HYGIENE
HYGIENE FOR
TEACHERS
BY
R. ALUN ROWLANDS, B.Sc., M.R.C.S., L.R.C.P.
DEMONSTRATOR OF PHYSIOLOGY, AND ASSISTANT TO THE LECTURER
ON CARDIAC RESEARCH, AT THE LONDON HOSPITAL
MEDICAL COLLEGE
WITH PREFATORY NOTE
LEONARD HILL, M.B., F.R.S.
PROFESSOR OF PHYSIOLOGY, UNIVERSITY OF LONDON
THIRD IMPRESSION
LONDON
EDWARD ARNOLD
[All rights reserved}
*" * V,'1
*S8-
PREFATORY NOTE
BY LEONARD HILL, M.B., F.R.S.
FOR scores and probably hundreds of thousands of years
man has lived uncivilized as a wild animal, exposed to
all the rigours of climate, and slowly evolved, structurally
and functionally, to win as an individual in the struggle for
existence and perpetuate his stock. In later times there
has come about a vast revolution in his condition, brought
about, first, by the acquirement of a dominion over fire
and fashioning of implements ; then by perfection of
speech, writing, the printing-press, and the accumulation,
sifting, and handing down of knowledge ; and, finally, with
enormously increased velocity by scientific invention of our
age.
Geological evidence shows us that man, who lived twenty
or thirty thousand years ago, had no less well-proportioned
a body and no smaller a brain than ours. His cave draw-
ings of animals in motion, his carvings and his stone
implements, show that he was as cunning of hand as the
best artist or artificer of modern days. If we could re-
instil the spirit of life into some child of his, found, as the
mammoth has been, perfectly preserved in ice, this child
clothed and educated as one of us, would take an ordinary
part in our world. But what a different world to his !
y
551) (30
vi PREFATORY NOTE
In place of the free range of forest, hill, seashore, and
plain, confinement to an office desk or factory bench. In
place of wind, rain, and sun beating upon his skin, and
stimulating him to activity or repose, the uniformity of a
windless atmosphere, often artificially lit, and the monotony
of a sedentary occupation. In the place of fruit or flesh
obtained by the hardest muscular effort, and eaten with
the appetite bred of such exercise in the open air, and a spare
diet, tinned food, white bread robbed of some of the vital
principles of the fresh, whole foods of nature, and eaten
with an appetite Jaded by the long hours of monotonous
sedentary occupation in confined places.
The wild man, like the wild animal, gained the perfection
of bodily function and well-being at the expense of a
maximum insecurity of life. Industrial man has sunk his
individuality, lost the perfection of bodily function, and
gained the security of a longer and tamer existence.
It is imperative that man should know how to regulate
his life in industrial communities, so that his bodily func-
tions may receive that exercise which is demanded by the
history of man's evolution.
The happiness of the masses can only be obtained by the
recognition of the working of the human body, by plu< -in^
the foundations of physiological science on a sure footing.
Some are unhappy because they do not know how to keep
their bodies and minds in health ; others because the in-
dustrial conditions do not permit them to live in accordance
with those functional needs of the body which have been
established by ages of evolution.
The spirit of man is not set above his body, so that he
PREFATORY NOTE vii
can afford to neglect the latter, and, allowing the disorder
of bodily functions, yet triumph over all.
Such disorder inevitably leads to unhappiness and
lessens efficiency. To mortify the flesh means to restrain
the appetite and keep the body in perfect health by spir?
and clean living.
A man may be inherently weak or defective in some part
and yet triumph over these defects, but it is by the dis-
cipline and through the perfect working of the vital organs.
The spirit cannot overcome the defect of such organs — e.g.,
defect of brain substance or of some organ essential to
metabolism. Thus the idiot results from either the failure
of the brain development or that of the thyroid gland.
From birth to the setting of the seal on a man's life,
sensations, conscious or unconscious, stream into his
nervous system from the world without and from the body
within. The external sensations, such as the visual,
enable man to project his spirit to the stars, and lead him
to the contemplation of the universe.
His character, habits, and happiness, are moulded by his
education, the ceaseless beating of myriads of impulses on the
living substance of the brain. His consciousness should be
filled with the changing play of external sensations, and
the attention in perfect health should not be attracted to
internal sensations arising from the body.
Modern conditions confine him to the murky atmosphere
of a big city, to mean streets and houses — burrows which,
in comparison with the immensity of nature, are no
nobler and far less clean than the alleys of an ant-hill.
Teaching, reading, and example may elevate the spirit
viii PREFATORY NOTE
above the conditions of modern life, but full happiness can
only be secured by the recognition of the daily need of
the body for open air, exercise, and exposure to wind and
sunlight. These repel sensations of bodily discomfort and
stimulate the metabolism, make us breathe deep, flood
the lungs with air and blood, give us appetites, impel the
blood to circulate faster in its course, and refresh the brain.
Open-air exercise and right feeding enable us to maintain
our immunity, to resist the invasion of bacterial disease,
and prevent errors of metabolism which result in degenera-
tion of our tissues.
Man knows how to keep a horse in a perfect state of
physical fitness, and in institutions children are no less
well -disciplined to healthy happy lives. It is by discipline
that sailors, soldiers, and policemen are kept in a state of
physical fitness. The whole nation requires a disciplined
life to secure any general measure of happiness.
The study of hygiene gives us the clue to the required
happiness, but before we can understand hygiene we must
know something of the structure and function of the body.
Our national life and progress depends on the diffusion
of this knowledge, and the noblest function of the teacher
is to acquire and instil that which will impel the younger
generation to a better life.
LEONARD HILL.
OSBORNE HOUSE,
LOUGHTON.
August 20, 1912.
AUTHOR'S PREFACE
THE State has long realized that the power of the nation
depends upon the physical and moral strength of the in-
dividuals composing it. Within the last few years the
efficiency of the Public Health services has been increased.
Medical inspection of schools and school -children has
become one of the duties of the State, and all educational
authorities have realized the importance of teaching
physiology and hygiene in the schools and colleges.
This volume has been written mainly for the use of
teachers in the training colleges, and when the student
has mastered it, he should have no difficulty in answering
any reasonable question on the work required by the Board
of Education in the syllabus on hygiene and physical
training ; and a much more important attainment will be
a good knowledge of hygiene and of the physiological
principles upon which it is based.
My best thanks are due to Professor Leonard Hill, F.R.S.,
for guidance and help in the preparation of the manu-
script and for the use of illustrations ; to Dr. Drummond
of Edinburgh and Mr. G. P. Mudge, Lecturer on Zoology
at the London Hospital Medical College, for the use of
some illustrations in their possession ; to Mr. J. Watson
Jerdan, who has drawn the illustrations on school con-
x PREFACE
struction, planning, and drainage ; and to Mr. W. Morris, of
the London Hospital Medical College, who has drawn a large
number of the illustrations. The correction of the proofs
has been done by my friend and colleague, Dr. Martin
Flack, to whom many thanks are due.
B. ALUN ROWLANDS.
LONDON HOSPITAL MEDICAL COLLEGE.
September, 1912.
CONTENTS
CHAPTER PAOE
PREFATORY NOTE BY LEONARD HILL, M.B., F.R.S. - - V
AUTHOR'S PREFACE - - - - ix
I. INTRODUCTORY - - - - . - 1
H. THE SKELETON AND MUSCULAR SYSTEM - - 14
HI. THE DIGESTIVE SYSTEM - - - 61
IV. THE CIRCULATORY AND RESPIRATORY SYSTEMS - 112
V. THE EXCRETORY SYSTEM - - - 173
VI. THE NERVOUS SYSTEM - 190
VII. RELATION OF SENSES TO THE NERVOUS SYSTEM : THE SENSE
OF SIGHT - 221
VIII. RELATION OF SENSES TO THE NERVOUS SYSTEM (continued) :
SENSES OF HEARING, ETC. - - - 237
IX. SANITATION OF THE SCHOOL - - - 253
x. SANITATION OF THE SCHOOL (continued) - - 275
XL DISABILITIES AND DISEASES OF CHILDREN - 300
XII. MEDICAL INSPECTION OF SCHOOLS - - - 329
INDEX ..... - 349
HYGIENE
CHAPTER I
INTRODUCTORY
Structure of an Animal Cell. — There are two methods of
examining the structure of plants and animals. The first one
is to dissect the organism and study its structure by the
naked eye ; this is called macroscopic anatomy. Secondly, its
minute structure may be studied by magnifying it by means
of a combination of lenses called a "microscope." This
second mode of structural study is called microscopic
anatomy, or histology. We can carry out a microscopic
examination of any object which is sufficiently transparent
to allow light reflected from the mirror of the microscope to
pass through ; thick objects therefore must be cut into very
thin sections. To effect this, the living tissues are first
killed and hardened by various reagents, such as alcohol.
Any form of tissue that is examined in this way is found
to be composed of an aggregation of a number of small
units. These to the earlier observers, who were not aided
by modern methods of staining, appeared like empty spaces
separated by fine strands of tissue ; hence animal and
vegetable tissues were said to be "cellular."
Though the term animal and vegetable " cell " is
still retained, it conveys a different idea to the modern
histologist to what it did to his predecessors ; it is not an
empty space enclosed by a cell wall, but is a structure of
complex composition.
An animal cell may be defined as a unit mass of animal
matter. Most of the simplest animals — e.g., protozoa —
1
HYGIENE
are single cells — egg cells and spermatozoa are single
cells ; but as the organism ascends in the zoological
tree, the number of cells composing it are increased,
and concurrently with this there is differentiation of
structure in the cells by which they are accommodated
to differences in function, and the cells which have
the same function are aggregated to form tissues and
organs.
When an animal cell is examined by the best histological
methods, it is found to be made up of cell substance, or
cytoplasm, which consists partly of the genuinely living
substance, or protoplasm,
and partly of complex
materials not really living.
This cytoplasm appears
at first sight almost homo-
geneous, but higher magni-
fication shows great com-
plexity of structure. It is
not amorphous, like raw
white of egg, but shows
a reticular, fibrillar, or
vacuolar structure. There
are often present obscur-
ing granules of various
kinds. It is a question
how far the reticular or granular structures are produced
by the action of the hardening reagents on the living
cytoplasm, for these reagents produce reticular, fibrillar, or
granular precipitate when added to white of egg.
Situated inside the cytoplasm of all living cells there is
a small vesicle called the nucleus ; it may be spherical,
ovoid, elongated, annular, or irregular, in shape. The
nucleus is bounded by a membrane which encloses a clear
substance (nucleoplasm), and the whole of this substance
is generally pervaded by an irregular network of fibres
called the " nuclear reticulum." This reticulum under-
Fio. 1. — DIAGRAM SHOWING THE
STRUCTURE OF AN ANIMAL CELL.
A, Cell- wall ; B, protoplasm (cyto-
plasm) ; N, nucleus ; N', nucleolus.
INTRODUCTORY 3
goes a most remarkable series of changes when a cell
divides into two cells.
Place of Man in the Animal Kingdom. — Man is the
highest of all forms of animals, and in order to show his
relation to the other forms of animal life it is necessary to
give a general survey of the animal kingdom, its classifi-
cation, and the factors on which it is based.
We naturally group together in the mind all things which
are like one another, and here lies the beginning of all
forms of classification. " The character of classifications
will vary according to their purpose, or according to the
points of similarity which have been selected as their bases.
For instance, animals may be classified according to their
diet or habitat, without taking any thought of their
structure. A strictly zoological classification must be
based on a real resemblance of structure, for it seeks to
show the natural relationship of animals, to group together
those which resemble one another in structure and
nature."
Animals may be divided into two great groups — the
Invertebrates, or backboneless animals, and the Verte-
brates, or backboned animals. This distinction between
the backboned and backboneless animals was to some
extent recognized by Aristotle over two thousand years
ago, and was probably more or less obvious to any
who accurately studied various forms of animal life. It
was not until 1797 that Lamarck definitely drew this line
of separation.
The Invertebrates are the lower group of animals, and
forming it there are a large number of diverse forms of
animal life. The lowest members are made up of a single
cell, and are called the " protozoa." Other members of
this group are the sponges, Jellyfishes, sea - anemones,
corals, segmented and unsegmented worms, starfishes,
insects, spiders, mussels, cockles, oysters, etc. The verte-
brates include the fishes, amphibians, reptiles, birds, and
mammalia.
4 HYGIENE
The Mammalia include many different types of animals,
such as men and monkeys, horses, cattle, cats, dogs, lions,
tigers, mice, hedgehogs, bears, and so on ; but the common
possession of certain characters unite them all in one
class, readily distinguishable from all other forms of
animals. These distinctive characters are " the milk-giving
of the mother mammals, the growth of hair on the skin,
the general presence of convolutions on the front part of
the brain, and the occurrence of the muscular partition, or
diaphragm, between the chest and abdomen."
Most mammals are suited for life on land, but some
members of this group, such as seals, whales, and sea-cows,
have taken to the water, while bats are structurally adapted
for aerial life.
In the majority of mammals there is a close connection
between the mother and the young during the early period
of its development ; on the other hand, birds and reptiles
lfty egg8, and the young are developed from these when
they have no organic connection between them and the
mother.
The lowest group of mammalia, called the Monotremes,
resemble birds and reptiles in bringing forth their young
as eggs ; but after the eggs are hatched the young are
suckled by the mother. The duckmole and porcupine
ant-eaters are examples of this group, and they form an
interesting link between the birds and reptiles on the one
hand, and the higher mammalia on the other.
In the next group of mammalia the connection between
mother and offspring has become closer. The embryo is
born- alive, but prematurely and after a short gestation.
In most cases after birth the young are placed in an
external pouch, within which they are sheltered and
nourished.
In the highest forms of mammalia, or Eutherians, there
is a close connection between the unborn embryo and the
mother. The young obtains its food and oxygen from the
blood of the mother, and this it does by means of a vascular
INTRODUCTORY 5
sponge, which is partly maternal and partly embryonic in
origin.
The various forms of human subjects are classified by
the zoologist under the title of Hominidse, which is the
highest group of mammalia. " The great distinction be-
tween man and the anthropoid apes is his power of building
up ideas and of guiding his conduct by ideals." But there
are some structural peculiarities which are of great interest,
such as more uniform teeth, forming an uninterrupted
horseshoe-shaped series without conspicuous canine teeth,
bigger forehead, smaller cheek-bones, a less protrusive face,
and a true chin.
The brain of man is two or three times as heavy as that
of an ape.
Darwin and others have sought to show that man has
arisen from a stock common to him and the anthropoid
apes. They have based their theory upon physiological,
anatomical, and historical grounds.
The physiology of man -is very similar to that of the
anthropoid apes, and they are both subject to the same
diseases.
Structurally man is very similar to the apes ; the only
great difference is the much heavier human brain.
The remains of primitive men are few, but most probably
man could not have arisen from any of the known anthro-
poid apes, but he may have arisen from a stock common to
them and to him.
Division of Labour. — It has been said above that the
simplest animal is made up of a single cell, which has the
ordinary structure of an animal cell. It is bounded by a
cell wall, which encloses the protoplasm, situated in which
there is a single nucleus. That single unit is able to per-
form all the functions that pertain to life. It will take in
food, digest and absorb it, and will eliminate waste matter.
It is also able to respond to stimuli, and has slight power
of locomotion.
The higher animals are made up of a large number of
6 HYGIENE
cells ; and if each unit remained in the primitive conditions
similar to the unicellular animal, the whole organism would
be a soft protoplasmic mass, and all its functions would be
performed sluggishly. It is a well known fact that in the
animal and vegetabb kingdom there is a very great struggle
Fia. 2. — DIAGRAM ILLUSTRATING A FEW DIFFERENT FORMS OF CELLS
FOUND IN THE HUMAN BODY.
a, Cell from lining of the mouth ; 6, ciliated cell from lining membrane
of the trachea or windpipe ; c, cell found in connective tissue ;
d, nerve cell ; e, fat cell ; /, involuntary muscular celL
for existence. In order to survive, an animal must be able
to compete successfully with its fellow-creatures, and this
is only possible by its having a ready means of absorption
of food and elimination of waste products, power of quick
response to change in its environment, rapid means of
INTRODUCTORY 7
locomotion, physical force for protection, and a good
nervous system to control rightly all the other functions
of the body. The only means of attaining this end is to
set apart certain cells for certain physiological purposes.
Thus, some of the cells of the body are set apart for the
purpose of digesting food ; in some of the lower animals
these simply form a layer of cells lining the body cavity,
but in the higher animals they form the alimentary
system, composed of gullet, stomach, liver, intestines, etc.
In the lower animals — e.g., protozoa — all the cell absorbs
oxygen from the air, and eliminates carbon dioxide ; in
the higher animals certain units are set apart for this
function, and constitute the respiratory systems.
The protozoa reproduce by simply dividing into two,
while in the higher animals certain cells are set apart for
this function, constituting the ovaries in the female and
the testes in the male.
In order to be able to respond more efficiently to external
stimuli, certain cells are set apart which become sense
organs, and these are so specialized that they can only
respond to one form of stimulus ; thus, the eye can only
respond to light stimuli, and the ear to sound, etc. The
power of locomotion in a protozoan is very limited, and
is effected by protruding its protoplasm in processes ; in
the higher animals certain cells are set apart which develop
great power of contractility, and become muscular tissue,
and by this means they attain a more efficient means of
locomotion.
Other examples may be enumerated how, as we ascend
the animal tree, there is greater and greater specialization
of function, and to attain this there must be adaptation in
structure.
This setting aside of different functions to different
organs and tissues, and a corresponding adaptation in
structure, is called by the biologist division of labour.
Structure and Function. — It is readily seen that in the
animal and vegetable kingdom there is structural adapta-
8 HYGIENE
tion in any portion of the organism to the kind of work
which the organism requires of it. Thus, in the nerve
layer of the eye there is a peculiar structure which is a very
specialized means to respond to light stimuli. In the ear
there are cells of peculiar structure, which are able to
respond to sound stimuli, and convert these into impulses,
which are carried along the auditory nerve to the brain.
Muscular tissue is made up of cells which have great
power of contractility, and these cells have a very peculiar
structure.
Bone serves the purpose of supporting and protecting
the remaining more delicate tissues of the body ; conse-
quently it is strong and rigid by its being made up of
strong fibrous tissue with large deposits of lime salts.
The structure of the mouth is adapted for taking in,
masticating, and mixing, the food with the saliva.
The stomach is adapted for the reception of food and
its digestion by the gastric juice.
A large number of other instances of adaptation to
function may be mentioned ; in fact, all the different parts
of the body are structurally highly specialized for adap-
tation to the physiological functions which they perform.
Work and Rest. — Throughout life we find a large amount
of work being done in the world around us, and it is com-
paratively few persons who realize what are the various
factors concerned in this process called " work."
Let us take an example from the steam-engine. There
coal is burnt, a large amount of heat is given off, and is
mostly utilized to heat water and convert it to steam, which
is kept at a high pressure. This high-pressure steam acts
on the piston-rod, which causes movement of the axle of
the wheels. The engine is thus able to move along and
pull heavy weights behind it.
After a long journey large amounts of coal will have
been burnt, and converted into carbon dioxide, water, and
ashes.
Coal is made of vegetable material which has been
INTRODUCTORY 9
subjected to very great pressure for a very long period of
time. It is therefore a complex compound of the element
carbon combined with hydrogen, oxygen, and inorganic
material. The various elements which make up the coal
are held together by what the chemist calls " chemical
energy."
To the scientist the term " energy " means capacity for
doing work. Energy takes various forms ; heat, light,
sound, mechanical movement, and electricity, are all
forms of energy.
It is not within the power of man to destroy energy, but
he can convert it from one form to another, and during
this conversion he is able to use the energy to do what work
he requires to be done. After it has been expended in
doing work it is converted into a form of heat, which can
no longer be utilized to do work.
In the steam-engine the capacity for doing work is stored
up at first in the coal, as chemical energy. When this is
burnt, the chemical energy is liberated as heat, which is
used to heat the water in the boiler. The water is con-
verted into steam, and on further heating the steam ex-
pands, like all bodies under the influence of heat. If
the steam is prevented from expanding, it will exert great
pressure on the structure which prevents its expansion.
This pressure is utilized to move the piston, which in its
turn causes movement of the wheels, and thus the engine
moves along the rail and pulls the load behind it. The
chemical energy of the coal has been converted by means of
the engine into mechanical energy.
The human body may be looked upon as a kind of com-
plicated engine, capable of converting chemical energy
into various other forms of energy. Chemical energy is
supplied to the body in the foodstuffs ; these are very
complicated organic compounds, and contain a large
amount of chemical energy. The foodstuffs are oxidized
or burnt (because burning is really a chemical reaction
between the substance that is burnt and the oxygen of the
10 HYGIENE
air) into simpler substances, and the greater part of the
chemical energy is liberated. This energy is used for
various purposes — production of heat, mechanical move-
ment, and all other activities of the body.
In the case of the steam-engine the best possible amount
of work can only be obtained by having the best coal and
the engine in the best condition.
Similarly for the human subject, work can only be done
at its best when the body is in the best of health and has
the best foodstuffs supplied to it.
It is very obvious that in our schools, in order to obtain
the greatest amount of mental work, the health of the
children must be in good condition, and they must be
supplied with proper nourishment.
It is useless, therefore, for the teacher to try and instil
knowledge into children that are physically unfit and are
not supplied with proper nutrition. All forms of work
involve a certain amount of wear and tear in the mechanism
which acts as the converter of energy. The steam-engine
has occasionally to be sent to the workshop for repairs.
Similarly in the human body, all its activities involve a
certain amount of wear and tear of the tissues, and these
are repaired during periods of rest.
It is seen, therefore, how important rest is for continual
good work. If it is insufficient, the repair does not keep
pace with the wear and tear ; this will result in derangement
of the tissues of the body, the amount and character of the
work will be of a lower standard, and the resistance of the
body to disease will be diminished.
Adequate rest for school-children is far more important
than for adults, because they have to grow as well as
work.
Development of the Child. — The young in mammalia
during the first stage of its growth lies within the mother,
and obtains its nourishment from her. The organic con-
nection between mother and child is broken at birth, and
even then the young is in rather a helpless condition, and
INTRODUCTORY 11
only able to develop to maturity through the care of the
mother.
The time that elapses between birth and maturity varies
for different animals, and is longest in the case of the human
subject, because it is the highest of all forms of living
beings, and therefore requires greater time and care to
develop. The success of the mammalia is attributed to the
maternal sacrifice involved in the placental union between
the mother and offspring, in the prolonged gestation, in
the nourishment of the young on milk, and in the frequently
brave defence of the young against attack.
The mother naturally provides the best form of food-
stuff for its young, and it should be emphasized that the
proper nourishment for the child is its mother's milk. If
a mother, because of poverty, illness, or her own selfish
interest, is unable to suckle her child, her offspring is likely
to suffer, because artificial feeding can never be looked upon
as a proper substitute for the mother's milk.
All the tissues and organs of the child at birth are
anatomically and functionally undeveloped, and when we
compare the anatomy and physiology of the child at birth
with that of the adult, we find there is a great difference.
In the child the skeleton is small, soft, and weak ; the
muscular system is undeveloped and incapable of co-
ordinate contraction, so that walking and other complex
co-ordinate movements are impossible ; the alimentary
canal is only able to digest and absorb its natural form of
foodstuff — namely, milk ; the nervous system is un-
developed and incapable of generating impulses in proper
sequence, and it cannot understand or appreciate the
various stimuli that reach it by afferent paths. The
respiratory and circulatory systems are undeveloped, and
only able to supply the needs of the body at this stage of
its growth.
The heat regulatory mechanism is very inefficient, and
a child will therefore easily become too warm or too cold,
unless very great care is taken to have it properly clothed.
12 HYGIENE
Maturity is attained only by a very slow process of
growth; and in a growing child not only has life to be
maintained, but provision must be made for the develop-
ment of the mind and body. A great characteristic of life
is its power to respond to stimuli from its surroundings,
and biologists tell us that environment has a great influence
upon the development of all forms of life. This is even of
greater importance in the case of the human race, because
that part of the body — namely, the nervous system — that
is specialized for the reception of outside stimuli is more
highly developed.
The physical and moral surroundings of the child must
be such as to aim at its highest mental, moral, and physical
development.
The child should be allowed an ample supply of fresh
air ; it should not be kept in closed heated rooms, but should
spend the greater part of its life in the open air.
Unsanitary conditions have a deteriorating effect upon
persons of all ages, and is certainly most marked in the
case of children, who should therefore be placed in the
best possible hygienic conditions.
It is obvious that proper food is of the greatest im-
portance to children ; otherwise their growth and develop-
ment are sure to suffer. This question will be discussed
in Chapters III. and V.
The great ideal of most educationists is for all children
to have a healthy mind in a healthy body, and proper
physical and mental training are the only means of attaining
such a condition.
Physical training will be discussed in Chapter II., and
the nutrition and training of the nervous system in
Chapter VI.
Characteristics of Children in Health. — The common
characteristics of children in health are well known, and
need only a very short description. They show great
activity of mind and body ; when at play they put their
whole energy into their games, and when at work they are
INTRODUCTORY
13
able to devote attention and concentration to their lessons.
The memory is good in children, and the educational
attainments of a child should be such as would be expected
at that particular age. They are well nourished ; their
weight and height should correspond fairly closely to what
it should be at their age. The following are the measure-
ments given by the Anthropometrical Committee of the
British Association :
Boys.
Girls.
Age.
Weight in
Pounds.
Height in
Inches.
Weight in
Pounds.
Height in
Inches.
5
39-9
41-00
39-2
40-55
6
44.4
44-00
41-7
42-88
7
49-7
45-97
47-5
44-45
8
54-9
47-05
52-1
46-60
9
60-4
49-70
55-5
48-73
10
67-5
51-84
62-0
51-05
11
72-0
53-50
68-1
53-10
12
76-7
54-99
76-4
55-66
13
82-6
56-91
87-2
57-77
14
92-0
59-33
96-7
59-80
15
102-7
62-24
106-3
60-93
16
119-0
64-31
113-1
61-75
The skin is clear and elastic, and has a good supply of
subcutaneous fat. The size of the head proportionally to
the body is larger than in the adult. The chest should be
broad from side to side and show no deformity. The
senses are very acute, and the time that elapses between
the stimulation of a sense organ and the response is very
short. The muscles have good tone and feel firm. In
childhood the nervous system is characterized by its com-
parative instability ; it has not yet settled down to the
stable form characteristic of mature life. The higher
centres are as yet imperfectly developed, and do not exer-
cise such a good control over the lower centres ; hence
abnormal forms of nervous actions are common even in
healthy children.
CHAPTER II
THE SKELETON AND MUSCULAR SYSTEM
I. THE SKELETON
BY the term " skeleton " is meant the parts of the body
which remain after the softer structures have been dis-
integrated or removed, and includes not only the bones,
but also the cartilages and ligaments which bind them to-
gether. In the restricted sense of the word, the skeleton
denotes the bony framework of the body, and it is in this
sense that it is generally used in human anatomy.
The skeleton supports the softer structures grouped
around it, and also protects the many delicate organs
lodged within its cavities. The connection of its various
parts by joints converts its segments into levers, which
constitute a means of locomotion and movement.
Bone may be regarded as white connective-tissue fibres
which have become calcified tissue.
There are two methods of study applicable to bones,
just the same as to all tissues of the body. The first
method is by the naked eye, or macroscopically, and the
second by means of the microscope, and it is by this method
that we ascertain its minute or histological structure.
The naked-eye appearance of bones is known to every-
one, and they have been classified by anatomists into
four classes (according to their shape) — long, short, flat,
and irregular.
Long Bones. — A long bone consists of a shaft and two
extremities. The shaft is a hollow cylinder ; the walls
consist of dense, compact tissue, and the cavity in the
14
FIG. 3.— THE SKELETON.
Skull ; B, lower jaw ; C, cervical vertebrae ; D, clavicle ; E, scapula ;
F, sternum ; 0, humerus ; H, ulna ; /, radius ; J, wrist or carpal
bones ; K, metacarpal bones ; L, finger-bones ; M , floating ribs ;
N, lumbar vertebrae ; 0, hip-bone ; P, sacrum ; Q, femur ; R, patella ;
8, fibula ; T, tibia ; U, tarsal or feet bones ; V, metatarsal bones ;
X, toe-bones.
16
HYGIENE
centre is called the " medullary canal." The extremi-
ties are generally somewhat expanded, for purposes of
articulation, and afford a broad surface for muscular
attachments.
The shaft is covered by a fibrous membrane — the peri-
osteum. This contains bloodvessels
t which run by minute passages into
the substance of the bone. The ex-
tremities, as they enter into articula-
tion with other bones, are covered
with a cap of smooth or hyaline
cartilage.
The interior of the long bones is
hollow, in order that strength may
be combined with lightness. The
medullary canal is filled with spongy
bone, fat, and cells, which cause the
formation of the cells of the blood,
all the contents being termed the
" bone-marrow."
The marrow is well supplied with
blood, and the vessels within the
medullary canal communicate with
those of the periosteum. The long
bones are found in the limbs, and
act as a system of levers, sustaining
the weight of the body and con-
ferring locomotion.
The bones belonging to the class
of long bones are — Clavicle, or
collar-bone ; humerus, or arm-bone;
radius and ulna — the bones of the
PIG. 4. — SHIN-BONE (TIBIA) SAWN IN Two
ALONG ITS LENGTH.
2, Struts and stays of spongy bone support-
ing 7, the upper and lower articular
surfaces ; 3, compact bone forming the
shaft ; 4, marrow cavity ; 6, periosteum.
THE SKELETON AND MUSCULAR SYSTEM 17
forearm ; femur, or thigh-bone; tibia and fibula, the bones
of the leg ; etc.
Short Bones. — Where a part of the skeleton is intended
to be strong and compact, and is to be allowed a very small
degree of movement, it is divided into a number of small
pieces united together by ligaments. The separate bones
FIG. 5. — DIAGEAM OF SKELETON OP THE HAND AND FINGERS,
SHOWING THE CHARACTERS OF SHORT BONES.
A, Lower end of radius ; B, lower end of ulna ; C, wrist or carpal bones ;
D, metacarpal bones; E, F, G, phalanges or finger bones (short
bones).
are short and compressed, such as the carpal bones of the
hand or the tarsal bones of the foot.
On section, the short bones are seen to be made of spongy
bone, surrounded externally by a thin layer of compact
bone.
Flat Bones. — Where a part of the skeleton is to provide
either extensive protection or broad surfaces for muscular
2
18
HYGIENE
J
attachment, the bony structure is expanded into broad,
flat plates, as in the bones of the skull and the shoulder-
blade. These bones are composed of two thin layers of
compact tissue enclosing between them a variable quantity
of spongy bone.
The flat bones are — The occipital, parietal, frontal, nasal,
lachrymal, vomer, scapula, os innominatum, and ribs.
Irregular or Mixed Bones are such as, from their peculiar
form, cannot be classified in any of the preceding groups.
They consist of a layer of compact tissue externally, and
of cancellous tissue
within.
The irregular bones
are — The vertebrae,
sacrum, coccyx, tem-
poral, sphenoid, eth-
moid, malar, superior
maxillary, inferior
maxillary, and palato.
The Microscopical
Structure of Bone can
be studied by taking
a piece of bone and
placing it in dilute
hydrochloric acid,
which will dissolve its
inorganic constituents,
and then cutting the organic framework into very thin
sections and staining them with various dyes, in order that
their constituent cells should stand out more clearly.
A bone after it has been softened as described above can
be readily torn into shreds by means of a pair of forceps.
This is because bone is made up of white fibrous tissue
impregnated with lime salts, which are most probably
formed by the cells which remain in certain spaces called
" lacunae."
When a section of compact bone is examined, a number
Fio. 6. — PARIETAL BONB— AN EXAMPLE
or A FLAT BONE.
THE SKELETON AND MUSCULAR SYSTEM 19
of small canals, called " Haversian canals," will be seen,
and around each canal concentric layers, or lamellae, of
bone are placed. In between the lamellae small spaces
containing soft protoplasmic cells will be seen. The pro-
cesses of the ceUs are contained in ramified passages which
Join contiguous cells. The cells are called the " bone
corpuscles," the spaces in which they lie the " lacunae,"
and the ramified passages in which the cell processes course
are called the " canaliculi."
1
3
FIG. 7. — LTTMBAB VERTEBRA — AN EXAMPLE OF AN IRREGULAR BONE.
The Haversian canals contain bloodvessels and marrow,
and the nourishment of the bone is derived from these
vessels. The canaliculi communicate with neighbouring
cells and with the Haversian canals.
In spongy bone the regular Haversian systems are re-
placed by spicules of bone enclosing large irregular spaces
rilled with marrow. The lamellae in the spicules contain
lacunae and canaliculi. Passing right through the lamellae
are certain fibres, called the "decussating fibres of Sharpey."
20 HYGIENE
Ligaments or tendons when attached to any bone are
joined to these fibres ; the union thus becomes very strong.
A section of hard bone can be obtained with a fine saw,
and the section is rubbed down to the required thickness
on an oilstone, and then examined with the microscope.
The Haversian canals would then be seen as holes, sur-
rounded by lamellae of bone, and the lacunae and canaliculi,
because they are filled with dust and air, appear as black
dots and lines. The marrow and bone cells will have been
destroyed by the process.
Fio. 8. — DIAGRAM SHOWING THE MICROSCOPIC STRUCTURE OF
COMPACT BONE.
A, Outside layers ; B, Haversian canal ; C, lacuna containing
branching bone cell.
The Chemical Composition of Bone can be ascertained by
igniting it in a covered porcelain dish in a blow-flame. The
organic matter at first becomes charred, and finally dis-
appears as carbon dioxide and water, and there remains a
brittle white residue composed entirely of earthy salts,
which by chemical test are found to be chiefly phos-
phates and carbonates of lime. The difference between the
weight of the bone placed in the porcelain dish and the
weight of the residue represents the weight of the organic
matter.
THE SKELETON AND MUSCULAR SYSTEM 21
The chemical composition of bone is found to be as
follows :
Animal matter
Calcium phosphate
Calcium carbonate
Other salts
Development and Growth
of Bone. — During the early
stages of development the
fertilized ovum divides into
a large number of cells, and
these cells become arranged
into three layers — an outer
layer, or epiblast, from which
the skin and the nervous
system is developed ; an
innermost layer, or hypo-
blast, from which the lining
mucous membrane of the
alimentary canal is formed ;
and a middle layer, or
mesoblast, from which the
bony and muscular con-
stituents of the body are
developed. Hence early in
foetal life a layer of cells
is set apart to develop into
the skeletal, supporting, and
muscular tissue of the
embryo.
The bony stage of the
skeleton is preceded by
either a membranous or
cartilaginous stage. The flat bones are developed in
membrane, and the long bones in cartilage.
In the intramembranous form of osteogenesis, or bone
FIG. 9. — DIAGRAM SHOWING THE
FORMATION or BONE FROM CAR-
TILAGE.
a, Cartilage cells arranged in rows ;
b, enlarged cartilage cells close to
line of formation of bone ; c, bone
covered with bone-forming and
bone-destroying cells.
22 HYGIENE
formation, bony spicules containing lime salts, together with
bone corpuscles and cells, are formed within a proliferation
tissue consisting partly of cells and partly of a more or less
perfectly developed homogeneous ground substance.
The intracartilaginous form of ossification takes place in
long bones, and in this process various definite stages
may be identified. The cartilage cells at first become
enlarged and arranged in rows; the matrix between tin
cartilage cells becomes calcified by the deposition of a
large amount of calcium salts ; the rows of cells become
joined together, and into the spaces so formed extend the
bloodvessels derived from the vascular layer of the fibrous
membrane covering the outer surface of bone. Bone-
forming and bone-destroying cells accompany these vessels,
the former building up true bone at the expense of tin-
calcified cartilage, the latter causing an absorption of newly -
formed bone, and results in its conversion into a marrow
cavity, and thus all the cartilage is replaced by true bone.
The Skull.
In order to understand the structure of the skull, it is
advisable for you to have a skull before you, or. if that is
not possible, a careful study of the figure of the skull should
bo made.
Some of the bonos of the skull form the cranium, or
brain-box, and others are the bones of the face. Tin-
cranium is made up of a base, upon which the brain lies,
and a vault, which covers the sides and upper surface of
the brain.
The bones of the cranial vault are the frontal, parietal,
occipital, and temporal bones.
The anterior part of the cranial vault is formed by the
frontal bone ; this was originally made of two halves, which
have joined by a bony suture.
The middle part of the cranial vault is formed by the
two parietal bones, which are joined above in the middle
line by a serrated suture.
THE SKELETON AND MUSCULAR SYSTEM 23
The posterior part of the vault of the cranium is formed
by the occipital bone, which is joined anteriorly to both
parietal bones.
The lateral wall of the cranium is formed from before
backwards by the frontal, temporal, and occipital bones.
FIG 10 —LATERAL VIEW OF THE HUMAN SKULL.
0, inferior maxilla, or lower jaw-bone.
The base of the skull, when examined from the inner or
cerebral surface, wiU present three cavities, <
which lodge different parts of the brain.
24 HYGIENE
The anterior fossa is formed by the frontal bone and the
anterior part of the sphenoid bone.
The middle fossa is made up of a narrow middle portion,
with two wide lateral portions. It is formed by the
sphenoid bone and the two temporal bones.
The posterior fossa is formed by the occipital bone and
the posterior portions of the temporal bones. The floor of
FIG. 11. — INNER SOTIFACE OF THE BASE OF SKULL.
A, Anterior fossa ; B, middle fossa ; 0, posterior fossa.
the posterior fossa is perforated by an opening called the
"foramen magnum," through which the brain becomes
continuous with the spinal cord.
When the base of the skull is examined, a large number
of small openings will be seen perforating it ; these are
called " foramina," and are for the passage of nerves and
bloodvessels to and from the cranial cavity.
THE SKELETON AND MUSCULAR SYSTEM 25
The facial part of the skull contains the following bones :
The upper jaw bones, right and left. Above they form
the floor of the orbit (eye socket) ; behind they articulate
with the cheek or malar bone. In front and below they
join together to form the upper jaw and the bony palate ;
FIG. 12. — FACIAL ASPECT OF THE SKULL.
A, Frontal bone ; B, nasal bone ; 0, superior maxilla, or upper jaw-bone ;
D, lower jaw-bone, or inferior maxilla.
above and in front they are separated by the cavity of
the nose.
The lower jaw, a single bone, is made up of a horizontal
portion and two perpendicular portions ; the latter articu-
late with the temporal bone of each side.
26 HYGIENE
The nasal bones — two small bones forming the roof of
the anterior part of the nasal cavities.
The lachrymal bones are two small flat bones, one of
which lies on the inner side of each orbit.
The cheek bones bound the orbits below and to the outer
side.
The cavity of the nose should be carefully examined. A
bony septum, formed by the vomer bone, divides it into
two halves. The ethmoid bone separates the nose from
the cranial cavity ; the lateral wall is formed by the upper
jaw-bone, and projecting from this the scroll-like turbinate
bones will be seen.
The skull is of great strength, in order that it may
protect the brain, eye, and ear, from external violence,
and at the same time it affords attachment for the powerful
muscles of mastication.
The Backbone, or Vertebral Column.
Tin- backbone is made up of a number of separate bones,
called "vertebrae" (from vertere, to turn). The
are originally thirty-three or thirty-four in number, but
during the growth of a child five of the lower ones fuse
together to form a broad curved bone, called the sacrum,
while the four lowest form a rudimentary tail, called the
coccyx.
The vertebrae are named according to the position they
occupy, and from above downwards they are called " cer-
vical " (seven in number), " dorsal " (twelve in number),
" lumbar " (five in number), " sacral " (five in number, and
fused together to form the sacrum), " coccygeal " (four in
number).
Structure of a Vertebra. — A short account will be given
of the general structure of the vertebrae, and it may be
noted that there are certain differences between vertebrae
from different regions ; but it is not within the scope of
this book to give any account of them.
THE SKELETON AND MUSCULAR SYSTEM 27
2-1
C. 0
FIG. 13.— THE SPINAL
COLUMN.
1-7, Cervical (7) ; 7-19, thoracic
(12) ; 19-24, lumbar vertebrae
(5) ; 24-29, sacrum (=5) ; 29-
34, coccyx (=5). Notice the
bends, or flexures, of the
column.
FIG. 14. — DIAGRAM SHOWING
STRUCTURE OF VERTEBRAL
COLUMN AFTER LONGITUDINAL
BISECTION.
Note the spinal canal, which
lodges the spinal cord, and the
lateral openings, called " fora-
mina," through which the spinal
nerves pass out from the canal.
28
HYGIENE
Each vertebra consists of a disc-like mass of bone, called
the " body." Behind this is the vertebral arch, connected
with the body by two pillars. From the back of the arch
there projects backwards the spinous process, and from
each side projects outwards a transverse process. The
bodies of the vertebrae are united together by tough pads
of fibro - cartilage, which are called intervertebral discs.
FIG. IS. — THORACIC VERTEBRA,
SIDE VIEW, ILLUSTRATING
THE IMPORTANT ANATOMICAL
PARTS OF A VERTEBRA.
1, Body ; 2 and 4, surfaces which
articulate with ribs; 3, trans-
verse piocess; 5, spinous pro-
cess ; 6 and 7, surfaces which
articulate with the next verte-
brae above and below.
FIG. 10.— THORACIC VERTEBRA : VIEW
or UPPER SURFACE.
J, Body; 2, vertebral canal; 3.
spinous process; 4, transverse pro-
cess; 5, surface articulating with
vertebra above.
The arches of contiguous vertebrae articulate by definite
joints.
By the joining together of the vertebrae there is formed
a strong flexible column. The arches form a canal in
which the spinal cord lies.
The Atlas and Axis. — These are the two upper cervical
vertebrae, modified in structure so as to allow articulation
with the skull.
The atlas is ring-shaped; it has no body, and on the
THE SKELETON AND MUSCULAR SYSTEM 29
upper surface of each half of its arch there are two oval
depressed surfaces for articulation with the condyles of
the skull.
The axis, or second cervical vertebra, has a pivot-
like process projecting from its upper surface, and this
articulates with the atlas, and it is by this Joint that
rotatory movements of the skull take place.
FIG. 17. — DIAGRAM SHOWING THE
STRUCTURE OF THE ATLAS, OR FIRST
CERVICAL VERTEBRA.
1, Anterior arch ; 2, vertebral canal ;
3, posterior arch ; 4, spinous pro-
cess ; 6, surfaces articulating with
condyles of the skull ; 7, transverse
process ; 9, surface articulating with
special process of axis.
FIG. 18.— THE Axis, OR
SECOND CERVICAL VER-
TEBRA : VIEW OF UPPER
SURFACE.
1, Body; 2, vertebral canal ;
3, spinous process ; 4,
transverse process ; 5,
posterior arch ; 6, surfaces
articulating with atlas ;
9, odontoid process.
The sacral vertebrae all fuse together to form the sacrum,
which is wedged in between the two hip-bones.
The coccyx is the rudiment of a tail.
The ribs number twelve on each side. They articulate
behind with the bodies and transverse processes of the
dorsal vertebrae, and then sweep forward to meet the
sternum, or breast-bone, in front. The upper seven are
Joined to the sternum by means of cartilages, called
30
HYGIENE
" costal cartilages." The cartilages of the next three ribs
are connected indirectly to the sternum ; they are first
joined to one another, and then to the seventh rib. The
last two are called " floating ribs," because they do not
reach the sternum at all.
FIG. 19.— BONY FRAMEWORK or TUB CHEST, OB THORAX.
1-12, Ribs ; 13-15, sternum ; 16-17, the thoracic part of vertebral column
(twelve vertebra).
The sternum, or breast-bone, lies in the front of the
chest. The dorsal vertebrae, sternum, and ribs, form the
skeleton of the thorax, which contains the heart and
lungs.
THE SKELETON AND MUSCULAR SYSTEM 31
The bones of the upper limbs are —
1. The clavicle, or collar-bone, extends from the shoulder-blade to the
upper part of the sternum. Feel it in your own body.
2. The scapula, or shoulder-blade, can be felt at the back of the upper
FIG. 20. — POSTERIOR (I.) AND ANTERIOR (II.) VIEW OP HTJMERUS, OB
UPPER- ARM BONE.
A, Head of the bone, articulating with the scapula, or shoulder-blade;
B, shaft ; C, cavity which receives the olecranon process, or upper
part of the ulna ; D, surface which articulates with ulna ; E, surface
articulating with radius ; F, rough processes to which musclea are
attached.
part of the chest. It is flat and triangular in shape, with a definite ridge
running across it.
3. The humerus, or arm-bone, articulates above with the scapula,
and below with the bones of the forearm. The head can be felt inside
the axilla when the arm is moved. Its lower end is flattened from
32
HYGIENE
Fio. 21.— AHTERIOB (I.) AKD
nmiiHH (IL) Votw OF
RADIUS (D) AKD ULHA (E).
A and B, Surfaces which
articulate with humerus ;
O, olecranon process of ulna ;
F, surfaces which articulate
with carpal bones of wrist.
Fio. 22.— THE PELVIS.
A, The sacrum ; B ,
crest of the hip-
bone ; C, the cavity
(acctabulum) which
. receives the head of
the femur; D, hole
which lightens the
weight of the bone ;
E, metal plate uni-
ting the pubcs (this
is fibrous cartilage
in life) ; /\ right hip-
bone.
THE SKELETON AND MUSCULAR SYSTEM 33
before backwards, and on each side are projecting processes to which
important muscles are attached.
F F
i a
FIG. 23.— FRONT (I.) AND HIND
(II.) VIEW OF FEMUR.
A, Head of the bone which articu-
lates with the hip - bone ; 0,
shaft ; D and E, rough pro-
cesses to which muscles are
attached ; F, surface which
articulates with tibia.
\E/
I n
FIG. 24.— HIND (I.) AND FRONT
(II.) VIEW OF TIBIA (B) AND
FIBULA (A).
C, Head of the fibula articulating
with tibia ; D, surface articu-
lating with lower end of femur ;
E, surfaces which articulate
with astragalus.
4. The radius and ulna are the two bones of the forearm — the radius
on the outer or thumb side, and the ulna on the inner side.
3
34
HYGIENE
5. The carpal or wrist bones are eight in number ; Joined together by
joints and strong ligaments.
6. The metacarpal bones He in the palm, one for each thumb and finger.
7. The phalanges are fourteen in number, two to each thumb and
three for each finger.
Fig. 5 shows the relationships of the bones of the hands.
The bones of the lower extremity are —
1. The hip or innominate bone has a very peculiar shape. It articu-
lates with the sacrum behind, and with its fellow of the opposite side in
front. The sacrum and both hip-bones form the pelvis, on each side
of which there is a depression for the head of the thigh-bone to articulate.
2. The femur, or thigh-bone, is the longest bone in the body. It
Fio. 25. — OUTER (I.) AND TUNER (II.) VIEW OF FEET- BOXES.
A, Heel-bone ; B, surface on astragalus which articulates with l«-g-
bones ; C, tarsal bones ; D, metatarsal bones ; E. F, 0, first, second,
and third toe-bones, or phalanges.
articulates above with the hip-bone, and below with the upper surface
of the tibia, or inner leg-bone.
3. The tibia and fibula are the bones of the leg — the tibia on the inner
and the fibula on the outer side.
4. The knee-cap, or patella, is a small flat bone felt in front of the knee.
5. The tarsal bones are seven in number ; the ankle-joint is formed
by the articulation of one of these bones — namely, the astragalus — and
the lower ends of the tibia and fibula.
6. The metatarsal bones and the phalanges correspond to similar
bones of the hand.
THE SKELETON AND MUSCULAR SYSTEM 35
Joints and Ligaments.
A joint is a mode of union between any two separate
segments or parts of the skeleton. Joints are divided into
two great groups — namely, the perfect, or movable ; and
the imperfect, or practically immovable.
Perfect joints, like the hip, shoulder, and knee, allow
great freedom of movement; while imperfect joints, like
the sutures of the skull or those between the vertebra,
allow very little movement. Entering into the structure
of a joint, we generally find portions of two bones, which
are covered by smooth hyaline cartilage. Each joint is
enclosed in a bag made of white fibrous tissue, called
the " capsule." Supporting the capsules there are gener-
ally some special bands of white fibrous tissue, called
" ligaments," which tend to check excessive movement.
The two bony surfaces are held in apposition by the tonic
action of the muscles surrounding the joint. Even in the
most movable joints there are certain limitations to its
movements, brought about by the stretching of ligaments,
interlocking of bony prominences, and the contact of sur-
rounding muscles.
All the structures inside a perfect joint which are not
lined by cartilage are covered by a smooth, glistening mem-
brane, called the synovial membrane. This secretes a
fluid called the " synovial fluid," which acts as a lubricant
to the joint.
In the imperfect joints the bones are united by
cartilage, and being bound together firmly by ligaments,
only a very small degree of movement is allowed.
The imperfect joints are divided into two great classes :
those which allow of no movement — e.g., sutures of the
skull-bones — and those which allow a small degree of move-
ment— e.g., pubic symphysis, joints between the bodies
of the vertebra.
The perfect or movable joints are of various kinds.
36 HYGIENE
Ball-and-socket Joints allow movements to take place
in all directions ; such joints exist at the hip and
shoulder.
Gliding Joints have nearly flat surfaces, and admit of
only a limited amount of gliding movement, as in tin-
articulation of the hand-bones, foot-bones, and the articular
processes of the vertebrae.
Hinge Joints. — This form of joint allows movement
in one plane. The elbow-joint is the beet example of a
Fio. 20. — SHOULDER • JOINT. COLLAR • BOMB, SHOULDER-BLADE, AND
UPPER END or HDMERUS, SHOWN SEPARATE AND BOUND TOGETHER
BY LIGAMENTS.
hinge joint ; the only movements allowed are those of
flexion and extension.
The wrist, knee, and ankle, are also hinge joints, but they
allow a slight amount of lateral movement as well.
Pivot Joints. — This type allows of only one form of move-
ment— namely, rotation. A good example of this is the
joint between the atlas and axis.
Condyloid Joints. — These allow all varieties of angular
movement and circumduction, as in the metacarpo-
phalangeal joints of the thumb.
THE SKELETON AND MUSCULAR SYSTEM 37
Joints o! the Skull. — The only movable joint in the skull
is that between the lower jaw and temporal bone. It is
covered by rather a loose capsule, and allows all movements
concerned with mastication.
The Joints of the Trunk. — The vertebrae are joined to-
gether by intervertebral discs, and their
articular processes by proper joints. In
children the spine is very flexible.
The Joints of the Upper Limbs. — The
clavicle articulates with both the sternum
and scapula.
The shoulder- joint is formed by the
articulation of the head of humerus with
the glenoid cavity of the scapula. It allows
very free movement.
The elbow-joint: The bones entering
into the formation of this joint are the
lower end of humerus and upper end of
ulna and radius. The radius articulates
with the humerus, and also above and
below with the ulna. Flexion and exten-
sion are the movements of the elbow- joint,
while the superior radio-ulnar joint allows
pronation and supination.
The wrist- joint is formed by articulation
of the lower end of radius and ulna with
the upper row of carpal bones. It allows
flexion, extension, and lateral movements.
The carpal joints allow very little
movement.
The movements of the fingers are
flexion, extension, and lateral movements
(adduction and abduction).
Joints of the Lower Limb. — The hip-joint is formed by
the articulation of the head of the femur with the innomi-
nate bone. It is a ball-and-socket joint, and allows very
free movement.
FIG. 27. — ELBOW
AND WRIST
JOINTS SHOWN
STRAPPED BY
LIGAMENTS.
Fio. 28.— HIP- JOINT: THIGH-BONK, HIP- BONE, AND HALF TUB SACRUM,
SI10WN SEPARATE AND BOUND TOGETHER BY LlGAMhMS.
Fio. 29. — KNEE-JOINT: LOWER END OF FEMUR, UPPER ENDS OF
TIBIA AND FIBULA, AND PATELLA, SHOWN SEPARATE AND BOUND
TOGETHER BY LIGAMENTS.
THE SKELETON AND MUSCULAR SYSTEM 39
The knee-joint is a hinge joint between the lower end of
the femur and the upper end of the tibia. The con-
cavities of the articular surfaces on the
upper end of the tibia are deepened »v
two semilunar cartilages. The patella,
or knee-cap, lies in front of the joint,
and running from its lower border to
the anterior surface of the upper end of
the tibia is a strong ligament called the
" ligamentum patellae."
The ankle-joint is a hinge joint, and
permits of only flexion and extension. It
is formed by the articulation of the
upper surface of astragalus and lower
ends of the tibia and fibula.
The joints of the foot are similar to
those of the hand, except that move-
ments are far more limited ; this is
especially the case with the big toe as
compared with the thumb. The shape
of the bones of the foot and their
articular surfaces are such as to form
various arches, and the integrity of
these arches is very important for
proper walking, because when some of
them disappear, as in flat-foot, walking becomes difficult,
and in some cases painful.
2. THE MUSCULAE SYSTEM.
The movements of the various parts and organs of the
body are caused by the action of muscle cells, which are
characterized by a special structure and by a special
function of contracting under the influence of an appro-
priate stimulus.
There are three different forms of muscle cells :
1. The striated or voluntary muscle cells, which make up the skeletal
muscles.
30.— ANKLE-
JOINT AND
UPPER SURFACE
OF FEET-BONES
SHOWN STRAPPED
TOGETHER BY
LIGAMENTS.
40 HYGIENE
2. The non-striated or involuntary muscle cells, which are present
in the walls of the intestine, bloodvessels, etc.
3. The cardiac muscle cells, which are striated, but involuntary, and
form the heart muscle.
In this section we are only concerned with the skeletal
or voluntary muscle.
Each voluntary muscle fibre or cell is an elongated, pale,
FIG. 31. DIAGRAM SHOWING STRUCTURE OF THREE FORMS OF
MUSCULAR CELLS.
a, Involuntary or non-striated muscle cell ; b, voluntary or striated
muscle cell ; c, cardiac or heart muscle cell.
transparent structure. Each has an elastic sheath, called
the " sarcolemma," which encloses the contractile sub-
stance. The cytoplasm of the cell, or sarcoplasm, is charac-
terized by alternate dark and light stripes, which run
THE SKELETON AND MUSCULAR SYSTEM 41
transversely across the fibre ; hence it is called " cross -
striated" or "striped" muscle. If the fibre be examined
with a very strong microscope, it will be seen to be com-
posed of a number of small fibrils. The nucleus of the
cell is situated just within the sarcolemma.
A large number of these fibres become aggregated to-
gether, and are surrounded by connective tissue, and thus
form a muscle.
Each muscle is composed of a number of fasciculi, or
bundles, arranged together in different muscles in different
ways, so as to give rise to the particular form of the muscles
in question. Then each muscular bundle, or fasciculus, is
composed of muscle fibres, and each fibre is made up of
fibrils.
Each muscle, fasciculi, and fibres, are surrounded by
connective tissue, by means of which they are brought
into firm and intimate relation with the bony or other
attachments of the muscle.
Each muscle arising from one bone is inserted into
another, and in its course it passes over one or more joints.
A muscle when excited to contract shortens in length
and swells in girth ; thus it pulls on the bones to which it
is attached, and if one of these be fixed the other moves.
The movement takes place at the joint over which the
muscle passes. Muscles on contraction can move the bone
from which they have origin or the bone to which they are
inserted. A muscle is said to have origin from that bone
which is the more fixed.
Tendons. — Tendons are the structures by which muscles
become attached to bones. The fibres of the tendon run
into and become part of the bone. Tendons are so securely
attached to bones that it is easier to rupture a muscle or
break a bone than to detach a tendon from a bone.
Tendons are generally long, slender white cords which
run and become inserted into bones at some distance from
the main portion of the muscle.
Properties of Muscle. — The physiological properties of
42 HYGIENE
muscle can be well studied in the frog. By one cut of the
scissors decapitate a frog ; and having done this, pass a
pin down the vertebral canal and destroy the spinal cord.
Divide the skin around the abdomen with a pair of scissors,
and, taking hold of the skin below the cut, pull it from the
lower limbs. The muscles will be thus exposed. Care-
fully separate the muscles at the back of the thigh ; a
white, glistening thread will appear. This is the main
nerve of the thigh, and is called the sciatic nerve. It
supplies the greater number of the muscles of the thigh
and leg. Stimulate it by touching it with a pin or needle ;
the muscles contract. Further, show that the muscles
themselves respond directly to stimuli by pricking them,
when they will contract.
Normally, impulses pass along the nerves and cause the
muscles to contract ; but the muscles themselves are
irritable and capable of being stimulated directly.
In a muscle freshly removed from the body there are
three properties that can be easily shown. Remove one of
the calf muscles of a frog, and if it is suspended by one end,
and a small weight attached to the other, the muscle will
be stretched ; this is called extensibility. The muscle offers
certain resistance to being stretched, and tends, when the
weight is removed, to return to its former shape ; this
property is called elasticity.
When the muscle is pinched, pricked, or if an electrio
spark is passed into it, it will contract sharply ; it becomes
shorter and thicker for a moment, and then returns to
its original condition. This is contractility, and it is by
means of this property that a muscle is able to do its
work.
Muscle contains 75 per cent, of water, and combined with
it are the proteins myosinogen and paramyosinogen,
glycogen, certain organic waste products, and mineral
salts.
Some of these substances are combined to form the
living contractile substance ; others form the food or
THE SKELETON AND MUSCULAR SYSTEM 43
waste products of the same. A resting muscle is alkaline
in reaction, but when fatigued or dead it is acid in re-
action. This is due to the formation of sarcolactic acid —
an acid similar to that formed in milk when soured by
bacteria.
When at rest there is a certain amount of oxidation
going on in the tissues, and therefore oxygen is absorbed
and carbon dioxide eliminated ; but during contraction
there is a far greater amount of oxygen absorbed and
carbon dioxide eliminated. During this process energy is
evolved by the breaking up of complex substances, and the
formation of simple products, like carbon dioxide. Some
of this energy is used up in doing work, some takes the
form of heat and warms the body, while a small portion is
converted into electricity.
Rigor Mortis. — The condition of stiffness into which
muscles enter after death is called rigor mortis. It comes
on much more rapidly when the muscles are fatigued ;
thus, soldiers in battle and hunted animals stiffen almost
as soon as they drop dead. The stiffness lasts for some
hours, and then disappears, when putrefaction commences.
This stiffness is due to the clotting of one of the proteins
present in muscle, the soluble myosinogen being con-
verted by the action of a ferment into the insoluble
myosin.
Muscular Action. — The action of some of the muscles of
the body should be studied in the living subject.
Muscles of the Head and Neck. — Note how facial expres-
sions are caused by the contraction of various muscles of
the face.
Place a finger on the outer surface of the angle of the
lower jaw-bone ; it will be found to be covered by a muscle.
When the teeth are clenched, this muscle will be felt to
harden. This is called the masseter muscle, and will be
found to be attached above to a ridge of bone in front of
the ear, and below to the outer surface of the angle of the
jaw. If a finger is placed deep or slightly below the
44 HYGIENE
angle of the jaw, the tongue and lower jaw moved, various
muscles will be felt to contract. These are muscles which
pass from the tongue or jaw-bone to be inserted into the
hyoid bone.
At the back and sides of the neck important muscles
will be felt. On each side of the neck a long muscle will
be found to run from the upper surface of the sternum and
inner end of the clavicle to a bony process behind the ear,
called the " mastoid process." This muscle is therefore
called sterno-mastoid, because it passes from the sternum
to the mastoid process.
Muscles of the Upper Limbs. — Examine the shoulder
while the arm lies by the side. On the outer border of
the shoulder the sharp bony projection formed by the
spine of the scapula, or shoulder-blade, will be felt. Just
below this the deltoid muscle will be felt. It arises above
from the outer border of the spine of the shoulder-blade
and anterior border of the outer end of the collar-bone,
and is inserted below into the bone of the arm, or humerus.
Its action is to pull the arm from the side to the horizontal
position.
In front of the arm the biceps muscle will be seen, while
on the posterior aspect of the upper limb lies the triceps
muscle. The biceps is a flexor, while the triceps is an
extensor, of the elbow ; therefore the triceps has quite the
opposite action to that of the biceps, and is called its
" opponent." While the biceps contracts, the triceps
slackens, and vice versa.
In front of the forearm a number of muscles will be
felt ; they are the flexors of the wrist and the joints of the
hand and fingers. Behind the forearm are their antago-
nists, the extensors.
Muscles connecting the Upper Limbs with the Trunk. —
The armpit is a pyramidal-shaped structure bounded by
muscles, and containing arteries, nerves, veins, and con-
nective tissue. The anterior border of the armpit is formed
by the great pectoral, or breast muscle, which arises from
THE SKELETON AND MUSCULAR SYSTEM 45
FIG. 32. — SUPERFICIAL MUSCLES.
4 , Stcrno-mastoid ; B, deltoid ; C, pectoralis major ; D, biceps ;
E, triceps ; F, supinator of forearm ; 0, extensors of fingers ;
H, latissimus dorsi ; /, serratus magnus ; J, rectus abdominis ;
K, flexors of thigh (extensors of knee) ; L, hamstring muscles ;
M , calf muscles (extensors of foot) ; N, flexors of foot (extensors
of toes).
46
HYGIENE
the breast-bone, costal cartilages, and collar-bone, and is
inserted into the humerus, or arm-bone.
The posterior border is formed by the latissimus dorsi,
Fio. 33. — MUSCLES or BACK.
T, Trapeziu* ; Ft, lloxors of fingers ; other letters as in Fig. 32.
which arises from the hip-bone and the lumbar vertebrae,
and is inserted into the huraerus, its action being to pull
the humerus downwards and backwards.
There are two other large muscles connecting the upper
THE SKELETON AND MUSCULAR SYSTEM 47
limb with the trunk. The serratus magnus arises from the
ribs at the side of the chest, and is inserted into the inner
border of the shoulder-blade, and its action is to pull the
shoulder forward. The trapezius arises from the skull
and vertebrae of the neck and back, and is inserted into the
outer part of the posterior border of the collar-bone and
the upper border of the spine of the shoulder-blade ; its
action is to pull the shoulder-blades back.
Muscles of the Trunk. — The powerful muscle of the back
is called the erector spinse. It is made up of several
smaller muscles, which cover the whole length of the spine
from the sacrum to the back of the head.
The abdominal wall is made up of several muscles
which arise from the ribs, bones of the pelvis, and lumbar
vertebrae, and are inserted into a fibrous layer in the middle
line, called the " linea alba."
Muscles of the Lower Limbs. — The muscles of the thigh
may be divided into three great groups. In front are the
muscles which flex the thigh on the abdomen; and since
these muscles gain insertion to the patella and the anterior
surface of the tibia, their contraction will also result in
extension of leg on the thigh. Behind are the opponents
of these muscles, which extend the thigh at the hip-joint,
and, by their insertion in the bones of the leg, flex the leg
on the thigh at the knee-joint. On the inner side are the
adductors, running from the pelvic bone to the inner side
of the femur and tibia, and their action is to pull the lower
limb towards the middle line.
In the leg there are two sets of muscles. The extensors
lie anteriorly, and arise from the anterior surface of the
tibia and fibula. They have long tendons which are
inserted into the metatarsal bones or phalanges of the toes.
Their action is to extend the toes, and one of them is a
powerful inverter of the foot.
On the posterior surface of the leg there are two groups
of muscles. The superficial group is inserted into a
strong tendon, called the tendo Achillis, which is attached
48 HYGIENE
to the posterior surface of the heel-bone, or os calcis. The
deeper group of muscles on the posterior aspect of the leg
have long tendons, and are inserted in the under-surface
of the phalanges of the toes ; they cause flexion of the
toes.
Relation of the Muscular System to the Nervous System.—
All the striated or skeletal muscles can be controlled volun-
tarily in the execution of movements, but we are so accus-
tomed to perform various movements that they are done
by us quite unconsciously. The non-striated musculature
is controlled by the sympathetic nervous system, and is
not under voluntary control.
A certain part of the brain is set aside to govern the
action of the voluntary muscles. The posterior part of
each frontal lobe of the brain contains the nerve cells
which generate impjlses that travel along nerve fibres
and stimulate the muscles to contract.
