u Jv ANATOMY AND PHYSIOLOGY FOR NURSES •Tl t5?) CO2, tells that during the process of combination, one atom of carbon combines with one molecule of oxygen (composed of two atoms) to give one molecule of carbon dioxide. In the action of sodium hydroxide with hydrochloric acid, water and sodium chloride are formed. The equation to represent this, NaOH + HCl -> H2O + NaCl, shows that one molecule of sodium hydroxide reacts with one mole- Chap. I] EXPLANATIONS AND DEFINITIONS 7 cule of hydrochloric acid to give one molecule of water and one molecule of sodium chloride. Oxide. — An oxide is a compound in which another element is in combination with oxygen, as water (H2O), carbon dioxide (CO2), sulphur dioxide (SO2), and iron oxide (Fe203). Acid oxide. — -An acid oxide (or acid anhydride) is an oxide of a non-metal which in combination with water will form an acid, as carbon dioxide and sulphur dioxide, as shown in the following : — CO2 + H2O -> H2CO3 (carbonic acid), SO3 + H2O -> H2SO4 (sulphuric acid). Basic oxide. — A basic oxide (or basic anhydride) is an oxide of a metal which in combination with water will give a base, as calcium oxide (CaO) and sodium oxide (Na20), shown in the following : — . CaO + H2O -^ Ca(0H)2 (calcium hydroxide), NaoO + H2O -> 2 NaOH (sodium hydroxide). Acid. — An acid is a substance which contains hydrogen and an acid radical. The acid radical must contain a non-metal and may contain ox;y'gen. Examples are hydrochloric acid (HCl), sulphuric acid (H2SO4), carbonic acid (H2CO3), hydrobromic acid (HBr), nitric acid (HNO3). Base. — A base is a substance which contains a metal and the hydroxyl (OH) radical. Examples are sodium hydroxide (NaOH) and calcium hydroxide (Ca(0H)2). One exception to this is ammonium hydroxide (NH4OH), which contains the ammonium radical (NH4) instead of a metal. The alkalies are the bases of sodium, potassium, and ammonium ; they give very strong basic action. Both acids and bases give distinctive characteristic actions. Salt. — A salt is a substance containing the metal from a base and the acid radical from an acid. Salts may be obtained by the neutralization of an acid by a base, the characteristic hydrogen of the acid combining with the characteristic hydroxyl of the base to form water, leaving the salt as shown in the following : — Base + Acid —> Water + Salt NaOH +HC1 ^H20 + NaCl (sodium chloride), Ca(0H)2 + H2SO4 -^ 2 H2O + CaS04 (calcium sulphate). 8 ANATOMY FOR NURSES [Chap. 1 SOME GENERAL CHEMICAL ACTIONS Oxidation. — Oxidation is the process in which the element oxj^gen combines chemically with another substance, heat being evolved in the process. The heat evolved may not be perceptible unless the oxidation takes place rapidly, as in the burning of gas, wood, coal, etc. If the substance combines slowly with oxj^'gen, heat may be imperceptible ; for example, iron allowed to lie in moist air is covered with rust due to the union of the iron and oxygen. Also in our bodies some of the carbon from the cells unites with oxj'gen, and thus the temperature of the body is kept up. It is for this reason that ox;>'gen must be taken into the body, which is accomplished by the act of breathing. Neutralization. — Neutralization is the process that takes place in the action of an acid with a base. Water and salt are the products of the reaction. (See Salt.) Hydrolysis. — Hydrolysis can be defined as the chemical change that takes place when a compound in its action with water splits into two other compounds, fixing the elements of water in the process. The action of water with some salts, also the formation of glucose and fructose from cane sugar, may be given as examples, as represented in the following reaction equations : — (Sodium carbonate) (Sodium hydroxide) (Carbonic acid) NasCOa +2H20^ 2 NaOH + H2CO3, (Cane sugar) (Fructose) (Glucose) C12H22O11 + H2O -> CeHiiOe + CeHioOe. Hydration. — Hydration is the process by which water enters into direct combination with another compound to form a single compound which is called a hydrate. As examples might be given, sulphuric acid as a hydrate of sulphur trioxide, calcium hydroxide as a hydrate of calcium oxide, and crystalline cop- per sulphate as a hydrate of anhydrous copper sulphate. The formation of these hydrates in the process of hydration is represented in the following : — Anhydrous substances Hydrates SO3 + H2O :^H2S04 CaO + H2O :^Ca(0H)2 CUSO4 + 5 H2O :^ CUSO4 . 5 H2O. Chap. I] EXPLANATIONS AND DEFINITIONS 9 The reverse process by which a compound is split up into water and an anhydrous compound is called dehydration. This process is represented in the equations by the reverse arrows. ENERGY Energy is ordinarily defined as the power of doing work. As examples of various types of energy might be mentioned : mechani- cal energy, heat energy, electrical energy, and chemical energy. These can be transformed from one form to another. To illustrate : (1) electrical energy can be converted into energy of motion, as evidenced in the motor ; (2) electrical energy can be converted into heat energy, as in the electric stove ; (3) mechanical energy of motion can be converted into electrical energy, as in the dynamo ; also, (4) chemical energy can be transformed into heat energy, as is true in the burning of wood. SOME PHYSICAL TERMS Specific gravity. — By specific gravity is meant the comparison between the weight of a substance and the weight of an equal volume of some other substance taken as a standard. The standards usually referred to are air for gases, and water for liquids and solids. For instance, the specific gravity (sp. gr.) of mercury is 13.6, meaning that mercury is 13.6 times as heavy as an equal volume, of water. Again, the specific gravity of carbon dioxide (air standard) is 1.5, meaning that it is 1.5 times as heavy as an equal volume of air. The specific gravity of solutions, as a salt solution, will neces- sarily vary with the concentration. Diflfusion. — This term in its ordinary use has to do with the tendency of two liquids or two gases of different densities to mix uniformly. Diffusion can take place either when the substances are simply superimposed, or when they are separated by a per- meable membrane. The following illustrations may help to make this clear. 1. When the gases or liquids are not separated by a membrane. (a) If a bottle of hydrogen is inverted over a bottle of chlorine gas, the lighter hydrogen molecules will move down among the chlorine molecules, while the heavier chlorine molecules will move 10 ANATOMY FOR NURSES [Chap. I up to mix with the hydrogen molecules, so that the two will eventu- ally be mixed uniformly. (6) If a layer of water is placed carefully over a layer of sulphuric acid, in such a way that the two do not mix, two distinct layers will be formed with the heavier sulphuric acid at the bottom. The acid molecules will begin to move up and mix with the water molecules, while the water molecules will move down to mix with the sulphuric acid molecules. The action is much slower than with the gases. 2. When the gases or liquids are separated by certain membranes. (c) In the illustration given in (a) if a membrane, permeable to gases, be stretched over the mouth of the bottle, the gases wull mix evenly through it. Also, if a membranous sac of carbon dioxide is placed in a vessel containing oxygen, the two gases will diffuse through the membrane, until the mixture of gases inside and outside is uniform. (d) When a bladder of alcohol is immersed in water, the two liquids will diffuse through the membrane; the water diffusing more rapidly than the alcohol, the bladder will become distended. This subject of diffusion is an important one, as it has a great deal to do with life and with physiological processes. Because of diffusion the heavier carbon dioxide in the atmosphere is pre- vented from settling to the bottom of the atmosphere, thereby forming a layer of the same next to the earth, a condition which would seem to make life impossible. Diffusion of gases through membranes makes possible the exchange of carbon dioxide and oxy- gen through the walls of the lungs. (See page 246.) The explanation of the process is found in the suppositions of the Jcinetic theory that : — 1. There are spaces between the molecules making up all bodies. 2. Molecules are in rapid motion in straight lines, the motion of gas molecules being much more rapid and unrestrained than in the case of liquid molecules. Two forms of diffusion are spoken of distinctively as osmosis and dialysis. Osmosis. — If a solution is separated from the clear solvent by a membrane, which is permeable to the liquid but not to the substance in solution, the liquid will pass through the membrane and the volume on the side of the solution will be increased. Also, Chap. I] EXPLANATIONS AND DEFINITIONS 11 if two solutions of different concentrations are used with the separating membrane, the volume on the side of the solution of greater concentration will be increased. For example, if a carrot with the inside hollowed out is filled with a sugar solution, a long glass tube secured in the opening and the carrot then placed in a vessel of water or a solution of less concentration, the volume of the solution inside the carrot will increase as indicated by the rise in the glass tube. If conditions are reversed and the less concentrated solution is placed in the membrane, the increase in volume will be in the outer vessel. This phenomenon of osmosis, therefore, accounts for the swelling of dried fruits in water and the rising of water into the stems and leaves of plants. (See page 154.) No completely satisfactory explanation is given for this process of osmosis. A most acceptable one, however, is found in the kinetic theory. According to this theory, the molecules of liquid and solute are both bombarding the membrane on each side. The molecules of the liquid can pass through, but the mole- cules of the solute cannot, the membrane, therefore, being called semi-permeable. The number of liquid molecules bombarding the membrane, per unit area, on the side of the clear solvent, or less concentrated solution, will be greater than the number of liquid molecules bombarding the membrane on the side of the more con- centrated solution, hence, more liquid molecules will pass from the less concentrated to the more concentrated solution and the volume of the latter will be thereby increased. This increase will continue until the pressure in both directions is the same. Osmotic pressure. — This is a term that is used indefinitely, and to express a fact rather than an understood force. A possible explanation is as follows : the molecules in their vibratory motion in the process of diffusion exert a certain force which is evident as a pressure when striking against anything in their path. This force or pressure is spoken of as osmotic pressure. When there- fore a solution is held confined the vibratory force or osmotic pressure of the molecules within the mass produces an evident pressure against the sides of the containing vessel. It is to this pressure that the process of osmosis is due, for if the side of a vessel is a permeable membrane, the molecules in pressing against it will pass through. 12 ANATOMY FOR NURSES [Chap. 1 Dialysis. — In this process a permeable membrane is selected which will admit of the passage of a substance in solution. For example, if a tumbler is completely divided vertically into two compartments by a moist piece of membrane and a water solution of common salt is placed in one compartment and a water solution of sugar in the other, it will be found after a time that some of the salt has passed into the solution of sugar, and vice versa some of the sugar into the salt solution. Such an interchange is said to be due to dialysis, and if the process is allowed to go on for some hours, the same proportion of salt and sugar will be found in the solution on each side of the dividing membrane. (See page 154.) Emulsion. — When a substance scatters evenly throughout a liquid in such a finely divided form that it cannot be separated from the liquid by filtration, but has a tendency to separate like matter in suspension, the system is spoken of as an emulsion. This separation may take place in a brief time, or it may require a week, or month, or even a year. Oil shaken thoroughly in water furnishes an example. UNIT FOR MEASURING HEAT Inasmuch as heat is a form of energj'', it is not as simple an under- taking to speak of it in comparative terms as in the case of matter. It is easy for one to visualize five quarts of milk as five times a certain volume that has been taken as a standard and called one quart. So it is also with weights and distances, and the measure- ment of weights, distances, and volumes is a necessary part of our experience. It is quite as urgent that there should be a basis for the comparison of energy values as well as for matter values, else the coal dealer could not place the value of his coal on a basis of its heat-producing qualities, nor could the dietitian plan the meals on a basis of the ultimate energy-producing qualities to the individ- ual. We are only conscious of energy as a result of the effect it produces, consequently, if it is to be measured, it must be on this basis. The units most used for measuring heat are the small calorie and the large calorie. Small calorie. — The small calorie (cal.) is the amount of heat that is necessary to raise one gram of water through one degree centigrade. In the complete combustion of 12 grams of carbon, 94,300 cal. Chap. I] EXPLANATIONS AND DEFINITIONS 13 are liberated, or suflBcient heat energy to raise 943 grams of water through 100 degrees. When 25 grams of sugar are oxidized, 100 calories of heat energy are produced ; therefore, if the sugar is used as a food, the energy produced by the same can be expected to be proportionate to this estimate. Large calorie. — ^The large calorie (cal.) is the amount of heat that is necessary to raise 1000 grams of water through one degree centigrade. This shows the large calorie to be equal to 1000 small calories. (See page 311.) CHAPTER II DEFINITIONS. — CAVITIES OF THE BODY DEFINITIONS Before taking up the subjects of anatomy and physiology in detail, it is well first of all to consider the definitions of these terms as follows : — Anatomy refers to the structure of the body. Physiology refers to the functions of the different parts of the body, in a state of health. Anatomy teaches us what organs a plant or animal has, and how they are arranged with reference to one another. Physiology teaches us the uses to which these organs are put. Anatomy shows what an organ is ; physiology shows what an organ does. Anatomy may be, and usually is, studied upon the dead crea- ture ; physiology can be studied only upon the living creature. Anatomy is sometimes divided into the following branches : — Osteology is the anatomy of the bones. Syndesmology is the anatomy of the joints. Myology is the anatomy of the muscles. Angiology is the anatomy of the vessels. Neurology is the anatomj'^ of the nerves. Splanchnology is the anatomy of tlic internal viscera. Adenology is the anatomy of the glands. Dermatology is the anatomy of the skin. Genesiology is the anatomy of the generative organs. The Anatomical Position. — In describing the body, anatomists always consider it as being in the erect position, with the face toward the observer, the arms hanging at the sides, and the palms of tlie hands turned forward. Surfaces of the Body. — When the body is in the anatomical position, the front, or surface facing the observer, is named the anterior or ventral surface. (See Fig. 1.) The back, or surface directed away from the observer, is named the posterior or dorsal surface. (See Fig. 2.) 14 rfFTH marr on Lrrn.E toe-^ rOURTM DIGIT OH FOOFTTH TOE TMIRO DIGIT OR THIRD T0£ SECOND DIGIT OR SECOND 1 ._ FIRST DIGIT OR GREAT T06 mcrruB ouintto^ " DIGITUS MINIMUM DIGITUS OUARTU» ^ DIGITUS TERTIUS DIGITUS 6ECUNDUS IICITU8 PRIMUS, HALIUX, POlLTH PCOIff lateral J'nfTthT''/''''^, °k n ^-^V ^""^ Anatomical Position. On the right h£hL rlrL "^ r' '^^u'""^ '° ^°^"'^' ^'^ the left in Latin. The right upper pTssib e when itT/ "^ the trunk in order to show the arm more luUy than is possiDie when it hangs perpendicularly. (Gerrish.) 15 MALLEOLUS ExTERNua Fig. 2. — Back View of a Max. On the left lateral half the names of the parts are given in English, on the right in Latin. (Gerrish.) 16 Chap. II] DEFINITIONS 17 The Median Line. — This refers to an imaginary line drawn through the middle of the body, from the top of the head to the middle of the floor between the feet, The parts nearest this line are described as medial, the parts farthest from this line are described as lateral. Internal and External. — These terms are used to designate within and without the body itself, also within and without the body cavities. Proximal and Distal. — Proximal is used to describe a position near the head or source of any part. Distal is used to de- scribe a position distant, or farthest away from the head or source of any part. Periphery. — This term is used to de- scribe the circumference of a circle, hence in anatomy it means the part farthest from the centre. THE HUMAN BODY It is necessary to have the clearest pos- sible conception of the main divisions and -c o t^ _ ^ _ hiG. 3. — Diagrammatic the positions of the different parts of the Longitudinal Section op 11 1 1 11 .1 e jt ,1 THE Trunk AND Head. 1,1, body, and we shall therefore outline the the dorsal cavity; a, the structure of the body as a whole. It is ^p^"^^ portion ; b. the cra- nial enlargement ; c, c, the readily seen that the human body is sep- bodies of the vertebrce form- arable into trunk, head, and limbs; the Te dtLCd ^tSu^ trunk and head are cavities, and contain ties ; 2, 2, the ventral cavity, , . , . 1 1 •! 1 subdivided into thoracic the internal organs, or viscera,^ while the cavity (d), abdominal cavity limbs are solid, contain no viscera, and ^');,^°^ '^f''' ^f^^*-^ ({[= ' ' g, the nasal cavity; /(, the are merely appendages of the trunk. mouth, or buccal cavity. g~i ..' r J.1- -L J rni . i i The alimentary canal (al) is Cavities of the body. — ihe trunk and represented running through head contain two main cavities, and look- the whole length of the ven- tral cavity. ing at the body from the outside we should naturally imagine that these two cavities were the cavity of the head and the cavity of the trunk, respectively. If, however, we di- vide the trunk and head lengthwise into two halves, by cutting 1 Viscera is the plural of the Latin word viscus, which means an organ ; hence viscera are organs contained within the body cavities. Example : heart, stomach, etc. Each of these may be called a viscus. c 18 ANATOMY FOR NURSES [Chap. II them through the middle line from before backwards, we find the trunk and head are divided by the bones of the spine into dorsal and ventral cavities, and not into upper and lower. (See Fig. 3.) 1. Dorsal cavity. — The dorsal or back cavity is a complete bony cavity, and is formed by the bones of the skull, and the vertebrae (bones of the spine). It may be subdivided into: — a. The cranial cavity. — This cavity contains the brain. 6. The spinal canal. — This canal contains the spinal cord, which is continuous wMth the brain. 2. Ventral cavity. — The ventral or front cavity is not a com- plete bony cavity, part of its walls being formed of muscular and Fig. 4. — Position of the Thoracic and Abdominal Organs (Front View). (Morrow.) other tissue ; it is much larger than the dorsal cavity, and may be subdivided into : — Chap. II] CAVITIES OF THE BODY 19 a. Orbital cavity. — The orbital cavity contains the eye, the optic nerve, the muscles of the eyeball, and the lacrimal apparatus. b. Nasal cavity. — The nasal cavity is filled in with the struc- tures forming the nose. c. Buccal cavity. — The buccal cavity or mouth contains the tongue, teeth, and salivary glands. d. Thoracic cavity. — The thoracic cavity, or chest, contains the trachea or windpipe, the lungs, oesophagus or gullet, heart, and the great vessels springing from, and entering into, the heart. Fig. 5. — Position of the Thoracic and" Abdominal Organs (Rear View). (Morrow.) Diaphragm. — The diaphragm is a dome-shaped muscle, and forms a transverse partition between the thoracic and adbominal cavities. 20 ANATOMY FOR NURSES [Chap. II c. Abdoiniiial cui'ity. — The ubdomiiuil cavity contuiii.s the stom- ach, Hver, gall-bladder, pancreas, spleen, kidneys, small and large intestines, etc. /. Pelvic cavity. — The pelvic cavity is that portion of the ab- domen lying below an imaginary line drawn across the prominent crests of the hip bones. It is more completely bounded by bony walls than the rest of the abdominal cavity. It contains the blad- der, rectum, and some of the generative organs. The limbs, or extremities, ui)per and lower, are in pairs, and bear a rough resemblance to one another, the shape of the bones, and the disposition of the muscles in the thigh and arm, leg and forearm, ankle and wrist, foot and hand, being very similar. There is, however, a marked difference between the mobility of the upper and the lower limbs. The shoulder is freely movable, not so the hip. SUMMARY IP- I "■ Cranial cavity — Brain. I h. Spinal canal — Spinal cord. r Eye. Optic nerve. Muscles of tlic eyeball. Lacrimal apparatus. Structures forming the nose. I Tongue. Teeth. Salivary glands. , ^, . f Esophagus — Trachea. (I. Thoracic K ' ^., , < J.ungs — Heart. [ Iil(jod-vessels. The Diaphragm nuiscle separates the thoracic and al)doininal cavities. Stomach — Spleen — Pancreas. Liver — Gall-bladder. Kidneys — Large and small intestines. Bladder — Rectum. Some of the generative I organs. HUMAN BODY Ventral Cavity (I. Orbital cavity b. Nasal cavity | Abdominal cavity /. Pelvic cavity CHAPTER III CELLS, TISSUES, ORGANS, AND SYSTEMS. — EPITHELIAL TISSUE: SIMPLE, TRANSITIONAL, STRATIFIED From the standpoint of the chemist the body is composed of elements. (See page 3.) From the standpoint of the anatomist the body is composed of cells, and they are regarded as the struc- tural units out of which either directly or indirectly it is built. If the substance of any part of the body, i.e. skin, muscle, or blood, is examined with the imaided eye, it appears homogeneous, but if examined with the microscope it is found to be composed of an innumerable number of these minute cells. , It is helpful to re- call that low down in the scale of life we find animals so simple that they are described as consisting of just one cell. As we ascend in the scale of life, we find animals that consist of a greater number of cells, until the human body may be properly described as an enormous aggregate of cells. All the varied activities of the body are the result of the activity of the cells which compose it, and it is very desirable that we early acquire some definite conception of these tiny elementary bodies. CELLS A cell ^ is a minute portion of li\'ing substance or protoplasm which is sometimes enclosed in a cell membrane or cell wall. Within the protoplasm lies a body of definite rounded form, called the nucleus, and this in turn often contains one or more smaller bodies or nucleoli. As the substance of the entire cell is proto- plasm, that portion which surrounds the nucleus is given the name cytoplasm, and the substance of the nucleus is named karyoplasm. 1 The word cell is from the Lutin cella — a cavity — and was first used by bot- anists to describe plant cells, like those of cork and elder pith, which have cavities in their substance. It is now known that most animal cells, and many plant cells, do not have cavities, so that the name is not especially appropriate, but it is too firmly fixed in our language to be abandoned. 21 22 ANATOMY FOR NURSES [Chap. Ill Cytoplasm. — The cytoplasm is a viscid semi-fluid substance, sometimes homogeneous, often granular, and has the appear- ance of a meshwork. In this meshwork are often suspended various passive bodies, such as food granules, pigment bodies, drops of oil or water. These may represent reserve food matters, or waste matters, and are collectively designated as metaplasm. Nucleus. — The structure of the nucleus is similar to that of the cytoplasm, hut it is more solid, and differs in chemical com- position. It is bounded by a membrane which separates it from the surrounding cytoplasm, and may or may not contain the mi- nute spherical bodies termed nucleoli. In some cells no nucleus can be found. It may be assumed as true that at some period of AUnct'ion-lphtrc eticlo«ing two centtosOEDCS. r.i-s(ve bodKt (men. pljsm or Dinplaim) suspended in the cy- lopMsmic meshvork Fig. 6. — Diagram of a cell. (Wilson.) its life every cell had a nucleus, though it may have been lost in the course of development. Centrosome. — The centrosome is an extremely minute body or pair of bodies usually surrounded by a mass of cytoplasm known as the attraction sphere. As a rule it lies in the cytopla.sm, not far from the nucleus, and plays an important part in nuclear division. Life activities in cells. — Since the body is composed of cells, it follows that all the activities of the body are the result of the activities of the cells. These activities produce changes in the protoplasm, the chief of which may be enumerated as follows : — (1) Respiration. — Each cell coming in contact with oxygen absorbs it and combines with it. Whenever this combination takes Chap. Ill] CELLS 23 place, a certain amount of the protoplasm is burned or oxidized, and as a result of this oxidation heat and other kinds of energy are produced, and carbon dioxide, which is a waste product, is evolved. Thus it will be seen that the real purpose of respiration is to furnish oxygen to each individual cell, and to take from the cell the carbon dioxide which it does not need. (2) Metabolism. — Each cell is able to take to itself, and eventu- ally convert into its own substance, certain materials (foods) that are non-living ; in this way the protoplasm may increase in amount, or in other words, the cell may grow. The amount of protoplasm is not permanently increased, because just as much protoplasm is being broken down by the process of oxidation, and removed from the cell, as is added by the process of assimilation. Chemical changes which involve the building up of living material within the cell have received the general name of anabolic changes, or anabolism ; on the other hand, those which involve the breaking down of such material into other and simpler products are known as katabolic changes, or katabolism, while the sum of all the ana- bolic and katabolic changes which are proceeding within the cell is spoken of as the metabolism of a cell. These chemical changes are always more marked as the activity of the cell is promoted by warmth, electrical, or other stimulation, the action of certain drugs, etc. (3) Amosboid movement. — The most obvious physical changes that can sometimes be seen in living protoplasm, by the aid of the microscope, are those which are termed "amoeboid." This term is derived from the amoeba, a single-celled organism which has long been observed to exhibit spontaneous changes of form, accompanied by a flowing of its soft semi-fluid substance. By virtue of this property, the cells can move from one place to another. If one of these cells be observed under a high-power lens of the microscope, it will be seen gradually to protrude a portion of its protoplasm ; this protrusion extends itself, and the main part or body of the cell passes by degrees into the elongated protrusion. By a repetition of this process, the cell may glide slowly away from its original situation and move bodily along the field of the microscope, so that an actual locomotion takes place. When the surface of these free cells comes in contact with any foreign particles, the protoplasm, by 24 ANATOMY FOR NURSES [Chap. Ill virtue of its amoeboid movements, tends to flow round and en- wrap the particles, and particles thus enwrapped or incepted may then be conveyed by the cell from one place to another. (4) Reproduction. — Like all living organisms, each cell grows, produces other cells, and dies, so that each cell has a life cycle compa- rable to, but much shorter than the body itself. As the cells are constantly dying, the need for constant repro- duction is apparent. This reproduction is accomplished in two ways, (a) simple, di- rect division or akinesis, and (6) indirect division or kary- okinesis, which is the almost universal method. Fig. 7. -Diagrams illustrating division of / ) j akhiesis OT direct a cell. A, resting cell with nucleus (n) and ^ ' " "^ v^l ^a centrosome (c). B, preparing to divide, two division the Cell cloUgatCS, asters (a) near nucleus, each with a centro- , , 1 + 1 some, chromatin becoming massed into chro- the nUCleUS and Cytoplasm mosomes. C, two asters have formed a spindle become COUStrictcd in the with chromosomes (ch) in centre. D, each chro- mosome divided and two halves being moved centre, and the Ccll dividcS towfird the asters. E, chromosomes forming ■, « , ii U* V. the two new nuclei, and cell body beginning to ^"^ lOrmS tWO CellS wnicn di\Tde. F, division complete, two-cell stage, ^qqjj gro^y tO the sizC of the each cell has the same structure as the one cell . . , in A. cw, cell-wall. (Bigelow from Wilson.) Original cell. (6) In karyokinesis or in- direct division the nucleus passes through a series of remarkable changes which are rather complicated. A careful study of Fig. 7 will give the student some idea of these changes.^ Differences in cells. — Cells differ in (1) size, (2) form, (3) chemical composition, and (4) function. (1) They vary in size from ^oVo to ^^ o^ of an inch (0.008 to 0.08 mm.) in diameter.^ > For a detailed description of karyokinesis the student is referred to "The Cell in Development and Inheritance," by Wilson. ' On page 469 will be found accurate ratios between the metric system and the system of length, weights, and measures used in the United States. For the sake Chap. Ill] ORGAN 25 (2) The simplest form of cell is spherical, but this is seldom realized except in unicellular plants and animals. In the human body the form of the cell is modified by the pressure of the surrounding structures, by active movements of the cell substance, and by growth and differentiation. (3) It is assumed that the marked difference in the appearance of cells is an expression of a chemical difference, which in turn shows the difference in function. (4) A unicellular animal is in itself a complete living thing, and thus one cell must perform all the essential activities of life, and is self- sufficient. In the human animal the individual cells have become specialized as it were, and certain groups of them perform certain functions, i.e. the function of muscle cells is to contract, and the combined contraction of a group of muscles cells results in the contraction of a muscle. TISSUE A collection of cells of like substance arranged together form what is known as a tissue. In many tissues, all the substance is not inside the cell walls, some of it is between the cells or inter- cellular. In the muscles there is a cement substance between the cells which holds them together. In some tissues there is very little intercellular substance, in others there is a large proportion of it. ORGAN When two or more different tissues are associated in per- forming some special office in the body, the part so adapted is termed an organ. Thus, the lungs are organs specially adapted for assisting in the function of respiration, the bones are organs adapted for support and locomotion, the kidneys for secreting urine, etc. As the structure of an organ depends upon the prop- erties of the tissues composing it, so the characteristics of each tissue depend upon their ultimate structural units — the cells and the intercellular substance. of simplicity in converting figures in the text, from one system to the other, we have assumed 1 cm. to equal | in. (25 mm. = 1 in.). 1 cc. to equal 15 minims. 30 gm. to equal 1 oz. (dry or liquid measure). 30 cc. to equal 1 oz. (dry or liquid measure). 1 litre to equal 1.75 pt. (dry measure). 1 litre to equal 2.11 pt. (liquid measure). 26 ANATOMY FOR NURSES [Chap. Ill SYSTEM An arrangement of organs closely allied to each other and set apart to perform some general function is spoken of as a system. Eight systems are found in the human body. Their names with the functions of each are briefly expressed as follows : — Skeletal system. — Support and locomotion. Muscular system. — Irritability and motion. Vascular system. — Distribution of the body fluids to all the cells. Respiratory system. — To provide oxygen and get rid of carbon dioxide. Alimentary system. — To receive, digest, and absorb the food so as to provide heat, energy, and materials to replace worn-out tissues. Excretory system. — To eliminate the waste products that result from the activities of life. Nervous system. — To control and insure coordination in the working of all the systems in the body. Contains the centres for all the sensations, intelligence, and thought that we recognize as the highest functions of life. Reproductive system. — To insure the continuance of the race by the production of another being. It is important for the student to remember that these different systems are closely related and dependent on each other. While each forms a complete unit, specially adapted for the performance of some function, yet that function cannot be properly performed without the assistance and cooperation of other systems. The most perfect skeleton is not capable of locomotion, unless assisted by the muscular and nervous systems. Any interference with the circulatory system also affects the work of the excretory system, etc. CLASSIFICATIOX By the aid of the microscope the different distinct tissues of which the body is formed are found to be comparatively few in number, and some of these, although at first sight apparently distinct, yet have so much in common in their structure and origin, one with another, that the number becomes still further reduced, until we can distinguish only four distinct tissues, viz. : — Chap. Ill] EPITHELIAL TISSUE 27 1. The epithelial tissues. 3. The muscular tissues. 2. The connective tissues. 4. The nervous tissues. Such fluids as blood and lymph are frequently described as liquid tissues. Origin of tissues. — It has been stated that the cell is the struc- tural unit of the body, and in the beginning the body develops from a single cell named the ovum. The ovum is developed in the ovary and is made fertile by the entrance into it of a cell, known as the spermatozoon formed in the testes of the male. After fertili- zation or impregnation takes place, the cells divide and subdivide until their number is enormously increased. Fig. 8. — Diagrams to illustrate Fertilization of an Egg-cell (Ovum) bt a Sperm-cell (Spermatozoon). .4, e, nucleus of a matured egg-cell ; s, a sperm-cell ready to enter. B, sperm-cell entered and transformed into sperm-nucleus (s). C, sperm-nucleus and egg-nucleus united, fertilization complete. D, division lead- ing to two-cell stage. (Bigelow.) The cells thus formed eventually arrange themselves in the form of a membrane, blastoderm, which is composed of three layers. These layers are known respectively as ectoderm, mesoderm, and entoderm. The ectoderm, or outer layer, forms the epidermis and the nervous system. , The mesoderm, or middle layer, forms the circulatory and urino- genital systems, also the muscles, bones, and other connective tissues. The entoderm or inner layer forms the greater part of the alimen- tary and respiratory tracts, also the liver, pancreas, and other glands. EPITHELIAL TISSUE Epithelial tissue is composed entirely of cells united together by adhesive matter or cement substance. The cells are generally so arranged as to form a skin, or membrane, covering the external surfaces, and lining the internal parts of the body. This mem- brane is seen when the skin is blistered, the thin and nearly 28 ANATOMY FOR NURSES [Chap. IU transparent membrane raised from the surface being epithelial tissue — in this situation called epidermis, because it lies upon the surface of the true skin. In other situations, epithelial tissue usually receives the general name of epithelium. We may classify the varieties of epithelium according to the shape of the cells which compose them, or according to the arrange- ment of these cells in layers. Adopting the latter and simpler classification, we distinguish three main varieties : — 1. The simple, consisting of a single layer of cells. 2. The transitional, consisting of two or three layers. 3. The stratified, consisting of many layers. 1. Simple epithelium. — This is composed of a single layer of cells. The cells forming single layers are of distinctive shape, and have distinctive functions in different parts of the body. The chief varieties are : — a. pavement b. columnar c. ciliated (a) Pavement epithelium. — This is also called squamous or scaly epithelium. The cells form flat, many-sided plates or scales, which fit together like the tiles of a mosaic pavement. It forms very smooth surfaces, and lines the heart, blood-vessels, and lym- phatics, the mammary ducts, the serous cavities, etc. (6) Columnar epithelium. — The colum- nar epithelium is a variety of simple epi- thelium in which the cells have a prismatic shape, and are set upright on the surface which they cover. In profile these cells look somewhat like a close palisade. They taper somewhat toward their attached end, which is set upon a basement membrane. Columnar epithelium is found in its most characteristic form lining the intestinal canal. (c) Ciliated epithelium. — In ciliated epi- thelium the cells, which are generally colum- nar in shape, bear at their free surface little hair-like processes (strongly suggestive of eyelashes) , which are agitated incessantly with a lashing or vibrat- ing motion. These minute and delicate processes are named cilia, Fig. 9. — Simple Pave- ment Epithelium. a, from a serous membrane ; 6, from a blood-vessel. Fig. 10. — Simple CoL- UMN.\R EpITHELIU.M. O, the cells ; b, intercellular substance between the lower end of cells. Chap. Ill] EPITHELIAL TISSUE 29 and may be regarded as active prolongations of the cell-pro- toplasm. The manner in which cilia move is best seen when they are not acting very quickly. The motion of an individual cilium may be compared to the lash-like motion of a short-handled whip, the cilium being rap- idly bent in one direction. The motion does not involve the whole of the ciliated sur- face at the same moment, but is performed by the cilia in regular succession, giving rise to the appearance of a series of waves travelling along the surface like the waves tossed by the wind in a field of wheat. When they are in very rapid ac- tion, their motion conveys the idea of swiftly running water. As they all move in one direction, a current of much power is produced. Function. — Cilia have been shown to exist in almost ever}' class of animal, from the highest to the lowest. In man their use is to impel secreted fluids, or other matters, along the surfaces to which they are attached ; as, for example, the mucus of the trachea and nasal chambers, which they carry toward the outlet of these pas- sages, and thus keep out foreign matter. 2. Transitional epithelium. — This consists of two or three layers of cells. The superficial cells are large and flattened, having on their under surface depressions into which fit the larger ends of Fig. 11. — Ciliated Epithelium from THE Human Trachea. (Highly magnified.) a, large eUiated cell ; d, cell with two nuclei. Fig. 12. — Sectiox of the Transitional Epithelium lining the Bladder. (Highly magnified.) o, superficial ; 6, intermediate ; c, deep layer of cells. (Schafer.) 30 ANATOMY FOR NURSES [Chap. Ill the pear-shaped cells which form the next layer. Between the tapering ends of these pear-shaped cells are one or two layers of smaller, many-sided cells, the epithelium being renewed by division of these deeper cells. This kind of epithelium lines the bladder and ureters. 3. Stratified epithelium. — This consists of main' layers of cells. The cells composing the different layers differ in shape. As a rule, the cells of the deepest layer are columnar in shape ; the next, rounded or many-sided, whilst those nearest the surface are always flattened and scale-like. The deeper soft cells of a stratified epithelium are separated from one another by a system of channels, which are bridged across by numerous fibres. These cells are often described as prickle cells, as when separated they appear beset with spines. They are continually multiplying by cell-division, and as the new cells which are thus produced in the deeper parts increase in size, they compress and push outward those previously formed. Fig. 13. — Section of Stratified Epitheliu.m. c, lowermost columnar cells; P, polygonal cells above these ; fl., flattened cells near the surface. Between the cells are seen intercellular channels, bridged over by processes which pass from cell to cell. (Schafer.) In this way cells which were at first deeply seated are gradually shifted outward and upward, growing harder as they approach the surface. The older superficial cells are being continually rubbed off as the new ones continually rise up to supply their places. Stratified epithelium covers the anterior surface of the eye, lines the mouth, the chief part of the pharynx, the oesophagus, the anal canal, part of the urethra, and in the female the vagina and neck of the uterus. Its most extensive distribution is over the surface of the skin, where it forms the epidermis. Whenever a surface is exposed to friction, we find stratified scaly epithelium, and we may there- fore classify it as a protective epithelium. Chap. Ill] EPITHELIAL TISSUE 31 Function. — The most important functions of epithelial tissue are as follows : 1. Protection. — Some varieties are specially modified so as to form protective membranes. Example — • skin. Other varieties form the top layer of the mucous membranes, and mucous mem- branes are found lining passages that communicate with the ex- terior of the body. Serous membranes are also lined by epithelial cells. These serous membranes line passages that do not com- municate w4th the exterior of the body. 2. Motion. — This is seen in the cilia, which tend to keep the passages to w^hich they are attached clean, and free from foreign material. 3. Absorption. — This is particularly well seen in the digestive tract. To some extent the skin also is capable of absorption. 4. Secretion. — Every secreting organ must contain epithelial cells. Mucous and serous membranes are examples of secreting organs. 5. Special Sensation. — The organs of the special senses contain epithelial cells. Examples — eye, ear, nose, etc. 32 ANATOMY FOR NURSES [Chap. Ill SUMMARY Life activities in cells 1. Respiration The Human body is an enormous aggregate of cells. Cell membrane — may or may not be present. C^loplasm — distinctive name given to protoplasm that surrounds nucleus. Nucleus — a more solid central portion surrounded by a membrane. The protoplasm of the nucleus is Cell . . . . ] called karyoplasm. Nucleolus ^ minute, spherical bodies found in nucleus. Centrosome — one or two extremely small bodies, sur- rounded by attraction sphere, which is made up of cytoplasm. Alwaj's located near nucleus. (Combines with oxygen = oxidation. Liberates heat. Carbon dioxide formed. I Anabolism = building up process. 1 Katabohsm = breaking down process. Amoeboid movements. fAkincsis or direct division. 1 Karyokincsis or indirect division. Size y^Vr? to ^^ of an inch (0.008 to 0.08 mm.). {Pressure. Movements 'of cell. Growth and differentiation. cells 1 Chemical composition — dependent on special work of cell. Function — assist in work of tissue or organ of wliich it forms a part. Metabohsm Reproduction Tissues Organs - are made up of a collection of cells of like substance, with more or less intercellular substance between the cells. are made up of two or more tissues associated to perform a common function. Sj'stem — a group of organs set apart to perform some special function. Skeletal 1 Muscular System \ Vascular Respiratory AUmentary Excretory Nervous All interdependent. Classification offl. Epithelial, tissues 1 2. Connective. 3. Muscular. 4. Nervous. Chap. Ill] SUMMARY 33 Origin of tissues I Imprei gnation — Multiplica- tion of cells — Blastoderm Entoderm (Epidermis. NerVous system. Circulatory. system. Urino-gcni- Mesoderm \ tal system. I tion ot ceils — tsiastoderm ^yr , Connective tissues. Respiratory tract. Alimentary tract. Liver, Pan- creas. Epithelial — a tissue of cells and little intercellular substance. (Pavement or scaly. Columnar. Ciliated. Transitional, consisting of 2 or 3 layers. .Stratified, consisting of many layers. Protection. Motion. Absorption. Secretion. .Special sensation. Classification of Epithelial Tissue Function CHAPTER IV CONNECTIVE TISSUES: AREOLAR, FIBROUS, ELASTIC, ADIPOSE, RECTICULAR, LYMPHOID, CARTILAGE, BONE Following the classification of tissues we have adopted, the next group to be studied is that known as the connective tissue group. Our description of epitheHal tissue was briefly this : a skin or membrane formed of cells, which cells may be of a variety of shapes, and be arranged in one or more layers. It is distinctly a tissue of cells with very little of what we call intermediate or intercellular substance lying between the cells. Connective tissue differs from epithelial tissue in having a great deal of inter- cellular substance lying between the cells. It may be interesting to note that in this form of tissue, the intercellular substance is supposed to develop from the cells. CONNECTIVE TISSUE GROUP These tissues differ considerably in their external characteristics, but are alike (1) in that they all serve to connect and support the other tissues of the body; (2) they are all developed from the mesoderm ; (3) the cellular element is at a minimum, and the intercellular material is at a maximum ; (4) they originate no action, but are acted upon by the other tissues. We may there- fore group them together as follows : — 1 . Areolar tissue. 5. Reticular tissue. 2. Fibrous tissue. 6. Lymphoid tissue. 8. Elastic tissue. 7. Cartilage. 4. Adipose tissue. 8. Bone or osseous tissue. Areolar tissue. — This tissue appears to l)e composed of a multitude of fine threads or films, called fibres. Viewed with a microscope, these fibres are seen to be principally made up of wavy bundles of exquisitely fine, transparent, white fibres, and these bundles intersect in all directions. Mixed with the white 34 Chap. IV] CONNECTIVE TISSUES 35 fibres are a certain number of yellow elastic fibres, which do not form bundles, and have a straight instead of a wavy outline. Between these fibres are open spaces, called areolae,^ that com- municate freely with one another. Lying in the areolae between the bundles of fibres are seen the tissue-cells, of which there are many varieties. If we make a cut through the skin of some part of the body where there is no subcutaneous fat, as in the upper eyelid, and proceed to raise it from the parts lying beneath, we observe that Fig. 14. — Subcutaneous Areolar Tissue from a Young Rabbit. (Highly magnified.) The white fibres are in wavy bundles, the ela.stic fibres form an open network, p, p, vacuolated cells ; g, granular cell ; c, c, branching lamellar cells ; c', a flattened cell, of which only the nucleus and some scattered granules are visi- ble; /, fibrillated cell. (Schafer.) it is loosely connected to them by a soft, filmy substance of con- siderable tenacity and elasticity. This is areolar tissue. Fibrous tissue. — This tissue is intimately allied in structure to the areolar tissue. It consists almost wholly of wavy white fibres, which cohere very closely and are arranged side by side in bundles which have an undulating outline. The spaces between the bundles are occupied by cells arranged in rows, but the cells are 1 Areola is the Latin word for " a small space." Areolar tissue gets its name from appearing full of minute spaces. 36 ANATOIMY FOR NURSES [Chap. IV not a prominent feature of this tissue. The fibres may be some inches long, do not branch, and confer a distinctly fibrous aspect on the parts which they compose. ' ' ■ Fibrous tissue is white, with a ^ ,^, ^ peculiarly shining, silvery aspect. It is exceedingly strong and tough, yet perfectly pliant ; but it is almost devoid of extensibilitv and is very 1^' I sparingly supplied with nerves and j blood-vessels. j Elastic tissue. — In elastic tissue Q ' I the wavj' white bundles are com- ^- ! paratively few and indistinct, and : there is a proportionate develop- ,. / ment of the elastic fibres. When present in large numbers, they give a yellowish color to the tissue. This Fig. 15. — Fibrocs Tissue, from form of connective tissue is extensile THE Longitudinal Section of a , , . . i i • i Tendon. The spaces between the and elastic in the highest degree, Te'^:.'''tiZ:iZ\T'^'''''"^' ^^^ wherever located, .does such work as India rubber would do. It is not so strong as the fibrous variety, and breaks across the direction of its fibres wiien forcibly stretched. Function. — These three varieties of connective tissue (areolar, fibrous, clastic) agree closely with one another in elementary structure. It is the different arrangement of the cells and fibres, and the relative proportion of one kind of fibre to the other, that gives them their different characteristics. They are used for purely mechanical purposes. Areolar tissue forms web-like binding and supporting material and serves to connect and insulate entire organs. It is one of the most general and most extensively distributed of the tissues. It is, moreover, continuous throughout the body, and from one region it may be traced without interruption into any other, how- ever distant, — a fact not without interest in practical medicine, seeing that in this way air, water, pus and other fluids, effused into the areolar tissue, may spread far from the spot where they were first introduced or deposited. Fibrous tissue is met with in the form of : — Chap. IV] CONNECTIVE TISSUES 37 (1) Ligaments. — Ligaments are strong flexible bands, or cap- sules, of fibrous tissue that help to hold the bones together at the joints. (2) Tendons or sinews. — Tendons are white glistening cords or bands which serve to attach the muscles to the bones. They are usually composed of white fibres, but may contain some yellow fibres. (3) Aponeuroses. — Aponeuroses are flat, wide bands of fibrous tissue which serve to connect one muscle with another. (4) Protecting sheaths or membranes. — Fibrous tissue is found investing and protecting different organs of the body. Examples — heart and kidneys. (5) Fascioe. — The word fascia means a band or bandage. It is most frequently applied to sheets of fibrous membrane which are wrapped around muscles, and serve to hold them in place. Fas- ciae are divided into two groups, which are associated with the skin and the muscles. They are called : — a. Superficial. h. Deep. a. Superficial fascia. - — The subcutaneous areolar tissue, which forms a nearly continuous covering beneath the skin, is classed as superficial fascia. It varies in thickness, and usually permits free movement of the skin on the subjacent parts. The fascia covering the palms of the hands is named palmar fascia, and the fascia covering the soles of the feet is named plantar fascia. The palmar and plantar fascia are much thicker, stronger, and more closely attached than the superficial fascia in other parts of the body. 6. Beep fascice. — The deep fasciae are sheets of white, flexible fibrous tissue, employed to envelop and bind down the muscles, also to separate them into groups. The term fascia, unless limited by an adjective, is usually employed to designate the deep fascial. Subcutaneous areolar tissue is rarely called by the name fascia, though it is correctly classed as such. Elastic tissue, being extensile and elastic, has a most important use in assisting muscular tissue, and so lessening the wear and tear of muscle. It is found : — (1) Between the transverse processes of the vertebra in elastic bands. (Ligamenta flava.) 