Fundamentals of human physiology

Front matter

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Chapter I

The Scope of Physiology—The Structural Basis of the Body—The Epithelial Tissue—The Connective Tissue—The Muscular Tissue—The Nervous Tissue—The Gross Structures of the Body— The Skin—The Subcutaneous Tissues—The Muscles—The Body Cavities—The Skeleton—The Bones of the Trunk—The Limbs MnO OT VOREEAU TONS x. OF irajd'-as «ae wid dhe tetdicr doa. s be iw ow Sar adis stale alddeee ole

, CHAPTER II.

THE PHYSICO-CHEMICAL BASIS OF LIFE.

The Chemical Basis of Animal Tissues—Water-Proteins—Lipoids— Carbohydrates—Physico—The Influence of Chemical Laws on Physiological Processes—Properties of Crystalloids—Osmotic Phenomena in Cells—Reactions of Body Fluids—Colloids—GeneralNature of Hnzymes or Perments ... 05.0000. ccc ec ctt ec elas

CHAPTER III. Be THE MUSCULAR SYSTEM

* The General Properties of Muscular Tissues — Contractility — _.____Irritability—The Simple Muscular Contraction—Tetanic Con- 9 traction — Effect of Load— Elasticity of Muscle — Chemical Changes Accompanying Contraction—Rigor Mortis ............

Chapter IV

a THE BLOOD. ee ttroduction—Physical Properties—The Corpuscles—Erythrocytes oe . —Hemoglobin—Enumeration of Blood Corpuscles—The Origin of the Erythrocytes—The White Cells—Leucocytes—Lymphocytes—Estimation of the White Cells—Function of the Leucocytes—The Blood Platelets—The Blood Plasma..... Re ea ye vii

THE STRUCTURAL BASIS OF THE BODY. Page

Vili CONTENTS.

CHAPTER V. THE BLOOD. ; Page

The Defensive Mechanism of the Blood—Coagulation of the Blood —Antibodies in the Blood—The Process of Inflammation— Toxins—Antitoxins—Ehrlich’s Side Chain Theory of Immunity —Anaphylaxis—Phagocytosis—Opsonins—Vaccines—Serum Di- PUTAS 5. 00 5's w'eketnivie pasa this erkiat Maal aa Oe whole Bea {casts 5 oe 53

CuHaprer VI.

THE LYMPH. ‘

Chapter VII. ~ The Circulatory System

Introduction—Anatomical Considerations—The Heart—The Blood Vessels—Physiological Properties of Heart Muscle—Character of Cardiac Contraction—The Sequence of the Heart Beat—The Action of Inorganic Salts on the Heart Beat—The Vascular Mechanism of the Heart—Definition of Terms—Events of the Cardiac Cycle—The Heart Sounds—Diseases of the Cardiac é MLV ie 5 foe hark ve ia ana Rady ab) ol re hipk OO. «gee alm Re Sg 8! Sa ra 70

Chapter VIII. ‘the Circulation

i, Blood Flow Through the Vessels—The Part the Heart Plays— The Part the Arteries Play—Arterial Blood Pressure—Factors Which Maintain the Blood Pressure—Velocity of Blood Flow— The Return of the Blood to the Heart—Circulation Time— Pulsatile Acceleration of the Blood Flow—The Pulse—The Circulation in the Lungs—The Influence of the Nervous System on the Circulation—The Nervous Control of the Heart—The Cardiac Nerves—Accelerator Nerves—Inhibitory Nerves—Relation of the Sympathetic and Vagus Nerves to the Heart—The Cardiac Center—The Cardiac Depressor Nerves—The Nervous Control of the Blood Vessels—Vasomotor Nerves—Vasoconstrictor

_ Nerves—Vasodilator Nerves—Vasomotor Reflexes—The Effect of Gravity on the Circulation—Hemorrhage—Chemical Control of Circulation—Asphyxia—Action of Drugs on Circulation..... 83

.

CONTENTS.

