts, it is forced
to find a way of escape. The mitral valve closes the open
ing into the auricle, but the aorta is open, and it rushes into
that. Through artery after artery it travels, its containing
vessel ever growing smaller and smaller, until it reaches a
capillary network. Through this it travels slowly, very
slowly, yielding up its nutritive material, and at length
passes into a vein. Travelling now towards the heart, it
passes on and on, its containing vessel ever growing larger
and larger, until it reaches either the inferior or the superior
vena cava. It flows into the right auricle, and through the
auriculo-ventricular opening into the right ventricle, and
has concluded the systemic course. There is, however, no
rest for it. The contracting ventricle drives it out, and as
the opening into the auricle is closed by the tricuspid valve,
it is driven through the only other opening into the pulmo
nary artery. It goes either to the right or left lung, through
the capillaries, through the veins, back into the left auricle,
whence we traced its course, thus completing the pulmonarv
circulation. All the blood that has been round the body
�Physiology of the Home.
5
goes to the lungs ; all the blood that has been round the
lungs goes to the body. Why ?
Arterial and Venous Blood.—The question finds its
answer in the difference between the blood returned to the
heart from the body, and that returned to it by the lungs.
The words “ arterial” and “ venous ” are not very accurate,
but they are generally used; they are inaccurate, because
the pulmonary artery contains venous blood, and the
pulmonary vein arterial. The most striking difference
between arterial and venous blood is that of color; the
arterial is scarlet, the venous purple. The most impor
tant difference is the presence of much oxygen in the
arterial, of much carbon dioxide (carbonic acid gas) in the
venous. Oxygen is breathed in by the lungs, and this
oxygen is carried by the blood to the tissues ; it enters into
combination with the carbon of the tissues, and carbon
dioxide (carbonic acid gas) is formed; this is not wanted,
is even harmful, in the body, and it is carried away by the
blood. In the arteries there is scarlet oxygenated blood; in
the capillaries the oxygen is yielded to the tissues, the
carbon dioxide is taken from the tissues; in the veins there
is purple deoxidised blood, charged with CO2, requiring
purification in the lungs.
Cause of the Circulation.—This constant movement
of the blood now needs to be explained. The primary
cause of the movement is the alternate contraction and
expansion of the heart. The heart is a muscle, it is there
fore very contractile. The stimulus to the nerves, causing
them to act on the muscle, is the blood. When the blood
fills the heart, it stimulates nervous action, the nerves act on
the muscular fibres and they contract. The blood expelled,
the stimulus is absent, the muscle relaxes and the heart
expands. And so, alternately, we have contraction and
expansion. Remembering that the blood will always move
in the direction of least resistance, we at once understand
why, on being pressed out of the heart, it rushes into the
pulmonary artery and the aorta. The movement of the
blood, however, does not depend only on the contraction of
the heart; the elasticity of the arteries aids and regulates
the flow. The moment the rush of the blood consequent
on the contraction of the heart has ceased, the aorta in turn
contracts on the blood ; it would flow back to the heart, but
the ever useful valves, this time (semilunar valves) round
the aortic opening interpose, and the contracting artery
�6
Physiology of the Home.
ioYces the blood onwards. This action of the arteries gives
rise to the “pulse.” The pulse is the expansion of the
artery at a particular point, responding to the impulse sent
from.the heart. The blood is thus pushed on through the
arteries, each “ beat” of the heart driving fresh blood into
the aorta, so pressing on the blood already there. In the
capillaries the blood is pushed on from behind, and is also
aided, by several agencies classed under the head of
“ capillary action,” which time does not permit me to deal
with. In the veins it is propelled by the pressure from
behind, and also sucked on, as it were, by the emptying of
the heart in front. Any attempt to flow backwards is, as
we have seen, checked by the valves. It is practically use
ful to. remember the several directions in which the blood
flows in the arteries and veins ; suppose a limb be badly cut
and a suigeon be not at hand. If the cut have severed an
artery the blood will be bright scarlet, and will flow in
regular jets, like water pumped out; if this be the case,
remembering that arterial blood flows away from the heart,
twist a bandage very tightly above the injury, so as to cut
off the supply coming from the heart. If a vein be severed
the blood will be dark and flow steadily, without any
jerking motion ; in this case, remembering that venous blood
flows towards the heart, twist the bandage tightly below
the . wound, so as to cut off the supply coming from the
capillaries.