Two groups of nerve cells are involved in the nerve path
from the brain to the muscle; the first or upper group is
situated, as said above, in the posterior part of the frontal
lobe, whence the efferent nerve fibres travel to the base of
the brain. When these fibres reach the lower part of the
brain, or medulla oblongata, they cross to the opposite
side, then run down in the spinal cord, and end here by
forming connections with the second or lower group of
motor cells situated in the spinal cord. The nervous path
is continued by efferent fibres arising in the motor cells
of the cord, which finally end in the muscle fibres in special
end organs called the " muscle plates." It is seen, there-
fore, that in the motor nervous path two groups of nerve
cells and their fibres are involved. The upper group of
motor nerve cells is situated in the frontal lobe of the brain,
while the lower is situated in the spinal cord.
For proper muscular action it is essential that these two
groups of nerve cells should be intact ; injury to nerve cells
in either of them results in paralysis of corresponding
muscles.
FIG. 34. — DIAGRAM SHOWING THE CONNECTIONS BETWEEN MUSCULAR
AND NERVOUS SYSTEMS.
A, Cerebral cortex ; B, motor cortex, containing the upper motor nerve
cell ; G, anterior horn cell of spinal cord (lower motor nerve cell) ;
D, posterior nerve root cell ; E, nerve cell in medulla ; F, nerve
cell in optic thalamus ; 0, motor sense area of cerebral cortex ;
M, muscle ; H , motor nerve-ending in muscle ; K, sensory nerve-
ending in muscle ; B, G, H, represents motor nervous path ;
K, D, E, F, G, represents the path along which muscular sensation is
carried in the nervous system.
£0 HYGIENE
There are also afferent nerve fibres running up from the
muscles and joints to the central nervous system. These
tell us of the condition and position of our muscles and
joints, and the integrity of these is essential for co-ordinated
muscular contraction.
Mu;cular Fatigue. — If the sciatic nerve is exposed in the
frog, as described above, and placed on two electrodes
attached to an induction coil and battery, the nerve will
receive a series of rapidly repeated electric shocks on
closing the circuit. These will be conducted to the muscles,
which will give correspondingly rapid contractions, and
this will go on for some time until the muscular response
gradually decreases, and finally there will be no muscular
contraction at all. Such a condition is called muscular
fatigue, and may be defined as a more or less complete loss
of irritability and contractility brought on by functional
activity.
The seat of exhaustion in a fatigued muscle is in the
nerve endings or in their connections with the contractile
substance of the muscle. This is proved by the fact that,
though a muscle will not contract wheii its nerve is stimu-
lated, it will respond when it is directly excited.
The site of fatigue when caused by voluntary muscular
contraction has not been definitely settled. Certain
experiments seem to prove that it is due to central changes,
and not entirely to changes in the muscles and nerves
themselves ; thus, electrical stimulation of a " tired "
muscle or of its nerve is readily responded to at a time when
a weight cannot be raised by voluntary contraction.
It has also been shown that the injection of the blood
of an animal exhausted by running or other muscular effort
into the circulation of a normal animal produces in the
latter all the symptoms of fatigue. It seems that certain
substances are produced in the muscles during activity,
and if these accumulate to a certain point they produce
the sense of fatigue. ' The products causing this action
are probably acid-reacting substances, such as sarcolactic
THE SKELETON AND MUSCULAR SYSTEM 51
acid ; thus, the muscle's own waste products serve to limit
its responsiveness to stimulation, forming a protective
mechanism that saves it from complete exhaustion.
Locomotion. — In walking, one leg — say the right — is
slightly bent at the knee, and planted down in front of the
other. The weight of the body is thrown on to this leg,
while the left leg, raised on to the toes by the action of the
calf muscles, forms a straight stiff rod. The left leg, by
giving a push to the ground, next throws the body for-
wards. Thereupon the right leg straightens up, while the
left, slightly bent at the knee, swings forward as a pen-
dulum, and comes down in front of the right. It is now
the turn of the right leg to push off, and of the left leg to
bear the weight of the body. The length and rapidity of
the step in walking will, of course, depend on the length
of the leg.
It is far more difficult to analyze the exact changes that
take place in running, but this has been done by taking
a succession of instantaneous photographs by means of a
cinematograph arrangement. Both feet are momentarily
off the ground during each step, and therefore much more
powerful contractions of the muscles are necessary to propel
the body forwards ; and this is brought about by the com-
bined action of the calf muscles and the extensors of the
thigh.
Postures and Attitudes. — Some writers state that bad
positions in writing, drawing, reading, and standing, are
common causes of deformity. It is doubtful whether these
factors are able to produce deformities, except when they
are combined with other conditions, such as bad nutrition,
rickets, etc.
If deformities are to be avoided, it is most important
that children should be properly fed and the muscles
brought into good tone by suitable exercises ; also such
attitudes and postures as tend to produce deformities
should be avoided.
The ideal sitting posture for the child while receiving
52 HYGIENE
instruction in school should be such that the force of
gravity would largely replace muscular exertion. The
child should sit in such a position that it would be in stahl*
equilibrium, though all the muscles of the body are at rest.
The body should be symmetrically placed, and the pelvis
resting equally on the seat of the desk ; the spinal column
must be erect, the head balanced so that the muscles of
the neck are at rest ; the thighs horizontal, and
hands resting upon them. It is very difficult to maintain
such a position for any length of time became of the lack
of support to the back; and since the legs of all child'
in the classes are not of equal length, it is impossible to
have thin ideal posture unless the height of the RCNT
adjusted for each pupil.
pn-iiui-- u i iii 1 1 involvi twittiiig "t i '••• l"-d\ xi,..ulii I '.-
avoided, because they may result in curvature of tin-
spine.
When seated, the children should be taught to sit up
straight, and not to bend the body forward, or slide down-
ward* on their oeat, so that they sit on their sacrum and
coccyx fajtoad of on their ischial tubcrosittes.
When the pupil sits with the body bent forward, there is
compression of the chest, and pwptt expansion during
inspiration is impossible ; the amount of oxygen absorbed
would be diminished, and this would have a bad effect on
all the activities of the body. The dorsal spinal curve
is increased, while the lumbar curve If reversed. The
anterior abdominal wall is folded, and the contents of the
abdomen are unduly pressed upon. When a child slips
forward on his seat equally bad results follow.
A very common posture taken by the child when writing
is to support the right arm and hand on the desk, while
the left arm hangs down unsupported. This tends to
produce curvature of the spine, with the convexity to the
right.
Writing produces fatigue readily in children, because it
is such a complicated muscular movement ; and many of
THE SKELETON AND MUSCULAR SYSTEM 53
the injurious postures assumed are the direct result of an
attempt to relieve this fatigue.
The best position for standing is when the chest is
thrown forward with the head well back, and the heels
placed slightly apart and opposite each other, so that the
body is symmetrically placed and the weight of the body
is equally divided between the two legs. Such position
cannot be maintained for long, because the circulation
in the legs is impeded when they are held in one position.
The force of gravity opposes the return of the blood, and
muscular movement is required to pump the blood up the
veins.
For longer periods the best position is when the trunk
is held as above, but one leg is placed in front of the other ;
the posterior one is held rigid, and supports the weight of
the body, while the anterior one is relaxed and the knee
slightly flexed. The position is varied from time to time,
so that the anterior leg is placed posteriorly and supports
the weight of the body, while the previously posterior leg
becomes anterior and is relaxed and rests.
Lateral Curvature of the Spine, or Scoliosis, arises in
several ways : (1) It is said to occur very rarely as a con-
genital affection, owing to deformity in the formation of
the vertebrae. (2) It may commence in young children as
the result of rickets, owing to softened condition of the
bones, and partly to irregular growth. (3) Any cause of
asymmetry of the body will give rise to scoliosis ; shortness
of one leg will cause tilting of the pelvis, and to compensate
for this a lateral curvature of the spine is produced.
(4) The most common form is the scoliosis of adolescents
due to excessive muscular fatigue, bad nutrition, and un-
hygienic surroundings, met with in young people about the
age of puberty.
The first sign is inequality in the level of the shoulders
or some awkwardness in the gait. Slight cases may be
treated at home, but children with marked deformity
should be sent to special schools for a course of educa-
54 HYGIENE
tional treatment by means of remedial exercises and
movements.
Angular Curvature of the Spine, or Pott's Disease. — This
is due to tuberculous disease of the vertebrae, originating
almost invariably in their bodies, which are more or less
destroyed, and leading to the so-called " angular cur-
vature."
The exact signs and symptoms will vary considerably in
different situations, but generally there are some symptoms
in common.
Pain is a constant and invariable accompaniment of the
disease, and in the early stages it can only be elicited by
careful examination. The pain is either local over the site
of the disease, or, by involvement of the sensory roots of
nerves, it may be referred to different regions — e.g., down
the legs, over the buttocks or abdomen.
Rigidity is present, due to muscular spasm at first, and
then to bony deformity.
Deformity arises from destruction of the vertebrae. The
disease process often results in abscess formation, which
may form tracks to various regions.
PHYSICAL TRAINING.
The educational legislation and administration of this
country during the last few years has been characterized
by the efforts made to improve and develop the physical
condition of the children in our elementary schools. These
arc certainly steps in the right direction, because a healthy
physique is the greatest asset a nation can possess. A
healthy body is absolutely necessary for the development
of an active intelligence and a sound character.
The muscular system plays a very important part in the
physiological processes in the body ; and if this system be
undeveloped, not only is the physical power of the individual
weakened, but the vital processes upon which life depends
are performed in a sluggish manner. In the sections on
THE SKELETON AND MUSCULAR SYSTEM 55
Physiology it is shown that the muscles are the main site
of the oxidative processes in the body, and muscuk r ton *
and contraction are the most important causative factors
in the venous return of blood to the heart. The proper
development of the musculature of the body can only be
attained by adequate physical exercises.
The Board of Education has paid great attention to
this subject, and has issued an excellent syllabus of
physical exercises suitable for children in elementary
schools.* It is the duty of every teacher to procure a
copy and make a careful study of it.
In the introductory chapter of the above syllabus, the
objects, effects, and general physiology, of muscular exercise
are very well explained, and we cannot do better than
quote here some of the facts recorded there, together with
some additions that seem necessary.
It is stated that the object of physical training is to
help in the production and maintenance of health in body
and mind.
It is pointed out that physical training has, or should
have, a twofold effect : on the one hand a physical effect,
and on the other a mental and moral effect, which for con-
venience may be termed " educational " hi the popular
sense. The direct results upon the health and physique
of the child may be described as the physical effect. " Exer-
cises, if rightly conducted, also have the effect, not less
important, of developing in the children a cheerful and
joyous spirit, together with the qualities of alertness,
decision, concentration, and perfect control of brain over
body. This is, in short, a discipline, and may be termed
the educational effect." These two elements are obviously
blended in varying degree in every suitable exercise, and,
according to circumstances, now the one aspect of the
exercise, now the other, is to be regarded as the more
important. The difference consists rather in the stage at
* "The Syllabus of Physical Exercises for Public Elementary
Schools," 1909(Wyraan and Sons).
56 HYGIENE
which, and the manner in which, the exercise is taken, than
in actual difference of movement."
Physical Effect. — This is considered under three head-
ings, according as the effect is (1) on the general nutri-
tion, (2) corrective, (3) developmental.
1. Effect on General Nutrition. — The exercises which
have the most beneficial influence on general nutrition are
those involving a large number of muscles. Such exercises
consist chiefly of massive movements, and are of two kinds
— general and special.
" General Massive Movements are those of the limbs and
trunk, which involve the whole bony and muscular
hire of the body, and quickly and powerfully affect both
respiration and the circulation. Types of such exercises
arc to be found in the natural play movements of children,
such as running, leaping, and skipping ; also in marching,
dancing, cycling, and games of all kinds. It is chiefly
through such movements, given a sufficient supply of
fresh air and suitable food, that the structure of the body
is built up during the growing period, and the artificial
conditions of school life make it of the first importance
that adequate provision should be made for such exercises."
" Among the Special Massive Movement* may be included
the various balance movements, shoulder exercises, and
lungs. These have a beneficial effect upon the nervous
system, and strengthen the control exercised by the nerve
centres over the muscles."
2. Corrective Effect. — " This term is used to denote the
remedy or adjustment of any obviously defective or in-
correct attitude or action of the body, or any of its parts.
Exercises employed for their corrective effect do not usually
involve the whole body, but the trunk or limbs tak«-n
separately, in order to encourage local development. "
3. The Developmental Effect. — " One of the ain
physical training is to promote the development of the
muscular system and the body as a whole, in order to
attain the highest possible degree of all-round plr
THE SKELETON AND MUSCULAR SYSTEM 57
fitness. Physical training has also an equally important
influence on the development and specialization of the
brain cells.
" There are in the brain certain ' centres,' or masses
of brain matter, which preside over co-ordinated move-
ments of all kinds. Thes3 centres begin to perform their
functions in early life, when the child learns to stand, to
walk, or to talk. As new movements are attempted, new
centres become active, certain nerve impulses become more
or less habitual, and thus new nerve paths are opened up
and established, and the connections between the centres
in different parts of the brain become increasingly well
defined and co-related. It has been found that, within
reasonable limits, the greater the scope of the physical
education, the more complex and highly specialized and
developed do these centres become.
" There should be no demand for accurate movements in
the infant school, and but little in the lower standards.
Jt is only in the upper school, with children from eleven
to fourteen years of age, that real precision and smartness
of execution should be required."
Educational Effect. — The educational effect is of great
importance, especially as the child grows older. Exer-
cises have not only a physical effect on the body, but also
a strong mental and moral influence, which is a powerful
agent in the formation and development of character. The
child learns to respond cheerfully and promptly to the
word of command, and thus unconsciously acquires habits
of discipline and order.
PHYSIOLOGY OF MUSCULAR WORK.
Effects of Exercise on the Muscular System. — In all living
tissues there is an adaptation of structure to function ;
hence, if the muscles of the body are called upon to do a
greater amount of work, their structure is adapted to per-
form such new duties. Muscles on being regularly and
suitably exercised become larger, stronger, and more
58 HYGIENE
capable of doing work. Muscular work increases the
chemical changes going on in the muscles, and a greater
amount of food and oxygen is used up.
Effects on Bones and Joints. — Physical training causes the
skeleton to become bigger and heavier. Joints become
more flexible and supple, as well as stronger, by exercise.
Effects on Heart and Circulation. — The heart beats more
quickly during muscular work, because a more rapid cir-
culation is necessary to meet the various demands of
muscular activity ; this is brought about by the nervous
impulses passing out of the brain having an effect on the
nerve cells which govern the rate of the heart-beat. The
products of muscular activity also affect the heart and
cause it to beat quicker.
The heart is a muscle, and resembles the skeletal muscles
in its response to work. Gradually increasing work with
good nutrition and periods of rest strengthen it. If ex-
cessive work be done when the heart muscle is untrained,
it may bo overstretched and injured ; such a damage is
far less easily repaired than in the case of skeletal muscle.
Muscular tone and contraction aid the return of blood
to the heart, and so help to maintain the circulation in the
veins and lymphatics.
Effects on Respiration. — Muscular work causes increased
absorption of oxygen and elimination of carbon dioxide.
In order to meet the greater demand for the supply of
oxygen and the removal of carbon dioxide, there is an
increased respiratory exchange and increased ventilation
of the lungs. All parts of the lungs are opened out and
well circulated with blood owing to the deep breathing.
Effects on the Temperature of the Body.— Muscular
exercise results in a greater formation of heat, and in
order to keep the temperature of the body constant the
heat loss must be correspondingly increased. There is
dilatation of the vessels of the skin, a greater amount of
blood reaches the surface of the body, which, results in
greater loss of heat from the skin. Further, the sweat
THE SKELETON AND MUSCULAR SYSTEM 59
glands are stimulated to activity, and the evaporation of
this moisture causes rapid cooling of the surface of the body.
There is also increased evaporation of water from the
surface of the lungs, resulting in greater loss of heat. In
spite of the far greater loss of heat, hard muscular exer-
cise may at the time raise the temperature of the body
one or two, or even three, degrees (Fahrenheit).
Effect on the Digestive System. — Muscular activity in-
volves greater oxidation of food in the muscles, and to keep
up a proper supply there must be an increased absorption
from the intestine. The functional activity of the diges-
tive tract is improved, the appetite is sharpened, and
digestion and absorption of food increased. The vigorous
movements of the diaphragm aid the circulation through
the liver and other abdominal organs. The metabolic
functions of the liver are greatly improved by exercise.
Effect on the Nervous System. — The developmental effect
on the brain centres has been referred to above. There is
a close connection between the nervous and muscular
systems, and physical training must result in an improve-
ment in the tone and condition of the nervous system.
The increased circulation of blood through the brain
brought about by exercise has a very beneficial effect.
Physical Condition of the Child and Physical Exercises. —
There are few children who do not benefit by physical
exercises of the right kind, when not excessive in amount ;
but in certain cases the demands may be too great on the
physique of the child, and a good deal of harm may be
done. Medical inspection of schools will do much to
obviate this.
The teacher should watch for certain signs during
physical exercises — namely, marked breathlessness, early
signs of general fatigue, pallor, fainting, and mouth
breathing. The frequency of the pulse is greatly increased
during hard exercise. On resting, the frequency ought to
lessen very rapidly. If the pulse remains frequent, it is a
sign cf overfatigue.
60 HYGIENE
Children showing any of the above signs should be sent
to the medical officer for examination.
Clothing. — Physical exercises can only be carried out
satisfactorily when suitable clothing and proper shoe* Mi
worn. At present, unfortunately, this is impossible in our
elementary schools, unless special provisions are made by
the local educational authority.
Open Air. — All exercises should be carried out in tin-
open air, for the cooling effect of the wind is very beneficial.
Games. — Physical exercises must not replace school
games. Playing-fields should be provided for every school,
and proper games should be organized for the children by
certain members of the teaching staff. The older boys
should play football, cricket, tennis, etc. These games un-
doubtedly improve the mental, moral, and physical con-
dition of the children.
The amount of physical exertion required by the games
should be graduated according to the -age and strength of
the child. This is done most satisfactorily by the co-opera-
tion of the teacher and the medical officer.
CHAPTER III
THE DIGESTIVE SYSTEM
Digestion is the means by which food is taken into the
organism and changed into a form ready for absorption.
In the simplest form of animals — the protozoa — food is
taken in by the organism throwing out a protrusion of its
protoplasm, and surrounding the particle of foodstuff.
After the particle of food is taken into the protoplasm, it
is acted upon by certain substances, and broken up into
simpler compounds, which are absorbed, and the waste
products are thrown out. In the unicellular animal no
one part of the organism is specialized for this work, but
as we ascend the animal kingdom there is greater and
greater division of labour, until in the higher animals
a very special part of the body is set aside for the taking
in of the food and its conversion into simpler and more
soluble substance, more suitable for absorption into the
blood-stream. This specialized part of the body is called
the " alimentary system."
We shall first describe the chemistry of the foodstuffs,
and then treat of the anatomy and physiology of the various
parts of the digestive system.
Chemistry of Foodstuffs. — The food of man may be
divided into three main classes — the proteins, fats, and
carbohydrates.
The Proteins are substances which contain carbon,
oxygen, hydrogen, and nitrogen, sometimes sulphur and
sometimes phosphorus. They are the most important
61
62 HYGIENE
group of substances, because without them no animal can
survive, as they are absolutely essential for the building
up of the tissues. Since during the processes of life a
certain amount of wear and tear of the tissues always takes
place, it is readily seen how important these substances
are to the organism.
The chief proteins that we eat are the vegetable protein
found in flour, oatmeal, peas, beans, and potatoes ; albu-
min and globulin, found in white of egg and blood-plasma ;
myosin and myogen, found in lean meat ; casein, found in
milk and cheese ; gelatin, obtained from bones and liga-
ments by boiling.
As they exist in Nature proteins are amorphous sub-
stances, but it is possible in the laboratory to change some
of them into a crystalline condition.
Some of the proteins are soluble in water (e.g., the
albumins), while others (e.g., the globulins) are insoluble
in water, but soluble in dilute salines. The solutions so
obtained are not true solutions, but simply a very fine
suspension of the particles of the protein in water ; hence,
when neutral salts are added to the solution, they cause an
aggregation of the particles of the protein, and result in
its precipitation. This serves as an important test for
protein ; when neutral salts are added to a solution of
protein, they cause precipitation of the protein, and the
amount of salt that is required to attain this result varies
for different proteins.
The more modern view held about the composition of
proteins is that they are made up of an aggregation of
simpler bodies, called " amino-acids." Proteins can be
readily broken up into amino-acids through the inter-
mediate products of proteoses and peptones. About
eighteen of these amino-acids have been definitely isolated
on breaking up various proteins. These amino-acids
undergo chemical reaction with various reagents, and hence
these serve as tests for proteins. We will mention two
of these tests here.
THE DIGESTIVE SYSTEM 63
1. Biuret Test, so called because it is given by a substance called
biuret, which is obtained by heating urea in a test-tube. When it is
applied for proteins, it is done in the following way : To a solution of
protein (e.g., solution of egg-white) add caustic soda solution, and then,
drop by drop, dilute copper sulphate solution (1 per cent.), mixing after
each addition : a violet colour appears.
2. Xanthoproteic Test. — Heat a little egg-white solution with con-
centrated nitric acid ; a yellow colour is formed ; cool, and add ammonia
or soda in excess : the colour changes to orange.
Fats. — Chemists tell us that bases and acids combine
together to form a new compound, and this new compound
is called a " salt "; e.g., sodium hydroxide (base) will com-
bine with sulphuric acid (acid) to form sodium sulphate.
The reaction can be stated thus :
2NaOH + H2S04 =Na2SO4 + 2H20.
When we study organic chemistry, we find there are
reactions comparable to the above, and one of these is the
combination of alcohols and acids.
Alcohols combine with acids to form a new compound,
called an " ester." Thus, ethyl alcohol combines with
acetic acid to form ethyl acetate :
C2H5OH + CH3COOH = CH3COOC2H5 + H2O
ethyl alcohol acetic acid ethyl acetate
Fats are esters, and therefore are a combination of
alcohol and acid. Animal and human fat is generally a
mechanical mixture of three esters. The alcohol present
in these esters is the same (namely, glycerine), but there
are three different acids — namely, stearic, palmitic, and
oleic acids. Hence animal and human fats are a mechanical
mixture of glycerine tristearate, glycerine trioleate, and
glycerine tripalmitate.
Animal fats are semisolid at body temperature. Fats are
insoluble in water, but soluble in ether, chloroform, and
hot alcohol. Another important physical property of fats is
their power to emulsify — that is, they are capable of being
broken up into very small globules. A natural form of
emulsion is milk. Fats are readily broken up into their
64 HYGIENE
components — namely, glycerine and fatty acids. When
treated with caustic potash or soda, they are split up into
glycerine and a soap ; and if the products of their reaction
are treated with sulphuric acid, the soaps are broken up.
with the formation of fatty acid and sodium sulphate, and
the free fatty acids float to the surface. Fats are an im-
portant group of foodstuffs, and before they are absorbed
they are broken by one of the digestive enzymes into
fatty acids and glycerine, and then resynthesized during
absorption.
Carbohydrates are compounds containing carbon, hydro-
gen, and oxygen. In this group must be included the
sugars, starches, dextrine, glycogen, and cellulose.
Sugars. — For our purpose in this book we may state that
the sugars are divided into two main classes — the simple
sugars, or monosaccharides ; and the more complicated,
the disaccharides.
MONOSACCHAKIDES. — There are three monosaccharides
which are of importance in human physiology — glucose,
fructose, and galactose.
They are all soluble in water, and are capable of reducing
the salts of heavy metals in alkaline solution. A large
number of tests that are used for sugars depend on the
latter property — e.g. :
Trommer's Test. — Add a few drops of copper sulphate to
* sugar solution, and then some caustic potash solution.
A blue solution of cupric hydrate is formed, which on
heating yields a yellowish-red precipitate of suboxide of
copper.
Fehling's Test, is only a modification of Trommer's
test. Folding's solution is made by mixing solutions
of copper sulphate, caustic potash, and Rochelle salt.
The object of the addition of Rochelle salt, which is
a crude form of sodium tartrate, is to keep the cupric
hydrate in solution. When a sugar solution is heated with
Fehling's solution, a yellowish-red precipitate of suboxide
of copper is formed.
THE DIGESTIVE SYSTEM 65
DISACCH ABIDES, OR COMPOUND SUGARS, are formed by
combination of two monosaccharide sugars, with the
elimination of a molecule of water. Three disaccharides
are important in human physiology — namely, maltose,
lactose, and cane-sugar.
Maltose is made up of two molecules of glucose, and these
are so combined that their reducing property still remains,
and hence maltose gives Trommer's and Fehling's tests.
Maltose is important physiologically as an intermediate
product of hydrolysis of starch, and industrially as an
intermediate product in the preparation of ethyl alcohol
from barley.
Lactose, or sugar of milk, is made up cf a molecule of
glucose combined with a molecule of galactose. It also
gives Trommer's and Fehling's test.
Cane-sugar, or sucrose, is a combination of glucose and
fructose, and these are so combined as to have no reducing
properties, and hence cane-sugar will not give a Trommer's
or Fehling's test. It will, after warming with dilute acids,
give Trommer's and Fehling's test, for the acid hydrolyzes
cane-sugar and splits it into glucose and fructose ;
Starches are the most important reserve forms of foodstuffs
in the vegetable kingdom They exist in plants as small
granules, made up of alternate layers of cellulose and starch.
Starch is insoluble in cold water, but dissolves into an
opalescent solution on heating. On the addition of iodine
solution starch gives an intense blue coloration, which
disappears on heating and reappears on cooling.
Starch can be hydrolyzed to glucose by means of dilute
acids or enzymes. In the human body starch must be
converted into glucose before it ean be absorbed by the
small intestine.
The Digestion of Food. — The foodstuffs which we have
discussed above cannot be absorbed as such from the
intestine, hence they must be broken up to simpler and
more soluble forms. The cleavage of these foodstuffs is
brought about by the action of certain specialized sub-
5
66 HYGIENE
stances, called " ferments " or " enzymes." These bodies
are formed in special tissues called " glands." The prod-
ucts of activity of a gland are called its " secretion." After
the food has been broken down to the simpler products,
these are carried through the living membrane of the intes-
tine into the bloodvessels and lymphatics present in the
intestinal wall. The process of taking the food into the
blood or lymphatic vessels is called " absorption."
After absorption the food is carried in the blood-stream
to the tissues, and now serves to nourish all the body.
" Metabolism " signifies the use of the food by the tissues,
and the chemical changes it undergoes therein. Oxygen
is carried by the blood to the tissues from the lungs, and
there oxidizes the food, liberating its chemical energy ; on
this life is sustained. After this process of oxidation tlicro
are left the waste products, and the body gets rid of these
substances by a process of excretion. Hence in digestion
and metabolism there are three great processes, called
" secretion," " absorption," and " excretion."
The processes of secretion, absorption, and excretion,
are distinguished from one another only by their object or
physiological function, and not by anything intrinsically
different in their nature or in the mechanism by which
these processes are carried out in the body.
Secretion. — The purpose of secretion is to prepare an
active substance in solution for use in assisting a process
which is of service to the organism in some other part
(e.g., digestive secretion) or a secretion of a substance \\ lii< li
Was a guiding influence upon chemical change in other
tissues, and hence affects the state of activity of those
tissues (e.g., internal secretion : adrenalin, secretin, etc. ;
vide pp. 102-105) ; or a secretion which acts by mechan-
ical means (e.g., secretion of lachrymal glands, mucous
secretions of mucous membranes, and also secretions of
serous membranes).
Absorption is for the purpose of taking up for the servi< e
of the body generally, and of the absorbing cells, the
THE DIGESTIVE SYSTEM 67
materials in solution which have been prepared and modified
by the secretions.
Excretion is for the purpose of removing from the body
materials which have been passed through, or been formed
in the cycle of metabolism in the body, and have become
waste products for which the body has no further use.
In addition, the purpose of excretion is to maintain in
normal amount and concentration in the circulating fluid
of the body — the blood — those products which are of
service ; for in abnormal concentrations these useful bodies
become as injurious to the living cells as effete products of
metabolism or foreign substances of actively poisonous
nature.
Ferments or Enzymes. — It would be advisable at this
stage to learn some of the general properties of ferments
or enzymes, because the chemical changes wrought in the
food as it passes along the alimentary canal are due to the
secretions of various glands which line its cavities, which pour
their juices into it through special ducts. These secretions
owe their power for the most part to the presence of these
substances called " enzymes " or " ferments." Enzymes
or ferments are bodies capable of producing certain changes
in some substances without undergoing any change them-
selves. Enzymes are protein-like substances, and are
generally soluble in salt solutions, water, or glycerine.
They are destroyed by heat (80 °C.), and their action is in-
hibited by cold. They all have an optimum temperature —
i.e., temperature at which they work best — and for those
which are present in the body this is the body temperature.
Ferments are precipitated by alcohol, and carried down by
flocculent precipitates — e.g., calcium phosphate. Their
action is always incomplete ; e.g., yeast cannot convert a
certain weight of glucose entirely to carbon dioxide and
alcohol, nor can pepsin hydrolyze completely a certain
weight of protein. Their action is always inhibited by the
products of their reactions — e.g.. when yeast acts on
glucose. If the amount of alcohol rises above 14 per cent.,
68 HYGIENE
the action stops ; then, if some of the alcohol be removed,
the action will go on until the strength of alcohol again
rises to 14 per cent. Enzymes are most often secreted
in an inactive form, called the " zymogen," then acted upon
by a substance called the " activator," or " kinase," and
changed to the active form.
Various theories have been formed as to the mode of
action of ferments, but we are still rather far from under-
standing the exact nature of enzyme actions.
Ferments are* classified according to the nature of the
chemical changes which they bring about — e.g. :
1. ProUolytic or protein -splitting ferment* are those which hydrolyze
proteins, breaking them up into proteOMt, peptones, and amino-actds
— e.g. , pepsin of the gastric juice, trypsin of the pancreatic juice, and
c rcpsin of the intestinal secretion.
2. Atnylolytic or starch-splitting ferment* are those which break up
starch, converting it into glucose — e.g., ptyalin of the saliva, amylopsis
of the pancreatic juice.
3. Lipolytic or fat-splitting ferment* are those which split fats into
glycerine and fatty acids — e.g., steapsin of pancreatic juice, and Upases
present in the liver and connective tissue and other parts of the body.
4. Sugar-splitting enzymes are those which break up sugars :
(a) Those which change disaccharidcs to monosaccharides ; e.g..
maltose converts maltose to glucose, invertase changes
cane-sugar to a mixture of glucose and fructose.
(a) Those which split up the monosaccharides.
5. Congulative enzymes arc those which act on certain substances,
changing them from a soluble to an insoluble form ; e.g., thrombin
changes soluble Hbrinogen to insoluble fibrin, and brings about the
coagulation of biood ; rcnnin changes the soluble calcium compound of
caseanogen to the insoluble calcium compound of casein, and hence
brings about the dotting of milk.
(i. Oxidizing enzymes, or oxidasts, are those which bring about the
oxidation of substances in the tissues.
PHYSIOLOGY OF THE MOUTH.
Anatomy. — The alimentary canal is a long muscular
tube lined by a mucous membrane. It is about 30 feet
in length. Its upper expanded portion is called the
THE DIGESTIVE SYSTEM
69
" mouth," and is specially adapted for the reception and
mastication of food. When the mouth is examined, we
can distinguish in it various parts — the aperture of the
mouth, the vestibule, and the cavity of the mouth proper.
The aperture of the mouth is the upper or anterior open-
ing of the alimentary canal, and is bounded above and
FIG. 35. — DIAGRAM SHOWING STRUCTURES SEEN WHEN A LONGITUDINAL
SECTION is MADE THROUGH THE MOUTH, TONGUE, NOSE, AND
PHARYNX.
A, Cavity of the nose ; B, cavity of the mouth ; 0, tongue ; D, lower
jaw"; E, base of skull ; F, vertebral column ; G, larynx ; H, palate ;
K, naso-pharynx ; L, oral pharnyx ; M , opening of Eustachian
tube.
below by the corresponding lips, which by their junction
at the sides form the angles of the mouth.
The vestibule is a slit-like space bounded anteriorly and
externally by the lips and cheeks, posteriorly and internally
70 HYGIENE
by the dental arches and gums. Its roof is formed by the
reflection of the mucous membrane from the deep surface
cf the upper lip and upper part of the cheeks on to the
gum of the upper jaw. The floor is formed by the reflec-
tion cf the mucous membrane covering the deep surface
of the lower lip and lower parts of the cheek on to the gum
of the lower jaw. You should ascertain the boundaries
of the vestibule by placing the finger in the mouth between
the lips and teeth and pushing it upwards and downwards.
Lips are composed of a stratum of muscular tissue covered
superficially by skin, and on their deeper surface by a
mucous membrane.
Cheeks. — The cheeks resemble the lips in structure, being
formed of corresponding layers.
Cavity of the Mouth Proper. — This, is the space situated
within the dental arches, which with the gums separate
it from the vestibule.
Posteriorly the cavity of the mouth opens into the throat,
or pharynx, through an aperture bounded by two folds
of mucous membrane containing muscular tissue. These
Me called the " pillars of the fauces."
The roof is formed by the hard palate and by the anterior
part of the soft palate.
The floor is formed by the tongue. When the tip and
marginal portions of the tongue are raised, a limited sur
face, formed of mucous membrane and muscular tissue, is
exposed, and is called by anatomists the " floor of the
mouth. "
Gums. — These are made up of firm connective tissue
covered by a mucous membrane. They form the outer
covering of the bony ridges carrying the teeth in the- upper
and lower jaws. They are continuous on the outer surface
with the mucous membrane lining the floor and roof of the
vestibule, and on the inner surface with the mucous mem-
brane covering the floor of the mouth and the hard palate.
The palate is the structure which separates the mouth
from the cavity of the nose ; it projects posteriorly into
THE DIGESTIVE SYSTEM 71
the pharynx, incompletely dividing that cavity into an
upper nasal and lower oral portion. The anterior half is
composed of bone covered by a mucous membrane on each
side ; this is called the " hard palate." The posterior part is
formed of muscular tissue covered by a mucous membrane,
and is called the " soft palate." The soft palate ends
posteriorly in a conical projection, called the uvula.
The tongue is an organ composed chiefly of muscular
tissue covered by a mucous membrane. It occupies the
floor of the mouth, and forms part of the anterior wall of
the pharynx.
The muscular part of the tongue is made of voluntary
muscular tissue, the fibres of which go in various definite
directions. The mucous membrane is made of stratified
epithelium ; it is also covered with numerous papillae,
which give the tongue its most characteristic appearance.
The papillae of the tongue are formed by projections of
the upper part of the mucous membrane, covered by thick
caps of epithelium. Some of the papillae are furnished with
taste-buds (vide Special Senses).
The teeth are specialized portions of the mucous mem
brane of the mouth. Each tooth may be looked upon as a
papilla of such mucous membrane undergone calcification.
Just as the mucous membrane of the mouth is made up of
two portions — namely, a substratum of connective tissue
and a superficial layer of epithelium — so each tooth is also
composed of two layers — namely, dentine and enamel.
The dentine is modified connective tissue, and forms
the greater part of each tooth. The enamel is derived from
the epithelial layer, and forms a cap for the portion of
the tooth that lies above the gum. Another special form
of hard tissue, called the " cement," or " crusta petrosa,"
surrounds the portion of a tooth that lies in the socket.
The enamel is the hardest and densest substance in the
body, and is made up almost entirely of phosphate and
carbonate of lime. Dentine is made up of a large amount
of calcium salts combined with organic matter.
72 HYGIENE
Anatomists designate various parts to each tooth. The
crown is the portion of the tooth that lies above the gum.
This varies in shape in different teeth. In the anterior
teeth — namely, the incisors and canines — this portion is
shaped like the edge of a chisel, while the grinding surface
of all the other teeth bears either two or three cusps, or
tubercles. Those which have two cusps are called the
" bicuspids " or " premolars," while those which have three
cusps are called " tricuspids " or " molars."
The neck of a tooth is the portion that comes in contact
with the gum.
The root is the part of a tooth which lies in the bony
socket of the upper and lower jaws. In the incisor, canine,
and bicuspid teeth the root is a single process, while in the
tricuspids the root is made up of two or three processes.
When a longitudinal section is made of a tooth, its various
parts can be easily recognized and studied. The crown
will be seen to be made up of a superficial portion of enamel,
and a deeper part composed of dentine. The enamel will
be seen to end at the site where the gum comes in contact
with the teeth. The neck is made up of dentine with an
outer layer of "cement substance with which the gums come
in contact. The root is made up of dentine with an outer
covering of cement, or crusta petrosa, which is attached to
the bony socket by a vascular layer of connective tissue.
In the centre of each tooth there is a cavity, called tho
pulp cavity. It contains connective tissue, bloodvessels,
and nerves, all the contents being termed the tooth pulp.
The pulp cavity extends down to the root, whether it is
single or made up of two or three fangs. It finally ter-
minates in the small foramina at the apices of the roots,
through which nerves and bloodvessels enter the pulp
cavity. Nourishment is carried to the dentine along small
branching canals which radiate through it from the pulp
cavity.
The human subject is provided with two sets of tertli.
which make their appearance at different periods of life.
THE DIGESTIVE SYSTEM
73
Those of the first set appear in childhood, and are called
the " temporary," " deciduous," or " milk " teeth. Those
of the second set, which also appear at an early period,
continue until old age, and are named " permanent."
The temporary teeth are twenty in number : four in-
cisors, two canines, and four molars, in each jaw.
The permanent teeth are thirty-two in number : four
incisors (two central and two
lateral), two canines, four bicus-
pids, and six molars, in each jaw.
In each half of a jaw the teeth are
arranged in the following manner
from before backwards — central
incisor, lateral incisor, canine,
two premolars, and three molars.
The salivary glands are six in
number, three on each side, and
these are called the "parotid,"
" submaxillary," and " sublin-
gual."
The parotid gland is situated
in a deep recess at the side of the
head, below and in front of the
ear. Its secretion is carried to
the mouth by a duct, called
" Stenson's duct." It passes
superficially to the masseter
muscle, and then pierces the
mucous membrane of the mouth,
where it opens opposite the second
upper molar tooth.
The submaxillary gland is placed just below and under
cover of the angle of the lower jaw.
The secretion of the submaxillary gland is carried to the
mouth by means of Wharton's duct, which opens on the
floor of the mouth on each side of the frenum of the
tongue.
FIG. 36. — DIAGRAM SHOWING
THE STRUCTURE OF A
TOOTH : (LONGITUDINAL
SECTION).
A, Enamel ; B, dentine ;
C, pulp cavity ; D, gum ;
E, root membrane;
F, bony socket.
74
HYGIENE
The sublingual gland lies on the floor of the mouth, on
each side of the frenum linguae, which is a ridge of mucous
membrane seen on the under surface of the tongue. The
secretion of the sublinpual gland is carried to the mouth
c
Fio. 37.— DIAGRAM SHOWING SOME IMPORTANT STRUCTURES w A
LATERAL DISSECTION or THE LOWER PART OP THE FACE AND
UPPER PART OF NECK.
A, Mouth cavity ; B. teeth of upper JAW ; C. tongue ; D, parotid salivary
gland ; K. submaxillary salivary gland ; F, sublingual salivary
gland ; G, carotid artery.
by a number of ducts which open on each side of the
frenum linguae, and these are called the " ducts of Rivinus."
Composition of Saliva. — Saliva is a watery, alkaline
fluid containing inorganic and organic constituents. The
inorganic substances present are various salts — e.g., sodium
THE DIGESTIVE SYSTEM
75
chloride, sodium carbonate, calcium phosphate, magnesium
phosphate, and calcium carbonate. The organic substances
are mucin, a protein of the nature of a globulin, potassium
sulphocyanide, and ptyalin.
The secretion of the parotid gland is very watery, and
contains a good percentage of inorganic salts, but is poor
in organic constituents. The secretion of the submaxillary
and sublingual glands is thick and viscid, being rich in
organic substances. The presence of the above substances
FIG. 38. — DIAGRAM SHOWING MICROSCOPIC STRUCTURE or SEROUS
SALIVARY GLAND (I.) AND Mucous SALIVARY GLAND (II. J.
in saliva can be easily demonstrated. ^The salts can be
identified by the ordinary tests used in inorganic analysis.
Mucin is a slimy, viscid substance, and gives various protein
tests ; it is also precipitated by acetic acid, and is insoluble
in excess of that acid. Mucin acts as a lubricant to the
bolus of foo*d.
Pytalin is the only ferment present in saliva ; its action
is to convert starch into maltose. This can be easily
proved by making a solution of starch in boiling water,
allowing it to cool, and then test a little of it with iodine,
76 HYGIENE
when an intense blue coloration will be produced. Then
some of the starch solution is placed hi the mouth and held
there for a minute ; it is then returned to a test-tube, and
the iodine test again applied, when no blue colour would be
produced. If another portion of the starch that has been
held in the mouth be tested with Trommer's solution, a
precipitate of cuprous oxide would be produced on heating,
showing the presence of a reducing sugar.
The saliva has several important functions. It hag a
digestive enzyme which acts on starches, and hence it
helps in the digestion of this class of foodstuffs. It moistens
the food, and when a bolus has been formed the mucin
forms a slimy covering to it, and in this way saliva helps
mastication and swallowing. Saliva is also protect!
because, if any irritant — e.g., dilute acetic acid or can
potash — is placed in the mouth, it reflexly causes a great
secretion of saliva, which dilutes the irritating substance,
and therefore Intmnn its corrosive action.
Hygiene of the Mouth. — It is very important to keep the
mouth and teeth clean, because various micro-organisms
thrive readily in the mouth. They become mixed with tin-
food and are swallowed ; the poisons which they produce
are absorb, d into the body tissues, and give rue to serious
results. Anaemia may be caused by bad teeth, and there
is a fatal form of anaemia which may probably arise from
this infection from the mouth. Very serious joint affec-
tions may have the same cause. Indigestion, and possiMy
appendicitis, may be results of bad teeth.
The oaueee of decay of teeth are predisposing and deter-
mining. Heredity may play a part, because some persons
are, unfortunately, provided by Nature with a weak set
of teeth.
Malnutrition from wrong feeding is a very important
predisposing cause to dental caries ; this is most important
in the poorer classes of the community. The eating of
sweets may be a predisposing cause.
An acute illness may arrest the development of the teeth.
THE DIGESTIVE SYSTEM
77
The determining cause is the action of micro-organisms,
which produce an acid fermentation of food particles
between the teeth. Decay of the teeth can be prevented
by regular and thorough '
cleansing of the teeth
and mouth. The meals A •*
should be regular, and
no food eaten between
meals. The eating of
fruit, like an apple, at the
end of a meal will excite
the flow of saliva and
clean the mouth. Sweet,
sticky substances which
cling to the teeth should
not be eaten last. The
teeth should be cleansed
every night by a stiff
brush and water. Some
simple tooth - powder
should be used ; car-
bonate of soda or pow-
dered borax will serve
very well.
The Pharynx and Gullet.
—The pharynx is the part
of the alimentary canal
which lies behind, and
communicates with the
mouth, the larynx, and
FIG. 39. — DIAGRAM SHOWING MICRO-
SCOPIC STRUCTURE OF THE WALLS
OF THE (ESOPHAGUS.
A, Mucous membrane formed of strati-
fied epithelium ; B, submucous layer
made up of connective tissue, and
containing a few mucous glands ;
C, circular muscular coat ; D, longi-
tudinal muscular coat.
cavities of the nose. It
is a passage for air and food ; the former is carried down-
wards along the windpipe to the lungs, and the latter
along the oesophagus to the stomach.
The oesophagus, or gullet, is the part of the digestive canal
whioh communicates with the pharynx above and the
78
HYGIENE
stomach below. It extends from the termination of the
pharynx to the cardiac orifice of the stomach.
The function of the gullet is to carry the food from the
mouth into the stomach. This is done by the process Mf
swallowing, or deglutition. The food, having been broken
up by the teeth and mixed with saliva, is gathered up by
the tongue into a mass, or bolus, and forced between the
pillars of the fauces into the
pharynx. At the same moment
the larynx is drawn upwards, so
that the epiglottis covers its upper
opening, and respiration for a short
time ceases, and thus the food is
prevented from entering the larynx
and windpipe. The muscles at the
floor of the mouth then contract
and force the tongue backwards,
which pushes the food before it into
the pharynx. When the food enters
the pharynx, the muscles of this
tube contract and surround the
bolus closely. The contraction of the
pillars of the fauces and elevation of
the soft palate prevent the regur-
gi tat ion of the bolus to the nose
or mouth, and therefore it is forced
along the gullet to the stomach.
Throughout the alimentary
canal food is moved along by
a sp~cicl form of movement of the digestive tube, and
this is called " peristalsis "; it is a complex co-ordination
of contraction and relaxation, so that above the bolus there
is always contraction, and below it there is relaxation.
Wherever in the body we find such a co-ordination of
movements, they are found to be under the influence of
certain groups of nerve cells. Those for the process of
swallowing are situated in the central nervous system, or,
Fio. 40.— DIAGRAM SHOW-
ING THE MECHANISM OF
PERISTALSIS.
I., Diagrammatic repre-
sentation of bolus of
food in the alimentary
canal; 1 1., diagrammatic
representation of a peri-
staltic wave. There is
constriction above and
dilatation below thy
bolus.
THE DIGESTIVE SYSTEM 79
to locate them more exactly, in the medulla oblongata of
the brain. This is proved by cutting the nervous con-
nection— namely, the vagi nerves — between the central
nervous system and the oesophagus, when all swallowing
movements will be stopped entirely. The act of swallow-
ing is therefore brought about by a reflex action. The
sensory nerves, stimulated by the presence of food, carry
messages from the mouth and throat to the medulla
oblongata, and there excite the motor nerve cells, which
form impulses that cause the muscles of the pharynx and
gullet to contract co-ordinately.
PHYSIOLOGY OF THE STOMACH.
Anatomy. — The stomach is the dilated portion of the
alimentary canal as soon as it enters the abdominal cavity.
Its exact shape varies from time to time, according to the
amount of food present and its relative position to sur-
rounding organs. Anatomists generally describe it as
being an irregularly pyriform - shaped structure. The
broad portion is called the " cardia," and is directed back-
wards and to the left ; while the narrow portion is called
the " pylorus," and passess to the right to join the duo-
denum, or first portion of the small intestine. The stomach
has two surfaces, superior and inferior ; the former comes
in contact with the diaphragm and under-surface of the left
pr.rtion of the liver, and the latter lies on a portion of the
diaphragm, left kidney, pancreas, and other important
neighbouring organs.
The lesser curvature of the stomach is directed towards
the liver, and the greater curvature is directed downwards
and to the left. The stomach has two orifices : the cardiac
orifice, by which it communicates with the oesophagus ; and
the pyloric orifice, through which it communicates with the
small intestine.
Structure of the Stomach. — The stomach wall is composed
of four coats — namely, from without inwards : (1) Peri-
toneal ; (2) muscular ; (3) submucous ; (4) mucous.
80 HYGIENE
The peritoneal or serous coat is made up of pavement
epithelium lying on a basement membrane. This coat
gives the outer surface of the stomach its smooth and
glistening appearance.
The muscular coat is composed of involuntary muscle.
The fibres are disposed of in three incomplete layers — an
external or longitudinal, a middle or circular, and an
internal or oblique. In the region of the pyloric orifice
the circular layer becomes much thickened, and forms the
pyloric sphincter.
The submucous coat is a layer of strong and loose con-
Fio. 41.— DIAGRAM SHOWING VARIOUS ANATOMICAL PARTS OF THI
STOMACH.
A. Fund us ; H. cardia ; C. pyloric portion.
nective tissue, which connects the muscular and mucous
coats. Bloodvessels, nerves, and lymphatics, ramify in
this layer.
The mucous coat of the stomach is a soft thick layer.
It is lined by columnar non-ciliated epithelial cells, and con-
tains a large number of glands, which form the secretion
of the stomach called the " gastric juice." On examining
the inner surface of the stomach with a lens, a large number
of small pits will be seen ; these are depressions of the
mucous membrane, and are lined by the same kind of cells
as those which cover the general inner surface of the
THE DIGESTIVE SYSTEM
81
FIG. 42. — DIAGRAM SHOWING HISTOLOGICAL STRUCTURE OP THE WALL
OF THE STOMACH.
A, Mucous coat, lined on the inner surface by columnar non-ciliated
epithelium, and containing gastric glands, and their ducts supported
by connective tissue ; B, muscularis mucosae ; C, submucous coat
made up of connective tissue, and containing a few mucous
glands ; D, circular muscular coat ; E, longitudinal muscular coat ;
F, columnar non-ciliated epithelium ; 0, duct of gastric glands ;
H, gastric glands,
82 HYGIENE
stomach. They form the ducts of the glands, and *hen a
microscopic section is studied, one to four small tubular
glands will be seen to open into each duct. In the spaces
between the glands and the ducte there is connective
tissue, containing a number of lymphocytes, or white
blood-cells.
The gastric glands are small tubules, and are formed of a
layer of secreting cells lying on a basement membrane.
These cells are of two kinds : (a) The chief or pepsin cells
are cubical in shape and granular in appearance ; these form
the ferments that are present in the gastric juice. (6) The
oxyntic or parietal cells are rounded in shape, and have
acid properties ; they secrete the hydrochloric acid present
in the gastric juice. The columnar lining, the general
surface, and ducts, of the stomach secrete mucus.
Bloodvessels of the Stomach. — The arteries of the stomach
are all derived ultimately from the cceliac axis, a branch of
the aorta, as soon as it enters the abdominal cavity.
The veins follow the same course as the arteries, and
finally all drain to the portal vein. The glands are sur-
rounded with a close network of capillaries.
Nerves of the Stomach. — The stomach has two nerve-
supplies : (a) Fibres which are connected with cells in the
central nervous system : these run in both vagi nerves,
sometimes called the " pneumogastrics "; (6) fibres con-
nected with cells in the sympathetic system : these come
from the solar plexus in the abdomen, and run in the
sheath of the bloodvessels.
The Gastric Juice. — The digestive secretion of the glands
of the stomach is called the " gastric juice,*' and the
following are its most important constituents : Water,
salts (chiefly chlorides of sodium, potassium, magnesium,
and calcium), hydrochloric acid, pepsin, and rennin.
Activity of the Gastric Glands. — The gastric juice is not
secreted continuously, except in animals, such as the rabbit,
whose stomachs are never empty. There are two methods
by which the gastric glands are stimulated to activity :
THE DIGESTIVE SYSTEM 83
The idea or sight of food, and the tasting and mastication
of it, act as a stimulus to the gastric glands. This is done
reflexly through the nerves of special sense and the vagi.
The second mode of stimulation is by the direct action of
the food on the gastric mucous membrane, and this is
due to the formation of a chemical substance — a hormone,
or messenger — which is absorbed into the blood-stream,
and acts as a stimulus to the gastric glands.
Chemistry of the Gastric Juice. — The hydrochloric acid
is present in the free state, and is formed in certain special
cells of the cardiac portion of the stomach. It forms an
acid medium for the pepsin to act in. Pepsin is a pro-
teolytic enzyme, splitting up the proteins of the food into
proteoses and peptones, and, if continued long enough, into
amino-acids.
Rennin is a ferment present in gastric juice, which causes
the coagulation of milk. It acts on caseinogen, a protein
in milk, converting it into casein, and this combines with
calcium to form calcium caseinate, which constitutes the
clot.
A fat-spliUng ferment, or lipase, is said to be present in
the gastric juice. This breaks up fat into fatty acids and
glycerine.
Changes undergone by the Food in the Stomach. — When
the food, which has been broken up by the teeth and
mixed with alkaline saliva, reaches the stomach, the
ptyalin ferment continues to act upon the starch for
some little time. The food which entered the stomach
first is in contact with the stomach wall, and absorbs
the gastric juice ; while the food which entered last lies
in the middle, and is acted on by the saliva. As soon as
the gastric juice is secreted in sufficient amount to make
the food acid, the ptyalin is destroyed and its action
stopped.
The starchy constituents of food are therefore hydrolyzed
in the stomach by action of the ptyalin of the saliva.
The proteins of food are digested by the action of pepsin.
84 HYGIENE
The fate of the food are melted by the heat of the stomach,
and hydrolyzed to a certain extent by its lipase.
Absorption in the Stomach. — It is doubtful how much of
the food is absorbed from the stomach. It is possible that
there may be absorption of the following substances : Salts,
sugars, and dextrins, that may have been formed by the
action of saliva on starches of the food, or that may have
been eaten as such ; the proteoses and peptones formed as
the result of digestion of proteins in the stomach itself.
There is also some evidence that certain drugs — e.g., alcohol
— are absorbed from the stomach. It was formerly
assumed that the stomach absorbs easily such things as
water, salts, sugars, and peptones. Experimental work
performed under conditions as nearly normal as possible
tends to prove that absorption does not take place readily
in the stomach— certainly nothing like so easily as in the
intestine.
Movements of the Stomach.— It can be readily proved
that the stomach exhibits certain definite muscular move-
ments. This can bo seen in animals, by killing them and
opening the abdomen quickly and examining the stomach.
In man, under certain diieMad conditions, when there is
obstruction at the pyloric orifice, the movements of the
stomach are exaggerated, and can be seen through the
abdominal wall.
The muscular part of the stomach is made of involuntary
or unstriped muscle ; hence the movements are not under
the control of the will, as are movements of the skeletal
or striped muscle. Even when the stomach is cut off from
all connection with the central nervous system the move-
ments still continue ; hence the contractions of the stomach
wall have their origin in the stomach itself. There are
networks of nerve fibres and cells in the coats of the stomach
which maintain its movements. The nerves which supply
the stomach may reinforce or check these movements.
The stomach may be divided anatomically and func-
tionally into two parts — the fund us and the pylorus. The
THE DIGESTIVE SYSTEM 85
fundus serves as a receptacle for the food, and its move-
ment is peculiarly adapted to its function ; that is, during
the taking in of food it gradually dilates, and as digestion
goes on it tonically contracts upon its contents, and pushes
them towards the pylorus.
In the pyloric portion the food is further broken up and
mixed thoroughly with the gastric juice, and here we have
a series of waves of contraction, which start about the
junction of the pylorus and fundus and pass towards the
pyloric orifice. The effect of these waves is to force the
food, which has been digested by the gastric juice and
detached from the surface of the mass of food in the fundus,
towards the pylorus. The pyloric sphincter remaining
closed, the food cannot escape, and therefore is squeezed
back, forming an axial reflux stream towards the fundus.
The opening and closing of the pyloric orifice is regulated
by the local nervous mechanism, and the adequate stimulus
for its opening is a certain consistency and a certain acidity
of the contents of the stomach. Acidity on the stomach
side of the pyloric sphincter makes it open, while acidity
on the duodenal side makes it shut. Thus the acid chyme
passes slowly into the intestine in a succession of squirts.
When the food has passed from the stomach to the small
intestine, it then comes in contact with a series of alkaline
digestive secretions. These neutralize the acid chyme.
The pancreatic juice comes from the pancreas, the bile
from the liver, and the intestinal juice is formed in the
glands of the small intestine. We shall have to deal
separately with these three secretions.
PHYSIOLOGY OF THE PANCREAS.
Anatomy of the Pancreas. — The pancreas is an elongated
glandular structure which lies transversely on the posterior
abdominal wall. Its right end, or head, rests in the con-
cavity of the first portion of the small intestine, which is
called the " duodenum," and its left end, or tail, touches
the spleen, an organ on the left side of the upper part of the
86
HYGIENE
abdominal cavity. The intervening part, or body, lies in
front of the great vessels of the abdomen, and behind the
stomach and intestines.
Histology of the Pancreas. — The pancreas is made up of
a large number of branching tubes ending in dilatations
Fio. 43.— ABDOMINAL VISCERA DISPLAYED so AS TO SHOW THE PORTAL
VEIN CARRYING THE BLOOD FROM THE VlSCERA TO THE LlVER.
/., Liver; gt>., gall-bladder; ft., stomach; du.. duodenum. These have
been divided from each other, p.. Pancreas ; «p.. spleen ; ac.
cdt largo intestine. The bile - duct is shown sending off a side*
branch to the gall-bladder on its way to the duodenum.
called "alveoli," which are lined by secretory cells. It
resembles the salivary glands in its general structure, but
its alveoli are more tubular and elongated in shape ; the
connective tissue is looser in character, and small groups
of epithelioid cells are distributed amongst the alveoli,
and are called the " islets of Langerhans."
THE DIGESTIVE SYSTEM
87
Pancreatic Juice. — The pancreatic juice is a colourless
alkaline fluid. It contains a little protein, salts, and fer-
ments. The chief salt is sodium carbonate, which renders
the juice alkaline. The ferments present are trypsin, which
breaks up protein ; amylopsin, which converts starch to
maltose ; steapsin, which hydrolyzes fats to fatty acids and
glycerine ; and in some animals there is a milk-curdling
B
FIG. 44.— DIAGRAM SHOWING HISTOLOGICAL STRUCTURE OP PANCREAS.
A, Pancreatic alveoli ; B, connective tissue ; 0, islets of Langerhans.
ferment. All these ferments will only act in the presence
of dilute alkali.
Hence we may tabulate the composition of pancreatic
juice as follows :
... 97 '6 per cent.
Water
Inorganic salts
Organic solids
0-6
1-8
C Sodium chloride.
-| Sodium carbonate.
v Potassium chloride, etc.
Trypsin.
Amylopsin.
Steapsin.
Milk -curdling ferment.
Traces of other sub-
stances.
Mechanism of Secretion in the Pancreas. — Pancreatic
juice does not flow continuously into the small intestine,
88 HYGIENE
but only at certain definite intervals. It was noticed, by
experimentation in animals, that the flow of pancreatic
juice was always greatest about three hours after the
taking of food, and this coincides with the time at which
there is the greatest flow of chyme from the stomach to
the duodenum ; hence physiologists thought that there was
some association between these two phenomena.
The question arose, What constituent of the chyme acted
as the requisite stimulus to the pancreas ? It was easily
proved that it was the acid present in the gastric contents
that acted as the adequate stimulus to the secretory
activity of the pancreas.
The next question to be answered was, How did the acid
act ? The first theory regarding its mode of action was
that the acid stimulated certain nerve endings in the mucous
membrane of the small intestine, nerve impulses passed
from it to the central nervous system, and here impulses
were generated that passed back to the pancreas and
excited it to activity. For such a process to take place,
all the nervous connections between the pancreas, small
intestine, and the central nervous system, should be intact.
It was shown that, if a loop of the intestine was entirely
devoid of all nerve connections, the introduction of acid
into this loop still caused a secretion of pancreatic juice ;
and, further, the introduction of acid directly into the
blood-stream through the jugular vein did not excite a
secretion. The only difference was that in the first case
the acid comes into contact with the mucous membrane
of the loop of intestine. It was further proved that, on
treating the mucous membrane of the upper part of the
small intestine of any animal with hydrochloric acid, and
filtering, the injection of the filtrate into the jugular vein
of another animal caused a profuse secretion of the pan-
creas. Hence here we have a chemical mode of stimula-
tion : the hydrochloric acid of the gastric juice acts on the
mucous membrane of the upper part of the small intes-
tine, and li berates from it a chemical substance called
THE DIGESTIVE SYSTEM 89
" secretin," which is absorbed by the blood, carried to
the pancreas, and stimulates its alveoli to activity.
Action of the Pancreatic Juice. — The digestive action of
the secretion depends upon the three enzymes — trypsin,
amylopsin, and steapsin.
Trypsin converts proteins into proteoses, peptones, and
finally amino-acids.
Amylopsin acts on starch and breaks it up into dextrins,
and finally maltose.
Steapsin is the name given to the fat-splitting ferment ;
it breaks up fat into glycerol and fatty acids.
The following experiments should be performed to show
the action of the pancreatic juice : Obtain the pancreas of
a pig from a butcher. Chop it up and soak it in a weak
solution of sodium carbonate (1 part by weight in 100 of
water). Keep the mixture warm for some hours, and
finally strain off the liquid.
Add some of this artificial pancreatic juice to egg-white
nr a piece of meat, and keep it on a water-bath at the
temperature of the body for half an hour. The trypsin
will break up raw or coagulated protein first into soluble
peptone, and later into amino-acids. Apply the biuret
test to the protein solution at various stages in the reac-
tion. At first, when the protein is unchanged, a violet
coloration will be formed ; later it will be pink in colour,
showing the presence of proteoses and peptones ; and
finally no colour will be given, when the protein has been
completely hydrolyzed to amino-acids.
Add some of the juice to a solution of starch, and keep
this also at body temperature. The starch will be turned
by the starch-splitting ferment, or amylopsin, into sugar.
Test with iodine ; no blue colour will result. Then apply
Trommer's test by boiling a sample with a little copper
sulphate solution rendered alkaline by caustic potash ; a
yellow-red precipitate will be obtained.
90 HYGIENE
BILE.
Another digestive fluid that comes in contact with the
food in the small intestine is the bile. It is formed in the
liver, and carried from there to the duodenum by means of
a series of tubes called the " bile-ducts.'*
From a physiological standpoint bile is partly an excre-
tion carrying off waste products, and partly a digestive
secretion playing an important role in the absorption of
fats, and possibly in other ways. Bile is continuously
formed in the liver, but in animals that possess a gall-
bladder its ejection into the duodenum is intermittent
Composition of Bile.— The following are the most im-
portant constituents of bile :
Water.
Inorganic salts : Sodium chloride, sodium
carbonate, etc.
Sodium taurocholate.
Sodium glycocholate.
Mucin.
Bile pigments : Bilirubin and biliverdin.
Cholostcrin.
Lecithin.
Soaps.
Sodium Taurocholate and Glycocholate. — These are the
bile salts; the digestive function of bile is due to their
presence, because they facilitate the splitting and absorp-
tion of fats in the small intestine ; and they also serve as a
menstruum for dissolving the cholesterin and lecithin,
which are constantly present in bile, and are excretions
to be removed.
Bile Pigments. — There are two pigments generally present
in bile, called " bilirubin " and " biliverdin." These pig-
ments are derived from the haemoglobin, and are therefore
waste products of the red corpuscles of the blood. In the
intestine these pigments are reduced to a substance called
" stercobilin," which is the colouring matter of the faeces.
A portion of these pigments are absorbed, and give rite to
the pigments of the urine.
THE DIGESTIVE SYSTEM
91
Cholesterin is found in all animal cells, and is an important
constituent of the cell walls of animal tissue. It is said
to be an alcohol of the terpene series. It is soluble in
chloroform, and can be readily crystallized.
Lecithin is a complex compound containing glycerol, fatty
acids, phosphoric acid, and an organic base called " cholin."
Mucin is formed by the living membrane of the gall-
bladder and bile-ducts. It makes the bile viscid and
FIG. 45. — DIAGRAM SHOWING ANATOMICAL RELATIONS OF THE STOMACH,
GALL-BLADDER, BILE-DUCT, PANCREATIC DUCT, AND DUODENUM.
A, Stomach; B, gall-bladder; C, right and left hepatic bile-ducts;
D, common bile-duct ; E, pancreatic duct ; F, duodenum.
slimy. Mucin is readily precipitated on the addition of
acetic acid, and is insoluble in excess.
Tests for Bile. — Obtain some bile from a butcher, and
perform the following experiments :
1. Note its colour and slimy nature.
2. Add some acetic acid or vinegar to a portion of bile. A stringy
precipitate of mucin is formed.
3. Pour a little bile into a white basin, and add to this a few drops
of fuming nitric acid. A display of colours will result. This is called
" Gmelin's test," and is due to the presence of bile pigments.
92 HYGIENE
4. Place a little bile in a white basin, and dilute it with water ; add
a little solution of cane-sugar and sulphuric acid. On wanning, a beauti-
ful purple colour results. This is called " Pettenkofer'a teat," and U
due to the presence of bile salts.
Physiological Role of Bile. — Bile has both excretory and
secretory functions. It is of importance as an excretion
in that it removes from the body waste products of metabol-
ism, such as cholesterin, lecithin, and bile pigments.
