title: A new school physiology.
text: ©s I M m A® m. mSw fflp (Si 3f Ss^-^^^^^^^^ >*<»> < «s> < '<v<^>^> □> f LIBRARY OF CONGRESS,! #|hap. f J?%c/f OL°>XS | UNITED STATES OF AMERICA, f ^^^^^^^ A NEW SCHOOL PHYSIOLOGY. BY RICHARD J. DUNGLISON, A.M., M.D., Author of "The Practitioner's Reference Book," Editor of Dunglison's "Medical Dictionary," "History of Medi- cine," Secretary of the American Academy of Medicine, etc., etc. ILLUSTRATED WITH ONE HUNDRED AND SEVENTEEN ENGRA VINGS. IA% PORTER & COATES PHILADELPHIA. Copyright, PORTER & COATES 1880. PREFACE It has been the aim of the author in the following pages to impart such information on the interesting subject of Physiology as will make the reader familiar with the gen- eral structure of his own body. To young people this knowledge is especially important and desirable. They have the opportunity to be practically benefited by such instruction at a sufficiently early period in life to enable them to be watchful in regard to the laws of health, which they must necessarily study in connection with Physiology, Experience as a physician fully justifies the author in the statement that it is in ignorance of such laws, and in con- sequence of the lack of proper education in this useful branch, that so many adults are daily violating the sim- plest principles of health. No more important subject can be taught in the schools than that which instructs the student in the principles of his own formation. In the frequent allusion made throughout this work to Compar- ative Anatomy and Physiology — the anatomy and phys- iology of other animals compared with man — the reader 4 PREFACE. will be able to appreciate the lofty position occupied by him in the scale of creation. The knowledge which will thus be acquired by him of the higher state of development characteristic of man, and of the possibilities of still greater perfection of his intellectual and physical powers under proper education and training, will be one of the most valuable and improving lessons which Physiology can teach. RICHARD J. DUNGLISON, M. D. CONTENTS. INTRODUCTORY. PAGE Physiology and Anatomy Defined 10 Aids to Physiology 11 Organized and Inorganic Bodies 12 Physiology of Animals and Vegetables 14 Cells 19 Divisions of the Human Body 21 THE BONES, JOINTS, AND MUSCLES. The Bones 27 Structure of Bones 28 The Spinal Column 29 The Limbs 32 The Joints 34 The Muscles 36 Tendons 38 Movements 41 DIGESTION. Digestion in the Vegetable 49 Food of Man 50 Ingredients of Food 52 Classification of Food 53 Oils and Fats 54 Sugar and Starch 55 Gum; Albuminous Substances 56 Animal Food 58 Milk 60 Eggs; Vegetable Food ; Bread 62 Cooking 64 Drinks 65 Conditions Necessary for a Healthy Diet 71 Appetite and Hunger 72 Thirst 74 Apparatus for Digestion 74 1* 5 6 CONTENTS. PAGE The Teeth 76 The Tongue 80 The Salivary Glands 80 Deglutition 82 Processes of Digestion 84 Digestion in the Stomach and Intestines 86 Stomachs of Other Animals 91 Changes in the Food in Digestion 96 Digestibility of Food 9S Digestion in the Intestines 101 Intestinal Juices 10-4 ABSORPTION. Various Forms of Absorption 120 Intestinal Absorption • 121 Lymphatics 12-1 RESPIRATION. Objects; Changes Produced 128 The Chest and its Contents 130 The Lungs 131 The Act of Breathing 134 Sounds of the Chest 136 Capacity of the Lungs; The Air-Cells 137 The Air we Breathe 138 Ventilation.. 141 Respiration in Animals Generally 142 Respiration in the Vegetable 144 CIRCULATION. The Heart 148 The Greater and Lesser Circulation 151 Valves of the Heart 152 Sounds of the Heart 155 The Pulse 156 The Quantity of Blood : The Arteries 158 Pulse-Writing; The Veins 160 The Capillaries : Velocity of the Circulation 162 Infusion and Transfusion 163 Circulation in Other Animals 164 The Blood 167 White Corpuscles 171 Coagulation of the Blood 172 CONTENTS. 7 ANIMAL HEAT. PAGE Temperature of Animals 179 Effect of Food, etc. ; Temperature of Organs ISO Atmospheric Influences, Clothing, etc 181 SECRETION. Materials Separated from the Blood 184 Glands; Secreting Surfaces 185 THE NERVOUS SYSTEM. Divisions of the Nervous System , 190 Cerebro-Spinal System 192 The Brain 193 Brains of Different Races; Facial Angle 196 Cerebellum; Spinal Cord 199 TheNerves 200 Great Sympathetic Nerve 20S Functions of the Nervous System 210 Functions of the Nerves 211 Reflex Action of the Spinal Cord 212 Functions of the Medulla Oblongata 214 Functions of the Cerebellum 215 Functions of the Cerebrum 216 Phrenology; Sleep ." 218 Nervous System of Animals 221 THE SENSES. Their Objects, etc 231 Taste The Organ of Taste 233 Nerves of the Tongue 237 Organ of Taste in Other Animals : 238 Smell. The Organ of Smell 240 Odors.. 