LIBRARY 
 
 01- THK 
 
 UNIVERSITY OF CALIFORNIA. 
 
 T OK 
 
 Deceived o~ lc )? 
 
 Accessions No. ^ y J ~ j . CA/ss TVo . 
 
801 
 
 ; ' 
 
FIRST. LESSONS 
 
 IN 
 
 PHYSIOLOGY: 
 
 FOR USE IN THE COMMON SCHOOLS. 
 
 BY, 
 
 C. L. HOTZE, * 
 
 AUTHOR OF " FIRST LESSONS IN PHYSICS." 
 
 SAINT LOUIS: 
 
 THE CENTRAL PUBLISHING COMPANY 
 
 LBE, SHEPARD & BILLINQHAM, New York. 
 
 J. L. HAMMETT, Boston. 
 
/ 
 
 BIOLOGY 
 LIBRARY 
 
 G/ 
 
 Entered according to Act of Congress, in the year 1874, by the 
 
 CENTRAL PUBLISHING COMPANY, 
 In the Office of the Librarian of Congress, at Washington. 
 
 
1 
 
 PREFACE. 
 
 The propriety of teaching some of the sciences in 
 our common schools is so well established as to 
 require no further arguments. Nor does it seem 
 necessary here to justify the claims of physiologi- 
 cal science; educators, and the people generally, 
 are agreed that a knowledge of " the machine which 
 we run and which runs us " is of the utmost import- 
 ance. The question now under discussion is, how 
 much of Physiology can be taught in the upper 
 grades of the common school without infringing 
 upon the other studies ? 
 
 To facilitate the solution of this problem, as well 
 as to meet the wishes expressed on many sides to 
 see the essentials of Elementary Physiology ar- 
 ranged after the manner of the author's " First 
 Lessons in Physics," the present volume has been 
 prepared. It comprises thirty-nine lessons on the 
 structure and functions of the human body, the 
 subject-matter being treated with reference to the 
 wants of the young people in the classes, alluded to. 
 
PREFACE. 
 
 These lessons profess to present the amount of 
 physiological science which should be taught in the 
 common schools. They include the essentials of 
 hygiene, which are treated in immediate connection 
 with the function of the organ to which they refer. 
 Many technical terms, and all " rules " of hygiene 
 based on mere assumption or personal bias, to- 
 gether with a host of trivialities frequently met with 
 in works of the kind, have been excluded. For 
 while the teacher under favorable circumstances can 
 easily go beyond the limits of the text, it is an 
 objectionable feature in a school book if, after its 
 purchase, pupils are obliged to skim, or omit, any 
 part of it. 
 
 Portions of recently slain animals should be used 
 for demonstration, and the young learner be con- 
 stantly urged to observe for himself. 
 
 I am indebted to the works of Bennett, Dalton, 
 Flint, Huxley, Kirkes, and others ; and take great 
 pleasure in thanking Dr. Weber of this city for his 
 kindness in examining the manuscript of this book. 
 
 WEST HIGH SCHOOL, 
 Cleveland, Ohio, January ist, 1875. 
 
CONTENTS. 
 
 LESSON I. PAGE. 
 Organic and Inorganic Matter. Animal Structure - 9 
 
 LESSON II. 
 The Skeleton 13 
 
 LESSON III. 
 The Head. Cerebro- Spinal Axis. Teeth 17 
 
 LESSON IV. 
 Review 22 
 
 LESSON V. 
 The Trunk 24 
 
 LESSON VI. 
 The Limbs. Ligaments 27 
 
 LESSON VII. 
 Cartilages. The Larynx 30 
 
 LESSON VIII. 
 Review 33 
 
 LESSON IX. 
 Muscles. Fat 35 
 
 LESSON X. 
 Muscles as Motor Agents. Walking 38 
 
 LESSON XL 
 Muscles, continued. Work of Muscles 42 
 
 LESSON XII. 
 Review , 48 
 
 LESSON XIII. 
 The Skin. Hair and Nails. Excretion of Skin 51 
 
 LESSON XIV. 
 The Blood 54 
 
 LESSON XV. 
 Circulation of Blood I 58 
 
 LESSON XVI. 
 Circulation of Blood II 62 
 
 LESSON XVII. 
 Review 69 
 
 LESSON XVIII. 
 The Lungs __ . 74 
 
 LESSON XIX.. 
 Respiration 79 
 
 1 
 
6 CONTENTS. 
 
 LESSON XX. PAGE. 
 Review 84 
 
 LESSON XXI. 
 Air and its Relation to the Human Body. 1 87 
 
 LESSON XXII. 
 Air and its Relation to the Human Body. II 92 
 
 LESSON XXIII. 
 Review 98 
 
 LESSON XXIV. 
 Food 101 
 
 LESSON XXV. 
 Digestion. I 106 
 
 LESSON XXVI. 
 Digestion. II. (Stomach) no 
 
 LESSON XXVII. 
 Digestion. Ill (Intestines) .' 113 
 
 LESSON XXVIII. 
 Assimilation 119 
 
 LESSON XXIX. 
 Review 126 
 
 LESSON XXX. 
 Nervous System. I. Different Parts 130 
 
 LESSON XXXI. 
 Nervous System. II. Functions of Different Parts .. 137 
 
 LESSON XXXII. 
 Review 142 
 
 LESSON XXXIII. 
 The Senses in General. Sense of Touch 144 
 
 LESSON XXXIV. 
 Taste and Smell 148 
 
 LESSON XXXV. 
 Sight. 1 150 
 
 LESSON XXXVI. 
 Sight. II 154 
 
 LESSON XXXVII. 
 Hearing 159 
 
 LESSON XXXVIII. 
 Review 163 
 
 LESSON XXXIX. 
 The Mind 166 
 
 QUESTIONS 173 
 
 GLOSSARY OF WORDS 183 
 
 INDEX 190 
 
PHYSIOLOGY. 
 

 
LESSON I. 
 
 ORGANIC AND INORGANIC MATTER ANIMAL STRUC- 
 TURE. 
 
 From time immemorial all things around us have 
 been looked upon as either living or lifeless. Liv- 
 ing objects are plants and animals; lifeless, such 
 substances as mineral coal, iron, sand, rocks, water 
 or air. Although at the present advanced state of sci- 
 ence it is often difficult to draw the line, yet that dis- 
 tinction is still maintained, because between things 
 
10 FIRST LESSONS IN PHYSIOLOGY. 
 
 like those last mentioned, and substances such as 
 wood or flesh, the differences are very striking. 
 
 All so-called lifeless substances are comprised un- 
 der the head of inorganic matter, while the vegeta- 
 ble and animal worlds form the organic matter. 
 
 The distinction between these two great classes of 
 materials is based upon form, coherence, growth, 
 composition and derivation. 
 
 Form. The sharp angles and straight lines of a 
 crystal, the nearly regular features of most frag- 
 ments of rock, are characteristic. On the other 
 hand, notice the general absence of straight outlines 
 in living structures, the curved shape of leaves and 
 flowers, the rounded forms of the higher animals, 
 and particularly those of the human body. Distin- 
 guish between the fracture of a lump of mineral 
 coal and that of charcoal. It will be your impres- 
 sion that inorganic matter, generally speaking, as- 
 sumes forms of a severer pattern. 
 
 Coherence. Particles of sandstone cling together 
 owing to cohesion, without having any other mutual 
 relation. A fragment of sandstone truly represents 
 the original rock of which it once formed a part, in- 
 asmuch as it possesses all the properties of the rock. 
 The particles of a tree cohere likewise, but they are 
 closely dependent upon one another. A piece of 
 wood does not strictly represent the tree from which 
 it came, because in different parts of the same tree 
 the wood may have different properties. Hence, the 
 coherence of organized matter greatly differs from 
 that of substances of the inorganic world. 
 
ORGANIC AND INORGANIC MATTER. 11 
 
 Growth. If the growth of a crystal, or of an or- 
 dinary rock, could be plainly observed, it would be 
 found to consist in a mere adding of particle after 
 particle on the outside, without any interior devel- 
 opment. Nor would it be found accompanied by 
 decay, or repair, going on at the same time ; whereas, 
 plants and animals, during their growth, always 
 decay in part that is, while they are building up 
 they also lose waste matter, only the building up is 
 far greater in quantity than the waste. This is true, 
 regardless of the manner in which a plant grows, 
 whether, for example, like most of our trees, it grows 
 by adding superficial layers or rings around the 
 stem, or, like Indian corn, by developing from 
 within. Animals grow by interior development; 
 carbonic acid gas and water vapor are two products 
 of animal waste. Plants and animals make up the 
 organic world, or world of organisms, and all organ- 
 isms differ in their manner of growth from objects 
 belonging to the inorganic world. 
 
 Inorganic substances present a mere building up 
 without corresponding development of all parts, 
 while an organism develops throughout, and thereby 
 attains gradually to a higher organization. The 
 grain of corn generates the plant ; the egg brings 
 forth the bird; the infant develops into the full 
 grown man. Nothing of the kind takes place in 
 inorganic matter. 
 
 Composition. Copper, gold and iron are ex- 
 amples of elemental bodies ; however subdivided, 
 they always remain the .same. Water is composed 
 
12 FIRST LESSONS IN PHYSIOLOGY. 
 
 of two elements ; quartz- crystal of three. Nearly 
 all inorganic substances are of simple composition, 
 and, therefore, more stable than organic substance, 
 such as wood, or flesh, which are more complex in 
 composition, and decompose more readily. 
 
 Derivation. An organism is derived from a 
 parent ; inorganic matter is not. This is one of the 
 most peculiar characteristics of organisms. 
 
 Organisms live, develop and die ; inorganic bodies 
 are not said to live, develop or die. 
 
 The structure of a higher animal required for 
 the complete display of its capacities, may be repre- 
 sented thus : 
 
 1. An apparatus to convert food into a fluid which 
 will develop and maintain the body, and to remove 
 waste materials. 
 
 2. A system of vessels to convey this fluid to all 
 parts of the body. 
 
 3. A muscle or heart which, by contracting and 
 relaxing, pumps the fluid into the vessels. 
 
 4 A mechanism for respiration, so as to purify 
 the fluid by a fresh supply of oxygen. 
 
 5. Contractile cords or muscles to set the different 
 parts of the body in motion. 
 
 6. A mass of nervous matter, with nervous fibres 
 spreading over the body, to receive impressions from 
 the outer world, and to convey manifestations of 
 will, &c., to the various portions of the body. 
 
BONES. 13 
 
 LESSON II. 
 
 BONES THE SKELETON. 
 
 1. EXPERIMENT. Expose a bone to the action of 
 intense heat. Its shape will be preserved, but it 
 will no longer be strong and tough ; it will not sup- 
 port as much weight as before. It has now lost its 
 animal substance. 
 
 2. EXPERIMENT. Soak a bone in dilute acid. Its 
 shape will be retained, but its firmness is destroyed ; 
 it may now be bent without breaking. It has lost 
 its mineral substance. 
 
 The composition of bones is a close union of ani- 
 mal and mineral substances. In the normal bone 
 both substances exist in definite proportions. A 
 deficiency in the mineral ingredients (chiefly lime), 
 as is the case with bones in early life, causes the 
 bones readily to bend; while an excess of lime, 
 always found in the bones of old people, renders 
 the bones brittle. 
 
 The structure of bones shows a net- work of small 
 canals and layers of bone substance. Bones are less 
 dense at their centres ; many of them contain a fatty 
 substance, called the marrow. Bones grow and con- 
 stantly renew their particles. 
 
14 FIRST LESSONS IN PHYSIOLOGY. 
 
 The growth of bones. Every bone of an adult 
 was at one time a cartilage. It did not become har- 
 dened uniformly throughout its mass, but the pro- 
 cess of ossification that is, the deposition of min- 
 eral matter in the cartilage took place first at 
 particular points, called the centres of ossification. 
 Thus the long bones of an infant contain at least 
 three such centres or bony masses, one in the middle 
 part of the bone (then as yet a cartilage), and one 
 situated toward each end. In the adult these three 
 osseous centres are united into one solid bone. 
 
 When the edges or ends of bones in their growth 
 come to touch each other, they either form joints or 
 articulations, in order to enjoy motion upon each 
 other ; or they grow firmly together, forming sutures. 
 Sutures may be readily ascertained in the bones 
 composing the skull. 
 
 The skeleton consists of all the bones in the 
 human body, the total number of which is about 
 two hundred and ten, excluding the teeth. Besides, 
 there is found a firm, elastic tissue called cartilage 
 or gristle, such as the outer ear or the lower part 
 of the nose. 
 
 The skeleton forms the framework of the body. 
 It is usually divided into three distinct portions : 
 the head, the trunk, and the (upper and lower) limbs 
 (Fig. 1). It contains three cavities ; the uppermost 
 is a hollow box of bone, the skull or cranium ; this 
 contains the brain, and has attached to it the jaws 
 and the remaining bones of the head. 
 
Frontal Bone 
 
 Upper Jaw 
 Lower Jaw 
 
 Collar Bone 
 
 Chest 
 
 Occipital Bone 
 
 ertebrae of 
 the Neck. \ 
 
 Vertebral 
 Column. 
 
 ' 
 
 - Shoulder Blade 
 
 Ankle 
 
 Arch. 
 
16 FIRST LESSONS IN PHYSIOLOGY. 
 
 Below this a bony case or basket is seen, called 
 the chest or thorax; and further down a bony basin, 
 the pelvis. The chest and the pelvis, together with 
 the backbone, form the trunk of the body. The 
 arms, or upper extremities, are attached to the 
 upper part of the chest by means of the collar bone 
 and the shoulder /blade. The legs, or lower extremi- 
 ties, are fastened to the lower part of the trunk. 
 
 Bones, like all organic structures, consist of cells 
 that is, of cellular tissue ; the cells are more or less 
 of a hexagonal form. Bones are renewed even more 
 rapidly than any other portion of the body except 
 the nails, the skin and the hair. The natural pro- 
 cess by which broken bones are restored, is remark- 
 able. The immediate -result of the injury is an 
 effusion of blood around the broken parts. This is 
 soon replaced by a watery fluid, which, after some 
 time, thickens into a jelly-like mass. In a month 
 or two this mass hardens, and slowly acquires the 
 properties of bone ; months after this the bones, if 
 carefully treated, unite perfectly. 
 
THE HEAD. 
 
 17 
 
 LESSON III. 
 
 THE HEAD THE CEKEBRO-SPINAL AXIS THE TEETH. 
 
 The head (Fig. 2) consists of the bones of 'the 
 skull, face and ear. Its principal parts are : 
 
 FIG. 2. 
 
 1. The frontal bone. 
 
 2. Two side bones, which form the uppermost part, 
 and part of the right and left sides of the skull. 
 
 3. Two temporal bones, one on each side of the 
 lower part of the frontal bone. 
 
18 FIKST LESSONS IN PHYSIOLOGY. 
 
 4. The occipital bone, extending down to the neck. 
 
 5. The upper jaw. 6. Two cheek bones. 7. Nosebonr. 
 
 8. The lower jaw, easily separable from the re- 
 maining parts of the head. 
 
 9. The sphenoid bone, forming the base of the skull 
 (not visible in Fig. 2). 
 
 The upper jaw contains the upper row of teeth, 
 the lower jaw, the lower. The lower portion of the 
 nose consists of cartilage, which remains soft during 
 life. The roof of the mouth is a thin but hard bone, 
 forming part of the upper jaw. 
 
 The various bones of the head are firmly joined 
 together, although they contain fissures and holes. 
 
 According to the preceding lesson, the skeleton 
 is composed of head, trunk and limbs; and the 
 trunk separable into chest or thorax, and pelvis. 
 The young student will do well to observe that the 
 head contains two distinct cavities : the cavity of 
 the skull and that of the face, which are entirely 
 separated from each other. The former contains a 
 mass of nervous substance which is called the brain. 
 This -substance is continued down to the lower end 
 of the pelvis, in the shape of a downward tapering 
 cord, called the spinal cord. This cord together 
 with the brain, pass under the name of cerebro-spinal 
 axis. Thus, we discover that the skull together with 
 the vertebral column (Fig. 3), form a tube very 
 much expanded above and exceedingly narrow at 
 its lower end ; and that this tube is completely insu- 
 lated, in the first place, by the bones of the skull, 
 and secondly, by the vertebral bones, or vertebra*. 
 
CEREBRO-SPINAL AXIS. 
 
 19 
 
 Pig. 3 
 
 __-CS 
 
 AL 
 
 CS 
 
 The other cavity, 
 that of the face, con- 
 tains the mouth. The 
 mouth is part of an- 
 other tube, called the 
 alimentary canal,which 
 extends from the 
 mouth through the 
 vc entire length of the 
 trunk in front of the 
 vertebral column (Fig. 
 3). The cavity of the 
 mouth may be consid- 
 ered the expanded 
 upper end of the ali- 
 mentary canal, just as 
 v c the cavity of the skull 
 forms the upper ex- 
 panded end of the 
 tube containing the 
 spinal cord. 
 
 The cavity of the 
 mouth contains two 
 rows of teeth, one in 
 the upper jaw, the other in the lower. Each tooth 
 has a crown, neck and fang or fangs. The crown 
 is the portion which projects beyond the gum. The 
 neck is that portion immediately below the crown 
 and on a level with the edges of the gum. The fang, 
 or fangs if there be more than one, comprises all 
 below the neck (Fig. 4). 
 
 VERTICAL SECTION OF THE HUMAN 
 BODY. 
 
 A L. Alimentary canal. 
 l r C. Vertebral column. 
 C S. Cerebto-spinal axis. 
 
20 FIRST LESSONS IN PHYSIOLOGY. 
 
 The crown is covered with an exceedingly hard 
 substance, called enamel; this is the hardest por- 
 tion of a tooth, and the hardest substance in the 
 human body. It forms a very thin layer, and serves 
 as a protection to the principal constituent of all 
 teeth, the dentine or ivory. This dentine is hollowed 
 out into a cavity, which contains a very sensitive 
 mass of nervous matter, the tooth-pulp (Fig. 4, a). 
 Teeth are partially composed of bony matter ; they 
 differ from bones in possessing enamel and dentine, 
 which bones have not. Teeth have no growth. 
 a I c d e f 
 
 FIG. 4. 
 
 There are thirty-two teeth in number, sixteen in 
 each jaw. The four front teeth in each jaw are 
 adapted for cutting purposes, and therefore named 
 incisors (b). On each side of them is a tooth with 
 one cusp that is, with a pointed crown (c). It is 
 called the eye-tooth, or, because it resembles the long, 
 tearing tusk of the dog, the canine. Next on either 
 side is a tooth (d) with two cusps on the crown, lar- 
 ger than the preceding teeth, and called licuspid. 
 Adjacent to it are teeth with more than two cusps, 
 
TEETH. 21 
 
 the molars or grinders (e and/), the broadest and 
 most powerful of all. The crowns of the molars in 
 the lower jaw have four or five cusps, while those 
 in the upper have one cusp less. 
 
 In the early period of life, each jaw has ten tem- 
 porary or milk teeth. At tho age of six or eight 
 the upper portions of these teeth fall out, or are 
 ' shed,' while the fangs are absorbed. Then appears 
 the second or permanent set of teeth, thirty-two in 
 number. Vlio following formula shows that the 
 molars of tho child are replaced by the bicuspids 
 of the adult : 
 Formula of Arrangement and number of Teeth. 
 
 Mo Ca In Ca Mo 
 
 ^ Upper, 2 1 4 1 2 = 10) 
 Temporary ( __<^Q 
 
 Teeth Lower, 2 1 4 I 2 = 10 ) 
 
 Mo Bi Ca In Ca Bi Mo 
 
 Upper, 321412 316) 
 Permanent ( = ^ 
 
 Teeth Lowerj 331412 3=16) 
 
 (Compare Lesson XXV.) 
 
 Familiar Facts. Sudden changes of tempera- 
 ture, owing to very cold or very hot food or drink, 
 are dangerous to the teeth, as they may cause the 
 enamel to crack. Acids and metal toothpicks should 
 be avoided. Teeth require cleansing with water and 
 a soft brush, especially after meals. Any injury to 
 the enamel is irreparable, and, as it causes the den- 
 tine beneath to decay, may involve the loss of the 
 tooth. 
 
 Bead "Toothache," by S. Parsons Shaw. Lippincott, Philadelphia. 
 
f 
 
 FIKST LESSONS IN PHYSIOLOGY. 
 
 LESSON I V. REVIEW. 
 
 LESSON i. 
 
 1. Inorganic matter differs from organic mainly 
 in form, coherence, growth, composition and deriva- 
 tion. 
 
 2. An organism is an organized structure belong- 
 ing either to the vegetable or animal kingdom. 
 
 3. Only organisms live, develop and die. The 
 human body is the most perfect organism known. 
 
 4. The structure of a higher animal required for 
 the complete display of its capacities may be repre- 
 sented thus : 1. An apparatus to convert food into 
 a fluid which will develop and maintain the body, 
 and to remove waste materials. 2. A system of ves- 
 sels to convey this fluid to all the parts of the body. 
 3. A muscle or heart, which, by contracting and 
 relaxing, pumps the fluid into the vessels. 4. A 
 mechanism for respiration, so as to purify the fluid 
 by a fresh supply of oxygen. 5. Contractile cords 
 or muscles, to set the different parts of the body in 
 motion. 6. A mass of nervous matter, with nerv- 
 ous fibres spreading over the body, to receive im- 
 pressions from the outer world, and to convey mani- 
 festations of will, &c., to the various parts of the 
 body. 
 
REVIEW. 23 
 
 LESSON ii.- 
 
 5. Bones consist of animal and mineral material. 
 The former renders them tough and elastic ; the 
 latter gives them strength. 
 
 6. The animal substance in bones may be removed 
 by heat ; the mineral, by the action of acids. 
 
 7. Bones grow and constantly renew their particles. 
 S. The number of bones in the human body is 
 
 about two hundred and ten 
 
 9. Cartilages are firm, elastic tissues. 
 
 10. The skeleton may be divided into head, trunk 
 and limbs. 
 
 11. Bones, like all organic structures, consist of 
 cellular tissue. 
 
 LESSON in. 
 
 12. The head consists of the bones of the skull 
 and those of the face and ear. 
 
 13. The principal parts of the head are : 1. The 
 frontal bone. 2. The side bones. 3. The occipital 
 bone. 4. The temporal bones. 5. The upper jaw. 
 6. The cheek bones. 7. The nose bone. 8. The lower 
 jaw. 9. The sphenoid bone. 
 
 14. The cerebro spinal axis comprises the spinal 
 cord and the brain. 
 
 15. A tooth is composed of a crown, a neck and 
 one or more fangs. 
 
 16. The tooth-pulp is enclosed by dentine ; the 
 dentine is capped by the enamel. 
 
 17. The number of milk-teeth is twenty. 
 
 18. Each jaw of an adult should contain sixteen 
 teeth : four incisors, two canines, four bicuspids 
 and six molars. 
 
24 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON V. 
 
 THE TKUNK. 
 
 3. EXPERIMENT. The carcass of a quadruped, 
 
 if placed in a wooden box punctured on all sides, 
 and buried in the ground close by an ant-hill, will 
 after a few weeks be reduced to a skeleton, which 
 may be used to advantage in studying the human 
 skeleton. 
 
 The skull is supported by an upright column, called 
 the spinal column or back-bone. It consists of thirty- 
 three articulated bones, which are so fastened to- 
 gether that the entire number appears as an un- 
 broken pillar, forming the central, most important, 
 and, let us add, the most wonderful part of the 
 skeleton. Nearly all the organs of the body seem 
 to rely upon it for their support. It helps to form 
 the back wall of the chest and abdomen, which are 
 maintained by the pelvis or haunch bone. 
 
 The vertebra and joints of the back-bone may be 
 ascertained by the touch ; they begin with the back 
 part of the neck and pass down to the pelvis. In a 
 similar manner locate the ribs, which extend from 
 the right and left of each vertebra in the thorax and 
 encircle the chest. They are fastened in front to the 
 breast bone or sternum. Find the two collar bones or 
 clavicles, and observe their form. Next examine the 
 
VERTEBBJ3. 
 
 25 
 
 two shoulder-blades ; together with the clavicles 
 they form the shoulder, and protect the lungs from 
 above. 
 
 The vertebrae are perforated, that is, they contain a 
 nearly oval cavity about an inch wide, filled with 
 the spinal cord (Fig. 5, d). This cord extends down 
 to the lower end of the pelvis, The spinal column 
 protects the spinal cord within ; it serves to bear the 
 head aloft and to give the body its erect position. 
 
 FIG. 5. 
 
 d 
 
 A VERTEBRA. 
 HORIZONTAL SECTION. 
 
 TWO VERTEBRAE. SIDE VIEW, 
 
 Each vertebra presents the appearance of a hol- 
 low cylinder, to the rear portion of which are at- 
 tached seven superficial elongations or processes 
 (Fig. 5, I and <?). These processes are joined to ribs, 
 ligaments (Lesson YI) and muscles. 
 
 The number of ribs fastened to the sternum is 
 fourteen, seven on each side. The eighth and ninth 
 ribs, on each side, do not reach far enough to the 
 front; the tenth, eleventh and twelfth are shorter yet. 
 These ten ribs are called the 'false' ribs. 
 
26 FIRST LESSONS IN PHYSIOLOGY. 
 
 Between each pair of vertebrse is an interstice of 
 about one- sixth the height of the body of the verte- 
 bra. This space (Fig. 5, e) is occupied by two layers 
 of cartilage, attached to the two bones. These car- 
 tilages render the spine elastic, and make its joints 
 yield and work with ease. (All of the bones named 
 in this connection, except the body of each verte- 
 bra, are flattened and without cavity.) 
 
 The pelvis supports the spinal column and the 
 abdomen. It is formed by the two hip-bones, which 
 are held together by the lower part of the spinal 
 column, the sacrum. 
 
 During the day the spinal column, while in erect 
 position, supports the weight of the head, arms, and 
 nearly of the entire trunk. This compresses the 
 layers of cartilage between each pair of vertebrse so 
 as to diminish the length of the column. Hence, the 
 human body is actually a little shorter toward even- 
 ing, and resumes its normal length when lying in a 
 horizontal position, or after a night's rest. Elderly 
 persons shrink in height, because their interverte- 
 bral cartilages harden and become thinner; this 
 accounts for their stooping posture. Persons in the 
 habit of bending the head forward too far compress 
 the front part of those cartilages, while the rear 
 portion thickens. In course of time the cartilages 
 lose their elasticity, and the spine becomes curved 
 or * crooked.' The erect position of the spinal col- 
 umn is one of the essential requirements of health. 
 
LIMBS. 
 
 27 
 
 LESSON VI. 
 
 THE LIMBS. LIGAMENTS. 
 
 Ftg.6 Examine your arms, and locate 
 
 their bones. You will find a long 
 bone in the upper arm, and two 
 long bones in the lower. So there 
 is in the upper leg a long bone, 
 the longest and strongest bone in 
 the skeleton ; and there are, also, 
 two long bones in the lower leg. 
 
 The hand (Pig. 6) is composed of 
 three parts : the fingers, the palm and 
 the wrist. The wrist contains eight 
 little bones, placed in two rows ; to- 
 gether with the bones of the fore- 
 arm, they form the wrist-joint. The 
 palm has five bones. The four fin- 
 gers have three bones each; the 
 thumb contains only two. . The en- 
 tire hand, therefore, contains twenty- 
 seven bones. 
 
 The foot, in a similar manner, is 
 composed of three parts : the toes, 
 the arch and the ankle. The great 
 toe contains two bones ; the remain- 
 ing toes, like the fingers of the hand, 
 have three bones each (Fig. 1). The 
 
 Bones oftheArm and Hand. arc h of the foot Comprises S6V6n 
 
28 FIRST LESSONS IN PHYSIOLOGY. 
 
 bones; the ankle, two. In all, there are twenty- 
 six bones in the foot. The heel supports the rear 
 portion of the foot, or the whole body when the body 
 is in erect position. 
 
 The knee-pan covers the forepart of the knee-joint. 
 
 The mechanism which adapts the limbs in the 
 human body to their manifold uses is remarkable 
 for its effective plan and devices. No animal ex- 
 hibits a system of joints which is movable in so 
 many directions, and yet is so firm and stout. No 
 animal possesses such gracefulness in the motions 
 of its limbs, combined with so vast a capacity of 
 exertion and endurance. 
 
 The limbs are joined to the trunk in a manner 
 such that they enjoy motion in every direction 
 upward, downward, forward, backward, and in a 
 circular manner. This is secured by a ball and- 
 socket joint where the globular- shaped head of a 
 bone plays in a cup or socket. The elbow and ihe 
 ankle have each a hinge-joint^ which allows forward 
 and backward motion only. 
 
 The foot does not rest upon its whole lower sur- 
 face, but, having the form of an arch, it touches the 
 ground only at the heel and at the ball of the toes 
 in front. All the bones composing this arch or 
 " hollow of the foot," are fastened to each other by 
 ligaments in such a manner as to give them a large 
 amount of spring-force with which to resist the 
 effects of pressure produced by the weight of the 
 body and by the jar against the ground. To con- 
 vince one of the truth of this, he needs but place 
 the hollow of the foot uj on the round of a ladder 
 
LIGAMENTS. 29 
 
 Ligaments. The movable joints are fastened to 
 gether by ligaments. Ligaments are firm, fibrous 
 bands with very little mobility. The bone to which 
 a ligament is fastened may be broken by an acci- 
 dent, without harm to the ligament itself. If our 
 joints were formed by the direct contact of bones, 
 these bones could scarcely play upon each other ; 
 hence, there is cartilaginous tissue between them, 
 to give them a greater or less amount of play and 
 elasticity. In the movable joints the surfaces which 
 play upon each other, are covered with cartilage. 
 Moreover, they are enveloped by a sort of sac, which 
 feecretes a lubricating fluid resembling the white of 
 an egg. 
 
 Familiar Facts. Animals can not move their 
 claws separately ; man is able to move any of his 
 fingers independently. No animal except the bat 
 is competent, with his fingers, to make a span equal 
 to the entire length of the hand. While many an 
 animal has something like fingers ; while the bird 
 possesses a flying apparatus, and the horse greater 
 capacity for running than man, man alone has so 
 perfect a machine as the human hand with which 
 to execute such complicated motions, and to assume 
 such manifold positions and forms. 
 
 Bead, Dress and Care of the F:eL Sam. R. Wells, Publisher, 389 
 Broadway, New York. 
 
 Bead, The Hand, by Sir Charles Bell. Harper & Bros. 
 
30 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON VII. 
 
 CARTILAGES LARYNX TRACHEA. 
 
 Examine, and compare with each other, the nasal 
 cartilage, the external ear and the gullet of a bird. 
 The first is an appendage to a bone, the second is 
 not directly connected with any bone, the third is a 
 structure entirely independent of bones. All three 
 are illustrations of a dense, firm substance, called 
 cartilage or gristle. It is nearly related to bone, 
 but lacks the mineral ingredients of bone and is, 
 therefore, softer and more elastic. 
 
 The chief uses of cartilage are the following : 
 
 (1.) To yield smooth surfaces for easy friction in 
 the joints; and to act as a cushion in shocks. 
 
 (2.) To fasten bones together without destroying 
 freedom of movement, as between the vertebrae. 
 
 (3.) To serve as a firm yet not unyielding frame- 
 work, as in the larynx and trachea. 
 
 (4.) To adapt itself to all purposes where firm- 
 ness, toughness, elasticity and strength are re- 
 quired. 
 
 The Larynx. To the rear of the tongue is an 
 aperture, the glottis^ with a sort of fleshy cover, 
 the epiglottis (Fig. 7). This aperture leads to a cavity, 
 the larynx, whose sides are composed of cartilage. 
 
LAKYNX. 
 
 31 
 
 The lower continuation of the larynx forms a long 
 tube, the trachea or windpipe, composed of cartila- 
 
 Epiglottis 
 
 Right Bronchus 
 
 Larynx. 
 
 Trachea^ 
 
 Left Bronchus. 
 