Its most important secretory function is the part it
takes in the digestion and absorption of fats. It accelerates
greatly the action of the fat-splitting ferment of the pan-
creatic juice in breaking up the fats into fatty acids and
glycorol, and it further helps hi the absorption of the
products of this reaction.
Whenever bile is prevented from •reaching the intestinal
canal, a large portion of the fat of the food escapee absorp-
tion, and is found in the faeces. This occurs in human
subjects when the bile-passages are blocked by stones or
new growth ; then we find the faeces are very pale, due to
absence of pigment, and are very offensive, due to decom-
posing fatty acids. The bile is then absorbed into the
blood-stream, and gives rise to yellow pigmentation of the
skin, called " jaundice."
The older physiologists thought that bile prevented
excessive putrefaction in the intestine. This idea is
probably erroneous, because bile lias very weak, if any,
antiseptic properties. The addition of bile or bile salts to
the contents of the stomach causes precipitation of the
unaltered native protein, and it has been suggested that
by thus precipitating the constituents of the chyme, which
have not been carried to the peptone stage, bile prepares
them for the action of pancreatic juice.
PHYSIOLOGY OF SMALL AND LARGE INTESTINE.
Anatomy. — The small intestine is the portion of the
digestive tube which lies between the stomach and the
beginning of the large intestine. It commences at the
THE DIGESTIVE SYSTEM
93
pyloric orifice of the stomach, and ends at the ileo-csecal
opening, where it joins the large intestine. It occupies the
greater portion of the abdominal cavity below the liver and
stomach.
Structure of Small Intestine. — The wall of the small intes-
tine, like that of the stomach, is made up of four coats.
The outer or serous coat is formed of peritoneum, and is
complete throughout the
small intestine, except
for part of the duodenum.
The muscular coat is
composed of two layers
of muscular tissue, an
outer longitudinal and
an inner circular, and
between the two there is
a gangliated plexus of
nerves.
The submucous coat is
made up of connective
tissue, and in it the blood-
vessels and lymphatics
ramify before entering or
after leaving the mucous
membrane. It also con-
tains a gangliated plexus
of nerve fibres.
FIG. 46. — DIAGRAM ILLUS-
TRATING THE MICROSCOPIC p
STRUCTURE OF SMALL IN-
TESTINE.
A, Mucous coat ; B, muscularis
mucosse ; C, submucous coat;
D, circular muscular coat ;
E, longitudinal muscular
coat ; F, villus ; 0, intestinal
gland, or crypt of Lieber- E
kiihn ; H, layer of columnar
non -ciliated epithelium.
94 HYGIENE
The mucous coat is lined with a layer of columnar epi-
th( liuni lying on a basement membrane of connective tissue.
It also contains simple tubular glands, called the "crypts
of Lieberkiihn."
The lining membrane of the intestine between the glands
is thrust out in the form of finger-like processes ; these arc
called " villi," and serve to increase its area of absorption.
Inside this protrusion of mucous membrane we find a frame-
work of connective tissue, a few lymphocyte*, an artery,
vein, network of capillaries, and a lymphatic or lacteal.
Secretion of Glands of Small Intestine.— The following
are the most important constituents of intestinal juice :
Wator.
Salts : Sodium chloride, potassium chloride,
sodium carbonate, etc.
Erepsin, entorokinaae.
InvertaM.
Maltasc.
Erepsin is a ferment which breaks up proteoses and
peptones into amino-acids. It is said not to have any
action on native proteins.
Invertase is an enzyme which converts cane-sugar to a
mixture of glucose and fructose.
Lactose breaks up lactose into galactose and glucose.
Maltose hydrolyzes maltose into glucose.
Enterokinase is a substance wliich activates trypsinogen,
the inactive form of trypsin.
Changes undergone by Food in the Small Intestine. — In
the small intestine food is acted upon by three digestive
secretions — namely, the pancreatic juice, intestinal juice,
and the bile.
The proteins of the food, after being partly digested in
the stomach, are further hydrolyzed into amino-acids by
the action of trypsin and erepsin.
The starchy constituents of the food whicli have escaped
the action of ptyalin of the saliva are converted into
maltose by the action of amylopsin of the pancreatic juice.
THE DIGESTIVE SYSTEM
95
Maltose is broken up into glucose by the action of the
maltase of intestinal juice.
Lactose is hydrolyzed by the action of lactase into
galactose and glucose.
Cane-sugar is split up into glucose and fructose by the
action of invertase.
Fats by the action of bile and steapsin are emulsified,
and then hydrolyzed to glycerol
and fatty acids.
Large Intestine. — The large
intestine extends from the ter-
mination of the ileum to the
anus. It is about 5 feet in
length, being about one-fifth
of the whole extent of the in-
testinal canal. It is largest
at its commencement at the
caecum, and then diminishes
as far as the rectum, where
there is a dilatation of con-
siderable size just above the
anus.
Absorption. — Absorption is
the process by which the food-
stuffs are taken up from the FIG. 47.— THE VALVE BETWEEN
lumen of the gut into the blood ™SETI^RGE AND SMALL IN'
or lymphatic stream.
^ r, ,, , ,. a, Small intestine; b, large in-
One of the great functions testine ; e, /, valve ;?, appendix.
of the small intestine is to
absorb the digestive products of the food, which have been
formed by the action of the gastric juice, the bile, pan-
creatic juice, and the intestinal juice. The columnar cells
which line its walls perform the work of absorption, and.
since they must absorb sufficient food for the whole body,
the small intestine is about 20 feet long, and its absorbing
surface is greatly increased by the folding in of mucous
membrane in the form of valvulae conniventes and villi.
96
HYGIENE
The columnar cells which line the intestine have the
power to take up the various products of hydrolysis of the
foodstuffs, and to pass them along into the capillaries or
Fio. 48.— DIAGRAM SHOWING THK MICBOSCOPIC STRUCTURB or LARGE
I vn » n\ r.
A, Mucous coat ; B, muscularis mucoea ; C. submucous coat ; D. circular
muscular coat ; E, longitudinal muscular coat ; F, layer of columnar
non-ciliated epithelium lining the large intestine ; 0, glands of large
intestine.
lac teals. By some extraordinaiy means the products of
hydrolysis of proteins — namely, amino-acids — and those of
THE DIGESTIVE SYSTEM 97
the carbohydrates — namely, sugars — are carried to the
blood-capillaries ; while the products of hydrolysis of fats
are re-formed into fats and carried along the lymphatics
or lacteals.
Absorption is no mere physical process of diffusion and
filtration. It must be taken into account that the cells
through which the absorbed substances pass are living,
and, in virtue of their vital activity, not only select materials
for absorption, but also change these substances while in
contact with them. Also, when the cells lining the intes-
tine are removed or rendered inactive by sodium fluoride,
absorption practically ceases, though the opportunities for
simple filtration or diffusion would by such means be
increased.
Absorption of Carbohydrates. — All the starches and com-
pound sugars are hydrolyzed to the simple sugars before
absorption, and the carbohydrates are mainly absorbed as
glucose.
After absorption the glucose is carried along the portal
vein to the liver, and there stored up temporarily as
glycogen.
Absorption of Proteins. — The proteins of the food are
converted by the proteolytic enzymes of the digestive
juices into amino-acids, and are absorbed as such. They
are taken up by the blood-capillaries of the intestines,
carried along the portal vein to the liver, where the nitrog-
enous moiety is often broken off and converted to urea,
and the other moiety changed to glycogen. Some of the
amino-acids are allowed to pass through the liver, and are
used in the building up and repair of the tissues.
Absorption of Fats. — Fats are hydrolyzed during the
process of digestion into glycerol and fatty acids. The
columnar cells of the intestine resynthesize the fats after
absorption from their components. The lymphatic vessels
or lacteals of the villi take up the fat, and it is carried
along the main lymphatic vessels, which open into the
great veins at the root of the neck.
7
98 HYGIENE
Faeces are the waste products of the digestive system.
They differ greatly in amount and in composition with the
character of the food. Their amount is greatest on a vege-
table diet containing large quantities of cellulose ; with a
protein diet, on the other hand, they are small in amount
and dark hi colour.
The most important constituents of faeces are —
1. Indigestible material, such as ligaments of meat or cellulose from
vegetable.
2. Undigested material, such as fragments of meat, starch, or fats,
which have in some way escaped the action of the digestive juices.
3. Product* of bacterial decomposition, such as indol and skatol.
They possess a disagreeable faecal odour.
4. Pigments — stercobilin and urobilin.
5. Inorganic salts — salts of sodium, potassium, calcium, magnesium,
and iron.
0. Bacteria, which form a large proportion of the weight of faces,
Movements of the Small Intestine. — In the small intestine
two kinds of movements are to be seen :
1. Segmentation movement. Both the longitudinal and the circular
muscular coats contract, causing alternating segment of constriction
and dilatation. This type of movement may originate at any part of
the gut. The function of these movements is to break up the food
into smaller particles, and mix it thoroughly with the digestive juice
of the intestine.
2. Peristaltic movements — waves of constriction preceded by a
wave of relaxation of the muscular coat of the intestine. These are the
movements which carry the food along the alimentary tract.
Movements of the Large Intestine. — These differ from
those of the small intestine mainly in the great frequency
of antiporistalsis — that is, a wave of peristaltic movement
running in the opposite direction to what it does in the
small intestine. It is to prevent the contents of the large
intestine passing along too quickly, and therefore allow
time for the absorption of water, which is one great function
of the large intestine.
Defecation is partly a voluntary and partly a reflex act.
But in the infant the voluntary control has not yet been
developed ; in the adult it may be lost by disease.
THE DIGESTIVE SYSTEM 99
The faeces gradually accumulate in the pelvic colon and
rectum, and by their presence stimulate the sensory nerves
of the rectum and produce a distinct sensation and desire
to defaecate.
The involuntary factor is found in the contractions of
the strongly-developed musculature of the rectum, espe-
cially the circular layer, which serves to force the faeces
onwards ; and there is also relaxation of the internal
sphincter.
The voluntary factor in def aecation consists in the inhibi-
tion of the external sphincter, a muscle which closes the
anus, and the contraction of the abdominal muscles.
PHYSIOLOGY OF THE LIVER.
The liver is one of the most important organs in the body.
It is situated in the upper part of the abdomen ; its upper
convex surface fills the dome of the diaphragm on the right
side. Since it is situated near the diaphragm, it is pushed
down and compressed by its contraction. Muscular exer-
cise increases respiratory movements ; it will quicken the
circulation in the liver, and therefore prevent its con-
gestion. It is a very vascular organ, and contains about
one-fourth of the blood in the body. It is divided into five
lobes by five fissures. Into one of these fissures, called the
" transverse fissure," pass the portal vein, the bile-duct,
and an artery — the hepatic artery.
At the upper edge of the posterior surface two large
veins issue, called the " hepatic veins " ; these carry blood
away from the liver, and after a very short course open into
the inferior vena cava, which passes in close relationship
to the posterior surface of the liver.
If a section of the liver be examined microscopically, it
will be found to be made up of polyhedral masses, com-
posed of cells, separated from one another by connective
tissue.
Each of these masses, or lobule, is penetrated by a fine
network of connective tissue, which helps to support the
100
HYGIENE
Fio. 49.— AKTERIOB SURFACE OF THE LIVER.
4 Riuht lobe ; B, left lobr ; C. longitudinal teurc ; D, round ligament ;
K, fall- bladder.
FlO. 50. — UXDER-SURFACE OF THE LlYEB.
A, Right lobe ; B. left lobe ; C, quadrate lobe; D. inferior vena cava ;
E. gall-bladder; F, round ligament; 0, bile-duct; //, hepatic
artery ; A', portal vein.
THE DIGESTIVE SYSTEM
101
columns of cells within the lobule. The bloodvessels which
enter the liver through the portal fissure — namely, the
portal vein and hepatic artery — finally break up to very
small branches, which penetrate to the intervals between
the hepatic lobules.
On leaving the hepatic lobules, these bloodvessels are
joined together, and finally form the hepatic veins.
The bile -ducts commence as very small channels in
between the liver cells ; these finally join up and form ono
FIG. 51. — MICROSCOPIC SECTION THROUGH A FRAGMENT OF THE LIVER
SHOWING Two LOBULES.
A, Liver cells ; B, branch of hepatic vein ; G, branch of bile-duct ;
D, branch of portal vein.
duct, which leaves the liver by the portal fissure, and opens
into the first stage of the duodenum.
Functions of the Liver. — It has been said above that the
carbohydrate of the food is converted to grape-sugar or
glucose by the action of the digestive juices, and carried as
such in the portal vein to the liver.
If this sugar is not required in other parts of the body,
it is converted by the liver cells into glycogen ; this is a
carbohydrate similar to starch, but gives a red coloration
102 HYGIENE
with iodine. Therefore the liver is a temporary storehouse
for carbohydrate food after absorption.
The proteins of the food are converted by the action of
the enzymes of the alimentary canal into amino-acids, and
are absorbed as such into the portal vein and carried to
the liver. The amino-acids are made up of nitrogenous
and non-nitrogenous moieties. The greater part of the
nitrogenous moiety is cut off from the amino-acids in the
liver and converted to urea, while the non-nitrogenous
moiety is converted to glycogen. The liver is the most
important site of formation of urea.
The red cells of the blood are continually being formed
in the red marrow of bone, and after a certain period of
activity they are destroyed in various parts of the body ;
their pigment or haemoglobin is discharged, and carried to
the liver, and there converted into the pigments which are
found in the bile.
The liver also manufactures the bile, which is partly a
digestive secretion and an excretion. (For properties and
function of bile, see pp. 92.)
Ductless Glands.— There are a number of glandular
structures in the body which have no ducts, but their
secretion is poured into the blood-stream and carried to
all parts of the body. Their secretory products have
various important functions. The spleen, the thyroid, and
t lie suprarenal capsules, are examples of the ductless glands.
The Thyroid Gland. — This gland lies on the anterior aspect
of the neck. It consists of two lobes lying on each side of
the trachea, and an isthmus which passes in front of the
trachea. It is surrounded by a capsule of connective
tissue, and the glandular portion is made of minute sacs ;
each sac is lined by a layer of cells, and contains a glassy-
looking substance.
If the gland is not developed, the child grows up a cretin.
Bodily and mental growth is arrested, and an adult cretin
will remain the size of a child and behave like a child. If
THE DIGESTIVE SYSTEM 103
a cretin be fed on thyroid glands taken from sheep, his
condition will greatly improve, and he may develop like
a normal child, but he will have to take thyroid continu-
ously. If the thyroid degenerates prematurely in older
people, a very peculiar condition called "myxcedema"
results ; there is mental dulness, physical inactivity, in-
crease in the fat under the skin ; the hair falls out.
o
Fm. 52. — DIAGRAM SHOWING MICROSCOPIC STRUCTURE OP THYROID
GLAND.
A, Alveoli; B, cubical cells lining alveoli; 0, colloidal material inside
alveolar cavity ; D, connective tissue.
It is therefore evident that the thyroids produce a sub-
stance that is essential for the proper growth and the tissue
changes of the body.
Suprarenal Capsules. — These are two small structures
situated in the abdomen. One rests on the top of each
kidney. If they are both removed in an animal, death
results in a few days. Man rarely suffers from a diseased
condition of these glands. The symptoms and signs are
104
HYGIENE
very characteristic : pigmentation of the skin, vomiting
and diarrhoea, great physical exhaustion. If an extract of
the central portion of the suprarenal capsule be injected
under the skin, it causes great rise
in blood-pressure ; or if it is applied
to the external surface of a wound,
it causes constriction of the vessels
and stops bleeding. It is thought
that the suprarenal gland secretes
an active substance called " adre-
nalin,'* which keeps up the tone of
the sympathetic nervous system.
r. • ':'-•' .mi-- »vv* ••-.'•. '.:•••« ''mc-s. ' .
mm
Ki^w3?i^^^
Fio. 63, — MICROSCOPIC
STRUCTURE OF SUPRA-
RENAL CAPSULE.
A, Cortex ; B, medulla ;
1, 2, 3, 4, various layers
making up the cortex.
Fio. 64.— MICROSCOPIC STRUCTURE OF
SPLEEN (Low POWER).
A, Capsule; B, trabeoula; 0. spleen
pulp containing various cells ; D, aggre-
gation of lymphocytes around some
small arterioles.
The Spleen. — This is another ductless gland, and is
situated in the upper part of the abdomen, on the left side
and behind the stomach.
The exact function of it is not known ; it can be re-
THE DIGESTIVE SYSTEM 105
moved from the body without any deleterious results. It
is probably a site of destruction of red blood-corpuscles ;
it certainly forms certain kinds of white blood-corpuscles.
It undergoes rhythmic expansion and contraction, and this
is said to help the movement of the blood along the portal
veins.
FOOD AND NUTRITION.
It has been said above that life is maintained by the
oxidation of the foodstuffs in the tissues. Such oxidation
results in the formation of water, carbon dioxide, and
other waste products, which are eliminated. Concurrently
with this oxidation we should expect a loss in weight, and
this is found to be the case. Thus, if a man be weighed by
means of a sensitive balance, loss of weight will be registered,
which gradually increases as the interval of time from the
last meal lengthens. When a meal is taken, the weight
will suddenly increase by an amount equal to the weight
of the food taken in ; but immediately afterwards the weight
will commence to decrease, and continue to do so until the
next meal, when the weight will again go up by a corre-
sponding amount.
At the end of twenty-four hours a man will be found to
have much the same weight as he did at the beginning, for
practically all the food taken in has been oxidized and its
waste products eliminated.
If the same experiment were performed with a child, it
would be found that he would have gained in weight, for
in it the intake is greater than the loss.
On the other hand, if the weight of a man that was
starving or doing very hard muscular work were taken
at the beginning and end of twenty-four hours, it would be
found that there would be a loss in weight.
In a healthy adult the main objects of a diet are to
furnish sufficient nitrogenous and non-nitrogenous food-
stuffs, salts, and water, to maintain the body in equilibrium
of material and energy ; that is, the diet must furnish the
106 HYGIENE
material for the regeneration of tissue, and the material
for the heat produced and the muscular work done.
The diet of a child must supply the necessary amount
of energy for the production of heat and all activities of
the body, the repair of the tissues and the building up of
new tissues, which take place during growth.
At the beginning of this section it was said that food-
stuffs may be divided into three main classes — the carbo-
hydrates, fats, and the proteins.
Carbohydrates have three main uses to the body :
1. They furnish a source of energy for muscular work. All the
carbohydrates are converted to grape-sugar before they can be absorbed,
and this, when it passes to the liver, becomes converted to glycogen ;
or it may be stored in the muscles as glycogen. It has been proved that
the glycogen of a muscle disappears in proportion to the work done by
the muscle. Under normal conditions this material furnishes the main,
if not the sole, source of energy for muscular work.
2. The oxidation of the sugar reeulU in the formation of heat. The
heat of the body is produced by the oxidation of theae substances in
the muscles.
3. The oxidation of the sugar protects the proteins of the body. It
will be shown later on that proteins are absolutely essential to the
body. Man could live on protein food alone, but life could not be
sustained on a diet made up of starches and faU entirely.
It would not be advisable for man to live on a protein
diet alone, because the amount of protein that he would
have to take would be so large that it would throw too much
work on some of the internal organs — namely, the liver
and the kidneys. Life can be properly sustained on a
much smaller amount of protein if carbohydrate food is
increased, and therefore physiologists state that the
starches and sugars act as protein-sparers, in addition to
being a source of heat and energy.
Fats have important nutritive functions, which corre-
spond very closely with those of the carbohydrates :
1. During their oxidation in the body they give rise to a large amount
of heat, because 1 gramme of fat yields 9,300 calories of heat, twice as
much as 1 gramme of carbohydrate or protein. (A calorie is the amount
of heat necessary to raise 1 gramme of water through 1° C.) Hence
THE DIGESTIVE SYSTEM
107
we find inhabitants of cold regions choosing a diet that is very rich in
fat.
2. Fats are protein-savers, because their oxidation protects the protein
from consumption ; but in this respect fat is not so effective as an equiva-
lent amount of carbohydrate food.
Another very important function of fat is that it provides
a store of reserve food, which is used up by the body in
case of deficiency of food or complete starvation. The
fat in the skin acts as a natural garment, keeping in the
body heat, and rounding off the figure and giving beauty
and softness of form.
Proteins are absolutely essential for the maintenance of
life, and their functions may be briefly summarized as
follow :
1. They are the essential factors in the building up of tissues, and
repairing the changes due to the wear and tear of the body.
2. They serve as a source of body heat and other forms of energy,
but for this purpose carbohydrates and fats are better, because they
are cheaper and do not throw such stress on the digestive organs.
Since childhood is the period at which there is the greatest
amount of building up of the tissues, it is impossible to
exaggerate the importance of a sufficiency of protein in the
diet of children. No doubt much of the feebleness, flabbi-
ness, and pallor, of the children of the poorer classes in large
towns are due to a lack of it.
The following figures have been quoted from Dr. Robert
Hutchison's " Diet and Dietetics." They show the amount
of each nutritive ingredient required at different ages.
Age.
Protein.
Fat.
Carbohydrates.
1£ years
2
42«5 grammes
45-5
35 grammes
36
100 grammes :
110
3
50
38
120
4
53
41-5
135
5
56
43
145
8-9
60
44
150
12-13
72
47
245
14-15
79
48
270
108 HYGIENE
NUTRITIONAL DISORDERS.
Overeating. — There is no doubt that under conditions of
modern civilization a large number of people eat too much.
This involves greater work on the digestive system, the
liver, and the kidneys. For some years they are able to
cope with this extra work, but later on we find the organs
of the body prematurely decay, the bloodvessels become
thickened, the blood-pressure is increased, and great work
is thrown on the heart, which prematurely becomes ex-
hausted. Dyspeptic troubles in young adults are very often
duo to overfeeding.
It is said that many men used to a luxurious life are
enormously improved in health by the hard diet and hard
labour of a prison. Centenarians are not found among the
luxurious, but among those who have lived sparingly and
have worked hard throughout their lives.
Underfeeding amongst the poorer classes is a very
common cause of a weak physique, and predisposes the
body to all forms of disease. Unless the body is supplied
with sufficient food to carry out its functions and build up
new tissues during growth, the individual will grow up
having a weak constitution, will be attacked by various
diseases, and will not become a useful member of the
community.
Decomposing Foods give rise to irritation of the alimen-
mentary system, resulting in vomiting, diarrhoea, and pain
in the abdomen. Fortunately, Nature, as it were, applies
the remedy, expels the noxious food from the body, and
the person then recovers ; the young, the old, and the
infirm, may, however, be so prostrated by excessive vomit-
ing and purging that they may sink from exhaustion.
Alcohol. — The Board of Education has issued an excel-
lent syllabus of lessons on temperance for scholars attending
the public elementary schools, and the teacher should
procure a copy and make a close study of it.
Healthy persons are better without taking any form of
THE DIGESTIVE SYSTEM 109
alcoholic beverages ; if alcohol be taken, it should not be
more than a glass of wine or beer at meals. Spirits should
only be given on the advice of a physician.
The degeneration of the tissues and the great loss of
nerve power produced by alcohol-drinking should be
forcibly impressed upon all.
Malnutrition. — The common signs of malnutrition are
arrested growth, anaemia, and sallow skin ; flabby and
deficient muscles ; emaciation ; digestive troubles — diar-
rhoea and vomiting ; mental dulness, inattention, and
lassitude.
Good nutrition is not synonymous with stoutness, nor
bad nutrition with thinness, though at the same time the
majority of children who are well nourished are also chil-
dren who are well up to the standard as regards weight,
while the majority of children poorly nourished are pro-
portionally below the standard. A flabby, rickety child
may be above the standard in regard to weight, and yet
be, strictly speaking, of poor nutrition ; while a muscular
child of slender build may be below the weight standard,
and yet of good nutrition. Thus, although stoutness or
thinness of a child are important indications of the nutrition
of the child, they should be taken in conjunction with other
signs, such as the presence or absence of anaemia, the
character of the complexion, the condition of the eyes and
skin, and the character of the hair.
Rickets is a very common disease due to bad nutritive
condition, and the results of this disease are frequently
met with in schools of the poorer districts.
Sir William Jenner said many years ago that " Rickets
is the most common, and in its indirect results the most
fatal, of the diseases which peculiarly affect children."
The great cause of this disease is the substitution of
artificial and improper feeding in place of breast feeding.
It occurs in children who are fed in infancy on condensed
milk, or have a deficiency of fresh milk and fats and an
excess of starchy food.
110 HYGIENE
The signs of rickets are readily recognized. There is
pallor and general weakness ; bones are very brittle and
easily fractured ; there is a characteristic square head ;
the ribs are beaded ; the upper part of the chest is narrow
and constricted ; the ends of all the long bones are enlarged
— consequently there is enlargement of the wrists, ankles,
or knees ; the spine may be curved and the legs bent ;
knock-knee and flat-foot may arise from rickets.
Rickety children in schools should be sent to the medical
officer, who will advise proper treatment and give the right
instruction to the parents. They should be excused from
standing too long, because the bones are soft and give way
under the weight of the body ; and for the same reason these
children are very liable to bony deformity, and greater
care should be taken that their postures and attitude do
not tend to produce deformities.
Feeding of the School-Child. — A large number of tho chil-
dren in our elementary schools are underfed, and this is
due to the social conditions under which the poorer mem-
bers cf the community live in the large towns.
Since the education of the child has been made com-
pulsory, it is the duty of the State to see that the physical
condition of the child is such that it will benefit from the
education that is provided for it.
Up till 1906 voluntary associations had undertaken to
feed the necessitous school-child.
In 1905 the Relief (School-Children) Order was issued
by the Local Government Board, by which certain pro-
visions of the Poor LAW were adapted to the relief of
elementary school children in a state of destitution from
want of food.
At the end of the year 1906 the Education (Provision of
Meals) Act came into operation. It permits of the forma-
tion of a school canteen committee, composed entirely of
members of the local education authority, or of such
members in combination with the committee of any volun-
tary association for the provision of school-meals. In
THE DIGESTIVE SYSTEM 111
certain cases the education authority may defray the cost
of food from the rates, provided that the sum expended
does not exceed the amount which would be produced by
a halfpenny rate in the pound.
The adoption of this Act is permissive, and not obliga-
tory.
If the local authority are going to take advantage of the
provisions of this Act, they must first of all adopt it ; and
if the voluntary funds are insufficient, the local educational
authority must pass each year a resolution that there exist
in the schools children unable to take advantage of the
education provided because of lack of nourishment. The
Board of Education will then sanction the spending of
a definite sum on food. A committee is formed to which
is entrusted the organization of school-meals and the selec-
tion of suitable children.
An application is made by the parent to the teacher,
attendance officer, school-nurse, or medical officer, and each
case is investigated by the canteen committee. The degree
of poverty which entitles the child to receive free meals
varies in different localities ; generally it is taken as three
shillings weekly per member of the family.
The drawing up of the menu should be left to the school
doctor. The meals should be economical, easily cooked,
satisfying, and based on scientific principles.
The dietary will vary in different localities.
CHAPTER IV
CIRCULATORY AND RESPIRATORY SYSTEMS
FUNCTIONS, MORPHOLOGY, AND PROPERTIES, OF BLOOD.
BLOOD is the most important fluid in the body, and the
functions that it performs are numerous and most essential
to the maintenance of life. A healthy condition of the
body is impossible unless the blood performs its duties
properly. We Mill first of all enumerate some of its im-
portant functions, and then give a short account of it*
composition, morphology, and properties.
The functions of the blood are —
1. To carry nourishment from the digestive system to all parts of the
body.
2. To absorb oxygen from the lungs and distribute it throughout the
tissues, and also to carry carbon dioxide away from the tissues to be
eliminated by the lungs.
3. To remove the waste products from the tissues, and cany them
to the excretory organs.
4. It is by the blood that the heat of the body is equally distributed
throughout.
5. To convey substances from certain organs that are essential for
the proper working of all other parts of the body— «.p., secretions from
duct has glands.
6. To protect the body against the invasion of micro-organisms, and,
if they gain entrance to the body, to destroy them and neutralize their
poisonous effects. The study of this question — namely, immunity —
has uceived very great attention during the last ten years.
7. A very large percentage of the body is made up of water, and one
very important function of the blood is to keep this percentage constant.
Composition of Blood. — Blood is made up of a large number
of small cells, wliich float in a liquid of complex composition.
112
CIRCULATORY AND RESPIRATORY SYSTEMS 113
The cells which are present in the blood are called the
" blood-corpuscles," while the liquid in which they float is
called the " blood-plasma."
The corpuscles of the blood are of two kinds — namely,
red and white. We must consider the structure and func-
tion of each.
Red Blood-Corpuscles. — These are very small disc-shaped
cells ; they can only be seen by means of a microscope.
They are thicker in the periphery than in the centre, and
contain no nucleus ; thus, the general way of describing
FIG. 55. — RED. BLOOD -CORPUSCLES.
I. Mammalian cell : A, surface view ; B, side view ; C, rouleaux forma-
tion. II. Red blood-corpuscle of frog : N., nucleus.
the structure of the red corpuscle is to say " that it is a
biconcave, non-nucleated disc." It has a cell body, or
stroma, which is permeated by a peculiar protein substance
called " haemoglobin." Each red blood-corpuscle measures
about srftni inch in diameter. Their shape is easily changed,
as happens when they pass through small tortuous vessels.
In order to examine the blood-corpuscles, you should
perform the following experiments :
Experiment A. — Prick your finger near the base of the nail by a needle,
which has been previously sterilized by being passed through tne Hams
8
114 HYGIENE
of a match. Place a drop of blood on a slide, and examine it with the
microscope. You will notice the rod corpuscles as small circular bodies
floating in an almost colourless liquid medium. These corpuscles are
straw-coloured, and it is only when there is an aggregation of a large
number of them that they result in the red colour characteristic of
blood. Note also that the rod corpuscles tend to aggregate together in
a peculiar fashion, similar to a distorted pile of coins ; this is called
" rouleaux formation," ana is brought about by the peculiar consistency
tf these bodies.
Experiment B. — Again prick your finger, with the above-mentioned
precautions, and place a drop of blood near one end of a slide which has
bean thoroughly cleaned and rubbed with fine emery paper. The drop
of blood is now drawn into a film, by the edge of a second slide, which is
held at an angle of 45 degrees to the first one. This should be done by
one light movement, which should not be repeated unless the slide is
cleaned and a fresh drop of blood placed upon it. Having obtained
a good even film, allow it to dry in the air. Then place upon it some
staining reagent ; the commonest one used is called " Irishman's stain ";
it is made of a mixture of mcthylenc blue and eosin dissolved in methyl*
alcohol. Pour on the film a few drops of Irishman's stain, and allow
it to remain there for thirty seconds, during which the film is fixed
and prepared to take up the stain ; then dilute it with three times its
volume of distilled water, and allow it to stain for four or five minutes.
Then wash the slide in distilled water and dry between two pieces of
blotting-paper. Examine the film with the high power of the microscope.
All the corpuscles of the blood will stand out much more clearly ; the red
cells will be stained red by the eosin. and the white cells can be readily dis-
tinguished by their nuclei being stained blue, and the protoplasm of the
cells stained blue or terra-ootta colour, according to its staining property.
Of these red cells, there are 5,000,000 in the male and
4,600,000 in the female in each cubic millimetre of blood —
a droplet about the size of a small pin's head. In the study
of various conditions of anaemia it is very important for
the physician to know how many corpuscles are contained
in each cubic millimetre of his patient's blood. The red
cells are enumerated by an instrument called a " hflemo-
cyto meter," which is shown in Fig. 56. One cubic milli-
metre of the patient's blood is drawn up into a small
pipette ; this is diluted a hundred times by drawing up a
certain special salt solution. After thorough mixing of the
two fluids, a drop of the resultant mixture is made to fall
into a small trough on a microscopic slide. The bottom of
CIRCULATORY AND RESPIRATORY SYSTEMS 115
this trough is divided out into small squares of known area,
generally -ffa square millimetre, and the height of the
trough is generally ^o millimetre ; therefore each square
would enclose a volume of j^Vu cubic millimetre. By
placing it under a microscope the corpuscles in each square
can be enumerated ; this is done for a large number of
squares, and the average taken ; since we know the volume
of each square and dilution of the blood, the number of red
corpuscles in each cubic millimetre of undiluted blood can
be calculated.
FlG. 56. — H-SIMOCYTOMETER, OR INSTRUMENT FOR ENUMERATING THE
CORPUSCLES OF THE BLOOD.
The important function of the red cells is to carry oxygen
from the lungs to the tissues, and carbon dioxide away
from the tissues to the lungs. This is performed by means
of the red pigment, called " hsemoglobin," that is present
in the red corpuscles.
Haemoglobin is the most important constituent of blood,
to which it gives its characteristic colour and forms 13 per
cent, of its weight. It is a very complex substance, made
up of a protein combined with hsematin, an iron-containing
pigment. It is able to combine loosely with oxygen when
it is brought into contact with it, forming oxyhaemoglobin,
and on reaching the tissues it will give up its oxygen to
116 HYGIENE
them, where the oxygen combines with the foodstuffs in
the complex processes called " metabolism.*' One resultant
product of metabolism is carbon dioxide, and both the
corpuscles and the plasma combine with tliis and carry it
to the lungs. The scarlet colour of arterial blood is due
to oxyhaemoglobin, and the dark colour of venous blood is
due to haemoglobin which has given up oxygen.
If distilled water be added to blood, it causes the red
corpuscles to swell up and finally bunt, and the haemoglobin
is taken in solution, and the only remnant of the corpuscle
will be a colourless protein shell, representing the stroma
on which the haemoglobin was deposited. By certain pro-
cesses haemoglobin can be obtained in a crystalline condi-
t ion from the above solution. It is of great importance that
haemoglobin forms only a loose compound with oxygen.
The oxygen is easily combined and easily given up to the
tissues. There is another gas, carbon monoxide, which
forms a very stable compound with haemoglobin, and then
it becomes of no use to the body. This is what happens in
coal-gas poisoning.
Most other pigments, such as those of the bile, urine, and
farces, are derived from haemoglobin.
Origin and Life-History of Red Cells.— The red blood-
corpuscles tie frfUMHJ in the embryo in the parts which
give rise to the MoodTBMeli. The liver, the spleen, and the
red bone- marrow, are also sites of their formation at this
period of life.
In the adult they are formed only in the red bone-
marrow.
It is not known exactly what is the life-history of the
red blood-corpuscles, but it is certain that they are de-
stroyed in various parts of the body. The haemoglobin
is liberated and carried to the liver, where it is converted
into bile pigment*, and from these the pigments of the
urine and faeces are formed.
The White Blood- Corpuscles. — In order to study the white
blood-corpuscles, you should make a blood-film as de-
CIRCULATORY AND RESPIRATORS SYSTEMS 117
scribed in Experiment B. Take great care to obtain a
good film, and stain it well. The white cells of the blood
are not so numerous as the red corpuscles — only about
7,000 to 10,000 per cubic millimetre of blood. They are
enumerated by a method similar to that applied in the case
of red corpuscles, except that the blood is diluted five or
ten times by very dilute acetic acid with methylene blue
added to it. When you study them closely, you will find that
they are of two kinds — namely,
lymphocytes and leucocytes.
Lymphocytes are oval-shaped
cells, with a similarly-shaped
nucleus which nearly fills the
whole cell. In the blood- film
the whole cell will appear blue,
because the nucleus and the
protoplasm readily stain with
the methylene blue constituent
of your stain. Lymphocytes
are divided into two groups
according to their size — namely,
the small and the large.
Leucocytes are irregularly-
shaped cells, containing a
nucleus that is divided into ,4, Small lymphocytes; 5, large
several parts, joined together lymphocytes ; G, D, E, three
by strands of nucleus tissue.
The protoplasm of the cell
is granular, and the staining properties of these granules
serve to classify these cells into three different groups. In
some the granules will be small and numerous, and stained
a terra-cotta colour ; others will have a few coarse granules
of the same colour, while another group will have the
granules stained blue. These cells have great power of
independent movement.
Function of the White Blood-Corpuscles. — The white
blood -corpuscles may be looked upon as the protective
FIG. 57. — VARIOUS FORMS OF
WHITE BLOOD -CORPUSCLES.
forms of polymorphonuclear
leucocytes.
118 HYGIENE
army and the scavengers of the body. Wherever micro-
organisms gain access to the body, they cause, by the
products of their metabolism (toxins), a certain amount of
irritation to the tissues ; the blood carries away the toxins
which act as a stimulus to the formation of the white cells,
and these are carried by the blood to the site of invasion.
Then they will surround the germs and kill them, and carry
away their bodies and lay them aside, or destroy them
in situ. There are certain substances called " opsonins,"
present in the blood-plasma, which act on the bacteria
and aid their destruction by the white corpuscles. In this
struggle some of the white cells are killed, and if this
happens to a large extent their dead bodies in the tissue
fluids form matter, or pus.
Formation of White Blood-Corpuscles. — The two main
forms of white corpuscles have different modes of origin.
The leucocytes, or granular cells, are formed in the bone-
marrow, and there we find several different forms of cells
developing into adult leucocytes. From the bone-marrow
they are carried to the tissues.
The lymphocytes are formed in the lymphatic glands.
There we find certain cells dividing and giving rise to
lymphocytes, which are passed to the blood-stream.
Lymphatic Glands and Lymph. — The lymphatic glands are
small oval structures about the size of hazelnuts, and are
distributed through various parts of the body. They are
found at the side of and in front of the neck, at the root of
the lungs, in the mesentery (a membranous structure by
means of which the intestines are tethered to the posterior
wall of the abdomen), in the armpits and groins, and other
parts of the body.
When a section of a lymphatic gland is examined micro-
scropically, it is found to be made up of a capsule and
framework of connective tissue, in the interstices of which
lie a large number of lymphocytes. The manner of aggre-
gation of the lymphocytes is such as to divide each gland
into a cortical and medullary portion. In the former they
CIRCULATORY AND RESPIRATORY SYSTEMS 119
are accumulated to form lymphatic nodules, while the latter
has a loose structure, and the lymphatic cells are aggregated
into small cords.
Passing in and out of the lymphatic glands we find the
lymphatic vessels. In between all the cells of the body
there are potential cavities, which are called the " connec-
tive-tissue spaces." The lymphatic vessels take their
origin in these connective- tissue spaces, and pass along
to the lymphatic glands, from which vessels arise which
pass to another set of lymph glands, and finally into one
FIG. 58. — SECTION THROUGH A FRAGMENT OF A LYMPH GLAND.
A, Fibrous coat sending partitions into C, the pulp of the gland ;
B, denser masses of lymph cells ; D, bloodvessel in fibrous parti-
tion.
of the two main lymph channels which reach the blood-
stream. The lymph inside the vessels flows in one direction
— i.e., towards the veins. This is due to the action of the
valves which are present in the lymphatic vessel, and
which allow the lymph to flow only in that direction.
It will be seen that blood is carried to all parts of the
body by means of bloodvessels, which, as they recede from
the heart, branch repeatedly until very minute plexuses of
vessels are formed, called the " capillaries." These are
made up of a single layer of flattened epithelial cells.
The fluid constituents of the blood pass from the capillaries
120 HYGIENE
to the tissue spaces around, and this fluid is then called
"lymph."
Contraction of the muscles in all forms of movements,
and the action of the valves, are the two important factors
which cause the circulation of the lymph ; by these means
the connective- tissue spaces are pressed upon and their
contents squeezed out.
The amount of lymph in the connective-tissue spaces is
regulated by the activity of the cells lining the capillaries.
When these cells are injured by any form of irritant,
such as a blister, burn, or a bee-sting, the amount of fluid
poured out into the connective-tissue spaces is very much
increased at the site of injury, and results in a blister. In
some people a diffuse nettle-rash will appear when they
have partaken of certain things, such as crabs or mussels ;
this is due to the toxic effect of such diet upon the cells
lining the capillaries. The rashes of scarlet fever, measles,
etc., are caused by the toxic action of the organisms which
produce these diseases.
When germs or dust gain access to the tissue, they pass
into the connective- tissue spaces, and are then carried in
the lymph-stream to the nearest set of lymphatic glands,
where most often the germs are killed and the dust laid
aside. If the germs are so numerous that the glands
cannot cope with them, they cause irritation and reaction
on the part of the glands. The lymphocytic cells are
increased in number and the connective tissue is hyper-
trophied, and we have an inflammatory condition of the
glands. Everyone has experienced some form of inflam-
matory condition of glands. After a sore throat the
glands of the neck are often enlarged and tender. The
germs which cause consumption often gain access into the
body through the tonsils, and are carried along lymphatic
vessels into the lymphatic glands of the neck, giving rise
to the tuberculous condition of these structures. The
infection may be so severe as to cause the death of the
cells in the lymphatic glands, thus resulting in an abscess
CIRCULATORY AND RESPIRATORY SYSTEMS 121
formation. The greater part of the lymph that passes from
the blood-capillaries into the tissues returns into these
vessels ; it is only a small part which passes through the
lymphatic glands to the veins.
Blood-Plasma. — Plasma is blood that has been deprived
of its corpuscles. It is in the blood-plasma that the food-
stuffs are carried to the tissues and the waste products
conveyed to the excretory organs. It will contain the
three blood - proteins — fibrinogen, serum albumin, and
serum globulin — fats, traces of sugar, urea and uric acid,
inorganic salts, various enzymes and substances involved
in the means of protecting the body from bacterial invasion.
In order to obtain a specimen of plasma, some means
must be taken to prevent the clotting of the blood. One
method is to pass the blood, when the animal is being killed,
into a vessel containing strong salt solution, and leaving
the vessel to stand ; the corpuscles will drop to the bottom.
If the blood is allowed to be in contact with the vessel,
it will not clot ; hence plasma can be prepared by exposing
a large vein and after tying it at each end, cutting it out.
If the vein is suspended, the corpuscles will fall to the
bottom, and the plasma above can be removed by a pipette.
Coagulation, or Clotting of Blood. — The phenomenon of
clotting of blood is well known to everyone. In a few
minutes after its escape from the bloodvessels it becomes
viscous, and then sets into a soft jelly, which contracts
and becomes firmer, pressing out some clear, faintly yellow
liquid called " blood-serum."
Obtain a drop of blood from your finger, and allow it to
fall on a clean porcelain dish, and follow the changes that
take place during the clotting of blood.
In order to make a further study of the coagulation of
blood, you should have a greater supply of blood at your
disposal.
Take three vessels to a butcher on the day he kills ; in
one place a strong solution of salt, and just rinse the other
two with 0*9 per cent, salt solution. In one of the last two
122 HYGIENE
vessels place a small bundle of bristles or twigs from a
broom. Ask the butcher to collect some blood in each ;
two of the samples he must put aside undisturbed, while
the one with the twigs in it he should be told to whip
vigorously for a few minutes immediately after collection.
It will be found that one of the samples has clotted,
so that the vessel can be turned upside down without
spilling, and clear straw-coloured serum will have escaped
from the clot.
The one with the strong salt solution will be fluid, but
on dilution and placing it on a water-bath at the tempera-
ture of the body, it will clot.
The blood that has been whipped will be fluid, and en-
tangled on the bristles will be found shreds of material.
Wash these under the tap, and the shreds will be seen to
be made up of a white fibrous substance, called fibrin.
The essential factor in the coagulation of blood is the con-
version of a soluble protein called " fibrinogen" into an in-
soluble protein called " fibrin." This is brought about by
the action of a ferment, and the sequence of events in the
formation of a clot after injury to the body is as follows : When
the tissues are injured, some of the white blood-corpuscles
are killed, and during this process a ferment is liberated.
But the ferment is then in an inactive form. Certain sub-
stances from the tissues and the lime salts from the blood
activate the ferment, which is then able to convert the
fibrinogen into fibrin. This is deposited irregularly in fine
strings, and entangles the red corpuscles in its meshes.
These fibrin filaments contract, and the fluid constituents
and white corpuscles are squeezed out of its meshes,
forming the serum ; while the red cells are entangled,
forming the clot.
Clotting is a means devised by Nature to stop haemor-
rhage after an injury has been inflicted on any part of the
body. In some persons the blood has very weak power
of coagulating, and in them a slight injury will result in a
severe loss of blood.
CIRCULATORY AND RESPIRATORY SYSTEMS 123
CIRCULATION OF THE BLOOD.
From what has been said in the latter pages, it is seen
that the important function of the blood is to carry oxygen
and nourishment to the tissues, and to convey the waste
products from the tissues to the excretory organs. It
cannot perform such duties unless it comes into intimate
connection with the tissues ; and, further, it must come
into similar relationship with the lungs and intestine, in
order to absorb respectively oxygen and nourishment
therefrom. Such varied functions performed in distant
parts of the body can only be adequately fulfilled by a
movement of the blood through the various tissues ; this
movement is called the " circulation of blood."
Let us consider some of the most important factors
concerned in the circulation of the blood. It is brought
about by the pumping of the blood by the heart through a
series of elastic tubes, called the " bloodvessels." When
such a vessel conveys blood away from the heart, it is
called an artery, but when the direction of flow in a vessel
is towards the heart that vessel is called a vein. The small
bloodvessels which permeate the tissues are called the
blood-capillaries.
The cause of the circulation of the blood is the pumping
action of the heart, but several. other factors modify and
aid the flow of blood in the peripheral tissues and its return
to the heart — namely, the peripheral resistance, muscular
contraction, respiratory movements, etc.
It is therefore essential that we should know a little
about the 'anatomy of the heart and its great vessels in
order to understand the very elements of the circulation.
Anatomy of the Heart and its Great Vessels. — There is
very little difference between the main anatomical features
of a sheep's heart and that of the human subject. There-
fore ask your butcher to give you " a sheep's heart, with
the heart-bag and pluck attached, and the tubes cut long."
If he follows your instructions, you will be able to obtain
124
HYGIENE
the heart, lungs, and large vessels, in an undamaged state.
Then carefully note the following facts :
The heart and lungs will be seen to be closely associated,
and passing from the heart to the lungs are several tubes or
PR
PV
RA IV
Fio. 59. — HEART AND Lunos REMOVED FROM THE BODY.
A., Aorta ; 0., carotid arteries ; F, trachea; L., lung out open to show
branches of pulmonary artery, vein, and air-tubes; L.A., left
auricle ; L. V., left ventricle ; PR, pulmonary artery ; P. V., pul-
monary vein ; R.A., right auricle ; R. V., right ventricle ; 8., sub-
clavian arteries.
bloodvessels. You will also notice that the heart is enclosed
in a strong fibrous bag, which is called the " pericardium."
The Pericardium. — This is a strong fibrous bag enclosing
the heart. By means of a pair of scissors and dissecting
CIRCULATORY AND RESPIRATORY SYSTEMS 125
forceps, open the pericardium along its anterior surface
(the posterior surface is readily recognized, because passing
from it will be two vessels — one to each lung — and surround-
ing these will be a large amount of connective tissue and
fat). On section the pericardium will be seen to be made
up of two layers — an outer thick and tough layer, made of
white fibrous tissue ; and an inner smooth, glistening layer,
which on microscopical examination will be found to be
made of a layer of flattened epithelium lying on a thin bed
of connective tissue. It will be seen that this glistening
layer is reflected on and covers the outer surface of the
heart. The fibrous layer of the pericardium is attached
below to the central tendon of the diaphragm, whilst above
it merges with the outer coats of the bloodvessels which
leave the heart at its base. The pericardium has two func-
tions : the fibrous layer protects the heart, and prevents
its over-distension with blood ; the inner layer, by its smooth-
ness and secretion of a small amount of fluid, diminishes
friction, and allows the contraction and relaxation of the
heart to take place with greater ease.
The Heart. — Now direct your attention to the heart
itself. It will be seen to be a conical muscular organ, with
the apex downwards and the base above, where the great
vessels leave and enter it. A groove will be found running
along its anterior surface from above downwards, and in a
slight oblique direction, so that it passes a little to the right
side of the apex ; it will contain a small amount of fat and
a bloodvessel ; this is called the " inter ventricular groove,"
Corresponding to it there is a septum, which divides the
cavity of the heart into a right and left portion, and is
called the " inter ventricular septum." A second groove, con-
taining more fat, will be seen running transversely across
the heart, a little nearer the base than the apex ; it divides
each half of the heart into an upper auricular and a lower
ventricular portion ; this groove is called the " auriculo-
ventricular groove," and corresponds to a perforated
septum called the " auriculo- ventricular septum." Thus
126 HYGIENE
the heart is divided into four chambers — the right and left
auricles above, and the right and left ventricles below.
Now carefully remove all the connective tissue and fat
which surrounds the large vessels as they leave and enter
the base of the heart. Find a large elastic vessel which
can be seen anteriorly at the base. One arises from the
right ventricle, and lies more anterior ; it will be seen to
divide very soon into two branches — one for each lung.
This vessel is called the " pulmonary artery." The other
arises from the left ventricle, and at first is more posterior ;
it thus curves forward to form an arch on the right side of
the pulmonary artery. This second vessel is called the
"aorta," and is the chief artery of the body. Large
branches supplying the head and neck will be seen to arise
from the upper or convex surface of the arch.
Now turn your attention to the right and left auricles ;
note their shape and structure, and the vessels which enter
them. Both auricles are small, thin-walled bags, prolonged
anteriorly to crinkled projections lying close to the pul-
monary artery and aorta ; these projections are called the
" auricular appendices.**
Two vessels enter the right auricle — the superior vena
cava above, and the inferior vena cava below ; they carry all
the venous or impure blood from the tissues to the heart.
If you dissect on the posterior wall of the auricular
portion of the heart, two short vessels, one from each lung,
will be seen penning to the left auricle ; these are called the
" pulmonary veins," and carry oxidized blood from the
lungs to the left auricle. In man there are four pulmonary
veins — two from each lung.
Now take a probe or penholder, and pass it along all
these vessels, and find out to which chamber of the heart
it passes in each case. The superior and inferior venae
cavae will be seen to end in the right auricle ; the pulmonary
artery and aorta arise respectively from the right and left
ventricles ; while the pulmonary veins will be seen to end
in the left auricle.
CIRCULATORY AND RESPIRATORY SYSTEMS 127
Next turn your attention to the cavities of the heart.
Place one blade of your scissors into the superior vena cava,
and cut right through down to the inferior vena cava. The
cavity of the right auricle will be exposed ; it is lined by a
smooth, glistening membrane, and in the auricular appen-
dix there are bands of muscle called the " musculi pec-
B— *
FIG. 60. — DIAGRAM OF THE CAVITIES OF THE HEART AND
BLOODVESSELS.
A, Vena cava superior ; B, vena cava inferior ; G, pulmonary artery ;
D, aorta ; E, right auricle ; F, right ventricle ; O, left auricle, with
four pulmonary veins opening into it ; H, left ventricle. The
arrows show the direction of the circulation.
tinati." The right auricle opens into the right ventricle
by the right auriculo- ventricular opening, which is guarded
by a valve made of three flaps or cusps, and hence called
the " tricuspid valve."
Now make an incision into the anterior wall of the right
ventricle; further examine the right auriculo-ventricular
opening and valve. Also note the smooth character of the
128
HYGIENE
membrane lining its inner wall, and deep to this membrane
are bars of muscle called the " columnae carnae " ; some
of these are hypertrophied to form special muscles called
the " musculi papillares," which by tendinous cords become
attached to the cusps of the valves. In the right ventricles
there are three sets of musculi papillares ; by their contrac-
tion during ventricular systole, they prevent the valves
Fio. 61. — ANTERIOR SURFACE OP THE HEART.
A, Right auricle ; B, right ventricle ; C, superior vena cava; D, inferior
vena cava ; E. right auricular appendix ; F, aorta ; 0, pulmonary
artery ; H, coronary arteries.
being pushed into the auricles. In the upper part of the
right ventricle the pulmonary artery will be seen to arise.
Now cut the pulmonary artery transversely just above
where it leaves the right ventricle, and look downward to
the ventricle ; the opening will be seen to be guarded by a
valve made of three semilunar cusps — hence called the
''pulmonary semilunar valve1'; then lay open the pul-
monary artery and make further studies of its vulvee.
CIRCULATORY AND RESPIRATORY SYSTEMS 129
Make an incision into the anterior wall of the left ven-
tricle ; study its cavity. It will be found to communicate
with the left auricle by an opening called the " left auriculo-
ventricular opening," which is guarded by a valve made of
two cusps, and hence called the" bicuspid" or " mitral" valve.
Columns carnse will also be seen in the left ventricle,
and two sets are specialized to form musculi papillares,
FIG. 62. — POSTERIOR SURFACE OF THE HEART.
A, Left auricle ; B, left ventricle ; G, coronary artery ; D, aorta ;
E, superior vena cava ; F, inferior vena cava ; G, G, pulmonary
veins.
which are attached to the two cusps of the mitral valve by
means of chordae tendinese.
Cut the aorta transversely just above where it leaves the
left ventricle, and look within. Its opening will be found
to be guarded by a valve made of three semilunar cusps —
hence it is called the " aortic semilunar valve " ; then lay
open the aorta and further study its valve.
130 HYGIENE
At the bottom of two of the pouches formed by these
semilunar cusps small openings will be seen ; it is here that
the coronary arteries arise. These are of great importance,
because these vessels supply the musculature of the heart.
Place the blade of your scissors in the left auriculo-
ventricular opening, and open up the left auricle ; the
openings of the two pulmonary veins (four in man) will be
seen. Also examine the musculi pectinati of the left
auricle.
From the above dissection the course of the blood
through the heart can readily be followed. It enters the
heart by the superior and inferior venoe cavae, and passes
through the right auriculo- ventricular opening to the right
ventricle. From this chamber it is pumped along the pul-
monary artery to the lungs, and passing through their
capillaries returns to the left auricle by the pulmonary
veins ; it then enters the left ventricle, and is pumped
from this chamber along the aorta to all the tissues of the
body.
In order to understand the pumping action of the heart
and the working of its valves, perform the following instruc-
tive experiment, which has been taken from Dr. Leonard
Hill's " Manual of Physiology " :
The Action of the Heart as a Pomp.— Bay * sheep's heart, and
perform the following instructive experiment : Obtain two glass tubes
about 18 inches long and | inch in diameter. Insert one into the right
auricle through the superior vena cava ; tie it firmly within with a piece
of string. Take another piece of string, and tie the opening of the
inferior vena cava. Tie the other glass tube into the pulmonary artery
in such a position that the end of this tube lies just above the semilunar
valves. Now. holding up the heart by the two glass tubes, fill with
water the tube attached to the superior vena cava, and then rhythmically
squeeze the right ventricle with the hand.
With each squeeze the water will shrink in the vena cava tube and rise
in the pulmonary artery tube. This proves that the heart is provided
with valves, that fluid can be pumped only in one direction — namely,
from auricles to ventricles, and from ventricles to arteries. The water
in this experiment runs in the following way :
1. From superior vena cava through the right auricle to the right
ventricle.
CIRCULATORY AND RESPIRATORY SYSTEMS 131
2. On squeezing the right ventricle the pressure inside its cavity is
raised, and causes the tricuspid valves to come together and prevent the
return of the water to the auricle.
3. At the same time the increased pressure inside the ventricle forces
the semilunar valves open, and the water is drawn into the pulmonary
artery.
4. On ceasing to squeeze, the water runs again into the right ventricle
from the tube in the vena cava ; but it cannot return from the pulmonary
artery to the right ventricle, because the semilunar valves become closed.
The above experiment tells us how the living heart works.
Blood flows from the superior and inferior venae cavse to
the right auricle, and from thence through the auriculo-
ventricular opening to the right ventricle ; the muscular
wall of the latter then contracts, and expels the blood
within its cavity to the pulmonary artery ; then the ven-
tricle dilates and is refilled. Simultaneously with the above
processes blood flows from the pulmonary veins to the
left auricle, and thence into the left ventricle, which in its
turn contracts and expels the blood to the aorta. The
two ventricles fill together and empty together with perfect
co-ordination, and hence we have at first a simultaneous
contraction of both auricles, then an interval during which
the muscular contraction passes from the auricles to
the ventricles, followed by the simultaneous contraction
of both ventricles. This process goes on about seventy to
eighty times a minute during all our lives, and it is won-
derful that the heart is able to do its work so regularly and
effectually for so long a period.
Arteries, Capillaries, and Veins. — Blood is carried away
from the heart by means of a system of elastic tubes.
There are only two of these tubes leading from the heart
itself — one the pulmonary artery, carrying the blood to
the lungs ; and the other the aorta, which carries the blood
from the left ventricle to all other parts of the body. These
tubes, as they recede from the heart, give off a number of
branches, which in their turn subdivide, until the whole
body is penetrated by small vessels which are called the
" capillaries." These small vessels unite to form venules ;
132
HYGIENE
these, again, join to form veins ; and finally all the blood in
the human subject is returned to the heart by means of
two large veins, which open to the right auricle, and are
called the " superior and inferior venae cavae."
Structure of an Artery. — When a section of an artery is
examined by the microscope, it is found to be made up of
Fio. 63.— DIAGRAM SHOWING THE STRUCTURM SEEN WHEN THE
ANTERIOR WALL OF THE RIGHT AURICLE AND RIGHT YI.MKK 1.1.
HAS BEEN DISSECTED AWAT.
A, Superior vena cava ; B, inferior vena cava ; C, aorta ; D, pulmonary
artery ; E, cavity of right auricle ; F, cavity of right ventricle ;
Q, O, O, nmsculi papillares ; //, right auriculo-ventricular valve ;
A', chorda) tendineuo.
three coate. The inner coat is composed of a layer of endo-
thelial cells lying on a layer of connective tissue. The
middle coat, or tunica media, consist* mainly of circularly-
disposed plain muscular fibres intermingled with elastic
fibres. In the larger arteries — e.g., aorta and pulmonary
CIRCULATORY AND RESPIRATORY SYSTEMS 133
artery — there is more elastic than muscular tissue, while
the middle coat of the smaller arteries is mainly composed
of muscular tissue. The outer coat is formed of connective
tissue with a good many elastic fibres, especially next to
the middle coat. The strength of an artery largely depends
upon this coat ; it is far less easily cut or torn than the
other coats, and it serves to resist undue expansion of the
vessel.
Structure of a Vein. — The veins on the whole resemble
the arteries in structure, but they present certain differ-
ences. The middle coat contains far less elastic and
muscular tissue, but there are present a large number of
white connective-tissue fibres, and the outer coat is rela-
tively better developed in the veins than in the arteries.
The walls of the smaller arteries differ from those of the
larger arteries by a great increase in the number of muscle
cells and a decrease in the elastic fibres. Hence the larger
arteries are essentially extensile and elastic, while the
smaller arteries are muscular, contractile tubes.
As the smaller arteries branch into capillaries, the mus-
cular constituent of their walls becomes less and less, until
in the capillaries there is nothing left but a layer of flattened
cells separating the blood within from the tissues without.
It is through this layer of cells that the tissues absorb their
nourishment and oxygen from the blood, and also eliminate
their waste products to the blood-stream.
It has been said above that the great function of the blood
is to carry nutriment and oxygen to all parts of the body.
All the tissues are bathed in a continuous stream of blood,
which is moved along by the force of contraction of the
heart. This continual movement of the blood is called
its " circulation." Thousands of years were spent in study
and observation before this fact was discovered, and that
was because the older students of medical science studied
the dead more than the living body. After death the
arteries constrict and force the blood into the veins, and
so the old anatomists found the arteries .always empty
134 HYGIENE
after death, while the veins were full of blood. They
therefore came to the conclusion that it was the same
during life, and the arteries were said to contain " animal
spirits." It was reserved to the genius of an Englishman,
Harvey, by means of a few simple experiments, to prove
that the blood moves in a circle ; thereby he laid the
foundation of the modern science of physiology.
Harvey first observed the action of the valves in the veins
of the limbs. These can be noticed when you stroke your
arm downwards towards the hand ; little knots or swellings
will at once rise up in the course of the veins. If such
vessels were dissected, there would appear at each knot
small membranous flaps or valves placed within so as to
allow the blood to flow in one direction only — towards the
heart. Harvey concluded from this that the blood in the
veins could flow only in one direction — that is, from the
limbs towards the heart.
Harvey also made a large number of observations on the
direction of flow of blood in the heart and bloodvessels of
snakes, frogs, and fishes, and definitely proved the circula-
tion of the blcod.
Microscopical Study of the Circulation. — If any trans-
parent living membrane — e.g., web of a frog's foot or a
tadpole's tail — be examined by means of a microscope, the
blood can be seen circulating from the smallest arteries,
through the capillaries, to the venules.
The easiest way to see the circulation is to obtain a
tadpole ; wrap the body of it in wet blotting-paper, place
it on a glass slide, and examine the tail by means of the
microscope. The circulation can also be seen in the web of
a frog's foot. The digits must be spread out over a hole in
a sheet of cork. The frog can be put in a linen bag with
one leg left out.
It will be found that the flow is very rapid in the small
arteries, so much so that the shape of the corpuscles
cannot be readily detected ; in the capillaries the passage
is so narrow and tortuous that the corpuscles have to pass
along in single file. The red corpuscles move in the central
CIRCULATORY AND RESPIRATORY SYSTEMS 135
axis of the stream ; to the outside there moves a layer of
transparent plasma, and in this the white corpuscles move
along, sticking now and again to the wall ; the outermost
layer of plasma is practically stationary.
If a slight injury is inflicted to the web of the frog, it will
be found that there is a certain reaction on the part of the
tissues to this injury, and such reaction is called " inflamma-
tion." The smaller vessels would dilate, the blood-flow
would quicken in rate, then become slower, and finally
come to a standstill ; the white corpuscles would pass out
in large numbers to the surrounding tissue.
Course of the Circulation. — The general course of the
circulation can be studied by dissection of a dead rabbit
or cat, after a warm solution of gelatin stained with car-
mine has been injected into the arteries. The path and
direction of flow of blood is practically the same in these
animals as in man, except there are a few differences in
the anatomical distribution of the bloodvessels.
In man the blood is pumped from the left ventricle into
the arches of the aorta. From the top of the arch there
arises on the right side the innominate artery, and on the
other side the left common carotid and left subclavian
arteries. The innominate artery soon divides into right
common carotid and subclavian arteries. The common
carotid arteries ascend on each side of the neck, and about
the level of the upper border of the larynx they divide
into internal and external carotid arteries. The external
carotids supply the tissues of the head that are outside the
skull cavity, and the internal carotids enter the cranium,
and are the most important blood-supply of the brain.
The subclavian arteries pass behind the collar-bone to the
armpit, where they are called the " axillary arteries," and
thence are continued as the main arteries of the upper
limb. The blood is returned from the head and neck by
means of the jugular veins ; these join with the subclavian
veins to form the innominate veins, and the right and left
innominate veins unite to form the superior vena cava,
which opens into the right auricles.
136
HYGlKNi:
The aorta courses down the thoracic cavity near the verte-
bral column ; here it gives off a few branches which supply
the wall of the thorax ; one runs under each rib, and a few
twigs to the gullet and bronchi. It passes to the abdominal
cavity, where it gives off a large number of branches.
As soon as it has pierced the diaphragm, it gives off a
large artery called the " oceliac axis," and this subdivides
to branches which supply the stomach, liver, and spleen.
'»--•»
....
• ..
Fio. 04.— SECTION THROUGH A SMALL ABTERV AND Vsnr.
A, Artory lined with flat, scale-like cells; B. clastic membrane; C. mus-
cular coat ; D, connective- tissue coat (the vein is much thinner,
and has less muscle and elastic tissue) ; K, capillary supplying
outer coat with blood.
A little lower down it gives off the superior mesenteric
artery, which divides into a large number of branches to
supply the small and large intestines. At the level of the
kidneys the aorta gives off two renal arteries, one to each
of these organs. It also gives off a branch called the " in-
ferior mesenteric artery/' which supplies the lower part of
the large intestine.
At the level of the fourth lumbar vertebra the aorta
CIRCULATORY AND RESPIRATORY SYSTEMS 137
ends by dividing to two terminal divisions, called the
" right and left common iliac arteries." These run for
a short course in a downward and outward direction, and
divide into, external and internal branches. The latter
supplies the buttocks, the lateral walls of the pelvis, and
back of thigh ; while the former passes down the anterior
FIG. 65. — DIAGRAM OF THE
CIRCULATION.