242 Sense of Smell in Animals 244 Touch. The Organ of Touch 247 The Skin 248 The Papillae 249 Sweat-Glands 250 8 CONTENTS. PAGE Sebaceous Glands 251 Hair 252 Color of the Skin 253 Sense of Touch in Animals 256 Vision. The Sense of Vision 258 The Organ of Vision ; Protection of the Eye 259 The Tears 260. The Orbits; The Eyelids 26] The Eyelashes; Transparent Parts of the Eye 262 Coverings of the Eye 264 Motions of the Eyeball 266 Light 267 Image on the Retina 270 Accommodation of the Eye to Distance 271 Perception of Colors 275 Vision in the Inferior Animals 276 Hearing. The Apparatus of Hearing 282 External Ear; Middle Ear 283 Internal Ear 283 Functions of the External Ear.. 285 Functions of the Middle Ear 286 Functions of the Internal Ear 287 Sound 288 The Sense of Hearing in Other Animals 289 VOICE. The Organ of Voice 293 The Larynx 293 The Vocal Cords 294 Muscles of the Larynx 295 Production of Voice 296 The Singing and the Speaking Voice 299 The Formation of Language 300 Vocal Apparatus of Animals 303 PHYSIOLOGY It was formerly the custom to divide all bodies into the three classes. Animals, Vegetables, and Minerals, and this mode of division is still adopted by some writers. Animals and vegetables resemble each other, however, in so many respects, especially in the possession of organs, that it has seemed desirable to make a different classification. The division now generally adopted is into organized bodies and inorganic, the organized being composed of organs for the performance of certain duties, while no such ar- rangement exists in the inorganic. Animals and vege- tables, being made up of organs, belong to the class of organized bodies ; minerals are inorganic. Physiology proper. — Physiology is that branch of science which treats of the healthy exercise of the various organs of the body. It is derived from two Greek words denoting the doctrine of nature. Vegetable Physiology examines the properties of vegetables only, in all that concerns their life and nourishment. When the term Physiology is used alone, it is generally understood as restricted to man and animals. It is called Human Physiology when applied to man alone ; it is known as Comparative Physiology when applied to animals generally as compared with man. The chief subject of our inquiry will, of course, be the physiology of man, but allusion will frequently be made to comparative physiology, so that the place occupied by man 10 PHYSIOLOGY. in the scale of animals may be thoroughly understood. In whatever department we study physiology, we cannot fail to be struck with the vastness of its scope, for it embraces a knowledge of the progress and decay of all forms of vegetable and animal life, from brute matter, which is devoid of vitality, to the most perfect animal — man him- self — who possesses it in the highest vigor. Anatomy. — Anatomy is a distinct branch of inquiry, and is derived from a Greek word meaning dissection, but as generally used signifies that study by which, through the medium of dissection, we become acquainted with the struc- ture of the several parts that enter into the composition of the bodies of animals. It is really necessary, as a general rule, to understand the structure of the various organs of the body — that is, their anatomy — before we can fully appre- ciate their physiology. We can sometimes infer from the anatomy of a part what are its uses, but some of the organs, such as the brain, giye us but little information. We know that there can be no exercise of intellect without a brain, and yet when we come to examine that important organ we learn absolutely nothing from its structure. It is appar- ently only a mass of fat, phosphorus and other chemical materials arranged in a peculiar way and protected from injury in a bony covering. This is all we learn from its anatomy or chemistry, although it is an organ capable of the highest duties and has many important organs under its control. An- atomically, the eye is a perfect organ and the structure of the tongue is very familiar to us, yet the nicest dis- sector has failed to show us how the eye possesses the power of giving us our ideas of external objects or the tongue can impart to us the hundreds of varied flavors. Comparative Anatomy is the study of the structure of PHYSIOLOGY. 1 1 other animals than man as compared with him. When we see differences in the arrangement of their organs we know that there must be some different duty performed, and thus we may acquire a knowledge of their physiology. For instance, we see a variation in the anatomical arrange- ment of the stomachs of animals, and this we find occurs in accordance with a variation in the kind of food they live upon and the amount of digestion required. Aids to Physiology. — Even disease or malformation may aid us in learning physiology. Cases have occurred where life was carried on for a while without any brain, the child breathing and swallowing just as well without it, although it would not, of course, exhibit any mental power. This shows that the acts of respiration and of swallowing are not controlled by the brain, and so by the absence of an anatomical part we derive information negatively as to its duties. The laws of Physics are also involved in