Chapter IX

Introduction—Internal Respiration—Oxidation in the Tissues—Relation of Oxidative Process to Activity—Physical Laws Governing Solution of Gases—Hemoglobin—The Mechanism of the Respiratory Exchange—The Exchange of Carbon Dioxide—The External Respiration—Anatomical Considerations—The Mech-

i anism of Breathing—The Part the Diaphragm Plays—The Part

a _the Thorax Plays—The Movements of the Lungs—Respiratory

es Sounds — Artificial Respiration — Volumes of Air Respired —

Mechanism of Gaseous Exchange in Lungs ..................5.

S

Chapter X. The Respiration

The Nervous Control of the Respiration—Reflex Respiratory Move-

ments — Chemical Control of Respiration — The Effect’ of ws Changes in the Respired Air on the Respiration—Mountain Sickness—Ventilation—The Voice—Mechanism of the Voice— SUEDURE: REVIT t a the es ge Ni Sia Aoi 8 eg Anata, wramet ete OUR Na cat Ge! Gok alka Usarplatene

Chapter XI

ANIMAL HEAT AND FEVER. ‘ he Animal Heat—Normal Temperature—Factors Concerned in Maintaining the Body Temperature—Regulation of Body Tempera- Ret VOE——ABEIDYTOUICS 6.6 oso igs itinine wae ce gras dae eWiedwig ns

Chapter XII. Digestion

—Anatomical Considerations—Blood Supply of the Alimentary g Canal—The Mouth—The Teeth—The Salivary Glands—The : Pharynx—The Stomach—The Small Intestines—The Large In-

4 Necessity and General Nature of Digestion—The Alimentary Canal ix i THE RESPIRATION. Page testines—The Liver and the Pancreas. . ........0..cecccceeves 138 an CONTENTS.

Chapter XIII

DIGESTION. Page

Digestion in the Mouth—Salivary Secretion—The Nerve Supply of the Salivary Glands—The Reflex Nervous Control of Salivary Secretion—General Functions of Saliva—The Hygiene of the Mouth—Tartar Formation and Salivary Calculi—Mastication— Deglutition or Swallowing—The Act of Vomiting. ............ 150

Chapter XIV. Digestion: In The Stomach

The Secretion of Gastric Juice—The Active Constituents of Gastric Juice — The Movements of the Stomach— The Opening of the Pyloric Sphincter—Rate of Discharge of Food from MLC ot OE BID 2 bate ccsd Lage Weare ee ate OhLig Aa Groth bee TEIN 3 Sein ee 163

Chapter XV. Digestion: In The Intestine

Secretion of Bile and Pancreatic Juice—Functions and Composi- . tion of Pancreatic Juice and Bile—Chemical Changes Produced by Intestinal Digestion—Bacterial Digestion in the Intestine— Products of Bacterial Digestion—Protection of Mucous Membrane of Intestine Against Autodigestion—Movements of the Intestines — Action of Cathartics— The Absorption of Food— Resumé of Actions of Digestive Enzymes. ...............e000. 174

Chapter XX. Special Metabolism

Metabolism of Fats—Metabolism of Carbohydrates—Metabolism

THE DUCTLESS GLANDS.

Introduction—Thyroid and Parathyroid Glands—Adrenal Glands—

Pituitary Gland—Spleen—Thymus Gland ..............00c000. 227 CHAPTER XXII.

THE FLUID EXCRETIONS.

The Excretion of Urine—Composition of Urine—Organic Constituents—Urea—Ammonia—Creatinin—Urie Acid—Inorganic Constituents—Abnormal Constituents—The Organs of Excretion —The Blood Supply of the Kidney—Nature of Urine Excretion Micturition—Drugs which act on the Kidney—The Secretions of the Skin—The Sweat Glands—The Sebaceous Glands—The MUMRRIRAES GIRRAS casos g once beet Vecee Rak OT RCOTEMESE Rake Hee 239 pd es

Xii CONTENTS.

CHAPTER XXIII.

THE NERVOUS SYSTEM. Page

The Functions and Structure of the Nervous System—Fundamental Hlements of the Reflex Arc—Integration of the Nervous Sys- PEIN E or iatare Sie ee lok ome eIENT Oe be chins HE Rib e ehelole dtlrc en Ble) cae) Se Tea 251

CHAPTER XXIV.