//', Right ventricle ; P' , pulmonary
artery ; P, lung ; the branches
of the pulmonary artery and
vein, p' , and the air -tubes,
p, are seen entering the lungs ;
h, left auricle ; H, left ventricle ;
A., aorta ; a, carotid arteries to
head ; next to these arise the
subclavian arteries which supply
the upper limbs ; /., intestine ;
k., kidney. The aorta is shown
giving off branches to these
organs. Finally the aorta
divides into branches which
supply the pelvic organs and
the lower limbs. V , vena cava
inferior ; receiving blood from
lower limbs, pelvic organs,
kidneys, and liver, it enters the
right auricle. The portal vein,
L, is shown carrying the blood
from the intestines to the liver ;
I, hepatic vein ; V t hepatic
artery ; t/, superior vena cava
bringing blood from head and
upper limbs to right auricle.
aspect of the thigh, and forms the main blood-supply of
the lower limb. The femoral artery can be felt pulsating in
the upper part of the thigh ; after giving off branches to
the thigh, it winds round the lower part of the shaft of
femur to reach the back of the knee, and thence sends
branches to supply the leg and foot.
138 HYGIENE
Blood is returned from the lower limb and pelvis by
veins which join the external and internal iliac veins ; these
unite in the common iliac veins, and the right and left
common iliac veins join to form the inferior vena cava. This
runs up in front of the vertebral column, and receives
tributaries from the kidneys, the abdominal wall, and
the liver ; it then pierces the diaphragm, and after a very
short course within the thorax it enters the right auricle.
The veins from the intestines do not enter directly into the
inferior vena cava. Blood from the small intestine and
parts of the large intestine is drained into the superior
mesenteric vein ; the blood from the lower part of the large
intestine is carried along the inferior mesenteric vein, which
opens into the splenic vein. The superior mesenteric and
the splenic veins unite to form the portal vein, which enters
the liver, and there breaks up into a number of capillaries,
which reunite to form the hepatic veins, and these we
have previously seen to join the inferior vena cava, just as
it pierces the diaphragm.
The superior and inferior venae cavae open into the right
auricle, and from thence the blood passes to the right
ventricle, which pumps it along the pulmonary artery to
the lungs, whence, after traversing their capillaries, it
reaches to the left auricle. Then it passes through the
mitral orifice to the left ventricle, which by its contraction
forces it along the aorta.
The Beat of the Heart and Cardiac Cycle. — You should
study the contraction of the various parts of the heart in
an animal. This may very well be done in the case of a
frog. The anatomy of the heart of this animal differs to
some extent from that of the mammalian heart, but it will
serve very well to study the co-ordinate contraction of its
different parts.
Obtain a frog, flex its head, and then push a stout pin
into the space separating the base of the skull and the
upper part of the spinal cord. Turn the frog on its back,
and fix it to a cork tray by passing pins through its four
CIRCULATORY AND RESPIRATORY SYSTEMS 139
legs. Now take a pair of scissors and dissecting forceps,
cut through the skin covering the chest, and remove the
breast-bone. The heart will now be exposed enclosed in
the pericardium, which in this animal is a thin membrane
and should be removed with care. Make a careful study
of the anatomy of the frog's heart ; the veins conveying the
blood to the heart will be seen to end in a small chamber
called the " sinus venosus." Note also the auricular portion
of the heart divided by a vertical septum into a right and
left half. The ventricular portion will be seen as a single
conical structure, not divided into two, as in the case of
mammalia. Now study the sequence of contraction of
the various chambers of the heart. Blood will be seen
flowing along the veins to the sinus venosus and auricles ;
the sinus venosus will then contract, followed by a syn-
chronous contraction of the auricles, and later by contraction
of the ventricle. It is thus seen that each heart-beat in
all animals is composed of co-ordinate contraction of
various parts of the heart. The necessary stimulus that
excites the muscles of the heart to activity is generated
in the region of the mouths of the great veins ; it passes to
the auricles and causes them to contract ; then it is con-
ducted to the ventricles along certain special bands of
muscle connecting the auricles and ventricles ; finally the
ventricles are excited to contract. For a short period after
contraction of the ventricle the whole heart remains at rest.
The period of contraction of any portion of the heart is
called its systole, while the period of relaxation is called
diastole, and thus we speak of auricular systole and dias-
tole, and ventricular systole and diastole. The series of
changes that take place in the heart with each inflow and
output of blood is called the cardiac cycle. Above we have
only described the various phases of contraction of the
heart ; let us discuss the flow of blood through the heart,
and the relation of the time of opening and closing of the
different valves of the heart to the periods of the cardiac
cycle. The following description is applicable to mam-
140 HYGIENE
malian hearts : For nearly half a second after the contrac-
tion of the ventricle the whole musculature of the heart
is in a condition of relaxation, and its cavities are being
filled with blood. Blood is pouring into the right auricle
along the superior and inferior venae cavae, and into the left
auricle along the pulmonary veins. The auriculo-ven-
tricular valves of both sides are in apposition since the last
ventricular systole. As the auricles are filled, the pressure
of the blood on the auricular side of these valves becomes
greater than on the ventricular side ; consequently the
valves open, and blood can now pass from the auricles to
the ventricles. Auricular systole now sets in, and the
contents of the auricles are pushed through the auriculo-
ventricular openings into the cavities of the ventricles.
As the ventricles are filled with blood, the valve cusps float
on its surface, and a fifth of a second after contraction of
the auricles the ventricles enter into systole. During this
period the pressure inside the ventricular cavities is greatly
increased, and results in a closure of the auriculo-ventricular
valves. Since the last period of contraction of the ven-
tricles the semilunar valves of the pulmonary artery and
aorta have been in apposition ; very quickly after the
closure of the auriculo-ventricular valves the pressure of
the blood inside the cavities of the ventricles becomes
greater than that in the pulmonary artery and aorta, and
this results in the opening of the semilunar valves. When
the cavities of the ventricles have been emptied, they enter
into diastole, and then the pressure of the blood in the
pulmonary artery and aorta becomes greater than that
in the ventricles ; consequently the semilunar valves are
closed and the whole heart is at rest. The above changes are
again repeated. Thus, the auriculo-ventricular valves of
both sides open at the beginning of ventricular diastole, and
close at the beginning of ventricular systole ; while the
semilunar valves of the aorta and pulmonary artery open
very early in ventricular systole, and close at the beginning
of ventricular diastole.
CIRCULATORY AND RESPIRATORY SYSTEMS 141
Causation of the Heart-Beat. — The cause of the heart-
beat has naturally constituted one of the fundamental
objects of physiological inquiry. In the heart-heat we
have really a contraction of a special form of muscle.
Physiologists first studied the structure and properties of
voluntary or skeletal muscle, and the facts which they
ascertained about skeletal muscle were applied to cardiac
muscle. One of these properties is that the contraction of
voluntary muscle within the body depends upon the
integrity of its nerve-supply ; hence the older physiologists
said that the heart-beat depends upon the integrity of,
and arises in the nerve cells of, the heart. This statement
is the basis of the nervous or "neurogenic theory of the
heart-beat."
A special study was then made of the heart muscle, and
its properties were found to differ greatly from those of
voluntary muscle. Heart muscle was found to be auto-
matic— that is, capable of generating its own stimuli —
when separated from all parts of the body. Some time
after death a heart can be resuscitated by transfusing it
with warm saline, and in the embryo of certain animals
the heart has been seen beating before any growth of
nervous tissue has reached it. Hence the more modern
view on this subject is that the stimulus which excites the
heart to contraction arises in the musculature of the heart
itself. This is called the " myogenic theory of the heart-
beat."
The Frequency of the Heart-Beat. — You can count the
number of times the heart beats per minute by feeling the
pulse at the wrist. In a normal adult, when resting, the
pulse-rate is about 60 to 70 per minute. In young infants
the pulse-rate is much faster, about 130 per minute.
The rate of the heart-beat is accelerated under various
conditions : nervous excitement will cause the heart to
beat quickly, any form of fever is accompanied by an
increased pulse-rate, and exercise causes great acceleration
of the heart.
142 HYGIENE
Time Relations of Systole and Diastole. — The duration of
the separate phases of the heart-beat depends, naturally,
on the rate of the beat. Assuming a pulse-rate of 70 per
minute, the average duration of the different phases may
be estimated approximately as follows :
Second.
Ventricular systole .. ..^ .. .. = 0'379
Ventricular diastole and pause . . . . = 0-483
Auricular systole = O'lOO
Auricular diastole and pause = 0*762
When the rate of the pulse is increased, it is the diastolic
and pause periods that are shortened ; and since it is during
these periods that the musculature of the heart receives its
nourishment, it is clearly seen how dangerous it is for the
heart to continue to beat very rapidly during a fever or
overstrain.
The Heart-Sounds. — Two sounds are produced during
each beat of the heart. These sounds will be readily heard
if you place your ear against a friend's chest over the region
of the left nipple. The first sound has a deeper pitch and
is longer than the second, and their relative pitch and dura-
tion are represented frequently by the syllables ** lubb-
dup." The first sound is heard at the beginning, and the
second sound at the end, of the ventricular systole.
If the heart of a sheep or ox be cut out immediately after
the death of the animal, the first sound of the heart will be
heard as long as the heart muscle continues to contract.
There are two factors wliich .play a part in the formation of
the first sound : the contraction of cardiac muscle and
the closure of the auriculo-ventricular valves both set up
vibrations which give rise to the first sound.
The second sound is caused by the tension of the semi-
lunar valves. As the ventricles cease to contract, eddies
of blood shut the valves. The greater pressure of the blood
on the arterial side of the semilunar valves at the beginning
of ventricular diastole throws the valves into a state of
tension, and the vibrations set up by it are the cause of
the second cardiac sound.
CIRCULATORY AND RESPIRATORY SYSTEMS 143
Blood-Pressure. — When an artery is cut, the outflow of
blood is not uniform and smooth, but takes place in jerks
which correspond to each beat of the heart. Moreover, the
blood spurts out with considerable force, which, although
it is greater at each jerk, is still persistent and large between
the jerks. The obvious conclusion to be drawn from the
above observation is that the blood in the artery is always
under considerable, though variable, pressure. This pres-
sure is called arterial blood-pressure.
The smallest arterioles and capillaries offer a consider-
able frictional resistance to the flow of blood through them
into the veins. This is generally called " peripheral
resistance." Owing to this resistance, of the total amount
of blood forced into the arteries at each beat of the heart
only a portion can during the actual beat, apart from
the pause between it and the next beat, pass on into the
veins. The remainder is lodged in the arteries. This
volume of blood distends the arteries, and in between the
beats the elastic wall of the arteries recoils and presses
forward the blood ; hence there is a storing-up of the force
of the heart-beat by the elasticity of the arterial walls.
We have seen that the flow in the arteries is intermittent,
but in the veins the blood- flow would be continuous. This
is explained by the fact that the arterioles store up the
force of the heart-beat by the elasticity of their walls, and
during diastole the blood- flow in the veins is continuous.
As the blood passes along the arteries, capillaries, and
veins, there is a continual fall of blood-pressure, because the
force of the heart and the elastic recoil of the arteries are
used up to overcome the resistance to the flow of blood.
The greater the resistance that is overcome, the greater
the fall of pressure. The greatest amount of resistance is
offered by the capillary area, and hence the greatest fall of
blood-pressure occurs in this area.
Hence the blood-pressure is highest in the arteries, where
it is intermittent, and lowest in the veins, where the flow of
blood is continuous.
ANT. r v.
Fio. 66.— VENTRAL DISSECTION OF THE RABBIT (LEPUS), TO SHOW
MAIN ARTERIAL AND VENOUS VESSELS.
[Continued at foot of page 145.
CIRCULATORY AND RESPIRATORY SYSTEMS 145
The arterial blood-pressure can be measured very easily
by an instrument called a " sphygmometer." This consists
of a broad rubber bag enclosed in a leathern armlet. The
armlet is strapped round the arm above the elbow. The
rubber bag is connected with a pressure gauge or mercurial
manometer, and with a syringe-bulb. The pressure is
raised in the bag by pumping air into it, a finger is
placed on the radial artery at the wrist, the pressure in
the bag is raised so that it is able to prevent the pulse-wave
travelling to the wrist, and the pressure which is just able
to do this gives the measure of the blood-pressure.
Velocity of Blood. — The rate at which the blood flows
varies in different parts of the vascular system. In order
that there should be no stasis of blood hi any part of the
body, the same amount of blood must enter and leave the
heart in a certain interval of time. Therefore the rate of
flow in any set of vessels will vary inversely as the area of
FIG. 66 continued:
The arteries are represented in line, and the veins in solid black. The
ventral portion of the pelvic and pectoral girdles has been re-
moved, as well as the body wall and ribs. The viscera have been
turned overto the animal's right. AO. A., Aortic arch ; ANT. F. V.,
anterior facial vein ; ANT. EP., anterior epigastric ; ANT. M., an-
terior mesenteric artery ; AZ. V., azygos vein ; BE. A., brachial
artery ; BR. V., brachial vein ; G. G. A., common carotid artery ;
C(E., ooaliac artery ; CM., caecum ; CM. I., common iliac artery ;
CM. 1. V., common iliac vein ; D. (to reader's right), diaphragm ;
D. (to reader's left), duodenal branch of cceliac artery ; DO. AO.,
dorsal aorta ; DU., duodenum ; D-L. A. and V., dorso-lumbar
artery and vein ; EX. G. A., external carotid artery ; EX. J. V.,
external jugular vein ; EX. I. A. and V., external iliac artery and
vein ; F. A. and V., femoral artery and vein ; G. A., gastric artery ;
G-B., gall-bladder ; H., hepatic artery ; IN. C. A., internal carotid
artery ; INT. I. A. and V., internal iliac artery and vein ; IL., ileum,
or small intestine ; INT. A., intercostal artery ; INT. V., inter
costal vein ; INN. A., innominate artery ; INT. J., internal jugular
vein ; L. A., laryngeal artery ; L. L. L., left lobe of liver ; M. 8.,
median sacral vein ; the artery of the same name is immediately
to the left of it ; 0. A. and V., ovarian artery and vein ; P. A., pul-
monary artery ; P. M., posterior mesenteric artery ; P.-G., post-
caval vein ; POS. EP., posterior epigastric artery ; P08. F. V.,
posterior facial vein; B., rectum; T., trachea; V. A., vertebral
artery. The pre-oaval veins are not lettered, but they are the two
veins entering the heart from above, and formed by the union of
BR. V.&ndEX.J.V.
10
146 HYGIENE
cross-section of the vessels. When a river passes through a
gorge its velocity is very great, but when it widens out
in the plains the rate of flow is greatly diminished, and
this is because, if there is increased area of cross-section in
the river-bed, a smaller velocity will allow a volume of
water to pass which in the narrow gorge would require a
greater velocity for its passage in the same interval of time.
The same principle holds with the blood-flow. The area of
cross-section of an artery is always smaller than the total
area of cross-section of its branches, and, similarly, the total
cross-section of tributaries of a vein is always greater than
that of the vein itself.
As we pass from the aorta to the capillaries, there is
greater and greater increase in the area of cross-section of
the bloodvessels, and in the capillaries we have the greatest
cross-area. As the capillaries join into veins, and the
smaller veins into larger veins, the bed again becomes
narrowed ; finally, in the two venae cavae the capacity is
not much greater than that of the aorta.
In the aorta the channel is narrow and the flow fast ;
through the capillaries the blood moves slowly, for here
the total bed through which the stream flows is far wider
than that afforded by the aorta. As the capillaries unite
to form veins, and these to form larger veins, the bed
again becomes narrowed, and hence the velocity increased.
Relation of Circulation to the Nervous System.
The amount of blood passing through an organ is pro-
portional to the amount of physiological activity going on
in that organ. The total amount of blood that is normally
present in the body would not be sufficient to supply ade-
quately all the organs if they were in an active condition at
the same time. Since it is absolutely necessary that the
parts of the body that are in activity should receive a good
supply of blood, Nature has elaborated effectual means of
governing the blood-supply to various organs according to
their physiological requirements. This is done by increas-
CIRCULATORY AND RESPIRATORY SYSTEMS 147
ing or decreasing the rate and strength of the cardiac beats,
and varying the calibre of the bloodvessels. So that, if
any part of the body requires a greater amount of blood,
it will receive it by a dilatation of its own bloodvessels
and constriction of vessels supplying the parts that are not
in activity ; and if this will not suffice, the heart will beat
quicker and stronger, and still further increase the amount
of blood passing through the site of activity.
Vasomotor Nerves. — When describing the structure of
arteries, we said that their walls were made up of muscular
elastic tissue. The muscular tissue contracts and relaxes
like all forms of muscle, and these phenomena are under
the influence of a special set of nerves, which are called the
" vasomotor nerves." They run along the course of the
arteries, and end in a network of filaments in contact with
the muscle cells. These nerves emerge by the anterior
roots of the spinal nerves, and have their origin in the
spinal cord. The vasomotor nerves are of two kinds —
vaso-constrictor and vaso-dilator. The vaso-constrictor
nerves cause contraction of the muscular coat of arteries,
and therefore a decrease in their lumina ; while the dilator
fibres cause relaxation, and thus bring about an increase
in the calibre of the arteries.
All the vaso-constrictor nerves arise from the nerves
which issue from the spinal cord in the thoracic and upper
lumbar regions. From the spinal cord they pass to the
sympathetic system, which is a series of nerve ganglia
connected by a nerve cord, lying in front of the vertebral
column, and from the ganglia the fibres are carried on to
the wall of the bloodvessels.
Vaso-dilator fibres are present in most of the cranial and
spinal nerves. When certain precautions are taken to
prevent a constrictor effect, the stimulation of nerves con-
taining these fibres brings about vaso-dilatation of the
organs which they supply.
Vasomotor Centre. — The vaso-constrictor fibres are gener-
ally in tonic activity, while the vaso-dilator fibres are not
148 HYGIENE
in tonic activity ; in other words, impulses are continually
passing along the vaso-constrictor fibres, keeping the
musculature of the arteries in a certain state of tonic
contraction, while such impulses do not continuously travel
along the vaso-dilator fibres, but only at certain special
periods. All the vaso-constrictor fibres are in connection
with a special group of nerve cells situated in the lower
part of the medulla oblongata of the brain, and this group
of cells is called the vasomotor centre. The vaso-dilator
fibres, on the other hand, are not connected with any special
group of nerve cells, and, as said above, they are not in
tonic activity. This generation and passage of impulses
from the vasomotor centre along the vaso-constrictor
nerves are the factors that govern the relative amount of
blood-flow through the different tissues of the body, and
it is by such means that the parts of the body which are in
physiological activity receive a greater blood-supply at
the expense of such tissues as are not in activity. This
greater blood-supply is obtained by either stimulation of
the vaso-dilator fibres or inhibition of the vaso-constrictor
fibres which supply the active organ, and by stimulation of
the vaso-constrictor fibres supplying the rest of the body.
Thus, during mental activity, in order to have a good supply
of blood to the brain, there is constriction of the arteries
of the other parts of the body.
During digestion there is great activity going on in the
stomach and intestines, resulting in dilatation of their blood-
vessels, and increase in the amount of blood in the ab-
dominal viscera. Consequently not so much blood is left
to supply the brain and other tissues ; hence mental work
is performed with difficulty after heavy meals.
Similarly, during muscular exercise there is greater flow
of blood to the muscles.
Various emotional conditions influence the activity of the
vasomotor centre ; thus, fear or fright causes constriction
of the peripheral vessels, while feelings of shame or embar-
rass ment cause vaso-dilatation.
CIRCULATORY AND RESPIRATORY SYSTEMS 149
The vasomotor nerves also counteract the effect of gravity
upon the weight of the blood, and when the body is in the
erect posture the constriction of the bloodvessels prevents
the stagnation of blood in the arteries of the lower limbs
and abdomen. When, however, this influence is removed
the bloodvessels dilate, and the stagnation of blood in the
abdomen and lower limbs is such that the amount going to
the brain is so diminished that it results in fainting. It is
evident that the rational treatment of such a condition is
to lay the patient flat on the ground, or place him with
his feet up in the air, and the force of gravity will then
help the flow of blood to the brain.
Nerve-Supply of the Heart, and its Actions. — The heart
is richly supplied with nerves, which arise from two sources
— namely, from the vagi and the sympathetic systems.
The vagi, or tenth cranial nerves, arise from the medulla.
One runs on each side of the neck between the carotid
artery and the internal Jugular vein ; they both run through
the thorax, and pass to the abdomen, where they end by
joining various abdominal nervous plexuses. During their
course in the neck each vagus gives off three cardiac
branches, which pass down to supply the heart.
The sympathetic nervous chain will be found on each side
of the neck behind the carotid artery, and three cardiac
branches are given off on each side, which also go down to
supply the heart. Stimulation of the vagi causes the heart
to beat more slowly, or stop for a short time altogether.
The cardiac fibres of the vagi are connected with a group
of nerve cells in the medulla oblongata, called the " cardio-
inhibitory centre," and this centre is always in tonic
activity ; this is proved by the fact that if the vagi be cut
the heart will beat more rapidly.
Stimulation of the sympathetic supply of the heart will
cause it to beat more rapidly and more forcibly ; hence their
influence is entirely opposite to that of the vagi.
There are also two nerves, one on each side, which
carry impulses from the heart to the medulla. In part of
150 HYGIENE
their course the fibres ascend in the vagi. If these fibres
are separated from the vagi and stimulated, the vasomotor
centre will be depressed, and consequently there will be
great vaso-dilatation. The blood will escape more easily
to the capillaries, and the heart, owing to the consequent
fall of pressure in the aorta, expels the blood at each
systole with less effort.
The medulla oblongata has complete nervous control
over the circulation. The heart can be made to work more
quickly or slowly, and each organ can obtain the blood it
requires during activity or rest.
RESPIRATION.
Respiration in its widest sense is the means by which the
tissues of the body gain the oxygen they require, and
eliminate the carbon dioxide they produce.
Oxygen must be supplied to the protoplasm in order that
the energy of life may be maintained.
In the lowest animals, which are made of a single cell; no
special mechanism of respiration is needed ; the oxygen
diffuses in and the carbon dioxide diffuses out through the
general surface.
In some multicellular animals — e.g., sea-anemones —
oxygen is obtained by diffusion through the ectoderm from
the surrounding water. In animals of more complex
structure special adaptation for this important process
becomes necessary, and respiration may be divided into
two stages :
1 . External respiration is the means by which the gaseous
exchange takes place between the air or water and the
circulating fluid.
2. Internal respiration is the means by which the inter-
change takes place between the circulating fluid and the
cells of the tissues.
In the lower kinds of worms gaseous exchange takes place
almost entirely by the skin, under which plexuses of blood-
vessels often exist.
CIRCULATORY AND RESPIRATORY SYSTEMS 151
In crayfish there are special organs called " gills," where
the circulating fluid absorbs oxygen from the surrounding
water.
The bodies of insects are traversed by minute tubes,
which carry air from the outside to the tissues within.
Fishes and other water animals possess gills. By means
of these organs water is rhythmically swept over these
membranous sheets of tissue, which contain networks of
capillaries full of blood.
The respiratory organs of birds are complicated ; in
addition to small lungs they possess large and membranous
air -sacs. These sacs surround the lungs, and extend
between the organs of the body. They are connected with
the windpipe and its branches, and with the hollow
medullary cavities of the bones.
In man and the higher animals we have in the lungs
complicated organs, specially devised for the absorption of
oxygen and the elimination of carbon dioxide.
Physiological Anatomy of the Respiratory Apparatus.
In man the respiratory apparatus consists of the nose,
pharynx, larynx, trachea, bronchi, bronchioles, and air-
sacs.
The nose is a cavity that is bounded above by the bone
of the skull, below by the soft and hard palate, and laterally
by the upper jaw-bone. The nasal cavity is divided into
two by the nasal septum, which is made up of a framework
of bone covered by a mucous membrane.
The upper part of the nose is covered by a special form
of mucous membrane, which constitutes the organ of smell.
The remaining surface of the nasal cavity is lined by
ciliated epithelium, and the air in its passage to the lungs
comes in contact with this, and is filtered free from dust
particles and bacteria. Hence it is important that one
should always breathe by the nose, for the air is rendered
warm and moist, and is also purified to a large extent from
bacteria and dust particles.
152
HYGIKNK
Ask a butcher for the head of a sheep which has
been sawn through the middle line, and study in it the
general anatomy of the nasal cavities.
The structure of the pharynx
has been described in Chapter
III. It is divided into two
portions by the soft palate —
an upper nasal pharynx, and
a lower oral pharynx, whirh
is a passage common to food
and air.
At the lower end of the
pharynx there com men < •
two tubes, the oesophagus or
gullet behind, and the trachea
in front. At the upper part
of the trachea is the larynx,
which is a cartilaginous box
specialized for the production
of voice. In order to study
the structure of the trachea,
larynx, and lungs, ask the
butcher for the pluck of a
sheep.
For the structure of nose
and pharynx, study Fig. 35,
etc.
The trachea, or windpipe,
icnoscopic STBUC-
w TRACHEA.
A. Mucous membrane formed of
ciliated epithelium ; li, layer
of loose connective tissue ;
C, layer of yellow elastic fibres ;
D, submuoous coat made up
of loose connective tissue, ana
containing mucous glands;
E, layer of involuntary mus-
cular tissue ; F, supporting
cartilage.
will be found to be formed of
C -shaped rings of cartilage
covered within by mucous
membrane ; the rings are in-
complete behind where the
trachea rests on the gullet, which in its turn lies on the
vertebral column. Owing to the rings of cartilage the
trachea remains open always, and cannot be compressed
except by considerable force. The rings of cartilage im-
CIRCULATORY AND RESPIRATORY SYSTEMS 153
perfect behind are completed by a band of non- striated
muscle. The cartilage rings themselves are embedded in
and connected together by connective tissue. The mucous
membrane is lined by ciliated epithelium resting on a base-
ment membrane ; beneath it there is a layer of elastic tissue
and a deeper layer of loose connective tissue containing a
large number of mucous glands.
Bronchi and Bronchioles. — The trachea divides below
into right and left bronchi ; one goes to each lung. The
bronchi are similar in structure to the trachea.
Bronchial tubes are formed by the subdivision of the
bronchi ; they are in structure similar to the bronchi, but
pieces, not rings, of cartilage strengthen the walls, and
there is a complete ring of muscular tissue.
The bronchial tubes subdivide into bronchioles, and these
pass to all parts of the lung, and end finally in the air-sacs.
The Structure of the Lung. — Each bronchiole ends at
length in an elongated dilatation about •& m°h in diameter
on an average, and known as an infundibulum. The wall
of an infundibulum sends flattened projections into its
interior, and thus forms a series of thin partitions by which
the cavity of the infundibulum is divided up into a large
number of little sacs or chambers. These sacs are the
alveoli, or air-sacs.
The very thin walls which separate these alveoli arc
supported by much delicate and highly elastic tissue, and
carry the wide and close-set capillaries into which the
ultimate ramifications of the pulmonary artery pours its
blood.
Thus the blood contained in these capillaries is exposed on
both sides to the air, and separating the blood from the
air we have only two layers of endothelial cells ; through
these the gaseous interchange takes place. The air-sacs
are bound together by connective tissue to form lobules, and
these are further bound to form lobes. In the human
subject there are three lobes in the right lung, and two in the
left lung.
154
HYGIENE
Circulation of Blood through the Lungs. — Venous blood
is returned to the heart from all parts of the body by the
superior and inferior venae cavae. It first of all reaches the
right auricle, and from there it passes through the right
auriculo-ventricular orifice to the right ventricle. The
pulmonary artery arises from the right ventricle, and carries
Fio. 68. — MICROSCOPIC SECTIOK THROUGH A FRAGMENT OF THE LUNG.
A, Bronchial tube lined with ciliated cells ; B. layer of unstriped muscle ;
C, mucous gland with duct; D. cartilage stiffening the walls;
K, branch of pulmonary artery ; F, air-cells in which the bronchial
tubes end.
the venous blood to the lungs. It divides into branches
which pass to the lobes and lobules, and finally ends in a
network of capillaries surrounding the wall of each air-
sac. The tissue of the lung itself is supplied with some
arterial blood by branches of the aorta — the bronchial
arteries.
The respiratory movements draw air to the lungs until
the cavities of the air-sacs are filled with air, and in their
CIRCULATORY AND RESPIRATORY SYSTEMS 155
walls the venous blood is contained in the capillaries, and
separating the two is nothing but the thinnest membrane,
composed of two layers of flat pavement epithelial cells.
Here the interchange of gases takes place ; the blood gives
off carbonic acid, and absorbs oxygen from the air within
the air-sacs.
These capillaries unite to form venules, and the blood re-
enters the heart by two pulmonary veins from each side,
four in all, which open into the left auricle.
The blood during its passage through the lungs has
changed greatly in colour. As it enters the lung it is
bluish and dark, while on its return its colour has changed
to a bright red. This is due to the oxygenation of the
haemoglobin. Oxyhaemoglobin is bright red, while reduced
haemoglobin is very dark red in colour.
Since the capillary area of the lungs is less than that of
the systemic system, the peripheral resistance must also
be less ; and therefore the pressure of the blood in the
pulmonary system is smaller, but the velocity is greater,
than in the systemic system.
In order that the blood may continually acquire oxygen
and yield up carbon dioxide, it is necessary that the air in
the lungs should be renewed. This is effected by the act
of respiration, which occurs about fifteen to twenty times
a minute.
The Thoracic Cavity. — The thorax is the part of the body
in which the lungs and heart are situated. It also contains
the great vessels entering and leaving the heart and lungs ;
the gullet passes through it on its way to the abdomen.
The whole structure is supported by a bony framework ;
this is made up of the backbone or vertebral column
behind, the breast-bone or sternum in front, and the ribs
pass obliquely between these structures.
Various muscles take origin from, or are inserted into the
outer surface of the ribs and sternum. Some come down
from the neck, others pass to the abdominal wall or upper
limbs, while behind the great muscles of the back are
156 HYGIENE
situated. On the outer surface of these muscles there lie
subcutaneous tissue and the skin. In between the ribs
there are two thin sheets of muscle called the " internal
and external intercostal muscles."
The contraction of all the muscles attached to this bony
framework either tend to expand or diminish the dimensions
of the thoracic cavity ; the former are called " inspiratory "
and the latter " expiratory " muscles.
The thorax is bounded above by the connective tissue
which passes from the neck on the great vessels, gullet, and
windpipe, as they enter it. It is separated from the
abdominal cavity by a muscular partition called the
41 diaphragm."
The pericardium and its contents more or less divide
the thoracic cavity into two, and each is occupied by
a lung, covered by a glistening membrane called the
4< pleura."
The pleurae are two membranous sacs, each surrounding
a lung. It must not be thought that each lung is placed
inside each sac, but the walls of each sac are in apposition,
and the whole structure then surrounds a lung. Thus the
whole lung is surrounded by a pleura, except in a small area
on the inner surface, where the bronchi and bloodvessels
leave and enter it ; this area is called the " root of the lung."
It is seen that the cavities of the pleural sacs are in normal
persons only potential spaces. Since the lungs are always
in a condition of distension, and fill all the available space
in the. thoracic cavity, the outer layer of the pleura becomes
attached to the inner surface of the thoracic wall, while the
inner is intimately connected with the outer surface of the
luii r. The surfaces of the pleurae which are in contact with
each other are smooth and glistening ; they also secrete
a small quantity of fluid, which lubricates the surfaces, and
hence the alternate expansion and contraction of the lungs
are allowed to take place with the least possible amount of
friction. When the pleurae become inflamed, the surfaces
become sticky, and may result in adhesions ; the expansion
CIRCULATORY AND RESPIRATORY SYSTEMS 157
of the corresponding lung would be limited, and the
inflammatory stage accompanied by pain.
The lungs may be looked upon as two large mem-
branous, elastic sacs, the interior of which communicates
freely with the air through the trachea, while the outside
is protected from atmospheric pressure by the walls of the
chest. When the chest is opened, the lungs are found
shrunk up and far smaller than the thoracic cavity.
The atmospheric pressure on the interior surface of the
lungs expands these structures under normal conditions
until they fill every part of the thoracic cavity not occupied
by other organs. When the dimensions of the chest cavity
vary, that of the lungs will follow suit, until they again
fill up every part of the thorax. If the thoracic cavity
communicates with the outside air, or if the wall of the
lung is punctured so that air can communicate with the
pleural cavity, the pressure is equalized on the inner and
outer side of the sac, and the lungs, owing to their elasticity,
at once collapse.
The Normal Position of the Thorax — Inspiration and
Expiration. —The size of the thorax continually changes
with the respiratory movements. The position taken at the
end of a normal expiration may be regarded as the normal
position of the thorax, and in this position all the muscles
of respiration are at rest. Any enlargement of the thorax
from this position constitutes an active inspiration, while
any decrease in the size of the thorax would be an active
expiration. It is easily seen how after an active inspiration
the thorax may, by its own elasticity and without any
muscular effort, return to its normal position, giving what
may be called a " passive expiration."
Normally the respiratory movements consist of active
inspirations followed by passive expirations.
Respiratory Movements. — Air is constantly renewed in
the air-sacs of the lung by alternate expansion and decrease
in the cavity of the thorax.
It is readily seen, on studying the shape of the thorax, that
158
HYGIENE
expansion of its cavity might occur in three directions —
vertical, antero-posterior, and from side to side.
An increase in the vertical diameter can only be brought
about by contraction and descent of the diaphragm ; hence
the importance of abdominal breathing, because it is the
only way by which the vertical diameter of the thoracic
cavity may be increased. In the adult the only way in
Fio. 00. — DIAGRAM TO SHOW BOW, AS THB RIBS MOVE UPWARDS, THE
STERNUM GOES FORWARD. AKD so INCREASES THE Sirs OF THB
THORAX DURING INSPIRATION.
1, Spinal column ; 2. sternum ; 3, first rib ; 4. seventh rib; 2', 3', 4'. posi-
tion in inspiration ; a, 6. indicate the extent of movement.
which aeration of the apices of the lungs can take place
is by abdominal breathing. Consumption generally starts
at the apices, and lack of aeration is one important
predisposing factor. The germs which cause this disease
usually invade these regions.
The diaphragm is prevented from pulling inwards the
lower ribs by the action of antagonistic muscles, which
draw the same ribs outwards. The increase in the antero-
CIRCULATORY AND RESPIRATORY SYSTEMS 159
posterior diameter is caused by the lifting up of the ribs,
which run, in the position of rest, in an oblique direction
around the thorax. Each pair of ribs forms one ring of
the thoracic cage, and each ring slopes downwards. By
pulling each ring into the horizontal position, the thorax
must be made larger and the sternum thrust forwards.
The increase in the side-to-side diameter of the thorax is
due to the obliquity of the axis around which the ribs move.
—A
FIG. 70. — FIGURE SHOWING THREE RIBS, THEIR ATTACHMENT TO SPINE
AND STERNUM, AND THE MUSCLES COMPLETING THE THORACIC
WALL.
A, Sternum ; B, rib cartilage ; 0, vertebral column ; D, E, attachment
of ribs to spine ; F, rib ; G, H, outer and inner intercostal muscles.
The ribs are fixed to the vertebral column by means of
two joints. The head of the rib articulates with the bodies
of the vertebrae, while the capitellum is jointed to the top
of the transverse process. These two regions are the most
fixed points in each rib, and therefore movement takes
place around the line which joins these two points. The
line is set obliquely, and the increase in the side-to-side
diameter of the thorax depends upon this obliquity.
A combination of abdominal and costal movements
160
HYGIENE
results in expansion of the thoracic cavity in all directions,
and this type of breathing should always be practised.
When the diaphragm descends and the ribs ascend, air
rushes down the trachea and bronchi, and distends each
lung so as to fill up the enlarged thoracic cavity.
The descent of the diaphragm is necessarily accompanied
Fio. 71.— THE DOME-SHAPED DIAPHRAGM.
A, Aorta ; B. oesophagus ; C, vena cava inferior ; D, muscular pillan
of the diaphragm arising from the spinal column; E, F, ribs,
and O, sternum, sawn through so as to allow removal of the front
of the thorax; H, hind, and A, front, muscular sheet, and /, central
tendinous part, of the diaphragm.
by a descent of the liver and other abdominal contents.
This causes an increase in the intra-abdominal pressure,
which is associated with a decrease in the thoracic pressure.
It is readily understood that during inspiration there
would be a greater flow of blood from the abdomen into
the thorax. Since blood is sucked into the right heart
in great amount, and the capillary area of the lungs is
CIRCULATORY AND RESPIRATORY SYSTEMS 161
increased, during an inspiratory movement, there is greater
volume both of air and blood drawn into the lungs, and
hence the gaseous exchange between them is favoured.
The Volume of Air respired in the Capacity of the Lungs.
— The volume of air respired varies, of course, with the
extent of the movements and the size of the individual.
The amount of air that is taken in and given out at each
normal breath is for an adult man about 500 c.c. (a little
less than a pint), and is called the tidal air.
The amount of air that can be breathed in over and above
the tidal air by the greatest possible inspiration measures
about 1,600 c.c., and is called the complemental air.
By the term supplemental air is meant the amount that
can be breathed out, after a quiet expiration, by the most
forcible expiration. This is about 1,600 c.c.
By " vital capacity" is meant the amount of air that can
be breathed out by a most forcible expiration after making
the deepest possible inspiration. It is made up of tidal,
complemental and, supplemental air. It measures in an
adult man about 3,700 c.c.
After the most forcible expiration there still remains
about 1,000 c.c. of air, which is called the " residual air."
During natural quiet respiration there are within the
lungs about 2,600 c.c. of air, and at each inspiration
500 c.c. of air is taken into the trachea and larger bronchial
tubes. The actual ventilation of the air within the alveoli
of the lungs depends upon the size of the bronchial tree.
It has been found that the area of the bronchial tree
amounts to 140 c.c. — therefore 360 c.c. of air actually reach
the alveoli during each quiet inspiration ; and since there is
already present in the lungs about 2,600 c.c., the ventilation
would be -&6o°a=£ approximately.
Inspired and Expired Air. — Expired air differs from the
air inspired in the following manner :
Whatever the temperature of the inspired air may be,
that of the expired air tends to be nearly as hot as the
blood — that is, it has a temperature about 98'6° F., or 37° C.
11
162 HYGIENE
However dry the inspired air may be, the expired air is
nearly or quite saturated with aqueous vapour. This water
is derived from the outer air-passages, so that the inspired
air is saturated with aqueous vapour before it reaches the
alveoli of the lungs. This is more effectually done when
the air is taken in through the nostrils.
The expired air differs in chemical composition from
inspired air.
In 100 volumes we find in inspired or atmospheric air —
Oxygen 20-96
Nitrogen 7940
Carbon dioxide 0-04
Water variable
In 100 volumes of expired air we find, on the average —
Oxygen 16-40
Nit'rogen 79-19
Carbon dioricie 4*41
Water saturated
Thus, speaking roughly, in air that has been breathed
once the amount of nitrogen remains constant ; there is a
great increase in the amount of aqueous vapour, the amount
of carbon dioxide has iiiOTMHed 4 per cent., and the amount
of oxygen lias decreased about 4 per cent.
Experiment. — Buy some lime-water from a chemist,
place at the bottom of a bottle, and shake it up with the
air above. The lime-water remains clear. Now place a
glass tube into the lime-water, and blow through it. The
expired air will immediately make the li me- water milky ;
this is due to the fact that the carbonic acid of the expired
air combines wfth the lime-water to form carbonate of
lime, which is insoluble.
You can prove the presence of moisture in expired air by
simply breathing on to any cold surface, when the water
vapour will be condensed, and will appear as small droplets
of water.
Gas Analysis. — A specimen of air may be obtained by
taking a special form of tube, and filling it with acidulated
CIRCULATORY AND RESPIRATORY SYSTEMS 163
water. On opening one of the taps attached to it, the
water will run out and the air will rush in ; the taps are then
closed. The chemical composition of the sample can be
ascertained by an apparatus which is diagrammatically
shown in Fig. 72. A is a graduated mercurial pump, and
FIG. 72. — DIAGRAM OF APPARATUS USED TO DETERMINE THE
COMPOSITION OF AIR.
therefore the contents of the tube can be drawn into A
by lowering its distal limb, L. The amount of air taken
is measured. By arranging the taps B and C, and
raising L, the contents of A are pushed over to D, which
contains a solution of caustic potash ; this absorbs all the
164
HYGIENE
carbon dioxide. By lowering L the gases are withdrawn
into A, and the change in volume noted ; the difference
gives us the amount of carbon dioxide absorbed.
Now, on turning the tap (7, the contents of A may be
pushed over to E, which contains a solution of pyrogallic
acid in caustic potash. This absorbs the oxygen. On
returning the contents back to A and reading the volume,
we find by difference the amount of oxygen absorbed. Tin-
remaining volume represent* the amount of nitrogen.
Fio. 73. — DIAGRAM SHOWING THE APPARATUS USED TO DETERMINE
THE GASEOUS CONSTITUENTS OF BLOOD.
Knowing what volume of air we started with, we can
easily render in percentages the amount of carbon dioxide,
oxygen, and nitrogen. To obtain expired air for analysis one
requires a large rubber bag fitted with inspiratory and expira-
tory valves and a mouthpiece. The bag is squeezed empty,
and one breathes in the outside air. and expires into the bag.
Gases of the Blood.— If a known quantity of blood be
taken from a vein, and the same quantity from an artery,
CIRCULATORY AND RESPIRATORY SYSTEMS 165
of an animal, the gases contained in each can be analyzed
by means of the blood-pump. The blood contains a great
deal of gas, for from every 100 pints of blood there can be
obtained about 60 pints of gas.
The following is a rough method of performing the
analysis (see Fig. 73) :
The bulb G is placed in position C". The reservoir A is
raised until C' is full of mercury. On closing the tap T3 and
lowering A, the mercury will fall in <7', leaving a vacuum.
After producing a vacuum in G', it is placed in the de-
pendent position C. The tap T3 is immersed in a measured
vessel containing defibrinated blood, and this opened for
a moment. Blood will rush up into G, and its volume is
then observed. The reservoir A is still lowered until there
is a greater vacuum in B. The blood in G will begin to froth
and bubble, especially if G be warmed. The gases in B can
be analyzed by methods similar to that described above.
The difference between the gaseous content of venous
and arterial blood is as follows :
100 Volumes of
Arterial Blood would
yield about —
100 Volumes of
Venous Blood would
yield about —
Carbon dioxide
Nitrogen
Oxygen
40 volumes
1-2
20
46-50 volumes
1-2
8-12
Condition of the Oxygen and Carbon Dioxide in the
Blood. — Sugar or salt when brought into contact with
water will disappear by entering in solution. Gases can
a'so enter into solution, and animals living in water obtain
their oxygen from that which is dissolved in the water. It
is found that the amount of gas that can dissolve in a given
volume of water is directly proportional to the pressure
exerted by the gas in contact with the surface of the water.
On the other hand, the amount dissolved will vary inversely
as the temperature. A small amount of the oxygen is held
166 HYGIENE
in solution in the blood, and this portion will obey the
above laws of solubility of gases. But the greater portion
of the oxygen is combined chemically with the haemoglobin,
and will therefore not obey the gaseous laws.
The carbon dioxide is present in a small amount in
solution, but the greater part is chemically combined with
the alkalies of the plasma and the red bloooVcorpuscles.
The nitrogen is held only in solution, and therefore its
amount will vary according to the pressure, and inversely
as the temperature.
Gaseous Exchange between the Blood and the Air
inside the Alveoli of the Lungs.
The gaseous exchange bciiriam the blood and the alveolar
air depends on the concentration of the gases. The oxygen
and carbon dioxide diffuse from the place where there is
more to the place where there is less of each. There is a
higher concentration of oxygen in the air than in the blood,
and a higher concentration of carbon dioxide in the blood
than in the air.
Tissue Respiration. — The term " tissue respiration " is
applied to the gaseous exchange taking place between the
blood and the tissues. The cells of the body cannot live
without oxygen, and the blood is the carrier of oxygen ;
hence in the capillaries the tissues absorb oxygen from it.
The maintenance of life depends on complex chemical
changes, and without oxygen these cannot take place.
One of the resultant products of these chemical changes is
carbonic acid, and this the tissues yield to the blood.
Carried away by the blood, it is eliminated from the lungs.
The greater the extent of the tissue changes in the body,
the greater will be the amount of oxygen absorbed and the
carbon dioxide eliminated. Thus, the amount of carbon
dioxide breathed out by a man during muscular exertion
may be five times as great as during an equal period of rest.
Like most chemical changes, those of the body are
accompanied by the formation of heat, and all the heat of
CIRCULATORY AND RESPIRATORY SYSTEMS 167
the body is formed in this way. In cold weather the
amount of oxygen absorbed and carbon dioxide eliminated
is greater than in hot weather. When cold a man moves
about actively and contracts his muscles, while in hot
weather he is not inclined to do any form of work.
The chief seat of combustion is not in the lungs or blood,
but in the tissues, and especially in the muscles.
Relation of Respiration to the Nervous System. — Respira-
tory movements consist of co-ordinate contraction and
relaxation of special sets of muscles. Such phenomena in
the body are always under the influence of a special group
of nerve Cells. The group of nerve cells which controls the
respiratory movements is situated in the medulla oblongata,
very close to the cardio-inhibitory centre. This is proved
by the fact that, if this part of the brain is destroyed in
animals, the respiratory movements cease at once. The
centre is automatic — that is, it is capable of generating its
own stimuli, which pass along the efferent nerves to the
muscles concerned in inspiration.
The chief efferent nerves of this centre are the two
phrenics, which pass, one on each side, to the diaphragm.
If these nerves are cut the diaphragm ceases to contract.
The intercostal nerves which supply the other respiratory
muscles are also connected with this centre.
Various sensory impulses have a profound effect on the
respiratory movements, and this is due to their having
either a stimulative or inhibitory effect on the respiratory
centre. Irritation in the nose produces a sneeze ; a cough
results from a similar process in the larynx or windpipe.
A dash of cold water on the skin produces a deep breath.
Sharp pain or fright often compels a man to stop breathing.
Respiration comes to a standstill for a short time whenever
a man swallows.
Sighing is a deep inspiration ; it helps the circulation,
because the negative pressure in the thorax is greatly
increased, more blood gets to the right heart, and therefore
more to the brain.
168 HYGIENE
Yawning is a deep inspiration associated with the con-
traction of various muscles, which by pressing the capil-
laries and venules throws more blood to the veins, and
therefore improves the circulation.
Crying, shouting, and laughing, are all good exercise and
improve the circulation, and they should not always be
suppressed in children.
A person to a certain extent has voluntary control
over his respiratory movements ; this is because there ar«
nervous connections between the cortex of the brain, where
consciousness resides, and the respiratory centre.
A group of nerve cells can be influenced not only by
impulses travelling along its nervous connections, but also
by a change in the composition of the blood which supplies
it, and this has been found to be the case with the respira-
tory centre. Physiologists argued that, since respiration
had to do with the gaseous exchange of the blood, it would
be very likely that a variation in the percentage of the
gaseous contents of the blood would act as a stimulus to
the respiratory centre, and this was found to be the case.
The slightest increase in the amount of carbon dioxide in
the blood acts as a strong stimulus to the respiratory centre.
The carbon dioxide in the blood regulates the respiratory
centre, so that its percentage is always kept the same.
Owing to this fact, any increased percentage of carbon
dioxide in the air of a room only makes the breathing a
little deeper. It cannot have any poisonous effect. A
great diminution in the amount of oxygen in the air
affects the breathing. Small differences, such as occur
in close rooms, have no effect. The ill-effect of badly-
ventilated and crowded rooms is due to the excessive
heat and moisture and absence of movement in the
air.
The sensory nerve fibres of the respiratory tract run in the
vagi, and impulses passing up these help to co-ordinate the
respiratory rhythm and make the movements work
smoothly.
CIRCULATORY AND RESPIRATORY SYSTEMS 169
Effect of Respiratory Movements on the Circulation. —
It has been said above that the respiratory centre and the
cardio -inhibitory centre are situated close together in the
medulla oblongata. The generation of an impulse and its
passage from the respiratory centre has an influence upon
the neighbouring cardio -inhibitory centre, and it tends to
depress it; therefore the heart generally beats quicker
during inspiration than during expiration.
During the first part of inspiration the arterial blood-
pressure falls, while during the later stage the blood-pressure
is raised a little.
During the first stage of expiration the blood-pressure
rises, while during the later stage it falls a little.
Breathing Exercises. — The first important fact that must
be realized regarding breathing exercises is that the respira-
ticn can only be properly carried out when the air enters
through the nose. A large number of children habitually
breathe through the mouth. This may arise as a bad habit,
and is often followed by nasal obstruction.
But children may be unable to use the nose because it is
partly or wholly blocked by adenoid vegetations, other
forms of growths, or catarrhal condition. Suoh children
are usually weakly developed and of low vitality, and they
soon give up all attempt to breathe through the nose. It
is obvious that breathing exercises will be of no use to
the child unless the mechanical obstruction is removed;
therefore if the teacher suspect a member of a class to be
suffering from nasal obstruction, he should be sent to the
medical officer for examination.
Breathing exercises can be given at short, odd intervals
between lessons. It is very advisable to have all the
windows open all the time, so that there is a good supply
of pure air.
The following is a type of breathing exercise that can be
readily performed by members of a class : The children
should be taught to stand at attention, the shoulders well
pulled back and the hands resting on the hips. They
170 HYGIENE
should then take a slow, steady breath through the nose,
the mouth being firmly closed, raising the chest to ace >m-
modate the intake of air, and keeping the shoulders fixed.
This should be practised several times a day, but not for
long at a time. When the movements of respiration were
described, it was said that in the adult the apex of the lung
is aerated only by contraction of the diaphragm, so it is
also important for abdominal breathing to be practised.
Many authorities maintain that breathing exercises, if
generally and thoroughly carried out in every school and
by all children, would do more than anything else to cause a
rapid diminution in the number of cases of adenoids i:>
children and consumption in young adults.
Only general principles that should guide the teacher
when instructing a class in breathing exercises have been
indicated. For the exact performance of the exercises tho
teacher should consult the Syllabus of Physical Exercises
issued by the Board of Education.
A very important objection to these breathing exercises
is that, unless there is a general activity of the body muscu-
lature, they embarrass the circulation, so that walking and
running and outdoor sports are far better respiratory
cngoiee than the kind of ciMFoieea that have been described
above.
Advantages of an Open-Air Life. — In the open air our
bodies are surrounded by layers of air which are continually
changing ; the molecules of air on coming in contact with
our bodies take away some of our body heat, and the
greater the rate at which the layers of air in contact with our
body surface are renewed, the greater will be the loss of
our body heat. This will excite a greater production of
heat in the body, and therefore all the processes involved
in the production of heat will be accelerated — that is,
there will be an increase in the consumption of food and
oxygen and a greater production of carbon dioxide. There
will be greater movement of the body, the muscular
contractions will improve the circulation in the veins.
CIRCULATORY AND RESPIRATORY SYSTEMS 171
the inflow of blood to the heart will be greater, and this
will stimulate the cardiac muscle to contract more
efficiently ; hence the circulation of the blood will be
greatly improved to what it will be if the person habitu-
ally stays indoors.
Since the circulation is improved, and there is vaso-
constriction of the skin vessels excited by the cold, the
blood-pressure will be raised, a better quality and greater
amount of blood will pass to the brain, the condition of
the nerve cells will be improved, and therefore all forms
of mental work will be done better and with greater ease.
When treating of the functions of the blood, it was said
that it possesses substances which protect th*e body against
the invasion of micro-organisms, and there is no doubt that
by leading an open-air life these substances are increased
in amount.
The white blood-corpuscles are also in better condition,
and are able to cope more effectually with any form of
invading germs.
It is a well-known fact that a person who lives an out-
door life is far less liable to contract disease, when exposed
to infection, than a person who lives a sedentary life and
is always indoors.
The mental and moral condition of persons is improved
by outdoor exercises.
Adenoids. — At the back of the nose, where the nasal
passages open into the pharynx, nodules of lymphatic
glandular material are situated. These may cause trouble
by becoming enlarged.
Repeated attacks of cold may result in a chronic inflam-
matory condition of this adenoid tissue. A vicious circle
is set up, the child takes cold more readily than ever, and
eventually the adenoid growths become of a size sufficient
to cause the characteristic signs of obstruction.
Mouth breathing is the most characteristic sign of
adenoids, and it may lead to serious consequences. The
air as it enters the bronchi and lungs has not been warmed
172 HYGIENE
and filtered through the nose; consequently it acte as an
irritant to the mucous membrane of the bronchi, and may
set up bronchitis.
Children so affected are more liable to infectious disease,
and when such disease develops they are more liable to
bronchial and pulmonary complications.
Snoring is another sign of adenoids, and it seldom occurs
in children apart from the presence of adenoids or some
other form of nasal obstruction. Nasal discharge is fre-
quently present, and leads "to excoriation outside the nose.
There are important ear signs which arise from adenoid
vegetation. Deafness is very common. This is due to
blockage of the Eustachian tube. The inflammatory con-
dition may spread up the Eustachian tube, and lead to
inflammation of the middle ear. Pus may be formed here,
the tympanic membrane perforated, and a discharp fmm
the ear result.
The speech of children with adenoids is ali.-r.-d. I IM n
is marked nasal intonation, and in younger children the
speech is thick and indistinct, and pronunciation defective.
This is due to defective action of the soft palate and the
general catarrhal condition of the nose and pharynx.
There ait certain nervous conditions usually associated
with adenoids. There is a curious condition of mental
dulness characterized by marked loss of power of concen-
tration. There are various theories about the way it is
brought about ; it is certainly partly due to deafness.
Night terrors are often present. Nocturnal ii imminence
of urine is another condition associated with adenoids.
Tight Clothing. — Tight clothing hinders the respiratory
movement and the taking of exercise. It also causes
displacement of organs ; tight OOCTeto cause the liver to be
pushed up towards the thorax, and the stomach is often
displaced, and this certainly interferes with the functional
activity of these organs.
It causes-compression of the muscles beneath, and there-
fore they tend to atrophy.
CHAPTER V
THE EXCRETORY SYSTEM
Care of the Body. — The life of the members of the human
race may be divided up into various periods, and the mode
of living will vary to a great extent in each period.
Certain broad principles may be laid down, which apply
to all periods of life, such as the necessity of nourishing
food, suitable clothing, adequate periods of work and rest,
appropriate exercises in the open air, etc. ; but the quality
and quantity of these necessities vary according to the age
of the individual, so that it is impossible to lay down any
strict rules that apply equally to persons of all ages, and
not even to those of the same age.
A few words must be said in a general way on personal
cleanliness, habits, clothing, etc.
Personal Cleanliness. — The importance of personal clean-
liness must be instilled into the children. The hair, face,
and hands, should always be clean, and the nails kept short.
The skin must be kept clean, because dirt predisposes to in-
fection by bacteria and the formation of blackheads, pimples,
boils, and abscesses, and it harbours parasites. A weekly
change of underclothing and frequent baths are essential.
The benefits of school baths have been extolled by teachers
and doctors ; there is great reduction in skin diseases and
vermin, increased self-respect among the scholars, dis-
appearance of unpleasant odours in classrooms occupied
by the children, and good moral influence on the homes.
Cold baths and swimming have a splendid tonic effect on
the body.
173
174 HYGIENE
The hygiene of the mouth and teeth has been discussed
in Chapter III.
Habits. — Children are very sensitive to every form of
external impression, and habits are formed very early in
life. Since children are so imitative, it is very important
that the teacher should give them a good example of
character and personal cleanliness.
The children should be taught the importance of cleanli-
ness of the skin, care of the teeth, regular action of the
bowels, sufficient sleep, adequate exercise, and the avoid-
ance of tobacco and alcohol. Constipation is one of the
commonest diseases in this country, and this is largely due
to the fact that parents do not teach their children that the
daily regular action of the bowel is a necessity for health,
and this regularity can only be attained by keeping to the
same hour every day. For most people the most con-
venient time is just before or after breakfast. Children
should be taught that to allow waste products to accumulate
in the body causes the absorption of putrefactive sub-
stances, which poison all the tissues.
Another very bad habit is spitting. This should be sup-
pressed in the schools, not only on account of its filtlii-
ness, but because it is often a potent factor in spreading
disease ; for instance, there is no doubt that spitting by
consumptive persons is a very important factor in the
spreading of this disease.
There are other bad habits that children may attain in
schools, and it is the duty of teachers to do all in their
power to suppress them.
The children should also be taught their duty in helping
to keep their homes, the streets, and open spaces, parks,
and gardens, clean and tidy.
Nutrition. — In order to develop a healthy body and mind,
an adequate amount of food is absolutely necessary.
Foodstuffs may be divided into three great classes : starches,
fats, and proteins. The uses of food in children are —
(1) To build up the tissues during growth ; (2) to supply
THE EXCRETORY SYSTEM 175
the energy for the formation of body heat and all the work
of the body — e.g., contraction of muscles, secretory pro-
cesses, brain work, etc. ; (3) to repair the damage due to
wear and tear of the body tissues.
The proteins, starches, sugars, and fats, all serve as
sources of energy to the body, but the proteins are necessary
for the building up and repair of the tissues.
The tissue-forming food, or protein, is the most expensive
foodstuff, and is therefore amongst the poorer classes
deficient in quantity and quality, and this results in poor
physical and mental development.
Fats seem very essential for children, and deficiency in
fat is one cause of rickets.
Unless children are properly fed, it is unprofitable to
attempt to teach them. The mental apparatus of such
children is unfit for work, and if work is insisted upon,
the nervous system is readily exhausted, and this results
in all sorts of evil.
The Regulation of the Heat of the Body. — The temperature
of the human body remains practically constant in all
conditions of normal health.
Temperature is registered by means of a thermometer, and
the special form of instrument that is used to ascertain the
temperature of the body is called a " clinical thermometer."
The organs of a man's body work at a temperature of
98'5° F. If the temperature either rises or falls a few
degrees, the functions are disordered, and if continued for
some time life becomes endangered.
The temperature is kept uniform by the control (1) of
heat production, (2) of heat loss.
Heat Production. — In order to maintain life, certain com-
plex chemical changes are going on in all forms of living
tissues, and such changes always produce heat. The con-
traction of the muscles results in the breaking down of
complex contractile substances and the formation of heat
and simple waste products — carbon dioxide and water.
When a person gets cold, he voluntarily increases the
170 HYGIENE
activity of his muscles by moving about ; e.g., a coachman
or policeman beats his chest and stamps his feet on the
ground, and this results in greater production of heat, and
tends therefore to maintain the. body temperature constant
Each contraction of the heart produces heat, and the
force that is spent in driving the blood through the circu-
latory system is also turned into heat.
The liver, stomach, and all other organs, during activity
produce heat.
In cold weather man naturally eats more and shows
greater activity, while in hot weather he eats less and
avoids effort.
The circulation of the blood distributes the heat evenly
to all parts of the body.
Heat Lou. — Heat is lost in the urine, faeces, expired air,
but mainly from the skin. Heat is lost from the skin by
conduction, convection, radiation, and evaporation.
When one end of a poker is placed in a fire, the distal end
very soon becomes hot, and the heat is carried along the
poker by a process called " conduction " — that is, it is
carried from one molecule to its neighbour, and this gives up
some of its heat to the molecule that is next to it, and so on.
Convection is only possible in liquids or gases. The air
in contact with the body is heated, its molecules expand
and become lighter, these move away and are replaced
by molecules of lower temperature, these, again, are heated,
and thus the body will continually go on losing heat as
long as its temperature is higher than that of the surround-
ing air.
Heat may be carried from one body to another without
heating the intervening medium, and such process is called
44 radiation."
Evaporation is the conversion of water from its liquid
to its gaseous state. This takes place on the surface of the
body ; sweat is secreted by the sweat-glands, and this is
evaporated on the surface of the body, and in order to
convert water to steam a large amount of heat is required.
THE EXCRETORY SYSTEM 177
This is one of the most important means by which the heat
of the body is lost.
All the above processes are made more effectual by
increasing the rate at which the air in contact with the
body is changed. They are also increased by a greater
blood-supply to the skin.
On the other hand, the heat loss is diminished by the
stagnancy of the air in contact with the body, and a de-
creased supply of blood to the skin.
It is thus seen why in cold weather the skin is pale, the
excretion of sweat is decreased, and more clothes are put
on, while in warm weather the skin is flushed, there is
greater formation of sweat, and the amount of clothing is
diminished.
Clothes. — The function of clothing is to prevent a too
rapid loss of body heat, and this it does by entangling air
within its meshes. Clothes prevent the loss of heat by
convection, for the air, when warmed by the body, cannot
rise owing to the garments which entangle it. Air is also
a bad conductor of heat.
Woollen clothes are warmer than cotton, owing to their
spongy texture. White reflects away most sunlight, and is
therefore coolest ; black absorbs most.
The following are the most important facts that should
be considered in the selection of material and type of
clothing :
1. The clothes should offer ample protection to the body against heat
and cold, and should be such that the surface of the body is held at about
the same temperature during summer and winter.
2. They should not interfere with the function of the skin or any of
the internal organs.
3. They should be light, and it is easy to obtain warm clothing
though it may be light.
4. They should not constrict any part of the body ; further, a loose
clothing is much warmer, because the amount of air entangled is greater
than in the case of tight clothing.
5. They should allow efficient evaporation of sweat from the surface;
otherwise the underclothing will become soaked in perspiration, and -
the skin be sensitized and very liable to be chilled.
12 r •-•;'.•
178 HYGIENE
The underclothing of children should be made of flannel.
It is the best absorber and retainer of moisture, and the
worst conductor of heat ; it therefore prevents any sudden
change of temperature of the skin. Flannel does not catch
fire, and is safest for children. Flannelette, on the other
hand, is very inflammable. Some children are over-
clothed, and their skin becomes very sensitive and delicate,
and loses its power to react when chilled. Great care
should be taken to afford ample protection to the feet.
Woollen socks or stockings should be worn ; the boots
should be made of good leather, fit well, and be protective
against cold and damp.
Waste Matter. — The waste matter of the body is made up
of the portions of food that remain unabsorbed from the
intestine, and also certain chemical compounds that are
formed during the chemical changes going on in the tissues
of the body. These latter compounds are formed from the
food that is absorbed, and result from their oxidation in the
tissues.
The undigested foodstuffs remaining in the intestine
constitute the faeces, and their composition has been dealt
with in the chapter on digestion.
The waste products that are formed in the tissues are
mainly carbon dioxide, water, mineral salts, urea, and uric
acid ; these are expelled either in the urine, the sweat, or
from the lungs.
The Kidneys and the Excretion of Urine.— The urim- is
the most important excretory product of the body.
It contains in solution- the substances that result from
the chemical changes going on in all the tissues. In
order to learn some of the most important properties
of urine, you should perform the following simple experi-
ments :
1. Collect all the urine passed in twenty-four hours. Measure the
quantity, note its colour, and determine its density by means of a
hydrometer.
2. Determine whether it is acid, alkaline or neutral in reaction, by
placing a piece of red or blue litmus-paper in it.
THE EXCRETORY SYSTEM 179
3. Place a little in a test-tube, and heat it over a spirit-lamp or Bunsen's
flame. Healthy urine will remain unchanged, or a slight cloudiness
may be produced, which disappears on the addition of acetic acid.
On the other hand, if a cloudiness or coagulum is formed which does
not disappear, it is a sign of diseased condition of the kidney, allowing
the proteins of the blood to pass through.
4. If some of the urine be evaporated to dryness, a residue will remain,
consisting mainly of inorganic salts, urea, and uric acid.
5. Evaporate some urine to about a fourth of its volume, and then
add strong nitric acid to it. The acid will combine with urea in the urine,
forming an insoluble crystalline precipitate of urea nitrate. Place a
little of the liquid containing the crystals under the microscope, and
examine their structure.
6. Add a few drops of a solution of copper sulphate and some caustic
potash to a small volume of urine in a test-tube, and heat to boiling on
a spirit or Bunsen's flame. No red or yellow precipitate is formed in
the case of a healthy urine, because sugar is not present. When a person
is suffering from diabetes, his urine readily reduces the copper sulphate,
and a red or yellow precipitate forms. It must be remembered that this
is not an infallible test for sugar.