the study of physiology. Sight or vision is an example of this, the eye being mainly a physical apparatus, a transparent body influenced by the laws of light. If the physical part be imperfect, vision is defective. So, too, the muscles are a physical apparatus, acting like levers of different kinds according to the angle or mode in which they are inserted into the bones. As we shall see hereafter, the arrangement of the ear for hearing is partly a physical apparatus. Chemistry also aids us in the study of physiology. Digestion, for example, is mainly a chemical process, the juices in the stomach and small intestines which effect it being made up chiefly of acids and a ferment. The fluids in the mouth which act on the food in that cavity produce their effect by chemical action. Respiration or breathing is also a chemical and mechanical process, being an ex- 12 PHYSIOLOGY. change of gases into and out of the lungs, oxygen being received into those organs, and carbonic acid being given off. These functions or processes are also, to some extent, affected or regulated by a nervous system. There are many functions that are performed wholly or in part in a me- chanical or chemical manner, and their action is easily understood ; yet the controlling power — the vital action — is wholly beyond our calculation. The healthy action of the heart, for instance, is dependent on the movement of its own muscles and of valves in its interior, which act in a purely mechanical manner; and yet we cannot explain minutely why such action is carried on through life and sometimes by artificial stimulation after death. Vie say it is a power existing within itself, under proper control, and there our explanation ends. Differences between Organized and Inorganic Bodies. — Inorganic bodies, such as minerals, are not born, as animals are ; they do not possess life, and have not a certain definite shape like animals and vegetables. In each of these last — the animal as well as the vegetable — there are a particular form and recognized size, which belong to that kind and to every part of it. Vegetables, for instance, have a certain relation of size and shape of their stems and roots and limbs ; and animals have their bodies and all their parts framed on one general and uniform plan. The animal and vegetable are constantly undergoing change, while the mineral is at rest. As long as life lasts the organized body is never in perfect repose; it is continually receiving food in some shape or other with which to support life, or car- rying on the circulation of blood or of some other fluid necessary to its existence, or performing some other duty assigned to its various organs. In the animal and vege- table the different parts have a certain dependence upon PHYSIOLOGY. 1 3 each other, and no portion can be detached from another without inflicting injury upon the whole body ; but large pieces can be broken from a mineral, and its shape entirely changed by force applied to it, without any such sympathy on the part of the rest of the body. When we examine the structure of these different classes of bodies we find a great variation, for, as already stated, animals and vege- tables have a regular uniform arrangement, and certain parts which serve as organs. These are known by definite names : in the vegetable, for instance, they are the roots, leaves, flowers, bark, etc. ; in the animal, the nerves, muscles, blood-vessels, etc. In a mineral or inorganic sub- stance the structure is alike throughout. In the animal or vegetable, as we shall hereafter see, the particles are arranged in the form of fibres which run in all directions through and across one another to form a tissue, through which the different organs are made up. Organic bodies pass through a series of changes, which in the animal particularly are known as ages, during which the organs become developed, attain their full growth, and then decay. The condition of the inorganic body is very different ; it only changes its color or its shape when affected by the influence of blows or external agents, as rain, etc. A stone may increase in size by the addition of earthy or other matter to its surface, but it never grows in the same sense that animals and vegetables are said to grow. So, too, with regard to the death of either of these organized bodies ; they generally cease to have life as the result of some cause operating from within, as when a vital organ — the heart or lungs, for example — becomes diseased and unable to carry on its duties. The inorganic body has no death ; it may be broken to atoms by force, 2 • 14 PHYSIOLOGY. or it may crumble into dust, but there is no cessation of life here, for actual life never existed. Some of the lower forms of animals and vegetables may exist but a short time, while man may sometimes live a century ; but this short or long duration of life is controlled by the interior organization of the animal and by external causes operating upon