THE NERVOUS SYSTEM.

Reflex Action—The Nerve Structures Involved in the Reflexes of the Higher Animals—The Receptors of Pain, Touch, Tempera- — ture—Local Anesthesia and Analgesia—The Afferent Fiber— Choice of Paths on Entering Spinal Cord—The Nerve Center —The Efferent Neurone—Types of Reflexes—Spinal Shock— The Essential Characteristics of Reflex Action—Muscular Tone and Reciprocal Action of Muscles—Symptoms Due to Lesions Affecting the’ ReMexes iiss. ke EL wine oe eine ee 256

CHAPTER XXV.

THE NERVOUS SYSTEM.

The Brain Stem—The General Course and Functions of the Cranial — Nerves—The Brain—lInfluence of the Brain on the Reflex Functions of the Spinal Cord—Functions of the Cerebrum—Cerebral Localization — Experimental and Clinical Observations — The Sensory Centers—The Mental Process—Aphasia—The Cerebellum—Relationship to Body Equilibrium—The Semicircular Canals—The Sympathetic Nervous System—General Characteristics—The Course of Some of the Most Important Pathways— Action of Drugs on the Central Nervous System. ............. 268

CHAPTER XXVI.

THE SPECIAL SENSES: VISION.

Optical Apparatus of the Hye—Formation of Retinal Image— Changes in the Eye During Accommodation from Near Vision —The Function of the Pupil—Imperfections in the Optical System of the Eye—Long and Short-Sightedness—Astigmatism, etc.—The Sensory Apparatus of the Eye—The Functions of the Retina—Blind Spot—Fovea Centralis—The Movements of the Eyeballs—Diplopia—Judgments of Vision——Color Vision LOD SAAT ORS 6 U5 acs a, Grog Rhee Dele asen FWALoce Se ete Tk ates lw lata er ee a 285.

CONTENTS. oN as

CHAPTER XXVII.

THE SPECIAL SENSES. Page

Hearing—The Cochlea—How Sound Waves are Transmitted to this by Tympanic Membrane and Auditory Ossicles—Causes of Deafness—Taste—Nature of Receptors for Taste—The Location of the Four Fundamental Taste Sensations—Relationship Between Chemical Structure and Taste—Association Between Taste, Common Sensation of Touch, and Smell— Action of Certain Drugs on Taste—Smell—Nature of the Receptors of Smell (the Olfactory Epithelium) — Nature of MURPNRRNUNEI See's 5 oN Slo in'y Cudehal a ease he iad wae Vie aba Soothe 6 alee eee 297

CHAPTER XXVIII.

REPRODUCTION. ‘

Fig. Page 1, Diagram of a Cell 2.2... cece epee cece eee cece ener e rere ee eeeee 20 ac ely pes OL epithelial COllees sis 5 ive xcs baal no iols Hale ee ea 21 O23) ey pes: Of Oplsheltal COMBS) 5 ites oo tise doe via,s es sieiea seek vib are See 22 4. Connective tissue cells from a chick embryo .............ee8e- 23 5. Fibers from ligamentum nuchae of the 0x .........s0e..eeees 23 6. Segment of a transversely ground section from the shaft of a

MOTE DONG. Fee oths on 5 eal eleiclareb ONS aie ane asp stb breil nee 24 ac. Hab Celis treated, With BICOROL:> 4.2% oc. 6 ses sues cae miele sae 25 8. Cell from smooth muscle of intestine; cross section of smooth

TAUSCLS OF ANTOBUINE 6 oS ici iasah ek cts wate ss 0d oe lo eal Oo ireeal seen ee 25 D.- VOlUntEry Muscle HSPs. 62s 5 es bist pc 3's Cain's Mas acy 25