7. Add some hydrochloric acid to some urine in a glass vessel, and allow
it to stand for twenty-four hours. A pinkish precipitate of uric acid
will be formed, and deposited at the bottom of the vessel.
8. To some urine in a test-tube add a little nitric acid and solution
of silver nitrate. A white precipitate of silver chloride will result.
This shows the presence of chlorides in the urine.
9. To show the presence of sulphates, take a little urine in a test-tube
and add to it some hydrochloric acid and barium chloride. A white
precipitate of barium sulphate will result.
10. The presence of phosphates can be proved by adding solution of
ammonium molybdate and nitric acid ; a yellow crystalline precipitate
will be formed.
Properties and Composition of Urine. — In a healthy
subject the urine is a clear amber-coloured liquid, acid in
solution, and its density is higher than that of water. If
the specific gravity of water be represented by 1000, that
of the urine will be 1020 to 1025. It consists of various
inorganic and organic substances dissolved in water.
The specific gravity is a good indicator of the amount
of solids dissolved in the urine. Thus, after copious
drinking the specific gravity is Jowered, while after hard
muscular work or copious sweating for any reason it is
180 HYGIENE
increased. A person suffering from diabetes passes much
urine of high specific gravity, due to the sugar present.
Two or three pints of urine are passed every day by a
healthy man. Of course the volume will vary with the
amount of fluid taken into the body, and the amount of
water that is eliminated through other channels, such as
the skin, bowels, or lungs.
The inorganic constituents of the urine are the chlorides,
sulphates and phosphates of sodium, potassium, calnum,
and magnesium, but the salt that is present in largest
amount is common salt, or sodium chloride. The presence
of these salts can be shown by means of the testa given
above. The chief organic constituents of urine are urea,
uric acid, and creatinin.
Urea is the chief nitrogenous excretory product of the
body. It is partly derived from the wear and tear of the
tissue, and partly from the proteins that are absorbed from
the alimentary canal. In the chapter on digestion it was
said that the proteins of the food are broken down to amino-
acids by the action of ferments in the alimentary canal.
After absorption they are carried along the portal vein to
the liver. If more protein is taken in the food than is
required to repair the tissues, the amino-acids which result
from this excess are broken up in the liver, and the nitrog-
enous portion is converted into urea, while the other moiety
is changed to glycogen. The urea is carried in the blood-
stream to the kidneys and excreted, while the glycogen
may remain' as such in the liver, or be converted into glucose
and carried to the muscles, and there stored as glycogen.
If the non-nitrogenous portion is not required for muscular
work, it is converted into fat, and stored as such in the body.
The liver, and not the kidneys, is the great site of formation
of urea ; this we know because, after extirpation of the
kidneys in animals, urea still continues to be formed in
the body, and finally poisons the animal. If blood con-
taining some of the amino-acids or a solution of ammonium
carbonate be circulated artificially through an excised liver,
THE EXCRETORY SYSTEM 181
the amount of urea in the blood is increased on its passage
through the liver. Diseased conditions of the liver in man
will cause an increased amount of ammonium salts, and a
diminution in the amount of urea in the urine. In the
body uric acid is formed by the breaking up of certain
special forms of proteins called " nucleo-proteins." The
amount of uric acid in the urine, however, does not tell us
anything about the extent of the decomposition of nucleo-
proteins going on in the body, because the greater part of
the uric acid is converted into urea by the liver, and it is
only a small portion that escapes such conversion which
appears in the urine. In certain diseased conditions (gout)
uric acid is deposited in the capsule of Joints, but there is
no evidence of an excess of uric acid in the blood in this
condition, or that excess of uric acid is the cause of the
disease.
Some of the constituents of urine, such as phosphates, uric
acid, or urates, may crystallize out 'and give rise to gravel,
or they may be aggregated together to form a stone ; this
may take place in the kidney or in the bladder, resulting in
a kidney or bladder stone respectively. Phosphates are
deposited in an alkaline urine, while urates and uric acid are
precipitated from an acid urine. Stones give rise to great
pain and other troublesome symptoms, and when once
formed they can be removed only by the surgeon.
Anatomy of the Kidneys. — The kidneys are two organs of
characteristic shape, placed on each side of the vertebral
column in the lumbar region. The last rib passes behind
each kidney at the junction of the upper with the lower
two- thirds. Each kidney is embedded in a capsule of con-
nective tissue containing large quantities of fat.
The outer border of the kidney is convex, while the inner
is concave and directed towards the vertebral column. This
concavity is called the " hilum of the kidney," and here we
find entering and leaving the kidney the renal artery and
vein, and also a muscular tube, called the " ureter," which
carries the urine from the kidney to the bladder. The
182
HYGIENE
relative positions of these structures is the vein in front, the
ureter behind, and the artery in between. The renal
arteries come from the abdominal aorta, while the renal
veins join the inferior vena cava. The blood-supply to the
kidney is very large.
On section the kidney will be seen to be made up of a
peripheral dark red granular portion called the " cortex,"
and an inner pale striated portion called the " medulla " ;
FIG. 74.— DIAGRAM TO SHOW STRUCTURE SEEN OH LONGITUDINAL
SECTION OP THE KIDNEY.
A, Cortex ; B, medulla ; 0, pelvis ; D, ureter.
this is divided into a number of processes called the
" pyramids."
Obtain some sheep's kidneys from a butcher, and make
dissections to show their chief anatomical features.
Remove all the fatty connective tissues which surround
the kidney, its bloodvessels and ureter. Make a careful
dissection to show the relative position of the renal artery
and vein and the ureter. Then, with a long sharp knife,
THE EXCRETORY SYSTEM
183
Note the
bisect the kidney, starting at the convex border,
character of the cortex and medulla.
If a section be made of the kidney and examined micro-
scopically, or if a piece of the same organ be unravelled
under the microscope, it will be found to be made up of a
large number of small tubules lined by secreting cells.
£— - A
FIG. 75. — MICROSCOPIC SECTION THROUGH A FRAGMENT OF THE
KIDNEY.
A, Connective-tissue coat, or capsule ; B, convoluted tubules ; 0, glom-
erulus ; D, loops and collecting tubules ; E, artery.
These tubules are held together by connective tissue, and
supplied by a rich capillary network of bloodvessels.
When each tubule is examined by itself, it will be found
to have a long and complicated course. It commences in a
dilated portion, called the " capsule," which surrounds a tuft
of blood-capillaries called the " glomerulus " ; this is situated
184 HYGIENE
in the cortex. The first portion of the tubule courses
irregularly in the cortex, then runs down into the medulla,
where it forms a loop, and returns to the cortex, to again
take an irregular course ; finally it opens into a collecting
tube which passes straight through the medulla, to open
into the pelvis of the kidney at the apex of the pyramids.
The striated structure of the pyramids is due to its
being made of straight-coursing tubules, while the granular
appearance of the cortex results from the presence of the
glomeruli and the irregular course of the tubules.
Blood-Supply of the Kidney. — The right and left kidneys
are supplied by the right and left renal arteries, which arise
from the abdominal aorta.
Each artery enters the liiliim of the kidney, and there
divides into branches, which pass in between the pyramids
towards the junction between the cortex and medulla
Here the branches form a series of arches in the substance
of the kidney. From these arches small arteries run out-
wards into the cortex to supply the glomeruli, and on the
inner side branches are given off to the pyramids. Each
glomerulus is supplied by its own artery, which breaks up
into a number of branches. These join into an efferent
vessel which, on issuing from the glomerulus, breaks up
into a network of capillaries which surround and supply
the convoluted tubes.
The blood is returned by a series of veins, which join
together finally to form the renal vein.
Secretion of Urine. — The urine is formed by the secretory .
activity of the cells lining the capsule and tubules. The
water and salts are secreted through the glomeruli, while
the organic constituents are thrown out of the blood
through the activity of the cells lining the renal tubules.
The amount and character of the urine is influenced by
a large number of factors, which act by varying the amount
or character of the blood supplying the kidneys.
If the amount of blood passing through the kidneys is
increased, there will be a greater amount of urine secreted.
THE EXCRETORY SYSTEM 185
Thus, on a cold day the arteries of the skin are constricted,
less blood passes through the periphery of the body, more
FHJ. 76. — DIAGRAM SHOWING THE ARRANGEMENT OF THE BLOODVESSELS
IN THE KIDNEY.
A., Arteries supplying the glomeruli ; B, vein ; (?., glomeruli.
circulates through the viscera, and this increased visceral
blood- flow is shared by the kidneys, which respond and
secrete more urine. On the other hand, on a hot summer's
186 HYGIENE
day the bloodvessels of the skin are dilated, a greater
amount of blood passes through the periphery and a
smaller amount through the viscera ; this results in a de-
creased secretion from the kidney, and the urine becomes
concentrated.
When a person takes large quantities of fluid, it is
absorbed into the blood, which becomes diluted and in-
creased in volume. Such a condition excites the kidneys
to greater activity ; they excrete copious amounts of dilute
urine, and thus restore the blood to its proper composition.
Certain drugs, such as nitrate or acetate of potash, by
direct action on the cells of the kidney, excfte them to
greater activity, and thus increase the amount of urine
excreted . Certain other drugs — e.g. , digitalis — by improving
the general circulation through the kidneys, increase the
amount of urine excreted.
Ureter. — This is the small muscular tube by means of
which the urine is carried from the hiliini of the kidney
to the bladder. The muscular coat is made up of an outer
circular and an inner longitudinal layer; it is lined by a
mucous membrane. The urine is passed along the ureter
by repeated contraction of its muscular wall.
The Bladder.— The bladder is a structure into which the
urine flows along the ureter from the kidneys, and where
it is lodged until its expulsion from the body.
It is really a muscular bag, lined by a mucous membrane.
Its muscular coat is made of involuntary fibres, which are
disposed in three layers. The ureters pass into the bladder
in an oblique direction, and thus their orifices are covered
by a fold of mitf-ous membrane, which prevents the back-
ward flow of the urine from the bladder to the ureter.
The bladder opens below the pubic arch (formed by the
junction of the anterior parts of the two ossa innominata)
into the urethra. Certain fibres of the bladder coat are
aggregated at the base to form a sphincter. The urine
continuously flows along the ureter from the kidneys. When
the bladder has been filled to a certain amount, the pressure
THE EXCRETORY SYSTEM 187
is sufficient to arouse a sensation of fulness or desire to
micturate. The pressure of the urine inside the bladder
stimulates the sensory nerve-endings in the mucous coat ;
the impulses are carried to the spinal cord, where they
initiate reflex motor impulses, which cause contraction of
the musculature of the bladder. The pressure of the urine
inside is still further increased, and there is a corresponding
increase in the sensation of wanting to micturate. These
impulses cause relaxation of the sphincter.
There is another sphincter or compressor of the urethra
situated just below the pubic arch ; this muscle is .under
voluntary control. The impulses set up in the bladder
are passed to the spinal cord, and they also reach the
cerebral cortex, which exercises a certain voluntary control
over the process. When the occasion is fitting, the volun-
tary part of micturition comes into play — namely, relaxa-
tion of the sphincter and increased abdominal pressure,
brought about by closure of glottis and contraction of the
abdominal muscles.
The Skin. — The skin consists of two parts — an outer layer,
or epidermis, resting on a deeper layer, the dermis.
The skin as a whole is connected to the tissues it covers
by a layer of loose connective tissue called " subcutaneous
tissue."
The epidermis is made of stratified epithelium. It is
composed of a number of layers of cells, the deeper of which
are soft and protoplasmic, and form the rete mucosum,
whilst the superficial layers are hard and horny.
The dermis is composed of dense connective tissue, which
becomes more open and. reticular in texture in its deeper
part, where it becomes connected with the subcutaneous
tissue. ^
Sweat- Glands. — If the skin of the palm be examined with
a lens, minute pits may be seen, placed in rows on the ridges.
These pits are the pores, or ducts, of the sweat-glands.
Each gland is composed of a coiled little tube, and lies in
the deeper parts of the skin. The sweat-glands, like most
188
HYGIENE
glands in the body, are supplied with secretory nerves,
which run in the sympathetic system.
The presence of these secretory nerves can be .sli»\\n l>v
severing the nerve of the leg of a cat, when on placing the
cat in a warm chamber the pad of the foot on that leg will
not sweat, while the other three feet will.
FIG. 77. — MICROSCOPIC SECTION THROUGH THE SKIN.
A, Horny layer of cells ; B. layers of soft-growing cells ; C, thick con-
nective-tissue coat ; D, fat layer ; K, sweat-gland and duct ; /'. hair ;
0, sebaceous gland ; //, papilla of hair ; J, small artery ; K. muscle
of hair ; L, capillaries.
Composition of Sweat. — It is very difficult to determine
the precise composition of sweat, because, as it is usually
obtained, it is mixed with the secretion of the sebaceous
glands.
It is made up of water having small quantities of in-
organic and organic substances dissolved in it. The larger
part of the inorganic salts consists of sodium chloride.
Small quantities of the alkaline sulphates and phosphates
are also present. The organic constituents, such as urea.
THE EXCRETORY SYSTEM 189
are present in mere traces. Usually the amount of urea
excreted by the skin is very small, but when the kidneys
are diseased the amount found in the sweat is greatly
increased. There are sebaceous glands attached to the
roots of the hairs, which secrete a fatty substance — the
sebum.
Functions of the Skin. — The skin in man has many im-
portant functions to perform. (1) It protects the internal
organs from injury and access of bacteria ; (2) it regulates
the loss of heat from the body ; (3) it has many important
sensory functions (these will be dealt with in Chapter VIII.) ;
(4) it acts to a small extent as an excretory organ.
The most important excretory product of the skin in a'
normal person is water. The quantity of water excreted
by the skin of a man in twenty-four hours varies so much
that it would be impossible to quote any exact figures.
It is enough to say that the excretion of water from the skin
is about as much as the amount excreted by the kidneys
hi the same interval of time. The water is excreted by the
skin in order to keep it supple and to cool the body by
evaporation. The sebum helps to keep the skin and hair
supple and sleek, and prevents these being penetrated and
softened by water. It also prevents the invasion of bac-
teria. It is unwise to wash away the sebum by the too
free use of soap.
The amount of solids excreted by the skin in a normal
person is very small, but under diseased conditions the
amount may be greatly increased.
The Lungs act as excretory organs, because they get rid
of carbon dioxide and water. The older physiologists
believed that there were volatile poisonous organic com-
pounds given off by the lungs, but modern research work
disproves such a theory.
CHAPTER VI
THE NERVOUS SYSTEM
THE nervous system is the most highly developed portion of
the body. In the lower animals it is represented by a
•layer of cells which have specially developed the function
of responding to changes hi the environment of the organism.
In the higher animals, man included, the nervous system
controls all the functions of the body, and converts to
consciousness all the impulses that the organism receives
from its surroundings by means of its sense organs.
The nervous system is made up of a number of units,
each of which is called a nerve cell or neurone, and this,
like all other animal or vegetable cells, possesses a
cell wall, protoplasm, and a nucleus. The nerve cell is
irregular in shape, due to the presence of a number of small
protrusions, which divide to a number of branches, and one
long process, which as it leaves the cell attains a fatty
sheath, and often travels for a long distance before it
divides into its terminal divisions. The smaller processes
are called dendrites, while the single long process is called
an axon. In the nerve cell, after it has been fixed in alcohol*
may be seen a number of granules, called " Nissl's granules,"
after the man who first described them ; these are thought
to be a special nutritive material for the cell. This has
been proved by experimentation in animals. In the resting
animal the cells contain a large number of granules, while
after exhaustion all the granules disappear. The above
description applies to the commonest form of nerve cell,
and is the form found in the anterior horn cell of the spinal
190
THE NERVOUS SYSTEM
191
cord. There are two other forms of nerve cells found in
the body. One form differs from the above in that the
axon has a very short course, and then divides into a large
number of terminal twigs; this serves to connect other
nerve cells together, and is called an association cell.
Another form of cell is one in which the dendrites are
replaced by a single process forming a second axon ; the
III
FIG. 78.— THREE FORMS OF NERVE CELLS.
I., Multipolar cell ; II., association cell ; III., unipolar cell : N., nucleus ;
D., dendrites; A., axon.
two axons come out of the cell together as a single process,
which bifurcates. This is the type found in the ganglia of
the sensory root of nerves. The nervous system is made
up of —
1. Central portion, comprising the brain and spinal cord.
2. Peripheral portion, made up of nerves and ganglia.
3. Sympathetic system, which governs the activity of
internal organs and the tone of the bloodvessels.
192 HYGIENE
The peripheral portion of the nervous system is made up
of nerves and ganglia. A ganglion is simply a collection
of nerve cells, which are bound together by connective
tissue ; nerve fibres enter and leave it ; they are found
mainly on the posterior roots of nerves and in the sympa-
thetic system.
Nerves are, as it were, the telegraph-wires of the body,
because they carry messages from one part of the body to
another. They are divided into two classes, according to
whether they carry messages to or away from the central
nervous system. The first class carry impulses from the
N N
N
Fio. 79. — MICROSCOPIC STRUCTURE or POSTERIOR ROOT GAFOUON.
N., Nerve cells ; /'. afferent and efferent nerve fibres.
periphery to the central nervous system, and excite there
sensations of smell, sight, hearing, cold, warmth, etc., by
means of which man becomes conscious of the condition of
the world around him. The second class cany impulses
away from the central nervous system to the periphery,
and these govern the activity of the skeletal muscles,
glands, etc.
The Distribution of Nerves in an AnimaL — Obtain a rabbit,
and kill it by poisoning it with chloroform. Dissect away
the skin, and during this process fine white threads will be
seen hi the subcutaneous tissues ; these are the nerves
supplying the skin. On separating the muscles similar
A. M., anterior meseii-
teric ganglion of sym-
pathetic ; A. M. A., an-
terior mesenteric artery ;
0., coeliac artery ; 0. A.,
cardiac accelerator
G nerve ; C. D., cardiac depressor nerve ;
G. G., cceliac ganglion of sympathetic ;
C. S., cervical portion of sympathetic
nerve chain ; 1st and 8th C., first and
eighth cervical spinal nerve ; D. (upper
one), ductus arteriosus; it joins the
aortic and pulmonary arches, but the
latter is not represented ; the ductus
would join it just where the index line
points ; D. (lower one), diaphragm ;
D. A., dorsal aorta; G., glossopharyn-
geal ; G. A., great auricular nerve ; 0. S.,
greater splanchnic nerve; H., hyoid
bone ; H. G., hypoglossal nerve ; HT.,
heart ; 1C, posterior cervical ganglion of
sympathetic ; L., lingual branch of man-
dibular nerve ; LG, right lung ; L. S.,
lesser splanchnic nerve ; 1st and 7th L.,
first and seventh lumbar spinal nerve ;
M. C., middle cervical ganglion ; MX.,
maxillary division of trigeminal ; MN.,
mandibular division of trigeminal ; 0.,
ophthalmic branch of trigeminal;
P., phrenic nerve; PL., palatine
division of facial nerve; P. M.,
posterior mesenteric ganglion of
sympathetic ; P. M. A., posterior
mesenteric artery ; R. C., rami
communicantes ; R. L., recurrent
(posterior) laryngeal nerve ; 8. A.,
ppinal accessory nerve; 8. M.,
stylo-mastoid muscle; SH., sto-
mach ; ST., sterno-thyroid muscle;
S. G., sympathetic ganglia ; 1st
and 4th S., first and fourth sacral
spinal nerves ; T.. tongue ; V.,
vagus ; 1st and 12th T., first and
twelfth thoracic spinal nerves ; //.
and VII., second and seventh
cranial nerves. The trachea lies
just behind the sterno-thyroid
muscle (ST.), and its top dilated
part represents the larynx. The
dotted tube behind it is the
oesophagus.
19TH
••
-L.S.
"SG.
•R.C.
1STS.
Fia. 80. — CRANIAL AND SPINAL NERVES AND THE SYMPATHETIC
NERVOUS SYSTEM OF RABBIT (LEPUS). A SIDE-DISSECTION,
SEMI-DIAGRAMMATICALLY REPRESENTED.
13
194 HYGIENE
threads will come into view. Now separate the muscles on
the back of the thigh. A white cord will be found ; this
is the main nerve of the lower limb, and called the " sciatic
nerve." Follow it upwards, cutting through each success! \ •
structure that conceals it from view. The hip-bone will
have to be cut through, for the nerve passes through th>-
pelvic bone, and finally extends to the lower part «>f
the backbone. Here the nerve will be found to divide
into several branches, which disappear into the vertebral
column, where they join the lower part of the spinal cord.
Having removed the skin from the back of the rabbit,
and also the muscles which cover the vertebral column,
take a strong pair of scissors and cut away the spin«»i-
processes of the vertebrae ; then insert the point <>f nm-
blade between the arches of any two vertebrae about the
middle of the spine, and cut away the arches of the
vertebras ; this must be done with great care, and the blade
that lies inside the vertebral canal must be kept very < I
to the bony arches, so as not to injure the spinal <•<
This dissection will expose the spinal cord. At the level <»f
the lumbar vertebrae the spinal cord tapers to a filament
and is surrounded by a leash of white nerves ; this par
called the cauda equina. or horse's tail. Above the spinal
cord Joins the brain.
On either side of the spinal cord nerves are given off in
pairs, and there are in man altogether thirty-two pairs of
spinal nerves ; these pass out of the spinal canal by aper-
tures between the vertebrae, called the " intervertebral
foramina.'*
Roots of the Nerves. — If a nerve be examined as it leaves
the spinal cord, it will be found to arise by two roots. One
of these issues from the back, and the other from the front,
of the cord, and they are called respectively the " posterior"
and " anterior " roots. These two roots join together as they
leave the vertebral canal, and Just at their junction there
lies on the posterior root a small swelling, called the " pos-
terior root ganglion."
THE NERVOUS SYSTEM
195
It has been found that, if the anterior roots of nerves are
severed in an animal, then all the muscles supplied by
these nerves will be paralyzed. For instance, if the anterior
roots of the nerves supplying the legs are cut, the animal
will be unable to move them, but it will be able to feel
FIG. 81. — DIAGRAM SHOWING THE ORIGIN AND COURSE OF A SPINAL
NERVE — e.g., INTERCOSTAL NERVE.
A, Spinal cord ; B, anterior horn cells ; C, posterior root ganglion ;
D, anterior motor root ; E, posterior or sensory root ; F, posterior
division of nerve ; 0, anterior division ; //, lateral cutaneous branch ;
K, anterior cutaneous branch.
anything that is cold or hot, and a prick or touch, in the
legs. On the other hand, if the posterior roots of the
nerves are severed, the animal will be unable to feel any
prick or touch or anything cold or hot when applied to the
legs, but it will be able to move the legs. Hence it is seen
196 HYGIENE
that the posterior roots cany sensory impulses from tho
periphery to the spinal cord, while the anterior roots cany
motor impulses from the cord to the periphery.
Structure of the Nerves. — Take a small piece of nerve
from a frog or rabbit and place it on a glass slide, and by
means of a couple of needles teaie it out into a number of
fine filaments. Place a drop of saline solution on tl it-
threads, and examine with the high power of a microscope.
These filaments are the nerve fibres, and are bound up in
bundles, and the bundles are wrapped together by connec-
tive tissue to form the nerves. Each fibre will be sr« n t<>
be made up of a central core, which is called the " azon " ; a
layer of white fatty material, which forms a sheath around
the axon; and, outside this again, a very thin grey sheath
of connective tissue. The axon is the essentially conducting
C BAD
Fio. 82.— STBCCTUBK OF NERVE FIBRB.
A, Neurilcmma ; B, nucleus ; C, medullary sheath ; D, axon.
part of a nerve fibre, and is derived from a nerve cell. The
white or medullary sheath protects and nourishes the axon,
and separates it from the axons of neighbouring nerve
fibres. The grey sheath, or neurilemma, encloses the fatty
sheath and supports it. At regular intervals along the
course of a nerve fibre little intermissions will be seen in
the medullary sheath, and here the neurilemma comes in
contact with the axon ; these are called the " nodes of
Ranvier." About midway between any two nodes a nucleus
will be seen just underneath the neurilemma.
In the sympathetic system the majority of the fibres,
after leaving the chain of ganglia, lose their medullary
sheath, and hence are called " non-medullated fibres."
If an exposed nerve is pinched, irritated by a hot wire
or an electric shock, the muscles to which the nerve is
THE NERVOUS SYSTEM
197
distributed contract. This indicates the passage of a
nervous impulse along the nerve. We do not know the
exact nature of this nerve impulse.
The Spinal Cord. — The spinal cord is the portion of the
central nervous system which lies within the vertebral
canal. It extends from the brain above to the upper part
of the lumbar region. In order to understand the structure
of the spinal cord, it would be advisable for you to have
the spinal cord of an ox, and then cut it across at various
levels with a sharp knife. (Ask your butcher for the
marrow out of the spine.)
FIG. 83. — CROSS-SECTION OF SPINAL CORD.
A, Grey matter ; B, anterior horn ceils ; C, Clark's column ; D, posterior
columns ; E, an tero -lateral columns.
The cord is intimately covered by a thin vascular mem-
brane called the pia mater, and the spinal canal is lined by a
strong fibrous membrane called the dura mater. Between
these two is a very delicate membrane called the arachnoid.
The space between the membranes is filled with a watery
liquid called cerebro-spinal fluid, because it is found in the
cranial and spinal cavities. The cord is held in its place by
the spinal nerves, and also by bands of ligament, and these,
with the support of the fluid, protect it from shock or jar.
When the cord is cut across with a sharp knife, it will be
found to be composed of a white substance lying on the
outside, and partly of a pinkish-grey substance lying within.
198 HYGIENE
The cord is almost divided into halves by an anterior and
posterior fissure, each of which runs inwards from the
outside towards the centre of the cord. In cross-section
the grey matter is shaped like the letter H. There are two
crescent-like masses of grey substance lying in each half
of the cord, and joined by a narrow bridge of the same
material which crosses the middle of the cord.
The two ends of each crescent are called its " horns " or
" cornua," the one directed forwards being the anterior horn,
the one turned backwards the posterior horn.
The grey matter is made up of nerve cells ; this can be
readily proved if a piece of cord is cut into very thin
sections and stained with certain dyes.
The white matter consists almost entirely of nerve fibres,
supported in a delicate framework of connective tissue.
The anterior roots of the nerves arise from the anterior
horns of the grey matter, wliile the posterior roots enter the
cord near the posterior horns.
Functions of the Spinal Cord. — The white matter is made
up of nerve fibres which are running either towards or away
from the brain. It has been said above that the spinal
cord is nearly divided into two halves by the posterior and
anterior median fissures. The white matter of each half
of the (•' T(! is divided by the posterior roots of the spinal
nerves into an antero-lateral and posterior portions ; the
former is called the " antero-lateral column " and the
latter the " posterior column."
The nerve fibres which carry the same kind of impulses
or have the same destination are aggregated together to
form what are called " nervous tracts," and these tracts are
divided into two great groups — the ascending and the
descending tracts ; the former carry impulses from the
periphery of the body to various parts of the brain, while
the latter carry impulses away from the brain and form
connections with the cells of the grey matter of the spinal
cord. The exact course and destination of these tracts
have been worked out by making a large series of transverse
THE NERVOUS SYSTEM 199
sections and staining them in a particular way. The tracts
of the posterior columns are all ascending, and carry in:-
pulses of muscular sensation, sense of position, touch, and
XII F XI
FIG. 84. — BASE OF THE BRAIN.
/., Olfactory nerve, or first cranial ; //., second cranial or optic nerve ;
///., third cranial nerve ; IV., fourth cranial nerve ; F., fifth cranial
nerve, or trigeminal; VI., sixth cranial; VII., seventh cranial or
facial nerve ; VIII., eighth or auditory nerve ; IX., ninth or glosso-
pharyngeal; X., tenth or vagus nerve; XI., eleventh or spinal
accessory; XII., twelfth or hypoglossal nerve; A, frontal lobe;
B, temporal lobe ; C, optic tract ; D, crura cerebri ; E, pons ;
F, medulla.
pain. All these fibres come into the cord through the
posterior root of the spinal nerve, and ascend on the same
side of the cord.
The tracts of the antero-lateral columns are partly
200 HYGIENE
ascending and partly descending. The ascending tracts
carry impulses of sensation of touch, heat, cold, and pain ;
these also come to the cord through the posterior root of the
spinal nerve, but they then cross to the antero-lateral
column of the opposite side, and hence these tracts carry
sensations from the opposite side of the body. There are
two other ascending tracts in the antero-lateral columns,
and these have to do with the equilibration of the body ;
they ascend up to the cerebellum, which is situated beliind
the lower part of the great brain, and which modifies the
contraction of the muscles.
The descending tracts of the antero-lateral coin inns
carry impulses from the brain to form connections with the
cells of the grey matter of the spinal cord. The pyramidal
tract carries impulses from the brain, and governs all the
muscular contractions of the body ; these mainly come from
the opposite side of the brain, but partly also from the same
«ide. Other descending tracts come from the cervix -Hum.
and serve to co-ordinate the contractions of the muscles.
A tract also comes down in the spinal cord from certain
nerve cells in the brain which are connected with a special
part of the internal ear, and these also aid in the co-
ordinate contraction of the muscles, and thus are important
factors in keeping the body in equilibrium in various
postures.
The Brain. — The term " brain " is applied to that portion
of the central nervous system that lies within the skull
cavity. It is made up of several parts — namely, the spinal
bulb or medulla, the pons, the cerebellum, and the cerebrum.
The medulla is the continuation upwards of the spinal
cord. At first it is about equal in size to the spinal cord,
but as it approaches the pons it expands, and hence it has
a more or less conical shape. From the lateral surfaces
some of the cranial nerves (VII. to XII.) arise. \Vlu-n a
section is made of the medulla, it is found to be made up
of white and grey matter. The white matter is continuous
with that of the spinal cord, and is made up of the same
THE NERVOUS SYSTEM 201
tracts, but their relative positions are somewhat changed.
The central canal of the spinal cord, as it ascends to the
medulla, gradually becomes more and more posterior until
it opens out on the posterior surface to form the fourth
ventricle. The grey matter is collected around the floor of
the fourth ventricle.
The pons is a marked white prominence on the basal
aspect of the brain, and is interposed between the medulla
and the peduncles of the great brain.
When a section is made of the pons, it will also be found
to be made up of white and grey matter. A large number of
the nerve fibres will be found to run to the cerebellum.
The cerebellum is a large mass of nervous tissue attached
to the posterior aspect of the medulla. It is divided into
two hemispheres by a deep fissure, and these are joined
together by an extraordinary bridge of nerve fibres.
Above the pons we find the mid-brain, and this is a short,
narrow part of the brain stem, consisting anteriorly of the
crura cerebri, and posteriorly of four little lumps, two upper
and two lower, called the " corpora quadrigemina." Each
hemisphere of the cerebellum sends fibres to the mid-brain,
and these constitute the superior peduncles of the cerebellum.
In front of the mid-brain and beneath the cerebrum, or
fore-brain, we find the basal ganglia. These are made up
of large masses of grey matter, and subdividing them we
find tracts of white matter, made up of nerve fibres running
to and from the brain. These masses of grey matter axe
called the optic thalamus, the lenticular and caudate nuclei.
The cerebrum forms the greater part of the brain. It is
divided into right and left hemispheres by a deep cleft, at
the bottom of which runs a band of nerve fibres, called the
" corpus callosum." This serves to Join the two hemispheres
together. The outer surface of the cerebrum is thrown
into folds called " convolutions," between which are grooves
or fissures. The convolutions increase the area of the
cortex enormously, and the greater the brain-power of a
man the more convoluted will his brain be found to be.
202
HYGIENE
\
FIG. 85.— THE CEREBRAL CORTEX.
A. Frontal lobe; B, parietal lobe; 0, occipital lobe; D. tcmporo-
sphcuoidal lobe ; E, fissure of Sylvius ; F, fissure of Rolando.
Fia. 86.— DIAGRAM ILLUSTRATING THE FUNCTIONS OF THE VARIOUS
PARTS OF THE CEREBRAL CORTEX.
THE NERVOUS SYSTEM 203
If a section be made through a cerebral hemisphere, the
wall will be found to be made up of an outer layer of grey
matter and inner layer of white matter, and enclosed within
is a cavity called the " lateral ventricle."
Each cerebral hemisphere is divided up by deep fissures
into lobes, and the surface of each lobe is thrown into
convolutions by smaller fissures. Hence in the front part
of the brain we find the frontal lobe ; the middle and upper
part is formed by the parietal lobs ; behind is the occipital
lobe ; while below and externally is placed the temporo-
sphenoidal lobe.
The Cranial Nerves. — Twelve pairs of nerves arise from
the brain and pass out of the skull through holes in its walls.
1. The first pair of cranial nerves are the olfactory, or nerves of smell.
They arise from the front part of the base of the brain, and give off a
large number of fine twigs which pierce the roof of the nose and supply
the mucous membrane of its upper part.
2. The second pair are the optic nerves. These arise from the mid-
brain, and pass forward around the base of the brain and intertwine there ;
they then enter the orbits and supply the eyeball. The optic nerves are
connected with various parts of the brain, the corpora quadrigemina,
optic thalamus, and the hinder part of the cerebral cortex.
3. The third pair of cranial nerves arise from the mid-brain. They
pass to the orbits, and supply the muscles which move the eyeball.
They also supply the ciliary muscle, by the contraction of which accom-
modation is effected. They innervate the constrictor of the pupil.
4. The fourth pair of cranial nerves arise from the dorsal surface of
the mid-brain, and each enters the orbit and supplies a muscle which
causes a certain movement of the eyeball.
5. The fifth pair of cranial nerves arise from the lateral aspect of the
pons. They contain both afferent and efferent fibres. The efferent
fibres supply the muscles of mastication, while the afferent fibres carry
sensations from the face, anterior two-thirds of the tongue, the mouth,
lower part of the nose, and the teeth.
6. The sixth pair of cranial nerves arise just at the junction of the
medulla and pons. They enter the orbit and supply the muscles which
turn the eyeball outwards.
7. The seventh pair of cranial nerves arise from the medulla. They
supply the muscles of the face.
8. The eighth nerve is the nerve of hearing and of equilibration ; this
enters the upper part of the medulla, and this spreads out to form con-
nections with the cerebrum, mid-brain, and cerebellum.
204 HYGIENE
9. The ninth pair of cranial nerves are called the " glosso-pharyngeal
nerves." They are the chief nerves of taste, and also supply a few
muscles of the pharynx.
. 10. The tenth pair of cranial nerves are the vagus nerves. They
arise from the medulla, and pass down through the neck and thorax
to the abdomen. They supply the pharynx, windpipe, gullet, lungs,
stomach, heart, pancreas, and liver. They contain both afferent and
efferent fibres.
The afferent fibres carry impulses to the medulla from the larynx and
lungs, heart and abdominal organs.
The efferent fibres control the muscles of the larynx, pharynx, and
gullet. The movements and the secretion of the stomach are governed
by these fibres. They also control the rate of the heart-beat, ami t In-
state of contraction of the muscles of the bronchi and bronchioles.
11. The eleventh pair of cranial nerves are the spinal accessory nerves ;
they arise partly from the upper part of the spinal cord and partly from
the medulla. They control some of the muscles of the neck.
12. The twelfth pair supply the muscles of the tongue, and the
movements of this organ are controlled by these nerves.
The Functions of the Brain. — The white matter of the
medulla is made up of various nerve tracts ; some are
passing through to or from the great brain ; others start
in certain groups of cells in the medulla, and are passing to
the cerebrum or cerebellum. The grey matter of the
medulla gives rise to six of the cranial nerves.
There are also groups of nerve cells which are concerned
in regulating the movements of respiration and of the heart,
and life depends upon the integrity of these centres.
The pons contains both white and grey matter. The
white matter is made up of fibres which are passing to or
from the cerebrum or to the cerebellum. It is through
the pons that one side of the cerebrum is connected with
the other side of the cerebellum. The grey matter forms
cell-stations to a number of the fibres passing through the
pons, and also gives rise to the sixth nerve and the efferent
fibres of the fifth cranial nerve.
The crura cerebri are made up of fibres carrying impulses
from the cerebrum to other parts of the nervous system.
In the mid-brain there are large tracts of nerve fibres
carrying impulses to the cerebrum. The grey matter gives
THE NERVOUS SYSTEM 205
rise to the third cranial nerve. The superior corpora
quadrigemina are important centres for sight, while the
inferior corpora quadrigemina have to do with hearing.
Saveral theories have been held regarding the function
of the cerebellum, but now it may be definitely said to have
some important regulatory effect upon muscular contrac-
tion, and thus aid in the equilibration of the body. The
right half of the cerebellum influences the same side of the
body. The cerebellum is largest in birds, and they of all
animals have the greatest power of balancing the body in
various postures. When the whole of the cerebellum is
removed in animals, all the muscles of the body, especially
those of the limbs, are deficient in tone, and contract with
a peculiar want of steadiness. The signs of disease in
the cerebellum are giddiness, a staggering gait, twitching
movements of the eyes, and a tremor accompanying volun-
tary movement.
It has long been established that the cerebrum is the
organ of the higher psychical activities, and all the higher
nervous functions — namely, consciousness, will, reason,
ideation, etc. — depend upon the integrity of the cerebrum.
All these functions reside in the grey matter of the cerebral
cortex, and it is within this that the ceaseless changes take
place which result in the above activities. Naturally the
question arose whether the cerebrum is functionally equiva-
lent throughout, or whether different parts of the cortex
have different functions. It has long been proved, by
experimentation on animals and studying the effects of
disease in man, that certain parts of the cortex are connected
with particular functions, and the modern view is that the
cerebrum is composed of a plurality of parts that are inti-
mately associated, and to a great extent dependent one on
the other for their full functional importance.
Certain parts of the brain, called the motor area, govern
all the voluntary muscles of the body. One of these areas
is situated on each side of the brain, in the posterior part
of the frontal lobe ; the area on one side of the brain governs
FIG.
87. — SYMPATHETIC SYSTEM AND ITS CONNECTIONS WITH
CENTRAL NERVOUS SYSTEM.
A, Spinal cord ; B, posterior root of spinal nerve ; C, anterior horn cell ;
D, posterior root ganglion ; 88 , sympathetic cord and eanglia ;
E, tissue or organ supplied by the sympathetic fibres. Note the
course of afferent and efferent connections of sympathetic.
THE NERVOUS SYSTEM 207
the muscles ou the opposite side of the body. Even within
the motor area there is a further division of labour, so that
certain groups of cells govern the muscles of the leg, while
others govern the muscles of the abdomen, etc. (see diagram
showing various centres).
The anterior part of the frontal lobe is a part where
some of the processes involved in the highest mental activi-
ties take place, and it is this in particular that is un-
developed or degenerated in idiocy.
Between the motor area and the areas of higher psychical
processes are situated two special centres, which are con-
cerned in speaking and writing, and called respectively the
" speech " and " writing" centres. These are only present
on one side of the brain— on the left side in right-handed
persons, and on the right side in left-handed individuals.
The delimitation of the sensory areas in the cerebral
cortex is a matter of great difficulty, because the deter-
mination of the presence or absence of certain states of
consciousness in the animal or person under observation
cannot be made except by indirect means. The only
method that is of any value is to study the sensory changes
produced by disease of the cerebral cortex in man, and
determine the site of the lesion by an examination after
death.
It has been stated above that certain tracts in the spinal
cord carry sensations from various parts of the body.
These fibres finally end in the cerebral cortex, and we
become conscious of these sensations by changes which
take i lace in the anterior part of the parietal lobe, and this
part of the brain is called the body sense area.
Centre for Hearing. — The site in the brain where we
become conscious of what we hear is situated on the outer
surface of the temporo-sphenoidal lobe (see Fig. 86).
Destruction of this area on both sides is followed by com-
plete loss of hearing.
Centre for Vision. — When light is reflected from various
objects on to the eye, an image is formed of these objects
208 HYGIENE
on the retina, but the changes which result in our recog-
nizing and understanding what we see take place in the
cortex of the posterior part of the cerebrum (occipital lobe) ;
this is called the visual centre.
Centre for Taste and Smell. — We become conscious of
sensations of taste and smell by changes which take place
at the apex of the tempo ro-sphenoidal lobes (see diagram).
Co-ordination. — Man inherits certain powers of perform-
ing co-ordinate muscular movements. This is present to a
greater extent in the lower animals. Some of the lower
animals possess power of locomotion very soon after birth,
while in the case of the human subject this power is attained
after much training. The new-born child is endowed with
a certain amount of ability to perform co-ordinate muscular
contraction. Thus, it is able to perform those movements
of the cheeks, lips, and tongue, on which sucking depends.
Many movements, such as walking, running, or cycling,
have to be leamt by the greatest efforts, though when once
acquired they appear natural and spontaneous.
In the special trades and professions we find the highest
stage of special and elaborate movement. The skilled
mechanic by certain movements is able to work certain
things which the untrained person cannot do. The differ-
ence between a trained and untrained singer is due, to a
better co-ordination in the former, of the contraction of
muscles involved in the production of the voice.
The process of co-ordination has been studied experi-
mentally in animals, and they seem to depend upon the
changes that take place in the cerebral cortex, because it
has been shown that in monkeys the co-ordinated move-
ments involved in opening and closing the hand can be
produced by stimulation of certain parts of the cerebral
cortex, but not by stimulation of the anterior roots of the
spinal nerves supplying the hand.
Association. — Above we have described the motor and
sense centres of the brain, but these only occirpy a portion
of the cerebral cortex. The areas which surround the above
THE NERVOUS SYSTEM
209
centres have been called by Flechsig association areas. He
says that the association areas may be regarded as the
regions in which the different sense impressions are syn-
thesized into complex thoughts and ideas. The foundations
of all knowledge are to be found in the sensations aroused
through the various sense organs ; through these paths alone
can our consciousness come into relation with the external
world. The association areas build up all the impressions
received by the sense
organs into organized
knowledge. The changes
that result in the retain-
ment of such knowledge
take place within the nerve
cells of these special areas.
These areas are connected
together and with the sense
centres by nerve fibres,
called association fibres,
and it is by such means
that the various sensations
are grouped together and
organized into complex
knowledge.
Sympathetic Nervous
System.— A chain of ganglia
connected by a nervous
cord will be found lying on
each side of the front of the vertebral column. It will be
found that each spinal nerve, except those of the neck, gives
off a branch which joins these chains of ganglia. This
system of nerve cells and fibres is called the sympathetic
nervous system. Nerve fibres leave the sympathetic ganglia
and supply the viscera, such as the heart, lungs, stomach,
intestines, etc., and also the walls of the bloodvessels.
Other fibres pass from the viscera to the sympathetic
system, and thence to the central nervous system. When the
FIG. 88. — DIAGRAM SHOWING THB
PATHS INVOLVED IN A REFLEX
ACTION.
A, Spinal cord ; B, posterior root
nerve cell ; G, anterior horn cell ;
D, afferent fibre ; E. efferent fibre.
210 HYGIENE
viscera are in a healthy condition we are unconscious of
impulses travelling along these fibres, but under diseased
conditions of the viscera we indirectly become conscious
of such impulses.
Reflex Action. — Reflex action is a means by which a
peripheral tissue or organ is excited to activity by the
passage along efferent fibres of impulses generated by
stimulation of afferent fibres.
Reflex actions can be studied very well in a frog. Obtain
a frog and cut its head off with a pair of scissors. When the
tip of one of its toes is pinched, the leg will be pulled away ;
similarly, if a small piece of blotting-paper soaked in acetic
acid be placed on the back of the frog, the lower limbs
.perform co-ordinate movements which tend to remove the
irritant from the back.
If the spinal cord of a man is badly injured, all the
muscles of the body below the site of the lesion will be
paralyzed, and the man will be unable voluntarily to con-
tract any of these muscles ; he will also lose all forms of
sensations from this region, and will be unable to control
the sphincters of the bladder and anus. If the feet of such
a person be tickled, his legs may suddenly jerk up ; but he
will remain entirely unconscious of the tickling and move-
ment as long as he does not see his legs move. A large
number of reflex actions take place in the normal human
body, such as the sudden closure of the eye when anything
threatens to touch it, contraction of the pupil when light falls
upon it, formation of secretion in many glands, and so on.
In all reflex actions an impulse is passed to the spinal
cord along a sensory nerve ; the fibres of this nerve make
connections with cells in the grey matter (e.g., anterior
horn cell) : this generates an impulse, which travels out of
the cord by the efferent fibres (see Fig. 88).
Some reflex movements can be carried out at birth,
others are attained later on in lif e, and, by sufficient practice,
movements which at first required great attention will be
performed practically unconsciously. For example, walk-
THE NERVOUS SYSTEM 211
ing is learnt with great difficulty, but later on it is per-
formed without any thinking at all. Several other examples
may be noted, such as cycling, skating, knitting, etc.
Nervous System of the Child and its Development. — The
brain of the child, relative to the body, is much larger than
in the adult. The brain also grows very rapidly during
childhood, both in size and complexity.
The growth in complexity is indicated by changes in the
nerve cells and the nerve fibres. It is most probably
correct to say that the number of nerve cells in the body
does not increase after birth. As growth takes place we
find the cells become larger, and the processes (dendrites)
increase in number and size, and form a large number of
new connections with other nerve cells and fibres.
In describing the structure and function of the nervous
system, it was said that there were a large number of nerve
fibres aggregated into various tracts, which pass to and from
the brain, and others, called " association tracts," which
connect different parts of the brain together. Each fibre
is made up of an axon surrounded by a fatty or medullary
sheath. At birth we find that the fibres of a large number
of these tracts have no fatty sheath, and some fibres become
medullated before the others. It is owing to this fact that
we can trace out the tracts by cutting serial sections of the
central nervous system, for the fatty sheath stains differ-
ently. It is said that the fibres do not attain their full
functional activity until they acquire their medullary sheath.
The fibres which carry impulses to and from the spinal
cord are medullated at birth, and thus we find that a large
number of the movements of the child just after birth are
reflex in character.
Very soon after birth myelination takes place in the
fibres of the nerves which connect the sense organs and
their centres in the cortex. Also we find the tracts which
connect the motor area and the spinal cord attaining their
fatty sheaths, and concurrently with these we find develop-
ment of the senses and motor power. The education of
212 HYGIENE
the child consists partly in the development of the asso-
ciation fibres which connect different parts of the cortex,
and concurrently with this they attain their myelin sheath.
But before the myelination of the association fibres we
have the education of the receptive centres. It is most
likely that very early in life light and sound have no effect
upon the child at all. Soon the child will take notice of a
bright light or a sharp sound, but it would be at this stage
unaffected by lesser degrees of light or sound. Later he
will be able to appreciate differences of light and shade,
and these become associated with various planes and
shapes. The impressions from objects that are often seen
are stored up and remembered ; this results in the child being
able to recognize such objects. The centre for hearing is
developed in a similar manner, until it can distinguish and
appreciate different sounds. It must not be thought that
these centres are developed independently, because, as
each centre is developed, ite connection with other centres
becomes functional ; then the child sees certain objects
producing certain sounds, and he learns to associate these
sounds with the objects, and vice versa.
Speech Centres. — The power of communication by language
is attained by the development of certain special centres in
the brain, and these are very important from an educational
point of view.
About 1860 a French physician of the name of Broca
taught that destruction of a small area on the left side of
the brain resulted in the loss of speech, but since then
several other centres have been shown to be associated
with speech. These are situated in the left cerebral hemi-
sphere of right-handed persons, while in left-handed people
they. are situated in the right cerebral hemisphere.
The following are centres of speech :
1. The word-hearing centre.
2. The motor-speech centre.
3. The word-seeing centre.
4. The Trtriting centre
THE NERVOUS SYSTEM 213
The word-hearing centre is part of the hearing centre
on the left side of the brain, and is developed when the
child learns to distinguish special words and to appreciate
their meaning. The word-seeing centre is part of the
visual centre on the left side, and is developed when the
child commences to read.
The left centre, which controls the movements of the
lips and tongue, becomes a special centre for governing
speech, and the centre which governs the movements of the
right arm becomes a new centre to control the special
movements concerned in writing.
The child learns to associate certain words with certain
objects or ideas. This is done by the development of the
word-hearing centre ; thus he hears the word mother, and
this sound he learns to associate with a certain person. One
day he attempts and succeeds to say the word mother, or
any other word that he has heard, and then we have the
developments of the motor-speech centre. The connections
of the centre of sight with the auditory word and the
speech centre are developed, and then, when an object is
placed in front of the child, he remembers it, and also the
sound that is associated with it, and the speech centre will
reproduce this sound, and then the child is able to name the
object.
When a number of objects are placed in front of the
child, he is asked to pick one of them up ; he hears the
sound, and the visual centre reproduces the mental picture
associated with that sound, and then the child picks up the
object that conforms to that mental picture. These
processes go on gradually in the brain of the child, and
the impressions from external stimuli are increased ; such
impressions are remembered and associated with different
persons and objects.
The child generally goes to school at this stage of its
mental development. These centres should continue to grow
in school, and their connections to increase and strengthen.
When the child goes to school he is taught to read and
214 HYGIENE
write, and this is brought about by the development of
two other centres — namely, the word-seeing centre and the
writing centre. The connections between these centres
and with the other centres are also developed, and
these are the phenomena involved in the education of the
child.
Mentally Defective Children.* — The attendance of children
at school was made compulsory by the Elementary Educa-
tion Act of 1876. Previous to this a large number of
children, who subsequently were proved to be mentally
defective, had not received any form of attention from the
State.
A Royal Commission was appointed to inquire into the
matter, and their report was issued in 1889. This was chiefly
concerned with the blind, deaf and dumb, but they drew
attention to the mentally defective, and advised that they
should be separated from the ordinary pupils in the schools
and should receive special attention.
" Mental deficiency " is a term that has a very wide appli-
cation, and is used to cover a number of various abnormal
mental conditions.
If the various centres used in education show very great
lack of development, the condition is called " idiocy " or
"imbecility." Such children seldom reach the schools,
and if they did, they would not be able to profit at all
from the ordinary school methods of teaching. According
to the Defective and Epileptic Children Act of 1899,
mentally defective children are defined as those who, " not
being imbecile and not being merely dull and backward,
are defective, and are incapable of receiving proper benefit
from the instruction in the ordinary public elementary
schools, but are not incapable, by reason of such defect,
of receiving benefit from instruction in such special classes
or schools as are mentioned in the Act."
* For a more detailed discussion of this subject, see article by
A. F. Tredgold, M.R.C.S., L.R.C.P.. on Mentally Defective Children in
" Medical Inspection of Schools and Scholars," edited by T. N. Kelynaok.
M.D. (publishers : King and Son).
THE NERVOUS SYSTEM 215
Conditions associated with Mental Deficiency in Children.
1. Heredity. — There is often a history of mental deficiency, insanity,
epilepsy, or some other nervous derangement, in the family.
Many of the inmates of the London asylums belong to a few families.
A wise State would prevent the mentally deficient having children.
2. Alcoholism. — It has been asserted that alcoholism in the parent
plays an important part in the production of mental deficiency in the
offspring. It is said to act by either injuring the germ cells of either
parent or by deteriorating the brain of the fretus after being absorbed
by the placental circulation. There is no trustworthy evidence that in-
temperance of the parent is a factor in the causation of mental deficiency
in children. Those who are mentally defective by heredity may drink,
and have children defective, not owing to drink, but to heredity.
3. Tuberculosis. — Opinions differ as to the importance of a family
history of tuberculosis in the production of mental deficiency.
4. Cretinism. — This is due to congenital absence of the thyroid
gland, and is always associated with mental deficiency. This condition
is rarely noticed before the child is six or seven months old, and the
signs become marked during the second year. The face is large ; hair
is dry and scanty ; eyelids are puffy and swollen ; the skin is dry and
rough. The abdomen is swollen, the legs are thick and short, the hands
are short and broad, and the finger-tips square.
5. Microcepkalus. — Congenital smallness of the head. The head
may be very small in size. One observer quotes a case of a child, aged
three years, in whom the circumference of the head was only
13| inches. The body and face of the child are usually well developed.
6. Hydrocephalus. — Abnormally large head. It is not a common
cause of mental deficiency, and it is surprising how large a head may
be, and still the mental power be well retained.
7. Injury. — The brain may be injured during intra-uterine life or at
birth, and result in paralysis and mental deficiency.
8. Fits. — In some cases it is found that a child during the first two or
three years is quite normal ; then he has a severe convulsion, which seems
to damage the brain, and from that time the mental development
suffers, though the fits do not recur.
In other cases the child has a series of fits, and the mental state
suffers in consequence.
Cause of Mental Deficiency. — It has been said above that
the higher intellectual functions reside in the frontal region
of the cerebral cortex ; and though the exact relationship
between the mind and matter is not known, still, we should
216 HYGIENE
expect a defective mind to be accompanied by diseased
condition of the brain cells. In the severe forms of mental
deficiency gross changes are seen in the brain, but in the
milder forms the changes can only be discovered by the
microscope. The cortical cells are diminished in number,
incompletely developed, and irregularly arranged, and it
is this condition which gives rise to the ill-developed mind.
Detection of Mental Deficiency. — It is very important
that t\U mentally defective children should be detected
early. Hence, if the teacher has any suspicion regarding
the mental development of any of the pupils, they should
at once be sent to the medical officer. It is only medical
men with good experience of diseases of children that are
able to properly detect and classify such conditions.
The diagnosis of mental deficiency is made on the
(1) family history, (2) personal history, (3) physical and
mental conditions of the child.
A specially trained teacher may greatly help in the
preliminary detection of abnormal mental conditions. He
should ask the parent or guardian about the family and
personal history of the child, and then note its physical and
mental characteristics.
The Family History.— It has been said above that family
history of chronic alcoholism, tuberculosis, and insanity, are
important conditions associated with mentally defective
children, and thus it is important to make inquiries to ascer-
tain whether a child who is suspected to be mentally
defective has such a family history.
Personal History. — Ascertain whether (1) there is a his-
tory of injury at birth or subsequently ; (2) history of
previous disease — e.g., meningitis, convulsions, or paralysis ;
(3) age at which the child walked and talked ; (4) educational
facilities.
Physical Condition. — Note (1) the facies, or facial expres-
sion, which is a valuable index of the mental state ;
(2) general nutrition ; (3) presence or absence of certain
physical stigmata — e.g., harelip, cleft palate, development
THE NERVOUS SYSTEM 217
of Jaws and teeth, adherent lobes of the ears, opacities in
the media of the eye ; (4) measurements of the head and its
shape ; (5) the movements of the eyeballs by moving a
bright object in front of the eyes when the head is held
fixed ; (6) the balance of the hands and arms, by asking the
child to hold out his hands in front.
Tests of Mental Deficiency. — " In principle the method of
M. Binet and M. Simon is very simple. By extensive
observations on French school-childien at different ages,
they were able to arrange a great number of mental tests
in a series of groups graduated according to their increasing
difficulty after such a fashion that each group corresponds
to what the average child of a given age can do. The tests
in each group are of several kinds, and, though theoretical
considerations are deliberately eschewed by the authors,
it is evident that the choice of the tests has had in view
the different aspects of intellectual activity. This, can be
seen from a glance at the list of tests :"
Three Years. — (1) Point out nose, eye, mouth ; (2) repeat a number
with two figures ; (3) enumerate the objects in an engraving ; (4) tell
surname ; ( 5) repeat a sentence with six syllables.
Four Years.— (1) Tell whether a little boy or a little girl ; (2) name
key, knife, penny ; (3) repeat three numerals ; (4) point out the longer
of two lines.
Five Years. — (1) Find which is the heavier of two boxes ; (2) copy a
square ; (3) repeat a phrase with ten syllables ; (4) count four pennies ;
(5) reconstruct a card cut diagonally into two pieces.
Six Years. — (1) Distinguish morning and evening ; (2) define common
objects — fork, chair, table, horse, mother — by use ; (3) copy a rhomb ;
(4) count thirteen pennies ; (5) compare a number of drawings of faces
from an aesthetic point of view.
Seven Years. — (1) Point out right hand and left ear ; (2) describe an
engraving ; (3) do three simple errands ; (4) count three pennies and
three halfpennies ; (5) name four colours — red, blue, green, yellow.
Eight Years. — (1) Make mental comparison between fly and butterfly,
wood and glass, paper and cardboard ; (2) count from 20 to 0 ; (3) point
out features missing in incomplete figures ; (4) give the date ; (5) repeat
five numerals.
Nine Years. — (1) Take twopence out of a shilling and give the change ;
(2) define common objects (see above) otherwise than by use ; (3) recog-
218 HYGIENE
nizo all the current coins ; (4) name the months ; (5) answer simple
questions involving problems of ordinary life — e.g,, " When you have
missed the train, what should you do ?"
Ten Years. — (1) Arrange five boxes (3, 6, 9, 12, 15, and 18 grammes)
according to weight ; (2) copy two simple geometrical designs — a prism
and a Greek moulding — from memory after having seen them for ten
seconds ; (3) criticize a number of absurd statements — e.g*. " The body
of an unfortunate young girl, cut into eighteen pieces, was found yester-
day in Hyde Park; it is thought that she killed herself " ; (4) answer
questions of similar nature but more difficult than in test for nine years ;
(5) bring three given words into two phrases.
Twelve, Years. — (1) Resist a visual suggestion made by a series of pairs
of unequal lines followed by a series of pairs of equal lines, the subject
being asked which line is the longer, and passing the test if he recognizes
the equality in the later pairs ; (2) bring three given words into one
sentence ; (3) say more than sixty words in three minutes ; (4) define
abstract words — charity, justice, and kindness; (5) rearrange a simple
sentence, the words of which have been put out of their order.
Fifteen Years. — (1) Repeat seven numerals; (2) find three rhymes
for a given word ; (3) repeat a sentence of twenty-six syllables ; (4) in-
terpret ah engraving ; (5) explain an unfinished account of a common
episode.
Treatment of Feeble-minded Children. — Very little can be
done for the feeble-minded children. If there are any
physical defects, it may be well to remove them — such as
removal of adenoids, division of tendons if there is paralysis,
treatment of rickets if present, etc. If the mental deficiency
is slight, the removal of the above difficulties will result in a
great improvement. Regarding the treatment of the
mental defect, it must be realized that it is incurable, and
that no special training will convert these children to
normal persons able to hold their own in the world and to
look after their own interests without supervision.
The Elementary Education (Defective and Epileptic
Children) Act, 1899, empowers local authorities to provide
special schools for these children. This provides for their
education up to the age of sixteen, and then they are sent
out to do what they can for their living, and the results
have not been very encouraging.
The only cases that derive any benefit from such educa-
THE NERVOUS SYSTEM 219
tion are those children with one or more defective centres,
and these by careful training and individual attention may
make great improvement.
Backward Children. — There are a group of children in our
schools who, though they appear intelligent, are not up to
the " average " in their educational progress. It is difficult
to draw a hard-and-fast line between this group and the
slightly mentally deficient children, but in attempting to
make a practical distinction between these two groups it
would be well to remember the dictum of Charles West,
quoted by Dr. R. Hutchison, that a mentally deficient child
would be abnormal for any age, whereas a backward child is
merely abnormal for its own age.
Some authorities divide this group into two subclasses —
namely, those who are backward but intelligent, and those
backward and dull. The backwardness in the first group
may be physiological, merely retarded development, or it
may be due to some physical cause — e.g., late entrance at
school, slight deafness, or illness preventing school attend-
ance.
The dulness of the second group may be due to physical
or mental causes, or a combination of both. Some of the
physical causes are lowered vitality due to bad nourishment
or unhealthy home surroundings, and adenoids with asso-
ciated deafness. In other cases of this group there is no
associated physical cause, and the condition seems entirely
mental.
Treatment of Backward Children. — Ascertain whether
there are any physical defects present, and remedy them.
The general health must be attended to, and adenoids or
any other removable cause must be treated.
Good results have been obtained by sending these children
to open-air recovery schools.
It has been pointed out by many medical authorities that
it is impossible for all children in the elementary schools
to follow the same course of instruction and reach the same
goal, and thus the curriculum of the school must be altered,
220 HYGIEM:
so that there is more individual attention given to each
child.
The Congenitally Word-Blind and Word-Deaf. — These are
conditions of mental deficiency arising from lack of develop-
ment of certain special areas in the cerebral cortex. It
will be remembered in describing the function of the
cerebral cortex that certain areas were said to be con-
cerned with special forms of consciousness.
Word- blindness will result from affection of the word-
seeing centre, and the child will be unable to remember
or recognize letters or words. It is useless to try and teach
a word-blind child to read or write, though they will be
able to draw and recognize pictures, and even do arithmetic.
Word-deafness will result from lesions of the auditory
word centre, and the child will be unable to understand or
remember what is said to him, though he will be able to
understand and remember what he reads. They are often
supposed to be deaf or imbecile, but they are not. In such
a condition excellent results are obtained by special training
in articulation and writing.
CHAPTER VII
RELATION OF SENSES TO THE NERVOUS SYSTEM—
THEIR TRAINING AND DEVELOPMENT
THE sense organs are the means by which we become
conscious of the changes in the world around us, and they
convert the external stimuli which reach the body into nerve
impulses, which travel along the nerves to the cerebral
cortex, where the changes that result in consciousness take
place.
Sound is caused by the vibrations of air, and when these
vibrations fall on the ear they are converted into nerve
impulses, which are carried to the brain and give rise to a
sensation of sound.
Light is due to vibrations of the ether, a substance
which permeates all things ; these vibrations are converted
by the eye into impulses, which are carried along the optic
nerve to the brain and give us a sensation of sight.
Thus the sense organs are means by which these physical
stimuli are changed to nerve impulses.
THE SENSE OF SIGHT.
Structure o! the Eye. — The eyeball lies in the cavity of
the orbit, the walls of which protect it, except in front,
where it is guarded by the eyelids. The eyelid is a fold of
skin strengthened by a thin layer of muscle and fibrous
tissue, while on the inner side fchere is a thin mucous mem-
221
222
HYGIENE
brane called the * ' conj unctiva." Along the edge of the eyelids
are the eyelashes, and just behind these open the ducts of
small glands. A stye is due to blocking and inflammation
of one of these glands. The eyelashes protect the eye from
too much light, and also from dust, and give warning of the
approach of insects, etc.
B
H
FIG. 80. — DIAGRAM SHOWING THE STRUCTURES SEEN nr A CROSS-
SECTION <>F THE EYEBALL.
A, Cornea ; B, sclerotic ; C. iris ; D, crystalline lens ; E, ohoroid ;
F. ciliary processes ; 0. entrance of optic nerve ; H, retina ; K, hya-
loid membrane ; L, suspensory ligament of the lens.
The eyeball has three coats, or layers, and from without
inwards they are —
1. The sclerotic and cornea.
2. The choroid and iris. ,w
3. The retina.
THE SENSES AND THE NERVOUS SYSTEM 223
The sclerotic, or white of the eye, is a tough, white,
opaque membrane forming the greater part of the wall of
the eyeball. In front this fibrous capsule of the eye,
though it does not change its essential character, becomes
transparent, and thus allows light to pass through it ; it is
FIG. 90. — EXTEINSIC MUSCLES OF THE EYE VIEWED FROM
ABOVE.
A, Eyeball ; B, superior oblique ; C, internal rectus ; D, superior rectus
E, external rectus ; F, bony wall of orbit.
called the cornea. The sclerotic is the only part of the eye
that is capable of resisting any strain, and if it gives way
all the other structures of the eye will certainly do the
same.
The front of the cornea is lined by epithelium continuous
with that which forms the conjun ctiva on the inner surface
224
HYGIENE
of the eyelids. The cornea is more convex than the
sclerotic.
The middle coat of the eyeball is formed by the choroid
and iris. The choroid lies internal to the sclerotic, and
consists of a network of bloodvessels arranged in a complex
manner, bound together by connective tissue, and towards
its inner side there are a number of branched, connective-
Fio. 01.— EXTRINSIC MUSCLE or THE EYE: LATERAL VIEW.