it. AVhen the organs of the animal perform the work assigned to them properly and in full vigor, they are said to be healthy, and the general condition is said to be one of health. The reverse of this, when the action of the organs is interfered with from any cause, is called disease. The term hygiene has been applied to that branch of study which includes all the different methods, medical or other- wise, devised for the preservation of health ; for Hygeia, in the ancient mythology, was the goddess of health. Differences between Animals and Vegetables. — It is not so easy to draw the line here as it was between these two classes of organized bodies and the inorganic. Both ani- mals and vegetables require nourishment, and hence we say that nutrition is a function or performance common to both. But animals have a sense of feeling — sensation — which vegetables do not have, and they also have the power of moving at their own pleasure, and this is called voluntary motion. Under this action of the will they are able to move any part of the body as they may wish, or to go from place to place in any direction they may desire. Some of the lowest forms of animal life seem little higher in the scale than the vegetables they resemble, but the physiologist has certain laws by which he is able to distin- guish them. As a general rule, vegetables contain more solids than fluids ; in the animal, as man, although exter- nally, to the ordinary observer, largely solid, the fluids PHYSIOLOGY. 15 contained in the various tissues and organs of the body are greatly in excess. In the vegetable there is but one ele- mentary tissue observable in its structure, a tissue made up of areolae,, or spaces, and hence called areolar tissue. The animal possesses this, and in addition other primary tissues, such as the muscular and nervous tissues, all of which will be described hereafter. The vegetable, having no powers of sensation or feeling, or voluntary motion, does not re- quire a brain or nervous system, or even muscles which either a brain or nervous system can control. When we say that animals and vegetables present these general differences in their structure, we must not forget that in the lowest forms of animal and vegetable life such distinctions are not perceptible. Some vegetables of this kind contain more fluids than solids, and in some of the minute animals there is a total absence of muscles and nerves, and even of organs, as heart, lungs, or stomach, and of vessels to convey the fluids from one part of the body to another. When flowers open or close they do so under the influence of light or air, or of some other cause not requiring a brain or nervous system to produce it. In the " sensitive plant/ 7 as it is called, the leaves collapse under the slightest touch, but this is merely a power of contraction not dependent v>n a nervous system. Nutrition of Animals and Vegetables. — So far as nutrition is concerned in animals and vegetables, there is observable a marked difference. The source of supply of food to the vegetable is the earth which surrounds it and in which it is firmly fixed. The food thus offered it does not require preparation ; it is ready for use, and it is at once absorbed by the vegetable. Whatever the animal needs to sustain it must be taken into the stomach and digested, as it is called, or prepared for absorption for its nourishment. In 16 PHYSIOLOGY. both animals and vegetables absorption of the food is necessary before it can be of any service in maintaining life ; but the higher classes of animals also have the power of seizing upon their food, of moving to obtain it, and, as already stated, a will to govern them in their movements. Chemical Composition. — As a rule, vegetables are mainly composed of the three chemical substances, oxygen, hydro- gen, and carbon ; animals have all these, and nitrogen in addition, a fact which may be shown as follows : Animal. f Oxygen, Vegetable ' Hydrogen, { Carbon, Nitrogen, This is not wholly true of either animals or vegetables, for the green parts of vegetables are made up of the four elements, and the fatty parts of animals of the three ele- ments only. This explains why in cases of excess of fat in individuals animal food is given as a means to reduce it, rather than starchy matter or sugar, which are made up of the three elements, for these last would only increase the evil which it is attempted to remedy. In addition to the four elements just mentioned, many others are found in the animal tissues. Some of the prin- cipal of these may be conveniently arranged in a table, which gives at a glance the particular parts of the body in which they have been detected. It will be observed that the most important of these are found in all the tissues and liquids, while others have a special location : Name. Where Found. Hydrogen In every tissue and fluid. Carbon In every tissue and fluid. Nitrogen In many of the tissues; in solution in fluids. Oxygen In all the tissues; in solution in fluids. PHYSIOLOGY. 