10.. Large-sized nerve cell with processes ...........eceeeecvveees 26

11. The thoracic and abdominal cavities ......... Ora; Pate Mie eee 28

145. Pnomea-AZeiss Heemocy tometer va .s ese iat a sed on ae ree ever

15. White blood-corpuscles from Wh oie. a Bee Ce ee 55

Gis Position. of the. Heartiin tHe ENOrax sis shaw ae a ks es ete wa a 71

17. Diagram of the heart and large vesselS ..........ccc0ecsccesee 72

18: Diagram of the valves:of the heart... ....s.cns sow seb es eset 73

19. Cross-section of small artery and ‘Vein. 20.5.5. .< vase poe veh te

20. Arterioles and capillaries from the human brain .............. 15

21. Dissection of heart to show auriculo-ventricular bundle........ 78

22. Diagram showing relative pressure in auricle, vestricle and

AOL Cece eS EW CULE Be ARE ale ae BUN WSR Flefus hike ee 80

23. Diagram of experiment to show how a pulse comes to disap-

ILLUSTRATIONS.

pear when fluid flows through an elastic tube when there is repistance to the OULMOW = 0. i. oie eae ceo Fos ae 85 Apparatus for measuring the arterial blood pressure in man... 87 BECtlON OF CAG SUNS hui e ws cs Se alia tie a beh a cle SR ee 92 Effect of stimulating vagus and sympathetic nerves on a frog’s

LL hy op toe nn eariie Arner in RIPE E rrp ya Ee 94 Diagram of structure of lungs showing larynx, bronchi, bron-

Chigleés and alveold. os esc s gtatecdis wie huaieretere ee tk REE a cleew ete 111 ihe positionof the lungs inthe thorax. s.2 34 wos eo ee 113 Hering’s apparatus for demonstrating the action of the respira-

OLY UID ice eb as Sa Se setae soe e aa Gis IEE Tc Ne atte WIDE eee Toahege Sane 114

Diagram to show movement of diaphragm during respiration.. 115 Xiv

ILLUSTRATIONS. XV

Page Position to be adopted for effecting artificial respiration....... 118 A AtE OE AT VINO OSCODE:.,) 5 cteictea a ues gekicers disisia te tin'aefela she © eceligtets 128 Position of the glottis preliminary to the utterance of sound... 128 PRAT ES CNIULONIMOITNOTE SEOUETS 5 52 sN in ice Te ated Soe eokaerasel sare ‘Sherene wtacelevce enn 128 The position of the tongue and lips during the utterance of the DOLLY CMDS Se UG pea Rae Or ge ee gia She Ae er Agape Rana Fare 130 Diagram of the alimentary tube and its appendages .......... 141 Scheme of a longitudinal section through a human tooth ...... 143 Section from the human maxillary gland ..............e.cee0- 144 He StOMIACh ANd dUOGeEDUM OPeNed ... sn Saints Ged new dele dis creel 145 MP ePRILC OS OL CNG SSLOTIACH | 6 ig) 0:0 us 6 ccnvein age rerte aks Sim ROe ee steve eusee 146 Longitudinal section of duodenum near pyloric end ........... 148 Pie microscopic structure Of the Liver’ <:.:..05 scicig soos coe ele ee he 149 Cells of parotid gland showing zymogen granules ............. 150 The nerve supply of the submaxillary gland .............-.-- 151 The changes which take place in the position of the root of the tongue, the soft palate, the epiglottis and the larynx during 3 puevaeeona stase Of Swallowine. kc sie Since os als winsvele Srgueacseete 158 Diagrams of outline and position of stomach as indicated by skiagrams taken on man in the erect position at intervals BREMEN RAL LOW FIRE TOO Oa 22.2 sy io ds Gch: vlodw ho biteond ahdaa lerraeggr ae (eralke ee atioce 164 Diagram of stomach showing miniature stomach separated from main stomach by a double layer of mucous membrane. 165 Diagram of the time it takes for a capsule containing bismuth to reach the various parts of the large intestine ............ 184 Diagram of Atwater-Benedict respiratory calorimeter ....... - 189 PT boat CRE LATED 5 0553 2c brea ee kw aad ws PRle big ec8 2 erred cows Oa lore halos 229 ME BR ee ECUN Gs ONC os ola cio cea 8 SROs Sid 3 as Aa wiofeisnd ew Dalakrgpre ewe 230 SpeIMRER PIL VS CECECLIEG) «5 tnavihesie dial «orale & oe ears Wlaraeie’s vied Oe bhaee arte coe 231 Median sagittal section through pituitary of monkey.......... 235 Before and after onset of acromegalic symptoms ............. 236 The situation, direction, forms, and supports of the kidney.... 243 Longitudinal section through the kidney .............00.e00. 244 eet On UP INALY “SY SCCM. scecok aieiel Fle VOM «3 oiery-eyere a 6 oo etele aes 247 Schema of simple reflex arc .........