Blood.—It is time to answer the question; “ What is
blood ?” Gray very well defines it as “ a fluid holding a
number of minute cells or corpuscles in suspension.” The
corpuscles (corpusculum, a little body) are of so'lid matter,
forming about 1/7 of the blood ; there are also other solid
materials in the blood, albumin, fat, salt, and sugar, making
up another. 3/2s, so that
of the blood is solid and 3/4
water. This calculation is very rough, for the composition
of blood is not a constant. If blood be left standing, the
liquid and solid parts will separate out, and we have a
clot surrounded by fluid. In the clot, entangled among
structureless strings, called fibrin, we find the corpuscles,
and these are of two kinds, white and red. The white are
cells, constantly change their shape, and closely resemble
the white corpuscles of chyle; the red are semi-solid bi-con
cave (hollowed on each side) discs, and are two or three
hundred times more numerous than the white. These cor
puscles are the gas-carriers, and the difference of color
�Physiology of the Home.
7
between arterial and venous blood is thought to be due
merely to the difference of the refraction of light severally
from rounder or more flattened corpuscles.
The function of blood is to nourish and to equalise the
temperature of the body. We have seen food transmuted
into chyle, and the chyle poured into the blood system;
when we further learn that the liquid part of the blood
(liquor sanguinis') and the liquid part of the chyle (liquor
chyli) are identical, and that little difference can be found
between the white corpuscles of the blood and those of the
chyle, we have not much difficulty in tracing our foodstuffs
into the capillaries and, by osmosis, into the tissues.
Evolution of Heart.—In studying the wonderful
mechanism of the heart, the marvellous adaptation of the
organ to the function which it is its work to discharge, we
are almost compelled to ask : “ How did all this come into
existence ? ” If the human heart were the only one known
to us, the question would be hard to answer, but we are
fortunately able to trace the evolution of the heart from a
most imperfect beginning to its present condition. Without
dwelling on the mere tube of insects, and passing over the
very simple hearts of the invertebrate animals, let us hastily
glance at the hearts of the great divisions of the vertebrate
(back-boned) kingdom. The lowest class of the Vertebrata
is that of the fish, Pisces. In the lowest again of these, the
Amphioxus, the heart is a simple tube, a “pulsatile cardiac
trunk ” (Huxley), and “ contractile dilatations ” aid in pro
pelling the blood. The typical fish’s heart has two chambers,
one auricle and one ventricle, and may be regarded as
the tube, bent upon itself. In the highest fish, the heart
acquires three chambers, two auricles, and one ventricle,
thus graduating into the normal heart of the second
vertebrate class, the Amphibia, of which the com
mon frog is the best-known representative.
Here the
heart has two auricles, of which the right receives
the venous blood from the body, and the left the arterial
blood from the lungs. Unfortunately the frog has only one
ventricle, and as both auricles open into it, and discharge
their contents into the ventricle at the same time, the blood
it contains is to a great extent mixed. Certain folds and
valves tend to prevent complete mixing throughout, but the
result is scarcely satisfactory. An advance is made in the
next case, the Reptilia, and here we may take the snake as
an example. The snake’s heart has two auricles and one
�8
Physiology of the Home.
ventricle, but there is an incomplete partition separating
the ventricle into two halves, one containing venous and the
other arterial blood, and when the heart contracts, this
partition almost divides the ventricle into two chambers. In
the highest Reptilia, the crocodile has a four-chambered
heart, the septum becoming complete ; this great advantage
is, however, neutralised by the main arterial and venous
trunks crossing just outside the heart and communicating by
an opening, or foramen as it is called, and the blood mixing
through this. In the birds (Aves) and the mammals (Mammalia) the heart has four separate chambers and the arterial
never mixes with the venous blood.
We have thus a steady gradation from the tube of
Amphioxus, through the two-chambered heart of the com
mon fish; the three-chambered of the frog; the three
chambered, but with partially divided ventricle, of the snake;
the four-chambered, but with communication outside, of the
crocodile; up to the four-chambered, with uncommunicating
vessels, of the bird and the mammal. Thus we see gradual
evolution of a more perfect type, each improvement first
hinted at, then introduced, then perfected.