38 ANATOMY FOR NURSES [Chap. IV (2) In the walls of the blood-vessels (especially arteries), air tubes, and vocal cords. (3) Entering' into the formation of the lungs and uniting the cartilages of the laryn.x. Adipose tissue. — When fat begins to be formed, it is deposited in tiny droplets ' in some of the cells of the areolar tissue ; these Fig. 16. — A Few Fat Cells fkom the Margin of a F.\t Lobule. (Very hiRhly magnified.) f.g. fat globules distending a fat cell ; n, nucleus ; w, membra- nous envelope of the fat cell ; c, capillary vessel ; v, veinlet ; c.l. connective-tissue cell ; the fibres of the connective tissue are not shown. (Schafer.) droplets increase in .size, and eventually run together so as to form one large drop in each cell. By further deposition of fat the cell becomes swollen out to a size far beyond that which it possessed originally, until the protoplasm remains as a delicate envelope surrounding the fat drop. The nucleus is crowded off to one side and attached to the cell wall. As these cells increase in number they collect into small groups or lobules, which lobules are for the most part lodged in the meshes of the areolar tissue, and are also supported by a fine network of blood-vessels. This fatty tissue exists very generally throughout the body, accompanying the still more widely distributed areolar tissue in most parts, though not in all, in which the latter is found. Still, its distribution is not • The contents of the fat cells of adipose tissue are fluid during life, as the normal temperature of the body is considerably above the melting point of the mixture of fats found there. Chap. IV] CONNECTIVE TISSUES 39 uniform, and there are some situations in which it is collected more abundantly. This tissue is found chiefly : — (1) Underneath the skin, in the subcutaneous layer. (2) Beneath the serous membranes or in their folds. (3) Collected in large quantities around certain internal organs, especially the kidneys, which it helps to hold in place. (4) Filling up furrows on the surface of the heart. (5) As padding around the joints. (6) In large quantities in the marrow of the long bones. Function. — Adipose tissue serves several important purposes. (1) Unless formed in abnormal quantities it confers graceful out- lines. (2) It constitutes an important reserve fund, which when required can be returned to the blood and oxidized, thus producing heat and energy. (3) It serves as a jacket or covering under the skin, and being a non-conductor of heat, prevents the too rapid loss of heat through the skin. (4) It is an admirable packing material, and serves to fill up spaces in the tissues, and thus af- fords support for delicate structures such as blood-vessels and nerves. Reticular or retiform ^ tissue. — This variety of connective tissue consists of a close network of white fibres with few, if any, yellow. Fig. 17. — Retiform Tissue from a Lymph Node, r, r, r, represent ope^ meshes of this tissue. (Quaiii.) fibres. The meshes of the network are small and close in sOme parts, more open and like areolar tissue in other parts. The fibres are nearly covered by fibrous tissue cells in the form of broad^ thin 1 Reticulum (from the Latin reticulum "a small net"). Resembling a small net. 40 ANATOMY FOR NURSES [Chap. IV plates wrapped around them. It forms a fine framework in many organs. Lymphoid or adenoid ' tissue. — This is reticular tissue in which the meshes of the network are occupied by lymph corpuscles. This is the most common condition of retiform tissue. Function. — Lymphoid tissue forms the principal part of the substance of the spleen and lymph nodes. It also enters into the composition of the tonsils and some of the intestinal glands. Cartilage. — This is the well-known substance called " gristle." Although cartilage can be readily cut with a sharp knife, it is never- theless of very firm consistence, but at the same time highly elastic, so that it readily yields to exten- sion or pressure, and immediately recovers its original shape when the constraining force is with- drawn. When a very thin section is examined with a microscope, it is seen to consist of nucleated cells disposed in small groups in a mass of intercellular substance. This intercellular substance is some- times transparent, and to all ap- pearances structureless ; some- times it is pervaded with white fibres and sometimes with yellow fibres. According to the amount and texture of the intercellular substance, we distinguish three principal varieties : — (1) Hyaline or true cartilage. (2) White fibro-cartiloge. (3) Yellow or elastic fihro-cartilage. Hyaline cartilage. — This variety is named from the Greek word for glass. A comparatively small number of cells are em- bedded in an abundant quantity of intercellular substance which has the appearance of ground glass. White fibro-cartilage. — The intercellular substance is pervaded Z. SAILS Fio. 18. — Articular Hyaline Cartilage from the Femur of an Ox. s, intercellular substance; p, pro- toplasmic cell ; n, nucleus. (Ranvier.) 1 Adenoid (from the Greek aden, "a gland," and eiodos, " form" or "resemblance." Pertaining to or resembling a gland. Chap. IV] CONNECTIVE TISSUES 41 with bundles of white fibres, between which are scattered cartilage cells. It closely resembles white fibrous tissue, and is found wherever great strength, combined with a certain amount of rigid- ity, is required. Yelloiv, or elastic, fibro-cartilage. — The intercellular substance is pervaded with yellow elastic fibres which form a network. In the meshes of the network the cartilage cells are found. Function. — The function of cartilage is roughly the same throughout, the qualifying terms are used to denote differences in structure and appearance rather than in function. 1. Hyaline cartilage covers the ends of the bones in the joints, where it is known as articular cartilage. 2. Hyaline cartilage forms the rib cartilages, where it is known as costal cartilage. In both these situations the cartilages are in immediate connec- tion with bone, and may be said to form part of the skeleton, hence frequently described as skeletal cartilages. The articular cartilages, in covering the ends or surfaces of bones in the joints, provide these harder parts with a thick, springy coating, which breaks the force of concussion, and gives ease to the motion of the joint. The costal cartilages, in forming part of the solid framework of the thorax or chest, impart elasticity to its walls. Hyaline cartilage also enters into the formation of the nose, ear, larynx, and trachea. It strengthens the substance of these parts without making them unduly rigid, maintains their shape, keeps open the passages through them where such exist, and gives attachment to moving muscles and connecting ligaments. White fibro-cartilage is found joining bones together, the most familiar instance being the flat, round plates or disks of fibro- cartilage connecting the bones of the spine and the pubic bones. In these cases the part in contact with the bone is alw^ays hyaline cartilage, which passes gradually into the fibro-cartilage. Yellow, or elastic, fibro-cartilage is found in the epiglottis, carti- lages of the larynx. Eustachian tube, and external ear. Cartilage is not supplied with nerves, and very rarely with blood-vessels. Being so meagrely supplied with blood, the vital processes in cartilage are very slow, and when a portion of it is absorbed in disease or removed by the knife, it is regenerated very slowly. A wound in cartilage is usually at first healed by 42 ■ ANATOMY FOR NURSES [Chap. IV connective tissue proper, which may or may not become grad- ually transformed into cartilage. Nearly all cartilages receive tiieir nourishnuMit from the perichondrium which covers them, and which is a moderately vascular fil)r()us membrane. Bone, or osseous tissue. — Bone is connective tissue in which the intercellular substance which is derived from the cells is rendered hard by being impregnated with mineral salts. The mineral, or earthy, substance which is deposited in bone, and which makes it hard, consists chiefly of phosphate of calcium, with about a fifth part of carbonate of calcium, and a small portion of other salts. The organic, or soft, matter consists chiefly of blood-vessels and connective tissue, and may be resolved by boiling almost entirely into gelatine. It is possible to separate each of these substances. The min- eral matter may be removed by soaking a bone in dilute acid for several days. The result will be a tough, flexible, elastic substance, consisting only of organic matter. The shape of the bone will be preserved, but the specimen will be so free from stiffness that it may be tied in a knot. The organic matter may be driven off by heat. As before, the shape of the bone will be preserved. The specimen will consist only of mineral matter, will appear white, rigid, and so brittle it can bo crushed between the fingers. Amount of organic and inorganic matter. — The comparative amount of organic and inorganic matter found in bone is dependent on the age of the individual. In the foetus the tissues that later become bone are either fibrous or cartilaginous. By absorption of mineral substances from the blood, these tissues gradually become ossified. Thus it follows that in youth the organic matter is in excess. In adult life the organic matter constitutes about one-third of the weight of the bone, and the inorganic matter two-thirds. In old age the amount of inorganic matter is increased. Fractiure. — The term "fracture" is applied to the breaking of a bone. As a result of the greater amount of organic matter in the bones of children, they are flexible, bend easily, and do not break readily. In some cases the bone bends like a bough of green wood. Some of the fibres may break, but not the whole bone, hence the name " green-stick fracture." It is also true that the greater Chap. IV] CONNECTIVE TISSUES 43 "^'mm amount of inorganic matter in the bones of the aged renders the bones more brittle, so that they break easily and heal with diflSculty. Rachitis or Rickets. — In the disease called rickets, quite com- mon among poorly nourished children, there is not sufficient min- eral matter, so that the bones are flexible, bend easily, and may be permanently misshapen. Structure of Bone. — On sawing a bone it will be seen that in some parts it is open and spongy, whilst in others it is dense and close in texture, appearing like ivory. We thus dis- tinguish two forms of bony tis sue : — (1) The cancellated, or spongy. (2) The dense, or compact. On closer examination, however, it will be seen that the bony matter is everywhere po- rous, and that the difference between the two varieties of tissue arises from the fact that the compact tissue has fewer spaces and more solid matter between them, while the can- cellated has larger cavities and more slender intervening bony partitions. In all bones the compact tissue is the stronger ; it lies on the surface of the bone and forms an outer shell or crust, whilst the lighter, spongy tissue is contained within. The shafts of the long bones are almost entirely made up of the com- pact substance, except that they are hollowed » u out to form a central canal, — the medullarv j I canal, — which has a fibrous lining called en- z e dosteum, and contains marrow. ^ The hard substance of both varieties is ar- ranged in bundles of bony fibres, or lamellae (layers) . Fig. 19. — Vertical T 11 1 u 1 Section of a Long Cancellated bone. — In cancellated bone the bone. (Gerrish.) lamellae join and meet together so as to form a structure resembling lattice- work {cancelli), whence this tissue receives its name. In the interstices of this kind of bone we find the blood-vessels supported by the marrow. Compact bone. — In compact bone the lamellae are usually arranged f\ ^SS 44 ANATOMY FOR NURSES [Chap. IV in rings around canals, — Haversian canals, — which carry blood- vessels in a longitudinal direction through the bones. Between the lamellae are branciied cells which lie in cell-spaces, or cavities, called lacunae (little lakes), and running out in a wheel-like or radial di- rection from each lacuna are numerous tiny wavy canals called cana- liculi, connecting one lacuna with another, and forming a system of minute channels which communicate with each other and with the Haversian canal. This constitutes an Haversian System, so named from Havers, a celebrated anatomist. Many such systems may be found in the shaft of a long bone. The spaces between these systems are filled by lamellae arranged at irregular angles. Marrow. — Marrow consists of fi})rous tissue with blood-vessels, fat-cells, marrow-cells and red corpuscles. There are two distinct kinds of marrow, yellow and red. Yellow marrow contains a larger per cent of fat, and is found in the medullary canals of the long bones. Red marrow contains less fat, but is highly vascular and occupies the spaces in cancellous bone. The function of marrow is (1) to support the blood-vessels, lymphatics, and nerves; (2) to ser^•e as a source of nourishment for bone ; and (3) as a location for the formation of red corpuscles. (See page 143.) Periosteum. — All bones are covered, except at the joints, by a vascular fibrous membrane, the periosteum (around the bone). It consists of an outer fibrous layer and an inner vascular layer. The attachment of the periosteum to bone is rendered firmer by inward prolongations of the fibrous layer called the fibres of Sharpey. Blood-vessels. — Unlike cartilage, the bones are plentifully sup- plied with l)lood. If we strip the periosteum from a fresh bone, we see many bleeding points representing the canals (Volkman's) through which the blood-vessels enter and where they leave the bone. These blood-vessels proceed from the periosteum to join the system of Haversian canals. Around the Haversian canals the lamellae are disposed, while lying between them, arranged in circles, are found the lacunae, which contain the bone-cells. Running from one lacuna to another in a radial direction through the lamellae towards the centre are the canaliculi. Following this scheme, it will be seen that the innermost canaliculi run into the Haversian canals, and thus is established a direct communication between the blood in these canals and the cells in the lacunae connected with and surrounding each Haversian canal. In this way the whole sub- OSTCOGENETIC CELLS LAMELL/C LACUN/E CANALICUL HAVERSIAN CANAL COMPLETE AVEHSIAN SYSTEM Fig. 20. — Diagram of the Structure of Osseous Tissue. A small part of a transverse section of the shaft of a long bone is shown. At the uppermost part is the periosteum covering the outside of the bone ; at the lowermost part is the endosteum lining the marrow cavity. Between these is the compact tissue con- sisting largely of a series of Haversian systems, each being circular in outline and perforated by a central canal. In the first one is shown only the area occupied by a system ; in the second is seen the concentric arrangement of the lamellae ; in the others, respectively, canaliculi ; lacunae ; lacunae and canaliculi ; the contents of the canal, artery, vein, lymphatic, and areolar tissue ; lamellae, lacunae, and canaliculi ; and finally all of the structures composing a complete system. Between the systems are circumferential and intermediate lamellae, only a few of which are represented as lodging lacuna>, though it is to be understood that lacunae are in all parts. The periosteum is seen to be made up of a fibrous layer and a vascular [ayer, and to have upon its attached surface a stratum of cells. From the fibrous layer project inward the rivet-like fibres of Sharpey. (Gerrish.) 45 46 ANATOMY FOR NURSES [Chap. IV stance of the bone is penetrated by intercommunicating channels, antl the nutrient matters and mineral salts from the blood in the Haversian canals can find their way to every part. Function of periosteum in growth of bone. — In the embryo the toiindation of the skeleton is laid in cartilage, or in primitive connective tissue, ossification of the bones occurring later. The hardening or ossification of the bones is accomplished by the penetration of blood-vessels and bone-cells, called osteoblasts, from the periosteum. As they penetrate into the cartilaginous or membranous models, they absorb the cartilage and connective tissue and deposit the true bone tissue at various points until they form the i)articular bony structure with which we are familiar. Regeneration of bone. — A fracture is usually accompanied l)y injur\- to the periosteum and tissues. This results in inflam- mation, which means an increased amount of blood is sent to the part. The plasma and white blood corpuscles from the blood exude into the tissues and form a viscid substance, which sticks the ends of the bone together, and is called callus. Usually bone-cells from the periosteum and lime salts are gradually deposited in the callus, which eventually becomes hardened and forms new bone. Occasionally the callus does not ossify and a condition known as fibrous union results. The periosteum is largely concerned in this process of repair ; for if a portion of the periosteum be stripped ofl"', the subjacent bone will be liable to die, while if a large part or the whole of a bone be removed, and the periosteum at the same time left intact, the bone will wholly or in a great measure be regen- erated. SUMMARY CONNECTIVE TISSUE — A tissue of cells with a great deal of inter- ccUular substance, which is derived from the cells. 1. Resemble each other in function. Reasons for Classification { 2. Resemble each other in origin. 3. Resemble each other in structure. Areolar, Reticular, Fibrous, Lymplioid, Elastic, Cartilage, Adipose, Bone. Areolar tissue. — Formed hy interlacing of wavy bundles of white fibres and some straight elastic fil)res with cells lying in the spaces. Fibrous tissue. — Formed of wavy bundles of white fibres only, with cells in rows between bundles. \'ery strong and tough but pUant. Classification Chap. IV] CONNECTIVE TISSUES 47 Function - Elastic tissue. — Formed of yellow elastic fibres with few bundles of white fibres. It is extensile and elastic. ■ Areolar tissue connects, insulates, forms protecting sheaths, and is continuous throughout the whole body. Fibrous tissue is found in form of ligaments, tendons, apo- neuroses, protecting sheaths, and fasciae. Elastic tissue serves same purpose as India rubber. Saves wear and tear of muscles. Found in ligamenta flava, blood- vessels, air-tubes, vocal cords, lungs, and larynx. Adipose tissue. — ■ Modification of areolar tissue, with cells enlarged and filled with fat. Distribution quite general but not uniform. 1. Confers graceful outlines. 2. Forms a reserve fund for the production of heat and energy. 3. Prevents the too rapid loss of heat. .4. Serves to protect and support delicate organs. Reticular tissue. — ■ Network of white fibres with few yellow fibres. Cells wrapped around fibres. Lymphoid tisstie. — Reticular tissue with meshes of network occupied by Ijaiiph corpuscles. Function. — Lymphoid tissue forms the structure of the spleen and lymph- nodes. Also enters into composition of glands and mucous membranes. Cartilage. — Cartilage or gristle is a bluish white tissue, firm and elastic, covered and nourished by perichondrium. ,, ,. ., Articular Hyaline cartilage Function Varieties • Skeletal. Costal 2. White fibro-caitilage. 3. Yellow fibro-cartilage. Hyaline — Small number of cells in an abundant quantity of intercellular substance. Found as articular cartilage, covering ends of bones in joints. Found as costal cartilage, connecting ribs and sternum, or one rib with another. White Fi6ro — Intercellular substance pervaded with white fibres. Re- sembles fibrous tissue. Found between spinal and pubic bones. Yellow Fibro — Intercellular substance pervaded with network of yellow elastic fibres. Found in parts of throat and ear. Serves as cushions for ends of bones. Makes a flexible connection between the ribs and the sternum, or be- tween one rib and another. Strengthens and maintains shape of certain organs without rigidity. (Serves as strong, flexible connecting material between bones, and around some joints. (Strengthens and maintains shape of certain organs, and yet allows of certain amount of elasticity. Hyaline Cartilage Function 48 ANATOMY FOR NURSES [Chap. IV & o M CO CO O Qi O CO M O n Composition Varieties Canals Haversian System I Haversian (Calcium phosphate. Calcium carbonate. Small portion of other salts. i Blood-vessels. Connective tissue. Marrow. Cancellated or .spongy. Dense or compact like ivory. [ Medullary — Yellow Marrow. I Blood-vessels. I Lymphatics. Haversian canal. Lamellae — bony fibres arranged in rings around Haversian canal. Lacunae — small spaces between lamellae occupied b,v bone cells. Canaliculi — canals which radiate from lacunae to the Haversian canal. Endosteum — A fibrous membrane that lines the medullary canal. Fibrous tissue, blood-vessels, fat-cells, mar- row cells, and red corpuscles. (Yellow — found in medullary canals of long bones. Red — occupies spaces in cancellous bone. 1. Supports blood-vessels, Ijmaphatics, and nerves. 2. Serves as a source of nourishment for bone. 3. Serves as location for formation of red corpuscles. Periosteum — A vascular fibrous membrane that covers the bones and serves to nourish them. Important in reunion of broken bone and growth of new bone. ( Fibres of Sharpey — Inward prolongations of periosteum. Marrow Consists of Varieties Fimction CHAPTER V THE SKELETON Function. — The bones are the principal organs of support, and the passive instruments of locomotion. Connected together in the skeleton, they form a framework of hard material, affording at- tachment to the soft parts, maintaining them in their due posi- tion, sheltering such as are of delicate structure, giving stability to the whole fabric, and preserving its shape. The entire skeleton in the adult consists of two hundred and six named bones. These are : — Cranium 8 Face 14 f Malleus 2 Ear Incus 2 6 [ Stapes 2 Hyoid 1 The spine, or vertebral column (sacrum and coccyx included) 26 Sternum and ribs 25 Upper extremities 64 Lower extremities 62 206 In this enumeration the sesamoid^ bones, which are found em- bedded in tendons covering the bones of the knee, hand, and foot, are not included. CLASSIFICATION The bones may be divided, according to their shape, into four classes: 1. Long, 2. Short, 3. Flat, and 4. Irregular. Long bones. — A long bone consists of a shaft, and two extrem- ities. The shaft is formed mainly of compact tissue, this compact tissue being thickest in the middle, where the bone is most slender 1 Ses'amoid [from the Greek sesamon, a "seed of the sesamum " and eidos, "form," "resemblance"], resembling a grain of sesamum. E 49 50 ANATOMY FOR NURSES [Chap. V and the strain greatest, and it is hollowed out in the interior to form the medullary canal. The extremities are made up of can- cellated tissue with only a thin coating of compact substance, and . PARIETAL -TEMPO RA I. CARPUS METACARPUS Fig. 21. — The Human Skeleton. (Morrow.) are more or less expanded for greater convenience of mutual con- nection, and to afford a broad surface for muscular attachment. All long bones are more or less curved, which gives them greater strength and a more graceful outline. The long bones are as follows : — Chap. Y] THE SKELETON 51 2 Clavicle 2 Tibia 2 Humerus 2 Fibula 2 Radius 10 Metacarpals 2 Ulna 10 Metatarsals 2 Femur 56 Phalanges 90 Short bones. — The short bones are small pieces of bone ir- regularly shaped. Their texture is spongy throughout, excepting at their surface, where there is a thin crust of compact substance. The short bones are the sixteen bones of the carpus, and the four- teen bones of the tarsus. Some authors include the two patellae. Flat bones. — Where the principal requirement is either exten- sive protection or the provision of broad surfaces for muscular attachment, the bony tissue expands into broad or elongated flat plates which are composed of two thin layers of compact tissue, enclosing between them a variable quantity of cancellous tissue. The flat bones are as follows : — 1 Occipital 2 Lacrimal 2 Parietal 2 Scapula 1 Frontal 1 Sternum 2 Nasal 24 Ribs 1 Vomer 2 Hip bones 38 Irregular bones. — The irregular bones are those which, ok account of their peculiar shape, cannot be grouped under either of the preceding heads. The irregular bones are as follows : — 24 Vertebrae 2 ]\Ialar 1 Sacrum 2 Maxillse 1 Coccyx 1 Mandible 2 Temporal 2 Palate 1 Sphenoid 2 Inferior turbinated 1 Ethmoid J. Hyoid 40 The bones of the ear are so small that they are described as ossicles and do not fit in any of these groups. Processes and Depressions. — If the surface of any bone is examined, certain projections and depressions are seen. The pro- 52 ANATOMY FOR NURSES [Chap. V jections are called processes. The depressions are called fossae or cavities, and either a qualifying adjective is used to describe them, or a special name given to them. Processes and depressions are classified as : 1. Articular, 2. Non-articular. The articular are provided for the mutual connection of bones to form joints. The non-articular serve for the attachment of ligaments and muscles. The following terms are used : — Prucc.ss. — Any marked bony prominence. Tuberosity. — A large process. Tubercle. — A small process. Syinous. — A sharp, slender process. Cre^t. — A narrow ridge of bone. Condyle. — A rounded or knuckle-like process. Head. — A portion supported on a constricted part or neck. Fossa. — A depression in or upon a bone. Cavities. — The terms sinus ' and antrum are applied to cavities within certain bones. Meatus or Canal. — A long tube-like passageway. Fissure. — A narrow slit. Foramen. — A hole or orifice through which blood-vessels, nerves, and ligaments arc transmitted. DIVISIONS OF THE SI^LETON In taking up the various divisions of the skeleton, we will consider it as consistins: of — 1. Head or skull 2. Ilyoid. 3. Trunk . . Cranium. Face. Vertebrae. Sternum. I Ribs. 4. Upper extremities. 5. Ix)wer extremities. The head or skull. — The head or skull rests upon the spinal column, and is formed by the union of the cranial and facial bones. It is divisible into — 1. Cranium or brain case, and 2. Anterior region, or face. ' The term "sinus " is also used in surgeiy to denote a narrow tract leading from the surface down to a cavity. Chap. V] THE SKELETON 53 BONES OF THE CRANIUM Occipital 1 Parietal 2 Frontal 1 Temporal 2 Ethmoid 1 Sphenoid 1 Occipital bone. — It is situated at the back and base of the skull. At birth the bone consists of four parts, which do not vertex Sinciput Occiput Fig. 22. — Side View of the Skull. (Morrow.) Attention of the student is called to the text, page 64, where the word Mandible is used in preference to the term Inferior Maxillary which is found on the illustra- tion. The word Maxilla is also used in preference to Superior Maxillary. unite into a single bone until the sixth year. The internal sur- face is deeply concave, and presents many eminences and depres- sions for the reception of parts of the brain. There is a large hole — the foramen magnum — in the inferior portion of the bone, for the transmission of the medulla oblongata (the con- stricted portion of the brain) where it narrows down to join the spinal cord. At the sides of the foramen magnum it presents 54 ANATOMY FOR NURSES [Chap. V two processes called condyles, which articulate with the first vertebra. Parietal bones. — The right and left form by their union the greater part of the sides and roof of the skull. The external sur- face is convex and smooth ; the internal surface is concave, and Ftg. 23. — Front View of the Skull. (Morrow.) See note under Figure 22 regarding use of Mandible and Maxilla in pr«ferer.ce to Inferior Maxillary and Superior Maxillary. Note also that the spelling o^ the word Lachrymal differs from the more correct spelling found in the text, as per the B. x\. A. presents eminences and depressions for lodging the convolutions of the brain, and numerous furrows for the ramifications of arteries which supply the dura mater (membrane which covers the brain) with blood. Frontal bone. — It resembles a cockle shell, and not only forms the forehead, but also enters into the formation of the roof of the orbits, and of the nasal cavity. The arch formed by part of the frontal bone over the eye is sharp and prominent, and is known as Chap. V] THE SKELETON the supraorbital margin. Just above the supraorbital margins are hollow spaces called the frontal sinuses (see Fig. 33) which are filled with air and open into the nose. In the upper and outer angle of each orbit are two depressions called lacrimal fossae for the reception of the glands of the same name, which secrete the tears. At birth the bone consists of two pieces, which afterwards become united along the middle line, by a suture ^ which runs from Fig. 24. — Occipital Bone. Inner surface. the vertex of the bone to the root of the nose. This suture usually becomes obliterated within a few years after birth, but it occasion- ally remains throughout life. Temporal bones. — The right and left are situated at the sides and base of the skull. They are named temporal from the Latin word tempus, time, as it is on the temple the hair first becomes gray and thin, and thus shows the ravages of time. The temporal bones are divided into three parts — the hard, dense portion, called petrous; a thin and expanded scale-like portion, called squamous; and a mastoid portion, which is prolonged down- 1 See Figs. 61 and 62. 56 ANATOMY FOR NURSES [Chap. V "^^ Fig. 25. Pariet.\l Bone. Inner surface. ^4, parietal depression; E, fur- row for ramification of arteries. ward and forms the mastoid process. This process is filled with a number of connected cancellous .spaces, containing air, and called mastoid cells.' They communicate with the cavity of the middle ear. The condition known as mastoiditis means in- flammation of the lininj: of these cells. Supraorbital Margin Roof of Orbital Cavity ' Cells. — The student must bear in mind that the word cell is used with two different meanings in anatomy. Histologically speaking, the word "cell" refers to one of the component units of the body, such as an "epithelial cell" or "nerve cell." In connection with the use of the words "mastoid cells" in the text, the word "cells" refers to tiny enclosed hollow chambers similar to the cells of a honey-comb. Chap. V] THE SKELETON 57 The internal ear, the essential part of the organ of hearing, is contained in a series of cavities, channelled out of the substance of the petrous portion. Between the squamous and petrous por- DIGASTRIC FOSSA Fig. 27. — The Right Temporal Bone. Outer surface. The dotted lines indicate the lines of suture between squamous, mastoid, and petrous portions. (Gerrish.) tions is a socket, called the glenoid fossa, for the reception of the condyle of the lower jaw. Ethmoid bone. — -It is an exceedingly light cancellous bone that forms part of the orbits, nasal fossae, and base of the cranium. It consists of a horizontal plate, a verti- cal plate, and two lateral masses. The horizontal plate forms the roof of the nasal fossae, and also closes the anterior part of the base of the cranium. It is pierced by numerous foramina or holes, through which the nerves conveying the sense of smell pass. Descending from the horizontal plate is the vertical plate which helps to form the nasal septum, and on either side the lateral masses help to form the side walls of the nasal fossse. The lateral masses contain a Fig. 28. - Ethmoid Bone. Seen fromunder surface. 2,criD- number of thin-walled cavities called riform or perforated plate. 58 ANATOMY FOR NURSES [Chap. V T ZoM^UA^. the ethmoidal sinuses, wliich communicate with the nasal fossae. Descending from the horizontal plate on either side of the septum are two processes of very thin, cancellous, bony tissue, named the superior and middle tur- binated processes. Sphenoid bone. — It is situated at the an- terior part of the base of the skull and binds the other cranial bones to- gether. It helps to form tlie cavities of the cra- nium, orbits, and nasal fossae. In form it some- what resembles a bat ^ „„ ^ with extended wings, Fig. 29. — Parietal, Temporal, and Sphe- . -i j NOiD Bones. Posterior aspect. 1, body of sphe- and IS described aS COn- noid bone; 2, 2, preater wings of sphenoid bone; • j.' „ _f _ U^J,, +,,r„ 3, 3, parietal bones ; 4, 4, mastoid process of tem- ^^^l^mg 01 a DOQJ , tWO poral bones. (Gould's Dictionary.) pairs of wiugS, and two pterygoid processes. The body is joined to the ethmoid in front and the occipital be- hind. It contains cavities which are called sphenoidal sinuses. They communicate with the nasal fossae. THE SKULL AS A WHOLE The cranium is a firm case or covering for the brain. Four of the eight bones which form this bony covering are classed as flat bones. They consist of two layers of compact tissue, the outer one thick and tough, the inner one thinner and more brittle. The cancellated tissue lying between these two layers, or " tables of the skull," is called the diploe. The base of the skull is much thicker and .stronger than the walls and roof; it presents a number of openings for the passage of the cranial nerves, blood-vessels, etc. The bones of the cranium begin to develop at a very early period of fcetal life. Thus, before birth the bones at the top and sides of the skull are separated from each other by membranous tissue in which bone is not yet formed, and being then imperfectly Chap. V] THE SKELETON 59 Fig. 30. — Skull of Xew-born Child. To show moulding. (Edgar.) ossified, they are readily moulded, and they overlap one another more or less during parturition. The spaces at the angles of the bone occupied by the membra- nous tissue are termed the fon- tanelles, so named from the pulsations of the brain, which can be seen in some of them and which the early anatomists lik- ened to the rise and fall of water in a fountain. There are six of these fontanelles. Anterior Fontanelle. — The anterior fontanelle is the larg- est, and is a lozenge-shaped space between the angles of the two parietal bones and the two segments of the frontal bone. It remains open until the second year, and occasionally persists throughout life. Posterior Fontanelle. — The posterior fontanelle is much smaller in size, and is a triangular space between the occipital and two parietal bones. This is closed by an extension of the ossifying process a few months after birth. (See Figs. 61 and 62.) The other four fontanelles, two on each side of the skull, are placed at the inferior angles of the parietal bones ; they are un- important. Small, irregular os- sicles called sutural bones (Wor- mian bones) are found in the sutures of the head, chiefly near the fontanelles, and often assist in the closure of the fontanelles. Sinuses of the head. — Four sinuses communicate with each nasal cavity : the frontal, ethmoid, sphenoid, and maxillary or an- trum of Highmore. The mucous membrane which lines the nose also lines all of these sinuses, and inflammation of this membrane may extend into any of them and cause sinusitis. (See Fig. 90.) Fig. 31. — Skull of New-born Child To show moulding. (Edgar.) 60 ANATOMY FOR NURSES [Chap. V BONES OF THE FACE Nasal 2 Vomer 1 Inf. Turbinated 2 Lacrimal 2 Malar 2 Palate 2 Maxillffi 2 ISIandible 1 14 Nasal bones. — They are two small oblong bones placed side by side at the middle and upper part of the face, forming by their junction " the bridge " of the nose. Vomer. — It is a single bone placed at the lower and back part of the nasal cavity, ami forms part of the central septum of the nasal fossae. It is thin, and shaped somewhat like a ploughshare, but varies in different individuals, being frequently bent to one or the other side, thus making the nasal chambers of unequal size. Inferior turbinated bones. — Thcv are situated in the nostril. Fig. 32. — Nasal Bones. Viewed from before. (Ger- rish.) ANTER TINE GROOVE HARD PALATE Fig. 33. - Sagittal Section of Face, a Little to the Left of the Middle Line, showing the Vomer and its Relations. (Gerrish.) Chap. V] THE SKELETON 61 LACRIMAL PROCESS ETHMOID PROCESS Fig. 34. — Right Inferior Turbinate Bone. External surface. (Gerrish.) on the outer wall of each side. Each consists of a layer of thin, cancellous bone, curled upon itself like a scroll ; hence its name, "turbinated." They are below the superior and middle turbi- nated processes of the ethmoid bone. Abnormal conditions of these bones and the membranes covering them cause some of the more common nasal diseases. (See Fig. 140.) Lacrimal bones. — Are the smallest and most fragile bones of the face. They are situated at the front part of the inner wall of the orbit, and resemble somewhat in form, thinness, and size, a finger-nail. They are named lacrimal because they contain part of the canal through which the tear duct runs. Malar, or yoke bone. — Forms the prominence of the cheek, and part of the outer wall and floor of the orbit. A prominent spine of bone projects backward from the body of the malar, and articulates by its free extremity with the corresponding spine projecting forward from the temporal bone, thus making the two members of the true arch known as the zygo- matic arch. Palate bones. — They are shaped like an " L," and form (1) the back part of the roof of the mouth ; (2) part of the floor and outer wall of the nasal fossae; (3) a very small portion of the floor of the orbit. Fig. 35. — Lacrimal Bone. FRONTAL PROCESS ZYGOMATIC PROCESS-"" MhXILLARV PROCESS Fig. 36. — Right Malar Bone. Outer surface. (Gerrish.) 62 ANATOMY FOR NURSES [Chap. V Maxillae, or upper jaw-bones, also known as superior maxillary. — The maxilhv are two in number (right and left) and are the prin- gXTAL PRoc, PTERYGOID FOSSA Fig. 37. The Two Pal.\te Bones in their N.\tuu.\l Position. Dorsal view. (Gcrrish.) cipal bones of the face. Each bone assists in forming (1) part of the floor of the orbit, (2) the floor and outer wall of the nasal fossa?, (3) the greater })art of the roof of the mouth. These bones usually unite before birth to form one bone. When they fail to do so we have the condition known as cleft palate. From NA3AL ROCCSS POSTERIOR OEN- '. T«L CANALS i FRAORBITAL FO R A M E N ASAL NOTCH TERIOR NASAL SPINE Fig. 38. — The Right Ma.xilla. Outer surface. (Gerrish.) a surgical point of view, it is the most important bone of the face, on account of the number of diseases to which it is liable. That part of the bone which contains the teeth is called the al- Chap. V] THE SKELETON 63 veolar process, and is excavated into cavities, varying in depth and size according to the size of the teeth they contain. The body of the bone is hollowed out into a large cavity known as the antrum of Highmore, which opens into the nose. Abnormal conditions of either the nose or teeth may cause an infection of these antrums. Mandible, or lower jaw-bone, also known as inferior maxillary. — It is the largest and strongest bone of the face. At birth, it ENTAL PROTUBERANCE Fig. 39. — The Mandible. Viewed from the right and a little in front. (Gerrish.) consists of two lateral halves, which join and form one bone during the first or second year. It serves for the reception of the lower teeth, and undergoes several changes in shape during life, owing mainly (1) to the first and second dentition, (2) to the loss of teeth in the aged, and (3) the subsequent absorption of that part of the bone which contained them. It articulates, by its condyles, with the sock- ets in the temporal bones, which allows for free move- ment in mastication. Hyoid bone (os hyoi- deum). — Is an isolated U- shaped bone lying in front of the throat, just above the laryngeal prominence (Adam's apple). It supports the tongue, and gives attachment to some of its numerous muscles. Fig. 40. ^- The Hyoid Bone. Viewed from the left and in front. (Gerrish.) 64 ANATOMY FOR NURSES [Chap. V TRUNK The hoiu's which enter into tlie formation of the trunk consist of the vertebrae, sternum, and ribs. The vertebral column as a whole. — It is formed of a series of bones called vertebra^, and in a man of average height is about CERVICAL VERTEBRJC b K THORACIC VERTEBRiC LUMBAR VERTEBRA Fig. 41. — The Vertebral Column. Right lateral view and dorsal view. (Gerrish.) twenty-eight inches long. In youth the vertebrae are thirty-three in number, and according to the position they occupy are named : — Chap. V] THE SKELETON 65 Cervical, in the neck 7 Thoracic, in the thorax 12 Lumbar, in the loins 5 Sacral, in the pelvis 5 Coccygeal, in the pelvis ..... 4 The vertebrae in the three upper portions of the spine are separate and movable throughout the whole of life, and are known as true vertebrse. Those found in the sacral and coccygeal re- gions are, in the adult, firmly united, so as to form two bones, five entering into the upper bone, or sacrum, and four into the ter- minal bone of the spine, or coccyx. They are known as false vertebrae, and on account of their union the number of vertebrae in the adult is twenty-six. The bodies of the vertebrae are piled one upon another, forming a strong, solid pillar, for the support of the cranium and trunk, the arches forming a hollow cylinder behind for the protection of the spinal cord. Viewed from the side, it presents four curves which are alternately convex and concave. The two concave ones are called primary curves because they exist in foetal life and are designed for spinous rrocr., i'"^^CC' the accommodation 1\*^^~ ^ *' of viscera. The other L^^ "' m two are called second- ary or compensatory curves because they AHicuiar./ ^ Process ~ ))!» miiir enable the child to as- \ m sume the erect atti- Trausverse^:^/ ^im\\..-i->^ ^" young subjects it consists of ** three separate parts, and al- Fig. 53^- Development OF THE Hip though in the adult these have UONE. bhowing the union of the three portions in the acetabulum. (Gerrish.) become United, it is USUal to de- Chap. Y] THE SKELETON 75 scribe the bone as divisible into three portions : (1) the ihum (plural ilia), (2) the ischium (plural ischia), (3) the pubis (plural pubes). The ilium is the upper broad and expanded portion which forms the prominence of the hip. The ischium is the lower and strongest portion of the bone, while the pubes is that portion which forms the front of the pelvis. Where these three portions of the bone meet and finally ankylose is a deep socket, called the acetabulum, into which the head of the femur fits. Other points of special interest to note in the hip bones are : — (1) The spinous process formed by the projection of the crest of the ilium in front, which is called the anterior superior spinous process, and which is a well-known and convenient landmark in making anatomical and surgical measurements. (2) The largest foramen in the skeleton, known as the thyroid foramen, situated between the ischium and pubis. (3) The symphysis pubis, or pubic articulation, which also serves for a convenient landmark in making measurements. The pelvis. — The pelvis, so called from its resemblance to a basin, is stronger and more massively constructed than either the Female Pelvis. cranial or the thoracic cavity. It is composed of four bones, the two hip bones forming the sides and front, the sacrum and coccyx- completing it behind. It is divided by a narrowed bony ring into 76 ANATOMY FOR NURSES [Chap. V the large (false), and small (true) pelvis. The narrowed bony ring which is the dividing line is spoken of as the brim of the pelvis, the ilio-pedineal line, and the strait. The large pelvis is all that expanded portion of the pelvis situated above the brim ; it forms an incomplete or false basin. The small pelvis is all that portion situated below the brim. Its cavity is a little wider in every direc- tion than the brim itself, while the large pelvis is a great deal wider. The small bony pelvis is a basin with incomplete walls of bone, . Fig. 55. — Male Pelvis. the bottom of which is composed of the softer tissues, muscles, and ligaments. The opening of the small pelvis, i.e. the space just above the brim, is called the inlet, and the opening below is called the inferior strait, or outlet. The female pelvis differs from that of the male in those particu- lars which render it better adapted to pregnancy and parturition. It is more shallow than the male pelvis, but wider.in every direction. The inlet and outlet are larger, the bones are lighter and smoother, and the coccyx is more movable. As can be seen by looking at Fig. 54 and Fig. 55 a distinctive anatomical difference is that the sub-pubic angle in a male is less than a right angle, and in the female it is greater than a right angle. Chap. Y] THE SKELETON 77 Femur, or thigh bone. — It is the longest, largest, and strongest bone in the skele- ton. The upper extremity of the femur, like that of the humerus, consists of a rounded head joined to the shaft by a constricted neck, and of two eminences, called the greater and lesser trochanters. The head ar- ticulates with the cavity in the hip bone, called the acetabulum. The lower ex- tremity of the femur is larger than the upper, is flattened from before back- wards, and divided into two large eminences or condyles by an intervening notch. It articulates with the tibia and the patella, or knee- cap. In the erect position it is not vertical, being sep- arated from its fellow by a considerable interval, which corresponds to the entire breadth of the pelvis, Fig. 57. — The Right Patella. surface. (Gerrish.) Condyles Fig. 56. — The Right Femur, or Thigh Bone. Anterior view. (Morrow.) but the bone inclines gradually down- ward and inward, so as to approach its fellow towards its lower part, in order to bring the knee-joint near the line of gravity of the body. The degree of inclination va- ries in different persons, and is greater in the female than the male, on account of the greater breadth of the pelvis. Patella, or knee-cap. — It Ventral 78 ANATOMY FOR NURSES [Chap. V ^^ tuberosity is the largest sesamoid bone in the body. It is small, flat, tri- angular in shape, and placed in front of the knee-joint, which it serves to protect. It articulates with the two condyles of the femur, and is separated from the skin by a bursa. (See page 131.) Tibia, or shin bone. — Is situated at the front and inner side of the leg. The upper extremity is large, and expanded into two lateral eminences with concave surfaces, which receive the con- dyles of the femur. The lower extremity is much smaller than the upper ; it is prolonged down- wards on its inner side into a strong process, the medial (or inner) malleolus. It articu- lates with the fibula and one of the bones of the ankle. (In the male, its direction is verti- cal and parallel with the bone of the opposite side; but in the female it has a slight oblicpie direction outwards, to compensate for the oblique di- rection of the femur inwards.) Fibula, or calf bone. — Is situated at the outer side of the leg. It is the smaller of the two bones, and, in propor- tion to its length, the most slender of all the long bones ; it is placed nearly parallel with the tibia. The upper ex- tremity consists of an irregu- lar quadrate head by means of which it articulates with the tibia. The lower extremity is prolonged downwards into a pointed process, the lateral (or external) malleolus, which lies just beneath the skin. It articulates with the tibia and one of the bones of the ankle. Tarsus. — The tarsus is composed of seven small bones united by ligaments, but the tarsal bones differ from the carpal in being larger and more irregularly shaped. The largest and strongest Outer malleolus Fln^TED.^SDTURE. ^lic thrcc most important sutures are as follows : — (1) Coronal. — The line of union between the frontal and parietal bones. (2) Lambdoidal. — The line of union betw^een the parietal and occipital bones. 82 Chap. VI] ARTICULATIONS 83 (3) Sagittal suture. — This begins at the base of the nose, extends along the middle line on the top of the crown, separates the frontal bone into two parts/ the parietal bones from each other, and ends at the posterior fontanelle. Fig. 61. — Diameters and Landmarks of the Fcetal Skull. Upper sur- face. (Edgar.) Synchondrosis is usually a temporary form of joint. The cartilage between the bones ossifies before adult life. Example : the union of the sphenoid and occipital bones. 1 That portion of the sagittal suture which separates the frontal bone into two parts is often called the frontal suture. (See Fig. 61.) 84 ANATOMY FOR NURSES [Chap. VI Fig. 62. — Diameters and I.andmahks of the Fcetal Skull. Posterior surface. (Edgar.) AMPHIARTHROSES, OR SLIGHTLY MOVABLE JOINTS The above terms apply to joints that permit of slight movement and include two varieties: (1) symphysis, and (2) syndesmosis. Symphysis. — In this form of articulation the bony surfaces are joined together by broad, flattened disks of fibro-cartilage, as in the articulations between the bodies of the vertebrse. These intervertebral disks being compressible and extensile, the spine can be moved to a limited extent in every direction. In the pelvis the articulation between the two pubic bones (symphysis pubis), and between the sac- rum and ilia (sacro-iliac articulation), are slightly movable. The pubic bones are united by a disk of fibro-cartilage and by ligaments. In the sacro-iliac articulation the sacrum is united more closely to the Fio. 63. — A Slightly Movable Joint, a, b, disk of fibro-cartilage ; c, articular cartilage ; d, bone. Chap. VI] ARTICULATIONS 85 ilia, the articular surfaces being covered by cartilage and held together by ligaments. The fibro-cartilage between these joints (symphysis pubis and sacro-iliac) becomes thickened and softened during pregnancy and allows of a certain limited motion which is essential to a nor- mal parturition. Syndesmosis. — When the bony surfaces are united by an interosseous ligament, as in the lower tibio-fibular articulation, it is called syndesmosis. 5VN0VIAL FOLD DIARTHROSES, OR FREELY MOVABLE JOINTS This division includes the complete joints, and are the only joints in which the three following conditions are found : — (1) The bones are united by fibrous ligaments, forming more or less perfect capsules. The ligaments are not always so tight as to maintain the bones in close contact in all positions of the joint, but are rather tightened in some positions and relaxed in others, so that in many cases they are to be looked on chiefly as controllers of movements, and not as serving solely to hold the bones together. The bones are partly held together in these joints by atmospheric pressure and largely by the surrounding muscles. (2) A secreting membrane (synovial) lines the capsule and is so arranged that it dips in between the edges of the oppos- ing articular cartilages. (See Fig. 64.) (3) Each articular end of the bone is covered by hyaline cartilage, which provides surfaces of remarkable smoothness, and these surfaces are lubricated by the synovial fluid secreted from the delicate synovial membrane which lines the cavity of the joint. The varieties of joints in this class have been determined by the kind of motion permitted in each. They are as follows : — (1) Gliding joint. — The articular surfaces are nearly flat, and Fig. G4. — A (Vj.mplete Joint. The synovial membrane is represented by dotted lines. 