Mi Waicreaag NEA 3! pis) ease tele. We ad cere 252 Diagram of nervous system of segmented invertebrate ........ 254 Diagram of section of spinal cord showing tracts ............. 259 mer -Agpece OF. NUMAN “DPAI 2.55 3) 2ce ond sia of ath pase) toe es ace alos weg 269 Vertical transverse section of human brain .................. 270 Cortical centers in man ............ exalts: siclaheher alt alg Ba era hie b 275 mane nomicircular Candis Of The eal -. ile. suk ccs ig is 6 0 04 Cees 282 RISER AEION.OF MINAS OL. FOGG: 5.0 's56) uklscd ote. «sein acolo w din a aheta a ale coat 287

Section through the anterior portion of the eye............... 288

ILLUSTRATIONS.

; A, spherical aberration ; B, chromatic aberration ........... . Errors in TORBOTION (hl bee a we ee Semidiagrammatiec section through the right ear .

Tympanum of right side with the auditory ossicles in place.... § Schema to show the course of $i, taste fibers from ae toy DPA 2503 GE : Coast ory ta ae

COLOR PLATES,

Diagram of ciretilation:< (4:5)... 6a «sev weee ..Facing | Dietetic chart . ct beeen ee Se edeeeus sewen stip cm «ARI Diagram of the uriniferous tubules, the - bedaa'y | and veins of the kidneys......... : 2 The simplest reflex arc in the spinal cord...... “Facin Reflex arc through the spinal cord, in which an inter mediary neurone exists poles the afferent an efferent NeUranes:s Fae PE oe ee Ko

VII. Diagram of the dorsal aspect of the medulla an veeeeeees .Facin: _ Plate VIII.

FUNDAMENTALS OF HUMAN PHYSIOLOGY.

Chapter I. The Structural Basis Of The Body

The Scope of Physiology.—Physiology is the study of the phenomena of living things, just as anatomy or morphology is a study of their structure. The study of anatomy is most logically - pursued by starting with the simplest organisms and gradually proceeding through the more complex forms until man _ is reached. Except for certain fundamental functions, such as nutrition, which are common to all ‘cells, this method is not the most suitable one to pursue in physiology, because in the lowest organisms all of the functions are crowded together in a limited number of cells—indeed, it may be in one single eell. It is easier to study a function when it is performed by a tissue or organ that has been set apart for this particular purpose than when it is performed by cells that do many other things. Another reason for paying more attention to the functions of higher rather than lower animals is that the knowledge which we acquire may be more directly applicable in explaining the functions of man, and therefore in enabling us more readily to detect and rectify any abnormalities.

During the embryonic development of one of the higher animals, a single cell, the ovum, produces numerous other cells, which become more and more collected into groups, in many of which the cells undergo very marked changes in shape and structure, or produce materials, such as the skeleton or teeth, which show no cell structure whatsoever. Thus we have formed the tissues and organs, each having some particular function of 17

18 THE PHYSIOLOGICAL SYSTEMS.

its own, although certain functions remain which are common to all. In other words, as the organism becomes more and more complex, there comes to be a division of labor on the part of the cells that comprise it. The conditions are exactly like those which obtain in the development of a community of men. In > primeval communities there is little division of labor, every individual makes his own clothes, hunts his own food, manufactures and uses his own implements of war, but as civilization begins to appear, certain individuals specialize as hunters and fighters, others as makers of clothing, others as artisans. Although, in its first stages, this division of labor may be far from absolute, for every member of the community must still fight and take part in the building of his hut, yet it soon tends to become more and more so, until, as in the civilized communities of this twentieth century of ours, specialization has become the order of the day.