In the development of the individual a similar evolution
takes place. The heart is at one time a mere straight tube,
the veins connected with one end, the arteries with the other.
It soon becomes doubled on itself, and shortly afterwards a
longitudinal septum grows out dividing it into two chambers.
Later, two septa grow out transversely, dividing off the
auricles from the ventricles. Still the separation of arterial
and venous blood is not complete, for there is an opening
between the auricles, the foramen ovale, and there is also a
duct from the right ventricle to the aorta. The foramen
ovale closes at birth, except in cases of disease (morbus
ceruleus), and the duct is completely closed by the tenth
week after birth. Thus the evolution of the race is to some
extent repeated in the evolution of the individual, and the
development of the infant traces for us the development of
humanity.
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�PHYSIOLOGY OF THE HOME.
RESPIRATION.
Respiration is the purification of the gases of the blood..
We have seen that the corpuscles of the blood are gas
carriers ; that they carry to the lungs from the tissues the
carbonic acid gas which has been formed in work and
which needs to be expelled, and also carry from the lungs to
the tissues the oxygen which is required for use in the body..
We have now to investigate the organs of respiration and
the method in which the function is discharged.
Organs of Respiration. These are: the nose; the
mouth; the pharynx; the larynx ; the trachea ; the bronchi;
the bronchial tubes ; the air-sacs and air-cells; the skin.
The bronchial tubes, air-sacs and air-cells may be included
generally under the lungs; the nose, mouth, pharynx, larynx,
trachea and bronchi, may be regarded merely as the air
passages leading to the lungs. Some of you may be sur
prised at my mentioning the skin as an organ of respiration,
but when I remind you that the body of a medium-sized
full-grown man daily gets rid of 400 grains of carbonic acid
gas through the skin, you will see that the skia comes fairly
within the definition of an organ of respiration, that is, of
a special part of the body which purifies the gases of the
blood.
We will consider 1st, the air-passages; 2nd, the lungs;
3rd, the skin.
The air-passages opening on the exterior are two, the nose
and the mouth. Both these passages open internally into
the pharynx. If the mouth be closed, respired air passes
into the two anterior nares, or nostrils, up the nasal fossae
(fossa, a ditch or trench), and through the two posterior nares,
little openings into the pharynx. The air has thus arrived
at the top of the throat, just behind the mouth. If, instead
of breathing through the nose, you breathe through the
mouth, the air passes straight to the pharynx; so that in
�2
Physiology of the Home.
either case it arrives at the back of the mouth. The presence
of these posterior nares, 01* internal nostrils, explains how, if
you are bathing, water may run up your nose into your
throat, or how, in smoking, you may take smoke into the mouth
and breathe it out at the nose. Into the pharynx opens the
larynx, a kind of box, triangular above, rounded below,
which is situated at the top of the trachea, or windpipe.
The larynx is formed of nine cartilages, one of which, the
thyroid, is especially prominent in men, and is known as the
pomum Adami, or Adam’s apple. It is closed above by a
little lid of cartilage, the epiglottis, and contains the vocal
cords, the delicate strings of our voice-machine. When
food passes from the mouth to the oesophagus it goes over
this lid, the larynx being drawn beneath the tongue ; the lid
is then shut down, the hinge, so to speak, of the lid being
just behind the tongue. When food “goes the wrong way,”
it is because this process has been imperfectly performed,
and the morsel has slipped into, or wedged itself against the
larynx, so obstructing the air-passage. Hence the danger of
laughing or speaking when food is passing into the gullet.
“Don’t speak with your mouth full,” is a maxim of physi
ology as well as of politeness. Any action which raises the
epiglottis opens the air-passage, and a passing morsel may
enter and cause suffocation. We have not time to dwell on
the action of the vocal cords, we must content ourselves
with passing by them into the trachea, or windpipe.
The trachea is a tube of about 4^ inches in length, and is
formed of membrane with cartilaginous rings running twothirds of the way round. These rings are imperfect behind,
where the trachea comes into contact with the oesophagus,
along the froDt of which it lies. 1 he trachea divides into
the two bronchi, the right bronchus, about an inch long,
going to the right lung, and the left, about two inches in
length, going to the left. When the bronchus enters the
lung it divides and subdivides, forming the bronchial tubes.