86 ANATOMY FOR NURSES [Chap. VI admit of only a limited amount of gliding movement, as in the joints between the articular processes of the vertebra?. (2) Hinge joint. — The articular surfaces are of such shape as to permit of movement to and fro in one plane only, like a door on its hinges. These movements are called flexion and extension, and may be seen in the articulation of the arm with the forearm, in the ankle joint, and in the articulations of the phalanges. (3) Ball and socket joint. — In this form of joint a more or less rounded head is received into a cup-like cavity, as the head of the femur into the acetabulum, and the head of the humerus into the glenoid cavity of the scapula. Movement can take place freely in any direction, but the shallower the cup, the greater the extent of motion. The shoulder joint is the most freely movable joint in the body. (4) Pivot joint. — In this form, one bone rotates around another which remains stationary, as in the articulation of the atlas with the axis (epistropheus) and in the articulation of the ulna and radius. In the articulation of the ulna and radius the ulna re- mains stationary, and the radius rotates freely around its upper end. The hand is attached to the lower end of the radius, and the radius, in rotating, carries the hand with it ; thus, the palm of the hand is alternately turned forward and backward. When the palm is turned forward, or upward, the attitude is called supination ; when backward, or downward, pronation. (5) Condyloid joint. — When an oval-shaped head, or condyle, of a bone is received into an elliptical cavity, it is said to form a condyloid joint. An example of this kind of joint is found in the metacarp()-])halangeal articulations. The rounded heads of the metacarjial bones are rcrcjved in the elliptical-shaped bases of the phalanges. (6) Saddle joint. — In this joint the articular surface of each bone is concave in one direction, and convex in another, at right angles to the former. A man seated in a saddle is " articu- lated " with the saddle by such a joint. For the saddle is con- cave from before backwards, and convex from side to side, while the man presents to it the concavity of his legs astride, from side to side, and the convexity of his seat, from before back- wards. The metacarpal bone of the thumb is articulated with the trapezius of the carpus by a saddle joint. Both the condy- Chap. YI] ARTICULATIONS 87 loid and the saddle joints admit of motion in every direction except that of axial rotation. The different kinds of movement of which bones thus con- nected are capable are : — 1. Flexion. — A limb is flexed, when it is bent. 2. Extension. — A limb is extended, when it is straightened out. 3. Abduction. — This term generally means drawn away from the middle line of the body. 4. Adduction. — This term generally means brought to or nearer the middle line of the body. Both abduction and adduction have a different meaning when used with reference to the fingers and toes. In the hand the imaginary line is supposed to be drawn through the middle finger ; and in the foot through the second toe. 5. Rotation. — INIeans made to turn on its own axis. 6. Circumduction. — Means made to describe a conical space by rotation around an imaginary axis. No part of the body is capable of perfect rotation, as a wheel, for the simple reason that such motion w^ould necessarily tear asunder all the vessels, nerves, muscles, etc., which unite it with other parts. Sprain. — A wrenching or twisting of a joint accompanied by a stretching or tearing of the ligaments or tendons is called a sprain. Dislocation. — If in addition to a sprain, the bone is displaced, the injury is called a dislocation. SUMMARY Articulations or Joints — connections existing between bones. 1. Sutura. — Articulations by Synarthrosis, Bones are con- or nected by fi- Immovable brous tissue Joint or cartilage. pro- cesses and indentations interlocked together. A thin layer of fibrous tissue is interposed between the bones. Sutures may be dentated, dove-tailed ; serrated, saw-like ; squamous, scale-Uke ; harmonic, smooth; and grooved, for the re- ception of thin plates of bone. , Synchondrosis. — Temporary joint. Cartilage between bones ossifies in adult life. 88 ANATOMY FOR NURSES [Chap. VI Amphiarthrosis, or Slightly Movable Joint Bones are con- nected by ili.sks of car- tilage or in- terosseous ligaments. ' 1. Symphysis. — The bones are united bj' a plate or disk of fibro- cartilage of considerable thickness. Syndesmosis. — The bony surfaces are united by an interosseous liga- ment, as in the lower tibio-fibular articulation. Diarthrosis, or Movable Joint Movement . , Fibrous liga- ments form- ing a capsule. Synovial ni e m b r a n e lining fibrous capsule. Hyaline car- tilage cover- ing articular ends of bones. Flexion. Extension. Abduction. Adduction. Rotation. . Circumduction. 1. Arthrodia. — Gliding joint ; artic- ulates by i)lane surfaces which glide upon each other. 2. Ginglymus. — Hinge or angular joint ; moves backward and for- ward in one plane. 3. Enarthrosis. — Ball and socket joint ; articulates bj' a globular head in a cup-like cavity. 4. Trochoides. — Pivot joint ; articu- lates by a pivot process turning within a ring, or by a ring turning round a pivot. 5. Condylarthrosis. — Condyloid joint ; ovoid head received into elliptical cavity. 6. Reciprocal Reception. — Saddle joint ; articular surfaces are con- cavo-convex. CHAPTER VII MUSCULAR TISSUE: CLASSIFICATION; PROMINENT SKELETAL MUSCLES MUSCULAR TISSUE This is the tissue by means of which the movements of the body and its component parts are produced. It constitutes the fleshy parts, enters into the structure of many of the internal organs, and forms a large proportion of the weight of the whole body. The following has been calculated for a man of one hun- dred and fifty pounds' weight from the tables of Liebig : — • Skeleton 28 pounds. Blood 12 pounds. Viscera Skin 48 pounds. Fat J Muscles 62 pounds. Muscular tissue, like every other tissue, is composed of cells and intercellular substance, with this special difference that the cells become elongated and develop into fibres. The intercellular substance consists of a small amount of cement, which helps to hold the fibres together. The fibres are really bound into bundles by connective tissue which forms a supporting framework. CLASSIFICATION Muscle fibres are of three distinct kinds, and we therefore dis- tinguish three varieties of muscular tissue : — 1. Striated or cross-striped ; 2. Non-striated or plain ; 3. Cardiac. Striated or cross-striped muscular tissue. — This tissue is called striated because it is distinctly marked by striae, or parallel cross stripes. It is also called skeletal because it forms the muscles 89 90 ANATOMY FOR NURSES [Chap. VII Fig. 65. — Dia- GRA.M OF Muscle Fibre with Sar- coLEM.MA At- tached. which are attached to the skeleton, and voluntary because it is nearly always under the control of the will. It is composed of long, slender fibres measuring on an average gj^ inch (0.050 mm.) in diameter, but having a length of an inch or more. Each fibre consists of three distinct elements : — (1) Contractile substance, forming the centre and making up most of the bulk of the fibres ; (2) Nuclei, which lie scattered upon the surface of the contractile substance ; (3) The sarcolemma, a thin, structureless tube which tightly encloses the contractile substance and the nuclei. As each fibre is developed from a single cell and contains a number of nuclei, we may regard it as a multinuclear cell of elongated form. The muscle fibres lie closely packed, their ends lapping over on to adjacent fibres and forming bundles. A delicate connective tissue penetrates between the fibres, surrounds the small bundles and groups them into larger bundles. Connective tissue also surrounds the larger bundles and forms a covering for the whole muscle. Thus it will be seen that connective tissue forms a sup- porting framework for muscular tissue. All of the muscles described in this chapter are striated or skeletal. Non-striated or plain muscular tissue. — This tissue is called plain or non-striated because it does not exhibit parallel transverse strice or stripes. It is also called visceral because it constitutes a large portion of the substance of many of the viscera, and involuntary because it is usually withdrawn from the control of the will. It is composed of elongated fibre-cells containing a single elongated nucleus. These fibre-cells are always shorter than the fibres of striated tissue. They lie side by side or lay over one another at the ends and are joined together by a small amount of cement Fig. 66. — Fibre- cells OF Plain Muscular Tissue. (Highly magnified.) Chap. VII] MUSCULAR TISSUE 91 substance. The fibre-cells are variously grouped in different parts of the body ; sometimes crowded together in solid bundles which are arranged in layers and surrounded by connective tis- sue, as in the intestines ; sometimes arranged in narrow, inter- lacing bundles, as in the bladder ; sometimes wound in single or double layers around the blood-vessels ; and again running in various directions and associated with bands of connective tissue, they form large, compact masses, as in the uterus. Cardiac muscular tissue. — This variety of muscular tissue is found only in the heart substance. It is involuntary, but is striated, though not as distinctly as skeletal muscle. It is made up of fibres which are short, contain just one nucleus, and no sarcolemma. The fibres are grouped in bundles which are nearly square, and fine fibrils from each cell help to hold the bundles together. The bundles are really held together by connective tissue, which forms a supporting framework in the heart, just as it does in skeletal and visceral muscle. Stimuli. — This term is used to describe influences which stimu- late muscle fibres. They may be chemical, mechanical, thermal, electrical, or nervous. From the standpoint of physiology the nervous impulse is the most important. Characteristics. — Muscular tissue is highly specialized and exhibits irritability, contractility, extensibility, elasticity, and tonicity. Irritability has been defined as the response of a tissue to a stimulus. Nervous tissue and certain epithelial cells as well as muscular tissue possess this property. The response of any tissue to stimulation is to perform its special function, and in the case of muscular tissue this response takes the form of contraction and is known as muscular contractility. Each individual fibre becomes shorter and thicker, and thus the whole muscle becomes shorter and thicker. The function of the connective tissue frame- work is passive and may be likened to that of a harness, through which all the numerous contractile fibres are enabled to unite their efforts. Contraction of the muscle tends to bring together its two ends with whatever may be attached to them. Thus the contraction of certain muscles of the arm will shorten the muscles, shorten the distance between their ends, and flex the forearm. 92 ANATOMY FOR NURSES [Chap. \II Exiensibility of a li\'ing muscle means that it can be stretchetl or extended, and elasticity means that it readily returns to its orig- inal form. Normally, the skeletal muscles are in a condition of slight tension, being stretched from bone to bone. This condition is of importance in two ways : (1) smoothness of movement is dependent upon it ; (2) a stretched muscle will contract more cjuickly than one that is relaxed. To understand the first state- ment it is important to remember that skeletal muscles are usually arranged in antagonistic groups, one of which opposes another. Thus the muscles located on the anterior surface of the arm and forearm are called flexors, and those located on the posterior sur- face are called extensors. The action of the flexors is to bend the arm, the action of the extensors is to extend or straighten the arm. When stimulated, either group of muscles must overcome the resist- ance of the opposing group. Therefore contraction takes place more slowly and evenly, and smoothness of movement is the result. Under normal conditions there is a constant and insensible tendency to contract called tonicity. It is really a mild, sustained contraction, and though it may vary in degree, it is rarely absent altogether. Tone in the skeletal muscles gives them a certain firmness and maintains a .slight steady pull upon their attach- ments. It is not likely to result in movement on account of the action of an antagonistic muscle. In fractures the over-riding of the broken ends of a bone is often due to the contraction of the muscle, that is the result of its tonicity. This property is of importance in several ways: (1) in connection with elasticity it promotes a quicker response to stimulation, (2) it assists in maintaining the circulation of the blood and hinph, and (3) it assists in the regulation of nutrition and body heat. As previously staled tonicity may vary in degree. Increase in the degree may follow (1) muscular exercise, (2) mental exercise, and (3) lower- ing of the surrounding temperature. The effect of a cold bath is a familiar example of the last. Blood-vessels and nerves. — All varieties of muscular tissue are well supplied with blood-vessels and nerves. The blood- vessels that supply blood to the muscles are supported and carried by the connective tissue. They do not penetrate into the cells, but each cell is bathed in lymph which exudes from the blood- vessels. The cells take from the lymph the materials they need Chap. VII] MUSCULAR TISSUE 93 and give up to the lymph the waste substances that are the result of their activities. In order to understand the nerve supply it is necessary to become familiar with a few facts regarding the nervous system. The name nervous system includes all the structures in the body that are made of nerve tissue. For purposes of study the nervous system is arbitrarily divided into the central ner- vous system, and the sympathetic system. The central nervous system consists of the brain, the spinal cord, and their nerves. The sympathetic system consists of masses of nerve cell-bodies called ganglia, and the nerves connected with "them. These two systems differ slightly in function, but are intimately con- nected and are really interdependent. Most of the nerves that are connected with the skeletal muscles belong to the central nervous system, but the majority of those supplying the visceral muscles belong to the sympathetic system. Nerves that carry impulses from the periphery (in this connection the muscles) to the brain, spinal cord or ganglia, are called afferent. Nerves that carry impulses to the periphery from the brain, spinal cord or gang- lia, are called efferent. Afferent nerves that are connected with muscle fibres are spoken of as sensory. Efferent nerves that end in muscle fibres are spoken of as motor. For the purposes of this chapter, each of the terms in these pairs, i.e. motor and efferent, sensory and afferent, may be considered interchangeable. It should be remembered, however, that the terms efferent and afferent are applied to other types of nerves besides motor and sensory nerves.^ Differences in, and results of, contraction. — Skeletal muscle is essentially a quick-acting tissue. It contracts quickly and re- laxes promptly. Even prolonged contractions are compounded of successive twitches that follow each other too rapidly to permit of relaxation. In sharp contrast to this the contractions of vis- ceral muscle develop slowly, are maintained for some time, and fade out slowly. In addition to the contractions that are the result of stimulation from the nerves, visceral and cardiac tissue are also automatic. This means that there is a tendency to rhyth- mic contraction and relaxation inherent in the tissue itself. Contractions of all kinds of muscular tissue cause a chemical change in the substance of the muscle fibre. The complex sub- ' For a more detailed description, see Chap. XIX. 94 ANATOMY FOR NURSES [Chap. VII stances of which it is composed are split and oxidized into simpler substances, i.e. water, carbon dioxide, and sarcolactic acid. At the same time heat is generated, energy is set free, and various waste products are formed. Heat is a familiar result of muscular exercise. The liberation of energy enables the muscle to do its required work. The waste compounds must be eliminated, and, except in cases of prolonged contractions, the system is able to get rid of thep readily. Prolonged contractions result in fatigue, and this means two things : (1) an accumulation of waste substances, known as fatigue poisons, (2) a loss of nutrient material. A period of rest furnishes opportunity for these poisons to be carried to the excretory organs by the blood, and fresh nutritive materials from the digestive organs carried by the blood to the muscle. In cases of extreme fatigue that are the result of prolonged overwork of a muscle or muscles, the fatigue poisons have the same effect that the toxins of tetanus have, and the over-contracted condition is spoken of as tetanus of the muscle. Writer's cramp with its ac- companying stiffness and pain is an example of this condition. In such cases massage improves the circulation of the blood and IjTiiph, thus helping the elimination of fatigue poisons, and brings about a condition of relaxation. Skeletal Muscles. — The muscles are separate organs, each muscle having its own sheath of connective tissue, called epimy- sium. They vary in size from a fraction of an inch to nearly twenty- four inches (600 mm.) and are very diverse in form. In the trunk the muscles are broad, flattened, and expanded, forming the walls of the cavities which they enclose. In the limbs they are of con- siderable length, forming more or less elongated straps. A typical muscle is described as consisting of a body and two ex- tremities. The body is the red contracting part, and the extremi- ties arc the ends where they are attached. Attachment of the muscles to the skeleton. — Muscles are at- tached to the bones, cartilages, ligaments, and skin in various ways, the most common mode of attachment being by means of tendons. The muscular fibres converge as they approach their tendinous extremities, and gradually blend with the fibres of the tendons, the tendons in their turn inserting their fibres into the bones. Where one muscle connects with another, each muscle ends in expanded form in a flat, fibrous membrane called aponeurosis. Chap. VII] MUSCULAR TISSUE 95 Again, in some cases, the muscles are connected with the bones, cartilages, and skin, without the intervention of tendons or aponeuroses. Origin and insertion. — It is customary to speak of the attach- ments of the opposite ends of muscles under the names of origin and insertion, the first term origin being usually applied to the more fixed attachment ; the second term insertion being applied to the more movable attachment. The origin is, however, abso- lutely fixed in only a very small number of muscles, such as those of the face, which are attached by one end to the bone, and by the other to the movable skin. In the greater number, the muscle can act from either end. Names of muscles. — The skeletal muscles are usually called by their Latin names, and it is helpful to understand the meaning of these names, as they are often descriptive of some distinctive characteristic, such as their form, size, attachment, location, function, etc.^ The majority occur in pairs. Only a few are single, and they are located about the median line. Muscles may be classified in sev- eral ways. The most helpful way is to classify them according to their location and function. It is not necessary for nurses to dis- tinguish more than a few of the most prominent. CHIEF MUSCLES OF HEAD, FACE, TONGUE, AND NECK Muscles of the Head — Occipito-frontalis. Muscles of the Face Muscles of the Tongue Muscles of the Neck Orbital Muscles Muscles of Mastication Muscles of Expression I Genioglossus. I Styloglossus. f Platysma. I Sterno-cleido-mastoid. Four recti. Two oblique. Levator palpebrse su- perioris. Masseter. Temporal. Internal pter3'goid. External pterj^goid. r Orbicularis oris. I Buccinator. 1 The student will find the Latin derivations and their meaning in the Glossary at the back of the book. 96 ANATOMY FOR NURSES [Chap. VII Occipito-frontalis. — The chief muscle of the liead is the occi- pito-frontaHs, which may be considered as two muscles united to- gether by a tliiii aponeurosis extending over and covering the whole Fig. 67. — Superficial Muscles of Head and Neck. (Gerrish.) of the upper part of the cranium. The occipital takes its origin from the occipital bone and is inserted into the aponeurosis. The frontal takes its origin from the tissues in the region of the eye- brows, and is also inserted into the aponeurosis. Adioti. — The frontal portion of this muscle is the more po^er- Chap. VII] MUSCULAR TISSUE 97 Fig. 68. — Muscles of Right Eyeball within THE Orbit. Seen from the front. 21, superior rectus ; 22, inferior rectus ; 23, external rectus ; 24, internal rectus ; 25, su- perior oblique ; 26, inferior oblique. ful ; by its contraction the eyebrows are elevated, the skin of the forehead thrown into transverse wrinkles, and the scalp drawn forward. The occipital acts in direct line with the frontal, and emphasizes its action. Muscles of the face. — There are about thirty facial muscles ; they are chiefly small, and only a few are considered. We group them as : (1) Orbital muscles, (2) jNIuscles of mastication, and (3) Muscles of expression. Orbital muscles. — The orbit contains seven muscles; six of them are attached to the eyeball, and the seventh is attached to the upper lid. The six muscles attached to the eyeball are arranged in three oppos- ing pairs. The superior and inferior recti. — These two muscles have their origin at the apex of the orbital cavity and pass straight forward to their insertion into the eyeball, the superior rectus in the middle line above, and the inferior rectus opposite it below. Action. — Contraction of the superior rectus rolls the eye upward ; contraction of the inferior rolls the eye downward. The internal and external recti. — These two muscles have their origin at the apex of the orbital cavity, and pass forward to their insertion into the eyeball, the internal on the inner side, the external on the outer side. Action. — Contraction of the internal rectus draws the eye inward toward the nose. Con- traction of the external rectus draws the eye outward. Superior oblique. — The su- perior oblique muscle arises from the apex of the orbit (the same as the four recti), courses forward to the upper and inner angle of the orbit, w^here it passes through a loop of cartilage. Then it bends at an acute angle, passes around the upper part Fig. 69. — Muscles of Eyeball. Seen from side. 19, elevator muscle of eyelid ; 22-26, same as in Fig. 68. 98 ANATOMY FOR NURSES [ClL\P. VII of the eyeball, and is inserted between the superior and external recti. Inferior oblique. — The inferior oblique arises from the orbital Fig. 70. — Tempor.vl .\nd Deep Muscles about the Mouth. (Gerrish.) plate of the maxilla, and courses around the under portion of the eyeball to its attachment near the external rectus. Action. — The action of the two oblique muscles is somewhat complicated, but their general tendency is to roll the eyeball on its axis. Chap. VII] MUSCULAR TISSUE 99 In most cases the movements of the eye are somewhat complex and more than one muscle is involved. Levator palpebrae superioris (lifter of the upper lid). — It arises from the sphenoid bone, passes forward, and is inserted into the tarsal cartilage of the upper lid. Action. — It elevates the upper lid and opens the eye. Fig. 71. — Pterygoid Muscles. Viewed from behind, the back portion of the skull having been removed. (Gerrish.) Muscles of mastication. — They are: (1) the masseter (chew- ing muscle), (2) the temporal (temple muscle), (3) the internal pterygoid, and (4) the external pterygoid. These muscles can be located on the illustrations. They have their origin in one or more of the immovable bones of the skull, and are inserted into the movable lower jaw. Action. — The muscles of mastication generally act in con- cert, bringing the lower teeth forcibly into contact with the 100 ANATOMY FOR NURSES [Chap. VII upper ; they also move the lower jaw forward upon the upper, and in every direction necessary to the process of grinding the food. Muscles of expression. — These muscles are sometimes called mind muscles from the indications that they afford of the mental state of the individual. They are closely connected with the under surface of the skin or with each other, and therefore their slightest contraction is shown on the face. They include the muscles of the forehead, eyelids, nose, and all those related to STYLOID PROCESS ORIGIN OF BTYLOMVOID -MANOIBLC Fig. 72. — Muscles of the Tongue. Viewed from the right side. (Gerrish.) the orifice of the mouth. We shall only consider two important muscles related to the orifice of the mouth. Orbicularis oris. — The ring muscle surrounds the opening of the mouth, extending from the nose above to the chin below. It forms a great part of the bulk of the lips, and constitutes a sphincter to the mouth. It is attached above to the partition between the nostrils and the upper jaw bones, and below to the mandible. Action. — It closes the mouth. Buccinator (trumpeter's muscle). — This muscle arises from the alveolar processes of the maxilla and mandible. Its different parts Chap. VII] MUSCULAR TISSUE 101 converge to the angle of the mouth, and are inserted into the orbicularis oris. Action. — It compresses the cheeks, helps to close the mouth, and assists in such motions as blowing a trumpet. Chief muscles of the tongue. — The chief muscles connecting the tongue and hyoid bone to the lower jaw are the genioglossus and the styloglossus, Genioglossus. — The genioglossus has its origin in the front part of the mandible, and is inserted in the whole length of the tongue in and at the side of the mid line. Actioii. — ■ It thrusts the tongue forward, retracts it, and also depresses it. Styloglossus. — The styloglossus has its origin in the styloid process ^ of the temporal bone, and is inserted in the whole length of the side and under part of the tongue. Action. — It draws the tongue backward. These muscles are interesting to us from the fact that during general anaesthesia they, together with the other muscles, become relaxed, and it is necessary to press the angle of the lower jaw upward and forward in order to prevent the tongue from falling backward and obstructing the larynx. Muscles of the neck. — The two superficial muscles of the neck are: (1) platysma, (2) sterno-cleido-mastoid. Platysma (broad sheet muscle) . — It arises from the skin and areolar tissue covering the pectoral, deltoid, and trapezius muscles, and is inserted in the mandible and muscles about the angle of the mouth. Action. — It draws the angle of the mouth down and contracts the skin of the neck. Sterno-cleido-mastoid. — The most prominent muscle of the neck is the sterno-cleido-mastoid. It is named from its origin and insertion, arising from part of the sternum and clavicle, and being inserted into the mastoid portion of the temporal bone. This muscle is easily recognized in thin persons by its forming a cord-like prominence obliquely situated along each side of the neck. Action. — Both sterno-cleido-mastoid muscles acting together flex the head on the chest or neck. They serve as convenient landmarks in locating the great vessels carrying the blood to and 1 See Fig. 27. 102 ANATOIVIY FOR NURSES [Chap. VII from the liead. If one of these muscles be either abnormally con- tracted or paralyzed, we get the deformity called Torticollis or wrv neck. CHIEF MUSCLES OF THE TRUNK They may be arranjjjed in four groups : — _ . [ Trapezius. 1. Muscles of the Back ' 2. Muscles of the Chest 3. Muscles of the Thorax 4. Muscles of the Abdomen Latissimus dorsi. I Pcctoralis major. I Pectoralis minor. I External intcrcostals. Internal intcrcostals. Levatores costarum. External oblique. Internal oblique. Rectus abdominis. Transvcrsalis. OCCIPITAL BONE Muscles of the back. — The muscles of the back are disposed in five layers, one beneath another. The two largest and most su- perficial muscles are: (1) the trapezius, (2) the latissimus dorsi. Trapezius. — The trapezius, so called because right and left together make a large dia- mond-shaped sheet, arises from the middle of the occipital bone, from all the cervical and all the thoracic vertebrae. The connection with the cervical \'ertebr^\' '^fK \ a! \ y Fig. 77. — Di.\phrag.m. Viewed from in front. (Gerrish.) is deeply concave, and covers the liver, stomach, pancreas, spleen, and kidneys. Action. — The diaphragm is probably the most important voluntary muscle in the body, as well as the chief respiratory and expulsive muscle. In the act of inspiration the diaphragm contracts, and in contracting flattens out and descends, the ab- dominal viscera are pressed downwards, and the thorax is ex- panded vertically. In forcible acts of expiration, and in efforts of expulsion from the thoracic and abdominal cavities, the diaphragm and all the other muscles which tend to depress the ribs, and those which compress the abdominal cavity, concur in powerful action to empty the lungs, to fix the trunk, and to expel the contents of Chap. VII] MUSCULAR TISSUE 107 the abdominal viscera. Thus it follows that the action of the diaphragm is of assistance in expelling the foetus from the uterus, the fseces from the rectum, the urine from the bladder, and its contents from the stomach in vomiting. Muscles of the abdomen. — The chief muscles of the abdomen are : (1) external oblique, (2) internal oblique, (3) rectus abdominis, and (4) trans- versalis. External oblique. — The strongest and most superficial of the abdominal muscles is the external oblique. It arises from the outer surface of the eight lower ribs. The fibres incline downward and forward and terminate in the broad aponeurosis, which, meet- ing its fellow of the opposite side in the linea alba, covers the whole of the front of the abdomen. The lowest fibres of the aponeurosis are gathered together in the shape of a thickened band, which extends from the anterior superior spi- nous process of the ilium to the pubic bone, and forms the well-known and important landmark, the inguinal liga- ment, more commonly known as Pou- part's ligament from the anatomist who first described it. Internal oblique. — The internal oblique muscle lies just beneath the external oblique. It arises from the inguinal ligament, the outer crest of the ilium, and slightly from the lumbar fascia.^ ' The lumbar fascia springs from the vertebral column in three layers : — (1) Outer, or posterior. (2) Middle. (3) Inner, or anterior. (1) The outer layer begins at the spinous process of the lumbar and sacral vertebrae. It is attached above to the last rib, and below to the outer tip of the iliac crest and the ilio-lumbar ligament. (2) The middle layer starts from the transverse processes of the lumbar vertebrse (3) The inner layer starts from the front of the bases of the same processes. The fascia resulting from the combination of these three layers gives rise to the internal oblique and transversalis muscles. Fig. 7S. — Rectus Abdomi- nis AXD Obliquds Internus OF Right Side. (Gerrish.) 108 ANATOMY FOR NURSES [Chap. VII Its most posterior fibres run upward and forward and are inserted in the costal cartilages of the four lower ribs. At the outer border of the rectus muscle the remaining muscle fibres expand into a ijroad aponeurosis. This aponeurosis divides into two layers, one passing before, the other behind, the rectus muscle; they reunite at its inner border in the linea alba, and thus form a sheath for the rectus, extending from the xiphoid process to the crest of the pubes. At the lower part of the rectus the posterior layer of the aponeurosis is deficient. Rectus abdominis. — The rectus is a long, flat muscle, consisting of vertical fii)res situated at the fore part of the abdomen, and enclosed in the fibrous sheath formed by the aponeurosis of the internal ob- lique. It arises from the pubic bone, and is inserted into the cartilages of the fifth, sixth, and seventh ribs ; it is separated from the muscle of the other side by a narrow interval which is occupied by the linea alba. Transversalis. — The transversalis muscle lies beneath the internal oblique. The fibres arise from the six lower costal cartilages, the lumbar fascia, the crest of the ilium, and the outer third of the inguinal ligament. The greater part of its fibres have a horizontal direction, and are inserted in the linea alba and the crest of the pubes. Linea alba. — The linea alba, or white line, is a tendinous band formed by the union of the aponeuroses of the two oblique and transverse muscles, the tendinous fibres crossing one another from side to side. It extends perpen- dicularly, in the middle line, from the xiphoid portion of the sternum to the pubes. It is a little broader above than below, and a little be- low the middle it is widened into a flat, circular space, in the centre of which is situated the umbilicus. Fig. 79. — Transversalis Abdominis of Right Side. (Gerrish.) Chap. VII] MUSCULAR TISSUE 109 Action of the abdominal muscles. — When these muscles con- tract, they compress the abdominal viscera, and constrict the cavity of the abdomen, in which action they are much assisted by the descent of the diaphragm. By these means they give assist- ance in parturition, defecation, micturition, and vomiting. They also assist in respiration, and in various movements, such as climbing, flexing the thorax upon the pelvis, rotation of the trunk, etc. The inguinal canal. — Between the abdominal muscles, parallel to, and about one-half inch above the inguinal ligament, is a tiny canal, about one and one-half inches long, called the inguinal canal. The internal opening of the canal is called the internal abdominal ring, and is situated in the fascia of the transversalis muscle, mid- way between the spine of the ilium and the crest of the pubic bone. The canal ends in the external abdominal ring, which is in the tendon of the external oblique muscle. This canal transmits the sper- matic cord in the male, or the round ligament of the uterus in the female. Weak places in the abdominal walls. — The internal and ex- ternal abdominal rings, described above, the umbilicus, and an- other ring situated just below the inguinal ligament, and called the femoral ring, are considered weak places because they are so often the seat of hernia. Hernia, ^ or rupture, is a protrusion of a portion of the contents of a body cavity, and in this instance would mean a protrusion of a portion of the intestine or mesentery through one of these weak places. If it occurs in the umbilicus, it is called umbilical hernia; in the inguinal rings, inguinal hernia; and in the femoral ring, femoral hernia. The inguinal canal is larger in the male than in the female, hence inguinal hernia is more common in the male than in the female. MUSCLES OF THE UPPER EXTREMITIES A certain number of muscles situated superficially on the trunk are frequently grouped with the muscles of the upper extremities, as their function is to attach the upper limbs to the trunk and move the shoulders and arms. Of these, the two superficial • If the skull is injured so that a portion of the brain protrudes, it would also be correctly spoken of as hernia of the brain. Of course this is more unusual than abdominal hernia. 110 ANATOMY FOR NURSES [Chap. VII muscles we have mentioned as covering the back, the trapezius and latissimus dorsi, and the pectoral muscles covering the front of the chest, are the chief. The muscles of the extremities are arranged in antagonistic groups, the action of one group opposing the action of the other. The movements of which the extremities are capable are flexion and extension, abduction and adduction, supination and prona- tion, circumduction and rotation. (See page 87.) Functionally we might group the muscles of the upper extremi- ties as follows. Name of Muscle Location Function Trapezius Upper portion of back Moves shoulder upward and backward. Pectoralis minor Chest, under pectoralis Moves shoulder Moving the major downward Shoulder and assists in the elevation of the ribs during in- spiration. [ Deltoid Covers the top of the Abduction. Moving the Arm Pectoralis major shoulder Chest, from sternum to Adduction. humerus Latissimus dorsi Lower portion of back Adduction. Biceps Anterior surface of arm Flexion. Triceps Posterior surface of arm Extension. Moving the Pronators Anterior surface of Pronation. Forearm forearm Supinators Posterior surface of forearm Supination. Deltoid. — The deltoid is a coarse, triangular muscle covering the top of the shoulder. It arises from the clavicle, acromion process, and spine of the scapula, extends downw^ard, and is inserted into the middle of the shaft of the humerus, on the outer side. (See Fig. 81.) Action. — It abducts — raises the arm from the side so as to bring it at right angles to the trunk. This action is opposed Chap. VII] MUSCULAR TISSUE 111 by the pectoralis major and latissimus dorsi, which have been described. Biceps. — The biceps is a long fusiform muscle, occupying the whole of the anterior surface of the arm ; it is divided above into two portions or heads, from which circumstance it has re- FiG. 80. — Muscles of the Front op the Right Shoulder AND Arm. (Gerrish.) Fig. 81. — Muscles on the Dorsum of the Right Shoulder and Arm. CGerrish.) ceived its name. It arises by these two heads from the scapula, and is inserted into the radius. Action. — It flexes the forearm on the arm. Triceps. — The triceps is situated on the back of the arm, extending the whole length of the posterior surface of the humerus. It is of large size, and divided above into three heads ; hence its name. Two of the heads have their origin in the scapula and one in the humerus. The three heads unite in a common tendon which is inserted into the ulna. 112 ANATOMY FOR NURSES [C HAl'. VII Action. — It is the great exten- sor musele of the forearm, and is tlie direct antagonist of the l)ieeps. Muscles of the forearm. — The muscles covering the forearm are disposed in groups, the pronators and flexors being placed on the front and inner part of the fore- arm, and the supinators and ex- tensors on the outer side and back of the forearm : they antagonize one another. The pronators turn the palm of the hand backward and, when the elbow is flexed, downward or prone. The supi- nators turn the palm of the hand forward, and, when the elbow is flexed, upward or into the supine position. The flexors and exten- sors have long tendons, some of which are inserted into the bones of the wrist, and some into the bones of the fingers : they serve to flex and extend the wrist and fingers. MUSCLES OF THE LOWER EXTREMITIES If we compare the muscles of the shoulder, arm, and forearm with those of the hip, thigh, and leg, we shall see that the anterior muscles of the former correspond roughly with the posterior muscles of the latter, the muscles of the Fig. 82. — Muscles in hip, thigh, and leg, however, be- of?h?rTght i"g larger and coarser in texture Forearm AND than those of the shoulder, arm, Hand. (Ger- rish.) and forearm. Chap. VII] MUSCULAR TISSUE 113 Functionally we might group the most important muscles of the lower extremities as follows : — Name of Muscle Moving the ^ Thigh Moving the Leg Moving the Foot Psoas magnus Iliacus Gluteus maximus Gluteus medius Gluteus minimus Adductor magnus Adductor longus Adductor brevis Adductor gracilis Sartorius Biceps Semitendinosus Semimembranosus Rectus femoris Vastus externus Vastus internus Vastus intermedius Tibialis anterior Peroneus tertius Tibialis posterior Gastrocnemius Soleus Peroneus longus ■ Peroneus brevis Location I In the pelvis and I upper part of thigh Region of buttocks Under gluteus maxi- mus Under gluteus medius •i Mesial part of thigh Mesial part of thigh Function Front of thigh § Back of thigh ■^ Front of thigh & Front of leg \ Back of leg Outer part of leg Flexion and out- ward rotation Extension, out- ward rotation and adduc- tion. Abduction and inward rota- tion. Addud, rotate and flex thigh. Adducts thigh and flexes the leg. Flexes leg, helps in rotation and abduc- tion of thigh. Flexors of knee, rotate leg in- ward, extend thigh. Extension of leg, flexes the thigh. Flexors. Extensors. Psoas magnus. — The great loin muscle arises from the last thoracic and all the lumbar vertebrae with the included inter- 114 ANATOMY FOR NURSES [Chap. VII vertebral cartilages. It extends down and forward, then down and backward, to its insertion in the small trochanter of the femur. Iliacus. — This mnsele and its relation to the psoas magnus is well shown in Fig. 83. It arises from the iliac fossa and is inserted Fig. 83. — P.so.\s, Iliacus, and Obturator Externus Muscles. (Gerri.sh.) partly into the tendon of the psoas and partly into the small trochanter of the femur. Action. — The psoas magnus and iliacus act as one muscle to flex the thigh on the pelvis, and rotate the femur outward. Glutei muscles. — The three gluteal muscles are coarse in tex- ture, and form the chief prominence of the buttocks. Chap. VII] MUSCULAR TISSUE 115 Gluteus maximus arises from the ilium, sacrum, and coccyx, and is inserted into the great trochanter of the femur. Action. — It is a powerful extensor of the hip-joint. It also rotates the femur outward, and adducts the thigh. Gluteus medius and gluteus minimus are under the gluteus maximus and almost entirely covered by it. They arise from the outer surface of the ilium and are inserted into the great trochanter. Action. — Abduction of the thigh, and when the thigh is flexed, inward rotation. Adductors. — The four adductor muscles are called respectively magnus (great), longus (long), brevis (short), and gracilis (slender). They are situated on the inner side of the thigh. They arise from different portions of the pubic bone, and the first three are inserted into the inner side of the femur. The gracilis is inserted into the shaft of the tibia. Action. — The magnus, lon- gus, and brevis adduct, rotate, and flex the thigh. The gra- cilis adducts the thigh and flexes the leg. Sartorius. — The sartorius, or tailor's muscle, is a long, rib- bon-like muscle situated on the front of the thigh. It crosses the thigh obliquely from its origin in the ilium to its insertion in the tibia. It was formerly supposed to be the muscle principally concerned in producing the posture assumed by the tailor in sitting cross-legged, hence its name. Action. — It flexes the leg, and helps in rotation and abduction of the thigh. Biceps. — The biceps arises by two heads, one from the ischium, and the other from the posterior surface of the femur. It is in- serted into the head of the fibula and the outer tubercle of the tibia. Semitendinosus and Semimembranosus. — They arise from the ischium, and are inserted into the upper and inner part Fig. 84. Gluteus Maximus of Right Side. (Gerrish.) 116 ANATOMY FOR NURSES [Chap. VII of the tibia. These three muscles, the biceps, semitendino- sus, and semimembranosus, cover the back of the thigh, hence are named jiostrrior femoral, or hamstring muscles. Fig. 85. — Mcscles in thb Dorsum of the Right Thigh. (Gerrish.) Fig. 86. — Supekficial Muscles IN Front Part of the Right Thigh. (Gerrish.) Action. — They flex the knee, rotate the leg inward, and extend the thif^'h. Quadriceps. — The quadriceps is a four-headed muscle that covers the front of the thigh, and is analogous to the triceps cover- Chap. VII] MUSCULAR TISSUE Fig. 87. — Vastus Intermedius OP Right Side. (Gerrish.) ing the back of the arm. Each head is described as a separate muscle : (1) rectus femoris, (2) vastus externus, (3) vastus internus, (4) vastus inter- medius. The rectus femoris arises from the ilium, the other three arise from the femur. They pass downward, and are inserted by one tendon to the tubercle of the tibia. The tendon passes in front of the knee-joint, and the patella is a sesamoid bone devel- oped in it. Action. — The quadriceps is the great extensor of the leg; it also flexes the thigh, and antagonizes the action of the hamstring muscles. U< Fig. 88. — Gastrocnemius of Right Side. (Gerrish.) 118 ANATOMY FOR NURSES [Chap. VII Gastrocnemius and soleus. — The gastrocnemius and soleus form the calf of the leg. The gastrocnemius arises by two heads from the two condyles of the femur. The soleus is in front of the gastrocnemius. It arises from the tibia and fibula. The direction of both is downward, and they are inserted into a common tendon, the tendon of the heel (tendo Achillis), which is the thickest and strongest tendon in the body, and is inserted into the calcaneum, or heel bone. Action. — Extension of the foot, and when the ankle joint is fixed, extension of the leg. These muscles possess considerable power, and are constantly called into use in standing, walking, dancing, and leaping ; hence the large size they usually present.^ Fasciae. — As previously stated (page 37) most of the muscles are closely covered by sheets of fibrous tissue called fascife. These fasciae not only envelop and bind down the muscles, but also sep- arate them into groups. Such groups are named according to the parts of the body where they are found, viz. : cervical fascia, thoracic fascia, abdominal fascia, pelvic fascia, etc. In- dividual fascia are frequently given the name of the muscle which they envelop and bind down, viz. : temporal fascia, pectoral fascia, deltoid fascia, etc. It is important for the student to realize the continuity of the fibrous membranes. Tendons, liga- ments, and fasciae blend with periosteum, tendons and fasciae serve as ligaments, tendons lose themselves in fasciae, and tendons of some muscles serve as fasciae for others. Annular ligaments. — In the vicinity of the wrist and ankle, parts of the deep fascia become blended into tight transverse bands, which serve to hold the tendons close to the bones. These bands are called annular ligaments. (See Fig. 82.) ' Additional muscles included in Summary. Chap. VII] SUMMARY 119 Muscular Tissue 1 SUMMARY r Cells develop into fibres. ' Intercellular substance at a minimum. Connective tissue — supporting framework. Classification Striated / Voluntary \ Skeletal Non- f Involuntary striated I Visceral tern. 10 11 1. Marked with transverse strise. 2. Under control of wiU. 3. Attached to bones. 4. Composed of bundles of fibres. 5. Fibres are multinuclear elon- gated cells. 6. Connective tissue framework. 7. Outer sheath of connective tissue — Epimysium. 8. Well supplied with f Sensory. nerves. I Motor. 9. Majority of nerves connect with central nervous sys- f Brain. I Spinal cord. Well supplied \vith blood- vessels and lymphatics. Contracts quickly, relaxes promptly. 1. Not marked with transverse striae. 2. Not under control of will. 3. Found in walls of blood- vessels and viscera. 4. Composed of bundles of fibre- cells. 5. Fibre-cells contain just one nucleus. 6. Connective tissue framework. 7. Outer sheath of connective tissue — Epimysium. 8. Well supphcd with i Sensory. nerves. I Motor. 9. Majority of nerves connect with sympathetic nervous system. 10. Well supplied with blood- vessels and lymphatics. 11. Contracts slowly and continu- ously for long periods of time. 12. Possesses inherent power of automatic contraction. 120 ANATOMY FOR NURSES [Chap. VII Classification < r Striated Cardiac < Involuntary I Visceral y^ Stimxili Characteristics Contraction Fatigue Skeletal Muscles 1. Striated but not distinctly. 2. Not under control of will. 3. Made of square bundles of fibres. 4. Fibres are elongated cells, contain just one nucleus, no sarcolenuna. 5. Fine fibrils from cells form a network. 6. Connective tissue framework. 7. Contracts and relaxes quickly and unceasingly during life. Term used to describe influences which irritate or stimu- late. 1. Chemical. 2. Mechanical. Varieties \ 3. Thermal. 4. Electrical. 5. Nervous — important one. 1. Irritabihty — response to a stiumlus. 2. Contractility — muscle becomes shorter and thicker. 3. Extensibility — muscle can be stretched. 4. Elasticity — muscle readily returns to original shape. 5. Tonicity — mild, sustained contraction. „, . , ^, / Fibres shorten. Physical Change ( pi^res thicken. ' Take up oxj'gen. r Carbon dioxide. Formation of I Sarcolactic acid. i Various otherwastes. Heat is liberated. , Energy is set free. Accumulation of waste poisons. Loss of nutritive material. / Origin — more fixed attachment. 1 Insertion — more movable attachment. Chemical Change " Chap. VII] SUMMARY 121 ta 03 o ^-^ W 03 o -3 03 o I — I -Lj ^-r T3 d 03 >, =3 d S3 -^3 Q °^-i "T^ • c3 p^ p^ p^ 3 o3'm'3 o -3 P a; P^ ! fe d > C o ! O ^ ■^^ d vi c3 O d O o3 tH ^ > . 3 O tU C3 •— a d t» ^ »2 03 Q^ C P d 2 c > S O O O g a ^ ^ o3 , o3 , oj d ^ d ^ .g O) 0 d;=l d dj :3 oj :r3 d ^ d 3 o M oi> <1 <1 -^ OJ -73 OJ c 03 c3 O c3 O >> 2^ • :- !-, c "^ ^ S..2 I.2I P k:; S CL> O 03 d iu CD X ^ CU o-t3 -^ d I 03 - ^^-^ o .s r-H O.rt—H !_ curd 03 -ri -fJ 03 ~^ diTTi -?, Sg-^'^pad rTJ d cs ^3 d o3 d o3 -^2 d c3 d o a "^ "S "S 000 O H o X a <1 a <1 o O X a <1 o3 a n> 44 a is «! ^ T3 S !^ .^ j3 -*j 0 0 S2 0 e S-, fc..2 a ifi I— I t— I W d ^ X! o* (U cr a 0 0 o3 a t4 0 0 0 OI o3 a > 3 d ^ m 1— ( ^ S S •— ! 'TS H HH W OS 0 C 0 "3 o c3 CO T3 +3 fr^ O o ^ o J5 o ^ =: < CD 5, o^. js « u;:;— ^ o -7- O _0 13 C c3 3 O bCo ^ ^ -^ ^ S o 2 (=-= 2 S c3 bO G 3 " m O o o S ^ o"5. ^-^ 3 J3 p CO O = J -s a o 1^ •43 ai M C 2 o C c! fc- C O 03:7: a > s o "2 '^ 'S, o >>a CO o-:3 c3 ^ "5 --- Coo rt > CO S 3 cor; 02 k! o > c3 -r; c3 j:: C t, - c?x; — -JJ i) -»-' a: "t: 3 o ^ O 22 O 72 "2 'o -ii e c3 JU M H 0) 0 3 4> ca H 3 0 Ig O JU s*^. Chap. VII] SUMMARY 123 -73 o -a §° -^ d ^ r- . C |> ^ O C 03 rH c: •- o a o o nil -M rj a ;h -3 o C -^ 3 c3 03 §^ bC^ ^ -=5 -•=•£: -C! 03 tC Go -^-^ - >i .25 ^a g ^ o a cc 'n 'C Q <: o o .2 ^' „ :=! o p ■" .2 '^ rj 'm •^ Tj 'T ?3 -< o^ o V.2 St3 fl 2-S o f-i C3 C3 S o 03 03 _C ^ vis- and vis. i.i 03 S o ^ o X o gT3 T) omi e ri nth s-a XJ OS ^ o T3-G O 03 X!*" a 03 "^ ^ o3 =3 the esses hest O " 2 tH 03 5R ^ 03 o ^-^^ O Oj o3 CO 03 r/) CO " -. q; ompr cera, flcxe CO rr O tH 0 " U p u a . _, CO M X -C _Q 03 O O •!-■ "o o3 o3 ^•^ lh 03 03 03 O) <+-! t*-! ->^ ^ o o ^ 3 tn S-, '^ 03 03 03 03 H tH ^ S JD .03 t: -T-, -l^ CB 03 ^. p a Is cj^ o3 03 S £3 O) 03^ ^ 03 t., 03 ^ 03 Oi o p. a—' &■ !=1 bC 03 fl ,0 03 O) ^j -*^ a d, o , ^ o 3 O o o fi to «-' 03 bC ~ ^■^03-^ << O 03 ^ « '^ S C! r^ t- 03 *3 d 03 « 03 "S 03 So II 13 a O 13 o> o3 a 3 CO M 03 bC 03 o ;-( t3 CO ;::^^ o CO _, 03 '^ CO o3 O 9^ SrS g ^ ^ Oj G 3 03 g3 03 03 CO ^; ' > OJ CO -g > C 03 > O 03 ^ 03 S S ° Z3 o3 b 2 03 5S ^ S bjO 03 ^ 03 O— 1 bO 03 CO ^^ 03 -^ _, o ^ tH r-T 03 X! •-< 03 c t; C =' — "*- 3 I— I Ah ,X -"-d A ci ^ ^ t4_, c3 3 C5 C/J O C o 3 hf X — < C •^ '"^ CO ;-H CO"-!^ o3 O^ bC p 3 O 3 bO s Ah .i:^ h5 3 rr a 42 o bU _^ 03 ni ^ & 03 n -tJ X « W :3 o c _2 ^ P^ 124 ANATOMY FOR NURSES [Chap. VII g o o3 V.-I i «4-l 3 ^ o a. l G^ 1 C5 • TS -d § - . M 3 o3 a o ■■g a s M o a a^ Oj o rt CD CO 03 o -♦J «« o o o +J ^3 , c o % o 3 't: X o o fl •S -3.2 ,3 S-" ^t? o o o ^ bC+^ O 0) -tJ 3 73 ? "O C^ ^"^ "a o 5 c "^ , "rt -t^ t< 0) ^ o Q S-i fc- C; - «^ — t|< .-S^-v t- 03 t- .3 i-i 3 ^ O It's S Q< § s a So 3 O <*- 2 3 ci-tS g-S G,c3 03 a 3 a D, ID Ph fc fe s S « m SJO^BUOJ^ sjoxa^ sjo :^'Butdng » ^__ W >> a> n (X a> o. J- &** Chap. VII] SUMMARY 125 tM 1 t*-* §2 t3 o3 .2 !=! 2 !=! =^^H e*H «H-I e<-l ;-i C C Crp, S O O o ;=! o o o X5 '^ c3 d sag CD o a o il 4> r3 II c3 Pi c3 o3 O m cS o3 o «^ p! o3 43 o o o ^_^ a 53 ;-, 03 t, g"5 irpi ulnaris (in the pel \x\j of thigh) CO 2~ 1 -2 a CO CO ;3 :=! bC 03 a bi)'> CO o3 bb CS O ^-- o ,~, :- .« 03 a 1 a CO o o o O ^ -2 ^ CO c^ 23 > forearm :tcnsor ( niagnui upper p 2 a a 'a o -^ o CO tc CO -li ^<^ -< w^-g CO 3 ,^ "^ ^ ^ d ^ O t^ -♦-3 o I^JOUIOJ pUJO'^UJ sjosua^xg ^ 2 1— I 3 o & ^ J X « >> W >> ■^ ■^ ^ ^ >< o — o O — .2 X tf. -r _£ "^ "2 t ^'t a o a 3 5 bO o 3 '-2 ^3 ■^ 03 C "S_bC "y. o'-S X > "?.«*;'?.'*; ii.2 go li O o c3-d .->< O O O ao O ^^ O "< «*- rt*-^ . .2 3.2 =3 CO ^ X ^ _ C 2 3 - , 3 O O o ^ C 73 3 1 o (-< CO (U 1 bO j (O e3 [ o § W s S S S H W fil W . . ^ >v , , ^^ 1 CO o -t; "*-* c3 o O C - sU t- — - ■ £j ^ »*- E O o ^' -*-' rt :3 1 _2 o a o o u e3 23 ■+3 o 4> m a 1-4 2 3 to c3 C -IS 1— 1 o3 -^S C -t^ .S ^^ to^-- C3 c ^ ^ 2 f=^ 2^-^ EPh ^ io c^ tt 3J ^^ 2? H CO 3 3 " 1 s .3 ;rt 3 S g .2 i 2 § j2 1 '^Ut% ^ 03 a 3 IS bb a, ^ V" O 3 -3 -§ b h %%% ^ISI^' .2 1 1 e3 _c3 .^ o jz;feCiHfi^< ^iS^^ H S H H p^ p^ P^ >^ ^ C ,tj t*- i> «*- t- «*-! t- •a a 4> '^ CO .2 2^3 g 22 23 22 ill 22 ^'^ § c_ c -so 2^ t-s-5 siii.S ^"^ "St- — — ^-— ' 53 o c 3 to o " o o 3 O 33 22 ''^ 1^ to «« o 3o o ?■ S "« ^ "* 2 IS bC 3 OS — ' o Muscl e foun 2 i^ w en CO 3 q c3 cS _. - o ^ C-.ti.S CO O 3-3 CO bC,^^ •^ ^O _0 .^ = p £f--^«t; O 3 O p.- 3 O S ?3^ S CO 3 ..J •-■ r* o C ■-J c, W .ti u 6 4> 0) O 1 >A CHAPTER VIII SPECIAL MEMBRANES AND GLANDS MEMBRANE The word " membrane " in its widest sense is used to designate any thin expansion of tissue. Thus we speak of the periosteum as a fibrous membrane ; and the layer of cells beneath the epi- thelium of free surfaces is called a basement membrane. In a restricted, although the commonest sense, the word " membrane " is used to denote an enveloping or a lining tissue of the body. Classification of membranes. — The chief membranes of the body are classified as follows : — 1. Serous. 