A good example of a one-celled animal is the ameba, which is often found floating in stagnant water, and which consists of nothing more than a mass of tissue, or protoplasm, as it is called, and yet this apparently simple structure can move from place to place, it can pick up and incorporate with its own substance particles of food with which it comes in contact, it can store up as granules certain of these foodstuffs, and get rid of others that it does not require; it grows as a result of this incorporation, until at last it splits in two and each half repeats the eyele. In other words, this single cell shows all of the so-called attributes of life: movement, digestion and assimilation of food, growth and reproduction. No one of these properties is necessarily confined to living structures alone, for some perfectly inanimate bodies may exhibit one or other of them, yet when all oceur together, we consider the structure to be living.

In the higher animals, these functions are performed by the so-called systems, such as the digestive, the circulatory, the respiratory, the exeretory, the motor, the nervous and the reprodue- . tive, each system being composed of certain organs and tissues which are designed for the special purpose of carrying out some particular function or functions. One function, however, is common to all of the organs and tissues, namely, that of nutrition, id which includes the process by which the digested food is built up into the protoplasm of the cells, or assimilation, and that by which the resulting substances are broken down again, or disassimilation. It is by these processes that the energy of life is set free; the energy by which the tissues perform their functions, and which appears as body heat. Every cell in the animal body is therefore a seat of energy production, and at the same time each is a machine for converting this energy into some definite form of work. In this regard the animal machine differs from a stéam engine, in which energy liberation occurs in the furnace, and conversion of this energy to movement occurs in the pistons. The furnace and the machinery of the animal body are located in the tissue cells, and the digestive, circulatory, respiratory and excretory systems are provided for the purpose of transporting, to and from the living cells, the fuel (i. e., the food), along with the oxygen to burn it and the gases produced _ by its combustion. These processes of assimilation and disassimilation constitute the study of metabolism, the practical side of which is included in the science of nutrition.

The Structural Basis of the Body.

As has been indicated above, the structural and physiological unit of the body is the cell, and the structure and function of any organ depends on the nature of the cells which compose it. The general characteristics of the cells present important similarities, whether it be a cell which forms the whole organism as in the case of the ameba or a cell which forms an infinitesimal part of a higher organism. A cell may be defined as a small mass of protoplasm having a nucleus, and in general, we may regard protoplasm as any material which is endowed with life. It is the physical basis of life, and is not any specifie substance. The protoplasm of the muscle cell is, for example, quite different from that of the nerve cell. Indeed in any single cell there are at least two kinds of protoplasm—one composing the nucleus and the other, the cytoplasm. The nucleus is generally oval or spherical and lies near the center of the cytoplasm,

20 THE EPITHELIAL TISSUES.

which forms the outer protoplasmic mass. The cytoplasm surrounds the nucleus and is more homogenous than the nucleus. There are often granules and small vacuoles in it which represent stages in the metabolism of the cell.

By multiplication and differentiation, the simple cell is finally represented in the body in a number of different forms. These

Vacuoles.

Chromatin network. |K 7,

Spongioplasm.

Linin network. Hyaloplasm.

Nuclear fluid.

Nucleolus.

Nuc.ear membrane.

Chromatin net-knot.

Cell-membrane. }--

Exoplasm, |===

Foreign inclosures. Metaplasm.

Fig. 1.—Diagram of a cell. (Bohm, Davidoff and Huber.)

compose the elemental tissues of the body, the epithelial, the connective, the muscular and nervous tissue. We might also classify the blood and the lymph, as fundamental tissue.

The Epithelial Tissue——This consists almosteentirely of cells with a very small amount of intercellular substance which holds the cells together. This tissue covers the internal and external free surfaces of the body, as the external layers of the -skin, mucous membranes of the mouth, the alimentary canal, the internal surfaces of the body cavities and the secreting cells along the ducts of the various glands of the body. Because of its

wide distribution and function, we find many varieties of epithelial cells. Figs. 2 and 3 illustrate some of the varieties of this tissue.