 FIG. 7. LARYNX AND TRACHEA. 
 ginous rings, some of which may be felt from with- 
 
32 FIRST LESSONS IN PHYSIOLOGY. 
 
 out. These rings are complete only in front ; in the 
 rear, where the trachea rests against the gullet, their 
 ends are connected with each other by a thin mem- 
 brane and by muscular fibres. 
 
 The trachea, after entering the thorax, separates 
 into two branches, the right and left bronchi. These 
 enter the lungs and divide further into a great many 
 smaller bronchial tubes. 
 
 The larynx is the organ of the voice. It contains 
 within its cartilages, immediately below the epiglot- 
 tis, two elastic lips, known as the vocal chords. 
 These chords are controlled by certain muscles, so 
 that they can close the larynx against the passage 
 of air to or from the lungs. They can also be re- 
 laxed, or shortened and lengthened, so as to throw 
 currents of air passing between them into vibra- 
 tions that is, so as to produce sound. During in- 
 spiration the vocal chords are widely separated; 
 during expiration they relax somewhat, and are 
 nearer together. 
 
 QUESTIONS : 
 
 1. Why is not the spinal column made up of a 
 single bone in place of the vertebrae ? 
 
 2. Why are not all the ribs attached to the ster- 
 num? 
 
 3. When has the human body greater length than 
 usual? 
 
 4. State why this is the case. 
 
 5. How does a bone differ from cartilage ? 
 
 Bead "Voice and Speech." N. Y. Tribune Lecture Extra, No. 5, 1873. 
 
REVIEW. 33 
 
 LESSON VIII. RE VIE W. 
 
 LESSON v. 
 
 1. The spinal column directly supports the skull; 
 it is itself supported by the pelvis. 
 
 2. The spinal column consists of thirty-three arti- 
 culated bones or vertebrae. 
 
 3. The trunk contains the spinal column, twenty- 
 four ribs, twelve on each side; the breast bone, two 
 clavicles and the two shoulder-blades, two hip bones 
 
 and the sacrum. 
 
 4. The spinal column protects the spinal cord 
 within ; it serves to bear the head aloft, and to give 
 the body its erect position. 
 
 LESSON vi. 
 
 5. The arm is composed of a long bone in the 
 upper arm, two bones in the lower, and twenty-seven 
 bones in the hand. 
 
 6. The leg is composed of a long bone in its uppei 
 part, two bones in the lower, and twenty- six bones 
 in the foot. 
 
 7. The ball-and socket joint permits motion in 
 all directions ; the hinge-joint, only in two. 
 
 8. The arch of the foot renders the foot better 
 capable of supporting the weight of the body. 
 
 9. The movable joints are fastened together by 
 ligaments. Ligaments are firm, fibrous bands with 
 very little mobility. The bone to which a ligament 
 is fastened may be broken by an accident, without 
 
34 FIRST LESSONS IN PHYSIOLOGY. 
 
 harm to the ligament itself. If our joints were 
 formed by the direct contact of bones, these bones 
 could scarcely play upon each other ; hence, there 
 is cartilaginous tissue between them, to give them 
 a greater amount of play and elasticity. In the 
 movable joints the surfaces which play upon each 
 other are covered with cartilage. They are envel- 
 oped by a sort of sac, which secretes a lubricating 
 fluid resembling the white of an egg. 
 LESSON vn. 
 
 10. The chief uses of cartilage are : 1. To yield 
 smooth surfaces for easy friction in the joints, and 
 to act as a cushion in shocks. 2. To fasten bones 
 together without destroying freedom of movement, 
 as between the vertebrae. 3. To serve as a firm yet 
 not unyielding framework, as in the larynx and 
 trachea. 4. To adapt itself to all purposes where 
 firmness, toughness, elasticity and strength are re- 
 quired. 
 
 11. The larynx consists of a cavity surrounded 
 by cartilages ; it is the organ of voice. 
 
 12. It contains the vocal chords,which produce 
 sound by causing currents of air passing between 
 them to vibrate. 
 
 13. The trachea consists of cartilaginous rings, 
 which are complete only in front. 
 
 14. The right and left bronchi are two branches 
 of the trachea ; they divide into finer bronchial 
 tubes. 
 
 15. The epiglottis serves as a protection to the 
 larynx. 
 
MUSCLES. 85 
 
 LESSON IX. 
 
 MUSCLES FAT. 
 
 4. EXPERIMENT. Stretch out one arm and let 
 
 its upper part be grasped by another person. Then 
 slowly bend up the fore-arm; the person will now 
 feel that a portion of the upper arm is swelling ; in 
 fact, there is now a compact mass of flesh which 
 was not observable so prominent before, and which 
 relaxes again when the arm is stretched out. Could 
 we remove the skin after the arm is bent up, we 
 would find a mass of red flesh or muscle, called 
 the biceps muscle. 
 
 The motion of this muscle is, like all motion, the 
 manifestation of a force ; in the present case, the 
 force of the will. The flesh or muscle is the carrier 
 of this force. 
 
 A muscle is an aggregation of minute fibres, 
 each of which is again composed of minute fibrils, 
 held together 1<y a delicate membrane. All the 
 motions in the animal body are performed by mus- 
 cles. Muscles, generally speaking, are the organs 
 of motion. 
 
 The above experiment shows that muscles pro- 
 duce motion by means of their contractility. This is 
 the first property of muscles. Contractility implies 
 the power of shortening and lengthening, and it is 
 
36 FIRST LESSONS IN PHYSIOLOGY. 
 
 in this way that muscles move the bones to which 
 they are attached The second property of muscles 
 is their sensibility. As a general thing, healthy mus- 
 cles are not very sensitive ; witness the slight pain 
 caused by a cut in the flesh. Their sensibility con- 
 sists in this, that they can communicate to the mind 
 the state anl condition in which they are. If, for 
 example, a muscle is fatigued, or in a state of 
 cramp, we immediately become conscious of it. 
 
 About ten minutes after death the muscles of the 
 body pass spontaneously into a state of contrac- 
 tion, very nearly like that which takes place during 
 life. This produces a general stiffness of the en- 
 tire body, and is known as the rigor mortis, OY post- 
 mortem rigidity. 
 
 There are two kinds of muscles, distinguished by 
 their structure and mode of action : first, the volun- 
 tary muscles, as the biceps and nearly all the mus- 
 cles used for moving bones. The action of volun- 
 tary muscles is, to a large extent, controlled by the 
 will. Second, the involuntary muscles, as in the tra- 
 chea, the bronchi and the digestive canal. These 
 muscles are beyond the control of the will. Thus, 
 whether we will or not, the process of respiration 
 goes on day and night. The roughness of skin, 
 called goose skin, is caused by the action of involun- 
 tary muscular fibres in the skin It is usually the 
 result of cold, electricity, or sudden mental impres- 
 sions. 
 
 In children, and in some adults, we notice a soft 
 tissue, called adipose tissue or fat. It exists in 
 
FAT. 37 
 
 nearly all parts of the body. Its chief uses are 
 the following : 
 
 1st. The fat, which is situated directly beneath 
 the skin, prevents much of the heat of the body 
 from escaping, because fat is a bad conductor of 
 heat or cold. 
 
 2d. Fat serves as an elastic packing material to 
 . wrap delicate structures, such as the palm of the 
 hand and soles of the feet. 
 
 3d. It serves as a store of combustible matter 
 that is, it may be burnt up in the system, and thus 
 become a source of heat to the body. 
 
 4th. It serves to fill the cavities of the long bones. 
 It is then called marrow. 
 
 Bead Woman's Form. Harper's Magazine, Vol. 37, July, 1868. 
 
38 FIRST LESSONS IN PHYSIOLOGY. 
 
 
 LESSON X. 
 
 MUSCLES AS MOTOR AGENTS WALKING. 
 
 [First read Lesson XVI, " The Lever," in Hotze's First Lessons in 
 Physics.] 
 
 5. EXPERIMENT. Straighten the arm and extend 
 it horizontally; place a five-pound weight on the 
 hand. To uphold this weight a muscular effort, or 
 force, of about 100 pounds is required, to say no- 
 thing of the effort to sustain the weight of the arm 
 itself. 
 
 Before investigating this phenomenon, the young 
 student should be reminded that the human arm is 
 a lever with its point of support or fulcrum at the 
 point o (Fig. 8) in the shoulder-joint ; and that, in 
 virtue of this joint being a ball-and-socket joint 
 (page 28), the arm enjoys motion in a variety of 
 
 directions ; and that all these motions are exerted 
 by strongly-developed muscles, extending from the 
 shoulder-blade, clavicle and thorax to the upper 
 arm, to which they are attached(pp. 43 and 45). 
 
MUSCLES AS MOTOR AGENTS. 39 
 
 The weight (Fig. 8) is supported by a shoulder - 
 muscle, through which the power is exerted at the 
 point b. Joining the points o, I and a (the weight) 
 by straight lines, a bent lever o b a, with fulcrum at 
 
 0, is formed. The weight evidently operates at the 
 end of the long lever-arm a J, while the muscular 
 power at 5 operates only by the short lever-arm o b. 
 The ratio of the two lever-arms is about as 20 to 
 
 1. This explains why the five-pound weight, at the 
 end of the long arm, acts with a momentum of 
 nearly 5x20 = 100 pounds; and why the strong 
 shoulder muscle at the end of o 5, in order to bal- 
 ance this momentum, must pull upward with a 
 force of (nearly) 100 X 1 = 100 pounds. It also ac- 
 counts for the fact known to every one, that it re- 
 quires exertion to hold the arm extended, even 
 without any additional weight in the hand. 
 
 The strong shoulder-muscle here mentioned is 
 omitted in Fig. 8, because it would prevent o b 
 from being seen. . This muscle is the chief but not 
 exclusive supporter of the weight of the ball and 
 that of the extended horizontal arm ; in this it is 
 assisted by other muscles, among which is the 
 biceps, the muscle visible in Fig. 8. 
 
 The lever o b a is a lever of the third class, the 
 power being applied between the fulcrum and the 
 weight. A pair of tongs with which to lift lumps of 
 coal is also a lever of the third class, If, now, with 
 a little imagination, we compare the point where 
 the tongs are riveted together with the point below 
 each ear where the jaws come together : and if, fur- 
 
40 FIRST LESSONS IN PHYSIOLOGY. 
 
 thermore, we imagine each half row of teeth to be a 
 lever similar to one of the levers of the tongs, then 
 half the upper jaw, with its lower half attached, 
 forms a pair of levers like a pair of tongs. The far- 
 ther to the rear the resistance to be overcome by 
 the teeth be placed that is, the nearer to the ful- 
 crum the shorter do we make the lever-arm at the 
 end of which the weight or resistance operates, and 
 the less muscular effort is required. It follows, then, 
 that the jaws exert the greatest force between the 
 hindmost molars. Toward the front part of the jaw 
 the teeth lose their grinding power, and it is a wise 
 provision of nature that the front teeth, having but 
 small capacity otherwise, possess a knife-shaped 
 form. 
 
 From the preceding it would appear that a large 
 amount of muscular force exerted by a human be- 
 ing during the day is wasted ; bui; we must remind 
 ourselves that much of the force apparently lost is 
 realized as a gain of time, a convenience of direc- 
 tion, and as a greater range of motion. 
 
 It should be stated here that nearly all muscles 
 terminate, at their ends where they are attached to 
 bones, in sinewy, inelastic cords, called tendons. 
 Tendons form the connecting link between muscle 
 and bone, just as ligaments between bone and bone. 
 The leg of a turkey furnishes an abundance of ten- 
 dons. 
 
 Standing. When the centre of gravity of a body 
 is supported, the entire body is supported. The 
 centre of gravity in the human body lies in the ab- 
 
WALKING. 41 
 
 domen. In order that a person may stand erect, 
 therefore, the centre of gravity must be supported 
 by the legs. This requires work on the part of all the 
 muscles below the trunk. The amount of this work 
 is very great ; this is proved (1) by the difficulty 
 which a little child experiences in learning to stand 
 erect; (2) by the necessity, which the adult expe- 
 riences while standing, of frequently shifting the 
 centre of gravity, throwing it alternately over one 
 limb, so as to allow the other to rest for a short time. 
 Walking. This act comprises, 
 
 (1) The lifting of the body. This is accomplished 
 by lifting the leg, that is, by increasing the dis- 
 tance between the toes and the centre of gravity. 
 During this action, the same leg supports the entire 
 weight of the body ; the other leg, having at the 
 time no load to carry, swings freely forward, after 
 the manner of a pendulum, 
 
 (2) The forward motion of the body, and its sub- 
 sequent downward motion as the foot of the other 
 leg is planted on the ground. 
 
 (3) The forward swinging of the leg. The other 
 leg now bears the weight of the body, while the first 
 leg swings freely forward. This mechanical for- 
 ward swinging requires scarcely any muscular exer- 
 tion ; hence it affords alternate rest to each limb. 
 
 Although the entire weight of the body is carried 
 alternately by one foot ; yet an hour's walk is less 
 fatiguing than to stand still for an hour, because, 
 in walking, each limb enjoys alternate rest. 
 
42 tflKST LESSONS IN PHYSIOLOGY. 
 
 LESSON XI. 
 
 MUSCLES, CONTINUED WOKK OF MUSCLES LEAPING. 
 
 Muscles remain contracted only for a short 
 period. They soon relax, and during relaxation 
 their previous strength is regained. In walking the 
 muscles are constantly changing from contraction 
 to relaxation, while the erect position of the body 
 requires the activity of all the muscles ; for those 
 muscles which are situated in front prevent the body 
 from inclining backward, while those behind pre- 
 vent the body from bending forward. The muscles 
 upon the sides of the body act in a similar manner. 
 This explains why to stand erect and motionless for 
 a given time is much more tiresome than to move 
 about during an equal length of time. We gather 
 new strength when we rest or sleep ; complete rest 
 is found only in a lying position. 
 
 The muscles are wrapped in a tissue which is 
 found in nearly all parts of the body ; it envelopes 
 the muscles, it coats the bones and cartilages, and 
 thus connects the different portions of the human 
 body with one another. According to its different 
 uses, it varies greatly in character, being at times 
 soft and tender, at other times very dense and 
 strong, as, e. g. in the tendons. It is called connec- 
 tive tissue. 
 
MUSCLES. 
 
 FIG. 9. MUSCLES. 
 
44 FIRS I 1 LESSONS IN PHYSIOLOGY. 
 
 The muscles of the head and trunk perform no 
 such intense labor as those of the limbs ; hence, 
 they are less substantial. The roof of the skull has 
 no muscles proper, but a tendinous cap, or helmet, 
 underlying the hairy skin ; it may be moved by 
 muscles in the front and rear portion of the head. 
 The muscles of the eye are of a very delicate struc- 
 ture, and so arranged as to roll the eye-ball, move 
 it slightly forward and backward, and to raise and 
 lower the eye-lids. The tongue, the interior of the 
 mouth, the throat, in fine, all the parts of the body, 
 have suitable layers or strings of muscles in order 
 to produce motion, to hold the limbs in position, and, 
 in general, to protect the skeleton. The entire num- 
 ber of external muscles may be set down at two 
 hundred and forty pairs (Pigs 9 and 10). 
 
 When a force performs work, the \vork is always 
 a motion of some kind or other. The force of the 
 will or mind, when imparted to a muscle, causes 
 the muscle to perform work which, for the greater 
 part, consists of motion. Motions produced by the 
 human body are utilized mainly because of their 
 being converted into force when they are suddenly 
 arrested. The blacksmith having imparted motion 
 to his hammer by lifting it, changes this motion into 
 force when the hammer strikes the iron upon the an- 
 vil. If the weight of the hammer = 3 pounds, and 
 the height of its descent = 4 feet, the work performed 
 by the person is 3 x 412 footpounds . (A footpound 
 
MUSCLES. 
 
 FIG. io. MUSCLES. 
 
46 FIRST LESSONS IN PHYSIOLOGY 
 
 is a pound lifted through one foot of space against 
 gravity.) But this does not tell us anything about 
 the quantity of muscular exertion Perhaps the 
 following instance will make it clearer: If an 
 adult weighing 150 pounds wishes to leap two feet 
 high, the amount of work =2X150 300 footpounds. 
 On an inclined plane, or a stairway of gentle slope, 
 this amount of work is performed easily in one or 
 more seconds. But to do it by jumping seems to 
 require a greater effort, yet the actual amount of 
 work performed remains the same. 
 
 Leaping is a combination of two essentially dif- 
 ferent motions ; First, the body is lifted by the ac- 
 tion of the muscles; of course, there must be a sup- 
 port under foot. Next> the feet separate from the 
 ground and the body rises; gravity stops its up- 
 ward motion and pulls it down again. Let us re- 
 call the above example. The first motion, viz., 
 the lifting of the body, is effected by muscular ac- 
 tion. It has a limited range, perhaps no more than 
 one-half foot. Hence, the entire work of the mus- 
 cles=300-^J=600 footpounds, or twice the actual 
 work required. The reason of it is this : The mus- 
 cles have not only to lift 1 50 pounds 2 feet against 
 gravity, which amounts to a work of 300, but they 
 must also overcome the resistance or reaction of the 
 body, which amounts likewise to 150x2=300 foot 
 pounds; now, 300-1-300 = 600 footpounds, which is 
 the entire work performed by the muscles. The re- 
 maining space, 1 feet, is passed over in virtue of the 
 elasticity of the contracted muscles. Briefly : when 
 
LEAPING. 47 
 
 a person weighing 150 pounds jumps vertically 2 
 feet high, he must overcome gravity at every point 
 of his upward course ; this requires a work of 150X 
 2=300 footpounds ; besides, he must overcome his 
 own reaction at every point of his upward course ; 
 this demands, also, a work of 150X2300 foot- 
 pounds. In all, then, his muscular pressure amounts 
 to 600 footpounds, or twice the product of his 
 weight into the vertical height. 
 
 This work is performed in a fraction of a second ; 
 in using a stairway, however, it will consume much 
 more time, because a greater space has to be passed 
 over. 
 
 The experience of a long period of years has 
 shown, beyond doubt, that the mechanical power 
 of the human body is used to best advantage by 
 both employer and employee when the work is 
 done regularly and continuously, not in separate, 
 fitful exertions. Man's forces must not be exhausted 
 further than rest and food can replace them day 
 for day. In utilizing our physical forces, therefore, 
 certain limits must be observed, a limit of exertion 
 as well as a limit of time. Any deviation has always 
 been followed by a deterioration in the value of the 
 work done. 
 
 Read The Wonders of the Human Body. Illustrated Library of Won- 
 ders. Scribner & Armstrong, New York. 
 
48 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON XII. REVIEW. 
 
 LESSON ix. , 
 
 wwrffi/ 
 
 1. A muscle is an aggregation of minute fibres, 
 
 each of which is again composed of minute fibrils, 
 held together by a delicate membrane. All the 
 motions in the animal body are performed by mus- 
 cles. Generally speaking, muscles are the organs of 
 motion. 
 
 2. Muscular motion is exerted by means of the 
 contractility of muscles. 
 
 3. Contractility and sensibility are characteristic 
 properties of muscles. 
 
 4. Contractility implies the power of contract- 
 ing and relaxing ; sensibility, their power of com- 
 municating impressions directly to the mind. 
 
 5 Post-mortem rigidity is the general stiffness of 
 the body after death. 
 
 6. Muscles are of two kinds : involuntary and 
 voluntary ; these are distinguished by their struc- 
 ture and mode of action. 
 
 7. Nearly all the muscles used for moving bones 
 are voluntary muscles. 
 
REVIEW. 49 
 
 8. The trachea, bronchi and the digestive canal 
 have involuntary muscles. 
 
 9. The chief uses of fat are : 
 
 (1.) The fat, which is situated directly beneath 
 the skin, prevents much of the heat of the 
 body from escaping, because all fat is a 
 bad conductor of heat or cold. 
 
 (2.) Fat serves as an elastic packing material 
 to wrap delicate structures, such as the 
 palm of the hand and soles of the feet. 
 
 (3.) It serves as a store of combustible matter 
 that is, it may be burnt up in the system, 
 and thus become a source of heat to the 
 body. 
 
 (4.) It serves to fill the cavities of the long 
 bones ; it is then called marrow. 
 
 LESSON x. 
 
 10. To sustain a five-pound weight in the hand, 
 the arm being stretched out horizontally, a muscular 
 effort of about one hundred pounds is required. 
 This does not include the weight of the arm. 
 
 11. The human arm is a lever of the third class ; 
 the fulcrum lies in the shoulder-joint, and the power 
 between the fulcrum and the weight. 
 
 12. Muscles usually terminate in tendons. 
 
 13. Tendons connect bones with muscles ; liga- 
 ments connect bones with bones. 
 
 4 
 
60 FIRST LESSONS IN PHYSIOLOGY. 
 
 14. Walking consists 
 
 (1) Of the advance of the legs ; 
 
 (2) Of lifting the body ; 
 
 (3) Of advancing the body ; 
 
 (4) Of shifting the centre of gravity. 
 
 LESSON xi. 
 
 15. The erect position of the body is the result of 
 the combined action of the muscles. 
 
 16. Connective tissue is that tissue which invests 
 nearly all the parts of the body. 
 
 17. The properties of connective tissue vary ac- 
 cording to its uses. 
 
 18. The muscles of the eye roll the eye-ball, move 
 it slightly forward and backward, and raise and 
 lower the eye-lids. 
 
 19. The uses of the muscles are 
 
 (1) To produce motion ; 
 
 (2) To hold the limbs in position ; 
 
 (3) To protect the skeleton. 
 
 20. Human labor should be performed with con- 
 tinuance and regularity. The forces of man must 
 not be exhausted further than rest and food can re- 
 place them day by day. 
 
THE SKIN. 51 
 
 LESSON XIII. 
 
 THE SKIN HAIR AND NAILS EXCRETION OF THE 
 
 SKIN. 
 
 6. EXPERIMENT. A piece of fresh animal skin, 
 put in water, will swell up without dissolving. If 
 now the skin be boiled in the water for several 
 hours, most of it will dissolve, and on allowing the 
 liquid to cool, a gelatinous substance is obtained. 
 When dried, this forms the well-known glue. Nearly 
 all connective tissue yields the same result if treated 
 in a like manner. 
 
 The skin is the external covering of the body. 
 It consists of two layers the outside skin or the 
 epidermis, and the inner one or dermis. The epi- 
 dermis contains coloring matter, which gives rise to 
 shades of tint in the skin of both individuals and 
 races. It is of different thickness on different por- 
 tions of the body ; the more it is subjected to fric- 
 tion and pressure, the more does it grow that is, 
 the more does it become thick and horny. 
 
 The epidermis serves to protect the sensitive lower 
 skin or dermis, and to moderate the evaporation of 
 fluid from the blood vessels. 
 
 The dermis serves to invest the excretion glands ; 
 on its surface are the sensitive touch- corpuscles. 
 
52 FIRST LESSONS IN PHYSIOLOGY. 
 
 The dermis is the deeper portion of the skin ; it is 
 denser, more elastic and more tender than the epi- 
 dermis. When cut it bleeds very freely ; the epi- 
 dermis does not bleed at all. In sharpening a pencil 
 the outer skin is frequently cut, and no notice taken 
 of it unless the knife enters a shade deeper, causing 
 pain and flow of blood. 
 
 The general properties of the skin are toughness, 
 flexibility and elasticity. Owing to the first, it 
 serves as the protecting cover of the body ; in vir- 
 tue of the second, it shields the inner parts from 
 violence ; and, on account of the last, it yields 
 readily to the movements of the body. But it 
 serves yet another purpose not less important ; it 
 is the principal organ of touch (Lesson XXXI). 
 
 The hair and nails are peculiar forms of the epi- 
 dermis. The former is composed of horny scales 
 and cells, closely packed together. The root of a 
 hair, together with the root-sheath in which it is 
 imbedded, may be seen when a hair is pulled out 
 
 Nails grow, like hair,* by the constant addition of 
 cells from beneath and behind, which take the place 
 of portions worn away or cut off. 
 
 The secretion of the skin consists of two differ- 
 ent fluids, one oily, the other watery. The oily 
 one is secreted mostly in the scalp and the face, 
 where the skin is largely supplied with hair. The 
 other is called perspiration or sweat, the two terms 
 being habitually taken synonymously, although 
 there is this difference between them : perspiration 
 
SECRETION OF THE SKIN. 
 
 53 
 
 is an insensible excretion, which evaporates on the 
 skin ; sweat is a sensible secretion, composed of the 
 same fluid as the other, but appearing on the skin 
 in the form of drops. The passage of these fluids 
 
 is effected by a multitude 
 of fine canals or pores 
 (Fig. 11) in the skin. Per- 
 fect health requires clean- 
 liness, so that the activity 
 of the pores shall not be 
 impeded. 
 
 The quantity of water 
 lost by transpiration de- 
 pends, like all evaporation 
 in the open air, upon the 
 temperature, the satura- 
 tion and the stillness of 
 the atmosphere. In hot 
 weather the quantity of 
 excretion from the skin is 
 greater than in cold. 
 When the atmosphere is fully saturated with watery 
 vapor, perspiration does not evaporate ; and the 
 consequence is an almost insufferable sensation of 
 heat. The same holds true when, owing to the ab- 
 sence of currents of air, the watery vapors of per- 
 spiration remain around the person instead of being 
 constantly displaced by fresh, that is, less satu- 
 rated air. 
 
 Epidermis. 
 
 feg Dermis. 
 
 Glands for 
 the Hair. 
 
 Perspiration 
 Glands. 
 
 Hair. 
 
 FIG. n. Sectional View of 
 the Human Skin, Highly 
 Magnified. 
 
 Read H<nv to Bathe. E. P. Miller. Miller, Haynes & Co., N. Y. 
 
54 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON XIV. 
 
 THE BLOOD. 
 
 7. EXPERIMENT. Allow the blood of an animal 
 to remain quiet in a vessel. In a few minutes it 
 will coagulate, separating into two substances 
 a solid and a liquid. 
 
 The solid has a dark-red color, and is a sort of 
 jelly, often called the clot. The red color is due to 
 the presence of minute bodies, which are held in 
 suspension in the blood Besides these red corpus- 
 cles^ the clot contains a white, fibrinous mass, or 
 animal fibrine. The liquid is called serum; it has 
 a yellowish color, but if, by boiling it, we remove 
 its water, it will coagulate to a white jelly composed 
 of albumen. 
 
 The composition of blood that has remained 
 standing for some time is, therefore, as follows : 
 
 f ( Blood Corpuscles (red and white). 
 
 Clot. \ 
 
 [ Animal Fibrine. 
 Blood. \ 
 
 ( Water. 
 I Serum < 
 t ( Albumen. 
 
 It is characteristic of the red blood corpuscles that 
 they always contain iron. 
 
THE BLOOD. 55 
 
 The specific gravity of blood (at a temperature of 
 60 F.) is about the same as that of water. The 
 temperature of the blood in the human body is 
 generally 100 F. In the animal it has an odor 
 faintly resembling that of the animal from which it 
 came. 
 
 The quantity of blood in the living body is dim- , ^ 
 cult to ascertain ; it has been estimated at about 
 one-tenth of the weight of the entire body. In a 
 thousand parts of weight of blood seven hundred 
 and eighty-four parts are water, one hundred and 
 thirty parts are red corpuscles, and the remainder 
 is composed of albumen, fibrine, fat, and other 
 matters. The proper composition of the blood is 
 one of the three most important items in the 
 health of man. The ravages of cholera and of 
 similar diseases seem to result from a decomposi- 
 tion of this life-giving liquid. It will be seen further 
 on, that the health of the blood depends largely 
 upon our food and upon the air we breathe. 
 
 The red corpuscles of the human blood are cells 
 of different sizes, having the form of disks, each of 
 which has an area of nearly y^ of a square 
 inch, and a thickness of about 7 ^o of an inch. 
 They possess the remarkable property of adhering 
 together in columns like rolls of pennies ; these 
 rolls, moreover, join at their ends so as to cluster 
 together, forming a sort of network (Fig. 12). 
 
 Besides the red, there are white corpuscles in the * 
 blood. They differ from the former in their num- 
 
56 
 
 FIEST LESSONS IN PHYSIOLOGY. 
 
 ber being much smaller than that of the red ; for 
 every five hundred red ones there exists, perhaps, 
 one white corpuscle. During disease this ratio may 
 increase to ten, and even more, for every five hun- 
 dred. They are larger than the red corpuscles, and 
 possess* the peculiarity of alternately contracting 
 and dilating, and otherwise changing their forms. 
 
 In Fig. 13, B, there are four white, in A C, four 
 red, corpuscles, as seen through a microscope of 
 very high magnifying power. 
 
 Fig. 12. 
 
 Fig.13 
 
 The use of these little bodies is not well deter- 
 mined. The main purpose of the red seems to be 
 to convey oxygen from the lungs to all parts of the 
 body. 
 
 The gases contained in the blood are carbonic 
 acid, oxygen and a small quantity of nitrogen. 
 One hundred volumes of blood contain about fifty 
 volumes of these gases collectively. 
 
THE BLOOD. 57 
 
 Of the uses of the blood when in the healthy state, 
 the following four may here find a place : 
 
 (1.) It is a source of nutritive material, whence 
 the different parts of the body constantly draw for 
 their maintenance. 
 
 (2.) It keeps all parts of the body warm and 
 moist. 
 
 (3.) It conveys oxygen to those of the tissues 
 which need this element. 
 
 (4.) ' It collects refuse from all parts of the body, 
 and conveys the substances to places whence they 
 may be discharged. 
 
 In the next Lesson we shall learn something about 
 the manner in which the blood circulates through 
 the body. 
 
58 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON XV. 
 
 THE CIRCULATION OF THE BLOOD. I. 
 
 8. EXPERIMENT. Cut open a fresh plant, and 
 
 observe its juice. Next open an insect for the same 
 purpose ; it contains a watery, almost colorless juice 
 or blood. Then cut open a fish ; its blood is cold. 
 Lastly, procure some red, warm blood of a recently 
 killed bird or quadruped. 
 
 The preceding shows that organisms have a fluid 
 circulating through the body. 
 
 Man and the higher order of animals alone pos- 
 sess warm blood. The c vital fluid ' has a definite 
 order in which it travels through the animal sys- 
 tem. The circulation in the human body is the same 
 as in mammals and birds. 
 
 An uninterrupted current of blood through the 
 body must be maintained. This is evident from the 
 uses of the blood enumerated in the preceding Les- 
 son. The question now arises, How does nature 
 obtain such an unceasing stream rushing through 
 countless tubes and channels. 
 
 The heart (represented by 1, 2, 3, 4, in Pig. 14) is 
 a hollow muscle of about the size of its owner's fist. 
 This muscle has involuntary action, consisting of 
 alternate contraction and dilatation, which goes on 
 without interruption until death. Owing to the con- 
 
CIRCULATION OF THE BLOOD, 
 
 Venous Blood. 
 Arterial Blood. 
 Capillaries. 
 
 traction, the blood is 
 expelled from the 
 heart through arteries 
 and owing to the dila- 
 tation, it returns to the 
 heart through veins. 
 
 The heart is divided 
 ' RISH i A *M bv a Partition into 
 A two sides, right 
 
 11 3 and left (Figs. 14, 15). 
 These two sides do 
 not communicate with 
 each other. Each of 
 them has been sub- 
 divided into two por- 
 tions, an upper and a 
 lower, or into the 
 auricle (1 or 2) and 
 ventricle (3 or 4) re- 
 spectively. The heart, 
 therefore, contains 
 two auricles (1, 2) and 
 two ventricles (3, 4), 
 While the two divi- 
 sions right and left- 
 are entirely separate 
 
 The Heart and the Circulation, 
 
 Viewed from behind, so that 
 the postion of the observer 
 corresponds with that of the 
 figure. 
 
60 FIRST LESSONS IN PHYSIOLOGY. 
 
 from one another, each auricle communicates with 
 the ventricle of the same side. The opening, how- 
 ever, through which the communication takes place 
 is so constructed that it acts- like a valve (com- 
 pare First Lessons in Physics, p. 72) ; it allows the 
 blood to pass from the auricle to the ventricle, but 
 not in the opposite direction. 
 