17 Name. Where Found. Sulphur Albuminous substances ; blood; secretions; serum of the tissues.* Phosphorus.. ..Blood; nervous matter ; bone; teeth; fluids. Chlorine Tn every tissue and fluid. Sodium Blood ; all the secretions; serum of the tissues. Potassium Muscles; red blood-corpuscles; nervous matter; secretions. Calcium Bones and teeth ; fluids. Magnesium. ...Bones and teeth; fluids. Lithium Muscles; blood; milk. Iron Coloring -matter of the blood; bile; chyle; lymph; sweat, etc. These simple chemical elements are combined to form other bodies or materials of which the various animal tex- tures are composed. Water is one of the most important of these. The chemical composition of a living being varies in quality and quantity at different periods of its growth. The seed, for example, differs chemically from the plant ; the egg from the grown animal. The quantity of water gradually diminishes also as life advances. It usually forms about two-thirds of the weight of the body. In a person weighing one hundred and fifty pounds there are about one hundred pounds of water. It is distributed through the body in the most important organs as follows, in each 1000 parts : Tissues or Organs. Water. Solid Parts. Enamel of the teeth 2 998 Bone 220 780 Fat 299 701 Cartilage 550 450 Liver 693 307 Spinal cord 697 303 Skin 720 280 Brain 750 250 * By secretions are usually meant fluids separated from the blood, as the sweat, the tears, etc. ; by the serum of the tissues, the thin watery portions that bathe their surfaces like a moisture. 2* B 18 PHYSIOLOGY. Tissues or Organs. Water. Solid Parts. Muscles 757 243 Blood 791 209 Bile 864 136 Milk 891 109 Chyle 928 72 Gastric juice 973 27 Tears 982 18 Saliva 995 5 There are also in various parts of the body, as in the gastric juice, bones, muscles, blood, bile, etc., acids, such as muriatic, sulphuric, phosphoric, lactic, carbonic, and other acids ; alkaline substances, such as soda, potassa, magnesia, and lime ; salts of various kinds, such as phosphate of lime, chloride of sodium, or common salt, etc. ; sugars, such as sugar of milk ; fats, as in the oily part of milk ; coloring- matters, as in the blood and bile ; and albuminous matters, which we shall hereafter find to be present in the blood, milk, brain, muscles, and other important solids and liquids. The white of egg is the best example of albumen, and like albuminous substances in the various parts of the body is coagulable by heat, a fact familiar to all in the appearance of the egg when boiled. Vegetable albumen is the name given to it when found in the juices of plants. In milk it is called casein e ; while in peas, beans, etc., and in the grains of similar plants, it is called legumine. The albuminous body formed during the coagulation of lymph and blood is called ftbrine. In the red globules or cor- puscles of the blood there is an albuminous body called globuline ; and when the albuminous matters in the stomach are acted upon by the gastric juice, a substance called peptone results. In addition to all these and other substances in the bodies of animals, certain airs or gases are found. The PHYSIOLOGY. 19 air that passes into the lungs when we breathe is mainly composed of oxygen and nitrogen. From food and drink taken into the stomach we derive such gaseous matters as are found in that organ or in the intestines. The principal gas given off from the lungs is carbonic acid, which comes from the breaking down of the tissues, and has its outlet from the system chiefly at that point. Cells. — All the tissues and organs of the body originate from a minute form called a cell, which divides into other cells, and these, by uniting together, are developed into tissues. Organs are made up by a combination of tissues. Several organs grouped together form a system or appa- ratus. In the apparatus of digestion, for example, there are several organs, such as the stomach, intestines, etc., which are made up of different kinds of tissues. The cells are small vesicles, only visible under the micro- scope, composed of a very thin membrane called a cell-waff, and contain a semi-fluid matter, in which is frequently imbedded a minute oval body called the nu'cleus, itself containing sometimes an even smaller body, the nucleolus. So that we may correctly say that the nucleolus is the very lowest form in which a tissue is capable of being expressed. To give an idea of the size of the cells, it may be stated that some of the smallest of them are so very minute that 12,000 of them placed together would only occupy the space of an inch. They are of course only visible under the microscope. Fluids pass through the walls of these cells so readily that the latter may swell when brought into contact with thin fluids, while they may shrivel up if their own contents pass out into a thicker fluid around them. Where Nutrition is Effected. — It is in these cells that the nutrition of