Mucous.

ay Pavement cell.

Pear-shaped cell.

‘2:

Interstitial cells.

Cc pe

Pavement cells.

Fig. 2.—Types of epithelial cells. (Hill’s Histology.) A, Simple columnar cells from intestine; B, Ciliated epithelium from trachea; C, Epithelial cells from bladder.

The Connective Tissue.—This group of tissues, in which are included the bones, cartilages and tendons, serves as a supporting framework for the muscular, nervous and glandular organs. Its function is entirely one of support. The connective tissue cells are made up of two elements, i. e., cells and intercellular yy a THE MUSCULAR TISSUES.

substance. The intercellular substance is produced by the connective tissue cells and exists in many varieties throughout the body. In places it forms an elastic coat of fibrous material, as in the walls of the blood vessels; it is sometimes dense and — a) : ED Pavement ceil.

Pear-shaped cell.

Interstitial cell.

=. Sar = 25s Se

St Corneum or horny layer,

Stratum

Z 2 saa lucidum, Fe Ses Stratum v2 cups granulosum, OF Malpighian Pla Nhat) or germx inal layer, Ore Se: B Cc

Fig. 3.—Types of epithelial cells. (Hill’s Histology.) A, Section of bladder epithelium: B, Section of epidermis of skin from palm-surface of finger; C, Section of striated epithelium from esophagus. } fibrous in character, as in the fascia which covers the various organs. In bone the connective tissue substance is impregnated with inorganic salts which makes it very hard and firm. Fatty or adipose tissue consists of connective tissue cells in which are deposited large amounts of fat. Neuroglia is another form of connective tissue found in the nervous tissues (Figs. 4, 5, 6 and 7).

The Muscular Tissue.—There are two kinds of muscular tissue, which differ in histological and physiological characteristics, viz.: smooth and striated muscle. The smooth or non-striated kind is found in the muscle coats of the alimentary canal, the coats of the blood vessels, ete. It is made up of

Fig. 4.—Connective-tissue cells from a chick embryo. (Hill’s Histology. )

é € ss OF : Y Cpa a >, a = ~@ * Prine gf SRD eB ab: E Wa. oy cad b

Fig. 5.—a, Yellow elastic fibers from the teased ligamentum nuche of the ox; b, Cross-section of a portion of the ligamentum nuche of the ox. The elastic fibers are grouped in bundles with a few intervening connective-tissue cells. (Hill’s Histology.)

masses of mononucleated spindle-shaped eells (Fig. 8). Close histological examination reveals a faint longitudinal striation in the cells. This form of muscle is not under voluntary control and is therefore sometimes called involuntary.

The striated muscles constitute the tissue which composes the voluntary contractile part of the body. Heart muscle is striated but it differs a little from voluntary muscle in a number of histological and physiological details. The skeletal muscles—so-called because they are attached to and move the bones

—are composed of masses or bundles of striated fibers which —

~ 2 THE MUSCULAR ‘TISSUES. es vary in diameter from .01 to .1 mm. and may sometimes reach an a3 the length of 40 mm. ‘The fibers are inclosed in a sheat, known —

Outer circumferential lamelle,

se --= Haversian canal,’

i : r

_. Interstitial lamellae.

‘ Fig. 6.—Segment of a transversely ground section from the shaft of a long bone, showing all the lamellar systems. Metacarpus of man. (Bohm a oye. and Davidoff. ) , as the sarcolemma. This variety of muscle (Fig. 9) receives its name of striated from the fact that in microscopic preparation its fibrils show a remarkable cross striation, the significance of which is not known.

Connective-tissue cell.

*

Nucleus of fat cell.

Fig. 7.—Fat cells as they appear in sections treated with alcohol. Alcohol dissolves the fat. (Hill’s Histology.)

Fig. 8.—a, Cell from smooth muscle of intestine; b, Cross section of smooth muscle of intestine. (Hill’s Histology.)

Sarcostyles.

Fig. 9.—Voluntary muscle fiber. The sarcoplasm has broken, showing the smooth sarcolemma. (Hill’s Histology.)