 Fta.15 ^ e Gourse f ^e blood 
 'from auricle to ventricle 
 is of the same direc- 
 tion in e a c h side, 
 The blood in the 
 right auricle (2) is urged 
 into the right ventricle 
 (4), whence it passes 
 through a large artery 
 r a (pa) into the capillaries 
 
 The Heart and Large Blood Vessels, of the lungS, where it 
 
 absorbs oxygen, and gives out carbonic acid. This 
 artery is the pulmonary artery, one of the few 
 arteries carrying venous blood, and called an artery 
 simply on account of its being constructed like the 
 arteries. The blood is then gathered up again and 
 conveyed in large veins (pv) to the left auricle. From 
 the left auricle it emerges into the left ventricle (3), 
 the strongest of the four divisions, and thence into 
 the aorta, a, the strongest of the arteries. The aorta 
 distributes it all over the system, to the capillaries 
 of every portion of the body In these capillaries 
 the blood becomes impure, and after leaving them 
 it passes through the large veins (vc) back into the 
 right auricle (2), whence we supposed it to start. 
 
CIKCULATION OF THE BLOOD. 61 
 
 As stated before, the chief propelling force for the 
 incessant torrent of blood through the body lies in 
 the muscular substance of the heart. But there are 
 several helpers which must not be disregarded : 1st, 
 the elastic walls of the arteries (they are not un- 
 yielding like gas pipes) ; 2d, the pressure of mus- 
 cles upon some of the .veins ; and 3d, the contrac- 
 tion and expansion of the chest in breathing. These 
 aids will be better understood hereafter. 
 
 The function of each subdivision of the heart 
 may be stated thus : 
 
 a. The right auricle receives the venous blood of 
 the whole body and conveys it to the right ventricle. 
 
 b. The right ventricle impels the venous blood 
 through an artery into the lungs. 
 
 c. The left auricle receives arterial blood flowing 
 to it through veins from the lungs. 
 
 d. The left ventricle forces the blood into the 
 aorta, which distributes it over all parts of the 
 body. 
 
 In comparing the functions of these subdivisions 
 with one another it is found that 
 I. The auricles receive blood ; 
 
 The left auricle receives arterial blood from 
 
 the lungs ; 
 The right auricle, venous blood from the entire 
 
 body. 
 II. The ventricles convey away blood ; 
 
 The left ventricle conveys away arterial blood 
 
 to the entire body ; 
 The right ventricle, venous blood to the lungs. 
 
62 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON XVI. 
 
 THE CIRCULATION OF THE BLOOD. II. 
 
 Examine the movements of the heart by placing 
 the fingers between the fifth and sixth ribs, slightly 
 to the left of the breast-bone (as the lower part of 
 the heart inclines a little toward the left). Each 
 contraction of the heart will then be distinctly felt, 
 because the point of the heart strikes against the 
 wall of the chest. 
 
 The heart of a living animal, if quickly removed, 
 will continue pulsating for some time. Each pulsation 
 commences at the two auricles, and thence passes 
 to the two ventricles. That is to say, each pulsation 
 of the heart consists of 1st, a simultaneous con- 
 traction of both auricles ; 3d, immediately after this 
 a simultaneous contraction of both ventricles ; and 
 3d, a moment of rest or relaxation. 
 
 After this rest the contractions commence again in 
 the same order as before, and the relaxations occur 
 also in the same order as before. The work of the 
 heart is carried on, as all labor should be, regularly 
 and continuously, with due regard to rest. 
 
 The two contractions of the heart with its subse- 
 quent repose, are often represented by two short 
 marks and a rest, thus : ' - . The contraction 
 of either auricle or ventricle is called its systole; 
 the pause during the dilatation of either auricle or 
 
CIRCULATION OF THE BLOOD. 63 
 
 ventricle is called the diastole. This diastole or 
 pause occupies about the same length of time as 
 the two systoles together ; so the heart's action has 
 a certain rhythm. 
 
 The action of the heart may now be explained. 
 It is filled with blood, and the first contraction, or 
 the systole of the auricles, happens. The auricles 
 are, as it were, pressed together, and the liquid 
 within is forced out. Where can it go ? On exam- 
 ining Fig. 14 two outlets are found to exist. It may 
 pass back into the veins, or else descend into the 
 ventricles. The amount of resistance encountered 
 in each direction will decide the question. The re- 
 sistance encountered toward the veins is very great, 
 because exerted by the blood in all the veins ; that 
 encountered toward the ventricles will be exceed- 
 ingly small, because, in the first place, the valves 
 leading into the ventricles are open ; in the second 
 place, the walls of the ventricles, in their relaxed 
 state, are easily expanded ; and in the third place, the 
 resisting pressure of the arterial blood is rendered 
 naught by the valves between the ventricles and 
 arteries being closed. For these reasons only very 
 little blood will pass back to the veins ; nearly all 
 of it rushes at once into the ventricles. When the 
 ventricles are thus filling they become expanded, 
 and the blood getting behind the valves which 
 separate each auricle from its ventricle, the ven- 
 tricles are soon closed. The contraction of the 
 auricles now ceases, their walls relax, and immedi- 
 ately blood from the veins enters them, slowly ex- 
 
64 FIRST LESSONS IN PHYSIOLOGY. 
 
 panding them again. The auricular systole is now 
 over. 
 
 The next movement of the heart is the contrac- 
 tion of both ventricles. The walls of the ventricles 
 are strong and thick ; the pressure, therefore, which 
 they produce in suddenly contracting is very great, 
 and has the effect of shutting up the auriculo-ven- 
 tricular valves so that not a drop of blood can enter 
 the auricles. But it is toward the arteries that the 
 ventricles meet with most of the resistance. There 
 is the resisting pressure of the blood in the arteries, 
 a pressure which is very great because it is made 
 up first, of the weight of the blood; second, of 
 the resistance of the walls of the arteries to further 
 expansion ; third, of the friction of the blood in the 
 capillaries. All this explains why the walls of the 
 ventricles are built so very strong : they have more 
 work to perform than the auricles. It also shows 
 the necessity of the valves between the auricles 
 and ventricles ; and that no valves are needed be- 
 tween the auricles and veins. The auriculo-ventri- 
 cular valves act like the lower valve in a pump. 
 The whole office of the auricles seems to be to fill 
 the ventricles. And the contraction of the left ven- 
 tricle forces the blood into the arterial system of 
 the body, while the contraction of the right ventricle 
 impels the blood into the artery of the lungs. This 
 simultaneous contraction of the ventricles forms the 
 ventricular systole. 
 
 The arteries receive a fresh supply of blood at 
 every systole of the ventricles ; during a part of the 
 
CIRCULATION OF THE BLOOD. 
 
 65 
 
 time in which they transmit the shock, the diastole 
 of the heart occurs. Each ventricle contains about 
 three ounces of blood ; the whole of this passes, at 
 each contraction, into the respective arteries. The 
 great pressure of this quantity of blood (about one- 
 fifth of the pressure of the atmosphere) suddenly 
 forced into the main arteries, necessarily distends 
 them, because they are elastic and yielding ; but a 
 reaction takes place, and the elastic walls of the 
 arteries contract again This contraction has two 
 effects in opposite directions : it causes, first, the 
 valves between the arteries and ventricles to close 
 instantly ; second, the blood to pass from the larger 
 Fiq.16 to the smaller arte- 
 
 V T"^v A ^T" ^ ^"""^-" -^ 
 
 ries. Thence the 
 fluid enters the rami- 
 fication of the capil- 
 
 larieS (^8- 16). A 
 little reflection will 
 show that a corre- 
 sponding quantity of 
 blood passes at the 
 same time from the 
 capillaries through 
 CAPILLARIES. the veins back to- 
 
 ward the heart. The effect, then, of the ventricular 
 systole is 1st, the propulsion of blood through the 
 arteries into the capillaries ; and 2d, the return of 
 the fluid from the capillaries through the veins to 
 the heart. 
 
 The impulse given at every ventricular systole to 
 5 
 
the Mood in the aon* is spent in oiging the Wood 
 forward throogh the arteries* and. next, in distend 
 ing the elastic walls cdT the arteries This sodden ex~ 
 
 indgrres rise to 
 
 is catted thejraibe The poise 
 
 the artery. Each pokation means, of cooise* 
 
 uteries are exposed to the touch, as 
 siderf the neck, in front of t be ear, or 
 Tney appear to occur a tittle after 
 to a want of 
 
 applied only as it rashes through the artery. To 
 feel Ac poise* the wrist is selected by physicians 
 for cMTienience sake. The poise is fee index of the 
 of the heart. Its resulantr, stra^th, fott- 
 id a number of peculiarities, indicate the 
 
 oftkelxaort may lie distinctly heard 
 dosery OTOT the heart. They 
 with great regularity first, a pio- 
 like that of the word 
 
 r 
 
 5 
 
 
 
OF THE BLOOD. 07 
 
 die shock is spread orer a laige network of 
 capillary tubes; diis makes its effect imperceptible. 
 For the same reason, the blood in the capDaries 
 flows steadily, while from a severed artery it jets 
 forth in jerks. The elasticity of the arteries seems 
 to do for the blood what an air chamber does for 
 die water of a pomp. 
 
 From what has been said in regard to die arte- 
 ries, their uses chiefly are JJrrf, to conrey blood to 
 the system, and secondly, to oonrert the jerking 
 motion of the blood into a uniform flow. 
 
 9. EXPEBDOHT. Clasp die lower port of die arm 
 tightly a little abore die wrist; die Tons on die 
 back of die hand will soon distend, and knotty 
 points become visible. When die ptes&uie is le- 
 mored they will empty themselves, and die swell- 
 ing disappears. Kow, why did this not' completely 
 check the circulation of the blood I There are two 
 reasons: In the first place, the reins communicate 
 with each other by means of many blanches, so that 
 whenever the blood, for any reason, be stopped in 
 one vein, it at once passes through branch Teasels to 
 another, unimpeded vein, and finally to the heart 
 Bat it may be argued that in die above experiment 
 the arm had been encircled with so much pressure 
 that even the branch vessels were closed. Circulation 
 would, nevertheless, have continued, because, in the 
 second place, die veins are provided with valves 
 (Kg. 17) which are open as long as the flmd flows 
 toward the heart, bat which close when it 
 in the opposite direction. Those knotty places 
 
68 FIRST LESSONS IN PHYSIOLOGY. 
 
 the closed valves, preventing the backward flow of 
 the blood to the capillaries. Were it not for this 
 valvular action in the veins, any such disturbance 
 as the one occasioned by the experiment would 
 
 Fig.17. 
 
 impel the blood to the capillaries, where it would 
 resist, and finally overcome, the onward motion of 
 the blood in the arteries, which would speedily in- 
 terrupt the circulation. 
 
 The frequency of pulsations depends upon the 
 age, sex and health of a person. During the first 
 years of life about 130 pulse-beats may be counted 
 in a minute, while twenty years later the same per- 
 son's pulse will beat nearly 70 times, and increase 
 again toward old age. The pulse of women beats 
 more rapidly than that of men. 
 
 Bead First Series of Science Lectures. John Heywood. Deansgate, 
 Manchester 
 
REVIEW. 
 
 LESSON XVII. REVIEW 
 
 LESSON xin. 
 
 1. Connective tissue, when boiled, yields gelatine. 
 
 2. The skin consists of the dermis and epidermis. 
 
 3. The use of the dermis is, to invest the excretion 
 glands, and to bear the touch corpuscles. 
 
 , 4. The use of the epidermis consists in protecting 
 the dermis, and limiting the evaporation from the 
 blood vessels beneath. 
 
 5. The general properties of the skin are 1st, 
 toughness, which enables it to serve as a cover to 
 the body ; 2d, flexibility, by which it protects the 
 muscles; and 3d, elasticity, by which it yields 
 readily to the movements of the body. 
 
 6. The skin is the principal organ of touch. 
 
 7. The hair and nails are peculiar forms of the 
 epidermis. 
 
 8. The excretion of the skin consists of oily mat- 
 ter, and of perspiration or sweat. 
 
 9. The amount of transpiration depends upon the 
 temperature, saturation and stillness of the atmos- 
 phere. 
 
 10. The skin excretes about one fiftieth as much 
 carbonic acid gas as the lungs. 
 
FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON xiv. 
 
 11. Animal blood, after standing for some time, 
 contains 1st, red and white corpuscles ; 2d, animal 
 fibrine ; 3d, water ; and 4th, albumen. The first two 
 form the clot, the remaining two the serum. 
 
 12. The specific gravity of blood = 1, very nearly ; 
 its temperature = 100 Q F., nearly. 
 
 13. The living body contains a quantity of blood 
 of about one- tenth of its own weight. 
 
 14. A thousand parts of weight of blood contain 
 780 parts of water, and 130 parts of red corpuscles ; 
 the remainder is composed of albumen, fibrine, fat, 
 and other matters. 
 
 15. The proper composition of the blood is one 
 of the three most important requirements for health. 
 (For the other two see pp. 81 and 88.) 
 
 16. The red blood corpuscles differ from the white 
 in this, that they are smaller in size but larger in 
 number, and of a less changeable nature. 
 
 17. The use of the red corpuscles seems to be to 
 convey oxygen from the lungs to all parts of the 
 body. The use of the white is not fully known. 
 (Compare Lesson XXVII.) 
 
 18. The blood contains dissolved within it three 
 gases : carbonic acid, oxygen, and a small quantity 
 
 >f nitrogen. 100 volumes contain about 50 volumes 
 of these gases collectively. 
 
REVIEW. 71 
 
 19. The following are four uses of the blood : 
 
 (1) It feeds the different parts of the body, 
 
 which depend upon it for their mainten- 
 ance. 
 
 (2) It provides the entire body with warmth 
 
 and moisture. 
 
 (3) It carries oxygen to the tissues which need 
 
 this gas. 
 
 (4) It gathers refuse matter throughout the 
 
 body, and conveys it where it may be 
 discharged. 
 
 LESSON xv. 
 
 20. Organisms of every kind need a fluid which 
 circulates through the body and nourishes all the 
 parts of the body. 
 
 21. The human heart is a small, hollow muscle, 
 with involuntary action consisting of alternate con- 
 traction and dilatation. 
 
 22. Arteries are vessels conveying the blood from 
 the heart ; veins are vessels conveying the blood to 
 the heart. , 
 
 23. The force which propels the blood through 
 the body lies in the substance of the heart. Its 
 assistants in this are : 1st, the elastic walls of the 
 arteries ; 2d, the muscular pressure upon some of the 
 veins ; 3d, the contraction and expansion of the chest 
 in breathing. 
 
72 FIRST LESSONS IN PHYSIOLOGY. 
 
 24. The right side of the heart is entirely separ- 
 ated from the left side. Each is subdivided into an 
 auricle and ventricle. The heart contains two auri- 
 cles and two ventricles. 
 
 25. Each auricle communicates with its ventricle 
 below by means of an aperture provided with a 
 valve. 
 
 26. The circulation of the blood takes place in the 
 following manner : The blood leaves the right auri- 
 cle of the heart and enters the right ventricle ; thence 
 it flows through an artery to the lungs ; from the 
 lungs it passes through several veins to the left 
 auricle, whence it is impelled into the left ventricle. 
 It then rushes into the aorta, and is forced through 
 every portion of the body ; it finally returns through 
 veins to the right auricle, whence we supposed it 
 to start. 
 
 LESSON xvi. 
 
 27. A pulsation of the heart consists 
 
 (1) Of a contraction of the auricles ; 
 
 (2) Of a contraction of the ventricles ; 
 
 (3) Of a pause. 
 
 28. The contraction of either auricle or ventricle 
 is called its systole ; the pause during the dilatation 
 of either is called the diastole of the heart. 
 
 29. During the auricular systole the blood rushes 
 from the auricles into the ventricles. 
 
BE VIEW. 73 
 
 30. During the ventricular systole the blood is 
 forced into the arterial systems of the body and 
 lungs. 
 
 31. The contraction of the arteries has two effects 
 in opposite directions : 1st, the closure of the auri- 
 culo- ventricular valves; 2d, the propulsion of blood 
 from the larger to the smaller arteries. 
 
 32. The general effect of the ventricular systole 
 is the propulsion of blood through the arteries into 
 the capillaries, and back through the veins to the 
 heart. 
 
 33. The pulse is the expansion of the artery, caused 
 by the passage of a wave of blood at every ventri- 
 cular systole. 
 
 34. The sounds of the heart are two : a long sound 
 and a short one ; they are succeeded by a rest. 
 
 35. The capillaries are pulseless. 
 
 36. The chief uses of arteries are : 1st, to convey 
 the blood to the system ; 2d, to produce a uniform 
 motion of the blood. 
 
 37. Whenever the flow in the veins of a limb is 
 checked, the branch-vessels and the valves of the 
 veins prevent the interruption of the circulation. 
 
74 FIRST LESSONS IN PHYSIOLOGY 
 
 LESSON XVIII. 
 
 THE LUNGS. 
 
 The blood nourishes' the different parts of the 
 body (Lesson XIV), and at the same time removes 
 effete matter that is, all such particles as have 
 served their function in the body. This gives rise 
 to two distinct kinds of blood, the arterial or nutri- 
 ent, and the venous, the carrier of waste matter. The 
 most important difference between the two is, that 
 venous blood contains less oxygen and more car- 
 bonic acid gas than arterial. The latter is of a 
 scarlet color, but on passing through the capillaries 
 of the body it is converted into venous blood, at 
 the same time becoming darker. The venous blood 
 passes from the heart to the lungs, where it is con- 
 verted into arterial blood by the absorption of 
 oxygen gas. This conversion is mainly effected by 
 the peculiar structure of the lungs ; it is aided by 
 the acts of inspiration and expiration, as well as by 
 other processes. The conversion takes place during 
 the passage of venous blood through the capilla- 
 ries of the lungs (Fig. 21). 
 
 The lungs occupy the greater portion of the chest ; 
 they are situated on both sides of the heart (Fig. 
 18). They receive air through the trachea and the 
 larynx ; these communicate with the external air by 
 two channels, the mouth and the nasal tubes. The 
 
THE LUNGS. 
 
 75 
 
 mouth can be opened or closed at will ; the nasal 
 passages are not subject to the will. The left lung 
 consists of two separate portions, called lobes; the 
 right lung has three lobes (See Fig. 18). Each 
 lung is composed of a spongy^ elastic substance, 
 and is often compared to a bag. Each is attached 
 to one of the two bronchi (Fig. 19, c). These bron- 
 chi, or bronchial tubes, after entering the lungs, 
 
 Fig.18. 
 vc' a' 6 ff vc' 
 
 Lungs, Trachea and Heart, 
 a Aorta. a y Arteries. 
 b Trachea. vc Veins, entering 2. 
 
 2 Right Auricle. 
 
 3 Left Ventricle, with Left Auricle above. 
 
 4 Right Ventricle. 
 
 Pulm. Art. and Pulm. Veins 
 (pa and/z/, Fig. 15) visible. 
 
 Trachea, Bronchial Tubes 
 
 and Left Lung, 
 a Larynx. 
 b Trachea. 
 c Right Bronchus. 
 d Small Bronchial Tubes. 
 e Minute Bronchial Tubes 
 
 (4*0 in. diameter). 
 
76 
 
 FIKST LESSONS IN PHYSIOLOGY. 
 
 divide and subdivide into a great number of smaller 
 and smaller tubes (d\ which penetrate to every part 
 of the lungs. The trachea and bronchial tubes, 
 owing to their cartilages, are unyielding, so as to 
 remain permanently open ; the finer tubes (e\ about 
 fa of an inch in diameter, have no cartilages ; there- 
 fore, they may be closed by contraction. The minute 
 portion of a lobe is called a lobule; a lobule is a 
 little lung of itself. Each minute bronchial tube 
 passes into a lobule. After entering the lobule, the 
 small bronchial tube divides still further into smaller 
 branches (Fig. 20), whose walls at length become 
 
 exceedingly thin. Each such 
 minute branch widens at its 
 end into an air-cell. 
 
 An air-cell therefore is a 
 minute cavity of about ^ of 
 an inch in diameter (Fig. 
 21). The air-cells are ar- 
 ranged singly, or in groups 
 so that a series of cells open 
 into the same bronchial 
 tube. The lungs are made 
 Fig. 20. Bronchial Tubes, with up of air-cells. Each air- cell 
 
 Air-Ceils (magnified 15 times). carrieg a network of Capil- 
 
 laries that is, of minute blood vessels (of about 
 nfo-G inch diameter) ; this network is so dense that 
 its open spaces, or meshes, are even narrower than 
 the capillaries themselves. Between the air in the 
 cells, then, and the blood in the capillaries are but 
 
THE LUNGS. 77 
 
 two delicate membranes, that of the cells and that 
 of the capillaries 
 
 The purpose of this network of capillaries is to thor- 
 oughly expose the blood to the action of the air. 
 This is accomplished, 1st, by spreading the blood 
 over a large surface; 2d, spreading it in thin 
 
 Fia.21 
 
 300 
 
 Fig. 21. Air-Ceil, with Capillaries. 
 
 streams ; 3d, protecting it by merely a very delicate 
 cover. The renewal of the blood in these capillaries 
 is a result of the circulation ; the renewal of the air 
 in the cells is the result of respiration. The number 
 of respirations is from fifteen to eighteen a minute, 
 and varies slightly, according to the age of life. 
 
 Venous Hood absorbs oxygen in the lungs through 
 the membranes separating it from the air, while at 
 the came time it parts with carbonic acid gas and water 
 vapor. This influx of oxygen into, and efflux of car- 
 bonic acid gas and water-vapor out of, the blood form 
 the most important part of the respiratory process. 
 
78 FIRST LESSONS IK PHYSIOLOGY. 
 
 They purify the blood in changing it from venous 
 into arterial, the means of purification being the 
 peculiarly delicate membranes mentioned above. 
 (See also page 80.) But the action of the mem- 
 branes alone would suffice only for a short time, 
 since the carbonic acid gas accumulates very 
 rapidly, and in large quantity, and also because 
 oxygen is needed all over the system at every in- 
 stant of time. Hence, we need a rapid removal of the 
 carbonic, acid gas from the lungs, and at the same 
 time an incessant importation of fresh oxygen. We 
 find that the clearing away of the one and the supply 
 of the other, are accomplished incessantly by the 
 act of inspiration and expiration. The most powerful 
 aids in this process are the elasticity of the lungs, 
 the mobility of the sides of the chest, and the 
 mobility of the diaphragm. The diaphragm is a 
 strong muscle separating the chest from the abdo- 
 men, thus forming the floor of the chest. Its special 
 business is to assist respiration. 
 
 To avoid chilling the lungs, cold air should be 
 inspired through the nasal passages, not through 
 the mouth. 
 
 Bead Consumption. Dr. C. Both. Lee & Shephard, New York. 
 Bead Science Lectures. First Series. Heywood, Manchester. 
 
RESPIRATION. 79 
 
 LESSON XIX. 
 
 RESPIRATION. 
 
 The inspiration of air into the lungs is effected in 
 this way : The lungs are in close contact with the 
 inner side of the chest walls ; the lower portion of 
 the lungs is in close contact with the diaphragm. It 
 is evident that whenever the chest walls move the 
 lungs must also move, and vice versa. So, when the 
 chest expands the lungs expand ; or, more properly 
 speaking, they are enlarged by a quantity of air 
 which rushes through the larynx, trachea and 
 bronchi, to fill the lungs (compare First Lessons in 
 Physics, Lesson XIX, p. 71). 
 
 In expiration the chest walls contract ; the lungs 
 contract likewise that is, a quantity of air is 
 ejected from the lungs and forced to pass through 
 the bronchi, trachea and larynx, this being the only 
 communication between the lungs and the external 
 air. The act of expiration is followed by a short 
 rest. 
 
 The widening of the chest during inspiration is 
 owing to the motion of the ribs ; the lengthening of 
 the chest during inspiration, to the descent of the 
 diaphragm. In ordinary inspiration both chest and 
 lungs return to the state of rest by their elasticity. 
 Ordinary inspiration is nearly exclusively effected 
 
80 FIEST LESSONS IN PHYSIOLOGY. 
 
 by the mobility of the diaphragm and the ribs. In 
 very deep inspiration, the dimensions of the chest 
 are increased still further by the ascent of the clavi- 
 cle and the stretching of the vertebral column. 
 
 The rhythm observable in the respiratory process is 
 inspiration, expiration, pause ; that of the heart 
 being, in a similar manner, auricular systole, ven- 
 tricular systole, pause. 
 
 Inspired and expired air differ from each other 
 chiefly in the following points : 
 
 (1.) Expired air has nearly the same temperature 
 as the blood, whatever may be the temperature oi 
 the external air. 
 
 (2.) Expired air is always filled with water-vapor. 
 
 (3.) Expired air always contains more carbonic 
 acid gas and less oxygen than inspired air. One 
 hundred parts of air breathed once have lost about 
 five parts of oxygen, and gained a little less than 
 five parts of carbonic acid. This is shown by the 
 following statement : 
 
 Oxygen. Nitrogen. Carb. Acid. 
 
 loooo parts of atmosperic air contain 2080 7916 4 
 
 I oooo parts of expired air contain (nearly) 1600 7916 484 
 
 The absorption of oxygen by the venous blood in the 
 lungs is accomplished by the red blood corpuscles. 
 Although separated from the oxygen by the thin 
 walls of the air-cells, they seize upon the oxygen, 
 attach themselves to it, and make it accompany 
 them on their journey through the system. The 
 
RESPIRATION. 81 
 
 activity of the oxygen is thus highly increased, and 
 causes very important chemical changes in the body 
 as it unites with the carbon particles in the blood, 
 gradually changing them into carbonic acid. This 
 gas remains dissolved in the blood, giving the latter 
 its dark-red color ; but upon arriving in the lungs 
 it is liberated, passes out as the oxygen passes in, 
 and is removed by expiration. 
 
 Ventilation. Since about four hundred cubic feet 
 of air pass through the lungs of an adult in twenty- 
 four hours, a constant supply of oxygen that is, 
 of fresh air is one of the most essential require- 
 ments of health. And since carbonic acid gas is 
 unfit for respiration, it follows that every inhabited 
 room should have an open space to admit fresh air, 
 and an open space to convey away the waste pro- 
 ducts of respiration ; both spaces must directly or 
 indirectly communicate with the atmosphere. But 
 the presence of a surplus of carbonic acid is less in- 
 jurious than the absence of the normal amount of 
 oxygen. A person living in badly ventilated apart- 
 ments vitiates his blood, predisposes his system to 
 disease, and thus virtually shortens his life. A total 
 lack of air would result in speedy death. 
 
 Coughing is a quick and forcible expiration or 
 series of expirations; the glottis is closed, and a 
 current of air is violently forced through it into the 
 mouth. This causes the well-known sound accom- 
 panying coughing. 
 6 
 
82 FIRST LESSONS IN PHYSIOLOGY. 
 
 Sneezing is the same process, but with the cavity 
 of the mouth closed, the forcibly ejected air passing 
 through the nose. 
 
 Sighing consists of a slow, deep inspiration, fol- 
 lowed by quick and short expiration. 
 
 Laughing is a rapid succession of short and forci- 
 ble expirations, each accompanied by a ringing 
 sound. 
 
 Sobbing is a series of abrupt, inspiratory acts, 
 mostly produced by strong contractions of the dia- 
 phragm, and accompanied by sounding vibrations 
 of the vocal chords. 
 
 Snoring results from the current of expired air 
 striking against the soft palate, and causing it to 
 vibrate. 
 
 Respiration by means of the skin. Through the 
 skin of the body oxygen of the air enters, and 
 passes to the blood ; and carbonic acid gas and 
 water- vapor emerge through the skin from the body. 
 The quantity of water-vapor perspired in twenty- 
 four hours amounts to about II pounds. (Compare 
 page 69.) 
 
 The proper supply of oxygen forms one of the 
 three most important requirements for health. (For 
 the remainig two see pp. 70 and 88.) 
 
RESPIRATION. 83 
 
 THE LUNGS AND THE HEART COMPARED 
 
 Three points in common : 
 
 1. Both operate by expansion and contraction. 
 
 2. Both are involuntary organs ; that is, on ordi- 
 nary occasion they act independently of the will. 
 
 3. Both are indispensable to the maintenance of 
 
 life. 
 
 
 
 Three points of difference : 
 
 1. The lungs contain air; the heart contains 
 blood. 
 
 2. The lungs contain bronchial tubes, air-cells 
 and blood-vessels ; the heart has two parts, called 
 the right and the left side, each part being again 
 divided into auricle and ventricle. 
 
 3. The lungs purify the blood ; the heart propels 
 the blood through the body, 
 
 Bead Cough and Colds. Kurd & Houghton, New York. 
 Bead Ventilation. Popular Science Monthly, VoL I, p. 356. 
 
84 FIEST LESSONS IN PHYSIOLOGY. 
 
 LESSON XX. REVIEW. 
 
 LESSON xviii. 
 
 1. There are two kinds of blood, the arterial and 
 venous. The main difference between them is, that 
 the latter contains less oxygen but more carbonic 
 acid gas than the former. 
 
 2. Venous blood passes from the system to the 
 heart, and from the heart to the lungs ; arterial, from 
 the lungs to the heart, and from the heart to the 
 system. 
 
 3. The lungs consist of (1) the left lung, and (2) 
 the right lung. The former has two and the latter 
 three lobes. 
 
 4. Each lung is attached to a bronchus, each of 
 which is again subdivided into a great number of 
 smaller branches, called bronchial tubes. 
 
 5. An air-cell is a cavity or the dilated end of a 
 minute bronchial tube, and about 4^ of an inch in 
 diameter. The lungs are made up of air-cells. 
 
 6. The capillaries in the lungs serve to expose the 
 blood to the action of the air. This is done by (1) 
 spreading it over a large surface, (2) spreading it in 
 thin streams, (3) protecting it by merely a delicate 
 cover. 
 
 7. The renewal of the blood in these capillaries is 
 a result of the circulation ; the renewal of the air in 
 the cells is the result of respiration. 
 
REVIEW. 85 
 
 8. The influx of oxygen into, and the efflux of 
 carbonic acid gas and water- vapor out of, the blood 
 form the most important part of respiration. 
 
 9 The act of inspiration supplies' the lungs with 
 fresh oxygen ; that of -expiration removes carbonic 
 acid gas and water vapor from thetaa. 
 
 LESSON xix. 
 
 1 0. In inspiration a quantity of air rushes through 
 the larynx, trachea and bronchi, and passes into the 
 lungs, expanding and filling them. 
 
 11. In expiration a quantity of air is ejected from 
 the lungs by means of compression, and passes 
 through the bronchi, trachea and larynx into the 
 external air. 
 
 12. The rhythm observable in the respiratory pro- 
 cess is inspiration, expiration, pause. 
 
 13. Inspired and expired air compared : 
 
 (1.) Expired air has nearly the same tempera- 
 ture as the blood, whatever be the tempera- 
 ture of the external air. 
 
 (2.) Expired air is always filled with water- 
 vapor. 
 
 (3.) Expired air always contains more carbonic 
 acid gas and less oxygen than inspired air. 
 
 14. Coughing is a quick and forcible expiration, or 
 
 series of expirations. 
 Sneezing is the same process with the mouth 
 
 closed 
 Sighing is a slow, deep inspiration followed by 
 
 a quick and short expiration 
 
86 FIRST LESSON'S IN PHYSIOLOGY. 
 
 Laughing is a rapid succession of short and 
 
 forcible expirations, each accompanied by " 
 
 a ringing sound. 
 
 Sobbing is a series of abrupt, inspiratory acts.s 
 Snoring results from the current of expired air 
 
 striking against the soft palate, causing it 
 
 to vibrate. 
 
 15. The proper supply of oxygen forms one of the 
 three most important requirements for health. (For 
 the other two compare pp. 55, 88.) 
 
 16. The lungs and the heart compared. 
 Three points in common : 
 
 (1.) Both operate by expansion and contrac- 
 tion. 
 