2. Synovial. 3. Mucous. 4. Cutaneous. SEROUS MEMBRANES Serous membranes are thin, transparent, tolerably strong, and elastic. The surfaces are moistened by a fluid resembling serum, from which the membranes obtain their name of serous mem- branes. They consist of two layers only: (1) endothelium, (2) corium. (1) Endothelium is the name given to a variety of epithelium found lining {i.e. lying within) certain parts of the body. It consists of a single layer of flattened transparent cells joined edge to edge so as to form a smooth membrane. (2) The corium consists of a thin layer of fibrous tissue, and con- tains blood-vessels, lymph-vessels, and lymphoid tissue. Serous membranes are attached to the underlying parts by areolar tissue, called " subserous " tissue. They are found lining closed cavities and passages that do not communicate with the exterior. They may be divided into three classes : — 127 128 ANATOMY FOR NURSES [Chap. VIII (1) . Serous membranes proper. (2) The lining membrane of the vascular system. (3) The liniiiij inc'nii)rane of certain cavities. (1) Serous membranes proper. — With one exception, these membranes form closed sacs, one part of which is attached to the walls of the cavity which it lines, — the parietal portion, — whilst the other is reflected over the surface of the organ or organs con- tained in the cavity, and is named the visceral portion of the mem- brane. In this way the viscera are not contained within the sac, but are really placed outside of it, and some of the organs may receive a complete, while others receive only a partial, or scanty, investment. This class of serous membranes includes : — (a) The two pleurw, which cover the lungs and line the chest. (6) The pericardium, which covers the heart, and lines the outer jfibrous pericardium. (c) The peritoneum,^ which lines the abdominal cavity, clothes its contained viscera, and also the upper surface of some of the pelvic viscera. (2) The lining membrane of the vascular system. — This applies to the internal coat of the heart, blood-vessels, and Ij-mphatics. It bears a close resemblance to the proper serous membranes in structure and appearance. (3) The lining membrane of certain cavities : — (a) One illustration of this is the capsule of Tenon. This capsule is a shut sac placed back of the eyeball, with a visceral layer upon the globe of the eye, and the parietal layer next to the bed of fat on which the eyeball rests. (6) The brain and spinal cord enclose cavities which are lined with a delicate serous membrane. One of the membranes that envelop the brain and spinal cord (arachnoid) is also a serous membrane. Function of serous membranes. — The most important function of serous membrane is protection, which is accomplished in two ways : (1) by forming a smooth, slippery lining or covering for the viscera, blood-vessels, and cavities with which it is associated, and 1 The peritoneum in the female is the one exception to the rule that serous mem- branes are perfectly closed sacs, as it has two openings by which the Fallopian (uterine) tubes communicate with its ca\nty. Chap. VIII] SPECIAL MEMBRANES AND GLANDS 129 (2) by secreting serum which acts as a lubricating fluid and tends to lessen friction. The inner surface of a serous membrane is free, smooth, and polished ; and in the case of serous membranes proper, the inner surface of one part is applied to the corresponding inner surface of some other part, only a very small quantity of fluid being interposed between the surfaces. The organs situated in a cavity lined by a serous membrane, being themselves also covered by it, can thus glide easily against its walls or upon each other, their motions being rendered smoother by the lubricating fluid. SYNOVIAL MEMBRANES Synovial membranes are frequently classed as serous membranes, because their function is the same and they have no communica- tion with the surface of the body. They differ, however, (1) in the nature of their secretion, (2) in their structure, and (3) they are associated with the bones and muscles, and not with the viscera. Synovial membrane is composed of fibrous tissue which has on its free surface an imperfect covering of cells that are irregularly shaped, and secrete a viscid glairy fluid that resembles the white of egg, and is named synovia. They are divided into the following classes : — 1. Articular. 2. Vaginal. 3. Bursal. 1 . Articular. — Articular synovial membranes are found sur- rounding and lubricating the cavities of the movable joints in which the opposed surfaces glide on each other. 2. Vaginal. — Vaginal synovial membranes are found forming sheaths for the tendons of some of the joints, and thus facilitating their motion as they glide in the fibrous sheaths which bind them down against the bones. 3. Bursal. — Bursal synovial membranes, or synovial bursae, are found in the form of simple sacs, interposed, so as to prevent friction, between two surfaces w^hich move upon each other. These bursse may be either deep-seated, or subcutaneous. The deep-seated are for the most part placed between a muscle and a bone, or between a tendon and a bone. The subcutaneous 130 ANATOxMY FOR NURSES [Chap. VIII bursae lie immediately under the skin, and occur in various parts of the body, interposed between the skin and some firm promi- nence beneath it. The large bursa, situated over the patella, is a well-known example of this class, but similar, though smaller, bursa? are found also over the olecranon, the malleoli, the knuckles, and other prominent parts. Function of synovial membranes. — As previously stated, the function of synovial membranes is similar to that of serous membranes, but synovial membranes are associated with the bones and muscles. MUCOUS MEMBRANES The mucous membranes, unlike the se- rous membranes, line passages and cavities which communicate with the exterior. Their surface is coated over and protected by mucus, from which it derives its name. The mucous membranes of different parts are continuous, and they may nearly all be reduced to two great divisions ; namely, (1) gastro-pulmonary, and (2) the genito- urinarv. k i\\ J Fig. «9. — The An- terior Annular Liga- ment OF THE Ankle AND the Synovial Mem- branes OF the Tendons BENEATH IT. Artifuially distended. (Gcriish.) (1) Gastro-pulmonary. — The gastro-pul- monary mucous membrane covers the inside of the alimentary canal, the air-passages, and the cavities communicating with them. It commences at the edges of the lips and nostrils, proceeds through mouth and nose to the throat, and thence is continued throughout the entire length of the alimentary canal to the anus. At its origin and termina- tion it is continuous with the external skin. It also ex-tends throughout the trachea, bronchial tubes, and air-sacs. From the interior of the nose the membrane may be said to be prolonged into the frontal, ethmoidal, sphenoidal, and maxillary sinuses, also into the lacrimal passages, and under the name of conjunc- tival membrane, over the fore part of the eyeball and inside of the eyelids, on the edges of which it again meets with the skin. Chap. VIII] SPECIAL MEMBRANES AND GLANDS 131 From the upper and back part of the pharynx a pro- longation extends on each side, along the passage to the ear, — Eustachian tube,^ — and offsets in the ahmentary canal go to Hne the saHvary, pancreatic, and biHary ducts, and the gall-bladder. (2) Genito-urinary. — The genito-urinary mucous membrane line^ the inside of the bladder, and the whole urinary tract from the interior of the kidneys to the meatus urinarius, or orifice of the urethra ; it also lines the vagina, uterus, and Fallopian (uterine) tubes in the fe- males. A study of Figs. 91 and 92 will make this plain. Structure. — A mucous membrane is composed of a layer of connective tissue called the corium, which is bounded toward the free surface by a basement membrane and covered by a layer of epithelium. Be- neath the corium we usu- ally find a thin layer of muscular tissue called the muscularis mucosae. From the above, it will be seen 1 Named after Eustaehius, a famous anatomist. FRONTAL SINUSES 0UCT8 OF LACHRYMAL GLANnS UPPER LIDS EY[ LOWER LIDS TEAR DUCTS .ETHMOIDAL SINUSES .SPHENOIDAL SINUSES ,MAXILLAR¥ SINUSES ^MIDDLE EARS I MASTOID CAVITIES EUSTACHIAN TUBEJ Fig. 90. — Dia- gram OF THE GaSTRO- PULMONARY MuCOUS Membrane, show- ing THE Continuity OF ALL ITS Parts. (Gerrish.) 132 ANATOMY FOR NURSES [Chap. VIII that, starting at the free surface, the order of the tissues is as follows : — (1) Epithelium. (2) Basement membrane. (3) Corium. (4) Muscularis mucosae. (1) The epithelium is the most constant part of a mucous membrane, being continued over certain regions to which the other parts of the membrane cannot be traced. It may be scaly Fig. 91. Diagram of the Female Genito-urinary Mucous Membrane, SHOWING Continuity of all its P.\rts. (Gerrish.) and stratified, as in the throat, columnar, as in the intestine, or ciliated, as in the respiratory tract. (2) The basement membrane consists of a layer of flattened cells, and is really j)art of the corium. (3) The corium of a mucous membrane is composed of either areolar or hinphoid connective tissue. It is generally much thicker than in serous or synovial membranes, and varies much in structure in different parts. (4) The muscularis mucosae consists, as previously stated, of a thin layer of muscular tissue. The mucous membranes are attached to the parts beneath them by areolar tissue, here named " submucous," and which differs greatly in quantity as well as in consistency in different parts. The connection is in some cases close and firm, as in the cavity Chap. VIII] SPECIAL MEMBRANES AND GLANDS 133 of the nose. In other instances, especially in cavities subject to frequent variations in capacity, like the oesophagus and the stomach, it is lax; and when the cavity is narrowed by contraction of its outer coats, the mucous membrane is thrown into folds, or rugae, which disappear again when the cavity is distended. But in certain parts the mucous membrane forms permanent folds that cannot be effaced, and which project conspicuously into the cavity which it lines. The best-marked example of these folds is seen in the small intestine, where they are called valvulce conniventes^ (cir- cular folds), and which are doubtless provided for increasing the amount of absorbing surface for the products of digestion. In some locations the free surface of mucous membrane contains minute glands, or it is covered with papillse, villi, or cilia. PapillcB. — The papilhe are best seen on the _ _ ,, ^ Fig. 92. — Diagram of the Male Genito- tongue ; they are small urinary Mucous Membrane showing Conti- e J.1 • NuiTY of all its Parts. (Gerrish.) processes or the conum, ^ mostly of a conical shape, containing blood-vessels and nerves, and covered with epithelium. Villi. — The villi are most fully developed on the mucous coat of the small intestine. They are little projections of the mucous membrane, covered with epithelium, containing blood-vessels and lacteals, and are favorably arranged for absorbing nutritive matters from the intestines. Cilia. — For description of cilia see page 28. Function of mucous membranes. — The function of mucous membranes is (1) protection, (2) support of blood-vessels and lymphatics, (3) to furnish a large amount of surface for absorption. (1) It protects by forming a lining or inside skin for all ' See page 266. 134 ANATOMY FOR NURSES [Chap. VIII the passages that communicate with the exterior. These jxissages are subject to the contact of foreign substances, which are introduced into the body, and waste materials, which are expelled from the body. The mucus which it secretes is a thicker and more sticky fluid than either serum or synovia, and by coating the surface lessens the possibility of irritation from food, waste materials, or secreted substances. The cilia of the respiratory tract also assist in the function of protection. They keep up an incessant motion, and thus carry mucus toward the outlet of these pas- sages. Dust and foreign materials usually become entangled in the mucus and are forced out with it. (2) The redness of mucous membranes is due to their abundant supply of blood. The small blood-vessels which convey blood to the mucous membranes divide in the sub- mucous tissue, and send smaller branches into the corium, where they form a network of capillaries just under the basement mem- brane. The lymphatics also form networks in the corium, and communicate with larger Fig. 93. — An Jntes- vessels in the submucous tissue below. :r,^nI;'''^Tpith'::iir; (3) The modifications of mucous mem- b, h, capillary network ; brane, such as the valvulre conniventes, pa- d, lacteal vessel. . , , .,,. i i i> i i> piUfe, and villi, are largely tor the purpose ot increasing the surface for absorption, and also to enable it to carry more blood-vessels and lymphatics. CUTANEOUS MEMBRANE By this term is indicated the membrane which covers the body and is commonly spoken of as skin. It is a complex structure, iind has several functions in addition to serving as a protective covering for the deeper tissues lying beneath it. It will be more fully considered in Chapter XVIII. GLANDS A gland is a secreting organ, or an organ which abstracts from the blood certain materials and makes of them a new substance. Chap. VIII] SPECIAL MEMBRANES AND GLANDS 135 The simplest form of a gland may consist of just one cell, such as the goblet cells/ or may be a mere depression on the surface of a membrane, or a complex organ like the liver. No matter what the size or shape may be, all glands have three essential characteristics: (1) epithelial cells which are the active secreting agents, (2) a liberal blood supply from which the material for the secretion is drawn, (3) they are under the direct control of the ner- vous system and secretion is their response to stimulation, just as contraction is the response of a muscle. The usual arrangement is for the cells to cover the free surface of a basement membrane, a dense network of capillaries to be spread upon its under surface, and nerve fibrils to form a network in contact with the cells. Fig. 94. — Dl^gram showing De\t;lopment of Glands: A, a mere dimple in the surface ; B, enlargement by division ; C, enlargement by dilatation ; D, a combi- nation of B and C ; E, a. raeemosp gland ; F, development of method oi E ; G, & single tube intricately coiled. (Gerrish.) In order to economize space and to provide a more extensive secreting surface, the membrane is generally increased by dipping down and forming variously shaped recesses. Classification. — The secreting glands are of three kinds : — 1. Simple. 2. Compound. 3. Ductless. L Simple glands. — The simple glands are generally tubular or saccular cavities, which open upon the surface by a single duct. They are named simple tubular, or saccular glands. Sometimes the tube is so long that it coils upon itself, as in the sweat glands of the skin. These are named simple convoluted tubular glands. 2. Compound glands. — In the compound glands the cavities are subdivided into smaller tubular or saccular cavities, opening > See page 267. 136 ANATOMY FOR NURSES [Chap. Mil by small ducts into the main duct, which pours the secretion upon the surface. If composed of many tubes, either straight or convoluted, they are called compound tubular glands; if composed of gr()Uj)s of small sacs, they are called racemose glands. 3. Ductless glands. — This term is applied to a collection of glandular structures that possess no ducts. Whatever secretion or excretion they produce is discharged into the blood, either directly or indirectly by way of the lymphatics. SECRETION A new substance, the product of a gland, elaborated from the blood by cell action, and intended for use in the body is called a secretion. For purposes of study we may divide the secretions into two groups : — (1) External secretions. (2) Internal secretions. External secretions. — This term is used to designate those secretions of glandular tissues which are carried to their destina- tion by a duct. All of the digestive juices — saliva, gastric juice, pancreatic juice, bile, and intestinal juice — are examples of ex- ternal secretions, because thej' are carried off from the respective glands in which they are formed by means of ducts. Function. — The function of the external secretions is dealt with in connection with the organs which produce them. Internal secretions. — This term is used to designate those secretions of glandular tissues which are not carried off to the exterior by a duct, but instead are discharged into the blood or l\Tnph. The conception is that probably all the ductless glands form secretions which have a profound influence on nutritive changes in the body. Such secretions are called internal secre- tions. It has also been shown that not only the ductless glands, but some at least of the typical glands provided with ducts, may give rise to internal secretions. For example, the pancreas forms the pancreatic juice and discharges it by means of a duct into the small intestine. In addition, it is believed that the pancreas forms an internal secretion which passes into the blood. Function. — On account of the difficulty of separating internal Chap. VIII] SUMMARY 137 secretions from the blood or lymph, the precise nature of their composition or function is not known, beyond the fact that most of them are essential to metabolism and they contain chemical substances called hormones. The term hormone is suggestive, because it means messenger and is applied to a substance which is produced in one organ and on being carried by the blood to an- other organ stimulates this latter to functional activity. Excretion. — An excretion resembles a secretion, except that whereas the secretion is intended for use in the body, the excretion is generally formed to be thrown out of the body. It therefore follows that all excretions are first secretions, and some substances are made use of before they are eliminated. For instance, bile serves several purposes before it is eliminated, so that it is first a secretion and then an excretion. Urine, on the other hand, is a secretion, but is formed only to be eliminated. Definition — Varieties SUMMARY I Any thin expansion of tissue. I An enveloping or lining tissue. 1. Serous membranes. 2. Synovial membranes. 3. Mucous membranes. 4. Cutaneous membranes. Consist of 1 . Endothelium — a single layer of flat cells. 2. Corium — ■ a thin layer of fibrous tissue. Found — lining closed cavities or passages that do not communicate with the exterior. They are moistened by serum. ' Pleurae — cover the lungs and line the chest. Pericardium — covers the heart and lines the outer fibrous pericar- dium. Peritoneum — covers the abdominal and the top of some of the pel- Three Classes { vie organs, lines the abdominal cavity. Lining membrane of the J r>i j i ^ , \ Blood-vessels, vascular system I y , ,. •' "> Lymphatics. ' Serous membranes proper - 138 ANATOMY FOR NURSES [Chap. VIII Lining membrane of cer- tain cavities Function — Protection • Back of eye — capsule of Tenon. Lining membrane of the cavity of the central nervous system. Viscera. Vascular sj'^stem. Certain cav- ities. Furnishes a secretion — serum — which acts as a lubricant. 1. Furnishes a cover or lining. Consist of [l Three Classes ■ Imperfect layer of irregularly shaped cells. Layer of fibrous tissue. / ... , . , , f Surround cavities of Articular synovial membranes { , , . ■ [ movable jonits. Vaginal synovial membranes for Bursal synovial membranes Function — Protection Furnishes a cover or lining Found Two Divisions Consist of J Form sheaths 1 tendons. ■ Sacs interposed be- tween two sur- faces which move upon each other. Joints. Tendons. Sacs be- tween muscles and bones. Furnishes a secretion — synovia — which acts as a lubricant. lining passages that communicate with the exterior and are protected by tniicus. Alimentary canal. Air-passages. Gastro-pulmonary | Cavities communicating with both alimentary canal and air- passages. J Urinarj' tract. \ Generative organs, r Stratified. 1. Epithelium { Columnar, i Cihated. 2. Basement membrane, a layer of flat cells. I Areolar tissue, or I LjTiiphoid tissue. Genito-urinary 3. Corium Chap. VIIIJ SUMMARY 139 Consist of Modifications Function Definition Structure Classification I 4. Muscularis mucosae — thin layer of muscular tissue. Ruga. - temporary folds { ^^^^^^^^'^ Valvulse coniiiventes — permanent folds of mucous membrane found in small intestine. Papillae — conical processes of mucous membrane best seen on tongue. Contain blood- vessels and nerves. Villi — tiny thread-like projections of the mucous membrane of small intestine. Cilia — hair-like processes. r Inside skin. Protection < Secretion of mucus. I Action of cilia. Support — for network of blood-vessels. Absorption — • Various modifications increase the surface. Glands are organs that form secretions. A single cell, or many cells arranged in various ways. Epithehal cells. A Uberal blood-supply. Intimate connection with nervous system. Tubular — ■ tube shape. Saccular — sac shape. Convoluted tub ular — Ion g tube coiled upon itself. f Compound tubular — many 2. Compound — wa?i?/ tubes. I Racemose — many sacs. no duct \ Essentials 1. Simple — one duct ducts 3. Ductless Definition — the glands Classification Secretions are substances elaborated from the blood by They are intended to perform some office in the body. External secretions — are substances formed by the simple and compound glands and discharged by means of a duct. Internal secretions — are substances formed by any kind of gland and discharged into the blood or lymph. External secretions — studied later. f Essential to metabolism. 1 Stimulate by means of hormones. Excretion — a secretion which is ehminated. Function Internal secretions 140 ANATOMY FOR NURSES [Chap. VIII TABLE OF SECRETIONS AND EXCRETIONS Secretion Secreting Organs Reaction Main Purpose Mucus Mucous cells of mucous mem- brane Alkaline Lubricant and diluent. Serous Serous mem- Alkaline Lubricant and diluent. secretion branes Tears Lacrimal glands Alka,Une To moisten the conjunctiva. Saliva Salivary glands Alkaline To moisten food and digest car- bohydrates. Gastric Stomach Acid To digest proteins. juice Pancreatic Pancreas AlkaUne To digest proteins, fats, and juice carbohj^dratcs. Succus Intestines Alkaline To dilute the chyme. entericus Bile Liver Alkaline Part of the bile is used in diges- tion and reabsorbed. Part is a true excretion (bile pig- ments). Milk Mammary glands Alkaline Food. Sebum Sebaceous glands of the skin AlkaUne To oil the skin. Sweat Sweat-glands of Acid Elimination of water, carbon skin dioxide, and urea. Helps to regulate body-temperature. Vaginal Vagina Acid Lubricant, moistening and pro- tection. Urine Kidneys Acid Elimination of water and urea. Vascular System • CHAPTER IX VASCULAR SYSTEM; THE BLOOD AND LYMPH It is helpful to remember that the body consists of an enormous number of individual cells, and that each cell must be supplied with materials, to enable it to carry on its activities, and at the same time it must have the waste materials that are the result of its activities removed. Many cells are far from the source of supplies and the organs of elimination ; hence the need of a medium to distribute supplies and collect waste, and the need of a system so that the distribution will be orderly and systematic. These two needs are met by the vascular system, the divisions of which may be outlined as follows : — Circulating fluids I ^ , „ , I Blood vascular Systems 1 t i i •^ I Lymph vascular. THE BLOOD Characteristics. — ■ The most striking external feature of the blood is its well-known color, which is bright red, approaching to scarlet in the arteries, but of a dark red or crimson tint in the veins. It is a somewhat sticky liquid, a little heavier than water; its specific gravity is about L055. It has a peculiar odor, a saltish taste, a slightly alkaline reaction when tested with litmus, and a temperature of about 100° F. (37.8° C). Quantity of blood. — The quantity of blood contained in the body is estimated to be about 2V of the body weight. This pro- portion was formerly said to be about -5^3, but later experiments seem to place the figure at aV- This, in an individual weighing 160 pounds, would weigh about 8 pounds, or measure 4 quarts. Functions of the blood. — Blood is commonly spoken of as the nutritive fluid of the body. This is quite correct, but it is more than a nutritive fluid, as will be seen from the following list of its more important functions : — 141 142 ANATOMY FOR NURSES [Chap. IX (1) It carries to the tissues water and the nutritive substances resulting from digestion. These are required by each individual cell in order to enable it to carry on its metabolic processes. (2) It carries to the tissues oxygen, absorbed from the air in the lungs. Every individual cell requires oxygen, in order to provide heat and energy. (3) It carries from the tissues various waste ])roducts. These are not only useless, but poisonous, and must be eliminated by the lungs, kidneys, and skin. (4) It serves as a medium for the transmission of certain secretions. The presence of these secretions promotes oxidation and metabolism. (5) It aids in equalizing the temi)erature of the body. Blood passing through a tissue which is undergoing lively metabolism will have a higher temperature when it leaves than it had when it entered. This extra temperature will be lost in passing through a tissue that is not so active. In this way an average temperature is maintained. (()) It aids in protecting the body from infections. Composition of the blood. — Seen with the naked eye, the blood appears opaque and homogeneous ; but when examined with a microscope it is seen to consist of minute, solid particles called corpuscles, floating in a transparent, slightly yellowish fluid called plasma. Red or erj'throcytes. Corpuscles \ White or leucocjrtes. Blood plates. Water, £0 %. Blood { Proteins. Extractives. Inorganic salts. Gases. Enzj'^mes. Internal secretions. Immune bodies. Red corpuscles. — The red corpuscles are circular biconcave disks, with rounded edges. The average size is s^^-q of an inch (0.008 mm.) in diameter, and about 12^0^ (0.002 mm.) of an inch in thickness. Because of their extremely small size, the red cor- puscles do not appear red when viewed singly with a microscope, Plasma Chap. IX] VASCULAR SYSTEM 143 but merely of a reddish yellow tinge, or yellowish green in venous blood. It is only when great numbers of them are gathered together that a distinct red color is produced. Authorities differ regarding the structure of the red corpuscles. Some describe them as consisting of a colorless filmy, elastic frame- work infiltrated in all parts by a red coloring matter termed haemoglobin, which contains a small amount of iron. Others describe them as consisting of a colorless elastic envelope enclosing a solution of haemoglobin. In either case it is correct to consider them as packets of haemoglobin moving passively at the mercy of the blood current. They have no nuclei, are soft, flexible, and elastic, so that they readily Squeeze through apertures and passages narrower than their own diameters, and immediately resume their proper shape. Function of the red corpuscles. — The red corpuscles, or eryth- rocytes, by virtue of the haemoglobin which they contain, are emphatically oxygen carriers. Exposed to the air in the lungs the heemoglobin becomes fully charged with detachable oxygen and is known as oxyhsemoglobin. The red corpuscles carry this oxyhsemoglobin to the tissues, where it gives up the loosely en- gaged oxygen. It is then known as reduced haemoglobin and is ready to be carried to the lungs for a fresh supply. The color of the blood is dependent upon this combination of the haemoglobin with oxygen ; when the haemoglobin has its full complement of ox^'gen, the blood has a bright red hue ; when the amount is de- creased, it changes to a dark crimson hue. The scarlet blood is usually found in the arteries, and is called arterial; the dark crimson in the veins, and is called venous blood. Life cycle of the red corpuscles. — There is every reason to believe that the red corpuscles, like all the cells of the body, have a definite term of existence, then disintegrate and are replaced by other corpuscles. They originate in the red marrow of the bones, but in case of special need, as after the loss of a large number by hemorrhage, they can be formed in other organs, especially the spleen. Before being forced into the blood stream they lose their nuclei, and this suggests that they do not live a great while in the circulation. Red corpuscles in various stages of disintegration have been found in the substance of the spleen and lymph nodes. Some authorities consider that their destruction takes place in 144 ANATOMY FOR NURSES [Chap. IX these organs, but others consider that it takes place in the blood in any part of the system. Number of red corpuscles. — The average number of red cor- j)uscles in a cubic niillinietre of healthy blood is given as 5,000,000 for men and 4,500,000 for women. Even in health this number varies and in disease it may be greatly reduced. An increase in temperature hastens the destruction of red corpuscles, and in this way causes a reduction in number. The condition known as anemia may be due to a diminished number of red corpuscles, which means a diminished supply of ox^'gen, and a consequent inter- ference with the processes of metabolism. White corpuscles. — The white corpuscles are masses of proto- plasm containing a nucleus, sometimes even two or three nuclei, and they have no cell wall. Their form is very various, but when they are carried along in the blood current, or when the blood is first drawn, they are rounded or spheroidal. Measured in this condition, they are about osVcr of an inch (0.010 mm.) in diameter. The white corpuscle may be taken as the type of a free animal cell. Number of white corpuscles. — The average number of white corpuscles in a cubic millimetre of healthy blootl is from 7000 to 9000, or in the proportion of 1 white to 500 or 600 red. A marked increase in number is designated as leucocytosis, a marked decrease as leiicopenia. Under various normal conditions, such as digestion, exercise, or cold baths, leucocytosis occurs. It also occurs under abnormal conditions, and a knowledge of the variations under pathological conditions is an important aid in diagnosis. Varieties of white corpuscles. — At least five varieties have been studied and described. They are classified under two main groups : — (1) Leucocytes. (2) Lymphocytes. The most marked difference is in the nuclei and in the amount of amoeboid movement exliibited. The difference is said to be due solely to the age of the corpuscle — the lymphoc\'te being the more recently formed, and in time will change into a leucocyte. Each of these groups may be subdivided into two or more subgroups, and some authorities hold that each variety has some special function, but this has not been proven. Chap. IX] VASCULAR SYSTEM 145 Amoeboid movements. — One distinctive property of white blood corpuscles is their power of making amoeboid movements, which enables them to change their form and escape through the walls of the blood capillaries into the surrounding tissues. This property has earned for them the title of wandering cells, and the process is spoken of as migration. It occurs under normal condi- tions, but is vastly accelerated under pathological conditions. Function of the white corpuscles. — It is definitely known that they act (1) as protective agents, (2) aid in the absorption of fats and proteins from the intestines, and (3) assist in the coagulation of the blood. Their function of protection is very important, and is accom- plished in two ways : — (a) By forming certain substances called bacteriolysins, which when imbibed by bacteria kills them ; (b) by virtue of their amoe- boid movements they can creep around bacteria, envelop them with their own substance, and so put them inside themselves. This process is called phagocytosis, and has earned for them the name of phagocytes. Opsonins. — This is a name given to chemical substances found in blood plasma. The function of an opsonin ^ is to prepare certain disease germs for destruction and absorption by the white cor- puscles of the blood. The phagocytic properties of the leucocytes become especially developed as the result of the action of opsonins. Inflammation. — When any of the tissues become inflamed either as the result of injury or infection, the first effect is irritation, followed by an increased supply of blood to the part. If the irri- tation continues or is severe, the flow of blood begins to slacken, and a condition of stasis or engorgement results. The white corpuscles become particularly active and migrate into the infected tissues in large numbers. Some of the blood plasma exudes, and a small number of red corpuscles are forced through the capillary walls.2 This general condition is described as inflammation, and the symptoms of pain, heat, redness, and swelling are due, (1) to the increased supply of blood, (2) to the engorgement of the blood- vessels, and (3) to the collection of fluid in the tissues, which is 1 From opso'no, I prepare food for. " This passive ability of red corpuscles to pass through the capillary walls is called diapedesis. 146 ANATOMY FOR NURSES [Chap. IX spoken of as inflammatory exudate. Under these conditions a death struggle between the leucocytes and bacteria takes place. If the leucocytes are victorious, they not only kill the bacteria but remove every vestige of the struggle, and find their way back to the blood. If the bacteria are victorious, and suppuration ensues, the leucocytes become pus corpuscles. Also, in the case of a wound, the leucocytes, by virtue of their amoeboid movements, escape from the blood-vessels, accumulate in the region of the wound, and act as barriers against infection. Life cycle of the white corpuscles. — It is presumed that the white corpuscles like all other cells have a definite term of existence. We do not know the length of this term, or where they are de- stroyed, except that large numbers are lost in the battle waged against bacteria, others by hemorrhage, and others may be con- verted into granulation tissue. These lost leucocytes are replaced by new leucocytes which result from the division of former leuco- cytes. This division usually takes place in the lymph nodes and the spleen. Differences between white and red corpuscles. — (1) White blood-cells are larger than red corpuscles, but normally are present in smaller numbers. (2) They have no pigment or haemoglobin, hence are colorless. (3) On account of the property of amoeboid movement their shape varies. (4) They always have a nucleus, sometimes two or three nuclei. (5) There are five varieties that differ in microscopical structure and possibly in function. (6) During circulation they keep close to and even seem to adhere to the walls of the vessels, while the red corpuscles keep in the middle of the stream. (7) By virtue of their amoeboid movement they escape through the walls of the capillaries and are found in the tissue spaces. They are also found in lymph, chyle, and pus. (8) The functions of the white blood-cells are quite different from the red corpuscles. Blood-plates. — They are small, pale yellow, or colorless disks of which little is known. They vary in size and shape, but are always smaller than the red corpuscles. It is not decided whether they are to be considered as independent cells or as fragments Chap. IX] VASCULAR SYSTEM 147 of disintegrated cells. The number is usually about yV the number of red corpuscles. Function. — When the blood leaves the blood-vessels and comes in contact with foreign matter, the blood-plates and some of the white corpuscles disintegrate and give rise to a substance called prothrombin. This is acted upon by substances in the blood plasma and converted into thrombin, which is one of the essentials for the formation of a clot. Plasma. — The plasma of the blood is of a clear, slightly yel- lowish color. It consists for the most part of water charged with nutritive matter derived from our food, and waste matter derived from the tissues. In other words, it consists of water holding in solution or suspension : — r Serum-albumin. Proteins . . . . < Para-globulin or serum-globulin. I Fibrinogen. Sugars. Fats. Lecithin Cholesterin Urea Uric acid Hippuric acid Creatin Extractives Represent waste products. Inorganic Salts Gases . . Enzymes Internal Secretions Immune Bodies Chlorides Sulphates Phosphates Carbonates ( Ox.vgen. < Nitrogen. I Carbon Dioxide. of Sodium. Calcium. Magnesium. ( Opsonins. I Antitoxins. I Antibacterial substances. Proteins. — There are many indications which support the belief that the actual number of individual proteins is much greater than the usual three mentioned in our list. Our knowledge of these substances, and of the particular value of each one in the system is limited. 148 ANATOMY FOR NURSES [Chap. IX Serum-albumin belongs to the group of albumins of which white of egg is a member and holds the first place in regard to nutrition. It represents the protein portion of our food supply and the greater part of the material necessary for the daily nourishment and renovation of the tissues. In this process it undergoes a variety of transformations, by which it is converted into the struc- tural characteristics of the tissues which it supplies. Para-globulin ^ belongs to the class of globulins. The origin and function are undecided. It may be a source of nitrogenous food, and assists in coagulation of the blood. The serum-albumin and para-globulin occur in about equal quan- tities. Fibrinogen belongs to the class of globulins, and is the sub- stance which produces the fibrin of coagulated blood. It is very difficult to obtain in the fluid condition, owing to the rapidity with which it solidifies when blood is withdrawn from the circulation. Though it is a most important element in the blood, it occurs in very small quantities. Extractives. — Extractives are substances other than proteins that may be extracted from dried blood by special methods. Sugar in the form of glucose is present under normal condi- tions in the amount of 0.1 to 0.2 per cent. A temporary in- crease in the amount of sugar may follow the ingestion of a large quantity. Fat is found in the plasma in about the same proportion as sugar. It is much more subject to variation, rising notably after a meal in which there was much fat. Waste products found in the plasma represent the end products resulting from the oxidation of our food. Due to the efficiency of the kidneys and supplementary organs of excretion they occur in very small quantities. Salts. — The salts found in the blood amount to about one per cent of the total solids. They are derived from the food and from the chemical reactions going on in the body. The most abundant is sodium chloride. Gases. — OxA'gen, nitrogen, and carbon dioxide gas are found in the blood. Carbon dioxide is the result of oxidation in the ' Albumins and globulins give the same general tests ; they are both coagulated by heat, and the chief difference is in their solubilities. Chap. IX] VASCULAR SYSTEM 149 tissues, and is found in both arterial and venous blood, but the quantity is greater in venous blood. Enzymes. — An enzyme is a substance produced by living cells and is capable of effecting chemical change without itself undergo- ing alteration in the process. Each enzyme has a definite action at a suitable temperature, and will only work in a medium of definite reaction, either acid or alkaline. Further the products of the action must be removed. Five enzymes have been found in the blood. Internal secretions. — The blood serves as a medium to carry internal secretions. (See page 136.) Immune bodies. — In addition to the phagocytes and opsonins, the blood has been found to contain various other protective sub- stances, which are described as antibodies. Just how they are formed, and whether they are a natural constituent of the blood, or whether they are developed only during an attack of disease, are undecided questions. The antibodies, like the enzymes, are specific in their action, that is, each variety will act against only one form of bacterium or toxin ; for instance the antibody for typhoid is of no service against pneumonia. THE CLOTTING OF BLOOD Blood when drawn from the blood-vessels of a living body is perfectly fluid. In a short time it becomes viscid, and this vis- cidity increases rapidly until the whole mass of blood becomes a Fig. 95. — Bowl of Recently Clotted Blood, showing the Whole Mass uniformly Solidified. (Dal- ton.) Fig. 96. — Bowl of Clotted Blood AFTER Twelve Hours, showing the Clot Contracted and Floating in the Fluid Serum. (Dalton.) complete jelly. If the blood in this jelly stage be left untouched in a glass vessel, a few drops of an almost colorless fluid soon make their appearance on the surface of the jelly.- Increasing in number 150 ANATOMY FOR NURSES [Chap. IX and running together, the drops after a while form a superficial layer of pale straw-colored fluid. Later on, similar layers of the same fluid are seen at the sides, and finally at the bottom of the jelly, which, shrunk to a smaller size and of firmer consistency, now forms a clot, floating in a liquid. The upper surface of the clot is generally slightly concave. If a portion of the clot be examined under the microscope, it is seen to consist of a net- work of fine fibrils, in the meshes of which are entangled the red and some of the white corpuscles of the blood. The fibrils are composed of the fibrin ; and the liquid in which the clot is sus- pended is blood minus corpuscles and fibrin, and is called serum. The relation between plasma and serum is shown in the following scheme : — Serum ^, ^ Plasma Blood I Corpuscles Fibrin Clot . The formation of insoluble fibrin from soluble fibrinogen is an instance of enzyme action and is comparable to the clotting of milk under the influence of rennin. When blood leaves the vessels, the blood-plates and some of the white corpuscles luidergo prompt disintegration, and give rise to a substance called prothrombin, which is acted upon by the calcium salts of the plasma and con- verted into thrombin. It is this substance called thrombin which acts upon the fibrinogen and converts it into fibrin. Value of clotting. — This property is of very great im- portance in the arrest of hemorrhage. The clot formed closes the openings of wounded vessels, and the procedures used to check hemorrhage are directed toward hastening the formation of a clot, and stimulating the blood-vessels to contract so that a smaller- sized clot will be sufficient. The coagulability of the blood differs in different individuals, and in rare cases is so slight that the most trivial operation involv- ing hemorrhage is attended with great danger. This condition is known as hemorrhagic diathesis or hemophilia, and is thought to be due to a lack of fil)rinogen or of calcium salts. Conditions affecting clotting. — Clotting is hastened by : — (1) A temperature higher than that of the body, 110-120° F. (2) Contact with any rough surface. (3) Contact with any foreign substance, such as gauze. • Chap. IX] VASCULAR SYSTEM 151 (4) Injury to the walls of the blood-vessels. (5) Rest. It is generally conceded that the first four conditions hasten the disintegration of blood-plates and white corpuscles, and conse- quently the formation of thrombin and of a clot. Many standard text-books include agitation instead of rest. If blood is contained in a vessel, agitation of it does hasten the process of clotting in the same way that the first four conditions do. If, however, we consider the formation of a clot in the open end of an injured vessel, we keep the part at rest, because agitation might dislodge the clot after it had formed. Clotting is hindered by : — (1) A very low temperature. Cold hinders the formation of a clot but is often used to check hemorrhage, because it stimulates the blood-vessels to contract. (2) Contact with living tissues, especially the walls of the blood- vessels. (3) The addition of strong acids or alkalies, neutral salts, oil or other viscid substances, certain organic ferments, or a large quantity of water. (4) Absence of calcium salts. (5) Absence of fibrinogen. (6) Removal of fibrin. If fresh blood, before it has time to clot, be whipped with a bundle of twigs, the fibrin will form on the twigs, and if the whipping of the blood be continued until after the fibrin has been deposited on the twigs, the blood left in the vessel will be found to have lost the power of clotting. Such blood is called defibrinated. Why blood does not clot within the blood-vessels. — Fortunately blood rarely clots within the blood-vessels during life. Why it does not is not known, but two theories are advanced to account for it. (1) Circulating blood does not contain thrombin because the blood-plates and white corpuscles do not disintegrate in sufficient numbers to allow for the formation of it. (2) Circulating blood does contain some thrombin, but it also contains a substance called antithrombin which is secreted by the lining of the heart and blood-vessels. Antithrombin neutralizes or prevents the activity of thrombin. 152 ANATOMY FOR NURSES [Chap. IX Intravascular clotting. — It is well known that clots occasionally form within tlie blood-vessels. The most frequent causes are : — (1) When the internal coat of a blood-vessel is injured, as for instance by a ligature, the endothelial cells are altered and may act as a foreign substance. If in addition there is a stasis of blood at this point, disintegration of the blood-plates and white corpuscles may result in the formation of thrombin and a clot. (2) Any foreign material, even air, that is introduced into the blood and not absorbed may stimulate the formation of thrombin and a clot. Thrombus and embolus. — A clot which forms inside a blood- vessel is called a thrombus. A thrombus may be broken up and disappear, but the danger is that it may be carried to some point in an important vessel where it acts as a wedge, blocks circulation, and may cause instant death. A thrombus that becomes dislodged from its place of formation is called an embolus. Regeneration of the blood after hemorrhage. — A large portion of the total amount of blood in the body may be lost suddenly by hemorrhage without producing a fatal result. It is probable that a healthy individual may recover from the loss of as much as three per cent of the body weight, provided the lost blood is at once replaced by a solution having the same degree of concentration, and containing one or more of the important salts of the blood. Physiological saline solution, ?'. of arterioles. I dilatation J ( Low — Hemorrhage from cut vein " wells up." < _ „ , , ( Presence of valves. Influenced bv n t^ ■ .■ { ' [ Ilospiration. Pressure of finger against large artery. 1. Air pump. , Elastic bag covered with leather cuff. . Merciu-y ma- nometer. f SystoUc or maximum — 110 to 116 mm. I Diastolic or minimum — 65 to 75 mm. Alternate contraction and expansion of artery. ' Facial artery. Temporal artery. Brachial artery. Radial artery. Femoral artery. DorsaUs pedis. Frequency. Strength. Regularity. EquaUty. Tension. Infant, 130 Three years, 100 Adult, 72 Old age, 65 Eating. Aluscular activity. Mental excitement. Age. Sleep. Condition of health. Idiosyncrasies. / Process of transudation. I Process of secretion. Differences in pressure. Muscular movements and valves. I Respiration. Locations where Pulse may be counted Points to note " Pulse Rate Changes in Pulse Rate may be due to Formation Factors con- trolling flow Higher in women than in men. Chap. XII] SUMMARY 231 (Edema Foetal Circulation Accumulation of lymph in tissues. 1. Obstruction to flow of lymph from tissue. May be caused by Changes in Vascular System < at Birth 1. 2. 2. Excessive transudation. Direct communication between right and left auricle by means of foramen ovale. Direct communication between imibilical vein and inferior vena cava. Ductus venosus. Direct communication between pulmonary artery and aorta. Ductus arteriosus. Oxygen and nutritive substances obtained from placenta. Umbilical vein and ductus venosus become obliter- ated. 2. Respiration stimulates pulmonary circulation ; this raises the blood pressure in left auricle, and closes foramen ovale. 3. Ductus arteriosus becomes a fibrous cord. 4. Hypogastric arteries become obliterated. 1. CHAPTER XIII RESPIRATORY SYSTEM: NOSE; LARYNX; TRACHEA; BRONCHI; LUNGS. — RESPIRATION ; ABNORMAL TYPES OF RESPIRATION. MODIFIED RESPIRATORY MOVEMENTS The process of respiration is dependent upon the proper func- tioning of certain organs, which we group together and call a res- piratory system. A respiratory system consists essentially of a moist and permeable membrane, with blood-vessels containing AIR THIN MUCOSA |- |- | . I ^ \ ^ \ — |_ |- CAPILLARV BLOOD VESSEL QD00Q(SC?Xg)O Q QGg)0<50 Q0QO ©gQ Fig. 139. — Diagram of the Essentials of a Respiratory System. (Gerrish.) a high percentage of carbon dioxide on one side, and air or fluid containing a high percentage of oxygen on the other. In most aquatic animals the respiratory organs are external in the form of gills ; in terrestrial, or air-breathing animals, the respiratory organs are situated internally in the form of lungs, and are placed in com- munication with the nose and mouth by means of the bronchi, trachea, and larynx. NOSE The nose is the special organ of the sense of smell, but it also serves as a passageway for the entrance of air to the respiratory organs. It consists of two parts, — the external feature, the nose, and the internal cavities, the nasal fossae. The external nose is composed of a triangular framework of bone and cartilage, covered by skin and lined by mucous membrane. On its under surface are two oval-shaped openings — the nostrils, which are the external openings of the nasal fossse. The margins of the nostrils are provided with a number of stiff hairs, which ar- 232 Chap. XIII] RESPIRATORY SYSTEM 233 rest the passage of dust and other foreign substances carried in with the inspired air. The nasal fossae are two irregularly wedge-shaped cavities, separated from one another by a partition, or septum, the upper part of which consists of the perpendicular plate of the ethmoid, Fig. 140. — Sagittal Section of the Face and Neck, showing the Fibst Portions of the Respiratory and Alimentary Tracts. (Gerrish.) and of the vomer, and the lower part of cartilage. The turbinated bones and turbinated processes of the ethmoid, which are ex- ceedingly light and spongy, project into the nasal cavities, and divide them into three incomplete passages from before back- wards, — the superior, middle, and inferior meatus. The palate and maxillae separate the nasal and mouth cavities, and the crib- riform plate of the ethmoid forms the partition between the cranial and nasal cavities. 234 ANATOMY FOR NURSES [Chap. XIII These cavities ^ communicate with the air in front by the anterior nares, or nostrils, while behind they open into the back of the pharynx by the two posterior nares. The pituitary membrane (sometimes called the Schneiderian ^ membrane) is the mucous lining of the nose. It closely covers the nasal passages, and is thickest and most vascular over the turbinated bones. Advantages of nasal breathing. — Under normal conditions breathing should take place through the nose only (1) because the arrangement of the turbinated bones makes the upper part of the nasal passages very narrow ; (2) these passages are thickly lined, and freely supplied with blood-vessels, so that they can, even in the very coldest weather, moisten and warm the air before it reaches the lungs; and (3) the presence of hairs at the entrance to the nostrils serve as filters. Sinuses which communicate with the nose. — Opening into the nasal cavities are minute channels which connect with (1) the frontal sinuses, (2) the ethmoidal sinuses, (3) the maxillary sinuses or antrums of Highmore, and (4) the sphenoidal sinuses. The pituitary membrane is prolonged into these sinuses, and inflam- matory processes in the nose may extend into these cavities. Mouth and pharynx. — As the mouth and pharynx are more closely associated with the process of digestion rather than respira- tion, they will be described with the digestive organs. The mouth serves as a passageway for the entrance of air, and the pharynx transmits the air from the nose or mouth to the larynx. RESPIRATORY SYSTEM Under this heading we group the organs which are concerned in the process of respiration. In man they are as follows : — 1. Larynx. 