the body is effected. They are found in 20 PHYSIOLOGY. the vegetable as well as in the animal. The cell receives certain materials from the surrounding medium, and con- verts them into its own substance or makes use of them for nutritive purposes. Certain cells have a power of selection by which special kinds of material are formed. Some cells, for instance, form coloring matter, some fatty matter, etc. They make this selection or choice as per- fectly as if they had a mind of their own to control them. The cells are endowed with special qualities by which they perform certain actions when stimulated. Thus a cell of a muscle contracts when it is stimulated ; the cell of a gland pours out, or secretes, as it is called, a fluid, — that of the perspiration or the tears, for example; and a nerve-cell takes on itself an action which results in sensation or intel- lectual power or exercise of the will. Each cell has a life of its own separate from all those which surround it ; but the life of the whole body is made up of the lives of all the cells which compose it. Some cells die after a few hours ; others may exist for years. The cells on the sur- face of the body, for example, are being constantly re- moved and renewed, while those of cartilages, structures which have not much vitality, may endure for a long time. The importance of cell-agency in the nutrition of . the various organs must not be under-estimated because these bodies are microscopic. Some of the important cells of the body, as the nerve- cells, blood-cells, or corpuscles, etc., will be alluded to hereafter when we come to describe the nervous system, the circulation of the blood, etc. The solid fat of the body is contained in separate cells with delicate walls, called fat-cells or adipose-cells. They are globular in shape, but become many-sided when pressed together, and, although usually larger, are often as small as the -g-oVo^h PHYSIOLOGY. 21 of an inch in diameter. Some cells, known as pigment- cells, contain a coloring-matter in their interior, and are found in certain parts of the eye and on the skin. They are concerned in producing the different colors of the races of mankind, and in the eye they have the effect of assist- ing in absorbing the rays of light, like the dark parts of the interior of a telescope. Divisions of the Human Body. — When we study the human body in its various parts and structures, we find it made up of a number and variety of organs. The frame- work is the skeleton (Fig. 1), which is composed of more than two hundred bones. The skeleton has at its upper part the skull (Fig. 2), which is itself a collection of bones of all sizes, fitted accurately together, containing in its interior the various portions of the brain. Continuing downward from the skull, which is carefully poised upon it, is the spinal or vertebral column, or spine, which is a series of bones, in the interior of which is the spinal marrow. At the lower part of the spinal column, on each side, are large expanded bones, called the pelvic bones or pelvis, from their resemblance to a basin, as their Greek derivation implies. The sides of the pelvis form the hips. The framework of the upper and lower limbs is also bony, being composed of bones of various sizes adapted to the useful movements of those parts. These bones, which make up the skeleton, are covered with muscles, which give motion to the various portions of the body. Em- braced within these various walls formed by bones and muscles are the important cavities of the body — the head, chest, and abdomen — in which the organs concerned in sensation, respiration, circulation, digestion, etc., are placed. In the skull is the brain, and in the face, which is the front portion of the skull, are the organs of sight, smell, Skull Spinal column Collar-bone. — , Shoulder-blade. — , Breast-bone Ribs False ribs Vertebral column Pelvis Sacrum End of spin Radius. Bones of - ankle ' and foot. PHYSIOLOGY. 23 taste, and hearing. In the chest, or thorax, as it is called, are the heart and kings ; in the abdomen are the digestive organs, in which the food is acted upon and absorbed for the use of the system. In addition to the bones and muscles and the important organs just referred to, there are numerous bloodvessels, Fig. 2. — Bones of the Skull. conveying blood from the heart, to all parts of the body, and back again to the heart, and called arteries and veins ; and also a set of vessels in every region, called lymphatics, which convey a thin fluid, called lymph, to be mixed with the blood. Delicate cords, called nerves, greatly varying in size, pass everywhere throughout the system, like tele- graph-wires, keeping up a communication between the brain, spinal cord, and every portion of the body. Cover- ing the whole mass of muscles, bones, vessels, and nerves is the skin, the sensitive envelope which protects and shields the whole bodv from external irritants. 