 (2.) Both are involuntary organs ; that is, on 
 ordinary occasion they act independently 
 of the will. 
 
 (3.) Both are indispensable to the mainten- 
 ance of life. 
 
 Three points of difference : 
 
 (1.) The lungs contain air ; the heart contains 
 blood. 
 
 (2.) The lungs contain bronchial tubes, air- 
 cells and blood-vessels ; the heart has 
 two parts, called the right and left side, 
 each part being again divided into auri- 
 cle and ventricle. 
 
 (3.) The lungs purify the blood; the heart 
 propels the blood through the body. 
 
RELATION OF AIR 'TO THE BODY. 
 
 874 gf 
 
 LESSON XXI. 
 ( 
 
 AIR, AND ITS RELATION TO THE HUMAN BODY. I. 
 
 Wherever man sojourns, whether within doors or 
 out, whether below, above, or at the surface of the 
 earth, he requires, night and day, an incessant sup- 
 ply of air, which he mainly uses for food, and as a 
 means of cooling the body. 
 
 (Our atmospheric air is a mixture of two gases 
 nitrogen and oxygen ; only the latter is available 
 for food ; nitrogen is not utilized for the purpose by 
 the blood. Oxygen forms one-fifth of any given 
 volume of the atmosphere ; nitrogen, the remaining 
 four-fifths.) 
 
 This Lesson treats of air as a means of cooling 
 the body. 
 
 The human body, in order to properly carry on 
 the functions of life, requires a constant internal tem- 
 perature, which, in summer and winter, must be the 
 same. Experiments have shown this temperature 
 to be between 98 and 100 F. ; and, as it does not 
 vary under ordinary circumstances, this vital or ani- 
 mal heat, as it is called, must be generated in and 
 distributed through the interior of the body at every 
 instant of time. In severe cold weather the temper- 
 ature of the air may be so low that one's ears 
 or finger-ends may be cooled a few degrees be- 
 low 98, or even congeal ; but the temperature of 
 
88 FIRST LESSONS IN PHYSIOLOGY. 
 
 the interior organs and of the blood remains un- 
 changed. Should the cold be very intense, however, 
 and affect the body continuously, then the tempera- 
 ture of the blood will be reduced, and the conse- 
 quences be fatal. A decrease of five degrees below 
 the normal standard of temperature will cause the 
 vital processes to cease. 
 
 An increase in the temperature of the blood is 
 always associated with a diseased state of the body, 
 and, if not overcome, in course of time will prove 
 fatal. Such an increase occurs in typhoid fever, 
 often to the extent of eight degrees F. 
 
 A temperature not varying more than one degree 
 from 99 F., whatever be the temperature of the 
 surrounding air, is one of the three most important 
 requirements for health. 
 
 It is obvious that the maintenance of the standard 
 temperature of the body must be one of our main 
 cares. Heat may be lost I, by conduction; II, bj 
 radiation; and III, by evaporation. 
 
 I. LOSS OF HEAT BY CONDUCTION. 
 
 10. EXPERIMENT. The end of a wire held in a flame 
 has a higher temperature than its nearest part out- 
 side the flame, while the end of the wire which is 
 held in the hand is comparatively cool. We say 
 now that the wire is unequally hot ; and because of 
 this inequality of temperature, the heat commences 
 to pass from the hotter to the colder portions of the 
 wire, so that, finally, the hand can no longer hold it. 
 
RELATION OF AIR TO THE BODY. 89 
 
 In the same manner the human body transfers 
 heat to any substance in contact with it and colder 
 than itself, such as air, water or clothing. 
 
 The passage of heat from hotter to colder portions 
 of a body, or from hotter to colder adjacent bodies, 
 is called the conduction of heat. 
 
 If, by way of experiment, we were to step from a 
 heated room suddenly into an apartment whose 
 temperature was 32 F., a great deal of heat would 
 be conducted away from the body, and the loss 
 would at once be seriously felt ; but were we, in a 
 heated state, to plunge into ice-cold water, the loss 
 of heat would be far greater that is, the water 
 would take more heat from the body than the air, 
 and we should be chilled instantaneously. This 
 shows that water is a better conductor of heat than 
 air (compare First Lessons in Physics, pp. 94, 95). 
 It also explains why we take cold more easily in 
 moist and cold weather than in dry and cold. 
 
 II. LOSS OF HEAT BY RADIATION. 
 
 Familiar Facts. On a bright and calm day in 
 winter we feel the sun's rays to be quite warm, 
 although the water on the ground be freezing, and 
 the ice be dry and hard. The thermometer indicates 
 a temperature below the freezing point, but when 
 the direct rays of the sun fall on it, it rises at once, 
 indicating a far higher temperature. This shows 
 that the sun's rays pass through the air without 
 heating it, but that they heat any object, such as a 
 solid body, which stops them. 
 
 This passage of heat-rays from one body to an- 
 
90 FIRST LESSONS IN PHYSIOLOGY. 
 
 other without affecting the air through which they 
 pass is called the radiation of heat. It differs from 
 conduction, inasmuch as the radiating body is not 
 in contact with the body heated, while conduction 
 means the passage of heat from hotter to colder 
 parts of the same substance, or of adjacent bodies. 
 
 On a cold day, if a person is seated by a window 
 in a warm room, his loss of heat by radiation is only 
 partial, and, therefore, more dangerous than- an equal 
 radiation from all parts of his body, such as takes 
 place when he is walking out of doors. A partial 
 radiation may produce a cold, and, if continued, en- 
 tail serious injuries upon the system. 
 
 As the human body heats the air around it by 
 conduction, and as warm air has less specific weight 
 than cold air, currents of warmed air continuously 
 ascend along the body. These currents are interfered 
 with by the atmosphere, which constantly pene- 
 trates to the body, becomes heated at its expense, 
 and thus exerts a cooling influence upon it. Hence, 
 we feel colder when windy weather sets in, although 
 the thermometer shows no reduction of temperature, 
 
 All bodies continually tend to equalize their tempera- 
 tures by the diffusion of heat. This diffusion takes place 
 Try conduction and radiation. 
 
 III. LOSS OF HEAT BY EVAPORATION. 
 
 Familiar Facts. A few drops of alcohol or 
 ether, placed upon the bulb of a thermometer, will 
 rapidly evaporate ; this causes an immediate reduc- 
 tion of temperature, which is indicated by the ther- 
 mometer. So, snow and ice, when melting on the 
 
RELATION OF AIR TO THE BODY. 91 
 
 ground and evaporating, reduce the temperature of 
 the air. 
 
 Any substance in passing from a denser to a rarer 
 state absorbs heat; this Tieat is taken from the adja- 
 cent body, which is thereby chilled. This explains 
 the loss of heat by evaporation. 
 
 The injurious effects of 'wet feet,' and of gar- 
 ments moistened from rain, or from having been 
 worn next to the skin too long, are due to the cold 
 produced by evaporation, and also to the greater 
 conductive power of water. The skin must be kept 
 warm, and free from moisture ; garments worn next 
 to the skin should be frequently changed. A per- 
 son who, with his body heated from exertion or 
 rapid motion, and perspiring copiously, should en- 
 ter a colder atmosphere, or be exposed to a draught, 
 would lose an enormous quantity of heat, both by 
 conduction and radiation. 
 
 Diseases resulting from 4 colds ' are among the 
 most painful and dangerous. The process of ' cool- 
 ing off' should at all times be carried on slowly and 
 gradually. 
 
92 FIRST LESSORS IN PHYSIOLOGY. 
 
 LESSON XXII. 
 
 AIR, AND ITS RELATION TO THE HUMAN BODY. II, 
 
 The normal temperature of the body should be 
 maintained at all times, whether the temperature of 
 the atmosphere be low or not. This is effected (1) 
 by clothing, (2) by the bed, (3) by buildings. 
 
 1 Clothing. Our garments act like so many arti- 
 ficial skins, and thereby protect the skin from the 
 injury which would result to it were it left exposed 
 to the changing habits of our climate. They lose 
 heat in place of the skin; they sustain intense 
 cold or heat, rain and storm, in order that the deli- 
 cate vessel of the skin may not be contracted by 
 cold or expanded by heat, and its nerves not be 
 shocked. But it is not desirable to shut out the 
 .atmosphere altogether from the body, else we 
 might wear a tight-fitting India-rubber suit, or one 
 of kid-leather. In either of these the exhalation of 
 the skin (Lesson XIII) would be impeded, which 
 would be followed by dangerous consequences. 
 Besides, close-fitting garments are productive of 
 cold, because they do not envelop a sufficient quan- 
 tity of air ; this may be well shown by wearing kid 
 gloves in a cold atmosphere. India-rubber offers 
 excellent shelter from storm and moisture, but it 
 must not form an habitual garment, because it is 
 
RELATION OF AIR TO THE BODY. 93 
 
 impervious to air. Flannel permits a hundred times 
 as much air to pass through its tissue as fine leather 
 yet it is very much warmer than either leather or 
 India-rubber. 
 
 The body heats the air around it ; the air thus 
 heated heats the garments, which should retain 
 most of this heated air. The first purpose of cloth- 
 ing, therefore, physiologically considered, must be 
 to retard the outward diffusion of heat, by radiation 
 and conduction, from the body. 
 
 Kadiation, however, may be prevented by a single 
 cover. This is the case with the earth. In clear 
 nights the earth radiates its heat out into space ; 
 this radiation produces a low temperature on its 
 surface, which, under the tropics, becomes fatal to 
 travelers sleeping out of doors. In cloudy nights, 
 however, the clouds act as a screen ; the heat radi- 
 ated from the earth is, in great part, reflected back 
 to it. 
 
 If in our latitudes we wore a single garment, 
 though protecting us from the effects of radia- 
 tion, it would be powerless against losses by con- 
 duction. The outer, colder, air would constantly 
 traverse it, cool the layer of heated air around the 
 body, strike the skin and there warm itself at the 
 expense of the delicate nerves and vessels of the 
 skin. 
 
 The second purpose of clothing, therefore, must 
 be to retard the inward motion of currents of outer, 
 colder air. 
 
94 FIRST LESSONS IN PHYSIOLOGY. 
 
 Prom the preceding it is obvious that a regular 
 succession of garments is necessary ; that they, as 
 well as the air which they contain within their 
 meshes, grow colder as their distance from the body 
 increases ; and that garments generally (more espe- 
 cially the outside garments, as an overcoat,) carry on 
 upon their surface the equalization of temperature 
 between the outer, colder, air and the heated atmos- 
 phere within, in order that it may not take place on 
 the surface of the skin. 
 
 As the garments worn next to the skin are con- 
 stantly moistened by perspiration, their water- 
 absorbing qualities should be consulted. And since 
 moist fabrics are better conductors of heat than dry 
 ones, such garments must be frequently changed. 
 
 Linen is a rapid absorbent of moisture. As the 
 moisture absorbed readily evaporates, and thereby 
 produces cold, and as linen is also a good con- 
 ductor of heat, it is a favorite article of clothing in 
 summer ; but it should never be worn next to the 
 skin. 
 
 Cotton neither absorbs as much moisture, nor con- 
 ducts heat as well, as linen. It is, therefore, warmer, 
 although much cooler, than either wool or silk. 
 
 Woollen is a great absorbent, which does not 
 give up its moisture so readily as the preceding 
 fabrics. This property makes it very valuable. It 
 is a bad conductor on account of the great quantity 
 of air contained within its meshes. It also possesses 
 
RELATION OF AIK TO THE BODY. 95 
 
 ft 
 
 " *> 
 
 the**jjroperty of condensing water- vapor within its 
 tissu^, and thus produces warmth. This explains 
 why fresh flannel, put on after great exertion, feels 
 so warm. It should at all times be worn next to 
 the skin. 
 
 2. The led. This is the sleeping apparel during 
 nearly one-half of our life, and as important as cloth- 
 ing. It is made of material similar to that of gar- 
 ments, and serves the same purpose. But it must 
 be made much warmer than our clothing, because 
 (1) the body develops less heat during sleep, and 
 must yet be maintained at its standard tempera- 
 ture ; (2) the body, when not lying down, is heated 
 by currents of heated air ascending from the feet to 
 the neck, while when stretched out horizontally the 
 body is not so heated, for these currents then ascend 
 perpendicularly from the body. 
 
 3. Buildings. Dwelling houses serve the same 
 purposes as clothing, which they also resemble in 
 this, that, as a rule, they are built of badly conduct- 
 ing material. Like clothing, the walls of buildings 
 should always be permeable to air. As long as they 
 are in good condition they are easily penetrated by 
 atmospheric currents. This is evident, for we know 
 that wood, brick and stone are more or less porous, 
 and that they readily absorb water ; now, wherever 
 water can penetrate, air, being so much lighter, can 
 enter in hundredfold quantities ; the fact that we 
 never feel air pass through walls means nothing, 
 
06 FIRST LESSONS IN PHYSIOLOGY. 
 
 since currents of air moving at a rate less than 
 about 20 inches a second are not felt by the nerves. 
 Moist walls are unhealthy for the same reasons 
 as those applying to moist garments : (1) the stop- 
 page of ventilation, the pores of the walls being 
 taken up by water to the exclusion of air ; (2) the 
 cold-producing effects, owing to increased radiation 
 and conduction to heat the water ; (3) the cold gen- 
 erated by the evaporation of the moisture. 
 
 Large quantities of water are contained in the 
 mortar of the walls in newly-erected buildings. 
 Most of this water must be first removed before the 
 dwelling is fit to be inhabited. It is removed best 
 by giving it sufficient time to evaporate, and pro- 
 moting the evaporation by means of artificial heat 
 and by removing the vapor by ventilation. 
 
 Pure air is essential to health. Atmospheric 
 air depends for its purity on being washed by rain 
 and dew. It is heated and dried by the sun ; fed 
 with oxygen by plants, and by them also freed 
 of carbonic acid gas. Impure air may result from 
 (1) the want of sunlight ; (2) the want of cleanliness 
 in the household : (3) the absence of efficient venti- 
 lation ; (4) the presence of dust, smoke or decay- 
 ing matter. It is very dangerous to the lungs, and 
 although its pernicious effects upon the health are 
 generally slow, they are nevertheless sure. 
 
 Ventilation and draught may now be better un- 
 derstood. Ventilation is the imperceptible efflux of 
 air and the simultaneous imperceptible in- 
 
RELATION OF AIR TO THE BODY. 97 
 
 flux of atmospheric air. It depends (1) Upon the 
 difference of temperature between in-doors and out. 
 Thus, in severe cold weather, a room, to be well- ven- 
 tilated, must be heated. (2) The quantity of motion 
 of the atmospheric air. Strong currents of air, as 
 winds or storms, greatly facilitate ventilation. 
 (3) The size of the orifices through which the air is 
 expected to pass. When No. (1) fails, as e. g., in 
 summer, we use No. (3) mostly that is, we open 
 doors and windows. 
 
 Draught is a perceptible current of colder air 
 striking, and consequently cooling, only a portion 
 of the body. 
 
 Bead The Bazar Book of Health (The Dwelling, &c). Harpers. 
 Disease Germs. L. S. Beale. Lindsay & Blakiston, Phila. 
 Thermic Fever, or Sunstroke. Lippincott, Phila. 
 
LESSON XXIII. RE VIE W. 
 
 LESSON xxi. 
 
 1. The human body, in order to properly carry on 
 the functions of life, requires a constant internal 
 temperature. 
 
 2. A reduction or increase of the standard tem- 
 perature may, if continued, prove fatal to life. 
 
 3. A constant temperature of very nearly 100 F., 
 whatever be the temperature of the surrounding 
 air, is one of the three most important requirements 
 of health. (For the other two see Lessons XIY and 
 XIX.) 
 
 4. This temperature is maintained by interior 
 functions of the body. 
 
 5. All bodies continually tend to equalize their 
 temperatures by the diffusion of heat. This diffu- 
 sion takes place by conduction and radiation. 
 
 6. A substance passing from a denser to a rarer 
 state absorbs heat ; this heat is taken from the ad- 
 jacent body, which is thereby chilled. 
 
REVIEW. 99 
 
 7. The human body, as is seen from 5 and 6, loses 
 heat in three ways : (1) byconduction, (2) by radia- 
 tion, (3) by evaporation. 
 
 LESSON xxii. 
 
 8. The heat of the body is retained by clothing, 
 the bed and buildings. 
 
 9. Clothing protects the delicate vessels and 
 nerves of the skin from the effects of intense cold 
 or heat. They should include and contain air, be- 
 cause air is a bad conductor of either heat or cold. 
 
 10. Clothing (1) retards the outward diffusion of 
 heat (by radiation and conduction) from the body ; 
 (2) it retards the inward motion of currents of outer 
 colder air. 
 
 11. The bed must be warmer than one's garments, 
 because (1) the body develops less heat during 
 sleep, and must yet maintain its standard tempera- 
 ture ; (2) the body, when in a horizontal position, 
 is not heated by currents of heated air ascending 
 along it. 
 
 12. The walls of buildings should be permeable 
 to air, the same as clothing. 
 
 13. Moist walls are pernicious to health, because 
 (1) of the stoppage of ventilation, the pores of the 
 walls being taken up by water to the exclusion of 
 air ; (2) of the cold-producing effects, owing to in- 
 
100 FIRST LESSONS IN PHYSIOLOGY. 
 
 creased radiation and conduction to heat the water ; 
 (3) of the cold generated by the evaporation of the 
 moisture. 
 
 14. The moisture in the walls of newly-erected 
 buildings is best removed by giving it sufficient 
 time to evaporate, by promoting its evaporation 
 by means of artificial heat, and by removing the 
 water-vapor by ventilation. 
 
 15. Pure air is essential to health. Our atmos- 
 phere is washed by rain and dew. It is heated 
 and dried by the. sun ; it is fed with oxygen by 
 plants, and freed by them of carbonic acid gas. 
 
 16. Impure air may result (1) from the want of 
 sunlight ; (2) the want of cleanliness in the house- 
 hold; (3) the absence of efficient ventilation; (4) 
 the presence of dust, smoke, or decaying matter. 
 
 17. Ventilation is the imperceptible efflux of im- 
 pure air, and the simultaneous imperceptible influx 
 of atmospheric air. 
 
 18. Draught is a perceptible current of colder air 
 striking only a portion of the body. 
 
FOOD. 101 
 
 LESSON XXIV. 
 
 FOOD. 
 
 11. EXPERIMENT. Hydrogen gas may be liberated from muriatic acid 
 poured over a few small pieces of tin in a test-tube. The gas is recognized 
 by its burning with a pale, bluish flame. By connecting the mouth of the 
 test tube with a suitable tube, the gas may be conducted into a tumbler 
 filled with and inverted over water. 
 
 12. EXPERIMENT. Oxygen gas may be liberated from an ounce of pul- 
 verized potassium-chlorate mixed with a like quantity of manganese di-oxide, 
 by placing the mixture in a test-tube and applying heat. It may be recog- 
 nized by its rekindling a glowing taper ; like hydrogen, it is easily caught 
 in an inverted tumbler. 
 
 13. EXPERIMENT. Nitrogen gas maybe obtained from common air by 
 burning a short piece of candle, fastened on a fragment of board so as to 
 float on water, and inverting a glass jar over the candle. The light will 
 be extinguished, some water will rise into the jar, and nearly all the re- 
 maining gas will be nitrogen. 
 
 Carbon may be represented by a piece of coke or charcoal. 
 
 Hydrogen, oxygen, nitrogen three gases and 
 carbon a solid are the principal elementary sub- 
 stances which, when combined with each other, form 
 the materials composing the human body. 
 
 The functions of the human system cause a waste 
 of tissues. This waste must be repaired or the in- 
 dividual will die..' Since the human body is com 
 posed of combinations of carbon, hydrogen, oxygen 
 and nitrogen, it must be repaired by a supply of 
 aliments containing these materials. When an or- 
 
102 FIRST LESSONS IN PHYSIOLOGY. 
 
 ganism is deprived of proper food it commences to 
 feed upon itself. 
 
 Waste of tissue arises from the incessant work 
 which, the body performs, consisting of mechanical 
 motion, as when a person is walking or a blacksmith 
 strikes a piece of iron on the anvil ; or of vital func- 
 tions, such as breathing and digesting ; or of men- 
 tal processes, as when one is thinking or studying. 
 All such work diminishes the weight of the organ- 
 ism ; and if the labor were continued without food 
 being taken to repair the waste, the result would be 
 death. For a further illustration, suppose that a 
 man who has been carefully weighed, be placed in 
 a glass-house containing cold and dry atmospheric 
 air, and told to walk up and down in it for an hour 
 without interruption. At the end of that hour, if he 
 be weighed again, he will be found to have lost in 
 weight. This loss is balanced by the amount of work 
 he has done, viz. : 1. The mechanical labor in lifting 
 and moving the weight of his body at every step. 
 
 2. The rise in temperature, indicated by a ther- 
 mometer hung up inside of the glass-house, which 
 shows that he has heated the air around him. 
 
 3. The moisture on the inner sides of the glass, due 
 to expiration. 4. Carbonic acid gas, also due to 
 expiration, the presence of which is shown by a 
 white film of carbonate of lime on the limewater in 
 a vessel placed on the floor of the glass-house. 
 
 Food, generally speaking, is any substance adapt- 
 ed to supply the body .with material that re- 
 news lost tissue or supports some process of life. 
 
FOOD. 103 
 
 It is divided into organic and inorganic materials. 
 Organic food comprises (1) nitrogenous substances, 
 such as meat, milk, or white of an egg ; (2) fats, such 
 as butter or lard; (3) compounds of carbon and 
 hydrogen, such as starch or sugar. The last two 
 classes, when pure, contain no nitrogen. Inorganic 
 food comprises water, the most important article of 
 food, and alkalies, such as salt and phosphates. No 
 single class is generally considered sufficient ; all 
 of them are necessary to make food nutritive and 
 convenient ; a man feeding entirely upon bread and 
 sugar may ultimately be starved as surely as one 
 whose diet is composed solely of meat, or of mineral 
 water. Intuitively, we eat bread and meat, or bread 
 and cheese, bacon and beans, stuffing and fowl. 
 Persons who live largely on meat prefer it fat ; those 
 who feed mostly on vegetables consume a great deal 
 of milk, because milk contains the three classes of 
 organic food, as well as inorganic materials. 
 
 Oxygen is an article of food, as it serves to main- 
 tain important vital functions. It is the only article 
 of food which enters the system as a simple or 
 elementary body ; all the others are compounds. 
 
 Digestibility of Food. A substance may be 
 highly nutritious, but if its consistency is so great 
 that it is insoluble in the digestive fluids, it is use- 
 less as nourishment. This is the case with bones 
 and cartilages. Tasteless substances, such as com- 
 mon oil, do not digest, because they fail to pro- 
 duce secretion of saliva, an essential element in the 
 preparation of food. Many articles of food are ren- 
 
104 FIRST LESSONS IN PHYSIOLOGY. 
 
 dered nutritious by condiments, which, without 
 these, might not even have been palatable. Tea, 
 coffee and juices must be regarded as great helpers 
 to nutrition; so also a frequent change of, and 
 variety in, our bill of fare. 
 
 Irregularity in diet is a frequent cause of disease. 
 Next to it, perhaps, stands the want of the proper 
 preparation of food by cooking. The purpose of 
 cooking is : (1) to soften the food ; (2) to give it an 
 agreeable flavor. Beans, grains and many kinds of 
 fruit can not be digested in a raw state. 
 
 Hunger and Thirst. The man whom we sup- 
 posed to take exercise in a glass-house would dwin- 
 dle to nothing in due course of time unless he 
 took food to repair his waste. The imperious sen- 
 sations which remind us forcibly of the want of 
 solid and liquid aliment are hunger and thirst. To 
 satisfy the former, the body must be supplied with 
 solid food ; to satisfy the latter, with water in some 
 shape or other. 
 
 Solid Food. Over the whole world beef is justly considered the most 
 nutritious kind of flesh. Its flavor is fuller and more attractive than that 
 of other meats, and, as it has a denser structure, the volume of beef re- 
 quired for a meal need not be as large as that of other kinds of flesh. Veal 
 is inferior to beef, as it is more difficult to digest. Mutton, although a 
 lighter food than beef, is more suited to persons who take little exer- 
 cise. Pork is less nourishing than either beef or mutton. It is commonly 
 believed to be less digestible, and scientists have found that it requires more 
 time for digestion. Ham is more nearly like beef, as it contains less fat 
 than the other parts of the pig. Pork is known to be more frequently 
 diseased than other meats. Its use is most extensive in new coun- 
 tries on account of the facility in raising pigs, in preserving the meat, 
 and also on account of the difficulty in having a sufficient demand in thinly- 
 settled districts for a freshly-slaughtered ox or sheep. Fish should never 
 
FOOD. 105 
 
 take the place of beef permanently, but rather play the part of an agreeable 
 companion to, or variety of, other animal food. The nutritive qualities of 
 red-blood fish, as the salmon, are nearly as great as those of any other red- 
 blood flesh, while white fish is less nutritive. Butter depends for its flavor 
 very much upon the food of the animal from which it is derived. As lean 
 meat serves principally to produce and maintain the structures of the body, 
 the fats and they include butter mainly generate by their oxidation the 
 heat required for the vital processes. 
 
 Wheaten flour and bread are "the most important vegetable production of 
 temperate climates that upon which the life of man in these regions 
 mainly depends. Its importance rests upon several properties, by which 
 it is acceptable and good food for all ages and classes of the people. It is 
 produced abundantly and cheaply ; is easily ground and refined ; is readily 
 and thoroughly cooked ; has a mild flavor which is universally agreeable, 
 and contains nearly all the essential elements of nutrition. It is preferable 
 to any of the other great vegetable products on which men chiefly live, 
 since it is a far more agreeable food than maize, and a more nutritious food 
 than rice. It is probable that the health and mental and bodily vigor of 
 the inhabitants of temperate climes are more attributable to this food than 
 to any other single cause. " Potatoes can not be used alone, as they lack 
 mineral elements ; about three pounds of potatoes are equivalent to one 
 poiind of bread as regards nutritive contents. 
 
 Liquid Food. Water is, of all foods, whether liquid, solid or gaseous, 
 the most important. It forms about 87 per cent, of the human body. 
 Lean beef contains nearly 72 per cent, of water, veal 63, mutton 72, fat 
 pork 40, poultry 73, fish 75, wheaten bread 37, coffee and tea nearly 100. 
 To be good to the taste it must contain, as it nearly always does, a small 
 quantity of atmospheric air. Mineral matters in water render it hard ; for 
 domestic purposes it is rendered soft by boiling, or by treatment with lime, 
 soda or ammonia. Organic matter in water is harmless when existing 
 in very minute quantities ; if otherwise, it is very injurious to the system 
 and a frequent source of disease. Turbid water from wells is impure, 
 while the turpidity of water from streams simply arising from sand or the 
 soil is quite harmless. Water infected with organic matter, or offensive 
 to the smell or taste, must be rejected. Milk contains all the nutritive 
 elements, and is readily digestible. Tea is an infusion of the leaves of the 
 tea-plant, of scarcely any nutritive quality, but highly valued as a means of 
 exciting vital processes and stimulating respiration as well as perspiration. 
 Coffee is probably as little nutritious as tea; like this, it stimulates respira- 
 tion, but, unlike tea, it tends to make the skin dry. 
 
10(5 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON XXV. 
 
 DIGESTION. I. 
 [Before studying this Lesson review "Teeth," Lesson III.] 
 
 The food of plants requires no modification pre- 
 vious to its being absorbed by the vegetable organ- 
 ism. Plants feed principally on water, carbonic 
 acid, ammonia and saline substances, all of which 
 they find ready for their absorption. Man and ani- 
 mals, however, derive their food principally from 
 organic substances. They prepare it within their 
 bodies before it is absorbed by the blood; and 
 man, in addition, cooks his food. 
 
 The changes wrought upon the food in the body 
 may be divided into three parts : 1. Digestion, or 
 the proper preparation of food in the alimentary 
 canal (Lesson III), so as to fit it for absorption. 
 2. Assimilation, or the conversion of food into blood 
 and tissue 3. Excretion, or the decomposition of 
 food and its removal from the body. With the ex- 
 ception of the lungs, which absorb oxygen, the ali- 
 mentary canal is (generally) the only channel by 
 which food can pass into the blood. 
 
 The quantity of food dry, solid and nutritious 
 daily introduced into the mouth of a man of aver- 
 age size and activity is about 35 ounces, to whioh 
 must be added about a pound of oxygen gas ab- 
 sorbed by the lungs, making in all a little over 
 
DIGESTION. 
 
 107 
 
 three pounds. To this should be added the oxygen 
 which, during insalivation, mingles with the food. 
 Digestion commences immediately upon the pass- 
 age of food into the mouth before entering the 
 Fiy.22 stomach. Solid food must first be 
 crushed by the action of the teeth, 
 jaws and tongue. This part of di- 
 gestion is called Mastication. 
 
 While the structure of teeth be- 
 longs to Lesson III, it may be inter- 
 esting here to refer to the adapta- 
 tion of the teeth in different classes 
 
 Jaws of a Fish. 
 
 of animals to the food upon which the animal sub- 
 sists. Thus, in fish, the food is swallowed entire ; 
 hence, the teeth have, as a rule, the form of sharp, 
 curved spines (Fig. 22). Such teeth merely serve the 
 purpose of retaining or holding the prey. The 
 Fig.23. 
 
 Skull of a Horse. 
 
 horse has incisors in both jaws (Fig. 23), while her- 
 bivorous animals of the ruminating order have their 
 
108 FIBST LESSONS IN PHYSIOLOGY. 
 
 incisors only in the lower jaw. These incisors 
 merely serve to cut off the grass or herbs upon which 
 the animal feeds. The process of mastication is 
 performed entirely by the molars, the canines being 
 either wanting or only imperfectly developed. Car- 
 nivorous animals, such as the bear or dog, have in- 
 cisors for dividing the food, canine teeth for attack- 
 ing and retaining the prey, and molars for grinding 
 (Fig. 24). In man the teeth are so selected as to 
 combine the features of those of the herbivorous and 
 the carnivorous animals, which distinctly points to 
 the fact that his food should be composed both 
 of animal and vegetable substances. The tongue 
 has the- function of holding back the portion of 
 aliment which is about to pass down not yet wholly 
 crushed by the teeth; and any particles of food 
 which have been pushed outside of the teeth are 
 thrust back again under the teeth by the compres- 
 sion of the lips and cheeks. The tongue also crushes 
 soft substances against the palate. It is, at the 
 same time, an organ invested with special mobility 
 and acute sensibility, so as to pass judgment upon 
 the qualities, situation and degree of trituration of 
 the aliment in the mouth. The combined action of the 
 teeth, tongue, lips and cheeks results in the breaking 
 down of the food. The purpose of this is, that the 
 food shall present a large surface to the dissolving 
 action of the various fluids acting upon it. If large 
 masses were to pass down unbroken by the teeth, 
 they would scarcely be altered in the stomach, and, 
 consequently, supply nutrition imperfectly. For 
 
DIGESTION. 
 
 109 
 
 Fig.24*. 
 
 
 this and other reasons, rapid eating should be stu- 
 
 diously avoided ; it frequently causes indigestion. 
 
 Insalivation, the second part of digestion, takes 
 
 place in the mouth. It is here that the masticated 
 
 food thoroughly mixes 
 with the saliva of the 
 mouth, abundantly 
 secreted from a number 
 of salivary glands, and, 
 at the same time, min- 
 gles with air, which is 
 contained in the bub- 
 bles of the saliva. This 
 liquid contains over 990 
 parts of water in 1000 
 parts of its weight. It 
 changes a large portion of the starch, which the 
 food may contain, into sugar. 
 
 Deglutition, or the act of swallowing the third 
 part of digestion takes place after the aliment, 
 by means of mastication and insalivation, has been 
 reduced to a minute pulp, and, transferred from the 
 mouth through the oesophagus or gullet, to the 
 stomach. This downward passage is effected by a 
 successive contraction of the muscular parts around 
 the oesophagus above the food, while they are lax 
 below. Hence it is that a man can drink standing 
 on his head ; and a horse with its head lower than 
 its stomach. Food, while in the mouth, is controll- 
 ed by the will, but deglutition is not. 
 