A, Eyeball ; B. superior oblique ; C, superior rectus ; D, external rectua
E, internal rectos ; F, inferior rsotui ; 0, bony wall of the orbit.
tissue corpuscles containing a large amount of black
pigment. The choroid lines every part of the sclerotic ;
anteriorly, Just at the junction of the sclerotic with the
cornea, the ohoroid is thrown into numerous ridges called
the ciliary processes. The choroid is continuous anteriorly
with the iris, which forms a perforated diaphragm in front
of the lens.
The iris is a circular contractile diaphragm, situated
THE SENSES AND THE NERVOUS SYSTEM 225
behind the cornea and in front of the lens. The round hole
in the middle is called the pupil. The iris is made up of a
supporting structure of fibrous tissue, involuntary muscular
tissue d'sposed in circular and radial layers, and the whole
is covered by a layer of epithelium, which on the posterior
surface contains pigment and gives the characteristic colour
to the eye. The contraction of the circular layer of muscle
of the iris causes constriction of the pupil, while contraction
of the radial layer causes dilatation of the pupil.
The innermost coat of the eye is formed by the retina.
It is a very delicate and thin membrane, and has a very
complicated structure. The optic nerve enters the eyeball
behind and on the nasal side ; the fibres of this nerve, after
it has passed through the coats of the eye, spread out as
fine non-medullary fibres, and form the inner layer of the
retina. External to this there are various layers formed by
nerve cells and their intertwining dendrites ; the layer that
is most external but one is called the " layer of rods and
cones." These are probably the structures that are changed
by the influence of light, and this acts as a stimulus to the
nerve cells. Outside the rods and cones is a layer of pigment
cells ; these are concerned in the formation of " visuil
purple," which is present in the rods.
Internal to the retina is a thin membrane called the
hyaloid membrane ; anteriorly this becomes thickened, and
then divides to surround the lens ; the part which g^es an-
terior to the lens is called the suspensory ligannnt of the
lens.
The crystalline lens is situated just behind the iris ; it is
a thick biconvex lens contained within a capsule, and this
capsule is adherent all round to the ciliary processes. It is
composed of long ribbon-shaped fibres disposed in a com-
plicated manner.
The lens divides the cavity of the eyeball into two. The
small anterior chamber lies between the lens, iris, and the
cornea, and contains a watery fluid called the aqueous
humour. The large chamber situated behind the lens
15
226 HYGIENE
contains a clear, jelly-like substance called the vitreous
humour. This is not called the " posterior chamber," for
that name is reserved for a small space behind the iris,
between it and the circumference of the lens.
In order to understand the structure of the eye, you
should procure half a dozen bullock's eyes from your
butcher. They will be found to be covered externally by a
layer of fat ; remove this, and carefully dissect out the
muscles on the outer side of the sclerotic ; also clean up the
optic nerve, which will be found to pierce the sclerotic
behind and to the inner side.
After the eyes have been cleaned, place them under
water, and with a sharp razor cut one of them from front
to back, and another transversely just behind the cornea.
Then the various parts of the eye should be identified and
studied.
Muscles of the Eye. — The muscles of the eyeball are
divided into extrinsic and intrinsic : the former are situated
outside the eyeball, while the latter are placed inside.
The intrinsic muscles are the ciliary muscle, the dilator
and constrictor of the pupil.
The ciliary muscle arises at the junctions of the cornea
and sclerotic, and passes to the ciliary processes ; it is
therefore circular in shape. This is the muscle which, when
it contracts, brings about accommodation. It is supplied
by the third cranial nerve.
The dilator of the pupil is made up of the radial fibres
of the muscle of the iris ; its contraction causes dilata-
tion of the pupil. It is supplied by the sympathetic
system.
The constrictor of the pupil is made up of the circular
muscle of the iris ; its contraction causes constriction of
the pupil. It is supplied by the third cranial nerve.
The extrinsic muscles will be found on the outer side of
the eyeball, and attached just behind the cornea to the
sclerotic, and also, when the eye is in its place, to the
bony wall of the orbit. There are six extrinsic muscles
THE SENSES AND THE NERVOUS SYSTEM 227
of the eyeball — the superior, inferior, external, and internal
recti, the superior and inferior oblique muscles. The recti
muscles pass straight from the back of the orbit to be
inserted in front of the eyeball. The external rectus is
on the outer side, and its contraction causes movement
of the eye outwards ; the internal rectus is on the inner
side, and moves the eye inwards ; the superior and inferior
recti are placed, respectively, above and below the eyeball,
and their contractions cause, respectively, movements of
the eye upwards and downwards.
The two oblique muscles are inserted, slantwise, one
Fia. 92. — DIAGRAM ILLUSTRATING THE MECHANISM OF
ACCOMMODATION.
A, Comea ; B, ciliary muscle ; C, lens when viewing a distant object ;
D, lens when viewing a near object (accommodated).
above (superior), and one below (inferior), the eye. Their
contraction causes rotatory movement of the eye round its
axis.
Accommodation. — The eye is practically a photographic
camera. Images of external objects are formed on the
retina, and the impressions of such images are carried to
the brain. The retina is the sensitive plate upon which the
image is formed and is focussed in position. To have a
definite image of an object upon the retina, the rays of
light from that object must be brought to a focus on the
retina, and there must be some mechanism by which images
228 HYGIENE
of objects at various distances are brought to such a focus ;
and this mechanism, by which we adapt our sight to near
and distant objects, is called accommodation. To under-
stand this process, it would be well for us to take a physical
example of a similar change. If you take an ordinary
magnifying-glass (convex lens), and hold it at a certain
distance from a screen or a wall in a dark room, and
place a lighted candle on the side of the glass farthest
from the screen, it will be easy to adapt the distances of
the lens and candle in such a manner that an inverted image
of the candle flame shall be tin-own upon the screen. If
the candle be brought nearer to the lens, the image on the
Fio. 93. — DIAGRAM SHOWING TUB PATH or PARALLEL RAYS OP LIGHT
ix A NORMAL EYE.
Note how they are brought to a focus on the retina.
Mteen beoomee blvnd, and ONI be mad.- «-K-ar a^.-iin <-ith«T
by moving the lens towards the candle or by replacing the
lens by one of greater curvature. The distance between the
lens and the retina in the human eye cannot be altered as
in a photographic camera, therefore the first of the above-
mentioned methods cannot be adopted ; but the convexity
of the lens can be altered, and this is what happens in
accommodation. The essential point in accommodation is,
therefore, an increase in the convexity of the lens, and this
increase, as has been proved by experiment, takes place
in the anterior surface of the lens. The ciliary muscle,
described above, arises from the corneo-sclerotic junction,
THE SENSES AND THE NERVOUS SYSTEM 229
and is inserted to the ciliary processes, to which is also
attached the suspensory ligament of the lens. Contrac-
tion of the ciliary muscle causes a forward movement of
the ciliary processes and the relaxation of the suspensory
ligament of the lens ; and this results in the lens bulging
forward by its own elasticity, because the suspensory liga-
ment is rather tight, and normally compresses the lens.
The convexity of the cornea and the lens, and the distance
between the lens and the retina, are so arranged in the
human eye that parallel rays of light are brought to a focus
on the retina. If the rays are convergent — that is, coming
from a near object — they will not be brought to a focus
on the retina unless there is an increase in the convexity
of the lens, and this increase is brought about by accom-
modation.
Convergence. — When we look on a near object the eyes
converge, and this is of great importance, because the
image of the object is thus formed on the corresponding
parts of the two retinae ; and if this were not so we should
see double. This can be proved by experiment. Look
at any object, and lightly press the globe of the eye ;
the consequent displacement of the eye will make the
object appear double. The muscular sensation associated
with convergence helps us to judge the distance of
objects.
Cause of Defective Vision— Eyestrain. — The factors
concerned in the causation of defective eyesight are
numerous and complex, and have not by any means been
finally ascertained. Defective vision is generally acquired,
but high degree of myopia tends to run in families. The
main causes are the faulty methods of education, especially
in the infants' department. Work involving excessive
accommodation and convergence causes an increased tension
within the eyeball, and the contraction of the extrinsic
muscles tends to distort the eyeball, especially in young
children. The chief causes of defective vision may be
grouped as follows ;
230 HYGIENE
1 . Bad general health, inadequate nutrition, and constitutional dim* HP.
2. Methods of education involving near and strained vision.
'5. Too little or too much light, or when the light falls from the wrong
notion.
1. Faulty position of the pupils relative to the blackboard, resulting
n excessive contraction of some of the extrinsic muscles of the eye.
5. Faulty desks and scats ; this leads to bad posture.
Hence bad light, small print, long hours at work, all
tond to produce eyestrain which results in defective vision.
Defects of Vision. — A normal eye is able to focus on the
retina, without accommodation, all parallel rays of light
that reach the cornea, and distant objects are therefore
FIG. 94.— COURSE or PARALLEL RATS or LIGHT IK A HYPERMETROPIC
EYE ( LONG-SIGHTED).
Note how the rays of light arc brought to a focus behind the retina.
clearly seen even when the eye is at rest. The rays of light
falling on the cornea from a point 20 feet away are
practically parallel.
Long-sighted Eye, or Hypermetropia. — Hypermetropia
is a congenital defect, common amongst the younger
children. The antero-posterior axis of the eyeball is too
short, and parallel rays of light, when the eye is at rest,
are brought to a focus behind the retina. In order to have
a clear image on the retina, the hypermetropic eye has to
perform for distant vision what the normal eye does for
near vision — that is to say, it has to accommodate. If
the long-sighted eye turns its attention to near objects, it
will either not see them clearly or it will accommodate
THE SENSES AND THE NERVOUS SYSTEM 231
excessively. This excessive accommodation is associated
with excessive convergence, and should be treated by
appropriate spectacles (convex lens) and avoidance of
near work.
Signs of Hypermetropia. — The child complains of head-
ache. He blinks and waters at the eyes. He can dis-
tinguish distant objects with ease ; but, when reading, he
does so accurately for a few lines, and then makes mistakes
or stops, and will often complain that the words " seem to
move about."
Short-sighted Eye, or Myopia. — In this condition the
antero-posterior axis is too long, and therefore parallel rays
reaching the cornea are brought to a focus in front of
FIG. 95. — DIAGRAM SHOWING THE PATH OF PARALLEL RAYS OF LIGHT
IN A HYPERMETROPIC EYE AFTER CORRECTION BY MEANS OF A
CONVEX LENS.
the retina. It is not a congenital, but an acquired,
condition, though the predisposition is often hereditary.
There are several factors at work in producing myopia :
congenital or acquired weakness of the coats of the eye ;
excessive accommodation, convergence, and congestion.
The child may have a congenitally weak sclerotic,
and when this is exposed to excessive accommodation
and convergence it gives way, and causes the lengthen-
ing of the antero-posterior diameter of the eyeball. It
generally begins to become troublesome at the age of
nine or ten. In nutritional disorders and constitutional
diseases, the sclerotic shares the general weakness of the
232 HYGIENE
body, and is less capable of withstanding the strain than
the normal sclerotic. Hence myopia is often seen amongst
weakly and underfed children, and it frequently happens
that a child whose vision was normal acquires myopia
as a result of an acute illness followed by the strain of
school work. Some authorities doubt whether convergence
and accommodation produce myopia unless there is
either a congenital or acquired weakness of the sclerotic.
But when the latter conditions are present, they certainly
are important determining factors in its causation. Con-
vergence acts by the extrinsic muscles pulling on the
sclerotic, and also by the increased intra-ocular tension
Fio. 96.— DIAGRAM SHOWING THE PATH or PARALLEL RAYS or LIGHT
nr A Mronc EYE.
Note how the rays of light are brought to a focus in front of the retina.
associated \\ith near \\ < »rk. A« •« •«.min«»<l;it i»n lia> lout; IK-CM
indicted as a cause of myopia.
Congestion or overfilling of the small vessels of the
eye is an important cause of the stretching of the sclerotic,
which results in short-sightedness. This is brought about
by mental fatigue or unnatural posture due to improper
light and bad desks.
Signs of Myopia. — In its early stages careful eye-testing
is required to detect it. When the condition is pronounced,
the child, when reading, holds his book close to his eyes.
He is able to read when the book is in this position, but
frequently makes mistakes when reading from the board
THE SENSES AND THE NERVOUS SYSTEM 233
Headaches and pains in the eyes are often associated with
this trouble.
Treatment of Myopia. — The strain of near work should
be avoided, and suitable glasses with biconcave lenses
should be worn.
Testing of Eyesight. — The acuity of vision is generally
tested by Snellen's test types. A person with average
acuity of vision ought to be able to read the top letter of
the type at a distance of 60 metres, the second line at
36 metres, the third at 24 metres, the fourth at 18 metres,
and so on. In some test-cards the distances are recorded
in feet, and generally the smallest letters are such that can
FIG. 97. — DIAGRAM SHOWING THE PATH OF PARALLEL RAYS OF LIGHT
IN A MYOPIC EYE AFTER CORRECTION BY MEANS OF A BICONCAVE
LENS.
be read by a normal eye at a distance of 20 feet. The child
is made to stand at a distance from the test-card equal to
that at which he should be able to read the smallest type
on the card, and this distance is generally 6 metres or
20 feet. He is then asked to read the letters row by row,
and if his vision is normal he will be able to read all the
types at this distance. If distances are recorded in metres,
and the child can only read the 24 metre line at a distance
of 6 metres from the types, his vision is defective. The
numerical convention used to record this defect is a fraction
in which the numerator is the distance in metres the child
is from the types, and the denominator is the distance at
which he ought to be able to read the last line which he
HYGIENE
T B
D L N
P T E R
F Z B D E
O E L Z T G
L P O R F D Z
Fio. 08. — SBILLKI'S TISI TYPES RIDCCD a Sam.
THE SENSES AND THE NERVOUS SYSTEM 235
has succeeded in reading. The normal child's vision would be
V=-£. If, however, at a distance of 6 metres he would only
be able to read the 24 metre line, his vision would be
recorded V = -26T.
Astigmatism. — This is one of the optical defects of the
eye, and is due to an irregularity in the convexity of the
cornea, so that the curvature is greater from above down-
wards than from side to side, or vice versa. Most eyes are
slightly astigmatic, but when the condition is marked it
prevents distinct vision, because the rays of light passing
through the different planes of the cornea will not be
brought to a focus at the same point. A child whose
cornea has a greater convexity in the vertical than in the
horizontal plane, looking at the face of the clock, will see
the figures XII and VI (vertical) quite clearly, while the
figures III and IX (horizontal) will be blurred. Severe
forms of astigmatism cause " eyestrain " and headaches,
and should be corrected by the use of proper cylindrical
glasses.
Squint, or Strabismus. — "Squint" is the term applied to
the condition in which the two eyes are not directed to
the same point, and one eye may turn more inward or more
outward than the other. It often arises very early in
infancy. Long sight, or hypermetropia, is frequently
associated with squint, and both these conditions are
aggravated by the excessive accommodation required for
near work in school. Squint sometimes follows an illness —
e.g., diphtheria causes paralysis of some of the eye muscles,
which results in squint — but this form is generally only
transitory. It is imperative that squint should be recognized
and treated early, because the eye that habitually squints
tends to deteriorate, and may eventually become blind.
External Eye Diseases. — The following are a few of the
most common diseases of the eyelids and conjunctiva :
Blepharitis ("Sore Eyes" or "Red Eyes ").— This is
the term applied to the inflammatory condition of the
margin of the eyelids, of the follicles of the eyelashes and
236 HYGIENE
their glands, and of the portion of the skin and conjunctiva
bordering the margin. It is one of the most common forms
of eye disease occurring in children, and is seen more espe-
cially amongst the poorer classes. It is frequently caused
by measles and scarlet fever, and its course is prolonged
and intensified by the bad general conditions of the child
and his unhealthy environment. Pediculosis of the eyelids
is sometimes responsible for this form of disease. Certain
defects of vision or continuous overstrain tend to intensify
it, and may be directly responsible for it. The child suffer-
ing from this condition requires medical treatment, and the
parents should be instructed that great care and cleanli-
ness are necessary.
Stye. — A stye is a small abscess at the margin of the
eyelid, usually arising round one of the sebaceous or other
glands. It is most frequently found amongst poorly -fed,
weakly and neglected children. It gives rise to a great
deal of pain, and children suffering from this complaint
should be medically treated and their vision carefully tested.
Conjunctivitis. — Inflammatory condition of the conjunc-
tiva may be mild or severe ; it may vary from slight redness
to very acute disease, resulting in the destruction of the
conjunctiva and underlying cornea. This disease may be
due to several different conditions — irritation from dirty,
ill- ventilated rooms, exposure to strong light, or acute
infection by various microbes. The last variety is us ually
very infectious, and will spread throughout the school, and
any child suffering from this condition should be sent to
a medical officer for treatment.
Children whose Eye Conditions require treatment by
medical officers —
1. All children with congested or sore eyes.
2. All those who have difficulty in reading from the blackboard.
3. All those who blink to enable them to see anything distinctly.
4. Those who, when reading, hold the book close to the eyes.
5. Those who, when reading, hold the book at an arm's length.
6. Those who complain of headaches, more especially after reading.
7. Those who squint.
CHAPTER VIII
RELATION OF SENSES TO THE NERVOUS SYSTEM—
THE SENSES OF HEARING, ETC.
THE SENSE OF HEAEING.
THE ear is the means by which sound waves are con-
verted into nerve impulses, which are carried to the brain
by the eighth cranial or auditory nerve, and by changes
in the cerebral cortex we become conscious of sound.
Sound is produced by rapidly vibrating bodies. The
vibrations are transmitted by the air, and stimulate the
sensitive cells in the internal ear, where they are converted
into nerve impulses.
The pitch of a sound depends upon the rate of vibration,
the timbre upon the character of the vibration ; the loud-
ness depends upon the amplitude of vibration.
Physiological Anatomy of the Ear. — The ear consists of
three portions : outer, middle, and inner.
The External Ear. — The auricle, or flap, is made up of
skin supported by a plate of elastic cartilage of peculiar
shape. In its deepest part is an opening leading into a
bony passage lined by skin, called the " external auditory
meatus." At the inner end of the passage lies a circular
membrane set like a drum-skin in a ring of bone ; this is
called the " drum of the ear," or the " membrana tympani."
This membrane separates the external from the middle
ear. The skin lining the external auditory meatus contains
glands, which secrete wax. This wax sometimes accumu-
lates to such an extent as to block the passage and cause
deafness.
237
238 HYGIENE
The Middle Ear. — This is a small cavity lined by a mucous
membrane, and situated inside the temporal bone. Its
outer wall is formed by the membrana tympani. Its inner
wall is formed of a plate of bo ne perforated by two openings
— the oval window (fenestra ovalis), and the round window
(fenestra rotunda). Both these are covered by membranes
and lead to the internal ear. F rom the floor of the middle
ear there runs downwards into the pharynx a tube, called
the "Eustachian tube." The function of this tube is to
Fio. 99. — DIAGRAM SHOWING THE STRUCTFRE SEEN IN A SECTION
THROUGH THE AUDITORY APPARATUS.
A, External auditory canal ; B, external ear ; C, middle ear containing
the auditory ossicles ; D, the internal ear ; E, auditory nerve ;
F, Eustachian tube.
keep the pressure of air on each side of the membrana
tympani equal to the atmospheric pressure. When a
person has a cold or adenoids, the mucous membrane of
the tube is swollen ; its lumen is blocked, and the oxygen of
the air inside the middle ear is absorbed. This results in
unequal pressure on the two sides of the drum of the
ear, which causes it to be drawn inwards, and the result is
deafness.
THE SENSES AND THE NERVOUS SYSTEM 239
Three small bones stretch across the middle ear. The
outermost is called the malleus, and is attached to the
tympanic membrane. On the inner side of the malleus,
and attached to it, is the incus. Attached to the incus is
the stapes. The stapes is shaped like a stirrup, and the
foot-piece of the stirrup fits into the fenestra ovalis, where
it is attached to the membrane that spreads over it. This
chain of bones forms a kind of bent lever by which the
oscillations of the membrana tympani are transferred to
the membrane covering the fenestra ovalis. They conduct
the slight vibration of the tympanic membrane produced
FIG. 100.— THE THREE EAR
OSSICLES.
A, Malleus ; B, incus ; 0, stapes.
FIG. 101. — BONY LABYRINTH.
A, A, A, Three semicircular
canals ; B, vestibule ; 0, cochlea.
by a low sound without change, but they damp down the
vibrations produced by a loud sound, and thus they
protect the inner ear from injury.
There are two slender muscles, the tensor tympani and
stapedius, contained in the tympanic cavity, and they are
connected with, and may act upon, the ossicles. The
former is attached to the handle of the malleus, and is
able to influence the tension of membrana tympani. The
stapedius is attached to the neck of stapes.
The Internal Ear.— The internal ear consists of the bony
and membranous labyrinth.
The bony labyrinth is made up of a series of cavities
hollowed out in the temporal bone, called the " vestibule,"
the " cochlea," and three " semicircular canals."
240 HYGIENE
The vestibule forms the central portion of the osseous
labyrinth into which the cochlea and semicircular canals
open.
The cochlea is a tube coiled two and a half times round
a central column called the " columella." A shelf of bone
protrudes from the columella, and partially divides the
cavity of the cochlea ; the division of the cavity is com-
pleted by the basilar membrane.
The semicircular canals are three in number, and are
situated above and behind the vestibule. They are dis-
H
FIG. 102. — MEMBRANOUS LABYRINTH.
A Superior semiciitmlar canal ; B, posterior semicircular canal ; C, ex-
ternal semicircular canal ; D, utricle ; E, saccule ; F, membranous
cochlea.
tinguished from each other by their position, and are
called the " superior," " posterior," and " external." Each
canal has a small swelling at the end where it opens to the
vestibule called the ampulla.
The membranous labyrinth assumes more or less closely
the shape of the bony labyrinth in which it is situated. It
contains a fluid called the endolymph, while the interval
between it and the bony labyrinth is called the perilym-
phatic space, and is occupied by a fluid called perilymph.
THE SENSES AND THE NERVOUS SYSTEM 241
The position of the membranous labyrinth in the vestibule
is divided by a deep groove into two portions called the
utricle and saccule. The membranous cochlea arises from
the saccule, and passes into the bony cochlea. The floor
of the membranous cochlea is formed by the basilar
membrane. The roof is formed by the membrane of
Reissner, which is a delicate membrane covered on both
surfaces by a layer of epithelium. The outer wall is formed
by the periosteal lining of the bony cochlea. In the
membranous cochlea lies the organ of Corti.
The organ of Corti consists of a series of modified epithe-
lial cells planted upon the basilar membrane. The pillars
E C H H
FIG. 103. — ORGAN OF CORTI.
A, Membrana tectoria ; B, lamina spiralis ; C, basilar membrane ;
D, inner rod of Corti ; E, outer rod of Corti ; F, inner hair cells ;
G, outer hair cells ; H, H, H, supporting cells of Deiters ;
K, auditory nerve.
or rods of Corti, in two series (inner and outer), slope
against each other like the rafters of a roof, and with the
basilar membrane form a tunnel which runs from the base
to the apex of the cochlea. On each side of the rods of
Corti lie the hair cells, around which are the fibres of the
auditory nerve, and supporting these there are large epithe-
lial cells.
Causes of Defective Hearing.— The causes of deafness in
children may be enumerated as follows : 1. Adenoids
blocking up the Eustachian tube ; the oxygen ill the middle
16
242 HYGIENE
ear is absorbed, and results in inequality of the pressure on
the two sides of the membrana tympani. 2. Accumula-
tion of wax in the external auditory canal. 3. Middle ear
disease, arising as an infection from the throat along the
Eustachian tube. 4. Disease of the internal ear.
5. Damage to the auditory nerve. 6. Defective develop-
ment or injury to the hearing centre . situated in the
brain.
Many children seem deaf owing to mental deficiency ;
they are unable to distinguish different sounds, although
able to hear them quite well. On the other hand, some
children appear mentally defective who are in reality only
backward because they are not able to hear properly.
All cases of deafness recognized by the teacher should
be sent to the medical officer for further investigation and
treatment.
Ear Conditions common in School-Children. — Diseased
conditions of the ears are common in school-children ; this
is shown by the very great increase in the number of children
attending the aural departments of the large hospitals in
London, since the medical inspection of school-children
was begun. It is of the greatest importance that symp
toins associated with the ear should receive immediate
attention : for example, earache may be simply due to a
cold in the head ; on the other hand, it may be a sign of
serious condition of the auditory apparatus.
Another common condition is discharging ears. Parents
do not realize the danger that arises from ear discharge.
It is generally due to a chronic inflammatory condition of
the middle ear, which might at any time spread through the
thin bony roof of the middle ear to the brain. Diphtheria
and scarlet fever are generally accompanied by inflamed
condition of the mucous membrane of the throat. This
may spread to the middle ear along the Eustachian tube,
and set up inflammation in that cavity, which may result
in an ear discharge. Sometimes this discharge is infectious,
and may cause an epidemic in the schools. All children
THE SENSES AND THE NERVOUS SYSTEM 243
with discharging ears and earache should be sent to the
medical officer for investigation and treatment.
Tests for Hearing. — All children whose hearing is defec-
tive should be sent to the medical officer for investigation
and treatment. There are one or two simple tests of
hearing that can be performed by the teacher, either by
means of the voice or by a watch. The pitch and loudness
can be regulated more effectively in a whisper than in the
usual speaking voice ; hence the voice test should always be
performed by means of a whisper. Each ear should be
tested separately, and it is advisable that all the children
should be examined by the same teacher. The examiner
should first of all ascertain the distance at which his forced
whisper can just be heard by children possessing good
hearing, and if the maximum distance be, say, 30 feet, a
straight line of this length, divided into feet, should be
drawn on the floor of the classroom. The child stands
sideways at one end of this line, with the ear to be tested
turned towards the examiner, and the other ear carefully
stopped by the finger of an assistant. The examiner then
whispers single words, and should the child be unable to
hear him distinctly, or make a mistake, the examiner
should move a foot at a time nearer the child, until the
latter clearly understands the word whispered. The
distance between the examiner and the child is measured
and recorded.
The alternative test is performed by means of a watch ;
and since the ticks of various watches differ in pitch and
loudness, the same watch should be used for all experi-
ments. As in the voice test, the maximum distance at
which the ticking is heard by children of good hearing is
recorded. In this test the child should have his eyes
covered, and the watch should be held at a distance from
the ear and gradually brought nearer. The child is asked
to make a sign the moment he hears the ticking, and the
distance between the child and the watch should be ascer-
tained. The hearing of a child is represented by the ratio
244
HYGIENE
of this distance in feet to the length of the line drawn
on the floor prior to the commencement of the
experiment.
THE SENSE OF SPEECH.
Structure of Vocal Organs. — The larynx, or voice-box,
lies at the top of the trachea, or windpipe. It opens into
the pharynx above and the trachea below. The gullet
lies at the back of the larynx.
Obtain from your butcher a sheep's tongue with the
larynx, windpipe and gullet attached. The gullet will be
Fio. 104. — POSTERIOR VIEW
OF THE CARTILAGES OF THE
LARYNX.
A, Epiglottis ; B, thyroid
cartilage ; C, arytenoid
cartilages ; D, oriooid.
Fio. 105.— ANTERIOR VIEW OF
THE CARTILAGES OF THE
LARYNX.
A, Hyoid bone; B, thyroid
cartilage; 0, oricoid car-
tilage.
attached behind, and the larynx will be covered by thin
bands of muscle. These muscles pass from the prominence
of the larynx either upwards to the hyoid or downwards
to the sternum, or breast- bone. The hyoid is a small bone
embedded in the muscle below the tongue ; it is slung to
the skull by muscle and ligaments, and forms a means of
attachment for muscles which pass upwards to the tongue
and downwards to the cartilage or larynx and sternum.
THE SENSES AND THE NERVOUS SYSTEM 245
Dissect the muscles and fat off the front and sides of
the larynx, and expose its cartilaginous framework. Just
above the trachea lies the cricoid cartilage ; it is shaped
like a signet ring, the narrow part of the ring being in front,
and the broad part behind. It is this broad part which
forms the posterior wall of the larynx, and on the top of it
lie the two arytenoid cartilages. These are two pyramidal-
shaped cartilages, and are each attached to the cricoid
cartilage by a final joint. The thyroid cartilage is a broad
V-shaped cartilage with the angle anteriorly. The sides
of the thyroid cartilage are prolonged above and below
into horns. The upper pair of horns is bound to the arch
of the hyoid bone ; the lower part is articulated by a pivot
joint to the outside of the cricoid cartilage. The epiglottis
will be seen as a thin leaf -like lumina of yellow fibro -cartilage
covered b}r a mucous membrane ; it is placed behind the
tongue and the body of the hyoid bone, and in front of the
upper aperture of the larynx.
A number of very important muscles are attached to the
cartilages of the larynx. On each side the crico-thyroid
muscle will be seen ; this runs from the thyroid to the cricoid
cartilage, and when it contracts it causes a tilting of the
cricoid, and thus tightens the vocal cords.
Muscles will be seen passing from the cricoid to the
arytenoid cartilages. These cause the arytenoids to swivel
round upon their pivot joints, and by this means the vocal
cords are brought nearer together or farther apart, and
thus lessen or increase the aperture between them, which
is called the " glottis." The two arytenoids are connected
together by muscle, and this, when it contracts, causes
approximation of the vocal cords. Another muscle on
each side runs from the thyroid to the arytenoid cartilage,
and some of its fibres are directly attached to the vocal
cords, and by this means the cords can be slackened either
in part or in the whole of their length. With a sharp knife
bisect the larynx and study its interior. It will be found
to be lined by a mucous membrane, and divided into three
246 HYGIENE
portions by two elevated folds of mucous membrane,
which extend from before backwards, and project inwards
from each side of the cavity. The upper pair of folds are
called the false vocal cords ; the lower pair receive the name
of true vocal cords. The latter are the chief agents in the
production of the voice, and the muscles mentioned are so
arranged as to cause changes in their relative position and
degree of tension.
Interior of the Larynx in Man. — The glottis is examined
in a living person by means of a small mirror placed on a
long handle, and passed to the back of the throat. The
observer by means of a tape fixes a concave mirror over
his forehead. This mirror is pierced by openings, so that
the observer can see the image of the glottis formed by
the small mirror inside the throat, which is illuminated by
a light from a strong lamp, having been reflected from the
mirror on the forehead.
The Production of the Voice. — Sound is produced in the
larynx by the vibrations of the vocal cords. It was said
at the beginning of the chapter that the pitch of a sound
depends upon the rate of vibration, the loudness upon the
amplitude, and the timbre, or character, upon the form of
vibration.
By means of physical instruments it can be proved that
short strings vibrate at a quicker rate than long strings,
and thus the pitch of a note evolved by a string is inversely
proportional to the length of the string. Similarly, the
loudness will depend upon the amplitude of vibration,
while the character depends upon the form of vibrations.
The same holds true for the vocal cords of human subjects.
Man has longer vocal cords than a woman, and hence
his voice is deeper.
The loudness of the voice depends upon the strength of
the current of air setting the cords in vibration, because
the greater the force, the greater the amplitude.
The quality of the voice depends upon the character of
the vibration, and hence the thickness, elasticity, and
THE SENSES AND THE NERVOUS SYSTEM 247
smoothness, of the cords, and the shape of the cavities of
mouth, pharynx, and larynx, will influence it.
Song is produced by very complicated muscular move-
ments, which can only be carried out with accuracy after
continual practice and years of training. The exact degree
of tension must be given to the vocal cord to produce the
required pitch, and the quality at the same time must
be determined by the muscles of the mouth and throat.
The singer must learn to execute these movements with
great rapidity and precision. The range of the voice
seldom exceeds two and a half octaves.
Production of Speech. — Speech is voice modulated by
the throat, tongue, and lips. Voice may exist without
speech, but this is only true, however, if the term " voice "
be restricted to sound produced by vibration of the vocal
cords. In whispering, the slight sound produced by the
air passing through the air-passages is modified into speech
by movements of the tongue and lips.
Differences in the shape of the cavity of the mouth
and the form of its opening are the factors which cause the
variety of vowel sounds. Pronounce the pure vowel
sounds e as in " he," a as in " ay," a as in " ah," o as
in " oh," oo as in " coo," and notice that they are pro-
duced by varying the form of the cavity and the shape
of the opening of the mouth.
The consonants are produced by closing, more or less,
certain exits on the outgoing blast. If the exit be partly
closed, and the air rushes through with a hiss, the result is
an "aspirate" ; thus, /, v, and w, are produced by partial
closure with the lips ; s, z, I, sch, and th, by the tongue
and hard palate, and ch by the tongue and soft palate.
The consonant h is produced by increasing the expiratory
force with which the vowel is spoken.
M and n are produced by sending the current of air
through the nose ; in the case of m the lips are closed, while
to pronounce n the tongue is applied to the palate. The
consonants 6, p, t, d, k, g (hard), are called " explosives,"
248 HYGIENE
because the mouth is first closed, and then suddenly burst
open. In the case of b and p the lips close the mouth :
in t and d the tongue is applied to the teeth or front part of
the palate ; while in k and g hard the middle or back of the
tongue is forced against the back of the palate.
Speech Defects — Stammering. — This is a spasmodic affec-
tion of the organ concerned in speech, in virtue of which
the enunciation of words becomes suddenly checked. It
is much more common among boys than girls.
Stuttering. — Where there is spasmodic repetition of
initial syllables of words, it is due almost entirely to
imperfect breathing, and is more amenable to treatment
by respiratory exercises than stammering.
Motor Aphasia. — This arises from imperfect develop-
ment of the speech centre of the brain, and the child is
unable to control and co-ordinate the various muscles
which take part in the mechanism of speech.
Habitual Speech Defects. — Defects of this kind are very
common, and are due only to habit. The child may
imitate the language of its parents and associates, or he
may have an habitual lisp or the affected speech of spoiled
children. These are only correctly identified by knowing
the type of child and its surroundings, and by compelling
him to imitate correct speech.
Speech Defects due to Adenoids. — There is a marked nasal
intonation, and in the younger children the speech is thick
and indistinct, and pronunciation is defective.
THE SENSE OP SMELL.
The olfactory sense organ lies in the upper parts of the
nose, and consists of elongated cells, each of which bears on
its free end a tuft of hair-like processes, while at its nasal
end it is continued into a nerve fibre that passes through the
upper wall of the nasal cavity to reach the cranial cavity.
It has been held that smell is due to vibratory movement of
some medium, because it can be transmitted through space
THE SENSES AND THE NERVOUS SYSTEM 249
like light and sound, but this view is erroneous. Sensation
of smell is elicited by small particles being carried up the nose,
which, after solution in the moisture of the mucous mem-
brane, act chemically upon the sensitive hairs described
above.
THE SENSE OF TASTE.
At the back of the tongue a few large papillae surrounded
by a groove will be seen. These are called " circumvallate
papillae." The entire dorsal surface of the tongue will be
I II
FIG. 106. — ANATOMY OF THE NASAL CAVITY.
I. Outer wall : A, base of skull ; B, branches of olfactory nerve :
C, inferior turbinate bone ; D, palate-bone. II. Inner wall : A, olfac-
tory bulb and olfactory nerves arising from it ; B, nasal septum ;
C, palate-bone ; D, frontal bone.
found covered by papillae, some of which are long and slender
(filiform), and others are shaped like a puff-bull fungus
(fungiform). At the side of some of the fungiform papillae,
and of all the circumvallate papillae, the cells are modified
to form taste-buds. These consist of small cavities contain-
ing a cluster of cells, which are of two kinds — the gustatory
and supporting cells. The gustatory cells have small hairy
processes which project above the opening of the taste-
bud, and are exposed to the juices in the mouth.
Four qualities are detected by the sense of taste —
250
HYGIENE
namely, sweet, bitter, acid, and salt. We detect the
flavours of food and drink by the sense of smell. The
sensations are carried to the brain from the anterior two-
thirds of the tongue by the lingual nerve, a branch of the
fifth cranial nerve, and from the posterior third by the
glosso-pharyngeal or ninth cranial nerve.
Peripheral Sensations. — These are made up of cutaneous
FIG. 107. — CELLS OF
THE OLFACTORY Mu-
cous MEMBRANE.
Fio. 108. — ANATOMY OF THE
TONOTJE.
A, Epiglottis ; D, pharyngeal
portion of tongue ; C, oral
or buccal portion of tongue
covered by papillae ; D, D,
circumvallate papillae.
sensations — namely, touch, heat, cold, and pain, and also
the deep sensations arising from muscles and joints.
Touch is a skin sensation, and is elicited by stimulation
of nerve plexuses around hair follicles or some special form
of tactile corpuscle.
Heat sensation is experienced by stimulation of certain
specific end organs in the skin.
THE SENSES AND THE NERVOUS SYSTEM 251
FIG. 109. — MICROSCOPIC STRTTCTTTOE OF THE MTTCOTTS MEMBRANE OP
THE TONGUE.
A, Stratified epithelium ; B, taste-buds ; G, corium.
Fio. 110.— DIAGRAMMATIC REPRESENTATION OF TASTE-BTOS.
A, Stratified epithelium forming its wall ; B, gustatory or taste cells •
C, supporting or sustentacular cells.
252 HYGIENE
Cold is also elicited by stimulation of other special end
organs in the skin.
Temperature is a compound sensation, a combination of
touch and either heat or cold.
Pain is due to stimulation of the free nerve endings of
the skin.
Muscular and Joint Sense. — Afferent nerve fibres from
the muscles, tendons, and Joints, convey nerve impulses
which give rise to the sense of position and of the move-
ments of various parts of the body.
By muscular sensation combined with touch we deter-
mine the size and shape of objects.
The powers to localize touch in various parts of the
body, and to determine the size, consistence, and weight,
of an object, are acquired by practice in childhood — hence
the naturally eager desire of all young children to touch
and handle whatever they see.
CHAPTER IX
SANITATION OF THE SCHOOL
Relationship of Soil and Health. — Sanitary authorities
have for a long time held that the health of the inhabi-
tants of a locality bears a close relationship to the nature
of the soil of that locality, and this is still more marked
in the case of a single house or building.
It is seen, therefore, that it is of the greatest importance,
before building any house or school, to know the exact
nature of the soil of the site where it is to be erected. Let
us further consider the relationship of the character of the
soil to disease. Bowditch in America and Buchanan in
this country have brought certain facts to prove that there
is an ultimate connection between the moisture in the soil
and consumption of the lungs. Pettenkofer in Germany
has shown that there is a relation between the height of
the water in the soil and epidemic outbreaks of typhoid
fever. Malaria is most prevalent in the moist, hot climate
of the tropics ; it is very probable that with better drainage
the prevalence of this disease in such districts will be greatly
diminished. Some writers in this country state that too
much moisture in the soil and air of a building is closely
associated with conditions of catarrh, rheumatism, neural-
gia, etc., in its inhabitants.
It is wonderful what bacteriology and sanitary science
have done towards the extinction of yellow fever in America.
The two factors in t&e soil that influence the health of
the people living upon it are the composition of the air
253
254 HYGIENE
that lies in -the interstices between the particles of soil,
and also the amount of moisture that it contains.
Surface and Subsoil. — The soil is subdivided into the
superficial surface soil and the deeper subsoil. The
surface soil is made up of organic and inorganic con-
stituents ; it contains a large number of bacteria, some of
which are able to cause certain diseases in man, such as the
tetanus bacillus, causing lockjaw, or typhoid bacillus,
causing enteric fever. Others are of the greatest utility
to all forms of animal life, because they bring about the
putrefaction of organic materials containing nitrogen and
convert them to nitrates, which can be absorbed by plants,
and built up again to complex nitrogenous compounds,
which are eaten by man or animals. Since most plants
are not able to absorb nitrogen directly from the air, these
bacteria play a most important part in the " circulation
of nitrogen " in the animal and vegetable kingdoms. The
deeper subsoil is made of particles which are derived from
the rocks below, and it is thus made up of only inorganic
material. It will vary in composition in different localities
according to the nature of the rock that lies beneath such
localities.
The interstices between the particles of the upper layers
of the soil are occupied by air, and this is called the ground
air, and its composition is of great importance in its in-
fluence upon the health of the inhabitants living on the
soil. It may contain some organic constituents from the
decay of animal and vegetable substances ; further, it
contains more moisture, more carbon dioxide, and less
oxygen, than the atmospheric air.
The interstices between the particles of the deeper
layer of the soil are occupied by water, and this is called
the ground water. This is formed by rain water per-
colating through the upper layers of the soil until it reaches
an impervious stratum on the surface of which it flows
towards the nearest river or sea. The rate at which the
ground water flows away depends upon the condition of
SANITATION OF THE SCHOOL 255
natural drainage, and if this be inefficient it can be greatly
accelerated by artificial drainage.
The line of separation between the ground air and water
does not always remain at the same level. Thus, after a
heavy rainfall the level of ground water is raised, while
after a drought the level will be lowered. These will
cause corresponding movements in the ground air. Other
factors which cause movement of the ground air are the
difference in temperature between it and the atmospheric
air, changes in barometric pressure, and the action of the
wind.
Some soils readily allow water to percolate through, and
are said to be porous — e.g., sand, gravel, sandstone, and
chalk. Other soils do not allow the passage of water through
them, and are said to be impervious — e.g., clay.
Site of the School. — From the above facts it is seen
that the two important conditions that must be determined
regarding the soil as to its value as a building site are the
composition of the ground air and the amount of moisture
present.
The constituents of the ground air that must be avoided
are the volatile organic compounds which are formed by
decomposition of animal and vegetable matter. The amount
of such compounds in the ground air will naturally be pro-
portional to the amount of animal and vegetable matter
in the surface soil ; thus, it is found that excavations made
for various purposes are often filled up by all kinds of
rubbish. This results in what is called a made soil ; it
will contain large quantities of organic substances in
varying stages of decomposition, causing great pollution
of the ground air. Great care should be taken to avoid
such sites, or, if that is impossible, they should not be built
upon for at least eight or ten years after the excavation
has been completely levelled. The amount of moisture
in the soil will depend on its permeability and power of
absorption of water, level of ground water, and the con-
dition of natural drainage.
256 HYGIENE
A healthy site is one in which the soil is porous, or
impervious and non-absorptive, contains little organic
matter, where the ground water is 10 feet or more below
the surface, and where there is a good slope to allow for
natural drainage. Judged from these standpoints, we find
that rock, chalk and sandstone of considerable depth are
dry and healthy, while clay and made soils are very un-
healthy.
Environment of the School. — In this country, north and
north-eastern aspects are cold, whilst southern are warm ;
north-western and south-western are exposed to boisterous
winds, and the latter generally to driving rains. The
southerly aspect is generally dry and mild, and should, if
possible, be always selected.
The school should be some distance from all other
buildings, and especially from any offensive works, such as
tanneries, chemical works, etc. It should also stand at a
good distance from the street, to avoid noise and dust.
Trees should not be planted too near the school, because
they tend to prevent the evaporation of water, and also
impede the free circulation of air. At the proper distance
they are of great value to protect the building from cold
winds.
General Plan of School Buildings. — The considerations
requisite for proper hygienic conditions are so simple that
they are frequently overlooked even in elaborately-con-
structed modern schools. It is essential that a constant
supply of fresh air and daylight be obtainable, and in
addition some hours of direct sunlight. The exact re-
quirements of a school will depend, of course, upon the
number of scholars. The plan of a school required to
accommodate only fifty children will differ greatly from
that required to accommodate four hundred. It is desirable,
however, that all schools should be planned to meet the
above-mentioned general requirements, and such buildings
can be classified into two groups: (1) The central hall
type, where the classrooms open into the assembly hall ;
SANITATION OF THE SCHOOL 257
(2) pavilion type, where the classrooms open into a corridor
or veranda, and are independent of the assembly hall.
The central hall type of school appears at first sight
eminently satisfactory. It is convenient and compact,
and tends to render supervision easy. It has, however, its
disadvantages from a hygienic point of view. In this type
of school the assembly hall is surrounded by classrooms,
and the ventilation of the classrooms and this room are
therefore far from satisfactory. This is especially the case
during the hot summer weather, because the assembly
hall derives its ventilation from the surrounding classrooms,
and does not receive a constant supply of fresh air from
outside. The second hygienic essential, an abundant
amount of daylight, can easily be arranged for in this type
of school by the provision of a sufficiently large number
of windows. A serious difficulty is, however, experienced
when a direct supply of sunlight to each classroom has to
be arranged for. The importance of direct sunlight in all
classrooms cannot be over-estimated, because, as it will be
pointed out later, sunlight is one of the best germicides, and
schools should be so constructed as to allow of the presence
of sunlight for some time during school hours. The in-
convenience caused by excessive heat in summer can be
avoided by the use of blinds and curtains.
The pavilion type of school satisfies all the essential
hygienic conditions mentioned above. Each classroom
has an abundant supply of fresh air from the corridor or
veranda, the lighting of the rooms is satisfactory, and the
excessive heat of summer and the severe cold of the winter
can be moderated by a judicious use of the windows. The
chief objection to this type of school is that it covers a large
area of ground, which is a great drawback in large towns,
where the price of land is high.
The pavilion type has been most ably advocated in this
country by Dr. Reid, the Medical Officer of Health for
Staffordshire. (See his Report to the Staffordshire County
Council Education Committee, 1908.)
17
SANITATION OF THE SCHOOL
259
260
HYGIENE
The Construction of School Buildings. — First of all
adequate foundations must be secured. It is advisible to
have concrete foundations, grouted over by cement ; this
prevents the entrance of ground air and moisture. After
the removal of the surface soil, until a layer of hard earth
is exposed throughout the site of the school, it is covered
B
\
•^r--^^S^^[ 1 ,
•SfoSF5r=
Fio. 113. — DIAGRAM SHOWING THE FOUNDATION AND WALL OF A
BUILDING, AND THE MEANS PROVIDED TO PREVENT THE ASCENT
OF DAMPNESS WITHIN THE WALL.
A, Concrete foundation ; B, outside soil ; 0, damp-proof course ; D, floor ;
E, wall.
by a layer of cement concrete, 6 inches in thickness, and
under the walls the concrete must be at least 20 inches
deep.
The walls built of ordinary bricks and mortar are very
porous and capable of absorbing large quantities of water.
SANITATION OF THE SCHOOL 261
In the construction of the walls of a building, some pre-
cautions are taken to prevent the moisture ascending within
the walls. Where there is no basement, and the floors
are above the ground level, this result can be attained by
placing a damp-proof course of slates embedded in cement,
a half inch layer of asphalt, or slabs of perforated glazed
stoneware, in the walls. This should be placed at least
6 inches above the ground outside and below the level of
the lowest timbers. The stoneware slabs serve a second
function, in that the perforations allow the passage of air
through the walls, and thus ventilate the space under the
floor.
In buildings where a basement is necessary or in which
the floors lie at a lower level than the »oil outside, some
other means must be taken to prevent the ascent of moisture
in the walls. One method is called the " dry area," in
which a second wall is built at a short distance outside the
main wall ; it serves to keep the damp soil away from the
main wall of the building.
The external walls should be made of stone or good
bricks, bonded and solidly put together by means of mortar
or cement. The width will be proportional to the height.
The Board of Education demands that for walls of one
story high the thickness must be one and a half bricks,
and if of stone 20 inches thick. Hollow walls must be
built in very exposed situations.
Glazed bricks or enamelled tiles are very impervious
and readily cleaned, and therefore are very satisfactory as
internal wall surfaces.
If the walls are plastered, it should be a durable, smooth,
and non*porous variety, and it should be painted and var-
nished. The surface will then be almost non-absorbent,
and can be readily cleaned.
Great precautions should be taken so as to make the roofs
water-tight, and protective against heat and cold. Slates
and tiles are the best materials. Adequate means must
be attained to carry off the water from the roof as quickly
262
HYGIENE
as possible, and the spouting must be such as to be able
to cope with the maximum rainfall on any day in the year.
Floors should be made of wood blocks, and these laid
on cement and concrete (see Fig. 115). If boarded floors
and joists are used, the joists should be placed side by
side, and the floor boarding nailed to the upper surface of
the joists.
In order to abolish crevices, and thus facilitate sweeping
FlO. 114.— DIAGRAM SHOWING FOUNDATIONS AND WALL OF A BuiLt)-
INO WITH A DRY AREA INSTALLED TO PREVENT THE ACCESS or
WATER FROM THE OUTSIDE SOIL.
A, Concrete foundation ; B, dry area ; G, G, damp-proof sources ;
D, soil ; F, floor.
and cleaning, the wainscot and floor must be Joined by a
rounded insertion.
A basement should be present under the whole building.
Under certain conditions it may be used for cloakrooms.
Rooms situated in the basement should never be used for
SANITATION OF THE SCHOOL 263
teaching purposes. It may be taken up by the heating
apparatus and storerooms. The floor should be cemented
concrete.
The staircases should be made of some fire-resisting
material, such as iron and slate or steel and lead. It is
safer to have no balustrade, and to have the stairs walled
on both sides, because children often fall over the banisters.
There should be at least two staircases in every school,
and in mixed schools one should be used by the boys, and
another by the girls. The staircases should be about 6 feet
wide, and must not have more than fifteen steps to each
flight.
No school should have less than two entrances, and in
mixed schools there should be separate entrances for boys
©TELEl-
. BEAM
FIG. 115. — PLAN OP CONSTRUCTION OF FLOORS THAT SHOULD BE
ADOPTED FOR SCHOOLS.
and girls. In all schools the number of external doors
should be such as to allow the school to be completely
emptied in two or three minutes, if any emergency should
arise.
Cloakrooms and lavatories are essential for all school
buildings, and special rooms must be set apart for such
purposes.
Cloakrooms should be very well lighted and ventilated.
The pegs for hats and coats should be numbered, and
placed about 18 inches from each other. It is very impor-
tant to have free circulation of air around the clothing,
and therefore insuring rapid drying.
264 HYGIENE
Water-Supply. — Water is an absolute necessity to main-
tain life, and the supply should be pure and liberal. A
scanty and insufficient water-supply or scanty use of
available water results in every form of sickness associated
with filth, whilst an impure supply will result in various
forms of diseases.
To no class of the community is a plentiful water-
supply so essential as to the children in the schools, and
therefore it is the duty of the authorities to see that there
is an efficient water-supply to all the schools of the land.
The schools in all urban districts should obtain the water
from the general supply, but in rural districts is it generally
necessary to arrange for their own water-supply either by
smking a well or obtaining some means of collection and
storage of rain water.
The water from springs and wells varies greatly in
composition. Superficial wells are apt to contain organic
matter from cesspools and drains, but by an improved
subsoil drainage the water from these wells may be rendered
pure and wholesome ; therefore, if the water-supply of a
school comes from a shallow well or spring, there should
be no suspicion of pollution with drains or cesspools. These
wells should be examined after the holidays, and all the
water should be pumped out of them just before the open-
ing of the school. Since shallow wells are so liable to
pollution, it is better for country schools to have a private
deep or " Artesian " well. Deep wells contain much lime,
but they are the best source of drinking water. An
" Artesian " — from Artois in France — is a deep well bored
through impervious strata to a water stratum in which
the water is under such a pressure as to cause it to rise to
the surface. It is often better to filter the water before
it is drunk ; this should be done by a Pasteur-Chamberland
filter.
In the majority of towns the supply of water is main-
tained at a pressure which enables it to be drawn off
in houses at all times ; yet it is necessary to store some in
SANITATION OF THE SCHOOL 265
cisterns to feed boilers or for other emergencies. In some
places, however, water is only supplied at stated intervals,
and then a storage becomes a necessity. Thus there are two
systems of water-supply — the constant and intermittent.
In their report on the storage of water in houses the
Rivers Pollution Commissioners say : " All storage of
drinking water in houses is attended with the risk of
pollution. Good water is spoiled and bad water rendered
worse by the intermittent system of supply. All drinking
water ought to be drawn direct from the main. Under
proper supervision the waste of water is less on the constant
than it is on the intermittent system of supply. These
and other advantages have led to the adoption of the con-
stant system in a great majority of British towns." From
above it is seen how important it is to have a constant
supply of water whenever possible.
If the supply is intermittent, some form of storage is
absolutely necessary, and this is generally done by means
of cisterns ; they should be made of galvanized iron or
slate with cemented joints. All cisterns should be kept
covered to prevent contamination, but free ventilation
should be provided. They should be so placed as not to
damage the school or render it damp in case of leakage,
and also be easy of access for inspection, cleaning, etc.
The waste should open into the open air, and should on no
account communicate with the drains or closet tap. All
the cisterns should be inspected and cleaned periodically.
Where there is a public water-supply, the best means of
distribution is to have a drinking-fountain in the play-
ground. The best authorities advocate the instalment of
a fountain so constructed that a small stream of water
issues from an upright pipe for about 3 or 4 inches, and the
scholar drinks by receiving the stream into his mouth.
Drinking-cups should not be used, because they are often
potent factors in the spreading of contagious disease.
Various Forms of Water Pollution. — Shallow wells re-
ceive their pollution from the surface soil, and from the
266 HYGIENE
leaking of drains and cesspools. In order to prevent these,
the well must be sunk in such a position as regards possible
sources of pollution that the underground water flows
from the well to the sources of pollution. The mouth of
the well should be protected by a coping carried up to
about a foot above the surface of the ground ; it should be
closed over, and the water raised by an iron pump. The
water supplied by deep wells is generally remarkably free
from organic impurities, even when sunk in the midst of
large cities; but every means should be taken to prrvmt
contamination from surface drainage and from soakage
from sewers or cesspools.
School Drainage. — " The general aim in connection with
the drainage of a building is to insure a prompt and com-
plete removal of all waste, deleterious matter, the retention
of which may prove injurious to health. This is effected
by means of suitably-arranged pipes or drains, which shall
convey the waste water from baths, lavatories, etc., and
the removal of this and the construction of the pipes must
be such that, whilst they permit water to flow away into
the sewers, they shall not allow the access back again of
any gases produced by decomposition, from the drains
or sewers themselves into the building " (Hope and
Buchanan).
The principles that guide the constructions of drains for
schools does not differ from those applied in the cam Of
other residential or public buildings.
The exact course of the drains should be carefully
planned.
The trenches should be dug a s straight as possible, and
covered with concrete 6 inches in thickness, and should be
so graduated as to give a gradient of 1 in 40 for 4 inch
drains or 1 in 60 in 6 inch drams. Stoneware pipes should
be used, and laid with the socket end pointing towards the
commencement of the drain . Stoneware pipes are better than
those of earthenware because they are less porous and more
durable. Iron pipes may also be used. It is important
SANITATION OF THE SCHOOL
267
268 HYGIENE
to avoid the passage of a drain under the basement of a
house or school; and if this is impossible, greater care
should be taken with the joints, and the whole pipe should
be covered with concrete, and the wall supported by a
relieving arch to prevent settlement and fracture of the
pipes at the point where the drain leaves the premises.
The drains should be laid as straight as possible, and
stoneware pipes should be jointed by Portland cement,
and cast-iron pipes well caulked with blue lead. Care
should be taken to prevent any possible leakage, and also
the projection of any of the cement at the site of the Joint
into the interior of the drain, so as to obstruct the flow
of its contents. If a bend is necessary, it should be accom-
plished by a special pipe curved to the required degree.
Whenever a branch drain joins the main drain, it should
be done by means of a V junction pipe ; in such a case
there will be very little obstruction at the site of junction, be-
cause both currents are flowing very nearly in the same direc-
tion. All the branch drains should join the main drain as
near together as possible, and around such junctions a small
inspection chamber be built. In addition, any change in
direction of the dram should take place inside the inspec-
tion chamber. By having a system of such chambers, and
the drains between them running in straight lines, inspec-
tion of the drain is simplified and obstruction or deposits
can be readily removed. The inspection chambers should
be so constructed as to allow ample room for workmen
to manipulate rods and other cleaning apparatus. In the
case of iron drainage, it is usual to fix at the bottom of
these chambers a cast-iron box with the cover screwed
down ; with earthenware drains the bottom of the inspec-
tion chamber is laid with half-round glazed channel, and
the concrete benched, so as to prevent any lodgment of
excretory or foul matter remaining at the bottom of the
chamber after a flood or partial stoppage. A person entering
this chamber can say whether there is any obstruction at
the junctions, and, further, the chamber itself can be
SANITATION OF THE SCHOOL 269
easily cleaned and rods can be passed up the different
branches.
After the drains have been jointed they should then be
tested, and this can be done in several ways. One method
is to plug all the openings of the inspection chamber, and
then separately fill each branch of the drain with water.
If the water remains at the same level for an hour and a
half or two hours, the drains may be considered as satis-
factory. Another test is the smoke test, where a smoke
rocket is placed inside the dram, and inspection made for
any leakage of the smoke through the drain. Another test
is to break small capsules of phosphorus and asaf cetida in-
side the drain, and then look for any leakage of white fumes
formed by the reaction of these two chemicals. If a leakage
is present it should be remedied at once. Precautions
must also be taken to prevent the entry of gases from the
common sewer, soil pipes, drains, or waste pipes, to the house
or school. The most effectual means of prevention is to
have good ventilation of all the drains. Certain forms of
traps are of some use in this direction, but they are never so
effectual as good ventilation. Good ventilation can only be
effected when there is an outlet for foul air at one end of the
system, and an inlet for fresh air at the other end. The
grating over the inspection chamber acts as the inlet, while
the soil pipe or a separate ventilating pipe acts as the outlet.
Traps are simply means to prevent the passage of sewer
gas into the building. Siphon traps are the best, because
they can be readily flushed, and they have no corners
where any deposit can accumulate.
Cesspools. — These are, fortunately, not very commonly
used at present as means of collection for excreta ; but if
they are necessary, they should be removed as far as
possible from the school buildings, be made of brick,
and rendered water-tight by a good lining of cement.
Closet Accommodation. — It is of the greatest importance
that efficient sanitary conveniences should be installed in
all the elementary schools. There are two systems used
270 HYGIENE
to dispose of human excreta — conservancy and water-
carriage systems.
Conservancy System. — This should only be installed in
rural districts where there is no water-supply. All towns
which have an efficient water-supply should install a water-
carriage system. It is very undesirable to have any
form of conservancy system, because excremental matter
is kept near the school, and does not conduce to good
hygienic conditions.
Closets under this system may be of three kinds — privy
or midden, pail, and earth closets.
Privy or Midden Closets. — In this form of closet, a hole
is dug in the earth and a seat erected above it ; the hole
acts as a receptacle for the faeces. In the older forms of
midden closets, no provision was made to prevent their
contents mixing with the soil around, polluting the water
of the neighbouring wells and the air around the building.
The Local Government Board have formulated certain
laws which define requirements in the construction of a
privy. It must be at least 6 feet away from any dwelling,
and 40 or 50 feet from any well, spring, or stream. Ven-
tilating openings must be provided near the roof, which
must be rainproof. This method is very inefficient, and
should not be used in any form for schools.
Pail System. — The excreta in this system are received
into pails or tubs, which are removed very frequently and
their contents thrown away. The pails or tubs are then
replaced by clean ones. The contents should be kept as
dry as possible, because in this way certain decompositions
resulting in noxious gases are prevented. The contents
of the pail should be mixed with sawdust, soot, or other
absorbent material, or the pails may contain crude
aluminium chloride or cupric sulphate. In agricultural
districts the contents, after mixture with ashes, can be
used as manure. In the larger towns where this system
is used, the pail contents are converted into dry manure
by the action of vitriol and ashes.
SANITATION OF THE SCHOOL
271
: 5ECTTOM
:-THB»«?
: EARTH CLOSET
.DOOR.
Earth Closets. — These are modifications of the pail
system where there is an automatic arrangement for
covering each stool with about 1 or 2 pounds of dry
earth. The bacteria of the earth convert the nitrogenous
substances in the faeces to nitrates, and thus render them
inoffensive. Dried garden soils, peaty soils, or clay soils,
should be used for this purpose. The pail contents may be
used as manure, or they may be exposed to the air, dried,
and used again. This may be repeated five or six times.
None of the above forms
of closets should be placed
in the school buildings ;
they should be placed at
the farther end of the
playground. A servant
should be employed to
see that they are kept in
good and sanitary condi-
tion.
Water- Carriage System.
— This method should be
employed for disposing of refuse in all cases where there
is an efficient water-supply.
Water Closets. — These are contrivances for the reception
of excreta and for their carriage away by a stream of water.
In one set of water closets the contrivance for retaining
the water in the basin is not movable, while in the other
set there is a movable contrivance for the retention of
the water in the basin — e.g., movable pan, plug, or
valve.
Since all forms of pan, valve or plug water closets are
unsatisfactory, they should never be installed in the schools.
Some form of water closet with an immovable arrange
ment for the retention of the water in the basin should be
used, such as the hopper closet.
The pedestal form of wash-down water closet with a
flushing rim is the best form for schools and dwellings.
FIG. 117. — DIAGRAM SHOWING THE
CONSTRUCTION OF AN EARTH
CLOSET.
272
HYGIENE
s^F
Short Hopper or Wash-Down Closet. — This consists of
an inverted stoneware cone, with a Lp- shaped pipe
attached to it below. This acts as a trap by retaining
enough water to prevent the access of air from the sewer
to the rooms. The cone is about
8 or 9 inches in length. In order
to prevent the excrement dropping
on the sides of the basin, it is
important to have the posterior
wall of the cone nearly vertical.
-! r\_f I* should also be provided with a
'df>I/ " flushing rim," and thus the sides
of the basin will be well cleaned.
Trough Closet. — This is a com-
mon form of water closet used in
schools. It is an open trough
made of stoneware, and inclined
towards the outlet. Its length will
vary according to the number of compartments required.
At the lower end or outlet there is a high siphon trap, which
causes the retention of enough water to cover the bottom
TVPC.
: A 3HOIST
: HOPPER
Fio. 118. — DIAGRAM SHOW-
ING CONSTRUCTION OF A
SHORT HOPPER CLOSET.
7
y
3E.CTIOM
TRAR
FIG. 119. — DIAGRAM SHOWING THE CONSTRUCTION OF A TROUGH
CLOSET.
of the trough. At the other end an automatic flush tank
is placed about 5 or 6 feet above the trough ; this should
be arranged to discharge every few hours. Trough
closets do not work very satisfactorily, and have therefore
SANITATION OF THE SCHOOL 273
been replaced in the more modern schools by separate
wash-down closets.
The walls of the closets should be made throughout of
glazed bricks, and all corners should be rounded off. The
floors should be made of brick set in cement, and should
have a good slope towards the door. This will insure
rapid drying after being flushed with water, a procedure
that should take place daily. Each closet apartment
should have a fixed open grating near the ceiling, and a
fresh-air inlet near the floor level. Each water closet
pan should, wherever possible, be fixed to an outside
wall.
Urinals. — Urinals in a large number of schools are,
unfortunately, kept in an insanitary and offensive condi-
tion. There is no excuse for it at all, especially in places
where there is an abundant water-supply. All the surfaces
with which the urine comes in contact should be smooth
and non-absorbent, and should therefore be made of slate
or glazed earthenware. There should also be an arrange-
ment for a flushing with water of all the surfaces with
which the urine comes in contact ; this is generally done
by having a trough full of water, which fills and empties
automatically. In districts where there is no water-
supply, an attendant should wash the urinals twice or
three times daily by pouring bucketfuls of water over them.
Lavatories. — A large number of authorities have not yet
realized that good lavatory accommodation is absolutely
necessary for all schools. One lavatory basin should be
provided for every ten scholars. The basin should be
made of hard and durable material, and possibly the best
outlet is an opening fitted with a movable plug.
There should be no direct connection between the waste
pipe of the lavatories and any sewer or drain. If the
lavatory is on the ground- floor, the waste pipe should pass
through the outside wall and discharge upon a surface
sloping down to a gully trap ; but if the lavatory is on one
of the upper floors, the waste pipe should communicate
18
274 . HYGIENE
with a vertical pipe which discharges on a sloping surface
above a gully trap.
Baths. — It is very essential to provide swimming baths
and shower baths in the schools. In the past very little
has been done in this direction by most educational
authorities, but it is hoped that more will be done in the
future.
Effects of Sewer Gas. — Drain or sewer air often has a
bad effect upon the general health of persons who inhale
it. This is most marked when there is a leakage from
cesspools or drains into houses, and the occupants are
exposed to it for a long time. The long-continued inhala-
tion of diluted sewer air results in a chronic condition of
ill-health, and children are very susceptible to this con-
dition ; " it is characterized by the presence of anaemia,
loss of appetite, prostration, diarrhoea, fever, headache,
vomiting, or sore throat. It may be only present as a
condition of lowered vitality, and such persons would
have a very low resistance to any form of acute infection.