24 PHYSIOLOGY. QUESTIONS. Inter what three classes have bodies been divided? In what respect do two of these classes resemble one another? What are organized bodies? Inorganic? To which class do animals belong? Vegetables? Minerals? How do you define Physiology ? What is its derivation? What is Vegetable Physiology ? When the word Physiology is used alone, to what does it apply? What is Human Physiology? What is Comparative Physiology? What does the study of Physiology embrace? What is Anatomy? What relation does Anatomy bear to Physiology? What information does the anatomy of the brain give us? What is its chemical constitution? What do we learn of physiology from the anatomy of the eye or tongue ? What is Comparative Anatomy? What assistance does this give in learning physiology? Take the stomach as an example. What may we learn from disease or the absence of an organ ? Of the brain, for example? What examples of physical apparatus have we in the body? What process is chiefly chemical? What part does chemistry take in it? In what respect is respiration a chemical process? What action has a nervous system in such processes? What is the healthy action of the heart dependent upon ? How do we explain this continuous action of the heart? How do inorganic bodies differ from animals in regard to life, size, shape, etc.? Why is change necessary to the life of organized bodies ? What evidences of sympathy or dependence of different parts have we in animals and vegetables? How does this differ from the mineral or inorganic substance? What are the various organs called in the vegetable? in the animal ? How are tissues made up in the vegetable or animal ? What is meant by the different ages in animal life? PHYSIOLOGY. Which of those named are found in all the tissues and fluids? Select from the table those other elements which are found in the blood. In the nervous system. In muscles. In the bones and teeth. What special element is found in the coloring-matter of the blood ? What do we mean by secretions? By the serum of the tissues? What proportion of the weight of the animal body is fluid? How much water is there in a person weighing one hundred and fifty pounds ? What parts of the body are shown by the table to contain more solids than fluids ? Mention a few important fluids that are very largely made up of water. 3 26 PHYSIOLOGY. What acids are found in various parts of the body? What alkaline substances? What salts? What other chemical substances? In what parts of the body are albuminous matters present? What effect has heat upon albumen? What name is given to this substance as found in the juices of plants? In milk and beans what names are given to it? What is fibrine? What is the albuminous body in the coloring-matter of the blood called ? In the stomach as the effect of digestion ? How are oxygen and nitrogen taken into the system? What is the principal gas given off' through the lungs? From what minute form are tissues and organs developed? How do organs differ from tissues? What is a system or apparatus? What is included in the apparatus of digestion ? What are cells composed of? What is a nucleus? A nucleolus? What is the lowest expression of a tissue? What is the size of the cells? Where and how does nutrition take place? What power of selection do cells possess? What action takes place when a muscular cell is stimulated? A gland-cell? A nerve-cell? How long is the life of a cell? What is the arrangement of the fat-cells? What are pigment-cells, and where do they exist? What effect have they on the skin or the eye? What is the bony framework of the body called? How many bones compose it? What is the skull, and what does it contain ? What is the vertebral column? What does it contain? What are the pelvic bones? How are the bones covered ? What organs are contained in the front part of the skull ? In the chest? In the abdomen? What organs are concerned in conveying blood to all parts of the body ? What are the lymphatics? What organs maintain the communication between different parts of the body ? What general office does the skin perform ? THE BONES, JOINTS, AND MUSCLES. The Bones. — The general shape and solid form of the body depend upon the bones. These act not only as a framework for support, but also as a protection to the deli- cate organs which they enclose. Some very important organs of the senses are thus protected, as the eye and ear, within the bony structures surrounding them. The brain itself is completely sheltered from ordinary injuries by the skull, which, as a bony, air-tight case, covers it at every point. The heart and lungs are also similarly protected by the bony and muscular walls of the chest. The bones are also useful as offering surfaces on which the muscles are inserted, for on the bones and muscles thus acting on each other depend the movements of the body. The important part of the nervous system included in the spinal cord is protected by the spine, or spinal column, which is a long collection of bones