 Skull of a Polar Bear. 
 
110 F1KST LESSONS IN PHYSIOLOGY. 
 
 LESSON XXVI. 
 
 DIGESTION. II. 
 
 Digestion in the Stomach is the fourth part of 
 digestion. The stomach (Fig. 25, p. 114) is the continu- 
 ation of the gullet, but it is much wider, and of differ- 
 ent forms in different animals. It is a sort of bag of 
 about one and a quarter square feet internal sur- 
 face, with a capacity of five pints, and a weight of 
 seven ounces, in the adult man. It has two open- 
 ings one (a) to admit food, called Cardia, and 
 which is always open ; the other (&), called Pylorus, 
 which, during stomach digestion, is firmly closed so 
 as to allow only the finest pulp to pass. On the 
 outside the bag consists of a thin membrane, next 
 to which is a muscular coat, forming the centre ; and 
 of a mucous layer, which forms the inner lining of 
 the substanc of the bag. The muscular coat is made 
 up of involuntary muscles ; it is these which per- 
 form the mechanical labor of kneading and rolling 
 about the pulp. The food is pushed on along the 
 great curvature of the stomach (on the left side of 
 the body) to the right, and thence to the left along 
 the lesser curvature. The continual rolling motion, 
 together with the continual addition of gastric juice, 
 finally reduces the food to a fine pulp of a consis- 
 
DIGESTION. Ill 
 
 tency somewhat like that of a thick soup, which is 
 called chyme. The stomach is not capadle of great 
 muscular effort; hence, it can not crush, e. g. an 
 entire grape. The violence of abdominal motion in 
 vomiting is not due to the motion of the stomach 
 alone, but to the co-operation of abdominal muscles. 
 
 Chief functions of the stomach : (1) to mix all 
 food into a pulp; (2) to dissolve the nitrogenous 
 portion of the food by means of the gastric juice 
 (see next Lesson). The conversion of starch into 
 sugar, which takes place in the mouth, is in the 
 stomach discontinued temporarily, but not sus- 
 pended, as will be seen further on. (Regarding 
 absorption in the stomach, see the next Lesson.) 
 
 Conditions favorable to stomach digestion. The 
 following are among the most important: 1. A tem- 
 perature of 100 F., nearly. Any reduction, such as 
 results from overdoses of water or ice cream, may 
 lead to serious results. When a substance, instead 
 of being digested in the stomach, is digested in the 
 intestines, the time required is vastly greater. 
 
 2. Continual motion of the walls of the stomach 
 to permeate the food with gastric juice. 
 
 3. The removal of such portions of the food as 
 are thoroughly digested. This brings the remainder 
 into better contact with the gastric fluid. 
 
 4. Perfect mastication and insalivation of the ali- 
 ment previous to its entrance into the stomach. 
 
 5. A moderate quantity of food. The stomach 
 should not be distended. 
 
 6. Regular internals between any two consecutive 
 
112 FIEST LESSONS IN PHYSIOLOGY. 
 
 meals. They should be long enough for the food of 
 one meal to have left the stomach before the next is 
 introduced. 
 
 7. No severe physical or mental exertion either 
 immediately before or after a meal. 
 
 8. A tranquil mind. 9. Bodily health. 
 10 Favorable weather. 
 
 The processes which the food has undergone be- 
 tween its first introduction into the mouth and its 
 removal from the stomach through the pylorus are : 
 (1) mastication, (2) insalivation, (3 ) deglutition, (4) 
 digestion in the stomach. 
 
 The changes wrought upon the food by these pro- 
 cesses should now be carefully reviewed. What 
 happens to the food in the stomach will be ex- 
 plained in the next Lesson. 
 
 "According to the experiments of Dr. Beaumont, liquid substances are, 
 for the most part, absorbed by the vessels of the stomach at once, and any 
 solid matter suspended in them, as in soup, are concentrated into a thicker 
 material before the gastric juice operates upon them. Solid matters are 
 affected so rapidly during health that a full meal, consisting of animal and 
 vegetable substances, may be converted into chyme in about an hour, and 
 the stomach left empty in two hours and a half. Dr. B. found that among 
 the substances most quickly digested were rice and tripe, both of which were 
 digested in an hour. Eggs, salmon, trout and venison were digested in an 
 hour and a half; tapioca, barley, milk, liver and fish in two hours ; tur- 
 key, lamb and pork in two hours and a half. Beef, mutton and fowls re- 
 quired from three to three and a half hours, and these were more digesti- 
 ble than veal. These facts were different from what was anticipated, and 
 show that prevailing notions as to the digestibility of different kinds of food 
 are very erroneous. It must be remembered, however, that easy digesti- 
 bility does not imply high nutritive power. A substance may be nutritious, 
 though so hard as not to be readily broken down ; and many soft, easily 
 digested materials may contain a comparatively small amount of nutri- 
 ment." J. H. Bennett. Physiology. Lippincott & Co., Phila. 
 
 Bead Dyspepsia. By E. P. Miller. Miller, Haynes & Co., N. Y. 
 
DIGESTION. 113 
 
 LESSON XXVII. 
 
 DIGESTION. III. 
 
 Digestion in the intestines the fifth part of the 
 process of digestion. The intestines (Fig. 25) are 
 the continuation of the stomach. They form a long, 
 narrow tube, which, like the stomach, is composed 
 of membranous, muscular and mucous coats. The 
 intestines are of different length in different orders 
 of animals. They are divided into two parts, viz., 
 the small intestine and the large intestine. 
 
 The small intestine is subdivided into the duode- 
 num, D, and the small intestine proper. Dp. The 
 order in which they follow each other is, (1) the 
 stomach, (2) the duodenum, (3) the small intestine 
 proper, (4) the large intestine. 
 
 The alimentary canal begins with the mouth and 
 terminates with the rectum Its entire length is 400 
 inches, nearly, of which about 240 inch, belong to 
 the small intestine. The -small intestine has many 
 windings, is indirectly attached to the spinal col- 
 umn, and fills the lower central portion of the ven- 
 tral cavity. 
 
 The small intestine possesses a regular motion in 
 
 the direction of its own course ; this motion is called 
 
 peristaltic, and consists of muscular contractions, 
 
 such as take place in the gullet, the purpose of 
 
 8 
 
114 
 
 FIRST LESSONS IN PHYSIOLOGY. 
 
 FIG. 25. The Digestive Appara- 
 tus (Henle, Anat). 
 
 Front View Head and Neck 
 
 turned toward the right. 
 T Trachea, t Left Liver cut off. 
 
 C Caecum. 
 
 va Vermif. Appen. 
 
 Co Colon. 
 
 R Rectum. 
 
 L Liver. 
 
 I Gall Bladder. 
 Z>/Sm. Intest. 2 Diaphragm, 
 pro., laid aside, sp Spleen. 
 
 g Gullet. 
 a Cardia. 
 S Stomach. 
 b Pylorus. 
 P Pancreas. 
 D Duodenum. 
 
DIGESTION. 115 
 
 which is, to propel the food onward to the lower 
 parts and into the large intestine. 
 
 The large intestine, about five feet long, is shorter 
 but wider than the small intestine. It has three 
 subdivisions : the ccecum, C, the colon, Co, and the 
 rectum, R. The caecum is the short portion below 
 the junction of the small intestine, and distinguish- 
 able by a vermiform appendix, v a, about three 
 inches in length. The continuation of the caecum 
 forms the colon, which rises on the right side of the 
 abdomen up to the liver. This portion of it is 
 the ascending colon. The colon then suddenly turns 
 at a right angle and crosses over to the left side of 
 the body ; this horizontal part of it is called the 
 transverse colon; finally, it makes a sudden turn 
 downward and backward along the left side of the 
 body, where, accordingly, it is called the descend- 
 ing colon, which is succeeded by the rectum, K. The 
 large intestine is readily recognized by its width, its 
 stretching capacity and its many folds and pouches. 
 Its motions are far slower than those of the other 
 intestine, and scarcely ever result in actual dis- 
 placements of the parts with reference to each other, 
 such as take place regularly in the small intestine. 
 
 DIGESTIVE FLUIDS. 
 
 1. The Saliva, the action of which was explained 
 on page 109. 
 
 2. The gastric juice. The interior coa't of the 
 stomach contains a great number of glands which 
 are open upon its surface. Some of these are in the 
 
116 FIRST LESSONS IN PHYSIOLOGY. 
 
 vicinity of the pylorus, and secrete a mucous sub- 
 stance which covers the interior surface of the 
 stomach, and serves to envelop undigested pieces 
 of food so as to facilitate their passage through the 
 intestines. The others, which form by far the greater 
 number, secrete a clear acid liquid, the gastric juice. 
 This fluid has an extraordinary solvent power on 
 albuminous and other substances ; one part of it in 
 60000 parts of water will be sufficient to exert this 
 power. It does not act upon fatty substances fur- 
 ther than liquefying them. It is readily precipitated 
 by alcohol ; this may explain the pernicious effect 
 upon the stomach of alcoholic drinks taken in im- 
 moderate quantities. The churning motion of the 
 stomach, together with the solvent action of the gas- 
 tric juice, reduces the food to cliyme, which passes 
 through the pylorus into the duodenum, and is 
 shortly afterward mixed with bile and pancreatic 
 juice. The stomach is the part in which the food 
 undergoes its most important change. 
 
 3. The Bile is a brownish-yellow, very bitter 
 liquid secreted by the liver (L, Fig. 25). The liver 
 is the largest gland in the body ; it weighs from 50 
 to 60 ounces, has a dark-red color, and lies on the 
 right side of the body. Its upper part is connected 
 with the diaphragm, its lower touches the intes- 
 tines. The liver (1) secretes bile, and (2) modifies 
 sugar for purp9ses which this has to serve, The 
 bile accumulates in a reservoir, called the gall-blad- 
 der, from which, whenever the duodenum is dis- 
 tended by chyme coming from the stomach, it flows 
 
" DIGESTION. 117 
 
 into the duodenum, to mingle with the chyme. Bile 
 contains waste materials which it has taken from 
 the blood ; it must, therefore, be conducted out of 
 the system. If prevented from entering the duode- 
 num it congregates in the blood, producing jaundice 
 and acting then as a poison. Should some of it hap- 
 pen to be thrown into the stomach, digestion there 
 would cease at once ; nausea, vomiting, the usual 
 bilious symptoms, would occur. % It acts also as -a 
 solvent of the fatty portions of food, and as a stimu- 
 lant to the action of the intestines. Chyme after its 
 union with bile, is usually called chyle. 
 
 Chyme, as it leaves the stomach, is composed of 
 
 (1) Albuminous matter, broken down, partly dis- 
 solved, partly dissolving, and, it may be, partly un- 
 dissolved. 
 
 (2) Fatty matter, broken down, but not dissolved. 
 
 (3) Starch, being slowly converted into sugar, and 
 as fast as it becomes sugar dissolving in the fluids 
 of the mixture. 
 
 (4) Gastric juice, mixed with substances 1, 2, 3, 
 and liquids, and such portions of aliment as are un- 
 digestible. 
 
 4. The Pa/ricreatic Juice is a clear, colorless 
 liquid, distinguished (1) by its great capacity for 
 digesting fats after they have become fluid by the 
 warmth of the stomach ; (2) by its dissolving albu- 
 minous substances. It is secreted from a gland, P, 
 about seven inches long, having the form of a bunch 
 of grapes, and generally resembling the salivary 
 glands of the mouth. This juice also enters the 
 
118 FIRST LESSONS IN PHYSIOLOGY. 
 
 duodenum. The salivary glands and the pancreas 
 are readily influenced by the nervous system ; thus, 
 the sight, or smell, or the mere thought of food may 
 prompt the salivary glands to pour saliva into the 
 mouth, or, in common language, cause " the mouth 
 to water." 
 
 5. The Intestinal Juice, a thin fluid, is secreted 
 from minute glands on the interior surface of the 
 small intestine ; its business seems to be to digest 
 albuminous matter which has escaped the action of 
 the gastric juice. The main office of the small in- 
 testine is to digest fat. Intestinal juice is also 
 secreted from the colon. 
 
 The quantity of these five liquids generated daily 
 has been estimated at 22 pounds, nearly, of which 
 that of the gastric juice amounts to about 14 pounds. 
 It is plain that their office is to dissolve the food and 
 act chemically upon it. Each of them seems to have 
 its special function, and yet none is exclusively 
 directed to one object. They all aid each other, 
 and are in turn assisted by the peristaltic motion of 
 the intestines, which thoroughly mixes the food 
 with them, and propels the chyle from above down- 
 ward through that portion of the alimentary tube 
 which succeeds the stomach. The undigested masses 
 collect in the rectum to be properly removed. 
 
 Bead Constip. of Bowels. By S. B. Birch. Lindsay & Blakiston, Phila. 
 
ASSIMILATION. 119 
 
 LESSON XXYIII. 
 
 ASSIMILATION. 
 
 Chyme and chyle are merely digested food. Both 
 are in the alimentary tube ; one is in the stomach, 
 the other in the intestines. As yet they are stran- 
 gers to the system that is to say, they do not form 
 part of it. 
 
 The oxygen of the air which enters the lungs 
 rapidly burns up the particles of waste tissue which 
 are thrown into the lungs by the venous blood. 
 Now, this waste matter must be replaced by fresh 
 particles, else the vital processes speedily cease. 
 In other words, at every instant of life a quantity 
 of animal tissue is dying, and must at the next 
 instant be replaced. If no freshly-digested food is 
 at hand, as during disease, the burnt up particles 
 of the body are replaced, first, by the fat of the 
 tissues, and hence the sunken appearance of the 
 eyes and cheeks ; or next, by the flesh of the tis- 
 sues themselves, which results in emaciation, and 
 finally in death, unless cure can be effected. Thus, 
 death and life are intimately associated and depen- 
 dent upon each other in the living organism. 
 
 The question now arises, How is the digested 
 aliment converted into blood so as to be distributed 
 in this form over the entire body, and to replace 
 waste matter in fact, to furnish the material for 
 the growth and maintenance of the body ? The an- 
 
120 FIRST LESSONS IN PHYSIOLOGY. 
 
 swer is: The chyle throughout the course of the 
 alimentary canal is taken up by capillaries and 
 special minute vessels called chyle-vessels or lac- 
 teals, and conveyed into the circulation at large. 
 With the aid of respiration, it is then made into 
 nourishing blood. The process of taking up the 
 chyle forms part of the process of absorption. 
 
 Absorption. The object of this process is, (1) to 
 supply the blood with fresh materials ; (2) to remove 
 such particles as have accomplished their mission 
 in the body. Absorption, then, has a twofold char- 
 acter : it absorbs essentials from without the body 
 and carries them to the blood; it absorbs waste 
 materials from within the system and conveys them 
 outside the body. Absorption is mainly carried on 
 by two distinct sets of vessels, viz., blood vessels or 
 capillaries, and lacteals or lymphatics, also called 
 absorbents. The former are abundantly spread over 
 the interior surface of the stomach, and both the 
 small and large intestines; the latter only in the 
 intestinal canal, but most numerously in the small 
 intestine. Both sets of vessels form a perfect net- 
 work, completely covering the interior surface of 
 the intestinal canal ; in the small intestine this net- 
 work is closer to the chyle than anywhere else. 
 
 Absorption by Blood Vessels. The minute blood- 
 vessels and capillaries in the mucous coat of the 
 stomach and intestines (Fig. 26) absorb at b and c 
 completely digested aliment ; this substance is so 
 finely divided as to readily pass through the walls 
 of the blood-vessels in the manner, roughly speak- 
 
ASSIMILATION. 
 
 121 
 
 ing, of water passing through (from without to the 
 interior of) the walls of a hollow tube made of 
 blotting-paper. The blood at A is arterial ; on its 
 passage through the capillaries, 5 and c, it absorbs 
 chyle (together with waste materials), which renders 
 it venous; through a it descends into vein Y, to 
 be ultimately conveyed to the lungs. The blood- 
 vessels are not very particular in the choice of fluid 
 particles ; they absorb nearly all kinds except the 
 fatty portions. Water, and similar beverages, are 
 believed to be absorbed by the blood-vessels of the 
 stomach without passing into the duodenum. 
 
 Transverse Section of Mucous Membrane of Colon. 
 
 A Artery. V Vein, a a Descending Veins. b b Venous Net on 
 
 Inner Surface, c Capillaries in Mucous Membrane. 
 
 Absorption by the Lacteals is carried on in the 
 same manner. It is rendered most effective in the 
 small intestine, because the interior wall of this intes- 
 tine presents a larger surface to the chyle as it passes 
 
122 
 
 FIRST LESSONS IN PHYSIOLOGY. 
 
 by. This greater extent of surface is owing to the 
 fact that the mucous membrane which forms the 
 interior surface, is folded into a great abundance of 
 
 Ft a. 2 7. 
 
 Transverse Section of the Duodenum of a Calf. 
 
 I Villi. 2 Interior Chyle-Vessels. 3 Glands. 4 Exterior Chyle- Vessels 
 or Lacteals. 5 6 Muscular Coat. * Valvular Chyle-Duct. 7 Skin. 
 
 conical projections, called mill (Fig. 27, 1), some- 
 what resembling the velvety projections of a Turk- 
 
ASSIMILATION. 123 
 
 ish towel. From the villi the absorbed materials 
 pass through the interior chyle-vessels, 2, and 
 through glands, 3, to the exterior chyle-vessels or 
 lacteals, 4. These vessels gradually increase in size, 
 and on leaving the intestine obtain the valvular 
 structure of veins. This prevents any absorbed 
 chyle from flowing back to the villi. The way 
 in which each tillus imbibes the chyle is ex- 
 plained thus : the villi have minute muscles which 
 cause them alternately to contract and expand ; at 
 every expansion each villus fills with chyle ; at 
 every contraction it squeezes its contents into the 
 lymphatic vessels beyond. The villi maybe com- 
 pared to the delicate root-fibres of plants, which are 
 spread in the ground for the purpose of absorbing 
 food for the plant ; like the villi, these vegetable 
 fibres are without openings, and yet, as is known 
 from the fact that drooping leaves revive again after 
 a shower on a hot day, they are capable of absorp- 
 tion. The special function of the villi seems to be 
 the absorption of the fatty portion of the chyle, 
 although they absorb also other materials. The 
 villi are found only in the small intestine. 
 
 The lymphatic glands receive the chyle from the 
 lymphatic or chyle-vessels (Fig. 27, *) mentioned 
 above. The largest of these glands is the spleen 
 (Fig. 25), situated on the left side of the abdomen. 
 The lymphatic glands are widely distributed in the 
 body. The chyle on passing through them under- 
 goes some change, and on leaving them it flows into 
 the thoracic duct. 
 
124 
 
 FIRST LESSONS IN PHYSIOLOGY. 
 
 The thoracic duct (Fig. 28) is a tube of the width 
 of a goose-quill, nearly, which receives the chyle of 
 the lymphatic vessels and glands, and empties it 
 into a vein on the left side of the chest, near the 
 Fiq.28 heart. A similar, smaller 
 
 [tube likewise throws its 
 contents into a vein on the 
 right side of the chest, 
 near the heart. Thus, the 
 lymphatic vessels are the 
 carriers of the chyle on its 
 way to the blood ; they 
 act like veins in this, that 
 they contain valves to 
 make their contents How 
 in one direction only ; with 
 one end they terminate in 
 two ducts, which open into 
 the large veins and finally 
 into the heart ; at the 
 other end they terminate 
 in microscopic branches or 
 lymph-capillaries, which 
 are distributed throughout 
 the tissues of the body. 
 The villi form part of 
 these lymph - capillaries. 
 The lymphatic vessels of 
 the intestinal canal pass 
 by the name of lacteals, because their contents 
 ^resemble milk in appearance ; there is no difference 
 
 The Thoracic Duct. 
 
 
ASSIMILATION. 125 
 
 between lacteals and lymphatics. It should be 
 borne in mind that there are blood-vessels and 
 capillaries within each villus as well as around the 
 villi, which, as before mentioned, carry on absorp- 
 tion. 
 
 From the preceding it is evident that man and 
 the higher vertebrates have, in addition to the in- 
 tricate system of arteries and veins, another system 
 of vessels, called the lymphatic system. This con- 
 tains a fluid called lymph, which is chyle altered 
 by the lymphatic glands. As the blood-vessels have 
 blood-capillaries, so the lymphatic-vessels have 
 lymph-capillaries near the skin ; these widen into 
 lymph-vessels toward the interior of the body. 
 
 Bead Science Lectures. First Series. Heywood, Manchester 
 
126 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON XXIX. REVIEW. 
 
 LESSON xxiv. 
 
 1. The human body is composed largely of com- 
 binations of carbon, nitrogen, hydrogen and oxy- 
 gen ; hence, our food must contain these elements. 
 
 2. Waste of tissues is due to the incessant work 
 performed by the body ; most of this work consists, 
 during life, of (1) the mechanical labor in lifting 
 and moving the body ; (2) the maintenance of the 
 standard of temperature ; (3) secretion of moisture 
 and carbonic acid. 
 
 3. Food may be called any substance adapted to 
 supply the body with material that renews lost 
 tissue or supports some process of life. 
 
 4. Food consists of organic and inorganic mate- 
 rials. 
 
 5. Organic food comprises (1) nitrogenous sub- 
 stances , (2) fats ; (3) compounds of carbon and 
 hydrogen such as sugar or starch. 
 
 6. Inorganic food comprises water, and alkalies 
 such as salt and phosphates. 
 
 7. Substances of too great consistency, or such as 
 are tasteless, are indigestible. 
 
 8. The purposes of cooking food are to soften it 
 and to give it an agreeable flavor. 
 
REVIEW. 127 
 
 LESSON xxv. 
 
 9. The changes wrought upon the food in the 
 body are (1) digestion, or the proper preparation of 
 food in the alimentary canal ; (2) assimilation, or 
 the conversion of food into blood and tissues ; (3) 
 excretion, or the decomposition of food. 
 
 10. Digestion comprises (1) mastication, (2) in- 
 salivation, (3) deglutition, (4) stomach-digestion, (5) 
 digestion in the intestines. 
 
 11. The chief functions of the stomach are (1) to 
 mix the food into a pulp ; (2) to dissolve the nitro- 
 genous portion of the food by means of the gastric 
 juice. 
 
 12. The chief conditions favorable to stomach- 
 digestion are (1) a temperature of 100 F., nearly ; 
 
 (2) continual motion of the walls of the stomach ; 
 
 (3) the removal of thoroughly digested portions of 
 food from the stomach ; (4) previous perfect masti- 
 cation and insalivation of the food ; (5) a moderate 
 quantity of food; (6) regular intervals between 
 meals ; (7) no severe physical or mental exertion 
 immediately before or after a meal ; (8) a tranquil 
 mind ; (9) bodily health ; (10) favorable weather. 
 
 13. The processes undergone by the food between 
 its first introduction into the mouth and its removal 
 from the stomach through the pylorus are (1) mas- 
 tication, (2) insalivation, (3) deglutition, (4) diges- 
 tion in the stomach. 
 
128 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON xxvi. 
 
 14. The part of the alimentary canal succeeding 
 the stomach is the intestines. They are divided 
 into the small and the large intestine. 
 
 15. The small intestine comprises the duodenum, 
 and the small intestine proper. 
 
 16. The large intestine comprises the caecum, colon 
 and rectum. 
 
 17. The small intestine has peristaltic motion. 
 
 18. The digestive fluids are (1) the saliva, (2) the 
 gastric juice, (3) the bile, (4) the pancreatic juice, 
 (5) the intestinal juice. 
 
 19. Functions of the saliva : 
 
 (1) Softening the food ; 
 
 (2) Converting starch into sugar : 
 
 (3) Mingling the food with air. 
 Function of the gastric juice : Dissolving al- 
 buminous and other substances. 
 
 Functions of the bile : 
 
 (1) Absorbing waste material from the 
 
 blood ; 
 
 (2) Dissolving fatty portions of the food ; 
 
 (3) Stimulating the action of the intestines. 
 Functions of the pancreatic juice : 
 
 (1) Digesting fats ; 
 
 (2) Dissolving albuminous substances. 
 Function of the intestinal juice (probably): 
 
 Digesting albuminous matter. 
 
 20. The food undergoes its most important change 
 in the stomach. When leaving the stomach it is 
 called chyme. 
 
BE VIEW. 129 
 
 
 
 21. Chyme is composed of (1) albuminous matter, 
 (2) fatty matter, (3) starch, (4) gastric juice. 
 
 22. After its union with bile, chyme is usually 
 called chyle. 
 
 23. The object of absorption is (1) to supply the 
 blood with fresh materials ; (2) to remove waste 
 particles. 
 
 24. Absorption is effected by blood-vessels (capil- 
 laries) and by lacteals (or lymphatics). 
 
 25. Absorption by blood-vessels takes place chiefly 
 in the stomach and the intestinal canal. The so ab- 
 sorbed materials are conveyed to veins. 
 
 26. Absorption by lacteals takes place in the 
 small intestine by minute vessels called villi ; these 
 lead the absorbed chyle into the lacteals or lymph- 
 atic vessels, whence it is conveyed through the 
 lymphatic glands to the thoracic duct, and thence 
 thrown into veins. 
 
 27. The lymphatic system of the body has its 
 ramifications throughout the body similar to the 
 system of blood-vessels, from which it differs in this, 
 that its fluid is lymph, and flows in only one direc- 
 tion. 
 
 28. By the aid of respiration, the chyle is finally 
 made into blood. 
 
 29. The want either of proper food or of proper 
 digestion destroys one of the three most essential 
 requirements for health, viz., the proper composi- 
 tion of the blood. 
 
130 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON XXX. 
 
 THE NERVOUS SYSTEM I. THE DIFFERENT PARTS. 
 
 General Remarks. We have become acquainted 
 with the various bones and tissues which compose 
 the structure of the body ; with some of the mus- 
 cles which move the body ; with the alimentary 
 canal and its secretions which convert food into 
 nutriment ; with the organs of circulation the 
 heart, the blood-vessels, the lymphatics distribut- 
 ing nutriment all over the body ; and with several 
 organs serving to withdraw waste material from 
 the body, such as the skin and the lungs. We 
 must now gain an insight into a powerful organ, 
 called the nervous system. It is distinct from all 
 other systems in the body. The following are its 
 functions : 
 
 1. It connects the different portions and organs 
 of the body into an organic unit or whole. Thus, 
 a violent shock to the nervous system, such as 
 great anger or fear, may cause increased action 
 of the heart, an accelerated pulse and immediate 
 loss of consciousness. Here, then, the nervous sys- 
 tem acts upon the blood-vessels; these act upon 
 the muscles, and this combined action causes not 
 only single portions of the body to succumb, but 
 the entire body as a unit. 
 
THE NERVOUS SYSTEM. 131 
 
 2. It animates, or governs, all movements of the 
 muscles, whether these be voluntary or not. Thus, 
 when a person endeavors to resist a yawn, to repress 
 laughter or tears, a distinct exertion of muscles is 
 requisite for his effort. This is voluntary motion 
 prompted by an act of his will; whereas, the 
 churning motion of the stomach is an example of 
 an involuntary movement governed by the proper 
 nerves. 
 
 3. It regulates the temperature, nutrition and 
 secretion of the body. Thus, sudden fear often pro- 
 duces a chilling effect in lowering the temperature 
 of the skin ; weakness of the nervous system nearly 
 always impairs the digestive process ; intense an- 
 guish frequently causes increased perspiration. 
 
 4. It controls the processes of nutrition. This 
 may be proved by the fact that the injury of a nerve 
 leading to a tissue is frequently followed by the 
 waste or destruction of the tissue. 
 
 5. It receives impressions, which are communi- 
 cated by its terminal branches. Lateral pressure 
 against the eye-ball causes a luminous impression 
 or image ; this is owing to the pressure exerted 
 upon the delicate terminal branches of the optic 
 nerve (Lesson XXXIV). 
 
 6. It conveys impressions to different portions of 
 the body. In leaping, if a person alights upon the 
 heel, he will feel shocking pains in the back part 
 of the head ; the impression made at the foot is, by 
 the nerves, conveyed to the head. 
 
132 FIRST LESSONS IN PHYSIOLOGY. 
 
 7. It can generate influences which no other organ 
 or system can produce, such as sight, smell, taste, 
 etc., etc. In virtue of this function, it puts the body 
 in direct communication with the outer world. This 
 is evident, for a living being without the senses of 
 sight, smell, taste, hearing, touch and sensibility, if 
 existing at all, would be utterly unconscious of the 
 world around him. 
 
 The performance of all these functions is com- 
 prised under the term Innervation. 
 
 The nervous system, although a continuous sub- 
 Stance, is conveniently subdivided into two sys- 
 
 Ch 
 
 Mo 
 
 The Brain (side view). 
 Cb Cerebrum. Cbl Cerebellum. Mo Medulla Oblongata. 
 
 terns : 1, the cerebro- spinal system, and 2, the sym- 
 pathetic system. The former comprises the cerebro- 
 spinal axis, that is, the brain and the spinal cord, 
 together with the cerebral and spinal nerves which 
 emanate from this axis. The sympathetic system 
 
THE NERVOUS SYSTEM. 133 
 
 contains the chain of sympathetic ganglia and the 
 nerves which they give off. 
 
 The Brain (Fig. 29) is a very soft substance, 
 forming in man the enlarged upper terminus of the 
 spinal cord. It is encased in the cavity of the cra- 
 nium, which it fills, and from which it is difficult to 
 be extracted entire. The brain substance of man 
 generally varies in weight from 40 to 60 ounces, and 
 it is universally admitted that, as a rule, the quan- 
 tity of brain substance corresponds to the intellec- 
 tual powers of the individual, although it is be- 
 
 Fig.30 
 
 400 
 
 i 
 
 Two Nerve Cells and Nerve Fibres. From the Brain. 
 (Magnified 400 times.) 
 
 lieved that the quality of this substance also plays 
 an important part. The brain consists of cells and 
 fibres (Fig. 30), which are rendered visible only by 
 a good microscope. The brain is divided into the 
 large brain or cerebrum, the small brain or cerebel- 
 lum only one-eighth as large as the former and 
 the enlarged spinal cord or medulla oblongata. The 
 cerebrum in man and apes entirely covers the cere- 
 
FIRST LESSONS IN PHYSIOLOGY. 
 
 r.3l. 
 
 bellum. The cerebrum and cerebel- 
 lum consist each of two hemispheres, 
 one on the right, the other on the 
 left side. The surface of the cere- 
 brum is covered with a great many 
 foldings and windings or convolu- 
 tions, irregular in form and direction ; 
 these are separated from each other 
 by deep furrows. The cerebellum 
 also has convolutions, but they are 
 of a more regular form and direction. 
 
 The spinal cord (Fig. 31) is the 
 downward continuation of the 
 medulla oblongata. It is a soft sub- 
 stance contained in a bony cavity, 
 formed by the vertebral column or 
 back-bone (Lesson II). It extends 
 nearly to the sacrum ; it is furrowed 
 like the brain into two lateral, sym- 
 metric parts. Between these two 
 parts that is, in the centre of the 
 cord and through its entire length 
 runs a fine canal, which originates in 
 a point between the cerebellum and 
 the medulla oblongata. 
 
 The cerebro -spinal nerves originate 
 in both the brain and the spinal 
 cord, whence they ramify and spread 
 all over the body (Fig. 32). They 
 have the form of fibres and cells. A 
 nervous fibre is often made up of 
 minute tubes ; each tube contains a 
 
 The Spinal Cord, front view, with the projecting necves cut off. 
 
THE NERVOUS SYSTEM. 
 
 135 
 
 peculiar transparent, semi-solid substance which 
 contains a thick fluid. The nervous fibres terminate 
 
 in the organs to 
 which they lead, 
 and there form 
 terminal branches. 
 The nervous tube's 
 vary in size from 
 one-thousandth of 
 an inch to much 
 smaller sizes ; in 
 the spinal cord 
 they are much 
 smaller ; in the 
 brain they are 
 smallest. 
 