The Nervous Tissues.—Nerve tissue is composed of nerve cells and fibers arising from the nerve cell. Such a structure is known as a neurone. The neurone is imbedded and sup- ‘ported by connective tissue, the neuroglia. The long fibers aris-

26 THE GROSS STRUCTURES OF THE BODY.

ing from the nerve cells receive their nourishment from the cell. These may be very long; for example, the nerve cells from which the nerves in our hands or feet arise, are located somewhere in the spinal cord (see Fig. 10). The long process run-

Brush-like telodendrion.

Main dendrite.

Secondary dendrite.

Basal dendrite.

Neuraxis with collaterals.

Fig, 10.—Large-sized nerve cell with processes. (Béhm and Davidoff.)

ning out from the cell is known as an axone, and the shorter more branching process, the dendrite.

The Gross Structures of the Body.

From the fundamental tissues the various parts and organs of the body are developed, just as the various buildings which form a city are built out of the same varieties of building material. The description of the various individual organs of the v alae

Pe ee idl ied ee ee tenet a ee ee ee ee ee ee ee '* > A - ms t - aS na a.

_ body will be found in the appropriate chapters. At present we will concern ourselves with a brief consideration of the gross architecture of the body.

The Skin.—The body is everywhere covered fies the skin. This tissue is built of an outer layer of epithelial tissue and an inner one of connective tissue. The hairs and nails are modifieations of epithelial tissue. In the connective tissues are found the blood vessels and nerves which supply the skin.

THe SuspcuTANgEous Tissue.—dJust beneath the skin is a layer composed of connective tissue. In some places this binds the

_ skin direetly to the bones and in others it separates the skin from the muscles. The subcutaneous fat is found in this layer and is called adipose tissue. The subcutaneous tissue is usually spoken of as fascia.

The Muscles.—The skin and the superficial fascia form a protective covering for the muscles, bones and internal organs. The muscles comprise the lean meat of the body and are formed by a mass of muscle cells which have been described above. The muscle bundles are held together by connective tissue, in which are found the blood vessels and the nerves which supply the muscles. The attachments of the muscles to the bones are known as the origin and the insertion of the muscles. The insertion usually refers to the attachment of the muscle on the bone which has the greatest freedom of movement, when the muscle contracts. The covering of the bone is composed of a fibrous conneetive tissue, called the periostewm. To this the muscles are attached either directly or indirectly, by means of a tough band called a tendon. Whenever. a muscle contracts, the points of attachment are brought closer together.

The Body Cavities——The trunk has two compartments which are filled with the various organs composing the viscera. The upper chamber is called the thoracic cavity and holds the heart and the lungs; the lower chamber, which is separated from the supper by a sheet of muscle called the diaphragm, is the abdominal cavity. This contains, mainly, the viscera concerned in the digestion and absorption of food, and the organs of exeretion,

28 THE BODY CAVITIES.

Fig. 11.—The thoracic and abdominal cavities. (From a preparation by T. Wingate Todd.)

FUNDAMENTALS OF

Fig. 12.—The human skeleton. a photograph by T. Wingate Todd

HUMAN PHYSIOLOGY. 29

The viscera are directly or indirectly attached to the posterior surfaces of the thoracie and abdominal cavities by means of sheets of connective tissue (ealled mesentaries) in which are found the blood vessels and the nerves that Supply the viscera (see Fig. 11). The figures give the general idea of the structure and the position of the various viscera.

The cranial cavity is formed by the bones of the skull, and is. the receptacle for the brain. The cranial cavity is extended by means of a large opening in the base of the skull into the canal formed by the spinous processes of the vertebral column. This canal contains the spinal cord.

The Skeleton.—The bones and cartilages of the body form the skeleton, which is the structural foundation for the soft tissues.

We will consider it in three divisions: the skull, the trunk, and the limbs.

THE BONES OF THE SKULL.— The skull is composed of the bones of the cranium and the face. The cranium is the bony ease which protects the brain. It is formed by the union at their edges of several flat-shaped bones,