extending the whole length of the back. The bones are of a great variety of shapes : some of them, as those of the hands, are quite small ; others, as of the arms and legs, large and capable of numerous move- ments. Bone consists of an earthy and an animal part resembling gelatin. The earthy part is chiefly phosphate of lime, and when bone is acted on by heat and acids this is destroyed, and the bone becomes so flexible that it can be tied into a knot. This is like restoring it to the con- dition it was in when it was first formed, for it was gelat- 27 28 PHYSIOLOGY. inous before it became encrusted with earthy matter. The animal part of the bone imparts to it elasticity and renders it tough, while the earthy portion gives it rigidity. The earthy matter is in excess in old persons, hence the bones are more liable to break at that period of life. Cartilage. — Bony matter exists at first in a kind of pre- paratory condition called cartilage, the cells of which be- come replaced by bony cells, which give to bones their particular consistence. Some portions of the body, as parts of the ribs, remain during the Avhole period of life in this state of cartilage. Where the bones come together to form a joint, as in the elbow or knee, the surfaces are in this very condition. In the skull, made up of a number of bones of different shapes and sizes, no such arrangement is necessary. Almost all the bones here fit into one another by their opposite edges being bevelled and grooved, so that they can be accurately adjusted (Fig. 1. The bones are here shown as if widely separated, so that their edges may be more plainly seen). The bones of the skull proper are not movable, the joints being more like seams, and hence called sutures. The lower jaw is the only part that is movable, but it is connected with the skull in a different manner from that seen in the other bones. Division of Bones. — Bones are generally divided into long, short, and flat bones. The thigh, for instance, is a long bone; those of the skull are flat. Tin's is a good division so far as the bones of man are concerned, but not of other animals as compared with man, for the same bones that we might call long or flat in the one might be of very different shape in the other. Some small bones are called long, because their structure internally is like that of long bones. Structure of Bones. — If we examine the interior of a THE BONES, JOINTS, AND MUSCLES. 29 long bone by sawing through it lengthwise, we are able to understand how both strength and lightness are imparted to it. It will be seen that it is not solid throughout, as might ap- pear from an external view of it ; but it is divided into two distinct portions (Fig. 3) — a hard part, which is also porous and honey- comb-like at the extremities of the bones, and a spongy portion, containing in its centre a substance called the marrow. When we ex- amine the structure of bone under the microscope, we notice an ap- pearance similar to that presented in Fig. 4, the bony mass being hollowed out by an immense num- ber of small canals, called the canals of Havei's, after the anat- omist who first described them. Through these canals pass the bloodvessels which nourish the bone and the marrow contained in it. The bony canal is a sort of star-shaped cell, as seen in the section represented (Fig. 4). The Spinal Column. — This, gene- rally known as the backbone, is some- times also called the ver'tebral column, each piece forming it being called a ver'tebra. (The general arrangement will be seen by reference to Fig. 5.) The various spines, or projections, give it the name of the spinal column, by which it is generally known. These are readily felt by the hand along the 2* ^^»J^S^PH 1 ■JR 1* Wm H HB ■ Piiliiiii Fig. 3. — Interior of a Bone. Fig. 4, *11 Section of Bone;. 30 PHYSIOLOGY. am a Vertebrae of the neck. Vertebrae of the back. middle of the back. There are twenty-six bones in the chain, smaller at the top of the column, and larger as it ^.„„ D ^ descends. It is the back- bone or groundwork which acts as a basis of support to the chest and abdomen (Fig. 6). A canal, called the ver- tebral or spinal canal, passes through the interior of the spinal column, and contains the spinal cord, which is one of the great nervous centres. Between the bones com- posing the spine are layers of elastic tissue, which give to the whole column a slight degree of flexibility and elasticity without imparting much power of movement to it. The useful effect of this elastic tissue or cartilage placed between the harder texture of the bones is also to diminish the force of blows and injuries inflicted upon the spine. Were this not present, the force of the slightest falls or jumps would be felt by the deli- cate brain as transmitted along the solid bony mass of the spinal column. The effect may be illustrated by a simple and well-known experiment. If a number of solid - Vertebra; of the loins. Fig. 5. — Spinal Column. 