 The sympathetic 
 system consists, 
 like the brain, of 
 cells and fibres. It 
 is situated in front 
 and at the sides of 
 the spinal column ; 
 its ganglia or nerve- 
 cells are con- 
 nected with one an- 
 other, and with the 
 spinal nerves by 
 nerve cords. The 
 
 The Nervous System. nerves given off 
 
 from these ganglia chiefly follow the course of the 
 
136 FIKST LESSONS IN PHYSIOLOGY. 
 
 blood vessels, and are copiously distributed over 
 the heart and about the stomach. 
 
 The nervous system appears to be composed of 
 two distinct substances the gray and the white. 
 In the cerebrum and cerebellum the white substance 
 is contained within the gray ; in the medulla oblon- 
 gata and spinal cord the gray substance is enclosed 
 in the white. The nervous fibres and tubes are 
 white ; the cells are gray. 
 
 The central organ of the nervous system is the 
 gray substance. This has been admitted by even 
 those who used to think that the intellectual pow- 
 ers had no connection whatever with the nervous 
 system. All parties agree that the gray substance 
 evolves ^nervous power, while the white mainly serves 
 to conduct nervous power. If the white material of 
 the nervous system be compared to a network of 
 telegraph wires spread over a large extent of territory 
 engaged in war, then the gray substance may be 
 likened to the controlling power at headquarters 
 that is, the commander-in-chief. From all parts 
 telegrams will be sent and transmitted to him along 
 the wires stating the condition of affairs, while he 
 not only sends and transmits messages, but makes 
 his own combinations and plans, and forwards his 
 orders to distant points along the 4 wires. 
 
THE NERVOUS SYSTEM. 137 
 
 LESSON XXXI. 
 
 THE NERVOUS SYSTEM II. FUNCTIONS OF THE DIF- 
 FERENT PARTS. 
 
 The Functions of the Brain. The thin layer of 
 gray matter upon the hemispheres of the larger and 
 smaller "brain is intimately associated with mental 
 operations. The reason for the convolutions and 
 fissures on the surface of the brain is evident: 
 they cause the layer of gray matter to be more 
 extensive, and, consequently, other things being 
 equal, to increase in quantity with the increase 
 of convolutions and fissures. There are strong 
 reasons why the main function of the cerebral 
 hemispheres, and more especially that of the gray 
 matter, seems to be the manifestation of intellectual 
 powers and of powers of the will, viz. : 
 
 1. In the animal kingdom, there is generally a 
 correspondence between the quantity of gray mat- 
 ter, depth of convolutions, and the sagacity of the 
 animal. 
 
 2. The gray matter of the brain is much more 
 smooth during the first period of the infant's life, 
 and its increase corresponds with the development 
 of intelligence. 
 
 3. In diseases which have been known to com- 
 mence at the circumference of the brain, and to 
 
138 FIRST LESSONS IN PHYSIOLOGY. 
 
 pass toward the centre, medical observations have 
 found that the faculties of the mind are affected 
 first; while in those diseases which commence in 
 the central parts of the brain, and thence pass 
 toward the circumference, they are affected last. 
 
 4. Experiments upon animals show that when the 
 brain is gradually sliced away, the animal grows 
 more dull and stupid as the quantity of brain cut 
 away increases. 
 
 Mental Derangement may be caused by (I) im- 
 perfect nutrition of the brain; (2) insufficient, or 
 excessive flow of blood toward the brain ; (3) a per- 
 verse condition of the blood ; (4) prolonged sleep- 
 lessness; (5) deep affliction or despondency. The 
 usual symptoms of progressing derangement are 
 weakened attention and loss of memory, which 
 should be promptly met by avoidance of physical or 
 nervous excitement, and by proper attention to the 
 body. Insanity, a more continuous state of men- 
 tal derangement, often springs from like sources, but 
 sometimes from hereditary predisposition. Insanity 
 is characterized by lack of appreciation of the proper 
 relations between the self and the external world. 
 
 As persons can live though one of their lungs 
 may be seriously injured, so life is not necessarily 
 cut off in case one of the cerebral hemispheres has 
 been damaged. 
 
 The functions of the cerebellum, although not dis- 
 tinctly known as yet, seem to be the regulation of 
 muscular movements. 
 
THE NERVOUS SYSTEM. 139 
 
 The function of the medulla oblongata consists 
 in generating and controlling the motions of respira- 
 tion and deglutition. The brain, cerebellum and the 
 spinal cord can be sliced away one after the other 
 without immediately , destroying life; whereas, an 
 interference with the medulla oblongata is followed 
 by instantaneous death. 
 
 Functions of the spinal cord. 1. To transmit 
 sensitive impressions from its outer nerves to the 
 brain. 2. To transmit the manifestations of the. will 
 from the brain to the spinal-motor nerves, which 
 result in muscular activity. 3. To originate nerve- 
 force independently of the brain whenever a stimu- 
 lus is applied. Thus, when a stimulus, such as a 
 drop of acid, is applied to the upper leg of a 
 decapitated frog, he brings the toes of the corre- 
 sponding foot to the place to wipe off the acid, but he 
 will not leap away. In this case an impression 
 has been made upon a sensitive nerve leading to 
 the spinal cord ; this sensitive or sensory nerve 
 conveyed the impression to the spinal cord, the 
 spinal cord made response to the impression through 
 a motor nerve, and this response resulted in the re- 
 flex action of the foot. So when, independent of any 
 influence of the brain, a small piece of bread is passed 
 into the gullet by voluntary motion, it will be urged 
 onward to the stomach by involuntary motion that 
 is, by the reflex action of the spinal cord. The bread 
 here acts as an exciting stimulus upon the spinal 
 marrow, which generates motor power ; this motor 
 power is 'reflected' back and produces the invol- 
 
140 FIRST LESSONS IN PHYSIOLOGY. 
 
 untary movements or reflex action of the muscles 
 whose sensitive fibres were stimulated. 
 
 T he functions of the sympathetic system are not 
 fully known as yet. It would appear, however, that 
 while it is intimately connected with the other divi- 
 sions of the nervous system, it presides over the 
 actions of the alimentary canal, the glands, the 
 blood-vessels and the heart. The heart may be 
 removed from the body, and yet its rhythmical 
 movements will continue for a number of minutes. 
 This independent motor power on the part of the 
 heart can only be explained by the existence of 
 sympathetic ganglia or centres linked together by 
 delicate nerve filaments, constituting of themselves 
 a distinct nervous system. 
 
 Functions of Nerves. If the nerve of a tooth be 
 divided, the tooth has lost its sensibility. If the 
 nerves leading to the biceps be severed, this muscle 
 loses its motor power ; it will no longer move the 
 forearm. If these nerves be exposed in their course 
 and irritated, the biceps will be thrown into violent 
 movements, and intense pains experienced as com - 
 ing from the biceps. These facts show that the nerves, 
 generally speaking, are endowed with motor and 
 sensory properties. That is to say, the nerves ena- 
 ble us to seize ordinary sensations and to execute 
 acts of motion. 
 
 There are nerves which are specially engaged in 
 motion, and others, such as the optic nerve, which 
 generate merely sensations. Either class may be 
 injured without any damage to the other. Thus, a 
 
THE NERVOUS SYSTEM. 141 
 
 blind man rolling his eyes, shows that, though his 
 optic nerve is blighted, the motor nerves are in full 
 function. SD a limb may be paralyzed that is, 
 deprived of all motion and yet be very sensitive. 
 If a motor nerve be divided, and a galvanic current 
 applied to the portion of the nerve connected with 
 the muscle, the muscle contracts. This shows that 
 motor nerves act like telegraphic wires. 
 
 Cases have been known where soldiers com- 
 plained of pain in their limb which had long before 
 been amputated. This is evidence that sensory 
 nerves act like insulated wires, and, besides, that 
 we refer pain and all other sensations to the parts 
 which are supplied with nerves ; we suppose the 
 sensation to exist in the direction from which the 
 nerves communicate it. 
 
 The nerves leading from the brain to the eye, ear, 
 etc., etc., are in pairs ; also those originating in 
 the spinal cord. The latter are distributed nearly 
 over the whole body, and are endowed with both 
 motor and sensory properties. 
 
 Bead Brain and Mind. Am. Instit. Lect. N. Y. Tribune, 1873. 
 
 Bead Dynamics of Nerve and Muscle. C. B. Radcliffe. Macmillan & 
 Co. 
 
142 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON XXXII. RE VIE W. 
 
 LESSON xxx. 
 
 1. Functions of the nervous system : 
 
 (1) It connects the different parts and organs 
 
 of the body into an organic unit or whole. 
 
 (2) It animates or governs all movements of 
 
 the muscles, whether voluntary or not. 
 
 (3) It regulates the temperature, nutrition and 
 
 secretion of the body. 
 
 (4) It controls the processes of the organic life 
 
 of the body. 
 
 (5) It receives impressions which are generated 
 
 by its terminal branches. 
 
 (6) It conveys impressions to different portions 
 
 of the body. 
 
 (7) It can generate influences which no other 
 
 organ or system can produce, such as 
 sight, smell or taste. By means of this 
 function, it puts the body in direct com- 
 munication with the outer world. 
 
 2. The nervous system is subdivided into the 
 cerebro- spinal system and the sympathetic. 
 
 3. The brain is divided into the cerebrum, tke 
 cerebellum and the medulla oblongata. 
 
 4. The nervous system appears to be compqsed 
 of two distinct substances, the gray and the white. 
 
REVIEW. 143 
 
 5. The gray substance is the central organ of the 
 nervous system. 
 
 LESSON xxxi. 
 
 6. The main functions of the cerebrum seems to 
 be the manifestation of intellectual powers and of 
 the will. 
 
 7. The functions of the cerebellum seem to consist 
 in the regulation of muscular movements. 
 
 8. The function of the medulla oblongata is to 
 generate and control the motions of respiration and 
 deglutition. 
 
 9. The functions of the spinal cord are (1) to 
 transmit sensitive impressions from its outer nerves 
 to the brain ; (2) to transmit the manifestations of 
 the will from the brain to the spinal- motor nerves ; 
 (3) to originate nerve-force independently of the 
 brain whenever a stimulus is applied. 
 
 10. The functions of the sympathetic system seem 
 to be, to control the action of the alimentary canal> 
 the glands, the blood-vessels and the heart. 
 
 11. Nerves are generally endowed with motor 
 and sensory properties. There are some which 
 have only motor properties, and others which serve 
 the purpose of generating sensations. 
 
144 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON XXXIII. 
 
 THE SENSES IN GENERAL. THE SENSE OF TOUCH. 
 
 The ideas, words and actions of a human being 
 are largely dependent upon the soundness and the 
 training of his sensory organs. 
 
 Sensory organs are tools, or instruments, capable 
 (1) of receiving impressions from the outer world, 
 and (2) of making us conscious of those impressions. 
 The means by which consciousness of impressions 
 arises is sensation. Thus, the eye with its proper 
 nerves is a sensory organ ; it is capable of receiv- 
 ing the impression that a certain ribbon is blue ; 
 there is no other organ which can obtain such an 
 impression. The eye, besides being capable of re- 
 ceiving that impression, is also capable of making 
 us conscious of it, viz., the blue color. A man, 
 after his eyes were removed, would be utterly 
 incapable of recognizing the blue tint, although his 
 mind were never so clear. 
 
 Sensation, in the present example, is excited by 
 the action of the blue rays upon the retina; so we 
 speak of the sensation of cold, meaning by it the 
 peculiar effect which cold has upon the nerves. 
 
 Nearly all sensations come from without the 
 body that is, from the outer world ; they may be 
 
THE SENSE OF TOUCH. 145 
 
 called objective sensations. The yellow color of 
 a lemon, the blue color of a ribbon, are objective 
 sensations. It sometimes happens that the nerves 
 of a sensory organ are affected when there is no 
 objective or outside cause whatever. In this case 
 they make us believe things that have actually 
 no existence. The eye, for example, if closed and 
 pressed upon with a finger, develops a luminous 
 image ; this sensation is drawn not from the exte- 
 rior world, but solely from within the body, hence, 
 is not objective, but subjective. The peculiar noise 
 known as the ' humming of the ear ' is also a sub- 
 jective sensation. 
 
 The sensory organs are five in number, viz., that 
 of sight, hearing, touch, taste and smell. They are 
 merely the peculiarly shaped termination of a par- 
 ticular nerve. Impressions acting upon this termin- 
 ation, or anywhere upon the nerve, whether coming 
 from within the body or from without, affect it in a 
 way that is peculiar to it, and concerning which 
 nothing positive is known. Thus, the eye-ball 
 is so constructed as to collect a great number of 
 rays of light which affect the optic nerve, and 
 thereby produce the sensation of sight. What be- 
 comes of this sensation that is, in what manner it 
 produces the consciousness of sight, and in what 
 manner it ultimately serves intellectual functions, 
 we do not know, and probably never shall. The 
 ear is utterly blind to the minute waves of light, 
 but very sensitive to the aerial waves of sound. So 
 each organ has a distinct structure, in virtue of 
 10 
 
146 FIBST LESSONS IN PHYSIOLOGY. 
 
 which it has its particular manifestations ; and the 
 different senses may be compared to the various 
 departments of government in a country, all of 
 which together make up the government itself. 
 
 THE SENSE OF TOUCH. 
 
 Pressure, resistance, smoothness, roughness, hard- 
 ness, softness, also cold and heat, are the most com- 
 mon sensations excited by the sense of touch. The 
 distinct structure of this sense consists in the nerves 
 which are spread out under the epidermis (Lesson 
 XIII) and within the dermis or cutis. It is a curious 
 fact that the proper sensation is excited only on con- 
 dition that the epidermis (which is known to contain 
 no nerves) lie between the expanded nerves in the 
 dermis and the exciting agent; that is to say, the 
 stimulus or exciting agent must not be in direct 
 contact with the dermis. If by accident, as by burn- 
 ing, the epidermis has been destroyed, the sense of 
 touch of the exposed nerve is reduced to a mere 
 sense of pain. The termination of these nerves is 
 not a flat surface, but consists of a great number of 
 small conical projections, called papillce. Different 
 portions of the body possess different degrees of 
 sensibility ; compare the acuteness of the finger 
 tips with the dullness of the neck. The amount of 
 sensibility is greatly lessened when the skin is 
 stretched. 
 
 A person who takes hold of an exceedingly cold 
 iron bar experiences a sensation nearly like that 
 obtained by touching one overheated. The tooth- 
 
THE SENSE OF TOUCH. 147 
 
 ache caused by the contact of a tooth with ice- 
 cream is the same as that resulting from severe heat 
 applied to the tooth. These well-known facts show 
 that an excess of cold or heat causes pain instead of 
 impression of temperature ; the pain is the same by 
 whichever it may be caused. 
 
 Beyond the dermis the nerves are insensible to 
 heat and cold ; so the optic nerve beyond its expan- 
 sion the retina is no longer sensitive to light. 
 
 The sense of touch is capable of great improve- 
 ment. ' Professor Saunders, of Cambridge, who lost 
 his sight when two years old, could distinguish by 
 this sense genuine medals from imitation ones. 
 Other blind men have, by their exquisite touch, 
 been enabled to become sculptors, conchologists, 
 botanists,' etc., etc. 
 
 Bead 'The Seven Senses.' N. Y. Tribune, Lecture Extra No. 5. 1873. 
 
148 FIRST LESSONS IN PHYSIOLOGY 
 
 LESSON XXXIV. 
 
 THE SENSES OF TASTE AND SMELL. 
 
 TASTE. Sweetness, acidity and pungency are 
 sensations most frequently excited by this sense. 
 Its distinct structure consists of papillce spread over 
 the tongue and portions of the cavity of the mouth. 
 These papillae are the terminations of certain nerves 
 coming from the brain. 
 
 The sense of taste varies greatly in different per- 
 sons ; it depends upon education, habits, and often 
 upon imagination. It is diminished when the mucous 
 surface of the tongue and mouth is affected, as in 
 case of fever. It is a remarkable fact that, when 
 one part of the tongue is injured or paralyzed, the 
 other has its capacity for tasting unimpaired. 
 
 The sensations of taste are largely connected with 
 those of other senses, such as smell, touch, and 
 even sight. Thus, when the nose is held tightly 
 closed so as to obtain no smell, the taste of many 
 a substance is rendered difficult to distinguish ; and 
 it is very nearly the same if the sense of sight is 
 interfered with. 
 
 SMELL. Fragrance and fetor are the principal 
 sensations excited Toy this sense. Its distinct struc- 
 ture consists in olfactory nerves, which are spread 
 
THE SENSE OF SMELL. 149 
 
 over the interior surface of the nasal cavity, and 
 protected by the latter. The olfactory nerves com- 
 mence higher up in the nose ; the lower portion of 
 the nose warms the cold air as it ascends, and thus 
 protects the sensitive surface higher up. It also 
 prevents the latter from becoming dry ; this is of 
 the greatest importance, as the function of the 
 olfactory nerve ceases when the nasal chambers are 
 dry. Substances, in order to produce smell, must 
 have the gaseous form. This does not mean that 
 all gases are odoriferous, for oxygen, nitrogen, 
 hydrogen, and many other gases, when in the pure 
 state, are odorless. The fragrance of a rose, for 
 example, is caused by particles of the flower being 
 diffused in the air and transmitted to the olfactory 
 nerve by means of a current of air inhaled during 
 the act of inspiration. Like taste, smell may be 
 sharpened by education and habit. 
 
 As a rule, we judge localities with strong odors 
 to be unhealthy. The escape of illuminating gas is 
 easily detected by its odor, and may be fatal to the 
 inmates of a room. Many strong odors, however, are 
 harmless, while, on the other hand, quite inodorous 
 atmospheric air may contain the germs of the most 
 dangerous- epidemics. Such is the case with the air 
 of low grounds, marshes and swamps. The con- 
 nection between bad odors and pernicious effects is 
 not yet cleared up ; the production of smell is 
 closely connected with that of chemical action. 
 
150 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON XXXV 
 
 SIGHT. I. 
 
 Light, colors of all kinds, and vision generally, 
 are the principal sensations derived from the or- 
 gan of sight. Its structure comprises the eye-ball 
 and its accesory organs. The eye-ball owes its bulb- 
 like form, solid appearance, and resistance to pres- 
 sure from without arid within, to a hard, fibrous 
 membrane covering it entirely, and having in front 
 a transparent, horny part. 
 
 The eye-ball consists of (1) three distinct coats, 
 and (2) an optical apparatus. 
 
 I. The three coats of the eye (Fig. 33). 
 
 a. The Sclerotic. This membrane is the outer 
 coat of the eye f four-fifths of it is white, opaque, 
 hard, very little elastic ; it forms the rear portions 
 of the membrane, the remaining one-fifth being 
 the front part, a sort of window, called the cor- 
 nea. The sclerotic gives form to the eye, serves 
 for the attachment of muscles, and envelops and 
 protects the parts within. Both sclerotic and cornea 
 are hard, but the cornea is colorless, transparent 
 and elastic. 
 
 b. The Ohoroid. It lines all the interior of the 
 sclerotic with the exception of the optic nerve en- 
 trance. It contains a capillary network of blood- 
 vessels to feed and warm the eye. It is soft and 
 
THE SENSE OF SIGHT. 
 
 151 
 
 elastic, and lined within by a black tissue, or 
 pigment, to absorb unnecessary rays of light. 
 Where this pigment is wanting, as in albinos, a 
 confusion of sight is caused in daylight, probably 
 because the unnecessary rays of light are reflected 
 instead of absorbed. 
 
 The Iris, The bulb of the eye is divided into 
 two unequal parts by a muscular membrane, the 
 
 Cc 
 
 Fig. 3 3 
 
 ** 
 
 The Eye-Ball Horizontal Section. 
 S Sclerotic Coat. C Cornea. 
 
 Ch Choroid Coat. / Iris. 
 
 Cc Ciliary Processes. R Retina. 
 O Optic Nerve (blind spot). 
 * Aqueous Humor (anterior chamber). 
 ** Aqueous Humor (posterior chamber). 
 L Crystalline Lens. 
 Cv Vitreous Humor. 
 Fc Yellow Spot (optic axis). 
 
 iris, forming a sort 
 of curtain, with a 
 central opening, the 
 pupil, to admit the 
 rays of light. The 
 iris is lined on its 
 rear surface by the 
 choroid ; in front it 
 is provided with col- 
 oring matter, which 
 determines the color 
 of the eye. The iris 
 possesses only in- 
 voluntary muscular 
 fibres (ciliary pro- 
 cesses), by the aid 
 of which it con- 
 tracts and thus en- 
 larges the pupil 
 when a greater 
 amount of light is 
 
 needed ; and it dilates thus diminishing the aper- 
 turewhen light is abundant. Thus, the iris regu- 
 
152 FIRST LESSONS IN PHYSIOLOGY. 
 
 lates the supply of light required for distinct vision. 
 c. Retina. Both sclerotic and horoid coats 
 are pierced so as to admit the optic nerve. This 
 nerve comes from the brain and enters the eye-ball 
 from the rear. On reaching the interior surface of 
 the choroid coat the optic nerve divides into minute 
 branches, which are so densely interwoven among 
 each other that they form a nerve membrane, very 
 delicate in structure, and about -^ of an inch in thick- 
 ness. The point where it enters the choroid is not 
 in the main axis of the eye- ball a straight line 
 drawn through the centre of the pupil and bisecting 
 the eye-ball but is situated toward the inner cor- 
 ner of the eye. This point is not sensitive to light, 
 and, therefore, called the ' blind ' spot. It is ascer- 
 tained by the following simple experiment : 
 
 14. EXPERIMENT. Close the left eye; with the 
 right eye look steadily at the cross below, holding 
 the page at a distance of about twelve inches. 
 
 In this position both dot and cross will be seen 
 distinctly. But if the book be slowly brought nearer 
 to the face, the right eye being still fixed upon the 
 cross, the dot will disappear during an instant, and, 
 as the book approaches the face, become visible 
 again. Now, during the instant that the dot van- 
 ished out of sight the image of the dot was on the 
 blind spot of the retina that is, on the region of 
 the retina where the optic nerve enters the choroid. 
 
THE SENSE OF SIGHT. 153 
 
 II. The Optical Apparatus. This is transparent^ 
 and refracts the Jight-rays to the retina. It consists 
 of four lenses : a, the cornea, the network of the 
 lenses ; b, the aqueous humor, the second lens from 
 the front, a watery liquid containing a little salt ; 
 c, the crystalline lens, the third lens, one of the 
 most peculiar bodies in existence. It has the ap- 
 pearance of a double-convex glass and is situated 
 between the iris and the vitreous humor; d, the 
 vitreous humor, the fourth lens. It is filled with a 
 watery fluid, and forms by far the largest part of 
 the eye-ball. 
 
 Thus, the optical apparatus of the eye comprises 
 two solid substances a horny and a glassy one 
 and two liquids, all four serving the purpose of 
 lenses. There is no artificial contrivance which 
 approaches it in excellence. 
 
 The eyebrows serve to guard the eye against ex- 
 cess of light ; the eyelids, to keep the surface of the 
 cornea moist ; the eyelashes, to retain dust floating 
 in the atmosphere. The remarkable mobility of the 
 eye-ball is effected by a number of muscles, which 
 act upon it in various directions. 
 
 Bead 'Our Eyes.' By H. W. Williams. J. Osgood & Co., Boston. 
 Bead ' Diseases of the Eye. ' James Dixon. Lindsay & Blakiston, Phila. 
 
154 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSOIST XXXVI. 
 
 SIGHT. ii. 
 
 The accommodation of the eye. If a small box, 
 blackened on the inside, be provided with a convex 
 lens or a watch-glass, placed in one of its sides 
 which is then the front side of the box we have a 
 camera obscura. The lens collects rays of light 
 from the objects before it ; an image of these objects 
 is produced somewhere in the box. We can catch 
 the image by inserting a piece of ground glass, and 
 it will then be distinctly visible ; or if a sensitive 
 photographic plate be taken in place of the glass, 
 the image will be fixed on the plate. This is the 
 principle of photography. If the image be exam- 
 ined, we shall find that only those spots are pictured 
 on it distinctly which are nearly at the same dis- 
 tance from the lens ; the image of objects farther off 
 is brought to a focus in front of the plate ; that of 
 objects nearer to the lens, behind the plate. 
 
 A little thinking will enable us to see that the 
 eye may be compared to such a camera. The box 
 corresponds to the sclerotic coat, the lens answers 
 to the cornea and crystalline lens, the glass plate, 
 or the back of the box, to the retina. Were we to 
 fill the box with water, this fluid would indicate the 
 fluids of the eye. It will here be observed that in 
 
THE SENSE OF SIGHT. 155 
 
 the camera we have nothing for the iris ; so we must 
 imagine an opaque plate with a hole in the centre, 
 suspended directly behind the watch-glass, whose 
 purpose it should be to regulate the supply of light. 
 But the camera has yet another defect, viz. : it has 
 no means of adjusting the focus so as to view ob- 
 jects at different distances. In order to obtain the im- 
 ages of objects at a greater distance we might move 
 the glass plate toward the lens ; and, on the other 
 hand, to receive the images of objects situated nearer, 
 the plate would have to be pushed farther back. 
 We might also slide the lens forward and back- 
 ward, as is done in the ordinary camera. Or we 
 might effect the adjustment in still another way : 
 take a very convex lens to obtain the image of 
 nearer objects, and exchange it for a less convex 
 one when the image of distant objects is to be 
 thrown on the plate. 
 
 But the simplest way of all would be, if one and 
 the same lens could be made to alter its convexity 
 so as to adjust itself of its own accord to distances. 
 This actually occurs in the eye. 
 
 15. EXPERIMENT. Stick two pins upright into a 
 straight piece of wood, not quite, but nearly, in a 
 straight line with the eye applied to one end of the 
 wood ; one pin to be about six inches from the eye, 
 the other about twelve inches. If we look at the 
 nearer pin first we shall see it very distinctly, while 
 the other pin produces a blurred image. If now we 
 look at the other pin the blurred image will at once 
 become distinct, but we feel that somewhere in the 
 
156 
 
 FIRST LESSONS IN PHYSIOLOGY. 
 
 eye an effort had first to be made. We observe, 
 also, that the nearer pin now yields a blurred image, 
 and on repeated trials it appears evident that we 
 utterly fail to see both pins distinctly at the same 
 instant of time. 
 
 This experiment, as well as a great many familiar 
 facts of the kind, proves that the eye can see an ob- 
 ject distinctly at different distances. Hence, it must 
 be that the eye has the capacity of adjusting itself 
 
 according to the dis- 
 Fig.34 tance of objects. 
 This accommodation 
 on the part of the 
 eye is brought about 
 by a change in the 
 form of the crystal- 
 line lens ; the lens is flattened when a more-distant 
 object is viewed (Fig. 34, A), and becomes more 
 convex (B) when the object to be viewed is nearer. 
 The distance of distinct vision is about ten 
 inches. This means that, generally speaking, no 
 object which is brought within less than ten inches 
 of the eye can be rendered distinctly visible without 
 * effort. There is a certain range within which alone 
 the adjustment of the eye can take place. It is 
 subject to personal variation, i 
 
 Short-sightedness and long-sightedness arise often 
 from a defect in the adjusting powers of the eye. In 
 some persons the cornea is more convex than usual, 
 or the refractive powers of the eye are greatly in 
 creased. Such persons are short-sighted (or near 
 
THE SENSE OF SIGHT. 157 
 
 sighted) : they can see only near objects distinctly, 
 because objects at ordinary distances have their 
 rays come to a focus, not on the retina, but in front 
 of the retina. The images of these objects are 
 thereby rendered indistinct, for the rays, instead of 
 blending into points, form minute circles upon the 
 retina, which causes the blurred appearance of the 
 images. Some people, especially such as are ad- 
 vanced in years, have the cornea flattened that 
 is, not sufficiently convex and for this reason the 
 rays from objects at ordinary distances are not 
 brought to a focus on the retina, but behind it. 
 Either defect is amended by suitable glasses. Short- 
 sighted persons require concave glasses ^ glasses 
 thinnest in the centre which counteract the greater 
 convexity of the eye. Long-sighted people wear 
 convex glasses glasses thickest in the centre 
 so as to render the eye apparently more convex. 
 
 Visible Direction. From the observation of all 
 images formed by rays of light after crossing each 
 other through an aperture, it is evident that the 
 images or external objects are inverted upon the 
 retina. The probable reason why we do not see all 
 objects inverted is our habit of supposing that the 
 point from which a ray strikes us lies in the direc- 
 tion from whence the ray comes. Thus, a point at 
 the top of a steeple, although on the retina pic- 
 tured below, is by the mind supposed to be situated 
 above, because its ray strikes the retina from above. 
 (See First Lessons in Physics, Lesson XXXIV.) 
 
158 FIRST LESSONS IN PHYSIOLOGY. 
 
 Duration of Impressions upon the Retina. 
 When the retina has received an impression of light 
 it retains the impression a little longer than during 
 the actual time in which the light lasts. A lumin- 
 ous impression, however short the time during which 
 the light itself lasts, usually remains on the retina 
 one-eighth of a second. Supposing that two lumin- 
 ous points were to act successively upon the retina 
 in a less interval than one- eighth of a second, then 
 the two impressions would appear as one impres- 
 sion. This explains why a lighted stick, if turned 
 round very rapidly by the hand, appears as a lumin- 
 ous circle ; or why a vibrating string may be visible 
 as a sort of broad film. 
 
 Color -blindness is probably a defect in the retina, 
 or in the humors of the eye, of persons who are un- 
 able to distinguish between certain colors, and 
 sometimes even have no appreciation of any color. 
 They are said to be color-blind. 
 
 The sensitiveness of the retina is readily dimin- 
 ished. If we look steadily at an intensely bright light, 
 the part of the retina on which the rays fall is rapidly 
 weakened, and even temporarily blinded. This may 
 be ascertained by turning from the bright light to- 
 ward a moderately lighted surface; the dark spot 
 which then comes to view is the result of momentary 
 blindness in that part. It is also injurious to strain 
 the eye when the supply of light is insufficient, as 
 when persons attempt to read during twilight. 
 
THE SENSE OP HEAEING. 
 
 159 
 
 LESSON XXXVII, 
 
 HEAKING. 
 
 Sound, noise and music are the principal sensa- 
 tions derived from the sense of hearing. The organ 
 of hearing is the ear. The eye has an optical 
 apparatus to convey waves of light to the terminal 
 branch of the optic nerve, the retina; so the ear 
 has a complex apparatus for the transmission of 
 waves of sound to the terminal branches of the 
 auditory nerve. 
 
 Fig.35. 
 
 OE. 
 
 E.T. 
 
 THE EAR. Transverse Section through the Side Walls of the Skull. 
 OE Outer Ear. M Hammer. 
 
 ET External Tube / Anvil. 
 
 7> Tympanic Membrane. va, ha, -vpa Semicircular Canals. 
 
 D Drum, or Tympanum. Coc Cochlea. 
 
 Eu Eustachian Tube. AN Auditory Nerve. 
 
160 FIRST LESSONS IN PHYSIOLOGY. 
 
 The general" structure of the ear (Fig. 35) consists 
 of (1) the outer ear; (2) the middle ear; (3) the 
 labyrinth, a complicated system of canals, which is 
 filled with a liquid resembling water. 
 
 1. The outer ear (Fig. 35, OE) is a cartilage shaped 
 somewhat like a funnel, and provided with mus- 
 cles. On account of its shape and elasticity it is 
 peculiarly adapted to collect and transmit waves of 
 sound. 
 