3. Bronchi. 2. Trachea. 4. Lungs. 1 Eleven bones enter into the formation of the nasal cavities : the floor is formed by the palate (2) and part of the maxillse bones (2) ; the roof is chiefly formed by the perforated plate of the ethmoid bono (1), the sphenoid (1), and by the (2) small nasal bones ; in the outer walls we find, in addition to processes from other bones, the two scroll-like turbinated bones (2). The vomer (1) forms part of the septum. * It was formerly supposed that the mucus secreted by the mucous membrane of the nose came from the brain. Schneider was the name of the anatomist who first disproved this. Chap. XIII] RESPIRATORY SYSTEM 235 THE LARYNX The larynx is situated between the base of the tongue and the top of the trachea, in the upper and front part of the neck. Above and behind lies the pharynx, which opens into the oesoph- agus, or gullet, and on either side of it lie the great vessels of the neck. In form, the larynx is narrow and rounded below, Fig. 141. — Larynx. Viewed from above. (Gerrish.) where it blends with the trachea, but broad above and shaped somewhat like a triangular box, with flat sides and prominent ridge in front. It is made up of nine pieces of fibro-cartilage, united together by elastic ligaments, and moved by numerous muscles. The three principal cartilages are the cricoid, thyroid, and epiglottis. The cricoid resembles a seal ring with the hoop part in front and the signet part in the back. The thyroid resembles a shield and is the largest. It rests upon the cricoid and con- sists of two square plates, or alse (right and left), which are joined together in front and form by their union the laryngeal promi- nence, called Adam's apple. The upper portion of the hind border of the thyroid is called the superior horn, and the lower portion the inferior horn (see Fig. 143). The epiglottis is shaped like a leaf. The stem is inserted in the notch between the two plates of the thyroid. The larynx is lined throughout 236 ANATOMY FOR NURSES [Chap. XIIl by mucous membrane, which is continuous above with that lining the pharynx, and below with that lining the trachea. The glottis. — Across the middle of the larynx is a transverse partition, formed by two folds of the lining mucous membrane, stretching from side to side, but not quite meeting in the middle line. They thus leave in the middle line a chink, or slit, running from front to back, called the glottis. The glottis is protected by the leaf-shaped lid of fibro-cartilage, called the epiglottis, which shuts down upon the opening during the passage of food or other matters into the oesophagus. The vocal cords. — Embedded in the mu- cous membranes at the edges of the slit are fibrous and elastic lig- a m e n t s , w li i c h strengthen the edges of the glottis and give them elasticity. These ligamentous bands, covered with mucous membrane, are firmly attached at either end to the cartilages of the larynx, and are called the true vocal cords, because they function in the production of the voice. Al)ove the true vocal cords are two false vocal cords, so called because they do not function in the production of the voice. Variations in size of glottis. — The glottis varies in shape and size, according to the action of the muscles upon the laryngeal walls. When the larynx is at rest during quiet breathing, the glottis is V-shaped ; during a deep inspiration it becomes almost Fig. 142. — Tuk Larynx as seen by Means OF THE LaKYNUOSCOPE IN DIFFERENT CONDITIONS OF THE Glottis. A, while singing a high note ; B, in fiuiot breathing ; C, during a deep inspiration. I, ba.se of tongue ; e, upper free edge of epiglottis ; e', cushion of the epiglottis ; ph, part of anterior wall of pharynx ; cv, the true vocal folds ; cvs, the false vocal folds ; ir, the trachea with its rings. Chap. XIII] RESPIRATORY SYSTEM 237 round, while during the production of a high note the edges of the folds approximate so closely as to leave scarcely any open- ing at all. fiiiperior Horn Inferior Horn Fig. 143. — Front View of Cartilages of Larynx. Trachea and Bronchi. Voice. — The vocal cords produce the voice. A blast of air, driven by an expiratory movement out of the lungs, throws the two elastic cords into vibrations. These impart their vibrations to the column of air above them, and so give rise to the sound 238 ANATOMY FOR NURSES [Chap. XIII which we call the voice. The pharynx, mouth, and nasal cavities above the glottis act as resonating cavities, and by alterations in their shape and size, they are ai)le to pick out and emphasize cer- tain j)arts of the tones produced in the larynx. Differences between male and female voice. — At puberty in the male, the larynx enlarges, giving rise to what is commonly called Adam's apple. The increase in the size of the larynx causes an increase in the length of the vocal cords. To this is due the lower pitch of the voice in the male. THE TRACHEA The trachea, or windpipe, is a fibrous and muscular tube. It measures about four and a half inches (112 mm.) in length, and three-quarters of an inch (19 mm.) from side to side. It extends down into the tliorax from the lower part of the larynx to opposite the third thoracic vertebra, where it divides into two tubes, — the two bronchi, — one for eacli lung. The walls are strengthened and rendered more rigid by hoops of cartilage embedded in the fibrous tissue. These hoops are C-shaped and incomplete behind, the cartilaginous rings being completed by bands of plain muscular tissue where the trachea comes in contact with the oesophagus. Like the larynx, it is lined by mucous membrane, and has a ciliated epithelium upon its inner surface. The mucous membrane, which also extends into the bronchial tubes, keeps the internal surface of the air- passages free from impurities ; the sticky mucus entangles par- ticles of dust and other matters breathed in with the air, and the incessant movements of the cilia continually sweep this dirt- laden mucus upward and outward. THE BRONCHI The two bronchi, into which the trachea divides, differ slightly; the right bronchus is shorter, wider, and more nearly horizontal, the left bronchus is longer, narrower, and more nearly vertical. They enter the right and left lung, respectively, and then break up into a great number of smaller branches which are called the bron- chial tubes, or bronchioles. The two bronchi resemble the trachea in structure ; but as the bronchial tubes divide and subdivide Chap. XIII] RESPIRATORY SYSTEM 239 their walls become thinner, the small plates of cartilage cease, the fibrous tissue disappears, and the finer tubes are composed of only a thin layer of muscular and elastic tissue lined by mucous membrane. LUNGS The lungs are cone-shaped organs which occupy almost all of the cavity of the thorax that is not taken up by the heart, the large blood-vessels, the lymphatics, and the oesophagus. Each lung RIGHT LUNG LEFT LUNG Fig. 144. — Bronchi and Bronchioles. The lungs have been widely sepa- rated and tissue cut away to expose the air-tubes. (Gerrish.) presents an outer surface which is convex, a base which is concave to fit over the convex portion of the diaphragm, and a summit or apex which rises half an inch above the clavicle. On the inner surface is a vertical notch called the hilum, which gives passage to the bronchi, blood-vessels, lymph-vessels, and nerves. The right lung is the larger and heavier ; it is broader than the left, owing to the inclination of the heart to the left side ; it is also shorter by one inch, in consequence of the diaphragm rising 240 ANATOMY FOR NURSES [Chap. XIII higher on the right side to accommodate the liver. The right lung is divided by fissures into three lobes, upper, middle, and lower. The left lung is smaller, narrower, and longer than the right. It is only divided into two lobes, upper and lower. The front border is deeply notched to accommodate the heart. Anatomy of the lungs. — The lungs are hollow, rather spongy organs, and consist of the bronchial tubes and their terminal dilatations, numerous blood-vessels, lymphatics, nerves, and an abundance of fine, elastic connective tissue, binding all together. (See Fig. 99.) Each lobe of the lung is composed of many lobules, and into each lobule a bronchiole enters and terminates in an enlargement having more or less the shape of a funnel, and called an infundibulum. From each infundibulum there is a series of small sac-like j)rojections known as alveoli, the walls of which are honeycombed with cavities called the air-cells. In this way the amount of surface exposed to the air and covered by the capillaries is immensely increased. Blood-vessels of the lungs. — Two sets of vessels are distrib- uted to the lungs: (1) the branches of the pulmonary artery, and (2) the branches of the bronchial arteries. (1) The branches of the pulmonary artery accompany the bronchial tubes and form a plexus of capillaries around the al- veoli. The walls of the bronchioles consist of a single layer of flattened epithelioid cells, surrounded by a fine, elastic connec- tive tissue, and are exceedingly thin and delicate. Immediately beneath the layer of flat cells, and lodged in the elastic connective tissue, is this very close plexus of capillary blood-vessels ; and the air reaching the alveoli by the bronchial tubes is separated from the blood in the capillaries by only the thin membranes forming their respective walls. The pulmonary veins begin at the margin of the alveoli and return the blood distributed by the pulmonary artery. (2) The branches of the bronchial arteries supply blood to the lung substance, — the bronchial tubes, coats of the blood- vessels, the hmph nodes, and the pleura. The bronchial veins return the blood distributed by the bronchial arteries. Nerves. — The substance of the lungs is supplied with nerves which are derived from the s.Mnpathetic system, and from branches ,-n//^; t —Diagram of a Lobule of the Lung. A bronchiole is seen divid- ing nto two branches, one of which runs upward and ends in the lobule. la IVvpoh" 'l'\ ^'""^u °^ i^f^'^dibula. At the left are two infundibula. the aiveoh of which presen their outer surfaces. Next are three infundibula in ver- next Jrourihe fir 7'" ' "if^'f °Pf ^"^ '''*° *^" "°°^™°^ passageway. In the nnpn,-n f I ^ "^^"ndibulum shows a pulmonary arteriole surrounding the cC n. I f ^'^°/".«- and the second gives the same with the addition of the close capillary network in the wall of each alveolus. Around the fourth group is a deep deposit of pigment, such as occurs in old age, and in the lungs of those who "rtet n.h et'f — *'l/''t °!! *^^ '^'•'^'^'^^^^'^ ^-^ - ^--h of "the pulmonar^ artery (blue), bringing blood to the infundibula for aeration. Beginning between the infundibula are the radicles of the pulmonary vein (red), a root of which ^ea nutrient blood to the bronchiole. (Gerrish.) R 241 242 ANATOMY FOR NURSES [Chap. XIII of the pneumogastric. These nerves follow the course of the blood-vessels and bronchioles. Pleura. — Each lung is enclosed in a serous sac, the pleura, one layer of which is closely adherent to the walls of the chest and dia])hragni (parietal) ; the other closely covers the lung (visceral). The two layers of the pleural sacs, moistened by serum, are normally in close contact ; they move easily upon one another, and prevent the friction that would otherwise occur between the lungs and the walls of the chest with every respiration. Inflammation of the pleura is called pleurisy. Mediastinum. — The mediastinum is the space between the two pleural sacs. It extends from the sternum to the spinal column and holds a portion of many organs, i.e. the trachea, oesophagus, great vessels connected with the heart, ner^'es, and the thoracic duct. RESPIRATION Function. — The main purpose of respiration is to supply the body with oxygen and get rid of the excess carbon dioxide which results from oxidation. It also helps to equalize the temperature of the body and get rid of excess of water. To accomplish these purjioses two processes are necessary, i.e. external and internal respiration. External respiration. — This takes place in the lungs and con- sists of the absorption of oxygen from the air in the alveoli, and the elimination of some of the carbon dioxide and water from the blood in the capillaries. External respiration consists of inspira- tion, or the process of taking air into the lungs, and expiration, or the process of expelling air from the lungs. Internal respiration. — This takes place in the cells and consists of the diffusion of oxygen from the blood in the capillaries into the tissues, and its union there with the protoplasm of the cells. As a result of this union or oxidation complex bodies are broken up into simpler ones, such as carbon dioxide and water, and there is thus liberated a great deal of energy, which is mani- fested in the increasing of muscular activity and in the pro- duction of heat. The carbon dioxide passes by diffusion into the venous blood, and is carried by it to the right side of the heart and thence to the lungs, a certain quantity, however, escaping from the blood through the kidneys and skin. Chap. XIII] RESPIRATORY SYSTEM 243 Mechanism of inspiration and expiration. — During inspiration the cavity of the chest is enlarged in all three diameters : (1) antero-postepior, (2) lateral, and (3) vertical. This is brought about by the action of the intercostal and other muscles, which elevate the ribs and thereby increase the antero-posterior and lateral diameters. The descent of the diaphragm increases the vertical diameter. The lungs are correspondingly distended to fill the enlarged cavity. To prevent a vacuum in the lungs, air rushes in by way of the trachea to the bronchi. Upon the relaxa- tion of the inspiratory muscles, the elasticity of the lungs and the weight and elasticity of the chest walls cause the chest to return to its original size, in consequence of which the air is expelled from the lungs. As in the heart, the auricular systole, the ventricular systole, and then a pause follow in regular order, so in the lungs the inspiration, the expiration, and then a pause succeed one another. Control of respiration. — Respiration is both a voluntary and an involuntary act. It is possible for a short time to increase or retard the rate of respiration within certain limits by voluntary effort, but this cannot be done continuously. If we intentionally arrest the breathing or diminish its frequency, after a short time the nervous impulse becomes too strong to be controlled, and the movements will recommence, as usual. If, on the other hand, we purposely accelerate respiration to any great degree, the exertion soon becomes too fatiguing for continuance, and the movements return to their normal standard. Cause of respiration. — The nervous impulses which cause the contractions of the respiratory muscles are entirely dependent on the nervous system, especially that part known as the respiratory centre, which is located in the medulla oblongata. Efferent nerves from the respiratory centre travel down the spinal cord and end at different levels, where they connect with the fibres of the pneu- mogastric and sympathetic nerves that are distributed in the lung tissue. Afferent nerves lead from these different levels to the res- piratory centre. The consensus of opinion at the present time seems to be that the action of the respiratory centre is automatic, but that the rate and rhythm of the respiratory movements is controlled (1) by the pneumogastric nerve, and (2) by the chemical condition of the blood. 244 ANATOMY FOR NURSES [Chap. XIII (1) The fibres from the pneumogastric nerve are of two kinds : (a) inspiratory fibres which tend to increase the rate of respiration, and (6) expiratory fibres which check the action of the inspiratory set. The inspiratory fibres are stimulated to action when the lung collapses ; the expiratory when the lung expands. (2) The respiratory centre shows a specific irritabihty for carbon dioxide, and an increased amount of carbon dioxide in the blood acts as a stimulus, increasing the rate and depth of the respirations, so that the lungs are more thoroughly ventilated. Increased activ- ity, or any abnormal condition that increases the oxidation of the tissues, naturally results in an increased production of carbon dioxide, and an increase in the rate and depth of the respirations. On the other hand, an excess of oxA'gen in the blood may cause a condition known as physiological apncea, i.e. where the blood is so rich in oxj'gen and poor in carbon dioxide that a respiratory act is unnecessary. Reflex stimulation of the respiratory centre. — Every one must have noticed that the respiratory movements are affected by stimulation of the sensory nerves. Strong emotion, sudden pain, or a dash of cold water on the skin produce changes in the rate of the respirations. It is assumed, therefore, that the respiratory centre is in connection with the sensory fibres of all the cranial and spinal nerves. Cause of the first respiration. — The immediate cause of the first respiratory effort is closely connected with the cause of the activity of the respiratory centre during life. The stimulus is supposed to come from (1) the increased amount of carbon dioxide in the blood, due to the cutting of the cord ; and (2) the sensory nerves of the skin, due to cooler air, handling, etc. During intrauterine life the foetus receives its supply of oxj'gen from the blood-vessels of the umbilical cord, which connect with the placenta. The lungs are in a collapsed condition and contain no air. The walls of the air-sacs are in close contact, and the walls of the smaller bronchial tubes, or bronchioles, touch one another When the chest ex-pands with the first breath taken, the inspired air has to overcome the adhesions existing between the walls of the bronchioles and air-sacs. The force of this first inspiratory effort, spent in opening out and unfolding, as it were, the inner recesses of the lungs, is considerable. In the succeeding expiration, most of Chap. XIII] RESPIRATORY SYSTEM 245 the air introduced by the first inspiration remains in the lungs, suc- ceeding breaths unfold the lungs more and more, until finally the air-sacs and bronchioles are all opened up and filled with air. The lungs thus once filled with air are never completely emptied again until after death. Frequency of respiration. — Each respiratory act in the adult is ordinarily repeated about eighteen times per minute. This rate may be increased by muscular exercise, emotion, etc. Any- thing that affects the heart-beat will have a similar effect on the respirations. The ratio to the pulse is about 1 to 4 in health. Age has a marked influence. The average rate in the newly born infant has been found to be forty-four per minute, and at the age of five years, twenty-six per minute. It is reduced between the ages of fifteen and twenty to the normal standard. Respiratory sounds. — The entry and exit of the air are ac- companied by respiratory sounds or murmurs. These murmurs differ as the air passes through the trachea, the larger bronchial tubes, and the bronchioles. They are variously modified in lung disease, and are then often spoken of under the name of " rales." In labored breathing the contraction of the respiratory muscles not usually brought into play, such as the muscles of the throat and nostrils, becomes very marked. Effects of respiration upon the blood. — While the blood is passing through the pulmonary capillaries, the following changes take place : (1) it loses carbon dioxide ; (2) it gains oxygen, which combines with the reduced haemoglobin of the red corpuscles and turns it into oxyhsemoglobin, and as a result of this the crim- son color shifts to scarlet ; (3) the temperature is slightly reduced. Capacity of the lungs. — As the lungs are not emptied at each expiration, neither are they filled. If filled to their utmost, they can hold a little more than one gallon (4500 c.c.) of air. This total is divided as follows : — (1) Tidal. (3) Reserve. (2) Complementary. (4) Residual. Tidal air is the air introduced with every ordinary inspira tion. Complementary air is the excess over the tidal air which may be introduced during a forced inspiration. 246 ANATOMY FOR NURSES [Ch.\p. XII 1 Reserve air is the amount of air in addition to the tidal air one can expel from the lungs in a forced expiration. Residual air is the air remaining in the lungs after the most powertul cxi)iration. The vital capacity is the sum of the tidal, complementary, and reserve airs added together. It equals about 225 cubic inches (3700 cc). It is not correct to think of the residual air in the lungs as stationary, for the air is being constantly moved and renewed. This movement is maintained by: (1) the alternate expansion and collapse of the lungs in respiration, (2) the convection currents due to the differences in temperature between the inspired air and the residual air, (3) the pulsation of the arteries, and (4) the difference in the proportion of carbon dioxide and ox^'gen in the inspired air and residual air. This fourth factor is also responsible for the interchange of gases between the air in the air-sacs and the blood in the capillaries. The reason is that the blood contains more carbon dioxide and less oxygen than the air in the alveoli, and the tendency of gases is always to mix in uniform proportions. The effects of respiration upon the air outside the body. — AYith every inspiration a well-grown man takes into his lungs about 30 cubic inches (500 cc.) of air. The air he takes in differs from the air he gives out mainly in three particulars : — 1. ^Vhatever the temperature of the external air, the expired air is nearly as hot as the blood ; namely, of a temperature between 98° and 100° F. (36.7 and 37.8° C). 2. However dry the external air may be, the expired air is quite, or nearly, saturated with moisture. 3. The air when breathed loses about one-fourth of its ox\'gen and increases the carbon dioxide an hundred fold; the quantity of nitrogen is changed little, if any. To be exact, the air loses 4.94 volumes of oxygen and gains 4.38 volumes of carbon dioxide. Thus : — Inspired air Expired air Oxygen Carbon Dioxide Nitrogen 20.96 16.02 4.94 loss 0.04 4.38 4.34 gain 79 79 0 Chap. XIII] RESPIRATORY SYSTEM 247 In addition the expired air contains a certain amount of organic matter which comes principally from the mouth and particles of food left in the mouth. Ventilation. — Since at every breath the external air loses ox;y'gen, gains carbon dioxide, and a certain amount of organic matter, it was formerly taught that the general discomfort, headache, and languor that result from staying in a badly ventilated room were due to the increase in carbon dioxide, and the poisonous effects of the organic matter. The results of many experiments seem to prove that people can become so accustomed to a low percentage of oxygen and a high percentage of carbon dioxide that they suffer little discomfort, and the organic matter is not poisonous, though when present in any amount it causes disagreeable odors and makes the air stuffy. It is now thought that the injurious effects of remaining in a badly ventilated room are due to inter- ference with the heat-regulating mechanism of the body. The air is heated to a high temperature and becomes saturated with watery vapor. Both of these conditions prevent loss of heat from the body and produce a fever temperature. Even when these condi- tions exist it has been found that moving the air, i.e. keeping it in circulation even without renewing it, has a stimulating effect and lessens discomfort. Because of these facts we are now taught that the maintenance of proper air conditions must be based (1) on the normal composition of the air as regards ox;^^gen and carbon dioxide, (2) on the temperature, and (3) on the degree of humid- ity. Any system of ventilation that is based solely on the first condition, and neglects to take into account the second and third is sure to prove unsatisfactory. ABNORMAL TYPES OF RESPIRATION Dyspnoea. — The word dyspnoea means difficult breathing. It is caused by (1) an increase in the percentage of carbon dioxide in the blood, (2) a decrease in the ox;\^gen, and (3) any condition that stimulates the sensory nerves and causes pain in the lungs. Hyperpnoea. — The word hyperpnoea means excessive breathing and is applied to the initial stages of dyspnoea, when the respira- tions are simply increased. Apnoea. — The word apnoea means a lack of breathing. 248 ANATOMY FOR NURSES [Chap. XIII Chejme-Stokes Respirations. — This is a type of respirations which was first described by the two physicians whose names it bears. It appears in two forms: (1) the respirations increase in force and frequency up to a certain point, and then gradually de- crease until they cease altogether, and there is a short period of Fig. 146. — Stethograph Tracing of Cheyne-Stokes Respirations in a Man. The time is marked in seconds. (Halliburton.) apnoea, then the respirations recommence and the cycle is repeated. (2) The respirations increase in force and frequency up to a certain point, then cease, and the period of apnoea intervenes, without the gradual cessation of the respirations. This condition is asso- ciated with disease of the kidney, brain, or heart. The cause is not settled, but it is of bad prognosis and generally indicates a fatal termination. (Edematous Respiration. — When the air cells become in- filtrated with fluid from the blood, the breathing becomes oedema- tous and is recognized by the moist, rattling sounds, called rales, that accompany each inspiration. It is a serious condition because it interferes with aeration of the blood and often results in asphyxia. Asphyxia. — This condition is usually the sequel to severe dysp- noea and oedematous respiration. It is produced by any condition that causes prolonged interference with the aeration of the blood. After death from asph\ocia it will be found that the right side of the heart, the ])ulmonary arteries and the systemic veins are over- loaded, and the left side of the heart, the pulmonary veins, and the systemic arteries are empty. Chap. XIII] RESPIRATORY SYSTEM 249 MODIFIED RESPIRATORY MOVEMENTS Various emotions may be expressed by means of the respira- tory apparatus. Sighing is a deep and long-drawn inspiration, followed by a sudden expiration. Yawning is an inspiration, deeper and longer continued than a sigh, drawn through the widely open mouth, and accompanied by a peculiar depression of the lower jaw. Hiccough is caused by a sudden iiispiratory contraction of the diaphragm; the glottis suddenly closes and cuts off the column of air just entering, which, striking upon the closed glottis, gives rise to the characteristic sound. Sobbing is a series of convulsive inspirations during which the glottis is closed, so that little or no air enters the chest. Coughing consists, in the first place, of a deep and long-drawn inspiration by which the lungs are well filled with air. This is followed by a complete closure of the glottis, and then comes a forcible and sudden expiration, in the midst of which the glottis suddenly opens, and thus a blast of air is driven through the upper respiratory passages. Sneezing consists of a deep inspiration, followed by a sudden and forced expiration, which directs the air through the nasal passages. Laughing consists essentially in an inspiration, followed by a whole series of short, spasmodic expirations, the glottis being freely open during the whole time, and the vocal cords being thrown into characteristic vibrations. Crying consists of the same respiratory movements as laugh- ing; the rhythm and the accompanying facial expressions are, however, different, though laughing and crying often become indistinguishable. Speaking consists of a voluntary expiration and the vibration of the vocal cords as the air passes over them. 250 ANATOMY FOR NURSES [Chap XIII Respiration is dependent upon prise the respiratory system, these organs. Function External nose Nose Respiratory System Larynx Internal cavities, or ' nasal fossae SUMMARY the proper functioning of organs that corn- Air passes through the nose or mouth to Special organ of the sense of smell. Passageway for entrance of air to the respiratory organs. Framework of bone (nasal) and cartilage. Covered with skin, hned with mucous membrane known as pituitary, or Schneiderian. Xostrils are oval-shaped openings on under siu-face, separated by a partition. Extend from nostrils to the pharjTix. Two wedge-shaped ca\'ities. ' 2 palate. 2 maxillae. 1 ethmoid. 1 sphenoid. 2 nasal. Formed bv < 2 turbinated, and pro- cesses of - the eth moid Superior meatus. Middle meatus. Inferior meatus. Advantages of nasal breathing Communicat- ing sinuses JL^ vomer. 11 bones, r Warmed. Air < ^Moistened. [ Fihered. 1. Frontal. 2. Ethmoidal. 3. Maxillar}' or Antrums of Highmore. 4. Sphenoidal. 1. Larj'nx. 3. Bronchi. 2. Trachea. 4. Lungs. Triangular box made up of nine pieces of cartilage. Situated between the tongue and trachea. Contains vocal cords. SUt or opening between cords called glottis, which is pro- tected by leaf-shaped lid called epiglottis. Connected with external f Mouth, air by I Nose. Chap. XIII] SUMMARY 251 Voice . Trachea Bronchi Lungs Produced by vibrations of vocal cords. ( Pharynx. Resonating cavities < Mouth. I Nasal cavities. Lower pitch of male voice is due to greater length of vocal cords. Fibrous and muscular tube, 4^ in. long. Strengthened by C-shaped f Complete in front, hoops of cartilage I Incomplete behind. In front of oesophagus. Extends from larynx to third thoracic vertebra, where it divides into two bronchi. Right and left — structure similar to trachea. r 1 in. long. Right I f in. wide. I Almost horizontal. [■ 2 in. long. Left < f in. wide. I Almost vertical. Divide into innumerable bronchial tubes or bronchioles. Location — Occupy all of the cavity of the thorax that is not taken up by the heart, blood-vessels, lymphatics, and oesophagus. Outer surface convex to fit in concave cavity. Base concave to fit over convex diaphragm. > Apex rises half an inch above the clavicle. Hilum or depression on inner surface gives passage to bronchi, blood-vessels, IjTiiphatics, and nerves, f Three lobes — larger, heavier, broader, I shorter. / Two lobes — smaller, narrower, longer, I front border deeply indented. ' Hollow, spongy organs. Consist of bron- chial tubes — infundibula — alveoli, also blood-vessels, lymphatics, and nerves held together by connective tissues. Blood for aeration. Accompany bronchial tubes. Pulmonary J Plexus of capillaries around artery alveoli. Returned by pulmonary veins. Bronchial arteries — supply lung substance. 1. Branches from the sympathetic system. 2. Branches from the pneumogastric. Cone-shaped organs Right Left Anatomy Blood-vessels Nerves 252 ANATOMY FOR NURSES [Chap. XIII PleuTi Mediastinum Closed sac. Envelops lungs, but they are not in it. Two layers (■ Visceral — next to lung V1&- 1 Moistened 1 by serum. Respiration Ftmction Mechanism of Inspira- tion and Expiration < Parietal — outside of I ceral Function — To lessen friction. ■ Space between pleural sacs. Extends from sternum to spinal column. Increase the amount of oxj^gen. Decrease the amount of carbon dioxide. Help to maintain temperature. Help to eliminate waste. Absorption of oxygen from air by circulate* ing blood in the lungs. Absorption of carbon dioxide from circu- lating blood by the air in the air sacs. Inspiration — Process of taking air into lungs. Expiration — Process of expelling air from lungs. Absorption of oxygen from the blood by all the cells of the body. Absorption of carbon dioxide from all the cells by the blood. of External Internal Inspiration Chest cavity enlarged ' Elevation ribs. Descent of diaphragm. Cause of Respiration Expiration Chest cavity made smaller Lungs expand. Air rushes in through trachea and bronchi. Inspiratory muscles re- lax. Recoil of elas- tic thorax. Recoil of elas- tic lungs. Air forced out through trachea. 1 . Respiratory centre — Action is automatic. Assumed to be in eonnection with all the cranial and spinal nerves. 2. Pneumogastric nerves. 3. Sympathetic nerves. ' Inspiratory — tend Rate and rhythm controlled by Pneumogastric ^ nerves to increase rate. Expiratory — check the action of the inspiratory set. Carbon dioxide content of blood. Chap. XIII] SUMMARY 253 Cause of First Respi- ration Respiratory Rate Effect of Respiration upon the Blood Capacity of Lungs Movement of Residual Air maintained by Effect of Respiration upon the Air outside the Body Proper Ven- tilation ' 1. Increased amount of carbon dioxide due to cutting of the cord. 2. Reflex, due to stimulation of the sensory nerves of the skin. IS times per minute. Ratio to pulse 1 to 4. Influenced by Muscular exercise. Emotion. Heart-beat. I Age. 1. Loses carbon dioxide. _, „ . [ Oxyhaemoglobin. 2. Gams oxvgen i „ , ^ , ' I Scarlet color. 3. Temperature is slightly reduced. r Tidal A little more than 1 gallon of air ■ (4500 c.c.) Complemen- tary Reserve Residual ► Vital capacity 3700 c.c. Abnormal Types ' 1. Alternate expansion and collapse of lungs. 2. Convection currents. 3. Pulsation of the arteries. 4. Diffusion of gases. 1 . Temperature increased. Expired air is as hot as blood. 2. Moisture increased. Expired air is saturated with moisture. 3. Oxygen decreased by 4.94 parts in a hundred. 4. Carbon dioxide increased by 4.38 parts in a hundred. 5. Organic matter gained. 1. Composition of air as regards oxygen and carbon dioxide. 2. Proper temperature. 3. Degree of humidity. ' Dyspnoea — difficult breathing. Hyperpnoea — excessive breathing. Apnoea — lack of breathing. 1. Respirations increase in force ana frequency, then gradually de- crease and stop. Cycle re- - Cheyne-Stokes \ peated. . Respirations increase in force and frequency up to a certain point, then stop. Cycle repeated. (Edematous — air cells filled with fluid, hence moist, rattling sounds. Asphyxia — oxygen starvation. CHAPTER XIV THE DIGESTIVE SYSTEM: ALIMENTARY CANAL AND ACCESSORY ORGANS Digestion is the process by means of wliich the food we take into our mouths is transformed into a condition of solution or emulsion suitable for absorption into the blood. The organs in which the food is contained while undergoing digestion as well as the organs which assist in the process are grouped together and called the digestive system. THE DIGESTIVE SYSTEM The digestive system consists of the alimentary canal and the accessory organs : (1) the salivary glands, (2) the tongue, (3) the teeth, (4) the pancreas, and (5) the liver. ALIMENTARY CANAL The alimentary canal is a musculo-membranous tube extending from the mouth to the anus. It is about twenty-eight feet long and the greater part of it is coiled up in the cavity of the abdomen. The diameter of the tube is by no means uniform, being consider- ably dilated in certain parts of its course. It is composed of three coats, the serous coat being absent from the mouth, to where it passes through the diaphragm, and of four coats in the abdominal cavity. These coats are : — (1) The mucous j Both described (2) The areolar, or sub-mucous [ in Chapter VIII. (3) The muscular coat is composed for the most part of un- striped muscular fibres, the layers of which are disposed in various ways, the most general arrangement being in a longitudinal and circular direction. By the alternate contraction and relaxation of fibres arranged in this fashion (the contractions starting from above), the contents of the tube are propelled from above dowTi- ward. 254 Chap. XIV] THE DIGESTIVE SYSTEM 255 (4) The serous coat is derived from the peritoneum. The peritoneum. — This is a double membrane, the outer or parietal layer of which lines the inner surface of the abdominal and pelvic cavities, and the inner or visceral layer is reflected back over the contained organs. The arrangement of the peritoneum is very complex, for several elongated sacs and double folds extend from it, to pass in between and either wholly or partially surround the viscera of the abdomen and pelvis. One important fold is the omentum, which hangs like a curtain in front of the stomach and the intestines ; another is the mesentery, which surrounds the greater part of the small intestine. The posterior portion of the mesentery is gathered into folds which are attached to the spine and serve to hold the intestines in place. Functions of the peritoneum. — Like all serous membranes the peritoneum serves to prevent friction between contiguous organs by secreting serum which acts as a lubricant. It also serves to hold the abdominal and pelvic organs in position, to unite and separate these organs, and supports numerous nerves and blood- vessels. The omentum usually contains fat, and, in addition to the usual functions, serves to keep the organs it covers warm. Divisions of the alimentary canal. — For convenience of descrip- tion, the alimentary canal may be divided into : — Mouth, containing tonsils, tongue, salivary glands, and teeth. Pharynx. (Esophagus. Stomach. r Duodenum. Small or thin intestine < Jejunum. [ Ileum. f Caecum. Large or thick intestine • f Ascending. Colon \ Transverse. i Descending. Rectum. MOUTH, OR BUCCAL CAVITY The mouth is a nearly oval-shaped cavity with a fixed roof anteriorly, a flexible roof posteriorly, and a movable floor. It 256 ANATOMY FOR NURSES [Chap. XIV is bounded in front l)y the lips, on the sides by the cheeks, below by the tongue, and above by the palate. The palate. — The palate consists of a hard portion in front formed by bone, covered by mucous membrane, and of a soft portion behind containing no bone. The hard palate forms the partition between the mouth and nose ; the soft palate arches backward and hangs like a curtain between the mouth and the pharynx. Hanging from the middle of its lower border is a pointed portion of the soft palate called the uvula (little grape). Palatine arches. — From the base of the uvula on either side there passes a curved fold of muscular tissue covered by mucous membrane, which shortly after leaving the uvula is, as it were, split into two pillars, the ^% one gcung outward, down- I % ward, and forward, passing to the side of the tongue, the other outward, down- ward, and backward to the side of the pharynx. These pillars are known respec- tively as the anterior and the posterior pillars of the fauces. Tonsils. — In the lower part of the triangular space between the anterior and posterior pillars on either side lie the small masses of lymphoid tissue called ton- sils. They consist of a col- lection of lymph nodules held together by a distinct capsule and covered on their ex-posed surface by mucous membrane. Function. — The function of the tonsils is imperfectly under- stood. They may be a source of lymphocytes and leucocytes, or they may act as filters and prevent the entrance of microorgan- isms. Inflammation of the tonsils is called tonsillitis. Fig. 147. — The Soft P.\late and Tonsillar Regions. (Gcrrish.) Chap. XIV] THE DIGESTIVE SYSTEM 257 The palate, uvula, palatine arches, and tonsils are plainly seen if the mouth is widely opened and the tongue depressed. The fauces is the name given to the aperture leading from the mouth into the pharynx, or throat cavity. The tongue. — The tongue ^ is the special organ of the sense of taste and assists in speech. It has also to be considered with ref- erence to digestion, (1) because stimulation of the nerves of the sense of taste start the secretion of digestive juices, (2) it assists in swallowing, and (3) the follicles at the back of the tongue secrete mucus, which lubricates the food and makes swallowing easier. The salivary glands. — The mucous membrane lining the mouth contains many minute glands consisting of just one cell. These are called goblet cells and pour their secretion upon its surface, but the chief secretion of the mouth is supplied by the salivary glands, which are three pairs of com- pound saccular glands called the parotid, sub- maxillary, and sub- lingual, respectively. Each parotid gland is placed just under and in front of the ear ; its duct passes forward along the cheek, until it opens into the in- terior of the mouth opposite the second molar tooth of the upper jaw. The submaxillary and sublingual glands are situ- ated below the jaw and under the tongue, the submaxillary being placed further back than the sublingual. Their ducts open in the floor of the mouth beneath the tongue. The secretion of these salivary glands, mixed with that of the small glands of the mouth, is called saliva. The teeth. — The semicircular borders of the upper and lower Fig. 148. — The Salivary Glands. ' A detailed description of the tongue will be found in Chapter XX. B 258 ANATOMY FOR NURSES [Chap. XIV jaw-bones (the alveolar processes) contain sockets for the recep- tion of the teeth. A dense insensitive fibrous membrane covered by smooth mucous membrane — the gums — covers these pro- cesses and extends a little way into each socket. These sockets are lined by periosteum, which connects with the gums and serves POLP-CAVITY \ Fig. 149. — Section cf Hu.\ian Molar Tooth. Magnified. (Dalton.) (1) to attach the teeth to their sockets, and (2) as a source of nour- ishment. Each tooth consists of three portions: (1) the root, consisting of one or more fangs contained in the socket ; (2) the crotvn, which projects beyond the level of the gums; and (3) the neck or constricted portion between the root and the crown, which is enveloped by the gum. Each tooth is composed principally of dentine, which gives it shape and encloses a cavity, the pulp cavity. The dentine of the crown is capped with a dense layer of enamel. The dentine of the root is covered by cement. These three substances, enamel, dentine, and cement, are all harder than bone, enamel being the hardest substance found in the body. They are developed from epithelial tissue. The pulp cavity is just under the crown and Chap. XIV] THE DIGESTIVE SYSTEM 259 is continuous with a canal that traverses the centre of each root, and opens by a small aperture at its extremity. It is filled with dental pulp, which consists of loose connective tissue holding a number of blood-vessels and nerves which enter by means of the canal from the root. There are two sets of teeth developed during life : the first, temporary or deciduous ; and the second, permanent. Temporary teeth. — In the first set are twenty teeth, ten in each jaw. The cutting of the temporary teeth begins usually at seven months and ends at about the age of two and one-half years. ^ Permanent teeth. — In the second set are thirty-two permanent teeth, sixteen in each jaw. During childhood the temporary teeth are replaced by the permanent. The first molar usually appears at six years of age. According to their shape and use the teeth are divided into incisors, canines, premolars, and molars. Right Middle Left Molar Premolar Canine Incisor Canine Premolar Molar Upper ... 3 2 1 4 1 2 3 Lower ... 3 2 1 4 1 2 3 (ColHns.) Incisors are eight in number and form the four front teeth of each jaw. They have wide, sharp edges, and are specially adapted for cutting food. Canines are four in number, two in each jaw. The upper canines are commonly called eye-teeth, the lower, stomach teeth. They have a sharp, pointed edge and are longer than the incisors. In the human animal they serve the same purpose as the incisors. Premolars (or bicuspids) are eight in number in the permanent set, but there are none in the temporary set. There are four in each jaw, two being placed just behind each of the canine teeth. They are broad, with two points or cusps on each crown ; these teeth have only one root, the root, however, being more or less completely divided into two. Their function is to cut and grind food. ' The temporary teeth are usually cut in the following order, the teeth of each group appearing first in the lower jaw : central incisors, 7th month ; lateral inci- sors, 7th to 10th month ; front molars, 12th to 14th month ; canine, 14th to 20th month ; back molars, 18th to 30th month. 260 ANATOMY FOR NURSES [Chap. XIV Molars are twelve in number in the permanent set, but there are only eight in the temporary set. The molars, or true grinders, have broad crowns with small, pointed projections, which make them well fitted for crushing and bruising the food : they each have two or three roots. The twelve molars do not replace the temporary teeth, but are gradually added with the growth of the jaws ; the last or hindermost molars may not appear until twenty-one years of age; hence called " late teeth " or " wisdom teeth." Function. — The teeth assist in the process of mastication by cutting and grinding the food. THE PHARYNX The pharynx, or throat cavity, is a musculo-membranous bag shaped somewhat like a funnel, with its broad end turned upward, and its constricted end downward to end in the oesophagus. It is about four and a half inches (113 mm.) long, and lies behind the nose and mouth. Above, it is attached to the base of the skull, and behind, to the cervical vertebrae ; in front and on each side are apertures which communicate with the nose, ears, mouth, and larynx. Of these apertures there are seven : — Two in front above, leading into the back of the nose, the posterior nares. Two, one on either side above, leading into the Eustachian tubes, which communicate with the ears. One midway in front, the fauces. Two below, one opening into the larynx and the other into the oesophagus. The mucous membrane lining the pharynx is well supplied with glands, and at the back of the cavity there is a con- siderable mass of lymphoid tissue. During infancy and child- hood this may increase to such an extent that it interferes with nasal breathing. The child is then said to have adenoids and is obliged to breathe through the mouth ; hence the term " mouth breathers." Function. — The muscular tissue in the walls of the pharynx is of the striped variety, and when the act of swallowing is about to Chap. XIV] THE DIGESTIVE SYSTEM 261 be performed, the muscles draw the pharyngeal bag upward and dilate it to receive the food ; they then relax, the bag sinks, and the other muscles contracting upon the food, it is pressed down- ward and onward into the oesophagus. THE (ESOPHAGUS, OR GULLET The oesophagus is a comparatively straight tube, about nine inches (225 mm.) long, which commences at the lower end of the pharynx, behind the trachea. It descends in front of the spine, passes through the diaphragm, and terminates in the upper or cardiac end of the stomach. Structure. — The walls of the oesophagus are composed of three coats : (1) an external or muscular, (2) a middle or areolar, and (3) an internal or mucous, coat. The fibres of the muscular coat are arranged in an external longitudinal and in an internal circular layer. Contraction of the outer layer produces dilatation of the tube; contraction of the inner, constriction. Consequently this arrangement is of importance in the movements which carry the food from the pharynx to the stomach. These movements are called peristaltic and consist of contraction of the longitudinal fibres, followed by contraction of the circular fibres. The areolar coat serves to connect the muscular and mucous coats. The mucous membrane is disposed in longitudinal folds which disap- pear upon distention of the tube. Function. — The oesophagus serves (1) to connect the pharynx with the stomach, and (2) to receive the food from the pharynx and by a series of peristaltic contractions pass it on to the stomach. Regions of the abdomen. — That portion of the alimentary canal which is below the thorax is contained in the abdomen. For convenience of description, the abdomen may be artificially divided into nine regions by drawing the following arbitrary lines : — 1. Draw a circular line around the body at the level of the tenth costal cartilages. 2. Draw another circular line at the level of the anterior superior spines of the ilia. 3. Draw a vertical line on each side from the centre of Poupart's ligament upward. 262 ANATOMY FOR NURSES [Chap. XIV These lines are to be eonsidered as edges of planes which divide the abdomen into the following regions as per illustration. HIGHEST LEVEt OF ILIAC CRESr ANT. SUP. ILIAC SPINE Fig. 150. — Region.s of the Abdo.mex. (Gerrish.) Right Hypochondriac. — The right lobe of the liver and the gall-bladder, hepatic flexure (right colic flexure) of the colon, and part of the right kidney. Right Lu.mb.ar. — As- cending colon, part of the right kidney, and some convolutions of the small intestines. Right Inguinal (Il- iac).— The cipcum, ver- miform appendix ; the right ureter. Epiga.sthic Region. — The pyloric end of the stomach, left lobe of the liver, the pancreas, the duodenum, parts of the kidneys, and the supra- renal capsules. Umbilical Region. — The transverse colon, part of the great omentum and mesentery, transverse part of the duodenum, and some convolutions of the jejunum and ileum, and part of both kidneys. Hypogastric Region. — Convolutions of the small intestines, the blad- der in children, and in adults if distended, and the uterus during preg- nancy. Left Hypochondriac. — The cardiac end of the stomach, the spleen and extremity of the pancreas, the splenic flexure (left colic flexure) of the colon, and part of the left kidney. Left Lumbar. — De- scending colon, part of the omentum, part of the left kidney, and some con- volutions of the small in- testines. Left Inguinal (Iliac). — Sigmoid flexure of the colon ; the left ureter. Chap. XIV] THE DIGESTIVE SYSTEM 263 THE STOMACH After the oesophagus perforates the diaphragm it ends in the stomach (gaster), which is the most dilated portion of the ali- mentary canal. It is a hollow pouch placed obliquely in the left side of the upper portion of the abdominal cavity.^ It is curved upon itself, so that below it presents a long, rounded outline, called the greater curvature, and above, a constricted, concave outline, called the lesser curvature. The greater curvature is directed to the left, and the lesser curvature faces mostly to the right. The fundus, or cardiac, end is the greater extremity, which pro- jects several inches to the left of the oesophagus and is in contact with the spleen. The opposite or smaller end is called the pyloric extremity and lies under the liver. The central portion between the fundus and pyloric extremity is called the intermediate region. The stomach has necessarily two openings : the one leading into the oesophagus is usually termed the cardiac aperture ; the other, leading into the small intestine, the pyloric. Both the cardiac and pyloric apertures are guarded by strong circular bands of muscle which are normally in a state of contraction. By this arrangement, the food is kept in the stomach until it is ready for intestinal digestion, when the circular fibres guarding the pyloric aperture relax and allow it to pass. When distended, the stomach measures about fifteen inches (38 cm.) from end to end and about five inches (13 cm.) antero- posteriorly, and has a capacity of about one quart. The above description applies to the position and form of the stomach when normally filled with food, but the student must bear in mind that, when empty, the stomach contracts down so as more nearly to approach a true cylinder, the contraction and dilatation affecting more the greater curvature than the lesser. When contracted, the stomach is shorter as well as of lesser diameter. Coats of the stomach. — It has four coats : from the out- side, (1) serous, (2) muscular, (3) submucous or areolar, and (4) mucous. (1) The serous coat is formed by a fold of the peritoneum. The 1 Epigastric and left hypochondriac region. 