The lungs are paitly made up of the numberless ramifica
tions of these bronchial tubes, but before dealing with these
it will be well to pau^e for a moment on the thorax, the
cavity which contains the lungs. This cavity is a perfectly
air-tight box, bounded by the backbone behind, the breast
bone in front, and the ribs on either side, the interstices of
the ribs being filled with the powerful intercostal muscles.
�Physiology of the Home.
3'
The bottom of the box is formed by the diaphragm, a
remarkable muscle, shaped something like a fan, attached
in front to the lower end of the breastbone, at the sides to
the ribs, at the back to the vertebral column, and arching
over the abdomen. The diaphragm is pierced by the oeso
phagus and the great blood vessels, but adheres closely round
them, permitting no air to enter. The thorax contains,
besides the lungs, the heart which lies between them and all
the great vessels and nerves connected with heart and lungs,
as well as the greater portion of the oe'Ophagus. The liver
and stomach lie immediately below it, being separated from
the thorax by the diaphragm. The position of the diaphragm
varies according to circumstances. When the lungs are
partially emptied the diaphragm is much arched, the concave
side being toward the abdomen. When air is breathed in
the diaphragm is partially flattened, enlarging the cavity of
the thorax. After a full meal, the diaphragm is pushed
upwards by the extension of the stomach, and the oppres
sion in breathing felt after an excessive meal is due
partly to the upward pressure of the diaphragm against
the lungs.
Before quitting the question of the thorax, a few moments
must be devoted to the cause of our regular breathing.
You will have noticed that I have laid stress on the fact
that the thorax is perfectly air-tight. If it were not so
breathing would be impossible. When air is expired from
the lungs it is driven out partly by the elasticity of the lungs
themselves, the bronchial tubes contracting upon it and
expelling it. The outward motion is also perhaps assisted by
delicate cilia—hair-like processes from the lining of the tubes—•
which constantly sweep outwards the solid and liquid contents.
The muscles of thechest also come largely into play in expelling
the air, by lessening the cavity of the thorax. Their several
movements are too complex to be described in a lepture like
this. The diaphragm,lastly, does a share of the work; like all
muscles it contracts, and when it contracts it becomes flatter
and therefore descends, and as the ribs are rising while the
diaphragm is descending, the thoracic cavity enlarges, and
air rushes in to fill the space thus given. The whole of the
muscular action is, as before, controlled by nerves, and is
reflex, not voluntary. We can partly control it by our will,
and we can voluntarily hasten or slacken the movements ; but
�4
Physiology of the Home.
in the normal healthy condition, respiration goes on without
our notice. As the normal number of respirations in a
minute is fifteen, it would clearly be excessively troublesome
if the brain had to see that the work went on properly; the
task falls conveniently to the nonsensating division of our
nervous system.
One difference may be worthy noting, the difference
between male and female breathing. In the male the
diaphragm is very much used ; in the female it plays a com
paratively small part, while the muscles connected with the
ribs are the chief agents. Notice the breathing of a man and
a woman, and see how much more the bosom of the latter
rises and falls ; the upper ribs are coming largely into play,
while in the man they do but little work. A moment’s
thought, and the remembrance of the way in which Nature
adapts beings to their life-conditions, will suggest to you
the “ why ” of this difference. Woman is the reproducer of
the race ; during many months of her life, before she gives
birth to a child, violent movement of the diaphragm would
result in injury, and the condition necessary for health in
one part of life becomes a sexual characteristic, common to
the whole.
Let us return now to the anatomy of the lung, the sur
roundings of which we have been considering. Each lung
is covered by a double membrane, one fold of the membrane
clothing the lung, the other fold lining the cavity of the
thorax, in which the lungs and heart are enclosed. Between
these two folds is a small quantity of fluid, which enables
them to run smoothly over each other. Inflammation of
the pleuiae, or of these coats of the lungs, is the painful and
dangerous disease known as pleurisy. The lung is composed
of a large number of lobules, or little lobes. Each lobule
consists of a little branch of the bronchial tube—which
subdivides, each subdivision ending in a minute expansion or
atr-suc—and the nerves, blood-vessels and lymphatics in close
relation to it, all being held together by connective tissue.