" There is a severe form of sore throat which attacks
the occupants of badly drained houses. It is marked by
swelling of the tonsils, very foul tongue, derangement of
the stomach, severe headache, and great depression."
In some persons sewer air poisoning is shown by the
presence of boils and carbuncles, enlarged glands, and
special form of skin rashes.
CHAPTER X
SANITATION OF THE SCHOOL— Continued
Ventilation. — Ventilation is of very great importance,
and very worthy of the attention that is paid to it by all
sanitary authorities. Of late too much stress has been
laid upon certain aspects of this question, while other very
important points have been entirely neglected. The in-
creased amount of carbonic acid and the exhalation
of hypothetical volatile poisonous compounds from the
lungs have received great attention, while the effects
of the stagnation of the air, its increased temperature,
and the rise in the percentage of water vapour, have
not had the amount of study which their importance
demands.
The atmosphere is a gaseous envelope which surrounds
this earth. It is a mechanical mixture of various gases,
but the one that is essential for the maintenance of life is
called " oxygen."
The chemical composition of ordinary air can be de-
termined by analysis, and is found to contain oxygen,
nitrogen, and carbon dioxide, and traces of other rare
The percentage composition is as follows :
Per Cent.
Oxygen 20-96
Nitrogen .. ... .. 79 '00
Carbon dioxide . . «,. 0'04
Water vapour .. .. variable
275
276 HYGIENE
Expired air contains the same gases, but differs in its
percentage composition from the ordinary atmospheric
air. Expired air has the following composition :
Per Cent.
Oxygen 16-40
Nitrogen 79-19
Carbon dioxide .. .. 4-41
Water vapour .. .. saturated
It is seen that the difference between inspired and ex-
pired air is that expired air contains less oxygen, more
carbon dioxide, and is saturated with water vapour.
When a person enters a crowded room, he will generally
remark it feels stuffy and the atmosphere is impure. Now
let us inquire into the conditions which bring this about,
because it is only by a correct idea of their causation that
we shall be able to apply rational means of prevention.
The volume of air space for each person is too small, and
therefore the volume of air that is available for each person
in a room is a very important factor to determine. We
have seen about the difference between inspired and ex-
pired air ; the process of breathing by the occupants of a
room results in a gradual decrease in the amount of oxygen
and an increase in the amount of carbon dioxide. This
can go on to a certain point without having any bad
effects ; if it is allowed to go on until the percentage of
carbon dioxide rises up to about 2 to 3 per cent., then
breathing would become ratfher deeper, but the symptoms
presented would not be anything like so serious as those
that are described by a large number of writers on this
question. The air of the room would practically be at a
standstill, its temperature would be raised, and the per-
centage of water vapour would be greatly increased. More
modern research on ventilation tends to prove that these
last-mentioned factors are the most potent in bringing about
the condition of discomfort in crowded rooms. They have
their deleterious effects by preventing the loss of body heat.
The resultant product of the chemical cHanges that are
SANITATION OF THE SCHOOL 277
going on in the body is heat, and this is lost from the body
by the various physical methods by which anything that
is heated will lose its heat. Any condition that will un-
duly inhibit the loss of body heat will decrease the rate of
the chemical changes going on in the body and the amount
of available energy ; hence mental and physical vigour
will be diminished, and result in lassitude, which is the
commonest condition of persons in ill- ventilated rooms.
Personal emanations are very largely responsible for
the unpleasant odours which are perceptible on passing
from the outer air into a crowded unventilated room, and
this is particularly the case if the persons are of uncleanly
habits. These can to a great extent be obviated by
personal cleanliness ; great care should be taken to keep
the skin of the whole body clean, and this can only be done
by frequent bathing, and it is also of great importance to
have clean clothes, and underclothing.
To summarize, we have found that the air in" a crowded
ill- ventilated room differs from ordinary air in the following
points :
1. Diminished amount of oxygen.
2. Increase in the amount of carbon dioxide.
3. A great increase in the amount of water vapour.
4. Temperature is higher.
5. Decomposition of organic matter on the skin and clothes, if the
persons are unclean, giving rise to offensive odours.
6. Certain other gaseous impurities may be present due to the com-
bustion of coal and coal gas, carbon monoxide, and the oxides of
sulphur.
Having learnt the nature of the changes undergone by
air in a crowded room, it is easy to lay down principles on
which methods of prevention would depend. In order to
keep the percentage of oxygen and carbon dioxide at the
right level, there should be a sufficient cubic capacity for
each occupant, and the air should be continually renewed,
so that each person gets a sufficient volume of fresh air in
a certain interval of time.
Dr. Newsholme, of the Local Government Board, says
278 HYGIENE
that for each scholar there should be 150 cubic feet of space,
15 square feet of floor space, and 1,500 to 1,800 cubic feet
of fresh air per hour.
The continual renewal of the air, which is attained by
some form of ventilation, will not only tend to keep the
percentage of oxygen and carbon dioxide at the right level,
but will also obviate all the other changes enumerated
above ; stagnation of the air, rise in temperature, and
increase in the amount of water vapour, will be prevented.
Methods of Ventilation. — The problem of ventilation of
many school classrooms is rendered a very difficult one
from the circumstance that a series of rooms considerably
overcrowded may be occupied almost continuously for as
long as three hours. In some of the older schools the
question of ventilation was not studied at all, while, un-
fortunately, in more modern schools conditions are often
not much better, though large sums of money are spent on
elaborate installation.
There are two methods of ventilation — namely, the
natural and artificial. By natural ventilation is meant any
method that depends on the natural forces that cause
movement of the air, and does not necessitate the applica-
tion of any mechanical appliance for its renewal. In
artificial ventilation, on the other hand, the air is renewed
by means of fans, pumps, or bellows.
Natural Ventilation. — In this method of ventilation there
are three causes at work — diffusion of gases, the change
in density of the air caused by heat, and the force of the
wind.
1. Diffusion is a property of both liquids and gases, by
which their molecules are able to mix thoroughly even
against gravity.
This phenomenon can readily be shown by taking a jar
containing air and a drop or two of bromine placed in it.
The coloured bromine vapour will be seen to rise up, even
against gravity, until the colour of the contents of the
cylinder is everywhere of the same depth.
SANITATION OF THE SCHOOL 279
It can, also be seen when two jars are used, one contain-
ing air and the other carbon dioxide. If the carbon
dioxide be placed in the lower jar, it will pass up to the
upper until the contents of both jars will have a uniform
composition. The presence of carbon dioxide can be
proved by the addition of lime-water, when a white pre-
cipitate of calcium carbonate will be formed. The rate of
diffusion of a gas is inversely proportional to its density,
so that the lighter a gas is the faster it diffuses ; if a light
gas is on one side of a porous partition, and a heavier gas
on the other, then the light gas will diffuse through into
the heavy one faster than the heavy gas will diffuse into
the lighter one. In a room the ah* inside has a higher
temperature and is lighter than the cold air outside, and
therefore diffusion outwards of the lighter air will take
place at a greater rate than diffusion inwards. This will
result in a difference of pressure between that exerted by
the air inside and outside the room, and thus fresh air will
enter the room not only by diffusion, but also to equalize
this difference of pressure.
Some authorities state that the air of a room of 3,000
cubic feet will be completely changed in one hour pro-
vided there is a difference of 35° F. between the tempera-
ture of the air inside and outside.
2. Changes in Density of the Air. — When air is heated
it expands and becomes lighter in weight ; it will therefore
rise up, and cold air will take its place. Winds are produced
in this way, by the unequal heating of the air over dif-
ferent parts of the earth's surface.
3. Force of the Wind. — Winds are powerful ventilating
agents, and act in two ways : (a) by perflation — i.e., setting
masses of air in motion and driving them onward by
propulsion ; (6) by aspiration. When wind passes over
chimneys or a tube placed at right angles to its course,
it causes a diminution in pressure within them, and thus
creates a current of air up the chimney, and fresh air
must be drawn into the room below to take its place.
280 HYGIENE
The aspirating action of the wind is constantly being used
to ventilate rooms by means of the chimney ; this is in-
creased when there is a fire burning. If the chimney is
lower than the surrounding structures, the wind striking
these, and then descending, will often cause a back draught
and smoky chimney.
Different Forms of Openings used in a Natural System of
Ventilation. — In a natural system of ventilation the
openings are so arranged as to admit the air from outside
just above the level of the heads of the occupants of the
room. To avoid a draught, various contrivances are used
to direct the current of air upwards : it then mixes well
with the air of the room, and is warmed thereby, before it
falls down and reaches the occupants of the room. The
impure air is warm, and therefore its density is lowered ;
it will rise up towards the ceiling, where means of exit
should be provided.
A large number of different contrivances are used in
a natural system of ventilation, and they may be broadly
divided into inlets and outlets. The inlets, as said above,
are placed rather low down, while the outlets are placed
at the top of the building.
Inlets — 1. Windows and their Modifications. - The
simplest method of natural ventilation is by means of open
windows. The efficiency of such methods will depend upon
the type of school building. Dr. Reid of Stafford has
proved that in the pavilion type of school building ex-
cellent results can be obtained by cross window ventilation.
A common modification of window ventilation is that
of Hincke-Bird, where a solid block of wood is placed
under the whole length of the lower sash frame of a
window, and hence the upper rail of the lower sash is
raised above the lower rail of the upper sash. Air can
enter from outside between the two sashes, and is directed
upwards by the upper part of the lower sash.
2. Chaddock's Windows are often installed in schools and
colleges, and give very good results. The upper smaller
SANITATION OF THE SCHOOL
281
portion of the window can be opened by a hopper arrange-
ment. The lower portion may be in one piece, and open
by rotation round a pivot, or, better, it is divided by a
central mullion, and each half opens on hinges.
3. Tobin's Tubes. — These are very common forms of
inlets used in schools and public buildings. An opening
u
13 0
FIG. 120. — DIAGRAM SHOWING
HINCKE - BIRD'S MODIFICATION
OF WINDOW VENTILATION.
FIG. 121.— TOBIN'S TUBE.
is made in the outer Avail just above the floor level, and is
guarded by a perforated plate ; this is connected with a
vertical tube, which ascends up 6 feet above the floor
level. The upper opening of the tube is guarded by a
valve by means of which the air entry can be regulated.
282
HYGIENE
4. Sherringham Valve. — This is another common inlet
ventilator. A special form of perforated plate is placed
Fio. 122. — SHERRINGHAM VALVE.
in the wall about 7 feet above the floor, and on the inner
side of this plate there is a hopper valve and side-checks.
Air enters through the perfora- . >
tions, and is directed upwards ->~ "^
by the inclination of the valve.
5. Ellison's Bricks.— These
are special forms of bricks pro-
Fio. 123. — DIAGRAM SHOWING A SEC-
TION THROUGH ELLISON'S BRICK.
FIG. 124. — DIAGRAM SHOWING PER-
FLATING ACTION OF THE WlND.
vided with a conical perforation; the apex is directed
outwards, and the base inwards. As the air enters, the
cross -section of its path is increased ; hence its velocity is
diminished, and thus draughts are prevented.
SANITATION OF THE SCHOOL
283
Outlets — 1. Chimney. — This is the most important outlet
for foul air. The ascent of such air in the chimney is
brought about by the decrease in its density, because it is
warmed and the aspirating action of the wind produces
a partial vacuum.
2. Arnotfs and Boyle's Valves. — These are metallic
frameworks supporting small talc or mica plates, which
Fia. 125.— MACKINNELL'S VENTILATOR.
guard small openings that communicate with the chimney
flue near the ceiling.
3. MacKinnelVs Ventilator. — This can only be applied
to a room which has no other apartment over it. It
consists of two concentric tubes ; the inner tube forms
an outlet, and the space between the two tubes forms an
inlet.
284 HYGIENE
Artificial Ventilation. — There are two methods of arti-
ficial ventilation :
1. Extraction or Vacuum Method. — Mechanical appli-
ances are installed to withdraw the impure air from the
room. In order to keep the pressure inside constant, fresh
air from outside is drawn in through certain special openings.
2. Propulsion or Plenum Method. — Here the appliances
mechanically force fresh air into the room, and the impure
air is thereby forced out through special openings that are
installed.
Extraction or Vacuum Method. — It consists in connecting
the apartment to be ventilated, by means of tubes, with a
ventilating shaft.
A strong updraught is obtained in the ventilation shaft
by having some means of heating the air within it. It
may be heated by a fire in a small furnace below, hot-
water pipes or steam, or lighted gas-jets at the bottom of
the shaft.
Another method to obtain a strong updraught is to have
a fan fixed near the top of the vertical shaft ; this generally
works very satisfactorily.
Buchanan and Hope mention the following objections
to this method of ventilation : (1) " The inequality of the
draught, due to difficulty of always maintaining the fire
at the proper height ; (2) the inequality of the movement
of the air in the several rooms of a building, those nearest
the shafts being more rapidly exhausted than those at a
greater distance ; (3) regurgitation of smoke from the
shaft into the room ; (4) difficulty in controlling the supply
of fresh air at a proper temperature."
Propulsion or Plenum Method. — This method consists
in forcing air into the room by means of fans, and further
arrangements are made to regulate the volume and
physical condition of the air.
The volume of air propelled into the classroom will
depend on the rate of rotation of the fan ; the greater the
rate, the greater the volume, and vice versa.
SANITATION OF THE SCHOOL 285
The air is generally heated by passing it over steam
coils placed at the bottom of each shaft. The tempera-
ture of the air will therefore depend upon the time that
it has been in contact with the steam coils ; if the rate
of propulsion is increased, the time during which the air
remains in contact with the coils is diminished, and there-
fore it is not so well heated, and the reverse is the case
when the rate of propulsion is diminished ; therefore by
varying the rate at which the air is forced into the room
the temperature of the room can be regulated.
It is of the greatest importance to have the air at the
right degree of humidity, and this is well proved by the
more modern work on ventilation. In the American
schools the air that is propelled into the classrooms is
often too dry, and has very deleterious results on the
respiratory system ; on the other hand, too much moisture
has an equally bad effect, and thus it is very desirable
to have some means of regulating the amount of moisture
in the air. This is generally arranged for by having a
stream of water passing over the screen, through which
the air is filtered, or steam jets are placed in connection
with the steam coils used to heat the air.
The air can be filtered from dust particles and soot by
passing it over screens made of coke or jute.
Combination of Propulsion and Extraction. — This method
of artificial ventilation is called the balance system, and
is specially applicable for the ventilation of large halls.
Dr. Ralph Crawley has pointed out the following ad-
vantages and disadvantages of an artificial system of
ventilation in elementary schools.
The system has the following advantages :
1. The amount of air supplied can be carefully regulated.
2. The source of the air can be effectively controlled either near the
ground or, by means of a shaft or small tower, from a good height above
the ground.
3. The mechanical impurities can be filtered off.
4. The temperature and moisture of the air can be regulated with
great accuracy.
286 HYGIENE
It has the following disadvantages :
1. It is expensive, not only to fit it up, but for its continual working.
2. Uneven distribution of the current of air in the room ; also there
is often an accumulation of foul air near the outlet.
3. The presence of closed windows is a bad training for the children.
4. The physical condition of the air is so altered as to result in a lack
of freshness.
During the past, natural ventilation has been condemned
as inefficient by most authorities ; this is most likely due
to the fact that little trouble has been taken to plan the
school and fit appliances suitable for natural ventilation ;
on the other hand, when a school is to be ventilated by
artificial means, very careful calculations are taken, and
the whole system is carefully planned. Dr. Reid has proved
that excellent results may be obtained by natural ventila-
tion in the Staffordshire or pavilion type of school building.
Warming. — There is great variation in the susceptibility
of different individuals to grades of heat and cold, and
this depends upon the age, constitution, and usual mode
of life. The temperature of a sitting-room or schoolroom
should be about 60° F. to 65° F. Since the heat regulatory
mechanisms in the child are not so well developed as in
the adult, it is very important that great care should be
taken to apply adequate heating apparatus in the school.
The heating of the school is closely associated with its
ventilation, and has been discussed indirwtly in the section
on ventilation.
It has been previously stated (p. 176) that heat tends
to pass from warm bodies to the colder surrounding
structures by three processes — namely, conduction, con-
vection, and radiation.
The following methods are used for heating school
buildings :
1. Open Fires. — Houses are generally heated in this
country by means of open fires, but such a method can
only be applicable to small schools.
The back and sides of the grate should be made of fire-
SANITATION OF THE SCHOOL 287
clay, and the back should slope forwards, so that the
flames play upon it ; by such means the loss of heat through
the chimney is diminished, because some of it will be
reflected to the room by the sloping surface with which
it comes in contact. In order to have better distribution
of the heat, it is advisable to have the grates as low as
possible, and brought forward into the room.
Open fires are very cheerful, and, as has been said above,
they are important factors in aiding ventilation, but a
large amount of heat is lost by being carried up the
chimney; further, they require frequent stoking and
cleaning, and create a large amount of dust and ashes.
Ventilating grates may be combined with the fireplaces.
These are made by building small chambers around the
back and sides of the fireplaces, and should extend up to
and surround the lower portion of the chimney flue. Fresh
air enters this chamber by openings provided in its posterior
wall ; it is heated inside the chamber, expands, and enters
the room through openings provided just above or below
the mantelpiece. The Galton grate is built on this principle.
2. Stoves. — There is a great variety of heating stoves,
and they are classified as either closed or ventilating stoves.
In the former class no provision is made to take advantage
of the stove as a ventilating agent ; whilst in the latter
fresh air from outside the room circulates through the
stove, and thus the stove acts as a good ventilating
mechanism .
They have certain advantages over open fires: the
amount of heat that is lost is smaller ; they are cleaner,
and provide a more uniform supply of heat ; and if of good
quality they require very little attention. On the other
hand, they do not aid ventilation as well as open fires, and
if made of cast iron they may give off carbon monoxide,
which is a highly poisonous gas.
3. Hot-Water Pipes. — This is a method that has been
applied to heat large rooms, halls, etc., where open fires
and stoves have been inadequate. It is a well-known
288 HYGIENE
physical fact that the boiling-point of water and all liquids
depends upon the pressure under which they are heated.
Under normal atmospheric pressure water boils at 100° C.
or 212° F. ; if the pressure to which it is exposed is in-
creased, the boiling-point will be raised ; thus, under a
pressure of four or five atmospheres the boiling-point of
water would be 300° F. On the other hand, if the pressure
is diminished the boiling-point will be lowered ; thus, at
the top of high mountains the boiling-point of water is
so lowered that it will be useless for cooking purposes,
unless special contrivances are taken to increase the
pressure under which the water boils. In the heating of
rooms by hot-water pipes two methods have been applied
— one, where the water is heated at atmospheric pressure,
and certain arrangements are made to allow for its ex-
pansion. This is called the low pressure system ; the
other, where the water is heated under an increased
pressure, is called the high pressure system.
In the low pressure system 3 or 4 inch cast-iron pipes
are connected with a boiler placed in the basement, in such
a manner as to allow for a complete circulation of the
water inside. The exit pipes are attached to the top of the
boiler, while the return pipes reach it at the bottom. The
water on being heated expands, its density is diminished,
it circulates through the pipes, parting with some of its
heat to the air in contact with them, and on cooling
returns to the boiler ; the circulation depends on the
difference in specific gravities of the water in the flow and
return pipes. At the highest part of the system an ex-
pansion tank is placed, so as to allow for increased volume
of the water on being heated, and to make good any leak-
age or waste from evaporation th« tank is supplied with
water from the water-supply by means of a ball- Valve.
There are some modifications of this system used, such
as circulating pipes of smaller diameter, and radiators are
placed at convenient points. In Barker's "cable" system
there i4 a mechanism placed to assist the circulation.
SANITATION OF THE SCHOOL 289
Wrought-iron pipes of small diameter are used in the
high pressure system. The water is heated by about a
sixth of the piping being coiled and placed inside a brick
furnace at the basement. The pipe is completely filled
with water, and from the top of the coil in the furnace
it passes vertically, ard goes round each room in turn,
and then returns to the bottom of the coil. The water
is heated to about 300° I'., and, to prevent overheating
and too great a pressure, an expansion tank is connected
to the highest point of the system.
With this system there is a great tendency for the air
to become overheated and too dry, and thus become
" stuffy " in character.
Ventilating heat radiators give very good results where
there is a mechanism by which air can be drawn from the
outside and pass over the heating surface, and through a
grating placed at the top of the radiator into the room.
The Temperature and Humidity of the Air of Schools.—
All schoolrooms should be supplied with two or three
reliable thermometers, placed at different points in the
room. The temperature should not be allowed to rise
above 60° F. or to fall below 48° F. at any time.
When discussing the question of regulation of body heat,
it was said that the evaporation of sweat was one of the
most important ways in which the body lost its super-
fluous heat. Naturally, the rate of evaporation from the
skin will depend upon the degree of saturation with water
vapour of the air surrounding it. If the air is moist and
nearly saturated, the body cannot lose its body heat at
a proper rate, the skin becomes hot and moist and its
bloodvessels dilated, and therefore not so much blood is
carried to the brain ; this results in mental and bodily
langour. On the other hand, when the air is too dry it
is likely to have a bad effect on the respiratory system
of the children, because they will be exposed to such
differences in degree of moisture in the school air, the
outside air, and the air of their homes.
19
290
HYGIENE
no—
100 —
90 90 —
80 80—
70
70—
The amount of moisture contained in the air depends
on the temperature. The warmer the air, the greater is
the amount of water vapour that it can hold, and vice
versa; so that if you raise the temperature of a certain
volume of air saturated with
moisture, it will no longer
remain saturated, because
it will be able to take up
more water vapour. On the
other hand, if the tempera-
ture is lowered it becomes
incapable of holding so much
water, and some of it is de-
posited as dew.
Dry and Wet Hygrometer.
— This is an instrument to
determine the relative
amount of moisture present
in the atmosphere. It con-
sists simply of two ordinary
thermometers placed side by
side on a frame. The bulb
of one of the thermometers is
covered by muslin, which is
kept moist by a piece of lamp
wick which dips into a small
vessel containing water.
The wet bulb thermometer
legisters a lower tempera-
-60 60—
•so so —
•10 40 —
30 30 —
20
-10
ao —
•o —
FIG. 126.— DRY AND WET BULB
THERMOMETER.
ture than the dry one ; this
is due to the cooling result-
ing from the evaporation of
the water. If the air is dry, evaporation takes place
more rapidly, and therefore the temperature of the wet
bulb will be lowered, and there will be a good difference
between the readings of the two thermometers ; on the
other hand, if the air is moist evaporation would be slight,
SANITATION OF THE SCHOOL 291
and result in a small difference in the temperature of the
two thermometers. The dry bulb temperature should be
between 56° and 60° F., and the wet bulb temperature
between 53° and 56° F.
Lighting. — An adequate and proper supply of light is of
the greatest importance in our schools. A large number of
authorities maintain that some eye conditions found amongst
the children of our elementary schools are directly due to
deficient and improper illumination of the schoolrooms.
It must also be remembered that sunlight is one of the
best germicides, and some of the bacteria that cause
disease in man are killed when exposed to sunlight for a
short time. The areas of the windows must not be calcu-
lated by that necessary on a sunny day or when the sky
is clear, but by that necessary on dull days during the
winter months ; and, secondly, it is the illumination of
the portion of the room that is farthest away from such
windows that must be considered.
The windows should be arranged so as to admit light
from the left side of the scholars, and provided the light
comes from this direction it is impossible to make too
much allowance for its entry ; but as a minimum the
window glass must not be less than one- fifth the area of
the floor. The windows should be made of white glass,
extend up as far as possible and as close into the corners
as possible, and wide partitions between the panes of glass
must be avoided, because they cast troublesome shadows.
Light should not come from the front of the scholar ; and
if it comes from the back, a shadow is cast over the work
of the scholars and it is troublesome for the teacher.
A large number of our school buildings are so built
that they are surrounded by neighbouring walls and
houses. Under such conditions it is necessary to deflect
the light into the room by ribbed glass or prisms.
The best form of artificial light is the incandescent
electric lamp. If gas illumination is used, suitable in-
candescent burners and shades must be applied.
292 HYGIENE
< — ln the past, not enough attention has been given
to the desk accommodation in our elementary schools,
but it is hoped that in the future, with the advent of
the medical officer to the schools, this question will be
more satisfactorily solved. It is obvious that desks ought
to be graduated according to the size of the scholars, but
this has not been appreciated even by the Board of Educa-
tion, whose rules state that the desks should be graduated
according to the ages of the children.
The best position in which a child can be seated is such
that the body be equally balanced and symmetrical ; such
a posture will require the least effort to keep the body
in stable equilibrium. Such a posture is attained when
the child sits with the two ischial tuberosities on the same
H
Fia. 127. — DIAGRAM SHOWING THE RELATIVE PosmoH o» DESK AND
SEAT IN VARIOUS FORMS OF DESKS.
A, Minus desk ; B, zero desk ; G, plus desk.
horizontal plane, the thiglis horizontal, the feet resting
flat on the floor, back well supported, and the body erect,
with vertical line from the centre of gravity bisecting the
line joining the two ischial tuberosities.
In order to attain such an ideal, it is obvious that there
must be some adjustment of the desks and seats to the
size of the scholars who work at them. This can more or
less be easily done in schools where each class has its
own classroom. On the other hand, in schools where a
special room is allotted to each subject, and not to each
class, this question becomes very difficult, and the only
thing that can be done is to arrange the seats and desks
in rows, those for the smaller pupils being in front, and
those for the tallest behind, the other rows being arranged
SANITATION OF THE SCHOOL
293
for the intermediate heights ; and each class, when using
the classroom, should sort itself according to the size of the
individual pupil.
Let us consider the adjustment of seat and desk for each
individual pupil. The height of the seat is obtained by
bending the knee at right angles, placing the foot flat on
FIG. 128. — PUPIL SEATED IN A " PLUS " DESK.
the ground, and measuring the distance from the floor to
the under-surface of the thigh ; the back must be curved
forwards and high enough to support the lower parts of
the shoulder-blades ; the seat should be hollowed out to a
depth of | inch, and the concavity should extend to within
2 inches of the front edge.
In the adjustment of the desk, the " difference " — i.e.,
294 HYGIENE
the vertical distance from the edge of the desk to the level
of the seat — must be such that the edge of the desk be
brought opposite the navel of the child.
Desks are classed into three groups, according to the
relation of a vertical line drawn from the posterior edge of
the desk to the anterior edge of the seat.
FIG. 129.— PUPIL SEATED IN A " MINUS" DESK.
A " plus " desk is one in which the vertical line from
the posterior edge of the desk falls in front of the anterior
edge of the seat.
A "zero" desk is one in which the vertical line from
the posterior border of the desk touches the anterior edge
of the seat.
A " minus " desk is where the vertical line from the
posterior edge of the desk passes through the seat.
SANITATION OF THE SCHOOL 295
" minus " forms, although the commonest desk in our
schools at present is the " plus " form. The " plus " desk
should never be used, because it results in the body being
bent forwards, and causes the lungs, heart, and abdominal
viscera, to be unduly pressed upon ; and the vertical line
from the centre of gravity does not fall through the line
joining the ischial tuberosities, therefore the body is not
in stable equilibrium unless muscular effort is brought to
balance it.
It is seen that the entirely separate desks are the best,
and each desk and seat should be adjusted for each pupil
The teacher must also realize that in the past children
have been made to sit at the desks for too long a period ;
it is criminal to allow a child to sit in any form of a
desk for three hours at a time. Sitting-down periods
should be limited to three-quarters of an hour, relieved by
intervals of lessons in the standing postuie or an interval
of play.
Blackboards. — The best form for schools is the slate
blackboard, and it should be placed around all the avail-
able walls of the classroom. Children can be sent in groups
to the blackboard to do some of their lessons ; this will
obviate too much fatigue arising from sitting at the desks.
Damp dusters should always be used to clean the boards ;
this lessens the amount of chalk dust floating in the air.
Hygiene of Infants' Department. — The first question that
arises with regard to the infants' department is — At what
age should children be first admitted to the schools ?
Unless some other provision is made for the education of
the child, the Board of Education demands its attendance
at school at the age of five, provided its physical condition
will permit it. On the other hand, there are many
children under the age of five attending our elementary
schools. The propriety of such rule and custom will de-
pend upon the relative sanitary and moral condition of the
home and schools.
296 HYGIENE
If the home is such as to provide adequately for the
proper physical and moral training of the infant, it is
better for the child not to attend school until the age of
seven ; but it must be remembered that such ideal homes
are not, unfortunately, possessed by the majority of the
children attending the elementary schools of this country ;
hence, under the present conditions, some provision must
be made for children of five, or even three, years of age.
It will be advisable for us to consider the most obvious
dangers to the physical and mental conditions of such
children by their attendance at schools. Firstly, all the
cells of the body are young and delicate ; hence every pre-
caution must be taken to allow for the proper development
and prevention of overfatigue of the body, because any
damage done during this stage is very difficult to remedy.
Suitable and adequate nourishment, abundant supply of
fresh air, and ample opportunity for rest and exercise, must
be provided. Secondly, the fatality from infectious dis-
eases— e.g., measles, whooping-cough, diphtheria, etc. —
is greatest at this peiiod of life. This danger may be over-
come by preventing overcrowding, allowing ample space
for each child, adequate facilities for good ventilation
combined with efficient medical inspection ; under such
conditions the risk of infection will, in the majority of
cases, be less at school than at home.
If the children are not provided at home with sufficient
nourishment, it is the duty of the local authorities to
supply them with adequate and suitable food.
The floor space per child must be greater than in the
higher schools, and the greatest care should be taken to
provide for an adequate supply of fresh air and sunlight.
Heavy desks and galleries should never be used, but
small tables and chairs should be used instead, as they
can be easily put on one side to make more room for games
and play.
An adequate playground should be provided, and be
partly covered, so that the infants can be taken out often
SANITATION OF THE SCHOOL 297
to play, even on rainy days. The curriculum must be
based on knowledge of the physiological development of
the child.
Lessons involving fine muscular co-ordination or mental
concentration — e.g., writing, needlework, and reading —
must be banished, and instead large objects and course
movements must be the instruments of education. Correct
physical habits must be taught. When discussing the
growth of the child's nervous system, we mentioned how
co-ordinated contraction of muscles is developed by the
opening up of new nervous tracts, and hence the importance
of walking, running and marching exercises in the infants'
curriculum.
Open-Air Schools.* — Modern educational legislation and
administration are characterized by their efforts to adapt
the curriculum and surroundings of a child to its physical
and mental capacities. It is illustrated in the many Acts
that have passed making special provisions for different
groups of school-children. One such group is that com-
prising children who suffer from various physical defects,
resulting in their not being able to profit to a satisfactory
extent by the ordinary school methods. Some of these
children have no definite illness, but they are debilitated,
and not up to the standard of efficiency ; others suffer from
definite physical conditions, such as enlarged glands,
adenoids, anaemia, malnutrition, tuberculosis, in various
forms of bones, joints, and glands, nervous disorders, or
ear discharge. Mental backwardness is closely associated
with the physical defect, and is caused by it in the majority
of cases. Such children require good feeding, the best
hygienic surroundings, and open-air life ; the problem has
been satisfactorily solved in the establishment of open-air
schools.
The first open-air school was established in 1904, at
edited by T. N. Kelynack, M.D. (publishers, King and Son).
298 HYGIENE
Charlottenburg in Germany. Rough sheds and school
barracks were erected in a pine-wood at the outskirts of
the town. In three months' time the physical defects were
either cured or improved, and there was also great im-
provement in the mental and moral condition of the
children.
In 1906 the first English open-air school was opened by
the London County Council in Bostall Wood, Woolwich.
The great success of this school led to the establishment in
1908 of three other similar schools in London, and subse-
quently schools of this type for debilitated children have
been established in Sheffield, Bradford, Halifax, and
.Norwich.
The site of such schools should be well in the country,
and still within easy walking distance of the tramway
terminus or other means of conveyance.
The soil should be pervious, and the water-supply
should be ample and good.
An excellent type of building is that of the Bradford
open-air school, which has six classrooms, each with a
teaching veranda, together with dining and resting sheds.
A corridor connects the various buildings, behind which arc
placed the baths, kitchen, lavatories, etc.
The children come to the school about 8 a.m., and de-
part for home about 7 p.m. They are given three meals
— breakfast, dinner, and tea.
It must be remembered that the children are at the
school because of their physical condition, and therefore
much elasticity must be allowed with regard to the school
curriculum, which should be as practical as possible ; thus,
geography may be taught by the construction of relief
maps in sand or earth, arithmetic by measuring actual
distances or the circumference of trees by tape measure.
Nature study should form a very prominent part in the
curriculum. Arrangements should be made for singing
and breathing exercises, and all work should be done in
the open air, except in stormy weather, when the sheds
SANITATION OF THE SCHOOL 299
should be used. Very adequate periods of rest and play
must be provided for.
The results have been most encouraging. Dr. Ralph
Crawley in the Bradford schools found great improvement
in the physical appearance and carriaga of the children,
increased weight, increase in the amount of haemoglobin,
and great improvement in the physical condition of the
chest.
CHAPTER XI
DISABILITIES AND DISEASES OF CHILDREN
The Relation of Micro-Organisms to Disease. — Bacteria
is the name given to a group of organisms which lie lowest
in the scale of vegetable and animal life. The bacteria
consist of minute unicellular masses of protoplasm devoid
of chlorophyll, which multiply by simple fission. Some
are motile and others non-motile. They measure in certain
diameters only ^y^ of an inch.
The great characteristic of most vegetable organisms is
that they are able, by means of the green pigment called
" chlorophyll," to obtain their food from the water and
salts of the earth, and the carbon dioxide present in the
air. They are able to absorb carbon dioxide from the air
through their leaves, break it up, liberate oxgyen, and
combine the carbon with hydrogen and oxygen of the
water, which they absorb by their roots, together with
various salts dissolved in the water. This building up of
complex organic compounds — sugar, starch, fat, protein —
practically from their elements, only takes place in the
presence of this green pigment (chlorophyll). The re-
sultant compound is used as foodstuff by the plant itself.
When the plant utilizes these foodstuffs to maintain its
life, the process is similar to what takes place in animals :
there is absorption of oxygen and the elimination of carbon
dioxide.
It is seen, therefore, that in plant life there may be two
forms of gaseous exhanges. The first one is similar to what
takes place in animals. In order to utilize its foodstuffs
300
DISABILITIES AND DISEASES OF CHILDREN 301
to maintain its life, the plant absorbs oxygen, and as a
resultant product of various chemical reactions carbon
dioxide is evolved and eliminated. The second form of
gaseous exchange is peculiar to plants, which have chloro-
phyll, and can only take place in the presence of sunlight.
Here there is absorption of carbon dioxide and the elimina-
tion of oxygen.
The great difference between animal and vegetable life
is that animals are not capable of forming their foodstuffs
FIG. 130. — DIAGRAM SHOWING THE FORM OF SOME BACTERIA.
(a), Tubercle bacillus ; (6), anthrax bacillus ; (c), tetanus bacillus ;
(d), streptococci, or pus-forming bacilli.
from their elements, while plants are, in the majority of
cases, able to build up their foodstuffs from their elements.
Animal life is maintained by making use of food that has
been already prepared by plants.
Some plants do not contain chlorophyll, and are therefore
unable to form their foodstuffs ; these plants must live
like animals — that is, by obtaining their nourishment from
either dead or living organic substances. Such plants are
called " fungi," and the lowest group of fungi are called
" bacteria."
302 HYGIENE
Those bacteria which live on dead organic matter are
called " saprophytes," while those which are able to attack
living tissues, and obtain their nourishment in that way,
are called " parasites." The great majority of bacteria
which produce disease in man are parasites.
The realization of the existence and growth of these
organisms within the human body has brought about the
greatest revolution in medicine and surgery that these
sciences have experienced. How do these organisms pro
duce disease in man ? The bacteria, being unable to form
their foodstuffs as most other plants, must obtain it from
either dead or living organic material, and in the production
of disease in man these organisms gain entrance to the tissues
of the human body, and obtain their nourishment from them.
These organisms may produce a disease simply by their
presence in the body. Their metabolic products are toxic,
and cause a reaction in the tissues around them — an " in-
flammation " as it is called. The bloodvessels are dilated,
more blood is carried to the part, it becomes red, swollen,
hot to touch, and painful.
The toxins secreted by the bacteria are very similar in
nature to ferments, cause great injury to the tissues around,
and give rise to very active inflammation. This is exemplified
in the case of the bacteria which give rise to diphtheria.
These organisms generally attack the throat, and they
secrete a poisonous substance, diphtheria toxin, which is
absorbed by the blood-stream and carried to all the tissues
of the body, giving rise to the signs and symptoms of
diphtheria. Other forms of bacteria may enter the blood-
stream and cause a general microbio infection — that is,
the organisms are not confined to the site of invasion, but
are carried to all the tissues, and exercise their deleterious
influence throughout the whole body ; such is the case
with typhoid bacilli or the organisms which give rise to
general blood-poisoning, or septicaemia. These produce the
diseased condition by their presence throughout the body ;
they abstract their nourishment from the tissues, and pour
DISABILITIES AND DISEASES OF CHILDREN 303
out the products of their metabolism, which are poisonous,
to the body.
Conditions of their Life. — There are five factors which
must be considered in the maintenance and growth of
bacteria — namely, food - supply, moisture, relation to
gaseous environment, temperature, and light .
Food-Supply. — Bacteria, like animals, must have as their food already
synthesized organic compounds. They live on either dead or living
organic material.
Moisture. — The presence of water is necessary for the continued
growth of all bacteria. The amount of drying which bacteria will
. resist varies very much in different species. Thus, the organism which
causes cholera is killed by two or three hours' drying, while the diphtheria
bacilli will resist drying for several days.
Relation to Gaseous Environment. — The effect of the oxygen of the air
on bacteria is of great importance. Some bacteria prefer to live in an
atmosphere containing oxygen, and are called aerobes ; others thrive
better in the absence of oxygen, and are called " anaerobes." For ex*
ample, the germ which causes lockjaw will thrive better in the absence
of oxygen, while most germs which cause disease in man live better
in the presence of oxygen.
Temperature. — For every form of bacterium there is a temperature
at which it grows best. This is called the " optimum temperature."
The optimum temperature of the organisms which thrive in the human
body is the temperature of the body. The growth of organisms is in-
hibited by cold, but they are killed by excessive heat. Boiling in water
will kill practically all bacteria.
Effect of Light. — Direct sunlight is one of the most powerful factors
in killing bacteria ; it is therefore of great importance to have plenty of
sunlight to all the schoolrooms, for in this way the germs are destroyed.
Means of Resistance. — Every part of the human body
that communicates with the outside air is in contact with
a large number of micro-organisms, which, if they gained
entrance in sufficient numbers to the tissues, would set
up a diseased condition of those tissues. It is only by
certain means that the body is able to hold this invading
army in check. How does the body protect itself from
being overpowered by these micro-organisms ? The struc-
ture of the surface layer hinders their entrance ; when a
section of the skin is studied microscopically, it is seen to
304 HYGIENE
be made up of a thick layer of cells, which are very closely
aggregated together, so that in the normal state it is
impossible for bacteria to gain entrance through the skin
in sufficient numbers to cause any damage to the tissues.
If there is an abrasion or cut in the skin, and it be left un-
protected, organisms readily gain entrance, and may set up
variable degrees of inflammation. The discharges from
the surfaces of the body have protective functions. Thus,
if saliva were to be absent from the mouth, the growth of
bacteria in it would be far more luxuriant. It is well
known that the gastric juice and bile retard the growth,
or even destroy, various forms of bacteria. Some authori-
ties maintain that mucus has bactericidal properties, and
this substance is formed by the cells which line the surface
of the respiratory and alimentary tracts. The ciliated cells
which line the respiratory tract drive the dust and germs
entangled in the mucus into the pharynx, where the
mucus is swallowed. Hence tho expired air contains no
germs. In coughing, speaking, and sneezing, droplets
of saliva are sprayed out by the explosive force of the air-
blast. By these droplets, colds, measles, etc, are spread
Passing out, in between the cells which line the surfaces
of the respiratory and alimentary tracts, there will be found
some phagocytic cells. These have the power of sending
out processes of their protoplasm, which surround the
bacteria and destroy them.
Another means of defence is the lymphatic system.
Within the tissue spaces there is lymph, and this contains
white blood-corpuscles, and very close to various possible
sites of entrance of bacteria we find groups of lymphatic
glands, and these, as is well known, act as scavengers of
the body. For instance, at the entrance of the pharynx
we find the tonsils ; deep to the mucous membrane of the
stomach and intestines there are nodules of lymphatic
tissue ; in close relationship wit h the trachea and bronchi
are a number of lymphatic glands.
Some authorities maintain that the endothelial cells
DISABILITIES AND DISEASES OF CHILDREN 305
oi bloodvessels (see structure of bloodvessels) have bacteri-
cidal properties.
The circulatory fluids of the body have very important
protective functions. When studying the composition of
blood, it was said to have red and white corpuscles ; the
great function of the white corpuscles was to get rid of any
noxious substances which gained entrance to the body,
and hence these are the most effectual means of killing the
bacteria after they have entered the body.
In the plasma of the blood there are substances which
act on these micro-organisms and make them palatable
to the leucocytes ; these substances are called "opsonins."
It has been said above that bacteria during their growth
in the body generate certain poisonous substances called
" toxins "; the tissue fluids are able to generate substances
called " antitoxins," which combine with the toxins and
render them innocuous. It is obvious that there -are a
large number of factors concerned in the protective
mechanisms of the body, and the only way to have these
in the optimum condition is to have the general health
at its best. This is only possible when a person has a
sufficient quantity of nourishing food and sleep, exercise
in the fresh air, and a reasonable amount of work and
amusement to keep him happy.
Relation of Seed (Bacteria) and Soil (Body Tissues). —
The susceptibility to the different microbic diseases varies
greatly in different children, and this difference in the
resisting power of individuals is very difficult to explain
in many cases.
Some persons are immuned to certain diseases, while
they are very susceptible to other infections. Further,
two different persons may be exposed to the same degree
of infection, and acquire the disease ; but the course taken
by the malady may differ greatly in the two individuals :
in one it may be severe and prolonged ; in the other it may
be mild and of short duration.
An attack of infectious disease renders the subject non-
20
306 HYGIENE
susceptible to that specific organism for a longer or shorter
period of time ; this is called " acquired immunity." In
the case of smallpox the period of non-susceptibility after
the attack is very long, and it is rarely that a person ever
becomes infected twice with that disease. With measles
and scarlet fever the immunity is not so permanent. It is
clear, therefore, that, in the causation and severity of disease,
not only has the virulence of the organisms to be taken into
account, but also the susceptibility of the person that is
exposed to infection.
The susceptibility of children to infectious diseases will
vary inversely as their general health condition and
hygienic surroundings.
Conditions disposing to Disease.— All conditions which
lower the vitality of a child predispose it to disease.
Some of the conditions may be enumerated as follows :
1. Congenital Abnormalities — e.g., children with congenital heart lesions
are very susceptible to any form of infection.
2. Injudicious or Deficient Food. — During infancy, those children
which aro artificially fed are more liable to die than those which are
fed on the breast.
Older children, when improperly and insufficiently fed, are very liable
to any form of infection — e.g., consumption. The body, not having
proper nourishment, is not able to generate a sufficient power of resist-
ance. Overfeeding leads to digestive troubles, and results, not in
greater strength, but in ill-nourishment and weakness.
3. Bad Ventilation and Overcrowding. — Fresh, cool, moving air is as
essential to proper maintenance of life as good food. When children are
forced to live in badly- ventilated and crowded rooms, their vitality will
certainly suffer, and make them very disposed to any form of infection.
4. Insufficient and Improper Clothing. — It is the experience of everyone
that a sudden change of cold, raw, moist weather is the immediate
predisposing cause of a large number of respiratory diseases, caused by
the entrance of micro-organisms to the body. For example, the bacteria
which cause pneumonia are present always in our mouths ; a sudden
change in the temperature will diminish the resistance to these organisms.
This explains how persons after a severe chill are so liable to contract
pneumonia.
If children are insufficiently or improperly clothed, the activities of
their bodies will certainly be deranged, and result in diminished re-
sistance to disease.
DISABILITIES AND DISEASES OF CHILDREN" 307
Overdo thing weakens all the defensive mechanisms, and is to be
avoided just as much as underclothing.
5. A great many infective diseases are spread by the bites of insects.
The insects carry the organisms of disease from the blood of one person
to another. This is the case in plague (flea), yellow fever and malaria
(mosquito), sleeping sickness (fly), etc. All parasitic biting insects
should be kept out of our houses and away from our persons, and all
manure-heaps, etc., which breed flies and mosquitoes, should be cleaned
up and done away with. Flies bring dirt and germs into our food.
EARLY SIGNS AND SYMPTOMS OF COMMON AILMENTS IN
CHILDREN.
Chorea, or St. Vitus's Dance. — This is a disease which
generally affects children, and is characterized by irregular,
non -repetitive, and involuntary contraction of the muscles,
a variable amount of psychical disturbance, and liability
to inflammation of the lining membrane of the heart. It
is most common between the ages of five and fifteen, and
the type of child who suffers from this disease is generally
very intelligent at his work, and is often overstrained by
the work that is given to him in schools.
There is no doubt that there is a close association between
chorea and rheumatism. The child will have suffered from
joint pains and sore throat in a large number of cases, and
there will be a history of rheumatism in his family.
In the mild form of chorea the affection of the muscles
is slight, the speech is not seriously disturbed, and the
general health not impaired ; the child will simply appear
clumsy and awkward, and there will be restlessness and
inability to sit still, conditions often termed " fidgets."
There are emotional disturbances, such as crying spells or
night terrors. A change in temperament may also be
noticed ; a docile, quiet child may become cross and
irritable. In the more severe forms there will be very
obvious signs. The characteristic involuntary movements
may be limited to the face, or one limb, or one side of the
body, or they may be general. If the face is affected, there
will be curious jerkings and twitchings of the muscles of
308 HYGIENE
the lips, cheeks, nose, and eyes. When asked to put
out his tongue, such a child usually jerks it out and in
again and snaps together the teeth. Speech is very often
affected.
When the limbs are affected they perform jerky, irregular,
purposeless movements. When the child is asked to pick
up a pin, a large number of irregular movements will be
made around the object before it is finally picked up.
All the movements of the disease are intensified by
excitement or by knowledge that anyone is watching.
During the whole course of this disease the child is
entirely unfit for school, and the disease lasts three or four
months. If a child shows any of the above symptoms and
signs, it should be sent to the school medical officer to
be examined, and he will advise appropriate treatment.
Nervous Disorders of Childhood. — All the nervous dis-
orders of childhood may be divided into two great groups-
functional and organic.
In the fiist group there are no anatomical changes in
the nervous system to account for the disorder ; it is a
question of deranged function. Such is very prevalent
in childhood, because the nervous system at this age is
unstable, the higher parts of the brain are yet imperfectly
developed, and therefore the lower ones are incompletely
controlled. There is also lack of co-ordination between
the different nerve centres, and this often results in inco-
ordination of function.
Two diseases — namely, rheumatism and rickets — are
very common in childhood, and these predispose children
to all forms of functional nervous disorders.
The signs of functional disorders of the nervous system
in children are so numerous and varied that it is impossible
to give an adequate description of them here. Such are
convulsions, habit spasms — e.g., blinking or sniffing — night
terrors, incontinence of urine, and various pseudo-paralyses.
The symptoms and signs of organic nervous disease will
vary according to the site of the lesion.
DISABILITIES AND DISEASES OF CHILDREN 309
If the higher parts of the brain are affected there will
be mental deficiency.
If the motor paths of the nervous system are affected
there will be paralysis.
If the sensory paths are affected there will be loss of
various sensations.
Overpressure. — This results from the evil methods of our
educational system, and also from the bad hygienic con-
ditions found in the homes of the children attending our
elementary schools.
Symptoms. — The child may become restless, excitable,
and even hysterical, or the conditions may be characterized
by lapses of memory, mental dulness, incapacity for con-
centration, and headaches.
Treatment. — 1. Better nutrition and more hygienic
surroundings at home.
2. More time must be spent in the open air, and the
periods of rest must be greater.
3. Less mental work, avoidance of all excitement.
Hysteria. — This is a term applied to a variety of
well-recognized symptoms, which appear to depend upon
abnormalities ot the irritability and conductivity of
nervous tissues. It is not commonly met during school
life.
Symptoms. — It is very difficult to give a satisfactory
classification of the symptoms, because they are so varied
and numerous. There may be mental irritability, depres-
sion, or exaltation. Paralysis of muscles and loss of sensa-
tion are commonly present. It may result in physical
and mental inefficiency or chronic invalidism. Patients
suffering from this condition often have hysterical attacks,
or fits. These are attended by laughing or crying, but
sometimes they are distinguished with difficulty from
ordinary epilepsy.
Epilepsy. — This is a disorder of the nervous system
characterized by loss of consciousness to a varying degree,
with or without convulsions.
310 HYGIENE
Causes. — Little is known definitely about the causation
of epilepsy. It is frequently met with amongst the children
of insane, hysterical, or alcoholic parents.
Symptoms. — These vary according to the degree of
severity of the disease, but there are two main forms —
namely, " petit mal " and " grand mal."
Petit Mal resembles a fainting attack, and is accom-
panied by pallor, dazed appearance, and momentary loss
of consciousness ; the child drops any object that he hap-
pens to be holding.
Grand Mal. — Previous to an attack the patient has a
warning of its onset. This may take the form of peculiar
sensations of sighc and hearing, or tingling of the limbs.
The child then gives a cry, and falls down. All the muscles
of the body become tense, the jaws are clenched, the whole
body is rigid, and the face becomes blue. The muscles then
become relaxed, and convulsive movements are set up.
The saliva pours out from the mouth — so-called " foaming
at the mouth.*' A fit will last from one to five minutes,
when the child falls asleep.
Treatment. — The only treatment necessary during th<>
attacks is to prevent the child injuring himself. He should
be laid on the floor in a clear space, and prevented from
biting his tongue by placing something between the teeth,
such as a handle of a toothbrush or pencil wrapped round
with a piece of cloth, such as a towel or handkerchief.
Such a patient should be sent to the medical officer for
investigation and treatment.
Headaches. — Headache is a very common complaint
amongst school-children. It is a symptom that arises
from various causes. Bad ventilation and overheating is
a frequent cause of this condition, and this origin should
be suspected by the teachers if several members of the class
complain, especially late in the day's work. Eyestrain is also
a common cause of headache. It will often be associated
with certain eye defects, and such children should be sent to
the medical officer to have their vision tested and treated.
DISABILITIES AND DISEASES OF CHILDREN 311
Another common cause of headache in children is dis-
turbance of the digestive tract, such as bad teeth, dis
ordered stomach, or constipation.
Children suffering from adenoids and enlarged tonsils are
very liable to catch a cold, and such catarrhal condition
of the mucous membrane of the throat and nose are fre-
quently associated with headache.
Some of the acute specific fevers, such as scarlet fever,
measles, etc., commence with a headache.
Children who are rickety or anaemic will often suffer from
headache, especially after mental or physical exertion.
INFECTIOUS DISEASES.
The term infectious disease is applied to any disease
caused by the growth of a living virus, known or unknown,
within the tissues of the body. Before giving an account
of the symptoms and signs of the infectious diseases com-
monly met with in schools, let us discuss in general how
the factors are produced, and the way in which the diseases
and their dissemination can be prevented. Each disease
is produced by a specific micro-organism. This has been
decidedly proved in the case of diphtheria, typhoid, influ-
enza, etc., because a germ with certain definite character-
istics can be isolated from persons suffering from such
disease. Further, the germ can be cultivated apart from
the body, and on injection into animals the germs produce
the same specific disease. On the other hand, the organisms
causing some of these diseases, such as smallpox, scarlet
fever, mumps, etc., have not yet been isolated ; but, by
analogy with the diseases mentioned above, we may cer-
tainly conclude that these latter diseases are also caused
by certain specific germs, but the means of observation
and technique at present at our disposal are not such as
to enable us to isolate and identify such germs.
The first factor in the causation of any of these diseases
is the carriage of the germs to a susceptible person. When
312 HYGIENE
the virus can only be transferred by contact, the disease
is said to be contagious ; but when the germ is conveyed
by air, the disease caused is said to be infectious. Having
reached the surface of the body, the germ cannot produce
disease unless it has a favourable channel of entrance to
the body ; e.g., typhoid bacilli can only be admitted to the
system by the alimentary canal, and tetanus bacilli require
an open wound to produce infection. It has been pointed
out previously that these germs thrive in the body. They
cause their deleterious effects by the production, by their
own metabolism, of poisonous substances which injure or
may even cause death of the tissues. The symptoms and
signs of these diseases are produced partly by the reaction
of the tissues of the body against such invasion, and als<>
by the direct poisonous effect of the germs upon the tissues.
When the bacteria first enter the body, they are not
numerous enough to produce instantly the symptoms and
signs of the disease ; but if the conditions are favouraM-
they grow and thrive, and when their number and poisonous
products have increased to a certain extent the character-
istics of the disease are displayed. The period that elapses
between the entrance of the virus and the first sign of the
disease is called the " incubation period." This varies with
different diseases, but for the same disease it is more or
less constant. The disease will end either in death or
recovery. Death will result because the amount of poison
produced in the body is such as to directly or indirectly
kill the nerve cells upon whose integrity the vital functions
of respiration and circulation depend. Recovery takes
place when the reaction of the body is such as to destroy the
germs and neutralize and eliminate their poisonous products.
Physiologists and bacteriologists have within recent years
carried out important researches upon the factors whi< h
defend tissues against invasion by bacteria, and the means
by which the body destroys such bacteria and neutralizes
their products. The factors depend to a large extent upon
the corpuscles and plasma of the blood, and it is marvellous
DISABILITIES AND DISEASES OF CHILDREN 313
what power of response to such invasions the blood pos-
sesses ; and the response is specific for each species of germs.
It has been previously pointed out that the white blood-
corpuscles are able to surround and destroy the bacteria,
and that there are present in the blood substances called
"opsonins," which prepare the bacteria for ingestion by the
white corpuscles. By the reaction of the tissues a substance
called " antitoxin " is produced, which neutralizes all the
poisonous effects caused by the germs. There are also
present in the blood-plasma substances called " comple-
ments," which are able to destroy any foreign cells intro-
duced into the body ; but this action is only possible when
a connecting material called " amboceptor " is produced.
The amboceptor connects the foreign cell to the comple-
ment, thereby causing the cell to be destroyed or rendered
innocuous. Recovery takes place when the above pro-
cesses are able to cope with the infection and its results.
The germs are killed and their toxins neutralized, and the
cells of the damaged tissues then grow and attain their
normal structure and function.
When recovery has taken place, there is left an over-
production of the means of such recovery ; consequently
there follows a period of non-susceptibility to that par-
ticular disease. In some cases, such as smallpox, it is
permanent ; in others, unfortunately, it is not so. A
person therefore is liable to only one attack of smallpox,
and it is not often that a person has more than one
attack of any of the specific infectious diseases. This con-
dition of non-susceptibility to a disease is called immunity,
and it may be natural or acquired. The degree of suscepti-
bility of a person to infection varies with his constitution,
age, and hygienic surroundings. Children are far more
liable than grown-up persons to contract measles, scarlet
fever, mumps, etc. Unhygienic conditions are most im-
portant factors in the production and spread of these
diseases. Acquired immunity may be active or passive.
The immunity after recovery from an infectious disease is
314 HYGIENE
an active acquired form, because the antitoxins have been
produced in the tissues themselves. Active acquired im-
munity can also be produced by repeated injections into a
person of dosages of the virus not sufficient to produce
disease. His tissues will react and produce antitoxins,
and his resistance to a particular disease will be greatly
increased. This is done in the case of tubercle and typhoid
fever. Passive immunity is attained when a serum con-
taining antitoxin is injected into the body. This principle
is applied in the treatment of diphtheria, and has been
accompanied with great success. Diphtheria bacilli are
injected into a horse. Its tissues form antitoxin, and from
its blood a substance is obtained which is injected into
human beings suffering from this disease. The results
have been excellent.
There are three conditions essential for the production
of an infectious disease : (1) Source of infection ; (2) sus-
ceptible person ; (3) means of carriage of the virus from
the source to a susceptible person.
1. Source of Infection. — The source of a great majority
of infectious diseases is another human being who has
recently suffered from such a disease, or who harbours the
germs without showing any signs of the dintanri
2. Susceptible Person. — It has been shown above how
susceptibility depends upon constitution, age, etc.
3. Means of Carriage of the Virus— (a) Air. — The bac-
teria causing smallpox, measles, and scarlet fever, arc un-
doubtedly carried by ah-.
(b) Human Beings. — They are often not only the source of
infection, but the means of its carriage to a susceptible person.
(c) Animals. — Flies carry the germs of typhoid, sleeping
sickness, and yellow fever. Mosquitoes spread malaria.
(d) Clothing, Books, etc.— Some germs cling for a con-
siderable time to these articles, which would therefore be
potent factors in the causation of an epidemic in schools.
(e) Water. — Typhoid, cholera, and other diseases, are
carried by water.
DISABILITIES AND DISEASES OF CHILDREN 315
MEANS FOR THE PREVENTION OF THE OCCURRENCE AND
SPREAD OF INFECTIOUS DISEASES IN SCHOOLS.
This question will be discussed from three standpoints :
(1) The duties of the teacher ; (2) the duties of the medical
officer ; (3) the duties of the local authorities.
1. Duties of the Teacher. — He should learn the elemen-
tary principles of physiology and hygiene, and should instil
such knowledge into the children, and at every opportunity
into their parents. If the children and parents acted
according to these principles, their general physique would
be improved, and their resistance to all forms of infectious
diseases increased. These principles should guide the
teacher in the classroom as regards adequate light, proper
ventilation, alternate periods of work and play, etc. He
should exercise his power of observation, and ought then
to be able to notice early signs of disease in the children,
who should be sent for treatment to the medical offioer.
It is of the utmost importance that the teacher should be
able to identify the early symptoms and signs of the
common infectious diseases ; consequently, when a chill
presents any of these signs, his condition is diagnosed early
and the spread of the infection curtailed.
2. Duties of the Medical Officer. — He should diagnose
these diseases early, take effectual means to isolate the
suffering, and hold in quarantine the persons who have
been closely associated with the child. The means of
isolation will depend upon the social condition of the
patient, nature of the disease, and means provided by the
sanitary authorities.
3. Duties of the Local Authorities. — Great care should be
taken in securing a proper site, plan and construction of
the schools. There should be an adequate supply of sun-
light, fresh air, and floor space per child. Every case of
infectious disease should be notified to the sanitary
316 HYGIENE
authorities, and the medical officer of health should trace,
as far as possible, the infection to its origin, and take
adequate means to abolish it.
If an epidemic breaks out in a school, they should
provide means of giving the children acquired immunity.
This is, up to the present, only of value in a few of these
diseases — e.g., vaccination for smallpox, antitoxin for
diphtheria, etc.
Isolation hospitals should be provided in every locality
for the treatment of infectious diseases.
Disinfection should be carried out in the rooms occupied
by the infected child ; it should also be done in the school
whenever a large number of children have been infected.
This is generally provided for by the local sanitary
authorities.
A short account will be given of the symptoms and signs
of the more common forms of infectious disease that attack
children at school age.
Measles. — This is a very common disease amongst
children ; and though the general publio does not attach
much importance to it, it is responsible for about 10,000
deaths annually in England and Wales. This heavy death-
rate is not due to measles in itself, but to pulmonary com-
plications, which occur when the patients do not have
appropriate care and attention, and live in bad hygienic
surroundings.
The incubation period of measles is about fourteen days.
The period of invasion— that is, the time the child is ill
before the appearance of the rash — lasts three to four days.
The child generally presents the signs of a feverish cold.
There will be sneezing and running at the nose, redness of
the eyes and lids, and cough. The skin will be dry and
hot, and the child will complain of headache. If during
an epidemic of measles a child should show any of the
above signs and symptoms, he should at once be sent home.
4* Whether measles is prevalent or not, a child in the infants'
department who shows suspicions symptoms should be sent
DISABILITIES AND DISEASES OF CHILDREN 317
home at once. If the teachers would adopt this course, most
epidemics of measles would be avoided."
In about four days after onset the rash characteristic of
measles comes out, and then the diagnosis will be certain.
Small red spots just like fleabites will appear first on the
forehead, and then on the rest of the face ; they then
become raised and form dark red patches. The rash then
spreads to the other parts of the body.
The child is infectious during the whole course of the
illness, which usually lasts about four weeks.
German Measles. — This is rather a mild infectious dis-
order, having symptoms and signs similar to those of
measles. The incubation period is about a fortnight.
The period of invasion is very short, generally about
twenty-four hours, and during this time there may be
chilliness, headache, pains in the back and legs, and coryza.
There may be very slight fever. All these symptoms are
generally very mild. The rash usually appears on the first
day, and is often the first symptom noticed. It comes out
first on the face, and then on the chest, and in twenty-four
hours it will have spread all over the body. The eruption
consists of a number of round or oval, slightly raised spots,
pinkish-red in colour, usually discrete, but sometimes con-
fluent.
The lymphatic glands of the neck are frequently swollen,
and when the eruption is very intense and diffuse, the
lymph glands in other parts of the body will be enlarged.
The mildness of the initial symptoms, the more diffuse
character of the rash, its rose-red colour, and the early
enlargement of the cervical glands, are the chief points of
distinction between German measles and ordinary measles.
Scarlet Fever. — This is a widespread affection, occurring
in nearly all parts of the globe, and attacking all races. It
varies greatly in the intensity of the outbreaks. In some
years it is mild ; in others, with equally widespread
epidemics, it is very malignant. The specific germ of it
is not known. The incubation period is two to four days,
318 HYGIENE
and the disease is highly infectious from the commence-
ment. The infection is spread in the early stages by the
breath and the secretion of the nose, mouth, and throat ;
later on the desquam ated scales from the skin are probably
the cause of infection. These are very liable to cling to
clothes, and the germs lie latent for a long period. The
discharges from the nose and ears, which are common in
this disease, are very infectious, and will rapidly spread
the disease.
The onset is as a rule sudden. There may be shivering.
Vomiting is one of the most common initial symptoms.
Sore throat and headache are generally present. The
skin is dry and hot, the face flushed, the tongue furred.
The rash appears in about twenty-four hours. It first
makes its appearance on the side of the neck and on the
chest, and then spreads to the abdomen and limbs, but,
curiously, it does not appear on the face, the palms of the
hands, or the soles of the feet. The rash appears as
scattered red points on a deep red skin. It disappears
about the seventh day.
The tongue is red at the tip and edges, and furred in the
centre. The papillae of the tongue are red and swollen, so
that after a few days, when the fur comes off, the surface
of the tongue appears red and rough — hence the name
" strawberry " or " raspberry " tongue.
Inflammatory condition of the throat is very common in
this disease, and the glands around the lower jaw are often
enlarged and painful. Another very constant sign is pallor
of the skin around the mouth, compared with the flush on
the cheeks.
With the disappearance of the rash and fever the skin
looks somewhat stained, dry, and a little rough. Gradually
the upper layer of the skin begins to separate. The peeling
generally starts on the sides of the neck and chest, spreads
next to the trunk and arms, and finally to the palms of
the hands and soles of the feet.
Mild cases of this disease may escape notice, and not be
DISABILITIES AND DISEASES OF CHILDREN 319
discovered until the desquamation stage. It is important,
therefore, during an epidemic to have constant routine
examination of the children's hands and fingers.
A child is generally considered infective until the peeling
is complete. This occurs about six to eight weeks after
onset. Special care should be taken of cases with dis-
charge from the nose and ears, or with throat trouble,
because these are highly infectious, and no child should be
allowed to return to school with any of these signs.
Diphtheria. — Diphtheria is very fatal in young children.