264 ANATOMY FOR NURSES [Chap. XIV fold is slung over the stomach, in much the same way as we sling a towel over a clothesline, and covers it before and behind. The anterior and posterior folds unite at the lower border of the Fig. 151. — The Stomach and Intestines, Fkont View, the Great Omen- tum HAVING been removed, AND THE LiVER TURNED UP AND TO THE RiGHT. The dotted Hue shows the normal position of the anterior border of the liver. (Gerrish.) stomach and form an apron-like appendage, the omentum, which covers the whole of the intestines. (2) The muscular coat of the stomach consists of three layers of unstriped muscular tissue : an outer, formed of longitudinal fibres ; a middle, of circular ; and an inner, of less well-developed, obliquely disposed fibres. Chap. XIV] THE DIGESTIVE SYSTEM 265 (3) The submucous, also called the areolar coat, is loose and vascular. It carries the nerves and vessels which go to and from the muscular and mucous coats. (4) The mucous coat is very soft and thick, the thickness being mainly due to the fact that it is densely packed with small tubular glands. It is covered with columnar epithelium, and in its undis- tended condition is thrown into folds or rugae. The surface is honeycombed by tiny, shallow pits, into which the ducts or mouths of the tubular glands open. The glands are of two kinds : (1) pep- tic, (2) pyloric. During digestion they secrete the gastric juice. Nerves and blood-vessels. — The stomach is supplied with nerves from the sympathetic system, and also with branches from the pneumogastric nerve, which comes from the cerebro- spinal system. The blood-vessels are derived from the three divisions of the coeliac axis. Function. — The functions of the stomach are (1) to connect the oesophagus with the intestine, (2) to hold the food while it undergoes gastric digestion, and (3) to secrete mucus and gastric juice. THE SMALL OR THIN INTESTINE^ The small intestine extends from the stomach (pyloric valve) above to the large intestine (valve of the colon) below. It is a convoluted tube about twenty feet (6.0 m.) in length, and fills the greater part of the front abdominal cavity. Its diameter at the beginning is about two inches (5 cm.), but it gradually dimin- ishes in size and is hardly an inch (2.5 cm.) in diameter at its lower end. The small intestine is divided by anatomists into three portions : — The duodenum. The jejunum. The ileum. The duodenum. — The duodenum is twelve fingers' breadth in length (eight inches or 20 cm.), and is the widest part of the small intestine. It extends from the pyloric end of the stomach to the jejunum. Beginning at the pylorus, the duodenum at first passes in a direction upward and backward to the under surface of the liver ; it then makes a complete bend and passes in a direction downward 266 ANATOMY FOR NURSES [Chap. XIV in front of the kidney ; it again turns in a right angle direction to the left and passes horizontally across the front of the ver- tebral column. This third portion of the duodenum lies retro- peritoneally, so that only its anterior aspect is covered by peri- toneum. The small intestine now passes forward so as to leave the posterior abdominal wall, and becomes completely invested by peritoneum and has a true mesentery. The point at which it becomes completely invested by peritoneum marks the ter- mination of the duodenum and the beginning of the jejunum. The jejunum. — The jejunum, or empty intestine, so called because it is always found empty after death, constitutes about two-fifths of the remainder, or seven and a half feet (2.2 m.), of the small intestine, and extends from the duodenum to the ileum. The ileum. — The ileum, or twisted intestine, so called from its numerous coils, constitutes the remainder of the small intestine, and extends from the jejunum to the large intestine, which it joins at a right angle. There is no definite landmark to determine the point at which the jejunum ceases and the ileum begins, although the mucous membrane of the one differs somewhat from the mucous mem- brane of the other; the change is a gradual transition, and one structure shades off into the other. The lengths in feet as given are arbitrary, but those usually accepted. Coats of the small intestine. — The small intestine has four coats, which correspond in character and arrangement with those of the stomach. (1) The serous coat furnished by the peritoneum forms an al- most complete covering for the whole tube except for part of the duodenum. (2) The muscular coat of the small intestine has only two layers: an outer, thiimer and longitudinal; and an inner, thicker and circular. This arrangement is necessary for the peristaltic action of the intestine. (3) The submucous, or areolar coat, carries blood-vessels, lymphatics, and nerves. (4) The mucous coat is thick and very vascular. ValvulcB conniventes. — About two inches beyond the pylorus the mucous and submucous coats of the small intestine are ar- ranged in circular folds called valvulae conniventes. Each of these Chap. XIV] THE DIGESTIVE SYSTEM 267 Fig. 152. — Portion of Small Intes- tine LAID OPEN TO SHOW VALVULE CONNI- VENTES. (Collins.) folds extends part of the way around the circumference of the in- testine. Unlike the rugfe of the stomach, the valvulae conniventes do not disappear when the intestine is distended. About the middle of the jejunum they begin to decrease in size, and in the lower part of the ileum they almost en- tirely disappear. The pur- pose of the circular folds is : (1) to prevent the food from passing through the intes- tines too quickly, and (2) to present a greater surface for the absorption of digested food. J^ilH. — Throughout the whole length of the small intestine the mucous membrane presents a velvety appear- ance due to minute finger-like projections called villi. Each villus consists of a central lymph channel called a lacteal, surrounded by a network of blood capillaries, held to- gether by lymphoid tissue. This in turn is surrounded by a layer of columnar cells and covered by the mucous coat of the intestine. After the food has been digested it passes into the lacteals and capillaries of the villi, so that this arrangement increases the surface for absorption. Glands and nodes of the small intestine. — Besides these projections formed for ab- sorption the mucous membrane is thickly studded with secretory glands and nodes. These are known as — 1. Simple follicles or crypts of Lieber- kuhn. 2. Duodenal or Brunner's glands. [ (a) Solitary lymph nodules. [ (h) Aggregated lymph nodules. (1) Simple follicles. — These glands are found all over the surface of the small and large intestine. They are simply tubular Fig. 153. — An Intes- tinal Villus, a, a, a, columnar epithelium ; b, b, capillary network ; d, lacteal vessel. 3. Lymph nodules 268 ANATOMY FOR NURSES [Chap. XIV depressions in the mucous membrane, lined with columnar epithe- lium. (2) Duodenal glands. — These glands are better known as Brunner's jiiaiuls. They are compound glands found in the Fig. 154. — Portion of the Mucous Membrane, fro.m the Ileum. Mod- erately magnifietl, exhibiting the villi on its free surface, and between them the orifices of the tubular glands. 1, portion of an aggregated lymph nodule; 2, a solitary lymph nodule ; 3, fibrous tissue. (Dalton.) submucous tissue of the duodenum. The simple follicles and the duodenal glands secrete the intestinal digestive juice which is named the succus entericus. (3) Lymph nodules. — The.se are of two varieties, (a) solitary lymph nodules, (b) aggregated lymph nodules of Peyer. Fig. 155. — Mucosa of Small Intestine in Ideal Vertical Cro88-8BCTion. (Gerrish.) Chap. XIV] THE DIGESTIVE SYSTEM 269 (a) Solitary lymph nodules. — Closely connected with the lym- phatic vessels in the walls of the intestines are small, rounded bodies of the size of a small pin's head, called solitary lymph nodules. These bodies consist of a rounded mass of fine lym- phoid tissue, the meshes of which are crowded with leucocytes. Into this mass of tissue one or more small arteries enter and form a capillary network, from which the blood is carried away by one or more small veins. Surrounding the mass are lymph channels which are continuous with the lymphatic vessels in the tissue below. Aggregated lymph nodules. — They are simply collections of lymph nodules, commonly called Peyer's patches. A well-formed Peyer's patch consists of fifty or more of these solitary lymph nodules, arranged in a single layer, close under the epithe- lium of the intestinal mucous membrane, and stretching well down into the tissue be- neath. These patches are circular or oval in shape, from one-half to three inches (12.5-75 mm.) long, and one- half inch (12.5 mm.) wide, and from twenty to thirty in number TheV are lartrest ^^^- 156. — - Aggregated Lymph Nodule "^ . ^ /■ (Peyer's Patch). (Gerrish.) and most numerous in the ileum. They increase in size during digestion. These Peyer's patches are the seat of local inflammation and ulceration in typhoid fever. It is interesting to note that in this condition, the long axis of the ulcer runs in the same direction as the long axis of the intestine ; whereas in tuberculosis of the intestine, the long axis of the ulcer is at right angles to the long axis of the intestines. Function. — It is in the small intestine that the greatest amount of digestion and absorption takes place. The valvulae conniventes delay the food so that it is more thoroughly subjected to the action of the digestive juices ; and being covered with villi they increase the surface for absorption. The glands of the small intestine secrete the succus entericus which aids in the digestion of food. 270 ANATOMY FOR NURSES [Chap. XIV THE LARGE OR THICK INTESTINE The largeness of the next division of the alimentary canal is in its transverse, not in its longitudinal, diameter ; for it is only about five feet (1.5 m.) long, but is much wider, being two and one-half inches (63 mm.) in its broadest part. It extends from the ileum to the anus. Like the small intestine, it is divided into three jjarts : the caecum with the vermiform appendix, colon, and rectum. The caecum. — The caecum {cwcus, blind) is a large blind pouch at the commencement of the large intestine. The small intestine opens into the side wall of the large intestine about two and a half inches ((53 mm.) above its — the large intes- tine's — commencement, the ca.^cum forming a cul-de-.sac be- low the opening. The opening from the ileum into the large intestine is j^rovided with two large projecting lips of mucous membrane which allow the pas- sage of material into the large Fig. 1.57 - Cavity of the c^cdm, jntestine, but etfcctuallv pre- ITS Front \V ALL HAVING BEEN CUT AWAY. • 1 • The valve of the colon and the opening veut the paSSagC of material 111 of the appendix are shown. (Gerrish.) ^^^ opposite direction. Thcse mucous folds form what is known as the valve of the colon, or the ileo-cfecal valve. The vermiform appendix is a narrow, wormlike tube about the diameter of an ordinary lead pencil, and from three to seven inches (7.5 to 17.5 cm.) long. It is attached to the lower end of the caecum, but its directions and relations are very variable. In a general way it may be said to be located in the right iliac fossa. The colon. — The colon, though one continuous tube, is sub- divided into the ascending, transverse, and descending colon, with the sigmoid flexure. The ascending portion ascends on the right side of the abdomen until it reaches the under surface of the liver, where it bends abruptly to the left (right colic or hepatic flexure), and is continued across the abdomen as the transverse Chap. XIV] THE DIGESTIVE SYSTEM 271 colon until, reaching the left side, it curves beneath the lower end of the spleen (left colic or splenic flexure) and passes downward as the descending colon. Reaching the left iliac region on a level with the margin of the crest of the ileum, it makes a curve like the letter S, — hence its name of sigmoid flexure, — and finally ends in the rectum. The rectum. — The rectum is from six to eight inches (15 to 20 cm.) long; it passes obliquely from the left until it reaches the middle of the sacrum, then it follows the curve of the sacrum and the coccyx, and finally arches slightly backward to its ter- mination at the anus. The anus is the aperture leading from the rectum to the exterior of the body. It is guarded, and except during defecation is kept closed by the contraction of two involuntary circvilar muscles called, respectively, the internal and external sphincters. Coats of the large intestine. — The large intestine has the usual four coats except in some parts where the serous coat only par- tially covers it, and the rectum, where the serous coat is lacking. The muscular coat consists of two layers of fibres, one arranged longitudinally and the other circularly. Beginning at the appen- dix, the longitudinal fibres are arranged in three ribbon-like bands, which extend the whole length of the colon to the rectum, and these bands being shorter than the rest of the tube, the walls are puck- ered between them. The third coat consists of submucous areolar tissue, and the fourth or inner coat consists of mucous membrane. The mucous coat possesses no villi and no circular folds. It contains numerous tubular glands and solitary lymph nodules which closely resemble those of the small intestine. Functions. — The functions of the large intestine are three. (1) The process of digestion is continued. This is due to the pres- ence of bacteria, and to the digestive juices with which the food became mixed in the small intestine. (2) The process of absorp- tion is continued, and (3) the waste products are removed from the body. ACCESSORY ORGANS OF DIGESTION The accessory organs of digestion are : (1) the salivary glands, (2) the tongue, (3) the teeth, (4) the pancreas, and (5) the liver. The first three have been described. 272 ANATOMY FOR NURSES [Chap. XIV PANCREAS The pancreas is an elongated organ, of a pinkish color, which lies in front of the first and second lumbar vertebrae and behind the stomach. It weighs between two and three ounces (60 to 90 grams), is about six inches (150 mm.) long, two inches (50 mm.) wide, and one-half inch (12.5 mm.) thick. In shape it somewhat resembles a hammer, and is divided into head, body, HEPATIC DUCT \^^^^^ ■/ '.^$ , SPLENIC AR COMMON BILE DUCT ORIFICE OF ACCESSORY PANCREATIC DUCT FiQ. 158. — Ddcts of the Pancreas. Part of the front wall of the duodenum is cut away. (Gerrish.) and tail. The right end or head is thicker and fills the curve of the duodenum, to which it is firmly attached. The left, free ,end is the tail, and reaches to the spleen. The intervening portion is the body. Structure of the pancreas. — It is a compound secreting gland and consists of minute tubes coiled up into little masses called lobules, each lobule having its own duct. The lobules are joined together by connective tissue to form lobes, and the lobes, united in the same manner, form the gland. The small ducts open into one main duct adbout the size of a goose-quill, which runs length- Chap. XIV] THE DIGESTIVE SYSTEM 273 wise through the gland, from the tail to the head. The pancreatic and common bile duct enter by means of a common opening into the duodenum about three inches (75 mm.) beyond the pylorus. Islands of Langerhans. — Scattered throughout the pancreas are round or ovoid bodies known as the islands of Langerhans. Each island is about one twenty-fifth inch (1 mm.) in diameter and consists of a group of many-sided cells. They are surrounded by a rich capillary network. Considerable evidence supports the theory that the internal secretion of the pancreas is formed by these islands. Function. — Two secretions are formed in the pancreas. (1) The pancreatic juice, which is one of the most important of the diges- tive juices, is an external secretion and is poured into the duodenum during intestinal digestion. (2) The secretion formed by the islands of Langerhans is an internal secretion that is absorbed by the blood and carried to the tissues. This internal secretion aids in the oxidation of glucose. Diabetes mellitus. — This is a disease characterized by a lack of oxidation of glucose and its consequent loss to the body as it is excreted in the urine. The cause is not settled, but it is believed that disease of the pancreas involving the islands of Langerhans may produce this condition. THE LIVER The liver (hepar) is the largest gland in the body, weighing ordinarily from fifty to sixty ounces (1500 to 1800 grams). It measures ten to twelve inches (25 to 30 cm.) from side to side, six to seven inches (15 to 17.5 cm.) from front to back, and three to four inches (7.5 to 10 cm.) from above downward in its thickest part. It is a dark reddish brown organ, placed in the upper right and middle portion of the abdomen,^ and extending somewhat into the left hypochondriac region. The upper convex surface fits closely into the under surface of the diaphragm. The under con- cave surface of the organ fits over the right kidney, the upper por- tion of the ascending colon, and the p.vloric end of the stomach. The number five prevails in the parts and appendages of the liver. Ligaments. — The liver is held in place by five ligaments, four of which are formed by folds of peritoneum, and the fifth, or round 1 Right hypochondriac and epigastric regions. 274 ANATOMY FOR NURSES [Chap. XIV Fig. 159. — The Liver. Front View. (Gerrish.) ligament, results from the atrophy of the umbilical vein of intra- uterine life. Fissures. — The liver is divided by five fissures into five lobes. The important fissures are (1) the portal, or transverse, which is the gateway for vessels, ducts, and nerves to enter and leave Fig. 160. — The Liver. Lowlt surface. (Gerrish.) Chap. XIV] THE DIGESTIVE SYSTEM 275 the liver, and (2) the gall bladder fissure, which supports the gall bladder. Both these fissures are in the under surface of the liver. Lobes. — The liver is divided into five lobes : — 1. Right (largest lobe). 2. Left (smaller and wedge-shaped). 3. Quadrate (square). 4. Caudate (tail-like). 5. Spigelian. Vessels. — The liver has five sets of vessels : — 1. Branches of portal vein. 2. Hepatic veins. 3. Bile ducts. 4. Branches of hepatic artery. 5. Lymphatics. Minute anatomy of liver. — The liver may be regarded as made up of many minute livers called lobules. Each lobule is an ir- regular body about one-twelfth inch (2 mm.) in diameter, com- posed of a multitude of hepatic cells packed so closely together Fig. 161. — Diagrammatic Representation of two Hepatic Lobules. The left-hand lobule is represented with the intralobular vein cut across ; in the right-hand one the section takes the course of the intralobular vein, p, interlobular branches of the portal vein ; /i, intralobular branches of the hepatic veins ; s, sub- lobular vein. The arrows indicate the direction of the course of the blood. The liver-cells are only represented in one part of each lobule. that only enough room is left between them for the passage of vessels and nerves. Thus each lobule is a mass of hepatic cells, pierced everywhere with a network of blood capillaries. 276 ANATOMY FOR NURSES [Chap. XIV Hepatic cells. — Thev are about i-q\s of an inch in diameter, but because of compression are very irregular in shape. They are epitheHal cells composed of protoplasm, with a single clear nucleus, but no cell-wall. Fio. 162. — Lobule of Rabbit's Liver, Vessels and Bile Ducts Injected. a, central or intralobular vein ; b, b, interlobular veins ; c, interlobular bile duct. The portal vein. — The portal vein, after entering the liver, divides into a vast number of branches which form a network surrounding each lobule, and hence are known as interlobular (between the lobules). From this network minute capillaries enter the lobule, penetrate between each cell and thus surround them, so that each cell is generously supplied with blood con- taining the raw material for the manufacture of bile. These capillary branches which enter the lobule and surround the cells Chap. XIV] THE DIGESTIVE SYSTEM 277 are called intralobular (within the lobule). These vessels con- verge toward the centre of the lobule like the spokes of a wheel and empty into a vein (intralobular) which carries the blood away from the lobule. The intralobular veins from a number of lobules empty into a much larger vein upon whose surface a vast number of lobules rest, and therefore the name sublobular (under the lobule) is given to this kind of veins. They empty into still larger veins, the hepatic, which converge to a few large trunks and terminate in the inferior vena cava, which is em- bedded in the posterior surface of the gland. The bile ducts. — The surfaces of the hepatic cells are grooved, and the grooves on two adjacent cells fit together and form a channel into which the bile is poured as soon as it is formed by the cells. These channels form a network between and around the cells as intricate as the network of blood-vessels. They are called intralobular ducts, and empty into larger ducts called in- terlobular. These unite and form larger and larger ducts until two main ducts, one from the right and one from the left side of the liver, unite in the portal fissure and form the hepatic duct. The hepatic duct runs downward and to the right for about two inches (50 mm.) and then joins at an acute angle the duct from the gall-bladder, termed the cystic duct. The hepatic and cystic ducts together form the common bile duct {ductus com- munis choledochus) , which runs downward for about three inches (75 mm.) and enters the duodenum about three inches (75 mm.) below the pylorus. This orifice serves as a common opening for both the common bile and the pancreatic duct. It is very small and is guarded by a sphincter muscle which keeps it closed except during digestion. (See Fig. 158.) Hepatic artery. — We must remember that the blood brought to the liver by the portal vein is venous blood from the stomach, spleen, pancreas, and intestines. It is rich with the products of digestion and intended for the manufacture of bile, etc. It is not intended for purposes of nourishment of the liver itself, hence arterial blood is furnished by the hepatic artery. It enters the liver with the portal vein, divides and subdivides in the same way, thus forming another network between the lobules, and in the lobules between the cells. The capillaries from the portal vein and the hepatic artery are separate and distinct until, near 278 ANATOMY FOR NURSES [Chap. XIV the centre of each lobule, they unite, and all the blood sup])lied to the liver is carried away from it by the one set of \eins de- scribed under head of portal vein. Lymphatics. — There is a deep and a superficial set. They begin in irregular spaces in the lobules, form networks around the lobules, and run always from the centre outward. They drain off waste j)roducts and unconsumed nutritious substances. Glisson's capsule. — The whole liver is invested in an outer capsule of areolar connective tissue, which is reflected inward at the portal fissure and encloses the vessels and ducts passing through this opening. Serous membrane. — With the exception of a few small areas, the liver is enclosed in a serous tunic derived from the jjeritoneum. Nerves. — Nerves are derived from the left pneumogastric and the solar plexus.^ Functions. — The liver may be compared to a wonderful laboratory, the most wonderful in the body. It has three im- portant functions : — 1. Bile secreting. — The cells of the liver manufacture bile from the blood brought to them by the i)ortal vein. The function of bile is considered in the next chapter. 2. Glycogenic. — The cells of the liver take from the blood brought to them by the portal vein a substance called glucose, which is derived from the carbohydrates eaten. This is stored in the liver in the form of glycogen until such time as the body needs more glucose than the food eaten furnishes. When such demand is made, the liver cells reconvert the glycogen into glucose and pour it into the circulation, 3. Higher chemical actitities. — i\Iany of the end products of pro- tein digestion are toxic substances. Some of these substances are acted upon by the liver and rendered less harmful. Others are changed into urea, and in the form of urea it is possible for the kidneys to eliminate them from the blood. The gall-bladder. — The gall-bladder is a pear-shaped sac, lodged in the gall-bladder fissure on the under surface of the liver, where it is held in place by a fold of the peritoneum. It is about four inches (10 cm.) long, one inch (25 mm.) wide, and holds about ten drachms (25 gms.). It is composed of three coats: (1) the inner one is ' See page 376. Chap. XIV] SUMMARY 279 mucous membrane, (2) the middle one is muscular and fibrous tissue, and (3) the outer one is serous membrane derived from the peritoneum. Function. — The gall-bladder serves as a reservoir for the bile. During digestion the bile is poured steadily into the intestine ; in the intervals it is stored in the gall-bladder. SUMMARY Digestion. — This is the process of changing food into products ca- pable of absorption. It is dependent on the proper functioning of certain organs that are grouped together and called the digestive system. Mouth. Pharynx. (Esophagus, or gullet. Stomach. Digestive System Alimentary canal Small or thin in^ testine ( Duodenum. i Jejunum. i Ileum. f Caecum. Large or thick in- ^ , ^° . < Colon testme i ^^ ,• -r, j^ I Descending. [ Rectum. ° r Ascending. < Transverse. Accessory organs Alimentary Canal ' Salivary glands. Tongue. Teeth. Pancreas. Liver. ' About 28 ft. long. From mouth to diaphragm - 3 coats From diaphragm to rectum 4 coats Above — palate Hard palate. Soft palate — tonsils. r Mucous. < Areolar. [ Muscular. Mucous. Areolar. Muscular. Serous derived from peri- toneum. uvula, palatine arches, and Mouth or Buccal Cavity Below — tongue. Front — lips. Sides — cheeks. Tonsils. Contains Tongue. Salivary glands. I Teeth. 280 ANATOMY FOR NURSES [Chap. XIV Tonsils Tongue Salivary Glands Teeth Pharynx Function Collections of lymph nodules occupy triangular space between palatine arches on either side of throat. 1. May be a source of lymphocytes and leu- cocytes. 2. May act as a filter and prevent entrance of microorganisms. ■ Special organ of sense of taste. . . . . (I. Stimulates secretion of digestive juices. Assists m „ . . ^ . ... ° ' ,. ,. < 2. Assists in swallowing, digestion „ a + I 3. Secretes mucus. Parotid — just under and in front of ear. Submaxil- \ lary > Below the jaw and under the tongue. Sublingual J Function — Form a secretion, that mixed with that of the mouth is called saUva. Contained in sockets of alveolar processes of maxillae and mandible. Gums — cover processes and extend into sockets. Sockets — lined with perios- j Attaches teeth to sockets, teum \ Source of nourishment. Root — one or more fangs contained in socket. Crown — projects beyond level of gums. Neck — portion between root and crown. Gives shape. Encloses pulp cavity which con- tains nerves and blood-vessels, that enter by canal from root. Enamel — Caps the crown. Cement — Covers the root. 1. Temporary — r Incisors 8 7 months to < Canines 4 2i yrs. I Molars 8 Incisors 8 Canines 4 Premolars 8 Molars 12 Function — To assist in the process of mastication. Funnel-shaped bag, A^ inches long, between mouth and oesophagus. Muscular and lined with mucous membrane. 1 fauces. 2 posterior nares. 2 Eustachian tubes. 1 larynx. 1 oesophagus. 3 portions Composed of three substances developed from epi- thelium 2 sets Dentine • 2. Permanent — 6 yrs. to 21 yrs. of age 20. 32. 7 apertures " Chap. XIV] SUMMARY 281 (Esophagus, or Gullet 3 coats Function — Stomach, Gaster or Curved upon itself Small or Thin Intestine f Tube — 9 in. long. Extends from pharynx to stomach. Inner — mucous — disposed in folds. Middle — submucous. r Internal circular fibres. Outer — muscular j External longitudinal I fibres. 1. Connects the pharynx with the stomach. 2. Receives the food and passes it on to stomach. Hollow pouch. Capacity, 1 qt. Oblique position in epigastric and left hypochondriac regions. 'Greater curvature, below, directed toward the left. Lesser curvature, above, directed toward the right. Fundus or cardiac end is in contact with spleen. Pyloric extremity under the liver. Intermediate region, between fundus and pyloric extremity. Outer — serous — peritoneum. r 1. Longitudinal fibres. Muscular < 2. Circular. I 3. Oblique. Submucous — vascular. r Rugae. Mucous < f S.ympathetic system. I Pneumogastric nerve. Blood-vessels from coeliac axis. 1. Connect the oesophagus with the intestine. 2. To hold the food while it undergoes gas- tric digestion. 3. To secrete mucus and gastric juice. Convoluted tube extends from stomach to valve of colon. Twenty feet coiled up in abdominal cavity. ( Duodenum, divisions < Jej unum. I Ileum. 1 . Serous from peritoneum, called mesentery. J Longitudinal layer. \ Circular layer. ( Blood-vessels. 4 coats Nerves Function Glands Peptic \ . . Pyloric l^^^^^^J^^^^- 2. Muscular 4 coats 3. Submucous 4. Mucous < Lymphatics. I Nerves. f Circular folds. I Villi — contain lacteals. 282 ANATOMY FOR NURSES [Chap. XIV Small or Thin Intestine Glands and nodes Simple follicles Duodenal or Brunncr's Ljinph nodules > Secrete intestinal juice. Solitary. Aggregated Ijinph nod- ules of Pej'cr — fifty or more solitary lymph • nodules form so-called patches in small in- testine. Function {Digestion. Absorption. Secretion of succus entericus. 3 divisions Colon Large orThick Intestine ' Largeness in its transverse, not in its longitudinal, diameter. Length, 5 ft.; width, 2| in. to 1^ in. Extends from ileum to anus. Caecum, with vermiform appendix. ' Ascending. Transverse. Descending with sigmoid flexure. Rectum — f Internal sphincter, anus 1 External sphincter. 1 . Serous, except in some parts it is only a partial covering, and at rectum it is wanting. Arranged in tluee Longitu- "b^^^'^ - ^^^ dinal } ^^^d« *^^* ^^- laycr S^^ ^* appen- dix, and extend Circular [ to rectum, layer 3. Submucous, r No villi. No circular folds. 4. IMucous I ( Tubular glands. Numerous < SoUtary lymph I nodules. . „ . I Continuance of digestion and absorption Function ^,. • .• r ^ Ehmination of waste. 4 coats 2. Muscular. Chap. XIV] SUMMARY 283 Pancreas Liver Hammer shape Size Structure Function In front of first and second lumbar vertebrse, behind stomach. r Head attached to duodenum. < Body in front of vertebra. I Tail reaches to spleen. Six inches long. Two inches wide. One-half inch thick. Weight — two to three ounces. Compound gland — coiled tubes form lobules. Lobules held together by connective tissue form lobes. Lobes form gland. Duct from each lobule empties into pan- creatic duct. 1. Secretes pancreatic juice. 2. Forms an internal secretion. Largest gland in body. ( Right hypochondriac. Location < Epigastric. I Left hj'pochondriac. Convex above — fits under diaphragm. Concave below — fits over right kidney, ascending colon, and pyloric end of stomach. L Suspensory, broad, or falciform Five liga- I 2. Coronary ments | 3. Right lateral 4. Left lateral 5. Round liga- ment 1. Umbilical fis- sure 2. Gall-bladder fissure 3. Portal or trans- verse fissure 4. Ductus venous i fissure > Dorsal surface. 5. Vena cava J 1. Right (largest lobe). 2. Left (smaller and wedge-shaped). Five lobes or sodium and potassium, bulphate Carbonate Phosphate 1 p , • , _, , > or calcium and magnesium. Carbonate J The inorganic salts are not oxidized in the body and therefore do not yield energy, but they are an essential part of all the tissues, and take part in the functions of the body in six ways: (1) they maintain the alkaline or neutral reaction of the fluids of the body ; (2) they furnish the material for the acidity or alkalinity of the digestive fluids and other secretions ; (3) they help in regulating the flow of fluids to and from the tissues, because they maintain the normal osmotic pressure ; (4) they enter largely into the composition of the bones, teeth, and cartilage ; (5) they are necessary for the clotting of blood ; and (6) they give the fluids of the body their influence upon the elasticity and irritability of nerve and muscle. Proteins. — Proteins are complex compounds and consist of carbon, hydrogen, nitrogen, oxygen ; sulphur, phosphorus, and other elements may be present. They differ from carbohydrates and fats in having nitrogen and therefore are described as nitroge- nous compounds. They, occur in the form of : — Albumins. — Simple proteins that are soluble in water and coagulable by heat. The white of egg when cooked, the scum that forms on milk when it is heated, and the coating that forms on meat when it has been subjected to high temperature are all forms of albumin that have been coagulated by heat. Caseinogen. — If milk is allowed to stand until it sours, or if the process is hastened by the addition of acid or rennet, the caseinogen is formed into a curd. Gluten. — This is the starchy nitrogenous substance found in wheat flour. Legumin. — This is a protein substance found in vegetables that are classed as legumes, i.e. peas, beans, lentils, etc. Extractives. — These are protein substances found in plant and animal bodies as a result of their metabolism. 288 ANATOMY FOR NURSES [Chap. XV Carbohydrates. — All sugars and starches are grouped together under the name of carbohydrates. They contain but three ele- ments, carbon, hydrogen, and oxygen, the two latter in the pro- portion to form water. The varieties of carbohydrates are as follows : — Glucose or dextrose, found in fruits, es- pecially the grape, and in the blood. CeHnOc Fructose or levulose, found with glucose in fruits. C6H12O6. J r Sucrose or cane sugar. C12H22O11. < Lactose or milk sugar. Ci2H220n. I Maltose or malt sugar. C12H22OU. Simple or Mono saccharids Complex or Disaccharids Invert sugai Sugars. — A study of the formulge of the complex sugars will show that the composition is the same, but they are differently named because they give different reactions. Before any of the complex sugars can be utilized in the body they must first be changed either into glucose, or into invert sugar, which consists of a molecule each of glucose and fructose. One molecule of a complex sugar plus one molecule of water will form one mole- cule of glucose and fructose. Complex Sugar Water Glucose Fructose 0^1^22011 + H2O = C6H12O6 . C(>Hi20c Invert Sugar. Polysaccharids < Starch — found in grain, tubers, roots, etc. (CeHioOs)/^ Cellulose — outside covering of starch grains, and basis of all woody fibres. (CeHioOs)?! Glycogen — form in which sugar is stored in liver. (C6nio05)n Dextrin — fomicfl from starch by par- tial hydrolysis. (CeHioOs)/! Polysaccharids. — In all of these compounds the composition of the molecule is supposed to be rather complex, although the elements are present in each in the same relative proportion, as shown in the formulae. The value of n, however, may be very small or very large and is probably different for each polysaccha- rid, which makes the actual composition of each member of the Chap. XV] DIGESTIVE PROCESSES 289 group different. For instance, n for the starch molecule is large, while for the dextrin molecule it is smaller, so that a single starch molecule in digestion may split into several molecules of dextrin of the same relative composition. Fats. — Fats are composed of carbon, hydrogen, and oxygen, but the two latter elements, hydrogen and oxygen, are not in the pro- portion to form water. They are not simple substances, but are mixtures of palmitin, stearin, and olein, which are derived from the fatty acids named respectively palmitic, stearic, and oleic. Each molecule of a simple fat is made from one molecule of glycerine and three molecules of a fatty acid. Glycerine Stearic Acid Stearin Water C3H5(OH)3 + 3 H . C18H35O0 -> C3H5(CisH3502)3 + 3 H2O. In general, fats and oils are practically the same, and the mixture of fats found in the body is liquid at the body temperature. They are soluble in ether, chloroform, and hot alcohol, but are insolu- ble in water. Decomposition of fats. — Under the influence of steam, mineral acids, and certain ferments found in the body, fats split up into the substances out of which they are built, i.e. glycerine and fatty acid. Stearin Water Glycerine Stearic Acid C3H5(Ci8H3502)3 + 3 H2O -> C3H5(OH)3 + 3 H . C18H35O2. The process of saponification is similar to the above, only that instead of water a base is used and the final products are glyce- rine and soap. Stearin Potassium Hydroxide Glycerine Soap C3H5(Ci8H3502)3 + 3 KOH -^ C3H5(OH)3 + 3 K(Ci8H3502). Necessity for digestion. — Digestion is necessary because organic foods, with the exception of simple sugars, are not soluble in water, hence they cannot be absorbed. Inorganic foods are absorbed directly, because salts dissolve in water. DIGESTIVE PROCESSES Digestion consists of two processes, i.e. mechanical and chemical. Mechanical processes. — Mechanical processes consist of vari- ous movements that result from the action of the muscles in the alimentary canal. They serve two important purposes: (1) in 290 ANATOMY FOR NURSES [Chap. XV taking food in and moving it along through the digestive canal, and (2) in separating the food into small particles upon which the digestive fluids can act rapidly. These processes consist of : — 1. Mastication. 2. Deglutition. 3. Peristaltic action of oesophagus. 4. Peristaltic action of stomach. 5. ^Movements of the intestines. 6. Defecation. Chemical digestion. — Chemical digestion is a process of hy- drolysis which is dependent upon the presence of enzymes. By the term hydrolysis is meant the breaking down of complex molecules into simpler ones with the absorption of water. An example of hydrolysis is the conversion of any of the complex sugars into simpler sugars. (See page 8.) In the disaccharids only one splitting is necessary, as each molecule of a complex sugar plus one molecule of water will give two molecules of a simple sugar which is soluble and read>' for absorption. The starches are more com- plex in their composition, hence they must pass through several stages of decomposition before they are changed by hydrolysis to a simple sugar. Each splitting of the molecule gives substances with simpler composition, though with the same relative proportion of the constituents, and to each such substance produced is given a special name. The proteins are even more complex than the starches, and pass through a greater number of stages in the process of digestion. The substances formed in each stage are of lighter molecular weight and are named (1) meta-proteins, (2) pro- teoses, (3) peptones, (4) polypeptids, and (5) amino-acids. Many physiologists are of the opinion that protein digestion does not pass beyond the peptone stage, as peptones are soluble and can be absorbed. Fats are hydrolyzed and split up into fatty acids and glycerine; the fatty acids are then acted upon by the bile and pancreatic juice, and form soap. (See page 298.) Cause of chemical digestion. — It is possible to make carbo- hydrates, proteins, and fats undergo the same changes outside the body as occur during digestion. Carbohydrates, proteins, and fats, if boiled with a mineral acid or subjected to the action of enzA'mes, will hydrolyze and split up into simpler substances. Chap. XV] DIGESTIVE PROCESSES 291 Within the body the change takes place at body temperature, and is due to the presence of organic ferments or enzymes present in all of the digestive juices. Enzymes. — An enzyme is an organic ferment produced by living cells, and is capable of effecting chemical change without itself undergoing alterations in the process. Each enzyme has a definite action at a suitable temperature, and will only work in a medium of definite reaction, either acid or alkaline. Further, the products of the action must be removed, and in the body this is accomplished by absorption. CHANGES THE FOOD UNDERGOES IN THE MOUTH Mastication. — \\Tien solid food is taken into the mouth it is cut and ground by the teeth, being pushed between them again and again by the muscular contractions of the cheeks and the movements of the tongue until the whole is thoroughly crushed and ground down. Insalivation. — During the process of mastication saliva is poured in large quantities into the mouth, and mixing with the food moistens it and reduces it to a soft, pulpy condition, A cer- tain amount of air caught in the bubbles of the saliva also becomes entangled in the food, and this facilitates the penetration of the gastric juice. Secretion of saliva. — The secretion of saliva is the result of reflex stimulation of the nerves connected w^ith the salivary glands. The movements of mastication, the taste and odor of food, act as stimulants to the sensory or afferent nerves which carry these im- pulses to a nerve centre in the brain (probably in the medulla oblongata), and from thence motor impulses are transmitted through efferent nerves to the gland. Psychical acts may also influence the secretion of saliva, as for example the thought or smell of food, or a feeling of nausea may stimulate the secretion, and anger, fear, or worry may inhibit it. Saliva. — Saliva is a mixture of the secretions of all three pairs of salivary glands, as well as of the small glands of the mucous membrane of the mouth. It consists of water, some mucus, and an enzyme called ptyalin. It has a specific gravity of 1.004 to 1.008 and an alkaline reaction. The amount secreted in twenty- four hours is estimated to be from one to two quarts. 292 ANATOMY FOR NURSES [Chap. XV The functions of saliva. — Saliva has four distinct functions. (1) It assists in speech by moistening the mucous membrane of the mouth and tongue. (2) It assists in mastication and degkiti- tion by softening and moistening the food. SaHva causes the masticated portions to stick together and thus helps to form a bolus which is coated with mucus and easily swallowed. (3) It renders soluble substances capable of being tasted. Salts, sugar, acids, and bitters are dissolved in the saliva. (4) It acts upon starch. Ptyalin. — By the ptyalin-ferment present in saliva, starch, which is an insoluble substance, is partially changed to dextrin and sugar (maltose). This process is a complicated one and it is probable that a number of intermediate compounds exist between the huge starch molecule and the dextrin and maltose. This change is best effected at the temperature of the body,^ in a slightly alkaline solution, saliva that is distinctly acid hindering or ar- resting the process. Boiled starch is changed more rapidly and completely than raw, but the food is never retained in the mouth long enough for the saliva to more than begin the transformation of starchy matters.- Deglutition, or swallowing. — The food thus softened and moist- ened is collected from every part of the mouth by the movements of the tongue, brought together upon its upper surface, and then pressed backward through the fauces into the pharynx. The elevation of the soft palate prevents the entrance of food into the nasal chambers, while the epiglottis bars its entrance into the air-passages, and it is guided safely and rapidly through the pharynx into the oesophagus. Here it passes beyond the control of the will ; it is grasped by the oesophageal muscles and by a continuous peristaltic action is carried downward. The cardiac orifice of the stomach is guarded by a sphincter muscle which is normally in a state of contraction. The peristaltic wave which passes slowly down the oesophagus inhibits this contraction and forces the food into the stomach. During the process of mastication, insalivation, and deglutition the food is first reduced to a soft, pulpy condition ; second, 1 A temperature of 100° F. in the alimentary canal is necessary for digestion, hence iced drinks or iced foods that lower this temperature delay digestion, * The salivary glands do not become active until the subject is from four to six months old ; hence the reason for avoiding starchy food for young infants. Chap. XV] DIGESTIVE PROCESSES 293 any starch it may contain begins to be changed into sugar ; third, it acquires a more or less alkaline reaction. Vomiting. — Under ordinary circumstances the contractions of the cardiac sphincter muscle prevent the regurgitation of food, but strong contractions of the stomach or spasmodic contractions of the abdominal muscles may, if the diaphragm is fixed, force the contents of the stomach through the oesophagus and mouth to the exterior. This is called vomiting., CHANGES THE FOOD UNDERGOES IN THE STOMACH, OR STOMACH DIGESTION Peristaltic action of the stomach. — The food which enters the stomach is delayed there by the contraction of the sphincter muscles at the cardiac and pyloric openings. The cavity of the stomach is always the size of its contents, which means that when it is empty it is contracted, but when food enters it expands just enough to hold it. Within a few minutes after the entrance of food small contractions start in the middle region of the stomach and run toward the pylorus. These contractions are regular and become more and more forcible as digestion progresses. As a result of these movements the food is macerated, mixed with the acid gastric juice, and reduced to a liquid mass called chyme. At intervals the pyloric sphincter relaxes and the wave of contraction forces some of the chyme into the duodenum. The fundal end of the stomach does not take part in these movements, but serves as a reservoir for food which is under slight pressure, as the muscles are in a state of continual contraction or tone. Due to the lack of movement and the muscular tone, the gastric juice cannot penetrate the bolus of food, and the ptyalin with which it became mixed in the mouth continues its action, and the digestion of starch continues for about twenty minutes. As the chyme is gradually forced into the duode- num, the pressure of the fundus forces the food into the pyloric end. Time required for stomach digestion. — It is obvious that the time required for gastric digestion depends upon the nature of the food eaten. An average meal of mixed food requires about five hours for gastric digestion. The ejection of chyme through the pylorus occurs at regular intervals, and is supposed to depend upon the consistency and acidity of the chyme. Solid particles 2<)4 ANATOMY FOR NURSES [Chap. XV forced against the pylorus tend to keep it closed, but hydrochloric acid in the stomach seems to favor or produce relaxation of the pyloric sphincter. In the intestines hydrochloric acid has a con- trary effect, as it causes a contraction of the sphincter, which remains closed after each ejection until the acidity has been neutralized. Secretion of gastric juice. — During the intervals of digestion the stomach is bathed in an alkaline mucus. The entrance of food acts as a stimulant to the whole organ. The blood-vessels dilate, and the glands pour out an abundant secretion upon the mucous lining. This secretion continues as long as food remains in the stomach, and is caused and maintained by two factors : (1) psychical, the sensations of eating, the taste and odor of food stimulate the sensory nerves situated in the mouth and nose. These afferent impulses are transferred through nerve centres to efferent fibres of the pneumogastric nerve, and thus are carried to the stomach. (2) Chemical, (a) by secretogogues contained in certain foods and (b) by secretogogues contained in the products of digestion. Certain foods, such as meat juices and extracts, con- tain substances called secretogogues or hormones which are sup- posed to act directly upon the nerves of the pyloric mucous membrane and form a substance called gastrin or gastric secretin, which is absorbed into the blood and carried to the gastric glands. This substance stimulates the glands to secretion. Other foods, such as milk, bread, white of egg, etc., do not appear to contain secretogogues. When such foods are eaten, a psychical secretion is started and when this has acted, some products of their digestion in turn become capable of stimulating a further secretion of gastric juice. Gastric juice. — Gastric juice, -secreted by the peptic and pyloric glands in the mucous lining of the stomach, is a thin, colorless, or pale yellow fluid, of an acid reaction. The amount secreted in twenty-four hours has never been accurately measured, but has been estimated to be about fifteen pints (7.1 litres). It contains few solids, and is dependent for its specific action upon two enz^'mes called (1) pepsin and (2) rennin. Pepsin is only properly active in an acid solution, and we therefore find that free hydrochloric acid in the proportion of 0.2 to 0.4 per cent is always present in normal gastric juice. Chap. XV] DIGESTIVE PROCESSES 295' The action of gastric juice upon food. — The action of gastric juice upon food is dependent on (1) hydrochloric acid, (2) pepsin, and (3) rennin. (1) Hydrochloric acid. — The hydrochloric acid found in the gastric juice is supposed to be secreted by special cells in the in- termediate portion of the stomach, from chlorides found in the blood. The chief chloride is sodium chloride (NaCl), and by some means this is decomposed ; the chlorine (CI) combines with hydro- gen (H), and is then secreted upon the free surface of the stomach as hydrochloric acid (HCl). Besides giving an acid medium, which is necessary for the pepsin to carry on its work, it serves : (1) to swell the protein fibres and thus give easier access to pep- sin, (2) it helps in the inversion of sugar, i.e. changing complex sugars to simple ones, (3) it acts as a disinfectant and kills many bacteria that enter the stomach, and (4) it helps to regulate the opening and closing of the pyloric valve. (2) Pejysin. — The property of converting proteins into peptones is dependent upon the enzyme pepsin. Whatever the protein may be, whether the albumin of eggs, the gluten of flour in bread, the myosin in flesh, the result is the same ; pepsin, in conjunc- tion with an acid at the temperature of the body, transforms them into peptones. This process of converting an insoluble protein to a soluble peptone is complicated, as the protein under digestion passes through a number of intermediate stages. Peptones readily dissolve in water, and pass with ease through animal membranes. (3) Rennin. — So far as is known, this ferment acts only upon the soluble protein of milk, which is called caseinogen. It converts this substance into a clotted mass called curd, which is later prepared for absorption by the action of the enzyme pepsin. The gastric juice has no action upon starch, and upon fats it has at most a limited action. The fats are set free from their mixture with other food-stuffs by the dissolving action of the gastric juice, they are liquefied by the heat of the body, and are scattered through the chyme in a coarse emulsion by the movements of the stomach. In addition to pepsin and rennin, various authorities describe other enzymes in the gastric juice, but there is a good deal of uncertainty regarding them. It is probable that a third enzyme, called gastric lipase, acts upon fats that are ingested in an emulsi- 296 ANATOMY FOR NURSES [Chap. XV fied form, and this action may be important in the digestion of milk fat by infants, as the pancreas is inactive. CHANGES THE FOOD UNDERGOES IN THE SMALL INTESTINE The ch^ine, on entering the duodenum, after an ordinary meal, is a mixture of various matters. It contains some undigested proteins ; some undigested starch ; oils from fats eaten ; peptones formed in the stomach ; salines and sugars ; all mixed with a good deal of water and the secretions of the alimentary canal. It is in the intestines that this mixture undergoes the most profound diges- tive changes. These changes which constitute intestinal digestion are effected by : (1) the movements of the intestines, (2) the pan- creatic juice, (3) the succus entericus or secretion of the intestinal glands, and (4) the bile. Movements of the small intestine. — The movements of the small intestine are of two kinds : (1) peristaltic and (2) rhythmic segmentation, (1) A peristaltic movement may be defined as a quick succession of waves of contraction and inhibition passing slowly along the intestine and affecting the longitudinal fibres. The wave of contraction begins at a certain point, passes downward away from the stomach, and is always preceded by an area of inhibition or relaxation. The purpose of it is to pass the food slowly forward, and it is obvious that the wave of contraction is more effective in forcing the contents forward because just in front of it the intes- tine is relaxed. (2) The movements of rhythmic segmentation consist of contractions of the circular fibres of the intestine, which occur at the same time as the contractions of the longitudinal fibres. The purpose of these contractions is to split the column of food into a number of equal segments. Within a few seconds each of these segments is halved and the corresponding halves of adjoining segments unite. Again contractions recur and these newly formed segments are divided, and the halves re-form in the same position as they had at first. In this way every particle of food is brought into intimate contact with the vahiilre conniventes and is thoroughly mixed with the digestive juices. Secretion of pancreatic juice. — Just as chewing and swallowing Chap. XV] DIGESTIVE PROCESSES 297 of food starts the gastric secretion, so the presence of acid chyme in the intestine starts the pancreatic secretion. This effect is due to a special substance called secretin which is formed by the action of the acid upon some substance present in the mucous membrane of the intestine. This secretin is absorbed by the blood and carried to the pancreas, which it stimulates to activity. Like the secretin of the gastric juice, this is not an enzyme but a hormone. Pancreatic juice. — Healthy pancreatic juice is a clear, some- what viscid fluid, with a very decided alkaline reaction. The amount secreted in twenty-four hours is about 15 to 25 ounces (7.1 to 11 litres). It contains few solids and is dependent for its remarkable power on three enzymes : (1) trypsin, (2) diastase (amylopsin), and (3) lipase (steapsin). Action of pancreatic juice upon food. — Pancreatic juice has the power of acting on all the food-stuffs, proteins, carbohydrates, and fats. This action is due to its enzymes. (1) Trypsin. — Tr^^Dsin, like pepsin, has the power to decompose proteins, but the action is more rapid and more powerful, and the protein molecule is broken up into simpler substances than pep- tones, depending on the amount of trypsin and the time that it acts. If complete hydrolysis takes place, the end products consist chiefly of amino-acids. Unlike pepsin, trypsin requires a neutral or alkaline medium. The preliminary action of pepsin, on a protein molecule, hastens the action of trypsin, and renders it more com- plete than if the trypsin acted alone. Diastase {Amylopsin). — The action of diastase is similar to that of ptyalin. It causes hydrolysis of starch with the produc- tion of maltose. The starchy food that escapes digestion in the mouth and stomach becomes mixed with this enzyme and con- tinues under its action until the ileo-caecal valve is reached. Lipase (Steapsin). — Lipase is an enzyme capable of decom- posing fats. This action is twofold : (a) It emulsifies them. (6) It splits them up into fatty acids and glycerine. (a) If we shake up olive oil with water, the two cannot be got to mix : as soon as the shaking ceases, the oil floats to the top ; but if we shake up olive oil with pancreatic juice, the oil remains evenly suspended in it. The reason of this is that the oil has been minutely divided into tiny droplets, and each droplet surrounded 298 ANATOMY FOR NURSES [Chap. XV by a delicate envelope supplied from the albumin in the pancreatic juice, so that they cannot fuse together to form the large drops, which would soon float to the top.