 2. The middle ear consists of (1) the external 
 tube, E T, and '(2) the drum, or tympanum, D 
 (scarcely visible in Fig. 35). The former may be con- 
 sidered the tube of the funnel, formed by the outer 
 ear. The outer wall is cartilaginous ; its inner, of 
 bony tissue. Its rear end is closed by the tympanic 
 membrane, Ty, a translucent, delicate membrane 
 which is stretched across the tube in an oblique 
 direction. Were it not for this membrane the exter- 
 nal tube and the drum would form a single passage. 
 The drum is a cavity filled with air, bordered at 
 one end by the tympanic membrane, at the other 
 by two openings one called the oval window (Fv, 
 Fig. 37), the other the round window (Fc, Fig. 37). 
 In the fresh state each of these openings is firmly 
 closed by a membrane ; in the dry skull both are 
 wide open, and lead into the labyrinth. The drum 
 also communicates with the roof of the mouth by 
 means of a long passage called the Eustachian tube, 
 Eu. This canal serves the purpose of equalizing 
 the temperature as well as the pressure of air on 
 
THE SENSE OF HEARING. 
 
 161 
 
 either side of the tympanic membrane, an important 
 item for the healthy state of the ear. 
 
 The drum contains three small bones (Fig. 36) ; the 
 hammer, M, the handle of which (Mm) is fastened 
 to the inner side of the tympanic membrane ; the 
 anvil, I; and the stapes, S. The head of the ham- 
 mer forms a joint with the anvil; the foot-plate of 
 
 the stapes closes the oval 
 Fig. 36 window. These small 
 bones make connection 
 between the tympanic 
 membrane and the 
 labyrinth or, more pro- 
 perly, the oval window 
 (Fv, Fig. 37) which leads 
 to the labyrinth. They 
 convey the vibrations of 
 the tympanic membrane 
 to the labyrinth. 
 3. The Inner Ear, or Labyrinth, consists of 
 (1) the vestibule (not visible in Fig. 37), a chamber 
 which is connected with the drum by means of the 
 oval window. (2) Three hoop-like semi-circular 
 canals, viz., two vertical ones, va, vpa, and one hori- 
 zontal, ha. (3) The cochlea, c, a cavity having the 
 form of a spiral shell, with two and a half windings. 
 Thus, the entire labyrinth consists of chambers 
 and canals which are hollowed out in the solid por- 
 tion of the temporal bone (Lesson II). Each such 
 cavity contains a fluid in which are floating minute 
 branches of the auditory nerve (A N. Fig. 35). 
 
 Mm 
 
 The Small Bones of the Ear. 
 
162 
 
 FIRST LESSONS IN PHYSIOLOGY. 
 
 Fig. 37 
 
 The sensation of sound is excited in about this 
 way : The outer ear collects waves of sound, and 
 conveys them through the external tube to the tym- 
 panic membrane, which is shaken by these waves, 
 and causes the three small bones to vibrate. The 
 last of these bones, the stapes, impinges upon the ves- 
 tibule, to which it imparts its vibrations. These are 
 
 at once taken up by the fluid 
 in the vestibule and trans- 
 mitted to .the remaining 
 liquids in the various canals 
 composing the labyrinth. 
 The motion of the liquids 
 causes the minute fibres and 
 hair-like terminations of the 
 auditory nerve, which are 
 floating freely in the liquids, to vibrate ; and their 
 vibrations are carried by the auditory nerve to the 
 brain. 
 
 Bead 'Deafness.' E. B. Lighthill. Carleton, New York. 
 
 Bead 'Sight and Hearing.' J. H. Clarke. Scribner & Armstrong, N.JY. 
 
 Bead 'Sound and Hearing.' N. Y. Tribune Lecture Extra 5, 1873. 
 
 The Labyrinth (ext. view). 
 
REVIEW. 163 
 
 LESSON XXXVIII. REVIEW. 
 
 LESSON xxxin. 
 
 1. Sensory organs are capable (1) of receiving 
 impressions from the outer world, and (2) of making 
 us conscious of these impressions. 
 
 2. The means by which the consciousness of im- 
 pressions arises within us is called sensation, 
 
 3. The structure of the sense of touch consists in 
 nerves which are spread out under the epidermis. 
 
 LESSON xxxiv. 
 
 4. The structure of the sense of taste consists in 
 papillce spread over the tongue and portions of the 
 cavity of the mouth. Papillae are the terminations 
 of certain nerves coming from the brain. 
 
 5. The structure of the sense of smell consists in 
 olfactory nerves, which are spread over the interior 
 surface of the nasal cavity 
 
 LESSON xxxv. 
 
 6. The structure of the sense of sight consists in 
 two eye-balls, each of which comprises (1) three 
 distinct coats, and (2) an optical apparatus. 
 
 7. The three coats of the eye-ball are : 
 
 (1) The sclerotic coat ; 
 
 (2) The choroid coat ; 
 
 (3) The retina. 
 
 il 7] 
 
 Oar 
 
 
164 FIRST LESSONS IN PHYSIOLOGY. 
 
 8. The retina is the terminal expansion of the 
 optic nerve. Both optic nerves unite into one optic 
 nerve in the brain. 
 
 9. The optical apparatus is made up of 
 
 (1) The cornea ; 
 
 (2) The aqueous humor ; 
 
 (3) The crystalline lens ; 
 
 (4) The vitreous humor. 
 LESSON xxxvi. 
 
 10. The eye is capable of adjusting itself accord- 
 ing to the distances of objects. This power is called 
 the accommodation of the eye. 
 
 11. The distance of distinct vision of the eye is 
 about ten inches. 
 
 12. Short-sightedness and long-sightedness are 
 remedied by concave and convex glasses, respec- 
 tively. 
 
 13. The visible direction of the eye is our habit of 
 supposing the point from which a ray'strikes it to 
 lie in the direction from whence the ray comes. 
 
 14. The retina retains impressions a little longer 
 than during the actual time in which the light lasts. 
 
 15. Color-blindness is a defect of persons in dis- 
 tinguishing between certain colors, or the impossi- 
 bility of detecting any color. 
 
 16. The sensitiveness of the retina is readily ex- 
 hausted. 
 
 LESSON xxxvii. 
 
 17. The structure of the sense of hearing consists 
 of two ears, each of which comprises (1) the outer 
 ear, (2) the middle ear, (3) the inner ear or labyrinth. 
 
REVIEW. 165 
 
 18. The outer ear is peculiarly adapted to collect 
 and transmit waves of sound. 
 
 19. The middle ear consists of (1) the external 
 tube and (2) the drum or tympanum. These are 
 separated from each other by the tympanic mem- 
 brane. The drum contains three small bones : the 
 hammer, the anvil and the stapes. Its inner end 
 contains the oval window and the round window. 
 The three small bones connect the tympanum that 
 is, the tympanic membrane with the oval window. 
 
 20. The labyrinth or inner ear consists of the 
 vestibule, three semi circular canals, and the cochlea. 
 
 21. The labyrinth is filled with liquids, in which 
 are floating the terminal fibres and filaments of the 
 auditorv nerve. 
 
166 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON XXXIX. 
 
 THE MIND. 
 
 We have now seen that man possesses a passive 
 framework composed of bones, which form the 
 levers by which he accomplishes his movements. 
 These levers are acted upon by the muscles, which 
 thereby become the proper organs of motion. These, 
 in turn, are controlled to a greater or less extent by 
 the nervous system. The bones, muscles, sensory 
 organs and nervous system have very properly b&en 
 called the 'Animal Apparatus of Life;' they are 
 found in all the higher animals. 
 
 Now, there is another function apparent in the 
 human body, in virtue of which a constant building- 
 up or repairing of these essentials of animal life 
 is going on within the body, which is called for 
 by the continuous wear and tear of bones, muscles 
 and blood. This function is performed by organs 
 which (1) make blood, such as the alimentary canal 
 and the lymphatics ; (2) keep the blood in circula- 
 tion, as the heart; and (3) maintain it in a pure 
 state, as the lungs. These organs have been com 
 prised under the head of 'Organic Apparatus of 
 Life,' and are also influenced by the nervous sys- 
 tem. 
 
 The animal apparatus of life intimately connects 
 
THE MIND. 167 
 
 man with the highest animals ; the organic appara- 
 tus of life, with the vegetable kingdom. 
 
 Many of the higher species of animals have been 
 greatly changed by domestication. Their ferocious 
 habits have been modified, their instincts improved, 
 their intelligence developed ; but, in spite of all 
 this, domesticated races, when left to themselves, 
 after a few generations return to their original wild- 
 ness. And the superiority of training which an in- 
 dividual animal may have received, never benefits 
 his species or race. 
 
 With the human being it is very different. Man is 
 gifted not only with an unlimited capacity for men- 
 tal accomplishment, but also with a never-ending 
 desire to acquire new mental attainments. And in- 
 dividuals of ability and talent seldom fail to 
 benefit their race. From those gifts springs the 
 eagerness of the human being for education. Educa- 
 tion consists chiefly in repressing the lower habits 
 of human nature, and in developing its nobler 
 qualities. 
 
 Beyond all this there exists yet something more 
 elevated though more difficult to analyze, viz. : the 
 faculty which enables us to conceive the idea of the 
 infinite and our relations to the infinite, by which 
 we possess aspirations after Truth, Goodness, Right 
 and Beauty. 
 
 If the capacity for, and desire after , mental ac- 
 complishment, referred to above, be expressed by 
 
168 FIRST LESSONS IN PHYSIOLOGY. 
 
 the term Mind, we must recognize (a) that the mind 
 is greatly dependent upon the condition and the 
 state of health of the body, and (b) that the body, in 
 turn, is easily affected by the mind. There are many 
 familiar facts to testify to this, among which may 
 be mentioned as proofs of a : (I) The necessity of 
 proper food to nourish the brain : that is, of pure 
 blood with an abundance of oxygen. Wherever 
 this is wanting, mental activity decreases. (2) The 
 effect of local affections of the brain, as when a per- 
 son has received a severe blow on the head. (3) -The 
 effect of intoxication, or (4) of poison, or (5) of fever 
 or other bodily disorder. And among the numerous 
 proofs of b we have : (1) The well-known effects of 
 anxiety, fear, or joy on the body. (2) The inju- 
 rious effect of mental depression on bodily func- 
 tions. (3) The self -restraint exerted by the body in 
 obedience to efforts of the will. 
 
 Attention. Every individual has a certain capa- 
 city of concentrating his faculties upon a task which 
 he wishes to perform. Thus, he may wish to acquire 
 knowledge, to repress his anger, to control his 
 habits, or to observe strict honesty in his dealings 
 with others ; but for any and all of these activities 
 he needs a certain power of will. This power of 
 will he must bring to bear upon his faculties in 
 order to be successful. If all his faculties are di- 
 rected upon any one activity at a time, as, for 
 example, upon the acquisition of mathematics, he 
 nearly excludes them from any other activity, and 
 is then said to be attentive. Attention, therefore, is 
 
PERCEPTION. 169 
 
 the concentration by the power of will of all the fac- 
 ulties upon some one activity to the exclusion of 
 others. Thus, a young person who is bent over his 
 slate, concentrating all his activities upon an arith- 
 metical problem, is almost unaware of what is going 
 on around him. His will deprives the sensory or- 
 gans of nearly all their faculties, which are now 
 spent in inward attention. On the other hand, a 
 countryman visiting a large town for the first time 
 does not follow any particular train of thought, but 
 has his senses busily engaged by the novelties with 
 which he is impressed at every step. His will does 
 not direct his faculties to any special activity ; they 
 are devoted to his sensory organs, and, conse- 
 quently, his attention is wholly outward. 
 
 Perception. A sleeping person may uncon- 
 sciously start at a loud noise, and then resume his 
 former state of sleep. His sensation was correct; 
 he was conscious of it, but he had no distinct per- 
 ception regarding the source or nature of the sound, 
 because he bestowed no attention upon it. Or, if 
 the young student referred to above had been les 
 absorbed by his mathematical problem, he might 
 have unconsciously heard cries outside of his room, 
 and yet not have had a distinct perception of them ; 
 and having finished his task, and hearing the cries 
 again, this time with his full attention directed to- 
 ward them, he may dimly remember to have heard 
 them before. While, then, a sensation is an im- 
 pression upon a conscious state of mind, a percep- 
 tion is an impression upon a conscious state of mind 
 
170 FIBST LESSONS IN PHYSIOLOGY. 
 
 accompanied by attention ; or, perception = sensa- 
 tion + attention. From the preceding it will be 
 clear that a person having heard a loud report at a 
 distance repeated several times, in speaking about 
 it will, with perfect propriety, describe the sensation 
 which the sound produced in himself, and which, as 
 yet, he may attribute to the roaring of cannon or 
 thunder, or to an explosion. Now, let him arrive 
 on the spot from whence the noise proceeded. Sup- 
 pose it to have been due to the practice of artillery. 
 He will then perceive the source and the nature of 
 the report, and thus obtain a distinct perception of 
 the cannon, which he may afterwards describe. He 
 has now learned something outside of himself, and 
 his mind is no longer engrossed with its own sensa- 
 tions. 
 
 Ideas. After his return, the same person can 
 accurately picture the cannon and represent to him- 
 self its effect ; that is, he has retained a mental 
 representation or idea of the object and its effect. 
 This idea he can afterwards reproduce in audible 
 or visible signs words ; or, if he is an artist, he 
 can paint it. An idea is the mental representation 
 of an object; it calls for a higher mental activity 
 than perception. 
 
 A succession of ideas gives rise to thought. The 
 conscious mind is incessantly engaged in thought. 
 "We might continue, and treat of the laws of thought, 
 of emotion, habit, will, sleep and dreams, but the 
 limits of the present volume have now been attained. 
 
DEFINITION OF PHYSIOLOGY. 171 
 
 For further information, the young student should, 
 throughout the course, peruse the works of refer- 
 ence indicated. 
 
 Definition of Physiology. Physiology is the 
 science of the functions of animals and vegetables. 
 Human physiology is the science which treats of 
 the functions of the human body and the manner 
 in which they are brought about. 
 
 Bead Mental Hygiene. D. A. Gorton. Lippincott, Phila. 
 Expression of the Emotions. Darwin. 
 
 Body and Mind. Maudsley. Macmillan & Co., New York. 
 Diseases of Btain. By Forbes Winslow. Churchill & Son, Lond. 
 Disorders of the Mind. By F. Winslow. Churchill & Son, Lon& 
 
 Excellent Anatomical Models, not costly, natural size and magnified, or 
 natural preparations, illustrating Hotze's First Lessons in Physiology, may 
 be found at BERENDSOHN BROS., 
 
 23 John Street, New York. 
 
QUESTIONS. 
 
 A. STRUCTURE. 
 
 LESSON I. ORGANIC AND INOR- 
 GANIC MATTER ANIMAL 
 STRUCTURE. 
 
 PAGE 9. 
 
 1. How are all objects around us 
 
 divided ? 
 
 PAGE 10. 
 
 2. Upon what is this division 
 
 based? 
 
 3. How does inorganic matter dif- 
 
 fer from organic as to form ? 
 
 4. How, in respect to coherence ? 
 
 5. How, as to growth ? 
 
 6. How, as to composition ? 
 
 PAGE 12. 
 
 7. How, as to derivation ? 
 
 8. Give the structure of higher 
 
 animals. 
 
 9. Define "Organisms;" "Func- 
 
 tion." (In Physiology, the 
 term Function means office, 
 work, or action; the last is 
 the preferable.) 
 
 10. State the functions of Organ- 
 
 isms. 
 
 LESSON II. THE SKELETON. 
 
 PAGE 13. 
 
 11. What effect has intense heat on 
 
 bones ? 
 
 12. How does dilute acid affect 
 
 bones ? 
 
 13. Of what substances are bones 
 
 composed ? 
 
 14. Give the structure of bones, 
 PAGE 14 
 
 15 How do bones grow ? 
 
 1 6. How is the skeleton divided? 
 
 What is its number of bones ? 
 
 17. Describe the three cavities of 
 
 the skeleton. 
 
 1 8. What forms the trunk of the 
 
 body? 
 PAGE 1 6. 
 
 19. How are the arms attached? 
 
 and how are the movable 
 joints fastened together? 
 
 20. How are bones renewed ? 
 
 LESSON III. THE HEAD; CERE- 
 BRO-SPINAL Axis; TEETH. 
 
 PAGE 17. 
 
 21. Give princ. parts of the head. 
 PAGE 18. 
 
 22. What two cavities in the head ? 
 
 23. What is ea'ch a part of? 
 PAGE 19. 
 
 24. What separate tubes do they 
 
 help to form ? 
 
 25. Describe the parts of a tooth ? 
 PAGE 21. 
 
 26. Give number and arrangement 
 
 of temporary teeth in either 
 jaw. 
 
 27. Give the same of permanent 
 
 teeth in either jaw. 
 
 28. What sudden changes are in- 
 
 jurious to the teeth ; and why ? 
 
 29. Mention two great functions of 
 
 bones. 
 
 (ist. Locomotion. 
 
 2d. Protection of softer parts, 
 as e. g., the skull protect- 
 ing the brain. ) 
 30 How do teeth differ from bones? 
 
174 
 
 FIRST LESSONS IN PHYSIOLOGY. 
 
 LESSON V. THE TRUNK. 
 
 PAGE 24.- 
 
 31. Describe the spinal column. 
 
 32. What are vertebrae ? 
 
 33. How are the lungs protected 
 
 from above, and by what are 
 they encircled ? 
 PAGE 25. 
 
 34. Describe a vertebra. 
 PAGE 26. 
 
 35. Give three functions of the 
 
 spinal column. 
 
 36. How many ribs are fastened to 
 
 the sternum ; and why do the 
 other ribs not reach it ? 
 
 37. What lies between each pair of 
 
 vertebrae ? 
 
 38. What two offices have these 
 
 cartilages ? 
 
 39. How is the variation in the 
 
 length of the human body ex- 
 plained ? 
 
 40. How is the pelvis formed ? 
 
 LESSON VI. THE LIMBS. 
 
 PAGE 27. 
 
 41. What similarity in the bones of 
 
 the upper and lower limbs ? 
 
 42. Describe the hand. 
 PAGE 28. 
 
 43. Describe the foot. 
 
 44. What supports the body when 
 
 erect ? 
 
 45. State the purpose of the ball- 
 
 and-socket joint. 
 
 46. Where is this joint found? 
 
 47. What is the hinge-joint ? 
 
 48. How many bones in the foot ? 
 
 49. Give the object of the arch of 
 
 the foot ? 
 
 50. State the chief advantages of 
 
 the human hand. 
 
 LESSON VII. CARTILAGES 
 THE LARYNX. 
 
 PAGE 30. 
 
 51. Give three samples of cartilage? 
 
 52. How does cartilage differ from 
 
 bone ? 
 
 53. Give four uses of cartilage ? 
 
 PAGE 31. 
 
 54. What, and where, is the glottis? 
 
 55. What is the epiglottis ? 
 
 56. Bound the larynx. 
 
 Describe the trachea. 
 
 58. Describe the bronchi and bron- 
 
 chial tubes. 
 
 59. Describe contents of the larynx. 
 
 60. How is sound produced in the 
 
 larynx ? 
 
 LESSON IX. MUSCLES; FAT. 
 
 PAGE 35. 
 
 61. What happens when the fore- 
 
 arm is bent up ? 
 
 62. Describe a muscle. 
 
 63. Why are muscles generally 
 
 called the organs of motion ? 
 PAGE 36. 
 
 64. What is the first property of 
 
 muscles ? 
 
 65. What the second ? 
 
 66. Explain rigor mortis. 
 
 67. How are voluntary muscles dis- 
 
 tinguished from involuntary? 
 
 68. Give two instances of each 
 
 class. 
 
 69. Which class is uncontrolled by 
 
 the will ? 
 PAGE 37. 
 
 70. What are the chief uses of fat ? 
 
 LESSON X. MUSCLES MOTOR 
 AGENTS WALKING. 
 
 PAGE 38. 
 
 71. Show why the arm is consider- 
 
 ed a lever. 
 
 72. To what does the arm owe its 
 
 variety of motions ? 
 
 73. By what are those motions ex- 
 
 erted ? 
 
 PAGE 39. 
 
 74. Explain why 100 pounds of 
 
 effort is required to balance 5 
 pounds at the free end of the 
 arm stretched out horizontally. 
 PAGE 40. 
 
 75. In what three forms do we re- 
 
 gain much of the muscular 
 force which is apparently lost? 
 
QUESTIONS. 
 
 175 
 
 76. How do muscles generally ter- 
 
 minate ? 
 
 77. Decide the first step in the act 
 
 of walking. 
 
 78. Describe the second step. 
 
 79. Describe the third step. 
 
 80. Describe the fourth step. 
 
 LESSON XI. MUSCLES (CON- 
 TINUED) WORK OF MUSCLES 
 LEAPING. 
 
 PAGE 42. 
 
 81. Explain the fatigue in standing 
 
 erect long. 
 
 82. What are the functions ot con- 
 
 nective tissue ? 
 
 PAGE 44. 
 
 83. Why are the muscles of the 
 
 head and trunk less substan- 
 tial? 
 
 84. Where is the helmet ? 
 
 85. Give the number of external 
 
 muscles. 
 
 86. What two motions constitute a 
 
 leap ? 
 
 PAGE 46. 
 
 87. Plow is it that a person in leap- 
 
 ing exerts a musculai force of 
 twice his weight into the ver- 
 tical height ? 
 PAGE 47. 
 
 88. In what way is the mechanical 
 
 power of the body used to 
 best advantage ? 
 
 89. How far may we exhaust our 
 
 forces ? 
 
 90. What limits should be observed? 
 
 LESSON XIIL SKIN HAIR AND 
 NAILS EXCRETION OF SKIN. 
 
 PAGE 51. 
 
 91. How is glue produced from 
 
 skin? 
 
 92. Describe the parts of the skin. 
 
 93. Describe the epidermis. 
 
 94. What are its main functions ? 
 
 95. What are the main functions of 
 
 the dermis ? 
 PAGE 52. 
 
 96. Describe the dermis. 
 
 97. State the general properties of 
 
 the skin, and give their uses. 
 
 98. Describe the hair and nails. 
 
 99. Describe the two excretions of 
 
 the skin. 
 
 PAGE 53. 
 
 100. What does the quantity of water 
 
 lost by transpiration depend 
 upon ? 
 
 B. NUTRITION. 
 
 """LESSON XIV. THE BLOOD. 
 
 PAGE 54. 
 
 101. Describe the clot. 
 
 1 02. What is the name and the color 
 
 of the liquid ? 
 
 103. What is the composition of 
 
 blood? 
 
 PAGE 55. 
 
 104. Give the temperature and spe- 
 
 cific gravity of the blood. 
 
 105. What is the quantity of blood 
 
 in the body ? 
 
 1 06. What does the health of the 
 
 blood depend upon ? 
 
 107. Describe the red corpuscles. 
 PAGE 56. 
 
 108. Describe the white corpuscles. 
 
 109. What gases does the blood con- 
 
 tain? 
 
 PAGE 57. . 
 
 no. Give the uses of the blood. __ rr ^ 
 
 LESSON XV. THE CIRCULA- 
 TION, i. 
 
 PAGE 58. 
 
 in. How large is the heart ? 
 
 112. How is it that the blood leaves 
 
 the heart and returns to the 
 heart again? 
 PAGE 59. 
 
 113. Describe the divisions of the 
 
 heart. 
 
 114. Describe the communication 
 
 between auricle and ventricle? 
 PAGE 60. 
 
 115. Give the course of the blood 
 
 from the heart, and back again 
 to its starting place. 
 
176 
 
 FIRST LESSONS IN PHYSIOLOGY. 
 
 1 1 6. Which artery carries venous 
 
 blood ? With what part of the 
 heart is it connected? 
 
 117. Where is the blood rendered 
 
 impure, and to which division 
 of the heart does the impure 
 blood flow ? 
 PAGE 6l. 
 
 118. Mention several helpers which 
 
 assist the action of the heart. 
 
 1 19. State the functions of each sub- 
 
 division of the heart. 
 
 1 20. Compare these functions with 
 
 one another. 
 
 LESSON XVI. THE CIRCULA- 
 TION, ii. 
 
 PAGE 62. 
 
 121. How may the movements of the 
 
 heart be examined ? 
 
 122. What movements form a pulsa- 
 
 tion? 
 
 123. Define systole and diastole. 
 
 What is their ratio of time ? 
 PAGE 63. 
 
 124. What is it that prevents the 
 
 blood, as it leaves the heart, 
 from returning at once into 
 the veins? 
 
 125. Describe the auricular systole. 
 
 126. Explain the ventricular systole. 
 PAGE 64. 
 
 127. What is the course of the blood 
 
 on leaving the ventricles? 
 PAGE 65. 
 
 128. What two effects has the pres- 
 
 sure of the three ounces of 
 blood passing into the arteries 
 after ea^h ventricular systole ? 
 PAGE 66. 
 
 129. What is the pulse ? Where may 
 
 it be felt ? Why are the capil- 
 laries pulseless ? 
 PAGE 67, 68. 
 
 130. Give the use of the arteries ? 
 
 And state two reasons why 
 compression of veins does not 
 check the circulation. 
 
 LESSON XVIIL THE LUNGS. 
 
 PAGE 74- 
 
 131. Define arterial and venous 
 
 blood. How do they differ 
 from each other ? 
 
 132. How, and where, is venous 
 
 blood converted into arterial ? 
 PAGE 75. 
 
 133. Locate and describe the lungs. 
 
 1 34. Give the structure of the trachea, 
 
 bronchial tubes and the finer 
 tubes. 
 
 135. How many lobes in each lung? 
 
 What is a lobule ? 
 
 136. What becomes of the finer 
 
 bronchial tubes? 
 
 137. Describe the air-cells and their 
 
 contents. 
 PAGE 77. 
 
 138. What is the purpose of the capil- 
 
 laries of the lungs, and how 
 is' it accomplished? 
 
 139. What does venous blood gain 
 
 and lose in the lungs? By 
 what means is its purification 
 effected ? 
 
 PAGE 7g. 
 
 140. What is accomplished by inspir- 
 
 ation and expiration ? What 
 are the most powerful aids in 
 this process. 
 
 LESSON XIX. RESPIRATION. 
 
 PAGE 79- 
 
 141. Describe the process of inspira- 
 
 tion. 
 
 142. Describe expiration. 
 
 143. Explain the widening and 
 
 lengthening of the chest dur- 
 ing ordinary inspiration. What 
 are the helps in very deep in- 
 spiration ? 
 PAGE 81. 
 
 144. What rhythm is observable in 
 
 inspiration, and to what is it 
 similar ? 
 
 145. Give the points in which inspir- 
 
 ed air differs from expired. 
 
 146. Explain the absorption of oxy- 
 
 gen by venous blood. 
 
QUESTIONS. 
 
 177 
 
 147. "What does the oxygen combine 
 
 with, and what becomes of 
 this combination finally ? 
 PAGE 8 1. 
 
 148. Why is fresh air necessary, and 
 
 why ventilation ? How does 
 a lack of either shorten life ? 
 
 PAGE 82. 
 
 149. Explain coughing, sneezing 
 
 and sighing; also, laughing, 
 sobbing and snoring. 
 
 150. Compare the lungs with the 
 
 heart, giving three points in 
 common and three points of 
 difference. 
 
 LESSON XXI. AIR AND ITS 
 RELATION TO THE BODY. i. 
 
 PAGE 87. 
 
 151. Explain the requirement of the 
 
 body in regard to vital heat. 
 
 152. What penalty attaches to the 
 
 decrease of the normal tem- 
 perature? What to the in- 
 crease of the normal tempe- 
 rature ? 
 PAGE 88. 
 
 3. In what ways do we experience 
 lo of heat ? 
 
 154. Define conduction of heat. 
 PAGE 89. 
 
 155. Show that water conducts heat 
 
 better than air. 
 
 PAGE 90. 
 
 156. Define radiation of heat. State 
 
 how a person may expose him- 
 self to partial radiation, and 
 what the effects may be. 
 
 157. Explain the feeling of cold in 
 
 windy weather. 
 
 158. In what way are bodies affected 
 
 by conduction and radiation 
 of heat ? 
 PAGE 91. 
 
 159. What explains the loss of heat 
 
 by evaporation ? 
 
 160. To what are the injurious effects 
 
 of wet feet ascribed? How 
 should we guard against cold? 
 
 12 
 
 LESSON XXII. AIR AND ITS 
 RELATION TO THE BODY. n. 
 
 PAGE 92. 
 
 161. Describe the functions of our 
 
 garments. 
 
 162. Why is flannel a healthier ma- 
 
 terial than india-rubber? 
 PAGE 93. 
 
 163. What is the first object of cloth- 
 
 ing? What the second? 
 
 1 64. Give the characteristics of linen. 
 
 Why is it to be avoided next 
 to the skin ? 
 
 PAGE 94. 
 
 165. How does cotton differ from 
 
 linen ? 
 
 1 66. Give the characteristics of wool- 
 
 lens. What makes woollen 
 goods valuable as clothing 
 material ? 
 PAGE 95. 
 
 167. Explain why the bed should be 
 
 warmer than the clothing. 
 PAGE 96. 
 
 1 68. State why moist walls are un- 
 
 healthy. How is their moisture 
 removed best ? 
 
 169. What does the purity of air 
 
 depend on ? What causes the 
 impurity of air ? 
 PAGE 97. 
 
 170. Distinguish between ventilation 
 
 and draught. What does ven- 
 tilation depend on ? 
 
 LESSON XXIV. FOOD. 
 
 PAGE IOI. 
 
 1 71. What are the principal elements 
 
 composing the human body? 
 
 PAGE 102. 
 
 1 72. What are the sources of loss to 
 
 the body ? 
 
 173. Illustrate this by a man in a 
 
 glass house. 
 PAGE 103. 
 
 174. Define food. 
 
 175. How are the materials which 
 
 constitute food divided ? 
 
 1 76. What mixture of these divisions 
 
 is essential to our well-being ? 
 
178 
 
 FIRST LESSONS IN PHYSIOLOGY. 
 
 PAGE 104, 
 
 177. Mention two substances that 
 
 are nutritious but not digest- 
 ible. 
 
 178. Why are many tasteless sub- 
 
 stances not nutritious ? How 
 may they be rendered nutri- 
 tious. 
 
 179. State the purpose of cooking 
 
 our food. 
 
 1 80. What sensations remind us of 
 
 the necessity of taking food ? 
 What is meant by oxygen- 
 starvation ? 
 
 SOLID AND LIQUID FOOD 
 
 (181. Fine Print State the advan- 
 tages of beef. 
 
 182. How does veal compare with 
 
 beef? 
 
 1 83. How does mutton compare with 
 
 beef? 
 
 184. What are the advantages and 
 
 disadvantages of pork ? 
 
 185. What part should fish play in 
 
 meals ? 
 
 186. Give the object of eating butter. 
 PAGE 105. 
 
 187. State the excellencies of wheat. 
 
 188. How does the potato compare 
 
 with bread? 
 
 189. Which is, after all, the most 
 
 important of all foods, and 
 why ? What constitutes im- 
 pure water? 
 
 190. What is remarkable about milk? 
 
 Why are coffee and tea highly 
 valued ?) 
 
 LESSON XXV. DIGESTION, i. 
 
 PAGE 1 06. 
 
 191. Whence do plants derive their 
 
 food? 
 
 192. What do animals generally feed 
 
 on? What great distinction 
 between animals and plants 
 respecting their food? 
 
 193. Describe the changes wrought 
 
 upon the food in the body. 
 
 PAGE IO7. 
 
 194. Through what channel does 
 
 food pass into the blood ? 
 
 195. What is the daily quantity of 
 
 solid food of a man ? 
 
 196. What two important additions 
 
 should be made to this ? 
 
 197. When does digestion commence? 
 
 198. In what consists the first part 
 
 of digestion ? 
 
 199. What purpose do the teeth in 
 
 fishes subserve ? 
 
 PAGE 1 08. 
 
 200. Describe the characteristic teeth 
 
 of the herbivores. 
 
 201. Describe teeth of carnivores. 
 
 202. What significant arrangement 
 
 in the human teeth ? 
 
 203. What is the function of the 
 
 tongue in digestion ? 
 
 204. What organs combine to break 
 
 down the food ? 
 
 205. Why is it broken down ? 
 
 206. Why is rapid eating injurious? 
 PAGE 109. 
 
 207. Describe the second part of the 
 
 digestive process. 
 