A number of these lobules make up a lobe, and of these
lobes the right lung has three, the left two. Reverting for a
moment to the air-sacs mentioned above, it is necessary to add
that in the walls of the air-sacs are little alveoli, depressions,
very badly called air-cells. These range from x/7o to 1/2oo of an
inch in diameter, and over the walls of each of these cells
�Physiology of the Home.
5
spreads a net work of capillaries, into which pours the dark
■carbonic-acid-burdened blood from the subdivisions of the
pulmonary artery, and out of which flows the scarlet
oxygen-laden blood to the pulmonary veins. So close is the
capillary net work that the space between the. capillaries is
only from 1/soo to 1/i25 of an inch. By osmosis, once more,
the carbonic acid gas passes out and the oxygen passes in.
The oxygen is brought down to the air-cells as part of .the
air through all the passages that we have been considering.
Air is a mixture chiefly of oxygen and nitrogen, the
nitrogen serving mei'ely to dilute its too vigorous companion;
the oxygen in the air breathed into the lungs is seized upon
by the corpuscles, and they give up in exchange the dele
terious carbonic acid gas, which passes up the air-passages
and out of the mouth or nose.
The exchange of oxygen for carbonic acid gas is not the
■only difference in inbreathed and outbreathed air. Expired
air is of a higher temperature than inspired, and it is also
charged with a considerable amount of water in the con
dition of steam. It is estimated that the lungs of an
ordinary adult send out daily about 5,000 grains (9 ozs.) of
steam, and 12,000 grains of carbonic acid gas, but it must
he remembered that the amount of steam and of carbonic
acid gas thus exhaled depends not only on the age, but also on
the work of the individual.
Before speaking of the effect of this action on the air,
we must complete our brief study of the organs of respira
tion by considering the skin. The skin is composed of two
distinct layers, differing in nature, the scarf-skin, cuticle, or
epidermis above, and the true skin or derma lying below.
In the true skin, or sometimes just below it, are a number
of small bodies called sweat-glands, and from , these run
ducts, which open by a tiny valve on the exterior of the
body. By these is discharged the watery matter, known as
perspiration, and if a limb be tied in an indiarubber bag it
is found that the air within the bag becomes charged, not
only with aqueous matter but also with carbonic acid gas.
Since 400 grains of carbonic acid and 10,000 grains of. water
are thus discharged daily by the skin, the enormous impor
tance of the healthy action of the skin at once becomes
apparent. Let dust fall on the skin and mixing with the
perspiration clog the openings of the valves, and the dis
�6
Physiology of the Home.
charge is at once checked; the matter that ought to be got
rid of is kept in the body; the other excretory organs try to
get lid of it, the lungs chiefly woi'king at the carbonic acid'
gas and the kidneys at the water; over much labor is
thereby thrown upon these organs, and they suffer. How is
all this mischief to be prevented ? The answer comes in
one word : cleanliness. The body needs to be thoroughly
washed, and where people work hard in dusty atmospheres
the necessity is the more stringent. The public baths now
found in London are veritable hygienic institutions, and
men, women, and children who visit them will find doctors5'
visits less frequent.
Ventilation.—We have seen that every person is con
tinually breathing oxygen into the body, and is continually
breathing out carbon dioxide, or carbonic acid gas. Hence
it results that if a person be shut up in a room to which
oxygen has no admittance, he will gradually use up the
oxygen therein contained, and gradually replace it with
carbon dioxide. As soon as the carbon dioxide amounts to
1 in 1,000 parts, the air of the room will begin to have an
oppressive odor. The man will get drowsy and disinclined to
exertion ; a little later he will sink down half-sleeping, half
fainting ; if he be left unrescued, he will die, and he will'
die not of any active poison administered to him, but from
privation of the oxygen necessary for the maintenance of
life. Carbon dioxide is sometimes called a narcotic poison,
but it is not the presence of carbon dioxide that kills; it is
the absence of free oxygen. When in crowded rooms
people faint, they faint from want of oxygen ; the venous
blood carried to the lungs is not oxygenated there;
it^ goes back to the left side of the heart still charged
with carbon dioxide. In this condition it is supplied
to the tissues.
The brain receives this, instead of'
the fresh bright blood which it is in need of; giddiness,
drowsiness, faintness, are the immediate consequences, and,
if the mischief be allowed to continue, these result in death.