^ (b) The fats that are not emulsified are broken up into glycerine and fatty acids. The glycerine is absorbed, and the fatty acids in the presence of an alkali form soaps which are soluble in water and capable of absorption. It is probable that the greater part of the fat is absorbed by the latter method. Succus entericus, or intestinal juice. — Succus entericus is the secretion of the intestinal glands. It is a clear, yellowish fluid, having a marked alkaline reaction and containing a certain quantity of mucus. The number of enzymes ^ described as present in succus enteri- cus differs with different authorities audit is probable that the entire physiology is not known. Its chief function seems to be a continu- ation of the work of pepsin and trypsin and the inversion of com- plex sugars to simple ones. It also acts as a diluent and supplies a loss of fluid. Bile. — Bile, secreted in the lobules of the liver and stored in the gall-bladder until needed, is a fluid of a golden brown or greenish color ^ with an alkaline reaction. The quantity secreted in twenty-four hours varies with the amount of food taken, but is estimated at about one quart. Bile contains no enzyme, but the fact that it is poured into the intestine through an orifice common to it and the pancreatic juice suggests that these two fluids cooperate in their action on food. Action of bile. — Its most important function as a digestive is noted in its action on fats. (1) It splits up neutral fats and, assisted by the pancreatic juice, emulsifies and saponifies them. (2) It aids in the absorption of fats. The passage of digested food through membranes is assisted by wetting the membranes with bile or with a solution of bile salts. It is known that oil 1 This fine subdivision of fats gives the white color to the chyle, which is' its most striking external characteristic, the innumerable tiny oil drops reflecting all the light that falls on its surface. 2 See Summary at end of this chapter. ^ The color of bile is determined by the respective amounts of the bile pigments : (1) biliverdin, and (2) bilirubin, that are present. Chap. XV] DIGESTIVE PROCESSES 299 will pass to a certain extent through a filter paper, kept wet with a solution of bile salts, whereas it will not pass, or passes with extreme difficulty, through one kept wet with distilled water. (3) It has a feeble and questioned antiseptic action upon the intestinal contents, and its presence limits putrefaction to some extent. . (4) In addition to being a secretion, about one-sixteenth of the bile is an excretion, as it furnishes the channel by which the products of the disintegration of haemoglobin are carried from the body. (5) It acts as a mild laxative by stimulating peristalsis.^ Action of bacteria in small intestine. — Bacteria are constantly present in the small intestine, but only those capable of fermenting carbohydrate food show any activity. If the products of protein digestion are promptly absorbed, there is no fermentation of protein material. Various theories are offered to explain this protection of protein, but opinions differ, even among investigators. CHANGES THE FOOD UNDERGOES IN THE LARGE INTESTINE Movements of the large intestine. — After the food passes from the small intestine into the large intestine, its regurgitation is pre- vented by the closure of the ileo-csecal valve. When the caecum becomes filled, strong contractions of the walls exert pressure upon the contained food and force it into the ascending colon. The waves of contraction which pass over the walls of the ascending colon are described as antiperistaltic because they pass in two directions, (1) from the small intestine, and (2) toward the small intestine. This delays the food, keeps it moving backward and forward, and helps absorption. It has been estimated that it requires about two hours for the food to pass from the ileo-csecal valve to the hepatic flexure, and about four and one-half hours to reach the splenic flexure. Secretion of the large intestine. — The secretion of the large intestine is alkaline, contains much mucus, and does not contain any enzymes. Wlien the contents of the small intestine pass the ileo-caecal valve, they still contain a certain amount of unabsorbed food material. This remains a long time in the 1 Slow peristalsis will cause constipation, and is often associated with a torpid liver. As bile is a natural stimulant to the muscles of the bowel, an insufficient quantity may result in slow peristalsis. 300 ANATOMY FOR NURSES [Chap. XV intestine, and since it contains the digestive enzjines received in the duodenum, the process of digestion and absorption continues. By the abstraction of all the soluble constituents, and especially by the withdrawal of water, the liquid contents become, as they approach the rectum, changed into a firm and solid mass of waste matters, ready for ejection from the body, and calK-d feces. Action of bacteria in large intestine. — Protein putrefaction due to the action of bacteria is a constant and normal occurrence in the large intestine. A long list of end products result from this putrefaction. Some are given off in the feces, others are ab- sorbed and later excreted in the urine. The action of bacteria is considered of doubtful value. It is possible that they may act upon the cellulose of vegetable foods and render it useful in nu- trition. A conservative view is that bacteria confer no positive benefit, but under normal conditions the body is able to neutralize their action. The feces. — The feces consist of: (1) the undigested and indigestible parts of the food, (2) the products of bacterial de- composition, (3) great quantities of bacteria of difi'erent kinds, (4) bile and other secretions, (5) enzymes, and (6) inorganic salts. The color of feces is due to the presence of pigments derived from the bile. Defecation. — The anal canal is guarded by an internal sphincter muscle of the involuntary type, and an external sphincter that is voluntary, but both are supplied with nerves from the central nervous system and consequently defecation is a voluntary act. Normally the rectum is empty until just before defecation. Various stimuli (depending on one's habits) will produce peristaltic action of the colon, so that a small quantity of feces enters the rectum. This irritates the sensory nerve endings and causes a desire to defecate. The voluntary contraction of the abdominal muscles, the descent of the diaphragm, and powerful peristalsis of the colon all combine to empty the colon and rectum. One of the commonest causes of constipation is the retention of feces in the rectum because of failure to act on the desire for defecation. After feces once enter the rectum there is no retro- peristalsis to carry it back to the colon, and the sense of irritation becomes blunted. The desire may not recur for twenty-four hours, Chap. XV] DIGESTIVE PROCESSES 301 and during this time the feces continue to lose water, become harder, and more diflficult to expeL ABSORPTION This is the process by means of which the digested food is taken from the intestines and carried into the blood. We have now to consider this process, for, properly speaking, though the food may be digested and ready for nutritive purposes, it is, until it passes through the walls of the alimentary canal, still practically outside the body. Absorption. — Absorption is a very complex process and may be subdivided into a physical and physiological process. The physical process consists of the passage of the digested food from the intestines into the blood-vessels, and is governed by the laws of diffusion and osmosis. The physiological process consists in the building up of the end products of protein and fat digestion into the substances found in the blood. This process of reconstruc- tion is not understood, but is dependent on the living epithelial cells that make up the intestinal walls. Paths of absorption. — There are two paths by means of which the products of digestion find their way into the blood : — (1) By the capillaries in the walls of the stomach and intestines. (2) By the lymphatics in the walls of the small intestine (the lacteals) . It is now thought that absorption through the stomach is limited to small quantities of such substances as water, glucose, and salts. This means that the greater part of absorption is a function of the small and large intestines. The products that result from the digestion of proteins and carbohydrates pass into the capillaries. The products resulting from the digestion of fats pass into the villi of the small intestine. 302 ANATOMY FOR NURSES [Chap. XV SUMMARY Digestion — Is the process of changing food into products capable of absorption. Food — Substances that contain elements found in the body, or furnish material for production and repair of tissue, or yield energy. Classifica- tion Water . f Water. I Mineral matter or salts. ( Proteins. Organic \ Carbohydrates. [ Fats. H2O. About 66 per cent of body weight. Found in all tissues. ' Supplies fluid. Acts as solvent. Aids in elimination of waste. Mineral Matter ' of sodium and potassium. magnesmm. Proteins Chloride Phosphate Sulphate Carbonate , Phosphate 1 , , . , ^ , ^ ? of calcium and Carbonate J ' 1. To maintain alkalinity of body fluids. 2. To furnish material for acidity or alkaUnity of digestive fluids. Function { 3. To maintain osmotic pressure. 4. To enter into bones, teeth, and cartilage. 5. To influence elasticity and irritability of muscles and nerves. Consist of C, H, N, 0 ; S, P, and other elements may be present. Differ from carbohydrates and fats in having nitrogen. Albumins. Caseinogen. Examples I Gluten. Legumin. , Extractives. Chap. XV] SUMMARY 303 Carbohy- drates Fats ' Consist of C, H, and 0, the two latter in the proportion to form water. Include sugars and starches. j Glucose or dextrose C6H12O6 [ Invert . . , '1 Fructose or levulose C6H12O6 | sugar. chands I J Complex f Sucrose or cane sugar C12H22O11. or Disac- < Lactose or milk sugar C12H22O11. charids [ Maltose or malt sugar C12H22O11. ' Starch (C6Hio05)w. Poly sac- J Cellulose (C6Hio05)n. charids Glycogen (C6Hio05)n. . Dextrin (C6Hio05)/i. ' Consist of C, H, and 0. Made from one molecule of glycerine and three molecules of fatty acid. Fats are liquid at body temperature. Soluble in ether, chloroform, and hot alcohol. . Decompose to give glycerine and fatty acids. Organic foods are not soluble, hence necessity for digestion. Inorganic foods are soluble, and are absorbed directly. Mastication. Deglutition. Peristaltic action of oesopha- Mechanical I gus. Peristaltic action of stomach. Movements of intestines. Defecation. ' Splitting of complex molecules into simple ones, with ab- Chemical { sorption of water. Process of hydrolysis that is dependent on enzymes. An enzyme is produced by living cells and acts by catalysis. Enzymes { Its action is specific, it requires a medium of definite reac- tion, and the products must be removed. Digestion Processes 304 ANATOMY FOR NURSES [Chap. XV LIST OF DIGESTIVE FLUIDS AND CHIEF ENZYMES Digestive Fluids Enzymes Functions Saliva Ryalin Changes starch to dextrin and sugar (maltose). Gastric Juice Pepsin Changes proteins into proteoses and peptones in an acid medium. Gastric Juice Rennin Curdles the caseinogen of milk. Pancreatic Juice Trypsin Continues action of pepsin, splits proteoses into peptones and amino-acids. Requires al- kaline or neutral medium. Pancreatic Juice Diastase Changes starch to dextrin and sugar (maltose). Pancreatic Juice Lipase Splits fats to fatty acids and glycerine. Succus Entericus Erepsin Splits peptones into simplex products. Sucrase Changes sucrose to invert sugar. Succus Entericus Inverting < Maltase Changes maltose to dextrose. Lactase Changes lactose to dextrose. BUe No enzyme Splits fats into fatty acids and glycerine. Assist in saponifica- tion and aids in absorption. Mastication (chewing) . Insalivation (mixing with saliva). Secreted by sali vary glands Changes Food under- goes in Mouth Saliva and mucous I Submaxillary \ glands of I Subungual J mouth. L Reflex stimulation. 2. Psychical. Consists of water, mucus, and enzjTne — ptyalin. Specific gravity L004-1.00S. Alkaline reaction. One or two quarts in 24 hours. Result of Functions Deglutition (swallowing). 1. Assists in speech. 2. Assists in mastication deglutition. 3. Assists in taste. 4. Acts upon starch. and Chap. XV] SUMMARY 305 Stomach Digestion o H CO Gastric juice Peristaltic action of stomach. Time required for stomach digestion about 5 hours. Secretion of gastric juice \ ^^^ ]^^' [ Chemical — • Secretin. Secreted by glands of stomach ( ^^P*^^- I Pyloric. About 15 pints in 24 hours. Pale yellow liquid Acid reaction due to free hydrochloric acid. r Pepsin. Enzymes < Rennin. I Gastric lipase. Movements of small intestine ( Pen^^^l^ic. I Rhythmic segmentation. Secretion of pancreatic juice ( ^f^^^^.^^^)- I Chemical — secretin. Secreted by pancreas, discharged into small intestine during digestion. Pancreatic I Viscid fluid, alkaline reaction, juice 1 f Trypsin. Enzymes \ Diastase. I Lipase. Small Intestine Succus entericus Intestinal or Lieber- kuhn's. 2. Duodenal or Brun- Enzymes Bile Bacteria Secreted by glands found in intes- tines ner's. Yellowish fluid, alkaUne reaction. f Erepsin. I Inverting. ' Secreted by liver, stored in gall-bladder, dis- charged into small intestine during diges- tion. Golden brown or greenish liquid with alkaline reaction. About 1 quart in 24 hours. f 1. Splits up neutral fats. 2. Aids in absorption of fats. 3. Antiseptic action on intestinal Action Tinth, composed of a mass of tubes in the cortex, with a medullary ray for a centre. Equidistant from the ray on each side is a broken red line, marking the position of an interlobular artery. The parts between these lines constitute a lobule. Farther to the right is an interlobular artery, gi%'ing off lateral branches (afferent vessels), each of which ends in a tuft of capillaries, from which the blood is collected by an efferent vessel. The uppermost of the tufts is showti enclosed in a capsule. On the right of the interlobular artery the efferent vessels break up into a capillary network which surrounds the (unrepresented) tubes in the cortex and ray. The lowest efferent sends vertical vessels also into the medulla. On the right the interlobular vein is seen gathering the blood from all the parts sup- plied by the interlobular artery. A branch of the renal artery courses upward be- tween cortex and medulla, and forms an arch (here broken) over the base of the medulla. From it the inttrlol)\ilar arteries pass upward into the cortex, and straight branches go downward into the medulla, suppljing its structure, and end- ing at the apex in the capillaries. From the last the radicles of the renal vein arise, and accompany the straight arteries to the base of the medulla, where a %'e- nous arch is formed, continuous with which is the vena comes of the entering artery. The caljTC embraces the apex of the medullary pyramid. It is lined with epithe- lium, which continues from it ov^er the apex, the latter being perforated with the many apertures of excretory tubes. (Gerrish.) 328 Chap. XVII] URINARY SYSTEM 329 (1) When the arteries reach the level of the base of the pyra- mid, the branches divide laterally to form more or less com- plete arches between the cortex and medulla. From the arterial arches, vessels pass upward through the cortex (interlobular), giving off at intervals tiny arteries, each of which enters the dilated commencement or capsule of a uriniferous tubule. These tiny arteries, entering the capsule, are spoken of as afferent vessels. They push the thin walls of the capsule before them, break up into a knot of capillary vessels, called a glomer- ulus, and finally issue from the capsule as efferent vessels, near the point at which the afferent vessel entered. These efferent ves- sels are much smaller than the afferent ves- sels. They do not immediately join to form veins, but break up into a close meshwork or plexus of capillaries around the tubules, before they unite to form the larger vessels and pour their contents into the veins. These veins terminate in venous arches be- tween the cortex and medulla. It is in this way that the cortex is supplied with blood. (2) The pyramids also receive their blood supply from the arterial arches. The blood passes downward in straight vessels between the uriniferous tubules, to be re- turned by more or less straight veins to the venous arches, whence it is conveyed by large branches into the renal vein, which leaves the kidney at the hilus and pours its contents into the inferior vena cava. It is worthy of note that, unlike the lungs and the liver, the kidney receives blood from just one artery, and this blood distrib- uted in different sets of vessels serves the purposes of nourish- ment for the kidney substance, and the purposes of excretion. It is from the capillaries of the glomeruli and the plexus of capillaries around the convoluted portion of the tubules, that the passage of waste material from the blood into the tubule takes place. Other capillaries serve to hold the blood that is used for nourishment. Nerves and lymphatics. — The kidneys are well supplied with nerves derived from both the sympathetic and central nervous Fig. 168. — Plan of THE Blood-vessels con- nected WITH THE Tu- bules. (Note that in the text the term "renal or Malpighian corpuscles" is ussd instead of the term ' ' Malpighian body " which is found on the illustra- tion.) 330 ANATOMY FOR NURSES [Chap. XVII system. Many of these nerves are vasomotor nerves, and by regu- lating the contraction and relaxation of the blood-vessels, they in- fluence the blood pressure in the kidney. They are also well sup- plied with lymphatics. Function of the kidneys. — The function of the kidneys is to separate waste matters (urine) from the blood, and thus help to maintain the normal composition of the blood. The waste matters are those resulting from metabolism, particularly of proteins, water, salts, and foreign matters such as toxins, whether formed in the body, or taken into the body from outside. The secretion of urine. — The exact way in which the kidneys separate the urine from the blood is not known, but it is thought to be a double process, being partially accomplished by transuda- tion, and partially by the selective action of the secreting cells lining the tubules. (1) Into each hollow capsule which forms the beginning of a uriniferous tubule an afferent artery enters. This artery breaks up into capillaries which form a bunch of looped and twisted blood-vessels called a glomerulus. The walls of the capsule being double, the glomerulus pushes back the inner wall or visceral layer, until the capsule is entirely filled, leaving only a small space between it and the outer wall or parietal layer. The blood in the glomerulus is only separated from the interior of the tubule by the thin walls of the capillaries and the inverted wall of the capsule. The artery (afferent) which enters the capsule is larger than the issuing (efferent) vessel, and during its passage through the glomerulus, the blood is subjected to considerable pressure. As a result of this, a transudation of the watery constituents of the blood, with some dissolved salts, takes place through the walls of the blood-vessels and the walls of the capsule into the capsular space, then into the tubule. (2) After leaving the capsule, the efferent vessel communicates with other similar vessels, which together form a meshwork or plexus of capillaries closely surrounding the tubules, so that the blood is again brought into close communication with the in- terior of the tubules. The tubules are lined with secreting cells, and these cells appear to have the power of selecting from the blood the more solid waste matters (especially the urea), which fail to filter through the flat cells forming the wall of the capsule. Chap. XVII] URINARY SYSTEM 331 Fig. 169. — Diagram show- ing Method of Entrance of THE Ureter into the Bladder. (Gerrish.) THE URETERS The ureters are the excretory ducts of the kidneys. They con- sist of a distended portion called the pelvis, which is contained within the kidney, and a duct. Each duct is about the diameter of a goose-quill, and from twelve to eighteen inches (300 to 450 mm.) long. They consist of three coats : — (1) An inner or mucous coat con- tinuous above with that of the pelvis of the kidney, and below with that of the bladder. (2) A middle or muscular coat which is arranged in two layers, an inner longitudinal, and an outer cir- cular. (3) An outer or fibrous coat which carries the blood-vessels and nerves with which the tube is supplied. Function. — The ureters connect the kidneys with the bladder and serve as a passageway to convey urine from the kidneys to the bladder. BLADDER The bladder is a hollow muscular organ situated in the pelvic cavity behind the pubes, in front of the rectum in the male, and in front of the anterior wall of the vagina, and the neck of the uterus, in the female. It is a freely movable organ, but is held in position by ligaments. During infancy it is conical in shape and projects above the upper border of the pubes into the hypogastric region. In the adult, when quite empty, it is placed deeply in the pelvis ; when slightly distended, it has a round form ; but when greatly distended, it is ovoid in shape and rises to a considerable height in the abdominal cavity. It is customary to speak of the widest part as the fundus, and the part where the bladder becomes continuous with the urethra as the neck, or cervix. It has four coats : — 1. The mucous membrane lining the bladder is continuous with that of the ureters and the urethra. When the bladder is empty, the mucous membrane is thrown into irregular rugae. 332 ANATOMY FOR NURSES [Chap. XVll 2. The areolar coat connects the mucous and muscular. It permits freedom of movement such as is essential in an organ subject to change in size and shape. 3. The muscular coat has three layers, an inner longitudinal, middle circular, and outer longitudinal. The circular fibres are collected into a layer of some thickness around the cervix or neck, where the bladder becomes continuous with the urethra. These circular fibres around the neck form a sphincter muscle which is normally in a state of contraction, only relaxing at intervals, when the accumulation of urine within the bladder renders its expulsion necessary. 4. The serous coat is a reflection of the peritoneum, and only covers the upper portion of the fundus. Function. — The bladder serves as a reservoir for the reception of urine. When moderately distended, it holds about one pint (about one-half litre). THE URETHRA The urethra is a narrow, membranous canal, about an inch and a half (38 mm.) in length in the female. Its normal diameter is about one-quarter of an inch (6.3 mm.), but it admits of consid- erable dilatation. It extends from the neck of the bladder to the external orifice, which is named the meatus urinarius. It is placed behind the symphysis pubis, and is embedded in the anterior wall of the vagina. Its direction is obliquely downward and forward, its course being slightly curved, with the concavity directed for- ward and upward. Its external orifice is the narrowest part and is located between the clitoris and the opening of the vagina. (See Fig. 207.) The wall of the urethra consists of three coats : — (1) An inner or mucous coat which is continuous with that of the bladder. (2) A submucous coat which contains a network of veins. (3) An outer muscular coat which is continuous with that of the bladder. MICTURITION Urine is secreted continuously by the kidneys. It is carried to the bladder by the ureters, and at intervals is expelled from the Chap. XVII] URINARY SYSTEM 333 bladder through the urethra. The act by which the urine is ex- pelled is called micturition. It occurs normally as the result of irritation due to the accumulation of urine within the bladder. The accumulation stimulates the muscular walls to contract, and the resistance of the sphincter at the neck of the bladder is over- come. The action is involuntary, but it may be controlled by vol- untary effort. Involuntary micturition. — Involuntary micturition may occui as the result of lack of consciousness ; and as the result of spinal injury involving the nerve centres, which send nerves of control to the bladder. It may be due to a want of " tone " in the muscu- lar walls, or it may result from some abnormal irritation. Retention of urine. — When the kidneys secrete urine, but it is retained within the bladder, we speak of it as retention. Reten- tion or failure to void urine may be due to : (1) dulling of the senses so that there is no desire to void, (2) nervous contraction of the urethra, and (3) some obstruction in the urethra or in the neck of the bladder. In some cases the bladder may become so fully distended that the retention of urine may be accompanied by more or less con- stant voiding of small amounts of urine. Suppression of iirine. — When the kidneys fail to secrete urine, it is spoken of as suppression, and is a far more serious condition than retention, as it is usually due to disease of the kidneys. GENERAL CHARACTERS OF THE URINE Normal urine may be described as a transparent, amber-colored liquid, with a characteristic odor, an acid reaction, and a specific gravity of about 1.020. Transparency. — The transparency of urine may be diminished in health by the presence of mucus, derived from the genito- urinary tract, or by the deposit of salts. In disease the urine may become clouded by the presence of pus. Color. — The color of urine depends upon the quantity voided and the relative amounts of water and coloring matters. If the quantity is abnormally increased, it is usually more dilute and of a paler color; as, for instance, the copious light-colored urine of hysteria or diabetes insipidus. One exception to this is diabetes mellitus, where the quantity is increased, but the color is dark 334 ANATOMY FOR NURSES [Chap. XVII because of the presence of sugar. When the quantity is diminished, as in fevers, it is generally highly colored, because the amount of solids present is large. Other causes of change of color are the presence of abnormal substances, and large doses of certain drugs. Reaction. — The reaction of human urine is largely dependent on the kind of food we eat. Many of the waste products that result from a mixed diet are acid, hence the reaction of human urine is usually acid. On a diet of carbohydrates the urine will be alka- line, as it is with herbivorous animals. If human urine is allowed to stand for any length of time, it will become alkaline, because bacteria will decompose the protein constituents into ammonia and other alkalies. In certain diseased conditions of the urinary organs this same process takes place within the body. Specific gravity. — The specific gravity depends upon the amount of solid waste matters present in the urine. In health, it may vary from 1.010 to 1.030. When the solids are dissolved in a large amount of water, the specific gravity will naturally be lower than when, from a deficiency of water, the urine is more concentrated. A high specific gravity denotes the presence of abnormal constituents ; as, for instance, the specific gravity is not- ably heightened by the presence of sugar in diabetes mellitus. A low specific gravity generally denotes the presence of albumin, or hysteria or mere polyuria. Quantity. — The average quantity of urine secreted in twenty- four hours by a healthy adult is from forty to fifty ounces (1.19 to 1.48 litres). A child voids relatively more urine than an adult, but absolutely it voids less. From 2-5 years, 16-24 ounces. ' From 5-8 years, 24-32 ounces. From 9-16 years, 32-40 ounces. The quantity of urine may be increased by (1) the ingestion of a large amount of liquids, (2) the action of diuretics, (3) nervous- ness, (4) certain diseases such as diabetes insipidus, diabetes mellitus, and hysteria. The quantity of urine may be decreased by (1) the ingestion of a small amount of liquids, (2) vomiting, (3) diarrhoea, (4) high fever, (5) disease of the kidneys, and (6) the action of diapho- retics, muscular activity, or any treatment that induces free per- spiration. Chap. XVII] URINARY SYSTEM 335 COMPOSITION OF URINE The composition of urine is very complex; even in health it varies, depending on the quantity and kind of food eaten, etc. The chief constituents are as follows : — Urine Water, 95 per cent Solids, 5 per cent Organic, about 3.7 Inorganic, about 1.3 Urea (2 per cent of total solids). Uric acid. Creatinin. Hippuric acid. Other substances. Sodium chloride. Sulphates. Phosphates. Potassium. Ammonimn. Magnesiimi. Calcium. Other substances , Salts of Urea. — Urea constitutes about one-half of the solid constitu- ents of the urine, and represents the chief end product resulting from the metabolism of the proteins of the food and tissues. The result of the oxidation of protein material exists in the blood until the blood reaches the liver. Under the action of the liver cells this material (ammonium carbamate) is converted into urea and remains in the circulation until the blood reaches the kidneys. To eliminate urea is the special work of the kidneys, and if for any reason they fail to execute their work, the accumulation of urea in the system leads to a condition of poisoning. Normally an adult voids about one ounce (30 gm.) in twenty- four hours, but the quantity is increased by a diet rich in proteins, strenuous exercise, fever, and some diseases. A small amount of protein food, excessive vomiting, free perspiration, and diseases that interfere with elimination will decrease the amount of urea voided. Uric acid. — Uric acid is thought to represent the end products resulting from the oxidation of the tissues, and next to urea is the medium by which nitrogen is eliminated from the body. Uric acid combines with potassium and sodium to form urates, and is found in the form of urates in the urine. In gout the excretion of 336 ANATOMY FOR NURSES [Chap. XVII urates is decreased, and it accumulates in the blood and is deposited in the tissues. Creatinin. — Creatinin represents a meat extractive and may be taken into the body in food, or formed in the body by the oxida- tion of certain proteins. Hippuric acid. — This is increased in amount by a vegetable diet, so that it is thought to represent a waste product that results from the metabolism of vegetables. However, some hippuric acid is excreted even on a meat diet, so that it may result from the metabolism of proteins, or it may be derived from the jjrocess of protein putrefaction that occurs in the intestines. Salts. — The salts found in the blood are derived partly from the food eaten, and partly from the metabolism of proteins, particu- larly the neutralization of acids. Sodium chloride is the most abundant, and, next to urea, is the chief solid found in urine. In certain inflammatory conditions, coupled with serous exudate, the amount of sodium chloride excreted is very much diminished. Abnormal constituents. — The chief abnormal constituents that are liable to appear in the urine are albumin, glucose, indican, acetone, casts, calculi, pus, and blood. Albumin. — Normally the kidney cells do not allow albumin to pass into the tubules, but a condition of temporary albuminuria may follow overeating or severe muscular exercise. In abnormal conditions of the kidneys associated with nephritis and acute fevers, albumin is usually found in the urine. In cases of heart disease, where the blood vessels of the kidney are subjected to ab- normal pressure changes, albumin is usually present in the urine. Glucose. — In health the amount of glucose present in the blood varies from 0.1 to 0.15 per cent. A higher per cent is irritating to the tissues, so when the quantity of sugar eaten is greater than the system can promptly change to glycogen and fat, the kidneys secrete and excrete it. When glucose is found in the urine from this cause, it is called temporary glycosuria. Temporary glycosuria frequently follows an injury to the head, or occurs during convales- cence from fevers. In these cases it is thought to be due to tem- porary inability of the system to oxidize sugar. In the disease called diabetes mellitus glucose persists in the urine. In mild cases this condition can be controlled by lessening the amount of carbohydrate food, but in severe cases glucose will appear in the Chap. XVII] URINARY SYSTEM 337 urine even when no carbohydrates are eaten. This condition is serious because it means that the body tissues are being oxidized to form glucose. The cause of diabetes meUitus is not definitely known. It frequently follows injuries to the head, and is asso- ciated with disease of the pancreas, which interferes with the in- ternal secretion. Indican. — Indican is a substance that is formed from indol. Indol results from the putrefaction of protein food in the large intestine. It is absorbed and carried to the liver, which it is thought changes the indol to indican, a less poisonous substance. Traces of indican are found in normal urine, but the presence of it in any amount is abnormal and denotes : (1) excessive putrefaction of protein food in the intestines, or (2) disease of the stomach. (1) Excessive putrefaction may be due to a diseased condition of the intestine that interferes with absorption, to a diet containing too much protein food, or to constipation. (2) In certain diseases of the stomach, food is held until it undergoes fermentative changes. Acetone. — Acetone is a volatile substance that is thought to be the result of incomplete oxidation of fats and possibly of pro- teins. It is found in the urine of individuals suffering from defec- tive metabolism, and in the urine of normal individuals during periods of fasting. Casts. — In some abnormal conditions the kidney tubules be- come lined with substances which harden and form a mould or cast inside the tube. Later these casts are washed out by the urine, and their presence in urine can be detected by the aid of a micro- scope. They are named either from the substances composing them or from their appearance. Thus there are (1) pus casts, (2) blood casts, (3) epithelial casts from the walls of the tubes, (4) granular casts from cells which have decomposed and form masses of granules, (5) fatty casts from cells which have become fatty, and (6) hyaline casts which are formed from coaguiable elements of the blood. Calculi. — A deposit of solid matter that has been precipitated from the urine is called a urinary calculus or stone. They vary in size, shape, and composition, the size and shape being determined largely by their composition and location. They may be formed in any part of the urinary tract from the tubules to the external orifice of the urethra. The causes which lead to their formation 338 ANATOMY FOR NURSES IChap. XVII are (1) an increase in the slightly soluble constituents of the urine, (2) a decrease in the amount of water secreted, and (3) abnor- mally acid or abnormally alkaline urine. Pus. — In suppurative conditions of any of the urinary organs pus cells are present in the urine. Blood. — In cases of acute inflammation of any of the urinary organs, of tuberculosis, of cancer, and of renal stone, red blood corpuscles may be found in the urine. If present in large numbers, they make the urine look like blood, and this condition is known as hematuria. Toxicity of urine. — As urine is the medium by which the body gets rid of toxic material, it follows that urine itself is toxic, and must be eliminated, else a condition of toxemia will result. This condition is called uremia, because it was thought that the symp- toms of poisoning were due to the retention of urea in the body. It is now believed that while urea is poisonous, it is only one of several substances that renders urine toxic. During illness the kidneys always try to eliminate any poisonous substances that find their way into the blood, whether these substances are derived from defective metabolism or from bacterial activity. This ac- counts for the fact that after a severe illness the kidneys are often left in a damaged condition. Waste Prod- ucts or Excreta Excretory Organs SUMMARY Urea. Uric acid. Creatinin. Hippuric acid. Carbon dioxide. Other organic substances. Inorganic salts. Water. Urinary system Assist in excretion Kidneys (2) — secrete urine. Ureters (2) — ducts which convey urine from kidneys to bladder. Bladder (1) — reservoir for urine. Urethra (1) — tube through which urine is voided. Lungs. Skin. Liver. Intestines. Chap. XVII] SUMMARY 339 Location ' Posterior part of lumbar region, behind peritoneum. Placed on either side of spinal column and extend from upper border of twelfth thoracic to third lumbar vertebra. Q ^ Uriniferous tubules Capsule and j Covered by tough envelope of fibrous tissue. supports \ Supported by quantity of fat, vessels, and peritoneum. Four inches long, two inches broad, one inch thick. Weight, four and one half ounces (140 gm.). Size and J Bean-shaped, tubular glands. shape 1 Concave side toward spine, convex side outward. Hilum — depression near centre of concave side serves for vessels to enter and leave. Pelvis — Upper expanded end of ureter. Calyces — Cup-like cavities of the pelvis that receive papillae of pyramids. Cortex — ■ outer, lighter, more solid portion. Medulla — inner, darker, striated portion. ' Begin as hollow globes or capsules in the cortex of kidney, and after a very ir- { regular course open into straight col- lecting tubes which pour their contents into calyces of pelvis. Cone-shaped masses in the medullary portion of the kidney. Vary in num- ber from 8-12. Anatomy Bases directed toward cortex. of the i Pyramids < Papillae — Apices of the pyramids, di- kidney rected toward pelvis. Consist of uriniferous tubules, blood- vessels, and l}Tnphatics, held together by connective tissue. (Minute tufts of capillaries — glomeruli — in the cortical portion of kidneys which are surrounded by inverted cap- sule of uriniferous tubule. ' Renal artery — direct from aorta. Enters hilus of kidney, divides into many branches. C Lateral branches at the level of the base of the pyramids. Blood supply Arterial arches 1. Send branches to cortex (cortical) . . 2. Send branches to pyramids. 340 ANATOMY FOR NURSES [Chap. XVll Anatomy of the kidney Blood supply Nerves and lymphat- ics Function Ureters Bladder Lateral branches at level of Venous j base of pyramids, arches i Receive blood from cortex. i Receive blood from pyramids. Veins empty into renal vein, leave kidney at hilus, and empty into in- ferior vena cava. Note — Blood from renal artery serves for purposes of nourishment of kidney and purposes of excretion. Nerves from sjTnpathetic and central nervous system. Many are vasomotor, and by regulating size of blood-vessels, influence blood pressure. Well supplied with IjTnphatics. 1. Process of transudation or filtration. Water and saline elements are fil- tered from the blood during the cir- culation through the glomeruli. 2. Secretory action of the cells lining the uriniferous tubules. Urea and other foreign substances are sepn arated from the blood during the circulation through the plexus of capillaries which surrounds the tubules. Excretory ducts. Extend from kidney to bladder. Consist of expanded portion called pehas and duct. Size of goose-quill. 12-18 in. long. C 1. Mucous — lining. ' 2. Muscular 1 1^""'"' l«"gitudinal layer. I Outer, circular layer. 3. Fibrous — carries blood-vessels and nerves. r Connect kidneys with bladder. \ Passageway for urine. Hollow muscular organ. in front of rectum in male, in front of anterior wall of Secretion of urine Three coats Function Situated in pelvic cavity behind the pubes vagina and neck of uterus in female. Chap, XVII] SUMMARY 341 Four coats Function Freely movable. Held in position by ligaments. Size, shape, and position depend upon age, sex, and whether bladder is full or empty. Fundus — widest part. Cervix — where the bladder becomes contmuous with the urethra. 1. Mucous — lining. Bladder j 2. Areolar — connects mucous and muscular. f Inner layer — longitudinal. 3. Muscular Middle layer — circular. [ Outer layer — longitudinal. 4. Serous — partial covermg derived from peri- toneum. r Serves as a reservoir for the reception of urine. j When moderately distended, holds about one [ pint. ' Membranous canal, extends from the bladder to the meatus urinarius. li in. long and i in. in diameter in female. Behind symphysis pubis, and embedded in the anterior wall of vagina. Urethra I f 1. Mucous — lining. 2. Submucous — supports network of veins. 3. Muscular | ^''''^^ ~ longitudinal. I External — circular. Meatus urinarius — external orifice located between cU- toris and vagina. Act of expelling urine from bladder. Micturition I Occurs as result of irritation due to accumulation of urine in bladder. Involuntary act — can be controlled by voluntary effort. Failure to void urine. ' 1. DuUing of the senses. Due to j 2- Nervous contraction of urethra. 3. Some obstruction in urethra or neck of bladder. May be accompanied by overflow or constant voiding of small amounts. Suppression — Failure of the kidneys to secrete urine. Transparency — depends on absence or presence of mucus and pus. Color — depends on concentration. Relative amoimts of water and solids. Reaction — usually acid. Specific gravity — average 1.020. Depends on concentra- tion. Three coats Retention Characters of Urine 342 ANATOMY FOR NURSES [Chap. XVII Characters of Urine Average 40 to 50 ounces. Action of diuretics. Nervousness. ' Diabetes in- Quantity ■ Increased by Decreased by Urine Water, 95 per cent Solids, 5 per cent Organic, about 3.7 Inorganic, about 1.3 sipidus. Certain disease i Diabetes mel- litus. , Hysteria. Ingestion of small amounts of water. Vomiting, diarrhoea. High fever. Disease of kidneys. Increased action of skiu. Urea (2 per cent of total solids). Uric acid. Creatinin. Hippuric acid. Other substances. Sodium chloride. Sulphates. Salts of Urea Phosphates. Potassium. Ammonium. Magnesimn. Calcium. Other substances. End product resulting from metabolism of proteins. Average excreted in twenty-four hours — 1 ounce. Increased ( ^'^^ "^^^ ^^ proteins. 1^ < Strenuous exercise. I Fever, and some diseases. T^ I ( Small amount of protein food. Decreased \ ^ . -x- r • x- < Excessive vomitmg, free perspiration. I Diseases that interfere with elimination. by Uric acid Creatinin Hippuric Acid r End product resulting from oxidation of tissues. < Combines with potassium and sodium to form urates. I Failure to excrete results in gout. f May be taken into body in food. I Formed in body by oxidation of certain proteins. IMay be derived from oxidation of proteins. Maj' result from putrefactive processes in the intestines. Increased by a vegetable diet. Chap. XVII] SUMMARY 343 Salts Abnormal Constitu- ents r Derived from food eaten. I Derived from neutralization of acids. I Sodium chloride is most abundant. Albumin. Glucose. Indican. Acetone. Casts. Calculi. Pus. I Blood. CHAPTER XVIII THE SKIN; APPENDAGES OF THE SKIN. PRODUCTION OF HEAT; REGULATION OF HEAT. VARIATIONS IN TEMPERATURE THE SKIN Functions. — The skin is not, like the kidneys, set apart to per- form one special function. It serves: (1) as a protective cover- ing for the deeper tissues lying beneath it, (2) as a sense organ, (3) as an excretory organ, (4) as an absorbing organ, (5) as an important organ in heat regulation, and (6) as a respiratory organ. Structure. — It consists of two distinct layers : — (1) Epidermis, scarf skin, or cuticle. (2) Derma, cutis vera, or corium. Epidermis. — The epidermis is a stratified epithehum, com- posed of a number of layers of cells. The thickness varies in different parts of the body, measuring in some places not more than oi^ inch (0.104 mm.), and in others as much as o^ inch (1.04 mm.). It is thickest in the palms of the hands and on the soles of the feet, where the skin is most exposed to friction, and thinnest on the ventral surface of the trunk, and the inner surfaces of the limbs. It forms a protective covering over every part of the true skin, upon which it is closely moulded. It is roughly divisible into two layers : — (1) Upper, or Horny. (2) Germinative, or Malpighian. (1) The horny layer consists of three strata of cells, which are practically dead, and are constantly being shed and renewed from the cells of the germinative layer. (2) The germinative layer consists of soft protoplasmic cells. The growth of the epidermis takes place by the multiplication of these cells. As they multiply they push upward toward the surface those previously formed. In their upward progress they undergo a chemical transformation, and the soft proto- plasmic cells become converted into the flat, horny scales which 344 Chap. XVIII] THE SKIN 345 are constantly being rubbed off the surface of the skin. The pig- ment in the skin of the negro, as well as that of the nipple in white races, is found in the deepest cells of the germinative layer.' No blood-vessels pass into the epidermis ; it, however, receives fine nerve-fibrils between the cells of the germinative layer. Horny < corneum stratum lucidum stratum -ranulos.uin O. or M/ > Germinative or Malpighian ■m. ^e ,4^; ^X'i Fig. 170. — Vertical Section throttgh the Skin of the Palmar Side of THE Finger, showing Two Papill.e (One of which contains a Tactile Cor- puscle) AND the Deeper Layer of the Epidermis. (Schafer.) Derma. — The derma is a highly sensitive and vascular layer of connective tissue. It is described as consisting of two layers : — (1) Superficial, or papillary layer. (2) Deeper, or reticular layer. (1) The surface of the papillary layer is increased by protru- sions in the form of small conical elevations, called papillse, whence this layer derives its name. They project up into the epidermis, which is moulded over them, and contain for the most part looped blood-vessels, but they also contain the terminations of nerve- fibres in the shape of little bodies called tactile corpuscles. 34G ANATOMY FOR NURSES [Chap. XVIII The papillae seem to exist chiefly for the purpose of giving the skin its sense of touch, being always well developed where the sense of touch is exquisite. They are specially large and numerous on the palm of the hand and the tips of the fingers, and on the cor- responding parts of the foot. (2) The reticular layer of the corium is a continuation of the papillary layer, there being no real division between them. It is made up of bundles of white fibrous and elastic tissue. The derma is attached to the parts beneath it by a layer of areolar tissue, here named subcutaneous, which layer, with very few exceptions, contains fat. The connection in some parts is loose and movable, as on the front of the neck ; in others, close and firm, as on the palmar surface of the hand and the sole of tlic foot. Blood-vessels. — The blood-vessels of the skin are found in the derma only. They form a network of capillaries in which the ves- sels are very close to each other, and send branches to the papilhe and glands of the skin. The capillaries of the skin r.re capable of holding from one-half to two-thirds of the blood contained in the body. The amount of blood they contain is dependent on their calibre, and this is regulated largely by the vasomotor nerves. Nerves. — The skin is provided with a great variety of nerves. They are classified as follows : — (1) Vasomotor nerves, which are distributed in the walls of the blood-vessels. (2) Two sets of nerves concerned in the temperature sense, which terminate in the hot and cold spots of the skin. (3) The nerves concerned in the sense of touch or pressure. (4) Nerves which are stimulated by pain. (5) Motor nerves, which are derived from the sympathetic sys- tem and distributed to the glands and the arrector muscles. Nearly every nerve centre in the body may be affected by sensa- tions arising in the skin, because of the number of afferent nerves which lead from the skin to centres in the brain and spinal cord. It is for this reason that hydrotherapeutic applications, heat, cold, and counter irritants excite so many and such varied reflexes. Chap. XVIII] THE SKIN 347 LUNULA.. ^ Fig. 171. — Thumb-nail. (Geirish.) THE APPENDAGES OF THE SKIN The appendages of the skin are the nails, the hair, the sebaceous glands, the ceruminous glands, and the sudoriferous or sweat-glands. The nails. — The nails are composed of clear, horny cells of the epidermis, joined together so as to form a solid, continuous plate. Each nail is convex on its outer surface, concave on its inner side, and closely adherent to the underlying derma, which is modified to form what is called the bed, or matrix, of the nail. At the hinder part of the bed of the nail the skin forms a deep fold, in which is lodged the root of the nail. The growth of the nail is accomplished by constant multiplication of the soft cells in the germinative layer at the root. These cells are transformed into dry, hard scales, which unite into a solid plate, and the nail, constantly receiving additions from below, slides forward over its bed and projects beyond the end of the finger. When a nail is thrown off by suppuration or torn oft' by violence, a new one will grow in its place provided any of the cells of the germinative layer are left. The hair. — The hair is a growth of the epidermis, developed in little pits, the hair- follicles, which extend downward into the deeper part of the true skin, or even into the subcutaneous tissue. The hair grows from the bottom of the little pit or follicle. The part which lies within the follicle is known as the root, and that portion which projects beyond the surface of the skin is called the shaft or stem. The substance of the hair is composed of coalesced, horny cells, arranged in different layers, and we usually distinguish three parts in the stem or shaft of a hair : — (1) Cuticle — an outer layer of delicate, scale-like cells. (2) Fibrous substance — a middle, horny, thick portion, formed Fig. 172. — Piece of Human Hair. (Highly magnified.) a, cuticle ; b, fibrous substance ; c, medulla. 