The diphtheria bacillus may be present in healthy throats
without causing any sign of the disease, but such a person
is able to infect other individuals. Special local predis-
posing causes are sore throats, nasal catarrh, laryngitis,
unhealthy conditions of the mouth and teeth. When the
bacilli gain entrance to an unhealthy throat, they are able
to set up the disease called " diphtheria."
From the above it is evident that, in order to prevent the
occurrence and spread of diphtheria, the children who have
the bacilli of diphtheria in their throat should be excluded
from school ; and all conditions which tend to produce a
diseased condition of the throat should be removed, such
as bad drainage, insanitary conveniences, access of sewer
gas and ground air into school, bad ventilation, and over-
heating.
The period of incubation of diphtheria is two to seven
days. The initial symptoms are those of an ordinary
febrile attack — slight chilliness, fever, and aching pains in
the back and limbs.
Then the child complains of sore throat. The glands
round the jaw and throat next become enlarged and
tender.
On examination of the throat, the mucous membrane of
the pharynx is reddened, and the tonsils are swollen. There
will also be one or more patches of a greyish-white mem-
brane seen over the tonsils, the palate, or the back of the
pharynx.
320 HYGIEXK
The membrane may form in the nose or in the larynx.
In the latter situation it gives rise to difficulty in breathing.
The germs are localized to the throat, nose, or larynx,
and these produce a poisonous substance called the " diph-
theria toxin," which is absorbed into the blood-stream and
causes the general signs of the disease. It is very important
that the disease should be diagnosed early, so that the anti-
toxic serum may be injected. The use of this serum has
greatly lessened the mortality.
In schools the infection spreads by the saliva and mucus
from the throats of those suffering from the disease, and by
infected pencils, pens, papers, books, drinking-cups, etc.
During an epidemic of diphtheria the school medical
c fficer should examine the throats of the children bacterio-
logically, and all the scholars which have the germs of this
disease in their throats should be excluded from school
until a further examination proves them to be free from
diphtheria bacilli.
Whooping-Cough. — " This is a specific affection charac-
terized by catarrh of the respiratory passages, with a series
of convulsive coughs which end in a long-drawn inspiration,
or ' whoop.' ' It is an extremely infectious disease among
young children, and a dangerous disease where unhygienic
conditions prevail. It is not in itself a dangerous disease,
but, like measles, it has as a frequent complication, bron-
chitis and broncho-pneumonia, and it is this which is so
fatal amongst young children.
The specific micro-organism has not yet been isolated.
There is a variable period of incubation from seven to ten
days. There are two stages to this disease — catarrhal and
paroxysmal.
In the catarrhal stage the child has the symptoms of
ordinary cold, there will be slight fever, running at the
nose, redness of the eyes, and a cough. After lasting for
a week or ten days the cough becomes worse and more
convulsive in character, and then the disease starts on its
paroxysmal or whooping stage, where associated with the
DISABILITIES AND DISEASES OF CHILDREN 321
cough is the long-drawn inspiration or whoop. Vomiting
often takes place at the end of a paroxysm of cough.
Infected children should be excluded from school for at
least two months, or for a longer period if the paroxysms
of cough accompanied with vomiting have not disappeared.
Children with whooping-cough want plenty of open air
and good feeding.
Mumps. — The period of incubation is from two to three
weeks, and there are rarely any symptoms during this
stage.
The onset is marked by slight fever, the child complains
of feeling ill, and soon after the characteristic swelling
appears on one side of the face and adjacent parts of the
neck ; later the swelling appears on the other side of the
face and neck. There is seldom great pain, but an un-
pleasant feeling of tension and tightness. Great incon-
venience is experienced in taking food, for the patient is
unable to open the mouth. Even speech and swallowing
may be difficult.
After persisting for seven to ten days, the swelling
gradually subsides, the child rapidly regains his strength
and health, and is none the worse for the attack.
Cases should not be regarded as free from infection until
the lapse of four weeks after the onset of the disease.
Chicken-pox. — " This is an acute contagious disease
characterized by an eruption of vesicles on the skin."
The disease is common amongst children, and spreads
rapidly through schools. It is a disease of childhood, and
the majority of cases occur between the second and sixth
year.
After a period of incubation of ten or fifteen days, the
child becomes feverish, and there may be a slight chill.
The eruption usually occurs within twenty-four hours. It
is first seen on the trunk, the back, or the chest ; afterwards
on the face and scalp, and then on the limbs. The rash
appears first as raised red papules ; these in a few hours
become transformed into hemispherical vesicles containing
21
322 HYGIENE
a clear or turbid fluid. After two or three days the latter
burst, dry up, and form scabs.
Children are not free from infection until the disappear-
ance of all scabs.
Smallpox. — At the present day smallpox is not com-
monly met with in our schools, and this undoubtedly is
due to the good results of vaccination. The incubation
period is nine to twelve days, and during this time no
symptoms are complained of. The onset commences com-
monly with a convulsion in a child, and repeated chills
in an adult. Then severe headache, marked pain in the
back, and sickness, set in. On the third or fourth day a
rash appears first on the forehead and anterior surface of
the wrists. It first appears as hard red spots, which
become vesicles or small blisters, and then pustules, which
dry up and form scabs.
More than a hundred years ago smallpox was frightfully
prevalent, and took toll of the best and noblest as well as
the poorest in the land. It scarred the faces and destroyed
the sight of many who escaped with their lives. Jenner's
great discovery has relieved the world from the terror of
this pest.
Heart Affections. — All forms of heart disorders may be
classified as functional, congenital, or acquired.
1. The Functional Disorders of the heart are quite common in child-
hood. The pulse may be irregular or too quick, or the heart's action
may be very rapid after slight exertions.
2. Congenital Affections are due to imperfect development of the heart.
Children with such often have a poor physique, and are very liable to
all forms of infection.
3. Organic or Acquired Heart Disease, — This is generally due to
rheumatic fever. When you ask for the history of the child, you will
be told that he has had rheumatic fever, tonsillitis, St. Vitus's dance, or
growing pains. It may also arise after scarlet fever, diphtheria, or other
infectious diseases.
Symptoms. — The child generally complains of shortness
of breath, palpitation, or cough, and shows very little
vitality. Fainting attacks are common. There are signs
DISABILITIES AND DISEASES OF CHILDREN 323
of bad circulation — cold feet and hands clubbed fingers.
The existence of murmurs in place of the normal sounds of
the heart is of little importance so long as the child has
signs of vigour and health.
Treatment. — The child should be sent to the medical
officer, who will advise the teacher regarding the amount
of work the child should do, etc.
Bronchitis. — This is due to inflammatory conditions of
the bronchial tubes, and arises very frequently from the un-
hygienic conditions under which children are often brought
up. It may follow measles or whooping-cough and other
infectious diseases. It varies greatly in its severity, from
a slight catarrhal condition of the larger tubes to a severe
form of capillary bronchitis, which may end fatally in a
short time.
Tuberculosis. — This is a disease caused by the entrance
and growth of the tubercle bacillus in the body. It may
affect any organ in the body, but in school-children it is
found more frequently attacking the lymphatic glands,
bones, joints, and the lungs.
Tuberculous Disease of Bones and Joints. — The disease
usually commences in a most insidious manner. It may
be dated back to a slight injury, or there may be no such
history. Slight impairment of movement, together with
some pain, especially after use, are the first signs. Thus, a
child with a tuberculous hip- joint will first complain of
slight pain after walking, and he will be noticed to limp.
Angular curvature of the spine is due to tuberculous disease
of the vertebrae. All children with such symptoms must
at once be sent to the medical officer.
Tuberculous Glands. — The glands most commonly at-
tacked by the tubercle bacillus are the glands of the neck.
Any chronic inflammatory condition of these glands pre-
disposes to their infection by tubercle. Thus, glands en-
larged secondarily to sore throats or carious teeth are very
liable to become tuberculous. The inflammation caused
by the tubercle bacilli may result in the formation of an
G24 HYGIENE
abscess, or the germs may be carried along the lymphatics
or bloodvessels, and be deposited in other parts of the
body, or result in a general dissemination.
Another set of glands commonly affected by tubercle
are the bronchial glands or mesenteric glands.
It has been held by many writers that the mesenteric
glands are infected by the germs being swallowed with the
food, and absorbed by the lymphatics of the intestine.
Pulmonary Tuberculosis, or Consumption. — In com-
parison with other forms of tuberculosis ; this is compara-
tively uncommon in school-children ; but its early recogni-
tion is not only necessary for the effectual treatment of
the individual sufferer, but also to prevent the infection of
other members of the school. This is the most infectious
form of tuberculosis, because by coughing and spitting the
bacilli are readily scattered about, and thus infect other
people.
It is very difficult to recognize it in the early stages, but
children suffering from a persistent cough or wasting should
be sent to the medical officer for examination.
Anaemia. — This is a term applied to a diminished amount
of haemoglobin in the blood. It will be remembered that
in Chapter IV. we gave an account of the properties and
function of the haemoglobin. The general symptoms and
signs of anaemia and the factors in their causation are
varied. The anaemia found amongst the children of our
large towns is directly due to their environment. Over-
\\ding, lack of proper food, and unhygienic surround-
ings, are the commonest cause of the disease. Anaemia
is associated with rickets, rheumatism, enlarged tonsils,
and adenoids.
The child becomes pale, languid, drowsy, disinclined for
t x« rtiou, readily fatigued, and the appetite becomes poor.
All children with the above symptoms should be Bent to
the medical officer for examination and treatment.
Vomiting. — This may arise from very trivial or serious
conditions. It may be a sign of slight indigestion, or it
DISABILITIES AND DISEASES OF CHILDREN 325
may be the commencement of a more serious affection of
the digestive tract. It also may be the first sign of the
onset of one of the specific fevers.
Diarrhoea. — This commonly arises from intestinal indi-
gestion due to the taking of too much or tainted food. In
towns, during hot weather, it may be due to infection with
certain germs, and will occur as an epidemic.
All children suffering from diarrhoea should be sent home
or to the medical officer for treatment.
Sore Throat. — All children suffering from a sore throat
should be sent home or to the medical officer for examina-
tion and treatment. The importance of attention being
paid to this condition lies in the fact that it may be in-
fectious in character, though the symptoms complained of
may be slight.
It may arise simply from catarrhal conditions of the
throat commonly associated with adenoids and enlarged
tonsils. On the other hand, it may be the first sign of
diphtheria, scarlet fever, and other infectious condi-
tions. Recurrent sore throat is generally associated with
rheumatism.
Skin Affections. — A large number of skin diseases affect-
ing children in our elementary schools are infectious, and
therefore it is advisable to exclude them from school when
they suffer from such conditions.
Verminous Conditions. — It is said that half of the
elementary school children have been affected to a certain
extent with verminous conditions. Head lice are the com-
monest, and their eggs, called " nits," are attached to the
hair, and removed with difficulty. These " nits " develop
into lice in five or six days under favourable conditions.
The irritation and scratching result in infection of the
scalp, so that sores and crusts will appear on it. The crust
should be removed by poulticing or bathing, and a weak
antiseptic ointment applied. The parents should be in-
formed of the condition of the child's head, and should be
advised to give the child a hot bath, using plenty of soap,
326 HYGIENE
and thoroughly cleansing the scalp and hair. After careful
drying, paraffin-oil should be thoroughly rubbed over the
hair and scalp. Great care must be taken not to bring a
flame near the child's head when this is done. The paraffin
is washed out with soap and water. This treatment should
be repeated two or three times, and it will result generally
in a complete cure.
Body lice lay their eggs in the clothes. Children affected
with these should be given a hot bath, and their clothing
be disinfected.
The Children Act, 1908, gives new powers and responsi-
bilities to local authorities to treat verminous children.
Itch, or Scabies.— This is a contagious disease caused by
the entrance of a small parasite into the skin, where it lays
its eggs. Infection is carried by personal contact, clothing,
towels, or bedclothes. The insect generally first attacks
the skin between the fingers and the back of wrist and
forearm. The intense itching causes the child to scratch
vigorously, and this results in a secondary infection with
other septic organisms. The itching, presence of burrows,
and signs of scratching between the fingers, are the signs
by which the condition is recognized.
Infected children should be sent away from school. The
parents should be advised to give them a hot bath, using
plenty of soap, followed by the application of sulphur
ointment. This should be repeated for three or four con-
secutive days. The clothing should be thoroughly dis-
infected before being worn again.
Impetigo. — This is an infectious condition attacking
dirty and neglected children. It often attacks the skin
around the mouth and the chin. Impetigo of the scalp is
generally associated with verminous conditions. It first
appears as small blisters surrounded by red patches ;
they dry up and form yellow crusts. It is spread by
scratching.
All children suffering from this condition should be
excluded from schools. The parents should be told to
DISABILITIES AND DISEASES OF CHILDREN 327
wash away all the crusts, and an antiseptic ointment should
be applied.
Eczema. — This is a term applied to a large number of
inflammatory conditions of the skin. It may be produced
by any form of irritant. It is not often infectious in
character. Children suffering from it should be sent home.
The treatment consists of removing the irritation and
applying soothing ointments or lotions.
Ringworm. — This is due to infection by a form of fungus.
It is very contagious and resistant to treatment. It
appears on the skin as a round, reddish, scaly patch, causing
itching and irritation. When affecting the scalp, the hairs
of the affected area become brittle and break off. This
results in bald, scurfy patches, on which may be seen
broken stumps of hair, very characteristic of the disease.
All cases should be excluded from school, and sent to the
medical officer for treatment. A good form of treatment
is exposure to X rays.
Favus. — This is another disease due to the infection of
the skin by a fungus. It is rather rare, and mostly confined
to the alien population of the East End of London. It is
very chronic and resistant to treatment.
Intestinal Worms. — Tapeworms are found at all ages,
but not uncommonly in children. They may give rise to
no symptoms, and even if they do so they are rarely
dangerous. If a person is aware that he has tapeworms,
it sometimes worries him, though he may have no symp-
toms at all. There may be abdominal pain, feeling of
sickness, diarrhoea, and anaemia. In some cases the
appetite is ravenous.
The diagnosis is confirmed by rinding segments of the
worm in the stools.
There are three prophylactic measures that should be
noted — namely, all tapeworm segments should be burnt,
and should never be thrown outside or into the water
closet ; all meat should be carefully examined and suffi-
ciently cooked.
328 HYGIENE
Every child suspected of having tapeworms should be
sent to the medical officer for treatment.
Round worms rarely give rise to any symptoms unless
they are very numerous, and then they may present the
following symptoms and signs : Diarrhoea, colic, sickness,
and convulsions. In the majority of cases the passage of
a worm by the anus or mouth is the first and only indica-
tion of its presence.
Threadworms generally live in the large intestine and
adjacent portion of the small intestine. They are often
present in large numbers, and wander down to the lower
part of the large intestine and the anus, in the neighbour-
hood of which they cause intense irritation, especially
during the night. The eggs of the threadworm are ex-
pelled with the faeces, and require to be taken into the
stomach before they redevelop. Children constantly re-
infect themselves by scratching the anus and conveying
the eggs by means of the finger-nails to the mouth.
The symptoms are, commonly, heat and irritation around
the anus and nose. In children, restlessness, nervous
irritation, choreic symptoms, and convulsions, may be seen
Brisk saline purgatives to expel the worms, and extreme
cleanliness to prevent reinfection, are usually all that is
required.
All children suspected to suffer from intestinal worms
should be sent to the medical officer for treatment.
CHAPTER XII
MEDICAL INSPECTION OF SCHOOLS
The Organization of Medical Inspection of Schools.— Sec-
tion 13 of the Education (Administrative Provisions) Act,
1907, states that—
The powers and duties of a Local Education Authority under Part III.
of the Education Act, 1902, shall include—
1. Power to provide for children attending public elementary schools,
vacation schools, vacation classes, play centres, etc.
2. The duty to provide for the medical inspection of children immedi-
ately before, or at the time of, or as soon as possible after, their admission
to a public elementary school, and on such other occasions as the Board
of Education direct, and the power to make such arrangements as may
be sanctioned by the Board of Education for attending to the health
and physical condition of the children educated in public elementary
schools.
The Board of Education issued a Memorandum on Medical
Inspection of Children in Public Elementary Schools, ex-
plaining the various provisions made by the above sections
of the Education Act. The following are briefly the most
important points dealt with in the Memorandum :
1. " The aim of this new legislation is not merely to obtain a physical
or anthropometric survey or a record of defects disclosed by medical
inspection, but to improve the physical conditions, and, as a natural
corollary, the moral and mental conditions of coming generations."
2. Organization. — The respective functions of the Board of Education
and the Local Education Authorities are clearly defined by the Act :
" The duties thrown upon the Board consist in advising Local Educa-
tion Authorities as to the manner in which they should carry out the
provisions of the Act, and in supervising the work they are called upon
to undertake ; in giving such directions as may be necessary regarding
the frequency and method of inspection in particular areas ; and in con-
sidering and sanctioning such arrangements for attending to the health
329
330 HYGIENE
and physical conditions of the children as may be submitted to them by
individual authorities. The Board will also collate the records and
reports made by the authorities, and will present an annual report to
Parliament. The duty of carrying out the medical inspection has been
entrusted by Parliament to the Local Education Authorities and not to
the Board. Each authority must therefore in due course appoint such
medical officers or additional medical assistance as may be required for
the purpose. The Board view the entire subject of school hygiene as
an integral factor in the health of the nation. The application of this
principle requires that the work of medical inspection should be carried
out in intimate conjunction with the Public Health Authorities, and
under the direct supervision of the Medical Officer of Health."
3. Teachers. — The necessity of the cordial sympathy and help of the
teachers is specially mentioned.
4. The Parents. — " The increased work undertaken by the State for
the individual will mean that the parents have not to do less for them-
selves and their children, but more. Their co-operation is very essential,
and will prove effective and economical. Efforts must be made to obtain
their presence at the medical inspection of the child."
6. Character and Degree of Medical Inspection. — " The fundamental
principle of the new Act is the medical inspection and supervision not
only of children known or suspected to be weakly or ailing, but of all
children in the elementary schools, with a view to adapting and modify-
ing the system of education to the needs and capacities of the child,
securing the early detection of unsuspected defect*, checking incipient
maladies at their onset, and furnishing the facts which will guide Educa-
tion Authorities in relation to physical and mental development during
school life."
The directions given in this circular as to the degree and
frequency of inspection refer only to the minimum medical
inspection, the effectiveness of which will in future be one
of the elements to be considered in determining the effici-
ency of each school as a grant-aided school.
The statutory medical inspection should, at entrance or
at subsequent inspection, take account of the following
matters :
1. Previous disease.
2. General conditions and circumstances :
(1) Height and weight.
(2) Nutrition (good, medium, bad).
(3) Cleanliness (including vermin of head and body).
(4) Clothing (sufficiency, cleanliness, and footgear).
MEDICAL INSPECTION OF SCHOOLS 331
3. Throat, nose, and articulation (mouth-breathing, snoring, stam-
mering, tonsillar and glandular conditions, adenoids).
4. External eye diseases and vision testing.
5. Ear disease and deafness.
6. Teeth and oral sepsis.
7. Mental capacity (normal, backward, defective).
8. Present disease or defect :
[(1) Deformities, or paralysis.
(2) Rickets.
(3) Tuberculosis (glandular, pulmonary, osseous, or other
forms).
(4) Diseases of skin and lymph glands.
( 5) Disease of heart or lungs.
(6) Anaemia.
(7) Epilepsy.
(8) Chorea.
(9) Ruptures.
(10) Spinal disease.
(11) Any weakness or defect unfitting the child for ordinary
school life or physical drill, or requiring either exemption
from .special branches of instruction or particular super -
Regulations. — " It is suggested that each child should be
inspected four times during its school life. The first inspec-
tion should take place on admission to school, the second
three years after, the third after another interval of three
years, and the fourth on leaving school.
" Provision should therefore be made by each authority,
when the Act has been sufficiently long in operation to ba
in normal working, for the inspection in each year of —
(a) the children newly admitted ; (&) the children in the
school who in that year had matured for their second in-
spection ; (c) those who had matured for their third inspec-
tion ; (d) those about to leave school."
" The following further regulations should be observed :
1. " The inspection should be conducted in school hours and on school
premises, and in such a way as to interfere as little as may be with school
work. The examination of each child need not, as a rule, occupy more
than a few minutes.
2. " The convenience of the teaching staff and the circumstances of
each school must receive consideration, and in these matters and in
332 HYGIENE
actual examination the medical officer will no doubt exercise sympathy
and tact, giving due thought to the personal susceptibilities of those
concerned.
3. " Facts revealed by inspection must be entered in a register kept
at the school, the confidential nature of many otthe entries being care,
fully respected.
4. " Every school medical officer should make an annual report to
the Local Education Authority on the schools and children under his
superintendence.
6. " A number of suggestions are given regarding the facts that should
be stated in the report of the medical officer."
Amelioration and Physical Improvement.— " The aim of
the Act is practical, and it is important that Local Education
Authorities should keep in view the desirability of ultimately
formulating and submitting to the Board for their approval
schemes for the amelioration of the evils revealed by medical
inspection, including, in centres where it appears desirable,
the establishment of school surgeries or clinics for further
medical examination, or the specialized treatment of ring-
worm, dental caries, or diseases of the eye, the ear, or the
skin.
" Verminous heads and bodies form another illustration
of a common condition in which amelioration can be secured
by school nurses.
" It is of the utmost importance to remember that baths,
with the necessary accompaniments of soap, sponges,
towels, etc., should be utilized, not merely for the immediate
and obvious purpose of cleansing the bodies of the children,
but also as a humanizing influence and as the means of
inducing habits and instincts of cleanliness, and of incul-
cating practical lessons in the value of personal hygiene
and in self-respect."
Objects of Medical Inspection. — The objects of medical
inspection of schools are —
1. To discover any physical or mental defects which will prejudicially
affect the future physical or mental development of a child.
2. To diagnose conditions of an infectious or contagious character
which render it inadvisable that children suffering from such conditions
should associate with other members of the school.
MEDICAL INSPECTION OF SCHOOLS 333
3. To ascertain whether the educational methods are adapted to the
physical and mental condition of the child.
4. To examine the hygienic conditions of the school buildings (ventila-
tion, light, heating, type of, and arrangement of, desks, etc.). •
Method of Medical Inspection. — Different opinions prevail
regarding the exact method of inspection of schools and
school-children, and it is impossible to lay down any hard-
and-fast rules that would be acceptable to all local authori-
ties. The following should be regarded as general lines
upon which the inspection should be conducted :
The necessary notification is sent to the head-teacher
concerned, stating the group of children it is intended to
examine, and the day and time upon which such examina-
tion is to be made. The head- teacher then sends out
notices to the parents or guardians of the children selected
for examination, stating the time of the examination, and
requesting their presence at the school at the appointed
time.
The teacher should see that the health schedules of the
selected children are filled up as far as possible in readiness
for the inspection.
In the routine of medical examination it would be well
that the Board of Education Schedule, or some modifica-
tion of it, should be followed. The history of any previous
disease is taken from the parent or guardian. The child's
height and weight are taken, and notes made regarding the
nutrition, cleanliness, and clothing of the child. The
various points in the Schedule are taken seriatim. The
presence of skin affections, external eye disease, otorrhcea,
enlarged glands, defective teeth, etc., can be recognized at
a glance. The heart and lungs should then be examined,
and the condition of abdominal viscera ascertained. By
such means the normal can be separated from the abnormal.
Further detailed examination may be applied to the
children who are abnormal, to find out their exact condition.
Since at present it is impossible in a large number of
cases for the school medical officer to treat the abnormal
334 HYGIENE
conditions that he finds, his chief duty is to separate the
abnormal from the normal children, and to classify the
abnormal conditions into various groups.
Treatment. — The general lines of treatment for various
ailments will be indicated by the school medical officers.
If the parents can afford it, the children may be treated
by a private practitioner. In the majority of cases the
parents will not be able to pay their doctor's fees, especially
when the condition requires prolonged treatment, and thus
some arrangement will have to be made with local hospitals
and dispensaries for the treatment of school-children.
The ideal thing would be the equipment of a school
clinic, where the medical officer could personally supervise
the treatment of his cases.
The teacher, by learning some of the common signs of
dinfuni mentioned in Chapter XI., will soon be able to
apply such knowledge, and thus identify some of the
common physical and mental defects of the children in the
school. It is most important that the teacher should have
a good knowledge of the early symptoms and signs of
infectious diseases, and thus early and more effectual means
may be taken to prevent an epidemic in the school.
School Closure.— During an epidemic of infectious disease
in a neighbourhood, school closure in the past has been
practised in an arbitrary manner when the school attend-
ance had fallen a good deal below the average. Such a
means, especially in towns, is generally useless in pre-
venting the spread of infection, because already the
children have been exposed to infection, and it is practi-
cally impossible to prevent them coming in contact with
each other whilst playing in the streets.
The only successful way of preventing the spread of
infectious disease is to train the teachers in methods that
will enable them to recognize the early symptoms and signs
of all infectious diseases met with during school life.
A child suspected of having the signs and symptoms of
any such disease should be sent home at once. The teacher
MEDICAL INSPECTION OF SCHOOLS 335
should inform the medical officer of the fact. The exact
course that he will take regarding that particular child will
depend whether the child is attended by a private doctor
or not.
If the diagnosis has been confirmed, the teacher and
medical officer should closely observe the other members of
the class, especially the associates of the child first infected
The exact methods taken to prevent the infection will be
indicated by the medical officer.
Disinfection. — In order to discuss some of the general
lines of disinfection of schools, let us define certain terms
which are often used and confused in this connection —
namely, disinfectant, antiseptic, and deodorant.
A disinfectant is a substance in certain strength, which is
able to destroy germs which come in contact with it. An
antiseptic is a substance that can stop the growth of micro-
organisms, and prevent decomposition of organic material.
A deodorant is a substance that is able to oxidize or absorb
substances causing evil odours.
All substances which are disinfectants are antiseptics ;
but, on the other hand, deodorants and antiseptics are not
disinfectants.
Disinfectants are intended to destroy micro-organisms,
and to ascertain their relative value methods have been
applied to determine their relative effects upon culture of
certain micro-organisms, and comparing them in each case
with a certain standard. Rideal and Walker have sug-
gested that carbolic acid should be the standard disin-
fectant, and that the Bacillus typhosus or B. coli communis
(the former causes typhoid fever, and the latter is present
in the intestine of every person) should be the germ used
in all tests. In modifications of the test the germs are
placed in certain definite media, because the surroundings
of the germ most influence the power of the disinfectant.
Processes of Disinfection — 1. Burning. — This is the best
means of disinfection, but, unfortunately, is only applicable
to articles that are of no value.
336 HYGIENE
2. Boiling. — This is also a very efficient means of dis-
infection, but here again its application is limited.
3. Hot Air. — This is efficient, but several objections may
be raised against it — namely, prolonged exposure, destruc-
tion of large numbers of articles — and hence its limited
application.
4. Steam. — This gives very good results when proper
precautions are taken.
5. Application of Liquid Disinfectants. — Such disinfec-
tants may be used to wash the walls of a room, or articles
which require disinfection may be placed in such solutions.
Some of the common liquid disinfectants are solutions of
corrosive sublimate, carbolic acid, and other tar prepara-
tions, bleaching powder, formaldehyde, etc.
6. Application of Gaseous Disinfectants. — This is a method
that is often applied to rooms. After all the doors and
windows have been carefully sealed, certain gas is produced
inside the room, and allowed to remain there for at least
twenty-four hours. Examples of such disinfectants are
formaldehyde, sulphur dioxide, and chlorine.
Disinfection of the Schoolroom. — Every means must be
taken to prevent the accumulation of germs in the school-
room. This is of much greater importance than devising
any plan to destroy such germs after their entrance and
accumulation.
The teacher must have greater faith in good ventilation
and windows, allowing abundant supply of fresh air and
sunlight, and in frequent and efficient use of soap and
water, than in any other form of more artificial disinfec-
tion. If such precautions are taken, the school will
harbour but few noxious germs, and will certainly not be
a very potent factor in the spread of infectious disease.
It may be necessary at times to apply more potent
methods of disinfection — e.g., when an epidemic of diph-
theria or scarlet fever has occurred.
The disinfection should be carried out by the local
sanitary authority.
MEDICAL INSPECTION OF SCHOOLS 337
Curtains, rugs, etc., should be sent for steam disinfection.
Books may be burnt, or disinfected by hot air, or ex-
posed to 3 per cent, formalin vapour.
Pencils, pens, and slates should be placed in a disin-
fectant fluid.
The exposed surfaces of the schoolroom may be disinfected
by one of three methods :
1. By the use of sprays, where the disinfectant is applied directly
by means of a spray — corrosive sublimate, or formaldehyde, can be
applied by such method.
2. By washing the walls, ceilings, and floors with a disinfectant
solution — formaldehyde, lysol, or corrosive sublimate, can be used.
3. By charging the air with certain gases or vapours, and allowing
them to remain in contact with the walls for at least twenty-four hours.
After any of the above methods, the walls, ceilings, and
floors should be well washed with soap and water, and then
thoroughly dried by a good current of air and sunlight.
FIRST AID IN INJURIES AND AILMENTS.
Fractures. — The causes of fractures are threefold —
namely : (a) direct violence, when the fracture occurs at the
part that is struck ; (b) indirect violence, when the bone gives
way at a distance from the site of application of the force ; (c)
muscular action. This is due to excessive contraction of some
of the muscles of the body. Fracture of knee-cap often arises
in this way. Fractures may be either simple or compound.
A simple fracture is one in which the skin is unbroken,
and the external air does not communicate with the site
of injury in the bone.
A compound fracture is one in which the force producing
the injury is so great that one of the broken ends of bone
is forced through the flesh and skin or mucous membrane,
thus resulting in an open wound as well as a fracture.
A ompound fracture is a very serious injury, because
there is great danger in micro-organisms gaining access to
the wound, and the bone setting up an inflammation result-
ing in general blood-poisoning. Before the introduction of
22
338 HYGIENE
antiseptics into surgery the death-roll from compound
fractures was very great.
The signs of a fracture are — (a) pain, bruising, or swelling
lit the site of fracture ; (6) loss of power of movement of
l he part involved ; (c) change in shape of the limb, or de-
formity from displacement. This results from three factors
— namely, the direction of the violence, the weight of limb,
and contraction of muscles.
The diagnosis of a fracture is sometimes difficult, but
every doubtful case should be treated as a fracture until
the doctor arrives.
The principle of the first-aid treatment of fractures is to
adopt means to prevent any undue movement of the frag-
ments of the fractured bone until medical help arrives.
Thus immobility of the parts must be secured before any
movement of the body is allowed. Injudicious movement
or rough handling, especially by untrained persons, aggra-
vate the condition, and may even convert a simple to a
compound fracture.
Fracture of the Skull. — If a fracture of any part of th<>
skull is suspected, the patient should be placed on a bed
or couch with head well raised, and cotton- wool or lint
soaked in cold water should be applied to the site of injury.
The doctor should be sent for immediately.
Fracture of the Lower Jaw is generally due to direct
violence, and is diagnosed by feeling a depression at some
area of the bone. The patient will be unable to speak
properly, and will often bleed at the mouth, because tin*
lining of the mouth is usually torn.
If the jaw is displaced, it should be gently raised to its
natural position. One handkerchief is fastened under the
jaw and round the top of the head, and another is passed
round the chin to the back of the neck.
Fracture of Ribs may be due to direct or indirect violence.
The patient will complain of having felt something snapping
or giving way, and of a sharp localized pain at the site of
the injury, increased on deep breathing and coughing. A
MEDICAL INSPECTION OF SCHOOLS 330
grating sensation is felt over the spot at each breath. A
broad bandage should be fastened tightly round the chest,
or the injured side of the chest may be strapped with broad
strips of adhesive plaster, each strip being applied when
the chest is in a state of forcible expiration.
Fracture of the Collar-Bone, or Clavicle. — This is one of
the commonest bones to be broken. It may arise from
direct or indirect violence, generally due to the latter.
There will be drooping of the corresponding shoulder, an
irregularity will be felt on passing the finger along the bone
and the patient will be unable to raise the arm any farther
than the shoulder.
Place a pad of cotton- wool or rolled-up handkerchief in the
armpit ; the arm should then be placed in a sling, and fixed
to the side by passing a bandage round the arm and chest.
Fractures of the Upper Limb. — Fractures of the humerus,
or arm-bone, are caused by direct or indirect violence. Two
temporary splints should be obtained and covered with
cotton- wool, or wrapped round with handkerchiefs. One
of the splints is placed on the outer side of the arm from
the shoulder to the outer side of the elbow ; the other
should run from the armpit to the inner side of the elbow.
These splints should be firmly bandaged to the arm, and
the forearm placed in a sling.
If a fracture of the forearm is suspected, two pieces of
wood should be obtained and bound at right angles to each
other, thus forming an angular splint. The arm should
then be bent at a right angle, and fastened to the splint by
means of handkerchiefs or pieces of bandage. The fore-
arm should then be placed in a sling.
The best way to apply temporary treatment in a frac-
ture of any of the bones of the hand is to fasten it by a
bandage to a broad flat splint, and then the forearm
placed in a splint.
Fractures of Lower Limb. — In fracture of the thigh, the
first thing that must be done is to take means to prevent
shortening of the limb. Therefore the lower portion of
340 HYGIENE
the injured limb should be held by both hands, and then
pulled gently until both limbs are of the same length.
Fasten both feet together by means of a handkerchief
applied below the ankles. A long splint may be extem-
porized from a broomstick, or any other piece of wood or
metal which is about the right length. It must run from
the armpit to the foot. Both limbs should be further
bound together by a handkerchief tied around them at the
knee, and another round the thighs.
Great care should be taken when removing a patient \\ it h
a broken lower limb from the place where the accident
happened to his home or hospital. He may be carried in
me arms, or a blanket, extemporized stretcher, or in an
ambulance.
A fractured leg is treated very similarly to a broken
thigh, except that the splint runs from above the knee to
below the feet.
In applying bandages to a limb, great care must be taken
not to stop the circulation. See that the fingers or toes
• 1< • not turn blue and cold.
Sprains and Dislocations. — If a sprain is seen immediately
after the accident, the injured part should be held under
a cold-water tap. The limb should then be raised, wrapped
in cotton-wool, and firmly bandaged, a splint being put
on to keep the part at rest. These measures will limit tin-
subcutaneous bruising. Hot fomentations is the best form
of treatment that can be applied to relieve the great pain
which follows a few hours after a sprain, but their applica-
tion should be limited, because they tend to increase the
after-swelling.
Dislocations are generally caused by injury, and have
the following signs : Evidence of local trauma — e.g., pain,
bruising, and swelling of the soft tissues ; deformity of the
limb, due to the abnormal position of the head of the dis-
placed bone ; and restricted mobility of the affected joint,
resulting in impairment of function of the limb. It is b?st to
leave all forms of dislocation alone until the doctor arrives.
MEDICAL INSPECTION OF SCHOOLS 341
Bruises. — These are very common accidents in the play-
ground. They are treated on the same lines as sprains — by
applying a cold-water compress to the site of the injury,
giving rest to the part, and firm bandaging to help absorp-
tion of any inflammatory fluid.
Stings and Bites. — Stings of insects, such as bees and
wasps, may be very irritating and painful, but they are
rarely dangerous except when they are on the tongue, or
very numerous, or some secondary infection such as ery-
sipelas supervenes. Great care must be taken that the
sting or poison-sac is not left in the body ; then a strong
solution of washing-soda should be rubbed on the spot.
Bites of animals cause ragged wounds, which take a very
long time to heal. Free bleeding should be allowed for
some time, aided by suction. Having previously cleansed
the wounds, they should then be touched with caustic,
or a piece of lint soaked in strong Condy's fluid applied.
In the case of a poisonous snake- bite, the wound should be
scarified, and some crystals of permanganate of potash
rubbed in. The same treatment should be applied to the
sting of the weaver — a fish with a poisonous spine in its
dorsal fin.
Wounds. — The great principle underlying treatment of
all kinds of wounds is to keep them clean. As long as
wounds are kept clean, they will in the great majority of
cases heal up quickly.
Small wounds, such as simple abrasion caused by falling
on the ground, should be cleaned with water, and then
bandaged, the sole object being to protect the part until
the formation of a scab, which is Nature's means of pro-
tecting wounds.
The treatment of small clean cuts, such as those caused
by a penknife, is the same.
The bleeding from slight wounds generally stops very
quickly of its own accord. In some cases, however,
bleeding will continue, and will require more effectual
treatment.
342 HYGIENE
Bleeding may be capillary, venous, or arterial in origin.
Capillary haemorrhage appears as slow oozing of blood
from the raw surface. This is treated by bandaging a cold-
water compress tightly on the site of the bleeding.
Venous haemorrhage is characterized by the dark colour
of the blood. This can be stopped by raising the limb, and
by bandaging a cold-water compress firmly on the wound.
Arterial haemorrhage is the most dangerous form of
bleeding, and in some cases may be very difficult to stop.
The blood is bright red in colour, and comes out in a con-
tinuous stream in the case of the smaller arteries, or in
jete synchronous with the pulse in the larger arteries.
The slight cases of arterial bleeding may be stopped by
firmly bandaging a compress over the wound.
Pressure may be applied continuously by some form of
tourniquet. This may be applied by tying a knot in tin*
middle of a handkerchief, and pressing this on the spot
where compression is needed. A piece of wood or a flat
stone may be tied on by means of a handkerchief, and the
pressure increased by passing a stick under the handker-
chief and twisting it round.
It should be remembered that the pressure of a tourni-
quet, though sometimes necessary, is always more or 1< -
injurious, and in five or six hours is likely to kill the tissu-
below the point where it is applied.
If bleeding takes place from one of the large arteries of
the limbs, compression of the main artery against the bone
at a point nearer the heart than the wound is a very
effectual method of stopping the haemorrhage. The exact
point where pressure should be applied varies with the
course of the particular artery involved.
Bleeding from the face and head will usually be stopped
by pressure against the bony surface beneath.
Bleeding from the artery of the armpit may be checked
by placing a pad of cotton-wool or lint, or a rolled-up
duster, in the armpit, and bandaging the arm to the side.
Bleeding from the artery of the arm is stopped by placing
MEDICAL INSPECTION OF SCHOOLS 343
a pad of cotton-wool over the wound and applying a firm
bandage.
If the blood comes from the arteries of the forearm,
place a pad of lint over the elbow, flex it, and bandage the
forearm on to the arm. Bleeding from the palm is checked
by making the patient grasp a pad of lint and bandaging
the fingers over it.
Bleeding at the back of the knee can be stopped by
placing a pad of lint over the wound, flexing the leg, and
bandaging it firmly to the thigh. Bleeding from the
arteries of the leg is checked by a similar process.
Hsemorrhage from the arteries of the foot is checked by
direct pressure, or by the same treatment as applied in a case
of bleeding from the arteries of leg.
Bleeding from the Ears after rather severe accidents is
generally due to a fracture of the base of the skull. In
such cases the doctor should be sent for at once.
Nose-Bleeding. — This arises from various conditions. It
is generally unilateral, and can in a large number of cases
be stopped by grasping the nostrils firmly, and allowing
the blood to collect within and giving it an opportunity
to clot.
The child should sit in a chair with the head thrown
back, and cold water may be applied to the root of the
nose or the nape of the neck. In other cases the nose can
be syringed out by any styptic solution — e.g., alum solu-
tion.
Burns and Scalds. — Remove the clothing ; but any part
that is stuck to the skin should not be forcibly removed,
but left there after cutting all loose parts around. Some
cotton-wool soaked in olive-oil or linseed-oil and lime-water
should be placed on the wound. Another layer of cotton-
wool should be placed over it, and then a bandage applied.
Shock is a very common feature associated with burns
and scalds, and should be treated by placing the patient
in bed, keeping him warm, and administering morphia or
stimulants when required.
344 HYGIENE
The best treatment when a child's clothes catch fire is
to wrap him instantly in some thick woollen material, such
as a coat, mat, rug, or blanket. This will put out the fire.
Fainting. — This arises from temporary weakness of the
heart, resulting in a lack of blood-supply to the brain.
The patient should be given plenty of fresh air, and the
body should lie full length on the floor.
Foreign Bodies in the Throat. — If any foreign body sticks
in the throat, pass the forefinger into the mouth, and try
to remove the body causing the obstruction. Even if
not successful in reaching the obstruction, vomiting will
have been incited, and this will very frequently be suffi-
i icri t to result in its expulsion.
Foreign Bodies in the Stomach. — If a small object, such
as a pin, nail, plum-stone, or small toy, has been swallowed,
aperients should not be given, and the diet during the next
f w meals should be dry, consisting of plenty of bread and
vegetables. The course of a metal object can be followed
by means of the X rays.
Eye. — The most common accidents to the eyes that occur
in schools arc the lodgment of foreign bodies, or bruising.
If a foreign body sticks in the eye, evert the upper or lower
eyelid ; and if the body is seen, remove it by a fine camel-
hair brush or the wetted corner of a clean handker< hi< f.
If it is not easily dislodged, do not make any further
at tempts, but send the child to see a doctor. If after the
removal of the foreign body the eye feels very sore, place
a drop or two of castor-oil on the cornea. Teachers should
be taught by the medical officer how to evert the ey< -lid
properly. Bruises of the eyelid are treated on the same lines
as bruises elsewhere — cold-water compress and bandage.
Ear. — Foreign bodies in the external ear do not give rise
to any symptoms unless it is a living creature, such as an
insect. It will be well for the teacher never to attempt
to remove a foreign body from the ear, because damage i»
so readily done by persons not medically trained ; therefore,
leave all such cases to the doctor.
MEDICAL INSPECTION OF SCHOOLS 345
Skin. — Common accidents to the skin are cuts, bruises,
and lodgment of foreign bodies. Wounds of the skin
should be treated on the lines previously indicated. Foreign
bodies, such as thorns, needles, etc., should be removed ;
but if the teacher should have any difficulty, he should ask
for the help of the medical officer.
Nose. — The treatment of nose-bleeding has been dis-
cussed above. If a small object is lodged in the nose, it
will excite sneezing, and this is often enough to remove it ;
if not, send the child to see the doctor, because interference
by untrained persons is contra-indicated.
Poisoning. — Poisoning does not often occur in schools ;
but in case such misfortune might happen, the teacher
should know some of the principles that will guide him
in the treatment of such cases until the arrival of the
doctor. The general condition of the patient must be
treated. If there is any prostration, he should be placed
on a bed or couch, and kept warm. Stimulants, such as
strong tea or coffee, should be administered. Means must
also be taken to get rid of the poison that has not been
absorbed from the stomach, and the only method that can
be applied by the teacher is the administration of emetics —
that is, substances which induce vomiting. It must be
remembered that the administration of emetics, and even
the use of the stomach-pump by the doctor, is contra-
indicated in some cases ; therefore, before applying such
treatment, some knowledge must be attained regarding the
nature of the poison that has been taken.
If a corrosive poison has been taken, shown by blisters
around the mouth and excoriations of the lining membrane
of the mouth, no form of emetic should be given, except in
the case of carbolic-acid poisoning.
If any form of acid, such as vitriol or spirits of salt, has
been taken, give chalk or magnesia.
If an alkali has been taken — e.g., caustic alkali — give
large amounts of water, dilute vinegar, or citric acid. Give
also raw eggs, milk, and oils.
346 HYGIENE
If an irritant poison, such as arsenic, lead, or copper salt,
has been taken, give an emetic (tablespoonful of mustard in
a tumbler of water, or strong salt solution). Give raw eggs,
milk, and oils, and treat the general condition by rest and
stimulants. If there is any suspicion of phosphorus-
poisoning — e.g., taking heads of matches — do not give oils.
If a narcotic poison has been administered — e.g., laud-
anum— give emetics ; and if the patient is sleepy, keep him
awake by walking him about, flapping him with a wrt
towel, and shouting at him.
Treatment of those apparently Drowned. — A doctor should
be sent for at once. The clothing should be loosened about
the neck and chest, and the mouth cleared of water an 1
<lirt, if present. The tongue should be drawn forwanN.
Every means should be taken to keep the patient warm.
Wrap him in hot blankets, and place hot-water bottl* >
near him. Artificial respiration should at once be resorted
to, and there are two methods in use at present — namely
those of Sylvester and Schaefer.
In Sylvester's method the patient is placed on his back,
with a pillow or something similar beneath the should* i
Care should be taken to have the tongue pulled forward
and the mouth kept open. The arms are grasped below
the elbow, and then pull them gradually over the head.
This will dravv air into the lungs.
Artificial expiration is produced by bending the arms
and forcibly pressing them against the chest-wall. These
movements should be done about twenty times a minute.
They should be kept up for at least an hour, though there
may be no sign of return to life. One great objection to
Sylvester's method is that the performer gets very tired,
and Schaefer has devised a method which involves less
fatigue.
In Schaefer's method the patient lies with his face
downwards, and the upper part of the chest is supported
by a pillow or a thick folded garment.
The operator stands at the side of the subject, facing his
MEDICAL INSPECTION OF SCHOOLS 347
131. — SYLVESTER'S METHOD OF ARTIFICIAL RESPIRATION: MEANS
OF PRODUCING INSPIRATION.
•MB
FIG. 132. — SYLVESTER'S METHOD OF ARTIFICIAL RESPIRATION : MEANS
OF PRODUCING EXPIRATION.
348 HYGIENE
head, and places his hands on each side over the lower
part of the back (lowest ribs). " He then slowly throws
the weight of his body forward to bear upon his own arms,
and thus presses upon the thorax of the subject and forces
air out of the lungs. Then he gradually relaxes the pres-
Fio. 133. — SCIIAEFER'S METHOD or ARTIFICIAL RESPIRATION.
sure l>y bringing his own body up again to a more erect
position, but without moving the hands." This method
docs not involve so much fatigue to the operator, and
hence can be carried out for much longer periods by the
person.
INDEX
ABSORPTION, 66, 95, 96. 97
of carbohydrates, 97
of fats, 97
of proteins, 97
Accommodation, 227
Adenoids, 171, 172
Advantages of open-air life, 170
Air, conditions causing impurity |
in crowded rooms, 276, 277
inspired and expired, 161, 162
Alcohol, 108
Alcoholism and mental deficiency, \
215
Anaemia, 324
Anatomy, macroscopic and micro- ;
scopic, 1
Angular curvature of the spine, 54 I
Animal cell, definition of, 1
structure of, 1
Animals, classification of, 3
Ankle-joint, 39
Anterior chamber of eyeball, 225
Antiseptic, 335
Antitoxin, 305
Aphasia, motor, 248
Aqueous humour, 225
Arnott and Boyle's valves, 283
Artery, 123, 131, 132
Artificial respiration Schaefer's
method, 346, 348
Sylvester's method 346
Arytenoid cartilages, 245
Association, 208, 209
areas, 209
cell, 191
fibres, 209
of words and objects, 213, 214
Astigmatism, 235
Atlas, 28
Attitudes, 51
Axis, 29
Axon, structure of, 190
Backbone, 26
Backboned animals, 3
Backboneless animals, 3
Backward children, 219, 220
treatment of, 220
Bacteria, 300-305
Basal ganglia, 201
Base of skull, 23
Basilar membrane, 24 1
Baths, 274
Bile, 90
composition of, 90
physiological role cf, 92
pigments, 90
salts, 90
tests for, 91
Bites, 341
Blackboards, 295
Bladder, 186, 187
Bleeding, capillary, venous, and
arterial, 342
from the ears, 343
from the nose, 343
Blepharitis, 235, 236
Blood capillaries, 123
carbon dioxide of, 166
circulation of, 123
coagulation of, 121, 122
composition of, 112
corpuscles, red, enumeration,
114
function, 115
origin and life -his-
tory, 116
structure, 113
white, formation, 118
function, 117
structure, 117
functions of, 112
gases of, 164, 165
oxygen of, 165
plasma, 121
349
350
HYGIKNE
Blood pressure, 143
velocity of, 145
Bone, 14
breast, 30
cheek, 26
chemical composition of, 20
classification of, 14-18
compact, 18
development and growth of,
21
ethmoid, 26
flat, 17
formation, intracartilaginou*.
22
intramembranou*, 21
irregular, 18
lachrymal, 26
long, 14
lower jaw, 25
limb, 34
microscopic structure of, 18
mixed. 18
nasal, 26
short, 17
spongy, 19
upper jaw, 25
limb, 31
Bones of the ear, 239
B .wditch, 253
Brain, anatomy of. 200-203
functions of. 204-208
motor area of. 20."i
Breathing exercises. 169
Bronchi and bronchioles, 153
Bronchitis, 323
Bruises, 341
One-sugar, 65
Capillaries, 131, 133
Carbohydrates, chemistry of, 64
nutritive uses of, 106
Cardiac cycle, 138, 139
-t the body. 173
Carpal bones, 34
( 'auda equina. 194
(Vll substance, 2
(Vat re, cardio-inhibitory, 149
hearing, 207
motor-speech, 213
respiratory, 167
taste and smell, 208
vasomotor, 147, 148
visual. 207
word-hearing, 213
• Centre, word-seeing, 2H
writing, 213
j Cerebellum, anatomy of, 201
functions of, 205
Cerebral hemispheres, 201-203
Cerebro-si 'nal fluid, 197
Cerebrum, anatomy of, 201
functions of, 205
Cesspools, 269
Chaddock's window, 280. 281
Characteristics of children in
health, 12-13
Cheeks, 70
Chemistry of foodstuffs, 61
Chicken- pox, 321
Child, characteristics in health,
12. 13
development. 10
growth of, 12
structure at birth 1 1
Chimney in ventilation, 283
Chlorophyll, 300, 301
Cholesterin, 91
Chorea. 307. 308
Choroid, 224
Ciliary muscle, 216
processes, 224
Circulation of the blood, course of.
135-138
microscopic study of, 134
through the lungs, 154.
156
Circulatory system, relation to-
nervous system, 146, 147
Class! float ion of animals, 3
Clavicle, 31
Closet accommodation, 269-273
conservancy system. 270
construction of, 273
earth, 271
pail system, 270
privy or midden, 270
short hopper or wash -down,
272
trough, 272
water. 271
water-carriage system of,
271
Clothes, functions of, 177
selection of, 177
Coa, 8
Cochlea. 240
Cold, sensation of, 252
Columella. 240
INDEX
351
Conditions disposing to disease,
306
Congenitally word-blind, 220, 221
word-deaf, 220, 221
Conjunctiva, 222
Conjunctivitis, 236
Convergence, 229
Co-ordination, 208
Cornea, 223
Cranial nerves, 203
Cranium, 22
Cretinism, 216
Crura cerebri, functions of, 204
Crystalline lens, 225
Curvature of the spine, angular, 54
lateral, 53
Cytoplasm, 2
Damp-proof course, 261
Darwin, 5
Deafness, causes of, 241, 242
Decomposing foods, 108
Defsecation, 98
Defective children, 214-220
vision, 229
Dendrites, 190
Deodorant, 335
Dennis, 187
Desks, 292-295
and seats, adjustment of, 293
plus, zero, minus, 294
Development of child, 10
Diarrhoea, 325
Digestion, 61-65
Dilator of pupil, 226
Diphtheria, 319
Disabilities and diseases of chil-
dren, 300-328
Disaccharides, 65
Disinfectant, 335
Disinfection, 335
of schoolroom, 336-337
processes of, 335-337
of boiling, 336
of burning, 335
of gaseous disinfectants,
338
of hot-air, 337
of liquid disinfectants,
337
of steam, 337
Dislocations, 340
Divisions of labour, 5
Drainage of school, 266-268
Drains, course of pipes, 268
inspection chambers, 268
testing of, 269
Drowned, treatment of those
apparently, 346-348
Ductless glands, 102
Dura mater, 197
Ear, 237-244
anatomy of, 237-240
bones of, 238, 239
conditions common in school
children, 242
discharging, 242
external, 237, 238
first aids in accidents of, 344
internal, 239, 240
middle, 238, 239
Eczema, 327
Effects of physical training, 55-57
Elbow-joint, 37
Ellison's bricks, 282
Enamel, 71
Endolymph, 240
Energy, definition, various forms, 9
Enzymes, classification of, 68
properties of, 67
Epidermis, 187
Epilepsy, causes, symptoms, treat-
ment, 309, 310
Ethmoid bone, 26
Eutherians, 4
Evaporation, 176
Eye, anatomy of, 222-227
first aid in accidents of, 344
long-sighted, 230, 231
muscles of, 226
short-sighted, 231
Eyeball, 223
Eyesight, testing of, 233
Eyestrain, 229
Excretion, 67
Excretory system, 173-189
External eye diseases, 235-236
Extrinsic muscles of eye, 226
Faeces, 93
Fainting, 344
Fatigue, muscular, 50
Fats, chemistry of, 63
nutritive value of, 106
Favus, 327
Feeding of school-child, 110, 111
Fehling's test, 64
352
HYGIENE
Femur. 34
Ferments, 67
Fibula, 34
First aid in injuries and ailment*.
337-348
Food and nutrition, 105
Foodstuffs, 61
Foot, bones of, 34
joints of, 39
Foramen magnum, 24
Foramina of skull, 24
Foreign bodies in stomach, 344
in throat, 344
Fosse, cranial, 24
Fracture of collar-bone, 339
of lower jaw, 338
of lower limb, 339, 340
of ribs, 338
of skull, 338
of upper limb, 339
Fractures, causes, 337
diagnosis, 338
signs of, 338
simple and compound, 337
treatment, 338
Fructose, 64
Function, relation to structure, 7
( ialactosc, 64
(lames, 60
Gas analysis, 162, 163
Gaseous exchange in lungs, 166
Gasea of the blood, 164, 165
Gastric glands, 82
juice. 82
German measles, 317
Glottis, 245
Glucose, 64
Grand mal, 310
Ground air, 254
movements of, 255
water, 254
(Juliet, function, 78
structure, 77
Gums, 70
Habit*, 174
Haemoglobin, 115
Haemorrhage, 342, 343
Havereian canals, 10, 20
Headaches, 310
Hearing centre, 207
causes of defective, 241
sense of, 237-241
Hearing, tests of, 243
Heart, affections of, 322
anatomy of, 123-130
beat, 138, 139
causation, 141
frequency, 141
diastole of, 139
mode of action, 131
nerve-supply of, 149
sounds, 142
systole of, 139
Heat conduction, 176
convection. 179
loss, 176
production
sensation of, 250
Immunity, acquired, active,
natural, passive, 313, 314
Impetigo, 326
Incus. 239
Infants' department, hygiene of,
MB, 296
Infectious diseases, conditions
essential for their pro-
duction, 314
definition, 311
general characters, 'Ml-
314
means of carriage of virus.
314
means for the prevent inn
of occurrence and spread
in schools, 315
recovery from, 313
source of infection, 314
susceptible person, 314
Innominate bone, 34
Intestine, large, 95
movements of, 98
small, anatomy and histology.
92, 93
changes undergone by
food in, 94, 95
movements of, 98
secretion of, 94
Intrinsic muscles of eyeball. 226
Invertebrates, 3
Iris, 224
Itch, 326
Jaw, lower, 25
upper. 25
Joints, 35-39
INDEX
353
Joints, ball-and-socket, 36
condyloid, 36
definition of, 35
gliding, 36
hinged, 36
imperfect, 35
perfect or movable, 36
pivot, 36
structure of, 35
synovial membrane of, 35
Kidneys, anatomy, 181
histology, 183
blood-supply, 184
Knee-joint, 39
Labyrinth, bony, 239
membranous, 240, 241
Lachrymal bones, 26
Larynx, dissection and structure
of, 244, 245
interior of, 246
muscles of, 245
Lateral curvature of spine, 53
Lavatories, 273
Leucocytes, 117
Ligaments, 35
Light, 221
Lighting, natural and artificial,
of schools, 291
Lips, 70
Liver, anatomy, 99
functions, 101, 102
histology, 99
physiology, 99
Locomotion, 51
Long- sighted eye, 230
Lymph, formation and function,
118-120
Lymphatic glands, 118
Lymphocytes, 117
Lungs, capacity, 161
excretory function, 189
structure, 153
MacKinnell's ventilator, 283
Malaria, 253
Malleus, 239
Malnutrition, signs of, 109
Maltose, 65
Mammalia, different types, 4
distinctive characters, 4
Man, relation to other animals, 3
Man, distinction between anthro-
poid apes, 5
Measles, 316, 317
Medical inspection of schools, 329
aims and objects. 332, 333
Board of Education's
schedule, 331
method, 333
regulations, 331
Medulla, 200
functions, 204
Memorandum on Medical Inspoc-
of Sphools, 329
Mental deficiency, cause of, 2 15,216
conditions associated
with, 215
definition, 214
detection, 216, 217, 218
family history, 216
personal history, 216
physical condition, tests
for, 217, 218
Metatarsal bones, 34
joints, 39
Micro-organisms, action of mois-
ture, 303
action of temperature, 303
conditions of their life, 303
food-supply, 303
general characters, 300, 301
means of resistance to in-
vasion by, 303, 304
mode of production of disease,
302
relation to gaseous environ-
ment, 303
Mid-brain, 201
Monosaccharides, 64
Monotremes, 4
Motor area of brain, 205
Motor-speech centre, 212
Mouth, anatomy, 68, 69
aperture, 69
cavity, 70
hygiens of, 76
physiology of, C3-77
vestibule of, 69
Mumps, 321
Muscle cells, 39, 40
composition, 42
connecting upper limb with
trunk, 44
properties, 41
structure, 41
23
354
HYGIENE
Muscles of eyeball, 226, 227
of head and neck, 43
of lower limb, 47
of trunk, 47
of upper limb, 44
Muscular action, 43
fatigue, 50
system, 39
relation to nervous sys-
tem, 48
work, physiology of, 67-59
Myopia, causes, 231
signs, 232
treatment, 233
Nasal bones, 26
Nerve cells, 190, 191
Nerves, distribution in animals,
192
roots of, 194, 195
structure of, 196
Nervous disorders of childhood,
organic and functional, 303,
309
system and its development,
211, 212
relation to muscular
•iltniii, 48
Neurone, 190, 191
Nose, 151
first aid in accidents to, 345
Nuclear reticulum, 2
Nucleus, 2
Nutrition, 174, 175
Nutritional disorders, 108, 109
Nutritive value of carbohydrates,
106
of fats, 106
of proteins, 107
(Esophagus, 77
Open-air life, advantages of, 170
schools, 297, 298
building, 297, 298
types of school children
to be sent there, 297,
298
results, 299
Open fires, advantages and dis-
advantages of this method of
heating in schools, 287
Optic thalamus, 201
Organ of Corti, 241
Overeating, 108
Overpressure, cause, signs, treat-
ment, 309
Pain, sensation of, 252
Palate, 70
Pancreas, anatomy, 85
composition, action, and
mechanism of its secretion,
86, 87, 89
histology and structure, 86
Parotid gland, 73
Patella, 34
Perilymph, 240
Perilymphatio space, 240
Peristalsis, 78
Personal cleanliness, 173. 174
Petit mal. 310
Pharynx. 77. 152
Physical condition of child and
physical exercises, 69, 60
training, 54-57
Pia mater,197
Poisoning, treatment of, 345, 346
Pons, 201
Postures, 51
Pott's disease, 64
Ptotoim, 61. tt
nutritive value, 107
Pupil, 225
Radius, 33
Reflex action, 210, 211
Regulation of body heat, 175
Relation of seed and soil, 305, 306
of soil and health, 253
Respiration, 150-172
relation to nervous system. 1 67
movements of, 157-160
relation of movements to
circulation, 169
Retina, 225
Rods and cones, 225
Round worms, 328
Running, 51
Saccule, 241
Sacrum, 29
Saliva, composition, 75
function, 76
Salivary glands, 73
Sanitation of school, 253
Scabies, 326
Scalds, 343
Scapula, 31
INDEX
355
Scarlet fever, 317, 318
School buildings, basement, 262
construction, 260-263
entrances, 263
floors, 262
foundations, 260
means taken to prevent
ad vent of moisture, 261
pavilion type, 257
central-hall type, 257
environment, 256
general plan, 256
site, 255
ventilation, 275-286
roofs, 261
staircases, 263
closure, 334, 335
drainage, 266-268
Sclerotic, 223
Secretion, 66
Semicircular canals, 240
Sensation, peripheral, 250-252
Sense, muscular and joint, 252
Sense-organs, 221
Sewer gas, 274
Sherringham valve, 282
Short-sighted eye, 231
Shoulder-blade, 31
Shoulder- joint, 37
Sight, 222-236
Skeleton, 14-34
definition, 14
functions, 14
Skin, 187
affections, 325
first aid in accidents to, 345
functions of, 189
Skull, 22-26
Smallpox, 322
Smell, sense of, 248
causation, 249
end organ, 248
Snellen's test type, 233, 234
Soil, surface and subsoil, 254
and health, 253
made, 255
Song, 247
Sore eyes, 235, 236
Sore throat, 325
Sound, 221
pitch, timbre, loudness, 237
Speech, 244
centres, 212, 213
defects, 248
Speech, organs of, 244-246
production, 247
Spinal cord, functions, 198
grey matter, 198
structure, 197
tracts, 198, 199
white matter, 198
Spleen 104
Sprains, 340
Squint, 235
Stammering, 248
Stapes, 239
Starches, 65
Sternum, 30
Stings, 341
Stomach, absorptions in, 84
activity of glands, 82
anatomy and structure, 79,
80
bloodvessels, 82
movements, 84, 85
nerves of, 82
Stoves, 287
Strabismus, 235
Structure and function, 7
Stuttering, 248
St. Vitus's dance, 307, 308
Stye, 236
Sublingual gland, 74
Submaxillary gland, 73
Sucrose, 65
Sunlight, importance of, 291
Suprarenal capsules, anatomy and
function, 103, 104
Susceptibility to disease, 305, 306
Suspensory ligament of lens, 225
Sweat, composition, 188, 189
glands, 187
Swallowing, 78, 79
Sympathetic system, 209
fibres, 209
ganglia, 209
Tapeworms, 327
Tarsal bones, 34
Taste, 249
qualities detected by, 249
Taste-buds, 249
Temperature of air in schools, 289
sensation of, 252
Tendo Achilles, 47
Tendons, 41
Theory of evolution, bases of, 5
Thorax, 30
356
HYGIENE
Thorax, normal position of, 157
cavity, 155
Threadworms, 328
Thyroid cartilage, 245
gland, anatomy, structure,
and function, 102-103
Tibia, 34
Tissue respiration, 166
To bin's tubes, 281
Tongue, 71
Tooth, crown, 72
dentine, 71
enamel, 71
neck, 72
pulp cavity, 72
root, 72
Touch, sense of, 250
Toxins, 302, 305
Trachea, 152
Treatment of menially defective
children. 21*. 219
backward children. 219
school children, 334
Trommer's test. 64
Trough closet, 272
Tuberculosis, 811
pulmonary, 324
Tuberculous disease of bones, 323
of glands, 323
Typhoid fever, 253
Ulna, 33
Underfeeding. 108
1'n-ter. 186
Urinals, 273
Trine, composition, 179-180
excretion, 178
properties, 179
secretion, 184. 185
Utricle, 241
Vasomotor centre, 147, 148
nerves, 147
Veins, 123, 131, 133
Ventilation, 275
artificial, 284
advantages and disad-
vantages, 285, 286
extraction or vacuum method,
284,285
Ventilation, natural. 278
natural, forces at work
in, 278, 279
openings used in, 280,
282
propulsion or plenum method,
284,285
balance, 285
Ventilating grates. 287
Verminous condition-
Vertebra, structure of, 26
Vertebral oolumi
Vertebrates, 3
Vestibule, bony, 239
membranous, 240
Visual centre, 207
Vitreous humour
Vocal organs, 244
Voice production . :M • i Jl 7
loud ness, 246
quality, 246
Vomer, 26
Walking, 51
Warming of schools, 286-289
Waste matter, 178
Water-closet, 271
Water pollution, various forms.
265
Water-supply 264, 265
constant and intermittent,
264, 265
means of distribution, 265
of storage, 265
Windows. 291
in ventilation, 280
Whooping-cough, 320, 321
Word-blindness. 220
Word-deafness, 220
Word-hearing centre. 213
Word-seeing centre, 213
Work and rest, 8
Worms, intestinal, 327
Wounds, 341
Writing centre, 213
Wrist-joint, 37
Yellow fever, 263
Zero desks, 294
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