A modified form of this injury is caused whenever a room is
“ close,” although actual faintness may not ensue. People
are so afraid of “draughts” that they prefer the “close
ness,” not knowing that the latter is really more dangerous
than the former. But there is no need to suffer either from
draughts or from closeness. Cut a slip of wood, about an
�Physiology of the Home.
7
inch thick, to fit along the bottom sash of a window; shut
the window down upon this. It will seem quite closed ; but
if you look at the middle of the window, where the bolt
comes, you will see a slit as wide as your piece of wood.
Fresh oxygen from outside will rise through this, and,
spreading upwards, will cause no draught. If, in addition,
you leave your window half an inch open at the top, you
will feel no uncomfortable stream of cold air, but your
room will be healthily ventilated, and your brain will be the
^clearer for it. One other agent we may call to our help in
ventilating our rooms. Flowers are not only beautiful, they
are also health-giving. They feed on the carbon dioxide,
so long as light falls upon them, and, retaining the carbon,
they excrete the oxygen. Although they breathe just as
we do, taking up oxygen and breathing out carbon dioxide,
yet, as long as they are in the light, they feed so much more
than they breathe that their total effect upon the air is to
diminish the carbon dioxide in it, and to increase the free
oxygen. Flowers are, therefore, really useful in the room,
and while they bring light and grace, color and sweetness
into our homes, they also come as messengers of health,
working for us as purifiers of the air.
Much unnecessary lung disease is caused by mere care
lessness. Remembering the delicate machinery of capillary
network and minute air-cell that I have traced for you, you
will readily understand that rapid changes of temperature,
or the introduction of foreign materials would very easily
disorganise the mechanism. Yet people go suddenly out of
a hot, close room into keen, cold air, unthinkingly subjecting
these exquisite machines to the mischievously sudden altera
tion of temperature. A handkerchief placed over the mouth
for a few moments after passing into the outer air from a
hot room would prevent many a “ bad cold on the chest.”
Various trades are characterised by special lung diseases.
If you pay a visit to a surgical museum, you may see lungs
preserved there of miners, cotton-spinners, etc. The miner
Suffers from coal-dust breathed into the lungs in the air; the
cotton-spinner from cotton-fluff carried thereinto in similar
fashion; the Sheffield grinder from steel-dust. These dangers
might be lessened in the last two cases by the continual swing
ing of large fans in the work-rooms, driving away the dust;
they might be completely avoided by the wearing of respi
�8
Physiology of the Home.
rators by the workers, as all dust would be stopped in these,,
instead of going on into the lungs.
Again, as to clothing. The apex of each lung rises about
an inch or an inch and a half above the line of this first rib.
The lower part of the neck, therefore, needs to be protected
even more than the chest itself. Yet mothers let babies
and little children play about in the open air in winter in
low-necked frocks, and then wonder that they suffer from
cough, bronchitis, and inflammation of the lungs.
This brief course of lectures has now come to an end. I
shall have wholly failed in my object, if it has only served
to amuse some idle hours. I trust rather that our talks may
have raised the desire to know more of a most interesting
subject, and will lead many to study fully that which has
been so superficially treated here.
PRICE ONE PENNY.
■I
London: Printed by Annie Besant and Charles Bradlaugh,
28, Stonecutter Street, E.C.
�
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Victorian Blogging
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Title
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Physiology of the home
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Besant, Annie Wood [1847-1933]
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An account of the resource
Place of publication: [London]
Collation: 8,8,8, 8 p. ; 19 cm.
Notes: Contents: Digestion -- Organs of digestion -- Circulation -- Respiration. Thursday lectures delivered at the Hall of Science. Printed by Annie Besant and Charles Bradlaugh. Author statement from OCLC WorldCat. Part of the NSS pamphlet collection.
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[Freethought Publishing Company]
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[1882]
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N538
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Biology
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<a href="http://creativecommons.org/publicdomain/mark/1.0/"><img src="http://i.creativecommons.org/p/mark/1.0/88x31.png" alt="Public Domain Mark" /></a> <br />This work (Physiology of the home), identified by <a href="https://conwayhallcollections.omeka.net/items/show/www.conwayhall.org.uk">Humanist Library and Archives</a>, is free of known copyright restrictions.
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Text
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English
Human Physiology
NSS