 208. State the function of the saliva ? 
 
 209. When does deglutition take 
 
 place, and how is it effected ? 
 
 210. Why may a starving sheep be 
 
 rightly said to be carnivorous . 
 (See pages 102 and 119.) 
 
 LESSON XXVI. DIGESTION, n. 
 
 PAGE 1 10. 
 
 211. Describe the stomach. What 
 
 name is given to its two open- 
 ings, and where are they sit- 
 uated ? 
 
 PAGE III. 
 
 212. In what way is the food in the 
 
 stomach reduced to chyme, 
 and what fluid assists in this 
 operation ? 
 
 213. Which kind of muscles perform 
 
 mechanical labor in the stom - 
 ach? 
 
 214. Why cannot the stomach crush 
 
 an entire grape? 
 
QUESTIONS. 
 
 179 
 
 215. State the chief functions of the 
 
 stomach. 
 
 2 1 6. What action is temporarily 
 suspended in the stomach ? 
 
 217. Give the conditions favorable 
 
 to stomach-digestion. 
 
 218. Why may ice-water taken dur- 
 
 ing a meal prove injurious ? 
 
 219. Give the desirable length of the 
 
 interval between two consecu- 
 tive meals. 
 
 .1 20. State the process undergone by 
 the food between the mouth 
 and the pylorus. 
 
 LESSON XXVIL-DiGESTiON. m. 
 
 PAGE 113. 
 
 221. Describe the intestines. 
 
 222. How are they divided? 
 
 223. State the length of the small 
 
 intestine, and of the entire 
 alim. canal. 
 
 224. Where does the peristaltic mo- 
 
 tion take place, and what does 
 it consist in ? 
 
 PAGE 115. 
 
 225. How is the large intestine 
 
 divided ? 
 
 226. Describe the position of each 
 
 part. 
 
 227. How is the large intestine 
 
 readily recognized ? 
 
 228. How does the motion of the 
 
 large intestine differ from that 
 of the small ? 
 
 229. Mention all the digestive fluids. 
 PAGE 1 1 6. 
 
 230. What is the purpose of the mu- 
 
 cous substance secreted by 
 the stomach ? 
 
 231. Describe the other liquid se- 
 
 creted by the stomach. 
 
 232. What action has this liquid upon 
 
 fatty substances ? 
 
 233. Explain the pernicious effect 
 
 upon the stomach of immode- 
 rate quantities of alcohol. 
 
 234. What two actions convert the 
 
 food into chyme ? 
 
 235. What becomes of the chyme 
 
 after leaving the stomach? 
 
 236. Where does the food undergo 
 
 its most important change ? 
 
 237. Describe the liver. 
 
 238. What are the functions of the 
 
 liver ? 
 
 239. Where does the bile accumulate, 
 
 and whither does it flow ? 
 PAGE 117. 
 
 240. Why must the bile be con- 
 
 ducted out of the system ? 
 
 241. What does bile produce when 
 
 in the blood ? 
 
 242. What does bile produce when 
 
 thrown into the stomach ? 
 
 243. What name has the chyme after 
 
 its union with bile ? 
 
 244. Give the remaining two actions 
 
 of the bile. 
 
 245. State the composition of the 
 
 chyme when leaving the stom- 
 
 PAGE 1 1 8. 
 
 246. What distinguishes the pan- 
 
 creatic juice? 
 
 247. Describe the pancreas, and the 
 
 peculiarity it has in common 
 with the salivary glands of the 
 mouth. 
 
 248. What is the office of the intes- 
 
 tinal juice? Where is it se- 
 creted ? 
 
 249. What is the estimated quantity 
 
 of the five digestive liquids a 
 day? What of the gastric 
 juice alone? 
 
 250. Describe the combined action 
 
 of thos five liquids. 
 
 LESSON XXVIII-AssiMiLATiON. 
 
 PAGE 119. 
 
 251. Explain the interdependency of 
 
 life and death in the organism. 
 
 PAGE 120.- 
 
 252. How is digested aliment con- 
 
 verted into blood so as to be 
 distributed over the entire 
 body ? 
 
 253. Describe the twofold object of 
 
 absorption. 
 
180 
 
 FIRST LESSONS IN PHYSIOLOGY. 
 
 PAGE 122. 
 
 254. Describe blood-vessels or capil-, 
 
 laries (Fig. 26). Describe 
 the lacteals (Fig. 27). 
 
 255. Describe the absorption of the 
 
 chyle by blood-vessels. 
 
 256. Describe the absorption by the 
 
 lacteals. 
 
 257. Explain the absorption of chyle 
 
 by a villus. 
 
 PAGE 123. 
 
 258. Describe the lymphatic glands. 
 PAGE 124. 
 
 259. Describe the position aud action 
 
 of the thoracic duct. 
 
 260. Trace the further progress of 
 
 the chyle. 
 
 C. INNERVATION. 
 
 LESSON XXX. THE NERVOUS 
 SYSTEM, i. 
 
 PAGE 130. 
 
 261. Give the first two functions of 
 
 the nervous system, demon- 
 strating each. 
 
 PAGE 131. 
 
 262. Give the third, fourth and fifth 
 
 functions, demonstrating each; 
 
 263. Give sixth and seventh func- 
 
 tions, and demonstrate each. 
 
 PAGE 132. 
 
 264. How is the nervous system div- 
 
 ided and subdivided ? 
 PAGE 133. 
 
 265. Describe the brain. 
 PAGE 134. 
 
 266. Describe the cerebrum and 
 
 cerebellum. 
 
 267. Describe the spinal cord. 
 
 268. Where do the cerebro-spinal 
 
 nerves originate? What is 
 their form ? 
 
 269. Describe nervous fibres. Where 
 
 do they originate ? 
 
 270. What do nervous fibres form at 
 
 their termination? 
 
 271. What is the size of those nerv- 
 
 ous fibres, and where are they 
 smallest ? 
 
 PAGE 135. 
 
 272. What does the sympathetic sys- 
 
 tem consist of? 
 
 273. Where is it situated, and how 
 
 is it connected ? 
 
 274. What course is pursued by its 
 
 nerves ? 
 PAGE 136. 
 
 275. Mention the two substances 
 
 composing the nervous sys- 
 tem. 
 
 276. Where is the white substance 
 
 within the gray, and where 
 the gray within the white? 
 
 277. Of which substance are the nerv- 
 
 ous fibres and tubes ? Of 
 which the cells ? 
 
 278. Which substance forms the cen- 
 
 tral organ of the nervous sys- 
 tem ? 
 
 279. What function has the gray 
 
 substance ? What function the 
 white ? 
 
 280. To what may both materials be 
 
 compared ? 
 
 LESSON XXXI. THE NERVOUS 
 SYSTEM, u. 
 
 PAGE 137. 
 
 281. Explain the reason for the con- 
 
 volutions in the brain. 
 PAGE 138. 
 
 282. What seems to be the function 
 
 of the cerebral hemispheres ? 
 and what are the reasons for 
 believing this ? 
 PAGE 139. 
 
 283. State the function of the medul- 
 
 la oblongata. 
 
 284. In what respect is the medulla 
 
 obi. specially distinct from the 
 brain and the spinal cord? 
 
 285. Give the functions of the spinal 
 
 cord. 
 PAGE 140. 
 
 286. Describe the functions of the 
 
 sympathetic system. 
 
 287. Explain the two special func- 
 
 tions of the nerves. 
 
QUESTIONS. 
 
 181 
 
 288. Demonstrate the existence of 
 
 motor nerves. 
 
 PAGE 141. 
 
 289. Demonstrate the existence of 
 
 sensory nerves. 
 
 290. What are the nerves of the 
 
 spinal cord endowed with ? 
 
 LESSON XXXIII. THE SENSES. 
 
 PAGE 144. 
 
 291. Define sensory organs. 
 
 292. What is sensation? Show by 
 
 an example. 
 PAGE 145. 
 
 293. Distinguish between objective 
 
 and subjective sensations. 
 
 294. Explain in what manner the 
 
 sense of sight is produced. 
 
 295. How are sensations generally 
 
 produced, and what becomes 
 of them ? 
 
 TOUCH. 
 
 PAGE 146. 
 
 296. Give the common sensations 
 
 excited by the sense of touch. 
 
 297. In what does its distinct struc- 
 
 ture exist ? 
 
 298. Show by facts that an excess of 
 
 heat or cold produces like 
 impressions. 
 PAGE 147. 
 
 299. How far do the nerves retain 
 
 their sensibility to touch ? 
 
 300. State why this sense seems cap- 
 
 able of great improvement. 
 
 LESSON XXXIV. TASTE. 
 
 PAGE 148. 
 
 301. Give the most frequent sensa- 
 
 tions excited by the sense of 
 taste. 
 
 302. In what does the distinct struc- 
 
 ture of this sense consist ? 
 
 303. What tends greatly to modify 
 
 the sense of taste ? And what 
 is remarkable about the ton- 
 gue? 
 
 304. How can it be proved that this 
 
 sense is largely connected with 
 other senses ? 
 
 SMELU 
 
 PAGE 149. 
 
 305. Give the principal sensations 
 
 produced by the sense of 
 smell. 
 
 306. Describe its structure. 
 
 307. How are the nasal chambers 
 
 protected from dryness ? 
 
 308. What form must all matter have 
 
 in order to impress itself, 
 upon the olfactory nerves ? 
 
 309. How does a dog obtain the 
 
 scent of an object? 
 
 310. State what connection there is, 
 
 if any, between bad odors and 
 their supposed effects ? 
 
 LESSON XXXV. SIGHT, i. 
 
 PAGE 150. 
 
 311. State the principal sensations 
 
 excited by the sense of sight. 
 
 312. Describe the structure of this 
 
 sense. 
 
 .313. What does the eye-ball owe to 
 the membrane which covers 
 it, and of what does the eye- 
 ball consist ? 
 
 314. Describe the choroid. 
 
 PAGE 151. 
 
 315. Describe the iris, 
 
 PAGE 152. 
 
 316. Desc-ibe the retina. 
 
 317. How may the blind spot in the 
 
 eye be readily detected ? 
 
 318. What do we experience when 
 
 the retina is in a state of utter 
 rest? 
 PAGE 153- 
 
 319. Describe the optical apparatus 
 
 of the eye. 
 
 320. What functions have the eye- 
 
 brows and eye-lids ? And how 
 is the mobility of the eye-ball 
 effected? 
 
 LESSON XXXVI. SIGHT, "n. 
 
 PAGE 154. 
 
 321. Describe a camera obscura, and 
 
 the principle of photography. 
 
182 
 
 FIRST LESSONS IN PHYSIOLOGY. 
 
 322. Show that the eye may be com- 
 
 pared to a camera obscura. 
 PAGE 155. 
 
 323. What is the experiment that 
 
 proves that the eye can adjust 
 itself to different distances ? 
 
 PAGE 156. 
 
 324. Describe the distance of distinct 
 
 vision. 
 
 325. Explain short-sightedness and 
 
 long-sightedness, and tell how 
 each may be neutralized. 
 PAGE 157. 
 
 326. Explain visible direction. 
 PAGE 158. 
 
 327. What is known regarding the 
 
 duration of impressions on the 
 retina? 
 
 328. What is color-blindness ? 
 
 329. How may the sensitiveness of 
 
 the retina be ascertained ? 
 
 330. Mention two frequent sources 
 
 of injury to the eye. 
 
 LESSON XXXVII. HEARING. 
 
 PAGE 159. 
 
 331. What are the principal sensa- 
 
 tions derived from the sense 
 of hearing? 
 PAGE 1 60. 
 
 332. Give the general structure of 
 
 this sense. 
 
 333. Describe the outer ear. 
 
 334. Describe the external tube and 
 
 the drum of the middle ear. 
 
 335. Describe the contents of the 
 
 drum. 
 
 336. What seems to be the function 
 
 of the eustachian tube ? 
 PAGE 161. 
 
 337. Describe the labyrinth. 
 
 PAGE 162. 
 
 338. State how the sensation of 
 
 sound is produced 
 
 339. Compare the ear with the eye, 
 
 giving three points in common, 
 (i. Outer ear and ext. tube 
 op*, apparatus. 
 
 2. Tympanum retina. , 
 
 3. Auditory nerve optic 
 nerve. ) 
 
 340. Find three points of difference. 
 LESSON XXXIX. THE MIND. 
 
 PAGE 1 66. 
 
 341. Describe the two apparatus of 
 
 life. 
 PAGE 167. 
 
 State the difference between the 
 higher animals and man, as 
 regards domestication, educa- 
 tion and the consciousness of 
 the infinite. 
 
 343. What specially characterizes the 
 
 human species, at least the 
 higher types of man ? 
 PAGE 1 68. 
 
 344. Give proofs of the dependence 
 
 of the mind on the body. 
 
 345. Give proofs of the dependence 
 
 of the body on the mind. 
 
 346. When is a person said to be 
 
 attentive ? 
 PAGE 169. 
 
 347. Demonstrate, by examples, that 
 
 there is an inward and an out- 
 ward attention. 
 
 348. Define sensation and percep- 
 
 tion. 
 PAGE 170. 
 
 349. Define idea. 
 PAGE 171. 
 
 350. Define physiology. 
 
GLOSSARY: 
 
 CONTAINING THE ANATOMICAL AND PHYSIOLOGICAL MEANING 
 OF CERTAIN TERMS. 
 
 Ab-do'men. The largest cavity of the body ; below the dia- 
 phragm and above the pelvis, containing the stomach, in- 
 testines, liver, spleen, etc. 
 
 ASid. A substance generally sour to the taste, which changes 
 vegetable blue colors to red, and combines with bases to 
 form salts. 
 
 Adipose*. Fat, or fatty. 
 
 Al-bu'men. A substance like the white of an egg, coagulating 
 by heat. 
 
 AVi-ment. Nourishment; food. 
 
 Al-i-menfa-ry Ca-naL A tube passing through the body, be- 
 ginning with the mouth, piercing the diaphragm, and ter- 
 minating with the rectum, by which nourishment is taken 
 into the body, digested, and indigestibles excreted. 
 
 Aor'ta. The great artery arising from the upper and the back 
 part of the left ventricle of the heart ; the common trunk 
 of the arteries of the body. 
 
 Apparatus (Physiol.) A system of organs concerned in some 
 special function of the animal body. * 
 
 Artery. Any branch of the aorta conveying blood in the 
 direction from the heart to all parts of the body. 
 
- 
 
 184 FIRST LESSONS IN PHYSIOLOGJ. 
 
 As-sim-i-la' tion. The conversion of food into the substance of 
 organized beings. 
 
 Au'ricle. The external ear. Hence one of the two venous 
 chambers of the heart, resembling the external ear. 
 
 Bi'ceps. Two-headed. A muscle attached, on the one hand, 
 to the shoulder-bone, and, on the other, to one of the 
 bones of the fore-arm. 
 
 Bicuspid. A molar tooth having two points. 
 
 Branch' us. The windpipe, or trachea. The bronchi, or bron- 
 chia, now mean the two tubes which arise from the bifur- 
 cation of the trachea, and carry air into the lungs. 
 
 Cam'era-obscu'ra. An instrument used in a darkened room 
 to throw images of external objects upon a surface. 
 
 Ca-nine'. Applied to teeth, it means the pointed, often long, 
 tooth next to the incisor. 
 
 Cap'-il-la-rics. A network of minute blood-vessels, connect- 
 ing the termination of the arteries with the termination 
 of the veins. 
 
 Car'di-ac. From the Greek kardia, the heart. 
 
 Carniv'orous. Flesh-eating. Carnivore, a carnivorous animal. 
 
 Car'ti-lage, or gristle. A dense, firm substance of less hard 
 tissue than bones. 
 
 Cell. A small, distinct, spheroidal mass of protoplasm or 
 living material. 
 
 Ccr-e-bel' lum. The little brain, beneath the cerebrum. 
 
 Ccr'e-brum. The brain proper, occupying the entire upper 
 portion of the skull. 
 
 Cho'roid. A coat containing a great many blood-vessels, lin- 
 ing the interior surface of the sclerotic coat of the eye. 
 
 Chyle. A milky fluid formed in the process of digestion 
 by the action of the pancreatic juice and the bile on 
 the chyme in the duodenum. 
 
GLOSSAET. 185 
 
 Chyme. A pulp formed by the action of the stomach on 
 the food. 
 
 Cil'i-ary Processes. The minute radiating ridges formed 
 around the iris by the anterior portion of the choroid. 
 
 Clav'i-cle. The collar bone. 
 
 Coch'lea. A cavity of the ear resembling a spiral shell. 
 
 Coherence. The act or state of cohering. 
 
 Co'lon. That portion of the large intestine extending from 
 the caecum to the rectum. 
 
 Connective tissue. The connecting medium by which the dif- 
 ferent parts of the body are held together. It passes 
 from the dermis between all the other organs, ensheathing 
 the muscles, coating the bones and cartilages, and ulti- 
 mately entering into the mucous membranes. 
 
 Contrac'tile. Having the power of contraction. 
 
 Corpus 'cle. Minute body or particle of matter. 
 
 Cu'ti-cle. The superficial layer of the skin. The same as 
 epidermis. 
 
 Cutis. The deeper portion of the skin. The same as dermis. 
 
 Degluti'tion. The act, or power, of swallowing food. 
 
 Dentine. The principal constituent of a tooth. 
 
 Derivation. Transmission of anything from its source. 
 
 Dermis. The same as cutis. (See this.) 
 
 Diaphragm. The muscular partition separating the chest from 
 the abdomen, and assisting respiration. 
 
 Dias'tole. A dilatation of the heart and arteries ; opposed to 
 systole. 
 
 Digestibility. The quality of being digestible. 
 
 Dilatation. Expansion. 
 
 Duode'num. The first of the small intestines; so called from 
 being equal in length to the breadth of twelve fingers. 
 
 Enam'el. The hard exterior surface of the teeth. 
 
 Epidermis. The same as cuticle. (See this.) 
 
186 FIRST LESSONS IN PHYSIOLOGY. 
 
 Epiglottis. A cover on the aperture of the windpipe. 
 Eu-sta' chi-an Tube. A tube extending from the inner side of 
 
 the tympanum and opening at the back of the nostrils. 
 Fetor. A strong, offensive smell. 
 Fi' brine we fibrin. A white, tough, fibrous substance, obtained 
 
 from coagulated blood. 
 
 Function. Performance, office, work, action. (See Ques. 9.) 
 Gan'gli-on, pi. ganglia. A mass of nerve-cells, forming a 
 
 centre from which nervous fibres radiate. 
 Gas 1 trie. Belonging to the stomach. 
 Gloftis. Aperture at the top of the larynx. 
 Hem'or-rhage The loss of blood, bleeding. 
 Herbivorous. Feeding on plants. Herbivore, an herb-animal. 
 Hy'gi-ene. The knowledge of the preservation of health. 
 IFeo-jeju'num. The part of the small intestine immediately 
 
 succeeding the duodenum. 
 In-cis'or. The four front teeth of both jaws. 
 Innervation. The function of the nervous system. 
 Inorgan'ic. Destitute of organs or animation. 
 In-sal-i-va'tion. The mixing of food with saliva. 
 I'ris. A membrane with an aperture in the centre, stretched 
 
 vertically across the eye, and separating the anterior from 
 
 the posterior chamber. The iris gives the eye its color. 
 LaVy-rinth. The internal ear. 
 La<?te-al. A lymphatic vessel of the intestinal canal. (See 
 
 Lymphatic?} 
 
 Lar'ynx. Cavity at the top of the trachea, the organ of voice. 
 Lever. A stiff bar or rod, which turns on, or is supported in, 
 
 a fixed point. 
 Lig'a-menf. A strong fibrous material, uniting bones or other 
 
 solid parts together. 
 Lymphatic. Vessel conveying colorless, watery fluid, called 
 
 lymph, to the thoracic duct. 
 
GLOSSARY. 187 
 
 Mas-ti-ca' tion. The act of chewing. 
 
 Me-dul'la Ob-lon-ga' ta. "The oblong marrow." The portion 
 of the nervous fcord within the skull nearest to the spinal 
 cord. 
 
 Mem'brane. A thin layer of tissue, serving to separate, cover, 
 or envelop other organs. 
 
 Me? far. A grinding tooth. 
 
 Mo' tor. Giving motion. 
 
 Mu'cous Mem'brane, or Muc. Coat. The continuation of the 
 skin, in apertures and interior cavities ; that is, the lining 
 of the internal cavities. 
 
 Mu'cus. A more or less tenacious fluid. 
 
 Nutri'tion. The conversion of food into nutriment. Some- 
 times used to comprise digestion, absorption, respiration, 
 circulation and assimilation. 
 
 CE-soph'a-gus. The tube which extends from the inferior 
 portion of the pharynx to the stomach ; the gullet. 
 
 Organ' ic. Having organs, animation; or, pertaining to 
 organs. Hence, organism = an organic being. 
 
 Ossified tion. The formation of bone. 
 
 Pal' ate. The roof of the mouth 
 
 Pan'cre-as, or " sweet-bread" A gland of the abdomen, under 
 and behind the stomach, at the right of the spleen. 
 
 Pel' vis. Two separate bones to which the legs are attached, 
 and which bound the abdomen below. 
 
 Phys-i-ol'o-gy. The science of the functions of animals and 
 vegetables. Human Physiology is the science which 
 treats of the functions of the human body and the man- 
 ner in which they are brought about. , 
 
 Process* Eminence of a bone ; a portion prolonged beyond 
 others with which it is connected. 
 
 Pul' mo-na-ry . Pertaining to or affecting the lungs. 
 
 Py-lo'rus. The lower or right orifice of the stomach. 
 
188 FIRST LESSONS IN PHYSIOLOGY. 
 
 Refi-na. A very delicate membrane, the continuation of the 
 optic nerve, which lines the hinder two-thirds of the eye- 
 ball. 
 
 Rhythm. A measure of anything according to a number of 
 regularly occurring impulses. 
 
 Rigor mortis. General stiffness of the entire body after death. 
 
 Sa'crum. The triangular bone forming the posterior part of 
 the pelvis, and terminating the vertebral column. It is 
 a union of the 25th, 26th, 27th, 28th, and 29th vertebrae 
 into one great bone. 
 
 Sa-li'va. A thin watery liquid of the mouth, having the prop- 
 erty of converting starch into sugar. 
 
 Sapid 'ity. The quality of bodies that gives them taste. 
 
 Scle-rot'ic. The white of the eye. A tough, firm spheroidal 
 case, the greater part of which is white and opaque. 
 
 Se-cre'tion. The separation of substances from the blood of 
 animals, or from the juice of plants. 
 
 Sensibility. The power which any tissue of the body has of 
 causing changes inherent or excited on it to be perceived 
 and recognized by the mind. 
 
 Se'rum. The watery part of animal fluids, as of blood or 
 milk. 
 
 Skel'e-ton. The solid framework of the body of an animal. 
 
 Sympathetic. A long, double series of ganglia connected 
 together by nervous cords. 
 
 SyJto-le. The contraction of the heart opposed to diastole. 
 
 Tactile. Perceptible to, or susceptible of, touch. 
 
 Temperature. The amount of heat which a body may com- 
 municate to other bodies. 
 
 Ten' don. A white cord attached at one end to a bone and at 
 the other to a muscle; the same as sinew. 
 
 Tho'rax. The chest ; the part of the body between the neck 
 and the abdomen. 
 
GLOSSARY. 189 
 
 Thoracic. Pertaining to the thorax. 
 
 Tissue. A membranous organization of parts. 
 
 Tra'che-a, or Trache'a. A tube strengthened by cartilagi- 
 nous rings extending from the larynx downward along 
 the front part of the thorax, and passing into the thorax 
 where it divides into two branches, a right and a left, 
 called the bronchi. 
 
 Tym'pa-num. The cavity of the middle ear ; the drum. Sep- 
 arated from the external ear by the tympanic membrane. 
 
 Vein. A vessel to convey venous or impure blood to the 
 heart. 
 
 Ven'tride. Generally applied to the two cavities of the heart 
 which communicate with the auricles. Applied also to 
 other cavities in the body. 
 
 Ver'te-bra, pi. Vertebra. One of the bones composing the 
 vertebral column. It consists of a main part, called the 
 body of the vertebra; and of seven projections, called 
 processes. 
 
 Vil'li. Soft projections or processes covering certain mem- 
 branes. 
 
 Vit're-ous Humor. The transparent mass which fills the eye 
 behind the crystalline lens. 
 
INDEX 
 
 PAGE. 
 
 Absorption 120 
 
 Accommodation of the Eye 154 
 
 Adipose tissue 36 
 
 Air, and its rel. to the body.. 87, 92 
 
 Alimentary canal 19, 113 
 
 Animal structure 12 
 
 Animal apparatus of life 166 
 
 Aqueous humor. ....... 153 
 
 Arch of the foot 28 
 
 Arrangement of teeth 21 
 
 Arteries ...64, 67 
 
 Attention 168 
 
 Auricles 59, 61 
 
 Back -bone 24 
 
 Ball and socket joint 28 
 
 Bed 95 
 
 Biceps 35 
 
 Bicuspid 20 
 
 Bile 116 
 
 Blood Action of. 63 
 
 Circulation of 58, 62 
 
 Composition of - 54 
 
 Corpuscles 55 
 
 Quantity of 55 
 
 Sounds 66 
 
 Sp. gravity of. 55 
 
 Uses of 57 
 
 Bones, 13; of the head 17 
 
 Brain 132, 137 
 
 Bronchi 32, 75 
 
 Buildings 95 
 
 PAGE. 
 
 Canines 20 
 
 Capillaries 65, 66, 77 
 
 Carbonic acid gas u, 77 
 
 Cartilages 14, 18, 26, 30, 80 
 
 Chyle 117, 119 
 
 Chyme 117, 119 
 
 Choroid ., 150 
 
 Cheek-bone... 18 
 
 Chest 16 
 
 Cells, cellular tissue 16 
 
 Cells of air in lungs 77 
 
 Centre of ossification 14 
 
 Cerebellum.. 138 
 
 Cerebro-spinal axis 18, 134 
 
 Circulation 58, 62 
 
 Clot-. 54 
 
 Clothing 92 
 
 Coherence 10 
 
 Collar-bone 16, 24 
 
 Composition, n ; of bones... . 13 
 
 Conduction of heat 88 
 
 Contractility 35 
 
 Corpuscles, of blood 55 
 
 " of touch 51 
 
 Cotton 94 
 
 Coughing 8l 
 
 Crystalline lens 153 
 
 Dentine 20 
 
 Dermis 5 1 
 
 Digestibility 103 
 
 Digestion 107, no, in, 113 
 
INDEX. 
 
 191 
 
 PAGE. 
 
 Digestive fluids 115, 1 18 
 
 Direction, visible 157 
 
 Distinct vision 156 
 
 Draught 97 
 
 Drum 1 60 
 
 Duration of imp. on retina 158 
 
 Ear 159 
 
 Enamel 20 
 
 Epidermis 5 1 
 
 Epiglottis 30 
 
 Evaporation ._ 9 
 
 Eye-ball 150 
 
 Eye-tooth 20 
 
 Expiration 78, 79 
 
 PAGE. 
 
 Incisors 20 
 
 Ingredients of bones 13 
 
 Innervation 132 
 
 Inorganic matter 9, II 
 
 Insalivation .-. 109 
 
 Inspiration 78* 79 
 
 Intestinal juice 118 
 
 Intestines 113, 115 
 
 Involuntary muscles 36 
 
 Iris 151 
 
 Irregularity in diet 104 
 
 Insanity 138 
 
 Jaw, upper and lower 1 8 
 
 Knee-pan 28 
 
 Fangs 19 
 
 Fat 36 
 
 Fibrine 54 
 
 Food 12, 104, 105, 106, 107 
 
 Foot 27 
 
 Form 10 
 
 Formula for teeth 21 
 
 Frontal bone 17 
 
 Gastric juice A.- 116 
 
 Glossary of words 183 
 
 Glottis 30 
 
 Glue 51 
 
 Grinders 21 
 
 Gristle .'. 14 
 
 Growth, n; of bones 14 
 
 Hair.. 52 
 
 Hand 27 
 
 Haunch-bone 24 
 
 Head 17 
 
 Hearing, sense of 159 
 
 Heart 12,58,59,61, 83 
 
 Hinge -joint 28 
 
 Hunger 104 
 
 Hydrogen 101 
 
 Ideas, 
 
 Labyrinth l6l 
 
 Larynx 30 
 
 Laughing 82 
 
 Leaping 46 
 
 Lever 39 
 
 Ligaments 29 
 
 Limbs 15, 27 
 
 Linen 94 
 
 Lobes and lobules 75 
 
 Long-sightedness 156 
 
 Lungs 74, 83 
 
 Lymphatic glands 123 
 
 Marrow 13 
 
 Mind 168 
 
 Medulla oblongata 139 
 
 Molars 21 
 
 Muscles 12, 35, 36, 38, 42 
 
 Nails 52 
 
 Neck of 'teeth 19 
 
 Nervous fibres 12, 133, 134, 140 
 
 " matter 12 
 
 system. 130, 136, 137, 140 
 
 Nitrogen 80, 87, 101 
 
 Nose-bone . . 18 
 
 170 
 
192 
 
 INDEX. 
 
 PAGE. 
 
 Occipital bone 18 
 
 Optic apparatus 153 
 
 Organic matter. 9, u 
 
 Organic apparatus of life 166 
 
 Organism n, 12 
 
 Oxygen 12, 80, 87, 101, 103 
 
 Pancreatic juice 117 
 
 Papillae 146 
 
 Pelvis 1 6, 24, 26 
 
 Peristaltic motion 113 
 
 Perception 169 
 
 Perspiration 52 
 
 Physiology, definitions of 171 
 
 Processes 25 
 
 Pulse.., 66 
 
 Questions 173 
 
 Radiation of heat 89 
 
 Requirements of health .. 26, 55 
 
 S 2 , 88 
 
 Respiration 12 
 
 " by the skin 82 
 
 Retina 152 
 
 Rhythm of the heart 63 
 
 " of the respiration 79 
 
 Ribs 25 
 
 Rigor-mortis 36 
 
 Sight 
 Skeleton 
 
 PAGE. 
 
 150 
 .......... i* 
 
 . - ........ H,l8, 24 
 
 Smell, sense of ....... ^ ...... j ^j 
 
 Sneezing .................... g 2 
 
 Snoring ..... ................ g 2 
 
 Sobbing ---- .' ................ g 2 
 
 g nds :--- .............. i59, 162 
 
 Spheno;d-bone .............. 18 
 
 Spinal cord ..... ...... 25, 134, ,139 
 
 Sternum .................... 24 
 
 Stomach ................ no, in 
 
 Structure of higher aniir-als ____ 12 
 
 " of bones ........... 13 
 
 Sympathetic system ....... 135, 140 
 
 Taste, sense of. 
 
 Teeth 
 
 Temperature of body 
 
 Temporal bone 
 
 Tendons 
 
 Thirst 
 
 Thoracic duct 
 
 Thorax 
 
 Thought 
 
 Touch corpuscles. .- 
 
 Touch,. sense of 
 
 Trachea 
 
 Trunk 15, 
 
 Tympanum 
 
 148 
 
 19 
 
 88 
 
 17 
 
 40 
 
 i<H 
 
 124 
 
 16 
 
 170 
 
 146 
 3' 
 
 Sacrum. 26 Veins 67, 
 
 Sclerotic 150 Ventilation 81, 
 
 Secretion 52 Ventricles 59, 
 
 Sensation 144 Vertebrae 18,24, 
 
 Sensation 170 Vision 150, 154, 
 
 Sensibility 36 Voluntary Muscles 
 
 Sensitiveness of retina 158 
 
 Sensory Organs 1/^4 
 
 Serum 54 Walking 
 
 Short-sightedness 157 Waste-materials 12, 
 
 Shoulder blade 16, 25 Windpipe 
 
 Side-bone 17 Woolen 
 
 Sighing 82 .Work 44, 
 
 25 
 [ 36 
 
 4 
 
 102 
 
 31 
 
 94 
 47 
 

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