348 ANATOMY FOR NURSES [Chap. XVIII of elongated cells. These cells and the intercellular spaces contain a varying amount of pigment, and the color of the hair depends upon the quantity. The gray hair of old age is produced by loss of pigment. (3) Medulla — a central pith formed of round cells. Minute air bubbles may be present in both the medulla and fibrous layer, and cause the hair to look white by reflected light. The root of the hair is enlarged at the bottom of the follicle into a bulb or knob. This bulb is composed of soft-growing cells, and fits over a vascular papilla which projects into the bottom of the follicle. Hair has no blood-vessels but receives nourishment from the blood vessels of the papilla. Growth of hair. — Hair grows from the bottom of the follicle by multiplication of the soft cells which cover the papilla. These cells become elongated to form the fibres of the fibrous portion, and as they are pushed to the surface, they become flattened and form the cuticle. If the scalp is thick, pliable, and moves freely over the skull it is favorable to the growth of hair. A thin scalp that is drawn tightly over the skull tends to constrict the blood- vessels, lessen the supply of blood, and cause atrophy of the roots of the hair by pressure. In such cases massage of the head loosens the scalp, improves the circulation of the blood, and usually stimu- lates the growth of hair. With the exceptions of the palms of the hands, the soles of the feet, and the last phalanges of the fingers and toes, the whole skin is studded with hair. The hair of the scalp is long and coarse, but most of the hair is very fine and extends only a little beyond the hair follicle. Arrector muscles. — The follicles containing the hairs are narrow pits which slant obliquely upward, so that the hairs they contain lie down on the surface of the body. Connected with each follicle is a small muscle called the arrector muscle. It is composed of bundles of plain muscular tissue which pass from the surface of the true skin, on the side to which the hair slopes, obliquely downward, to be attached to the bottom of the follicle. When these muscles contract, as they will under the influence of cold or terror, the little hairs are pulled up straight, and stand " on end " ; the follicle also is dragged upward, and in this way the roughened condition of the skin known as " gooseflesh," is produced. Chap. XVIII] THE SKIN 349 Sebaceous glands. — The sebaceous glands are small, saccular glands, which lie between the hairs and their arrector muscles. They occur everywhere over the skin surface, with the exception of the palms of the hands and the soles of the feet. Each gland consists of a collection of small tubes overspread with a network of capillaries. From the gland a small duct as- cends, and opens either upon the surface of the skin or, as is more SUBCUTANEOUS AREOLAR TISSUE DUCT OF SEBACEOUS GUND T— ROOT OF HAIR HAIR FOLLICLE — -ADIPOSE TISSUE BULB OF HAIR PAPILLA OFHAIB ARRECTOR MUSCLE Fig. 173. — Vertical Section of the Skin, showing Sebaceous Glands, Sweat-glands, Hair, and Follicle, also Arrector Muscle. (Gerrish.) common, into a hair follicle. Their size is not regulated by the length of the hair. Thus, some of the largest are found on the nostrils and other parts of the face, where they often become en- larged with pent-up secretion. Sebum. — The secretion of the sebaceous glands is called sebum. It contains fats, soaps, epithelial cells, albuminous matter and inorganic salts. It serves to remove waste matters and is classed as an excretion, but its more important purposes are to keep the skin and hair soft and pliable, and to form a protective layer on 350 ANATOMY FOR NURSES [Chap. XVIII the surface of the skin. An accumulation of this sebaceous matter upon the skin of the foetus furnishes the thick, cheesy, oily sub- stance called the vemix caseosa. Ceruminous glands. — The skin lining the external auditory canal contains modified sweat glands called ceruminous glands. They secrete a yellow, pasty substance resembling wax which is called cerumen. Sweat-glands. — The sweat-glands are simple, convoluted, tubu- lar glands with the blind ends coiled into little balls which are lodgetl in the true skin or subcutaneous tissue ; from the ball the tube is con- tinued as the excretory duct of the gland up through the true skin and epidermis, and finally opens on the surface by a slightly widened orifice called a pore. Each tube is lined by a secreting epi- thelium continuous with the epidermis. The coiled end is closely invested by a meshwork of capillaries, and the blood in the cap- illaries is only separated from the cavity of the glandular tube by the thin membranes which form their respective walls. The secre- tory apparatus in the skin is somewhat similar to that which obtains in the kidneys; in the one case the blood-vessels are coiled up within the tube, while in the other the tube is coiled up within the meshwork of blood-vessels. The sweat-glands are abundant over the whole skin, but they are largest and most numerous in the axillae, the palms of the hands, soles of the feet, and the forehead. Perspiration, or sweat. — The sweat is a watery, colorless liquid, slightly turbid, of a salty taste, with a strong, distinctive odor and an acid reaction. It is an excrement, the chief normal constituents of which are water, salts, fatty acids, a small quantity of carbon dioxide, and a slight amount of urea. In vari- FiG. 174. — Coiled End of a Sweat-gland. a, the coiled end ; b, the duct ; c, network of capillaries, inside which the sweat-gland lies. Chap. XVIII] THE SKIN 351 ous forms of kidney disease urea may be present in considerable quantity, the skin supplementing to a certain extent the deficient work of the kidneys. Quantity of perspiration. — Under ordinary circumstances, the perspiration that we are continually throwing off evaporates from the surface of the body without our becoming sensible of it, and is called insensible perspiration. When more sweat is poured upon the surface of the body than can be removed at once by evaporation, it appears on the skin in the form of drops, and we then speak of it as sensible perspiration. The average amount discharged during twenty-four hours is about one quart (0.946 litre), but it may be increased to such an extent that even more may be discharged in an hour. The secre- tion of sweat is increased by: (1) a dilute condition of the blood, such as results from drinking large quantities of liquids, (2) in- creased temperature or humidity of the atmosphere, (3) exercise, (4) pain, (5) mental excitement or nervousness, (6) dyspnoea, (7) use of diaphoretics, (8) certain diseases such as tuberculosis, acute rheumatism, and malaria, (9) use of electricity to stimulate the secretory nerves. The secretion of sweat is decreased by: (1) voiding of a large quantity of urine, (2) cold, (3) diarrhoea, (4) certain drugs, and • (5) certain diseases, such as fevers, diabetes, and some cases of paralysis. Activity of the sweat-glands. — The activity of the sweat-glands is supposed to be due to direct stimulation of the nerve endings in the glands, or indirect stimulation of the nerve centres controlling perspiration. An increase in perspiration following an increase in the temperature or humidity of the atmosphere is partly due to stimulation of the nerve endings in the sweat-glands, and partly due to the stimulation from the sensory nerves being carried to the nerve centres, and transmitted along motor nerves to the gland. The activity is also influenced by the vasomotor nerves, which control the size of the blood-vessels in the skin ; an increase in the size of the vessels leads to increased, a constriction of the vessels to diminished, perspiration. That this is not the only factor is proven by the profuse perspiration that often accompanies a pallid skin, or the absence of perspiration that is characteristic of fever. 352 ANATOMY FOR NURSES [Chap. XVIII Excretory function of the skin. — While sweat is an excretion, its value lies not so much in the elimination of waste matter as in the loss of body heat by the evaporation of water. This loss of heat is necessary to balance the production of heat that is con- stantly taking place. Less important functions of the skin. — The skin is to a slight extent an absorbing organ. Soluble substances are very readily absorbed if the epidermis is removed, but even when in solution they are sparingly absorbed by the unbroken skin. Oily sub- stances, if well rubbed in, are readily absorbed, especially in those parts of the body where the epidermis is thinnest. Oxj'gen in small amount is also taken in through the skin, but this gain to the body is counterbalanced by the carbon dioxide which is thrown off. BODY HEAT From the standpoint of heat, production animals may be divided into two great classes : — (1) Constant temperature animals, or those whose temperature remains practically constant whether the surrounding air is hotter or cooler than the body. The term warm-blooded is also applied to this class. It includes human beings. (2) Changeable temperature animals, or those whose tempera- ture varies with that of the surrounding medium. This class is also described as cold-blooded. The human foetus is cold-blooded. The great difference between these two classes is in their reac- tions to external temperature. A cold environment reduces the temperature of the cold-blooded creature, reduces the metabolism of all its tissues, and thus reduces its heat production. The warm-blooded animal reacts in precisely the opposite way. Since his temperature remains constant, his heat production must in- crease in order to neutralize the effect of cold surroundings. Production of heat. — Heat in the body is produced by such chemical changes going on in the tissues as are associated with oxidation. Friction is a minor source of heat, i.e. that caused by the movements of the muscles, the circulation of the blood, and the ingestion of warm food. Where heat is produced. — Wherever metabolic changes are taking place, there heat is set free. These changes take place Chap. XVIII] BODY HEAT 353 more rapidly in some tissues than in others, and in the same tissues at different times. The muscles always manifest a far higher rate of activity than the connective tissues, and consequently the former evolve a larger proportion of the bodily heat than the latter. We might liken the different tissues of the body to so many fire- places stored with fuel, the fuel in some of the fireplaces being more easily ignited and burning more rapidly than in others. The muscles and the secreting glands, especially the liver, are sup- posed to be the main sources of heat, as they are the seats of a very active metabolism. Loss of heat. — The heat thus continually produced is as con- tinually leaving the body by the skin and the lungs, and by the urine and feces. It has been calculated that in every 100 parts about : — 88 per cent is lost by conduction and radiation from the sur- face of the skin and the evaporation of the perspiration. 9 per cent is lost by warming the expired air and the evapora- tion of the water of respiration. 3 per cent is lost by warming the urine and feces. The temperature and humidity of the atmosphere may cause considerable difference in the per cents given above. A low tem- perature will increase the loss of heat by radiation and decrease that by evaporation. A high temperature will decrease the loss of heat by radiation and increase that by evaporation owing to the greater production of sweat. From the above figures it is evident that the skin is the important factor in getting rid of body heat. This is due: (1) to the large surface offered for radiation, conduction, and evaporation ; and (2) to the large amount of blood which it contains. Distribution of heat. — The blood, as we know, permeates all the tissues in a system of tubes or blood-vessels. Wherever oxidation takes place and heat is generated, the temperature of the blood circulating in these tissues is raised. Wherever, on the other hand, the blood-vessels are exposed to evaporation, as in the moist membranes in the lungs, or the more or less moist skin, the temperature of the blood is lowered. The gain and loss of heat balance one another with great nicety, and the blood, circulating rapidly, now through warmer, and again through cooler, tubes, is kept at a uniform temperature of about 100° F. (37.8 C). 2a 354 ANATOMY FOR NURSES [Chap. XVIII In this way the whole body is warmed in somewhat the same way as we warm a house, the warm blood in the blood-vessels heating the tissues, as the hot water in the hot-water pipes heats the rooms in water-heated dwellings. THE REGULATION OF HEAT The maintenance of the normal temperature of the body is due : (1) to the control exerted by the nervous system, (2) to the regu- lation of muscular exercise and diet, (3) to the use of clothing, and (4) the use of hot and cold baths. Control of nervous system. — As the amount of heat lost through the skin and lungs as well as the metabolism taking place in the body is under the control of the nervous system, it follows that this control is preeminently important. It is effected by means of the heat centres, the sensory nerves, the sweat nerves, and the vaso- motor nerves of the skin. Heat regulation by the skin. — When the external temperature is high, tlie nerve-endings which respond to heat are stimulated, and these impulses are transmitted over sensory nerves to the nerve centres controlling the motor nerves of the sweat-glands. The motor nerves stimulate the activity of the sweat-glands, and an increased amount of sweat is poured out upon the surface of the body. An increased amount of heat is required to vaporize this sweat, and thus heat is lost. Excessive humidity interferes with the evaporation of water, and thus interferes with the loss of heat ; hence the discomfort experienced on hot, humid days. The sensory nerves which are stimulated by heat not only trans- mit impulses that stimulate the sweat-glands to activity, but at the same time transmit impulses that result in the depression of the vaso-constrictor nerves of the arterioles of the skin. In con- sequence the arterioles dilate and more blood is sent to the surface to be cooled. When the external temperature is low, the sensory nerve endings which are stimulated by cold transmit impulses which result in stimulation of the vaso-constrictors, and conse- quent contraction of the arterioles of the skin. This lessens the amount of blood in the skin arterioles, and lessens the amount of heat lost. Heat regulation by respiration. — The stimulation of the sen- sory nerves of the skin that are affected by cold influences the Chap. XVIII] BODY HEAT 355 respiratory centres, increases the rate of the respirations, and con- sequently increases the loss of heat. In man respiration plays only a small part in heat regulation, but in animals that do not perspire, respiration is an important means of regulating the temperature. Mechanism of heat regulation. — Just how the nervous system controls the amount of heat produced by metabolism is not known. Various theories are advanced, one being that there are special nerves and special heat centres : (1) thermogenetic, which is concerned in the production of heat, (2) thermolytic, which is con- cerned in the dissipation of heat, and (3) thermotactic, which is concerned in regulating the former two. Another theory is that the temperature of the blood influences the motor nerves of the muscles. Stimulation by cold causes increased contraction and increased oxidation. Heat causes relaxation and a decrease in oxidation. Metabolism is also influenced by the action of the vasomotor system, for under the influence of cold, the blood is driven to the interior of the body and metabolism is increased; under the influence of heat, the blood is driven to the surface of the body and metabolism is decreased. Heat regulation by muscular exercise and diet. — Muscular contractions give rise to heat, therefore muscular activity is used as a means to counteract the effects of external cold. On the other hand, muscular activity does not increase the temperature in hot weather to any marked extent. This is accounted for by the fact that when muscular exertion causes the blood to circulate more quickly than usual, the blood-vessels in the skin dilate, the sweat-glands at the same time are excited to pour out a more abun- dant secretion, and the heated blood passing in larger quantities through the cutaneous vessels (which are kept well cooled by the evaporation of the perspiration), the general average temperature of the body is maintained. During digestion heat is produced partly by the peristaltic ac- tion of the intestines, and partly by the activity of the various digestive glands (particularly the liver). The quantity of food eaten, and the relative amount of heat-producing food, influences the temperature of the body. In cold weather an increase in food (usually accompanied by an increase of fats) serves to replace the greater amount of heat lost. When muscular exercise is impos- 356 ANATOMY FOR NURSES [Chap. XVIIl sibie, as in infants, an increase in fats serves the same purpose as exercise in a healthy aihilt. Heat regulation by clothing. — By clothing we can aid the func- tions of the skin and the maintenance of heat ; though, of course, clothes are not in themselves sources of heat. The object of clothing is, in winter, to prevent conduction, radiation, and evapo- ration of heat from the skin, and in summer to promote it. In considering the heat value of clothing the important properties are : (1) whether it is loosely or tightly woven, (2) its thickness, and (3) its color. (1) Materials that are loosely woven will be warmer than those that are tightly woven, because the meshes in a loosely woven material are capable of holding air, which is a poor conductor of heat, and thus prevents radiation. (2) Thick material does not allow cold air to penetrate to the skin. (3) Dark colored materials absorb heat to some extent, hence they are warmer than light colored textiles. Thick, porous ma- terials are used to keep the body warm. Wool has an additional advantage, as evaporation takes place more slowly from it than from linen, cotton, or silk. Thin and very porous materials help to keep the body cool, because they allow the air to penetrate to the skin, and thus assist the evaporation of sweat. Heat regulation by baths. Hot baths. — The primary effect of a hot bath is to prevent radiation of heat from the surface of the body, and some increase in temperature may result. If the bath is not continued for too long a time, this effect is counteracted by the increased perspiration that follows. Cold baths. — The primary effect of a cold bath is similar to the effect of cold air. The cold contracts the arterioles of the skin, drives the blood to the interior, and increases oxidation. If the bath is a short one and is followed by friction, the reaction is for the arterioles to dilate, the heated blood is sent to the surface, the circulation is quickened, and there is a consequent loss of heat. In health the gain in heat is usually balanced by the loss of heat, and the purpose of a cold bath is to exercise the arterioles and stimulate the circulation. If the bath is continued for some time, the temperature of the skin, and of the muscles lying beneath, is reduced, and either the heat-producing processes may be checked Chap. XVIII] BODY HEAT 357 and a loss of temperature result ; or shivering may intervene. In this case the muscular contractions and constriction of the blood- vessels stimulates metabolism and heat production. Wnen cold baths are given for the purpose of increasing heat elimination, friction is used during the bath to prevent shivering. Friction stimulates the sensory nerves of the skin, causes dilatation of the arterioles, and favors the flow of hot blood to the surface, thus decreasing the sensation of cold and increasing heat elimination. If properly given, cold baths stimulate the nervous system, improve the tone of the muscles, including the muscles of the heart and blood-vessels, stimulate the circulation, and favor the elimination of heat. VARIATIONS IN TEMPERATURE Normal variations. — The temperature of the human body is usually measured by a thermometer placed in the mouth, axilla, or rectum. Such measurements show slight variations, as the temperature in the interior of the body is slightly higher than on the surface of the skin. The average temperature in the rectum ^ is 98.9° F., in the axilla is 98.4° F., in the mouth is 98.3° F. Other normal variations depend upon the manner of living, time of eating, age, etc. The lowest temperature is usually in the early morning, it rises slowly during the day, reaches its maximum in the evening, and falls again during the night. This corresponds to the usual temperature ranges in fever, when the maximum is in the evening and the minimum in the early morning. Muscular activity and food may also cause slight increase in temperature during the day. Age has some influence. Infants and young children have a slightly higher temperature than adults. It is also true that the heat-regulating mechanism in infants^ and young children is not so efficient as in adults, consequently they are more subject to changes of body temperature, and these changes are not as significant as they would be with adults. Aged people show a tendency to revert to infantile conditions, and their temperature is usually slightly higher than in middle life. 1 Rectal temperature is the most reliable, and that by mouth (if properly taken) is almost equally reliable. Axillary temperature has little value. * At birth the heat-regulating mechanism is not "in working order," and during the first few weeks of life infants are not able to regulate their body temperature, hence the importance of keeping them warm. Premature infants are even less able to regulate their body temperature, hence need of special means to keep them warm. 358 ANATOMY FOR NURSES [Chap. XVIII Abnormal variations. Fever. — The term fever is applied to an abnormal condition, characterized by increased temperature, increased heart-beat, increased respiration, increased tissue waste, and faulty secretion. Cause. — The exact cause of fever is unknown. It is the result of causes which disturb the balance between heat production and heat elimination. One theory is that there is a heat centre in the brain which controls the production and elimination of heat, and toxic substances circulating in the blood or abnormal conditions of the various organs of the body may interfere with the proper functioning of this centre. The toxic substances circulating in the blood may result from faulty metabolism, as in diabetes, gout, etc. ; or from the action of bacteria, as in infectious dis- eases ; or from injury to the tissues of a mechanical, thermal, or chemical nature. Value of fever. — When fever is due to infection by bacteria, the body seems better able to fight the infection if the tempera- ture is elevated. For this reason fever is thought to be a protective measure and antipyretics are not used unless the elevation is ex- treme, or long continued. In this case measures must be taken to reduce the temperature, or death may ensue from coagulation of the proteins present in the nerve-cells of the brain and spinal cord. Subnormal temperature. — In some maladies the temperature falls distinctly below normal. This is no doubt chiefly due to diminished metabolism. In cases of starvation the fall of tem- perature is very marked, especially during the last days of life. The diminished activity of the tissues first affects the central nervous system ; the patient becomes languid and drowsy, and finally unconscious ; the heart beats more and more feebly, the breath comes more and more slowly, and the sleep of unconscious- ness passes insensibly into the sleep of death. Chap. XVIII] SUMMARY 359 Func- tions Skin<^ SUMMARY 1. Protective covering for deeper tissues. 2. As a sense organ. 3. As an excretory organ — Elimination of waste matter in sweat. ' Absorption through unbroken A A„„« u u- skin is limited. 4. As an absorbmg organ < . , I Absorption rapid if epidermis [ is removed. 5. Most important as organ in heat regulation. Small amount oxj'gen taken in. Small amount carbon dioxide is thrown off. ' Practically dead cells being con- stantlj^ shed and renewed from germi- native layer. 6. As a respiratory organ Epidermis is a strati- fied epi- theUum 1. Superfi- cial or horny b. Soft protoplasmic cells that are constantly multiplying by cell division. Stratum corneum Stratum lucidum Stratum granulo- sum Germina- tive or Con- I Mal- sists of 1 I pighian Papillary layer — papillae are minute coni- cal elevations of the cutis vera. They Derma is contain looped blood-vessels and ter- a layer minations of nerve-fibres called tactile of con- { corpuscles. nective f Bundles of fibrous and elastic tissue 2. Reticular I tissue, with network of layer blood-vessels, lymphatics, and nerves. Blood-vessels — They are found in derma only. Send branches to papillae and glands of skin. Capable of holding one-half to two-thirds total amount of blood in body. f 1. Vasomotor. 2. Two sets concerned in temperature sense. Nerves { 3. Nerves concerned in sense of touch or pressure. 4. Nerves stimulated by pain. 5. ]\[otor nerves from sympathetic system. r Nails. Appendages Hair. Sebaceous glands. Ceruminous glands. Sweat-glands. 360 ANATOMY FOR NURSES [Chap. XVIIJ Nails Hair Sebaceous Glands Ceruminous Glands Sweat- glands Sweat Found all over body, except [ Consist of clear, horny cells of epidermis. j True skin forms a bed or matrix for nail. Root of nail is lodged in a deep fold of the skin. Nails grow from soft cells in gerrainative layer at root. The hair grows from the roots. The roots are bulbs of soft-growing cells contained in the hair follicles. Hair follicles are little pits developed in the derma. Stems of hair extend beyond the surface of the skin, con- sist of three layers of cells: (1) cuticle. (2) fibrous substance. (3) medulla. (Palms of the hands. Soles of the feet. Last phalanges of the fingers and toes. Arrector muscles are attached to true skin and to each hair follicle. Saccular glands the ducts of which usually open into a hair follicle, but may discharge separately on the sm- face of the skin. Lie between arrector muscles and hairs. ^ , X- 1 • i- J. f Palms of hands. V ound over entire skin surface except ^ ^ i f f + Secrete sebum, a fatty, oily substance, which keeps the hair glossy and the skin flexible, and forms a protective layer on surface of skin. (Modified sweat-glands. Found in skin of external auditory canal. Secrete cerumen, a yellow, pasty substance, like wax. Tubular glands, consist of blind ends coiled in balls, lodged in subcutaneous tissue, and surrounded by a capillary plexus. Secrete sweat and discharge it by means of ducts which open exteriorly. (Pores.) Watery, colorless, turbid liquid, salty taste, distinctive odor, and acid reaction. Consists of water, salts, fatty acids, urea, and carbon dioxide. Average quantity, one quart in twenty-four hours. L Dilute condition of blood. 2. Increased temperature or humidity of the atmosphere. Exercise. Pain. Mental excitement or nervousness. Dj'spnoea. Use of diaphoretics. Amount increased by 3. 4. 5. 6. 17. Chap. XVIII] SUMMARY 361 Sweat Activity of Sweat- glands Body Heat Amount increased by 8. Csrtain diseases • Amount decreased by Animals divided into 2 classes Tuberculosis. Acute rheuma- tism. Malaria. 9. Use of electricity to stimulate secretory nerves. Voiding a large quantity of urine. Cold. Diarrhoea. Certain drugs. r Fevers. Certain diseases < Diabetes. I Some paralyses. 1. Direct stimulation of nerve-ending in sweat-glands. 2. Indirect stimulation of nerve centres controlhng per- spiration. [ 3. Action of vasomotor nerves on calibre of blood-vessels. 1. Warm-blooded or those which have an almost constant temperature. Human beings are in this class. 2. Cold-blooded or those whose tem- perature varies with that of their environment. The human foetus is cold blooded. 1. Chemical changes associated with oxidation. 2. Friction of muscles, blood, etc. 3. Ingestion of warm food. Wherever metabohc changes are tak- ing place. Offers large surface foi radiation, conduction. Skin 88 per j and evaporation of cent I sweat. Contains large amount Lost by \ [of blood. Lungs — 9 per cent is lost warming the expired air and the evaporation of the water of respiration. Urine and Feces — 3 per cent is lost warming the urine and feces. Distributed — by the blood circulating through the blood vessels. (Heat centres. Sensory nerves. Sweat nerves. [ Vasomotor nerves. Produced by 362 ANATOMY FOR NURSES [Chap. XVIII Body Heat ^V Regulated Variations in Temperature Normal ( Activity of sweat-glands. Skin < Dilatation and contraction I of skin arterioles. Respiration. Control of metabolism by nervous system. IMuscular exercise and diet. Clothing. fHot. 1 Cold. 2. 3. 4. 5. 6. Baths Abnormal ' 1. Depends on where temperature is I . ..,. taken | t^ ' ' { Itectum. 2. Depends on time f Lowest in early morning. of day I Highest in early evening. 3. Slightly increased by muscular activitj' and the digestive processes. 4. Age. Higher and f Infants, cliildren, and more variable in I the aged. Increased temperature. Increased pulse. Symptoms < Increased respiration. Increased tissue waste. Faulty secretion. Cause — not definitely known. Value — thought to help the body to fight infection. Subnormal — due to diminished metaboUsm. Fever ■ CHAPTER XIX THE NERVOUS SYSTEM In Chapter III it was stated that eight systems of organs were found in the human body. Six of these systems have been studied, leaving the seventh, i.e. the nervous system, to form the subject matter of this chapter. Parts of the nervous system. — The nervous system consists of : (1) the brain and spinal cord, which are contained within the cavities of the ?kull and spinal column ; (2) masses of nerve cell- bodies called s^Tapathetic ganglia, which are situated in the head and neck, also in the thoracic and abdominal cavities ; (3) nerve trunks, which connect the brain, spinal cord, and s;vTnpathetic gang- lia with each other, with the viscera, and with the periphery of the body. All of these structures are made up of nerve tissue. In addition the endings of the nerves distributed to the organs of the special senses, such as the eye, ear, and skin, are in close contact with modified epithelial cells sometimes called organules. Functions of the nervous system. — The human nervous system makes possible all the higher functions of human life. It enables us to think and to will, to recognize our surroundings and to accommodate ourselves to them ; to move, to talk, to hear, to see ; and it guarantees equilibrium and muscular coordination. Divisions of the nervous system. — For purposes of study the nervous system is arbitrarily divided into two parts : (1) the central nervous system or cerebro-spinal system, and (2) the sympathetic system. These two systems are not separate, dis- tinct, and independent as the names might imply, but are inti- mately connected both structurally and functionally, and are really interdependent. (1) The central nervous system consists of the brain, the spinal cord, and three sets of nerves. (a) Cerebro-spinal nerves connect the brain and spinal cord and form a part of the cord. 363 364 ANATOMY FOR NURSES [Chap. XIX (b) Cranial nerves pass to and from the brain through openings in or between the cranial bones, and are distributed to various organs. (See page 395.) (c) Spinal nerves pass to and from the cord to different parts of the body. (See page 380.) (2) The sympathetic system consists of masses of nerve cell- bodies, and the nerves connected with them. These masses are termed ganglia and are found in the thoracic and abdominal cavi- ties. (See page 375.) Properties of nerve tissue. — All of the organs included in the nervous system are made up of nerve tissue, which is the most highly specialized tissue in the body. It possesses the following marked characteristics: (1) irritability or the power to respond to stimulation, and (2) conductivity or the power to transmit the stimulus or nerve impulse to the muscles, viscera, etc. Just as all other tissues are composed of cells, so the structural unit of nerve tissue is the nerve-cell or neurone. NEURONES Although the neurones vary considerably in size and in form, there are certain structural characteristics which they all possess in common. They consist of : — (1) The cell-body. (2) The cell-processes. These two parts make up a complete nervous entity called a neurone, and the entire nervous system consists of neurones supported by neuroglia^ in the central nervous system, and by con- nective tissue in the nerve trunks. (1) The cell-body. — The cell-bodies vary as to size and shape, but all varieties present certain common characteristics. A topical cell-body consists of a mass of granular cytoplasm surrounding a large, well-defined nucleus, it in turn containing a nucleolus, and the whole mass of cytoplasm may in some cases be surrounded by a cell-wall. From the angles of the cell-body are given off the processes or poles, and the number of processes corresponds to the number of angles. Each cell-body usually has one process and may have several more. ' See page 373. Chap. XIX] THE NERVOUS SYSTEM 365 wenvE CELu— — ^DENOniTES. NAKED AXIS-CYLINDER. -AXIS-CYLINDER PROCESS. COLLATERAL BRANCH. AXIS-CYLINDER CLOTHED WITH MEDULLARY * SHEATH. — MEDULLARY SHEATH. — AXIS-CYLIfiOER. AXIS-CYLINDER CLOTHED WITH MEDULLARY ■ SHEATH AND NEURILEMMA. AXIS-CYLINDER I || CLOTHED WITH < ! ITH- NEURILEMMA. —NEURILEMMA, NAKED Axis-cylinder. / TERMINAL BRANCHES. Fig. 175. — A Neurone. (Gcrrish.) 366 ANATOMY FOR NURSES [Chap. XIX If the cell has but one process, that one is the axis cylinder pro- cess, and the cell is spoken of as a unipolar cell. If the cell has two processes, one is the axis cylinder process, and the cell is called bipolar ; many processes, multipolar. Function of the cell-body. — The cell-body affords nutriment to its processes, as is proven by the fact that if a nerve-fibre is cut, the part separated from the cell-body dies. It also bears the same relation to the cell that the battery does to many kinds of electrical apparatus: (1) it is the centre in which the action takes place which gives rise to nervous impulses ; (2) the cell-bodies are ca- pable of modifying impulses brought to them by their sensory processes. This modification may take the form of inhibition and either partially or completely block impulses ; or it may take the form of summation, i.e. collect weak impulses, and combine them into one effecti^'e impulse before transmission to the motor nerves. As cell-bodies are found only in the brain, spinal cord, and ganglia, it is only in these parts of the nervous system that these activities can take place. (2) The cell-processes. — The cell-processes are named as fol- lows : — (a) Dendrites or dendrons. (6) Axis cylinder processes, named also neuraxones, or axones. fMedullated. i^on-medullated. (d) Collaterals. (e) Nerve-endings. («) Dendrites. — These processes are usually short, and rather thick at their attachment to the cell-body. They have a rough outline, diminish in calibre as they extend further from the cell- body, and branch rapidly in a tree-like manner. These branches are called arborizations. The number of dendrites varies. Function. — The essential function of a dendrite is conduction of a nerve-impulse from the periphery to the cell-body. They collect nerve-impulses from the processes of other cells, and carry them always in one direction, i.e. to the cell-body. Synapse. — In this connection it is important to emphasize that there is no true anastomosis of processes from different cells. The arborizations interlace and intermingle so that the nerve- impulse from one cell-process is able to bridge the gap and set up (c) Nerve-fibres j ^7 Chap. XIX] THE NERVOUS SYSTEM 367 nerve-impulses in the contiguous process. This intermingling of arborizations is called a synapse. (6) Axis cylinder process. — There is but one axis cylinder process given off from each cell, and it differs from the dendrites in the following particulars : — (1) It is usually longer; in some instances it travels as much as 39.37 in. (1 meter) before breaking up into its terminal branches. (2) It has a smooth outline and diminishes in calibre very little. (3) It gives off minute side branches called collaterals. These are generally given off at right angles to the axis cylinder. (4) It merges into a nerve-fibre and usually becomes enveloped in one or two coats. Function. — The function of the axis cylinder process differs from that of the dendrites. The dendrites convey impulses to the cell-body, and the axis cylinder process conveys impulses from the cell-body. Some writers consider that the axis cylinder is capable of carrying impulses in either direction, but this is not the generally accepted view. (c) Nerve-fibre. — While the nerve-fibre is really only the con- tinuation of the axis cylinder process that has undergone some change in structure, it is advisable to describe the nerve-fibre separately as though it were a new subject. Nerve-fibres are of two kinds : medullated, or white fibres, and non-medullated, or gray fibres. Medullated fibre. — If one looks at a medullated nerve-fibre under the microscope, it is found to consist of three parts : (1) a central core called the axis cylinder which is a continuation of the axis cylinder process ; (2) immediately surrounding the axis cylinder is a sheath, or covering, of a semi-fluid, fatty substance called the medullary, or myelin, sheath. It is to the refraction of light from this fatty substance that medullated nerve-fibres owe their white color ; (3) external to the medullary sheath is a thin membrane completely enveloping the nerve-fibre and forming the outer covering called the neurilemma. This is comparable to the sarcolemma that invests muscle-fibres. Function of the medullary sheath. — It is supposed that the medullary sheath serves: (1) as a source of nourishment, (2) as a protection, and (3) as a non-conducting medium for the axis 368 ANATOMY FOR NURSES [Chap. XIX cylinder. In the last-mentioned capacity it is thought that this sheath prevents the deflection of nerve-impulses from their in- tended course, in some such way as the insulation on an electric wire prevents the current from taking a path other than the one desired. Nodes of Ranvier. — At regular intervals along the course of a meduUated nerve-fibre there are noted ring-like constrictions about the nerve-fibre dividing the nerve-fibre into a series of links. These constrictions are the nodes of Ranvier. At each node the constriction is due to a loss of continuity or absence of the medullary sheath, thus allowing the neurilemma to dip in, so to speak, and come in direct contact with the axis cylin- der. Thus at each node the nerve-fibre is smaller in diameter, this change in diameter being entirely at the expense of the medul- lary sheath, the axis cylinder being unchanged. These nodes are about 1 mm. apart, and the portion between two consecutive nerves is called a nerve segment. If a nerve-fibre divides, the division occurs at one of these nodes. In each nerve segment the neuri- lemma is seen to have a nucleus. MeduUated nerve-fibres may be very long, but the diameter is very minute. Function of the nodes of Ranvier. — The passage of the blood- plasma into the axis cylinder is rendered easier by the absence of the medullary sheath at the nodes of Ranvier, and this is thought to be their function. Non-medullated fibre. — Non-medullated nerve-fibres or, as they are sometimes called, the fibres of Remak, do not differ in any respect from the meduUated nerve-fibres save in the absence of the medullary sheath, the axis cylinder being directly invested by the neurilemma. Owing to the absence of the refracting medium (the medullary sheath), the non-medullated fibres do not appear white, but present a grayish or yellow color. (d) Collaterals. — The minute side branches given off at right angles from the axis cylinder process are called collaterals. These are found chiefly in the brain, spinal cord, and ganglia. They end either in bulbous enlargements, or in fine brush-like terminations, which come in contact (synapse) with the processes from other neurones. (e) Nerve-endings. — Nerve-endings may be classified accord- ing to the part of the body in which they are found. Chap. XIX] THE NERVOUS SYSTEM 369 1. Nerve-fibres which terminate in the brain or spinal cord split up into end arborizations. 2. Sensory nerve-fibres ending at the periphery of the body terminate in two ways : — (a) Inter-epithelial arborizations. (b) Organules. 3. Motor nerve-fibres ending in voluntary muscles terminate in motor plates. 4. JNIotor nerve-fibres ending in involuntary muscles (such as in the viscera) terminate in a plexus. End arborizations. — If the nerve-fibre is to terminate while still lying in the mass of the nervous system, its axis cylinder may Fig. 176. — Sensory Nerve Terminations in Stratified Pavement Epi- thelium. (Kirkes.) split up at the termination into a number of short filaments called end arborizations, which interlock with the dendrites of another neurone, or the axis cylinder may send out collaterals which inter- lock with dendrites. Thus an individual neurone would serve only as a relay station. Inter-epithelial arborizations. — This is the most common mode of termination of sensory nerves. The nerve-fibres pass to the surface either in the skin or mucous membrane ; the neurilemma and medullary sheath disappear, the naked axis cylinder subdivid- ing into minute arborizations that ramify between the epithe- lial cells of the surface of the body. This method is the one in which nerves terminate in various glands, hairs, teeth, tendons, etc. Organules. — Some of the highly complex special sensations need very complex end organs for their reception. These end or- gans are modified epithelial cells and are called organules. The axis cylinder subdivides into arborizations as described above; 2b 370 ANATOMY FOR NURSES [Chap. XIX and these enter and terminate in the organules. The different varieties of tactile corpuscles, the organ of Corti, for the auditory nerve, and the rods and cones of the retina may be cited as examples of organules. Motor plates. — A nerve intended to stimulate a muscle to activity terminates by a subdivision of the axis cylinder (the neurilemma and medullary sheath fading out), each branch of the axis cylinder end- ing in a flat nodule of granular material lying on the muscle fibre. This terminal mass is the motor plate. Plexus. — The nerve-fibres which are distributed to the viscera are non-medul- lated, antl near their terminations each one divides into a number of branches which arborize with each other and form a net- work or plexus. From this plexus smaller branches are given off, these subdivide to form fibrils, and the fibrils terminate on the surface of the muscle cells. (See page 377.) Nature of nerve-impulse. — Having ex- amined the make-uj) of a complete ner- vous entity (the neurone), it now seems best to study the nature of nerve-impulses. The nature of a nerve-impulse is not known. We know that nerve-fibres may be stimulated by several means, and the practical result is similar to the result obtained were the nerve stimulated by the natural physiological impulse. The nerve-fibre has no power to initiate a nerve-impulse, but serves merely as a conveyor of the impulse which has been started either in the end organs or in the nerve-cell. Artificial nerve stimulation. — There are four means usually applied to the artificial stimulation of a nerve-fibre, viz. : chemical, thermal, mechanical, and electrical, — the latter the most usual. That the true physiological impulse is none of these can be readily proven. (See any standard work of physi- ology.), Fig. 177. — Pacini's Cor- puscle, a, stalk; b, nerve- fibre entering it ; a, d, con- nective-tissue envrlope ; e, axis cylinder, with its end divided at /. (Collins.) Chap. XIX] THE NERVOUS SYSTEM 371 Physiological nerve stimulation. — The best explanation is that the true nature of nerve-impulse is a physical molecular vibration set up either in the nerve-cell or the end organs and transmitted along the nerve-fibre. Direction of nerve-impulse. — Within the body nerve-impulses travel in two directions : (1) from the cell-body to the periphery, and (2) from the periphery to the cell-body. Afferent and efferent nerve-fibres. — From the previous para- graph it is deduced that the nerve-fibres are divided into two great classes : (1) efferent or centrifugal are those in which the direc- tion for the nerve-impulses to travel is from the cell-body to the periphery; and (2) afferent or centripetal are those in which the impulses travel from the periphery to the cell-body. The most striking example of efferent fibres are those which convey impulses that stimulate functional activity, i.e. muscular contraction or glandular secretion ; hence the efferent nerve- fibres are often spoken of as motor, although motion is the mani- festation of but a class of neurones. On the other hand, afferent fibres are often spoken of as sensory, because it is to them that sensation is due. Reason for direction of nerve-impulse. — Normally the efferent fibres are stimulated only through the cell-bodies from which they spring, and the afferent fibres are stimulated only at their endings. For this reason a nerve-fibre can carry impulses only in one direction. Classification of nerve-fibres. — In addition to classifying nerve- fibres as efferent and afferent, we may subdivide peripheral nerve- fibres into smaller groups depending upon their physiological dif- ferences. Numerous experiments have demonstrated that the effect of an impulse conveyed by nerve-fibres may be either excita- tory or inhibitory; i.e. the tissue or cell may be stimulated to activity, or if already in activity it may be reduced to a condition of rest. On this basis both afferent and efferent fibres may be subdivided into excitatory and inhibitory fibres. Each of these subgroups may be further divided according to the kind of activity it excites or inhibits, and according to the kind of muscle or tissue in which it ends. The following classification, taken from " Text- book of Physiology," by William H. Howell, depends upon three principles : (1) the direction in which the impulse travels normally ; 372 ANATOMY FOR NURSES [Chap. XIX (2) whether this impulse excites or inhibits ; and (3) the kind of action excited or inhibited, which in turn depends upon the kind of tissue in which the fibres end. Eflferent Excitatory- Inhibitory Motor Secretory Inhibito-motor Inhibito-secre- < tory Motor. Vasomotor. Cardiomotor. Visceromotor. Pilomotor. Salivary. Gastric. I Pancreatic. I Sweat. Subdivisions corresponding to the varieties of motor fibres above. Subdivisions corresponding to the varieties of secretory fibres above. Afferent < Excitatory Sensory Inhibitory Reflex Inhibito-reflex Visual. Auditor}'. Olfactory. Gustatory. Pressure. Temperature. Pain. Hunger. . Thirst, etc. I According to the efferent fibres I affected. Inhibitory effects upon the con- scious sensations are not de- monstrated. The reflex fibres that cause un- conscious reflexes are known to be inhibited in some cases at least. Identity of nerve-impulses. — The generally accepted belief is that nerve-impulses are identical in character and vary only in intensity. According to this the impulses carried by a sensory nerve are similar in character to those carried by a motor nerve, and yet the result is different. The result is thought to be deter- mined by the nature of the tissue in which a nerve-fibre ends, rather than by the nature of the fibre itself. Chap. XIX] THE NERVOUS SYSTEM 373 Speed of nerve-impulses. — The speed at which an impulse travels along an afferent nerve-fibre is found to be about 140 feet (42.6 m.) per second. The efferent impulses travel some- what slower, 110 feet (33.5 m.) per second. It may be interesting to note how very slow a nerve-impulse is when compared with light which travels at the rate of about 186,000 miles per second, and sound which travels about 1100 feet per second. Reaction of nerve-endings. — A study of the previous classifica- tion shows that the sensory nerve-endings are not all affected by the same stimulus, nor do they react in the same way. Thus some of the sensory nerve-endings are affected by pressure, and others by temperature. The endings of the auditory nerve in the ear are affected only by sound, and the endings of the optic nerve in the eye are affected by ligh.:, though a similar effect may be produced by a blow on the head, or an accident which jars the spinal column. Gray matter. — The cell-bodies, dendrites, commencement of the axis-cylinder processes, and their collaterals are not scattered promiscuously throughout the body, but are gathered together in certain definite regions or groups. These form the gray matter of the brain, spinal cord, and ganglia. White matter. — The white matter consists of medullated nerve- fibres and is found in the brain, spinal cord, ganglia, and also in the nerve trunks distributed to all parts of the body. Neuroglia. — Neuroglia is not nervous tissue, but is a special kind of tissue found in the brain and spinal cord, and serves the same purpose as connective tissue in other parts of the body. It consists of cells that give off many fine processes which extend in every direction and form a supporting and connecting network among the nerve-cells, nerve-fibres, and blood-vessels. Formation of nerve-trunks. — The nerve-fibre of each neurone is, as has been described, of microscopic diameter, but when a number of these nerve-fibres are bound together in a bundle we have the plainly visible nerve-trunks, or nerves, such as are seen in dissections of the body. Nerves are whitish cords which extend between cells situated in different parts of the brain, spinal cord, and ganglia, also between these centres and all parts of the body. They thus afford a means 374 ANATOMY FOR NURSES [Chap. XIX of communication between : (1) the different parts of the nervous system, (2) the nerve centres and the viscera, (3) the nerve centres and the periphery, and (4) the viscera and the surface of the body. Between the nerve- fibres is a small amount of connective tissue which serves not only to bind the fibres together into bundles, or funiculi, but also to carry to or from the fibres the blood-vessels and the lymphatics nec- essary for their imtrition. Connective tissue also surrounds these bundles in the form of a sheath. Although the nerves branch frequently through- out their course, and these branches often meet and fuse with one another, or with the branches of other nerves, yet each nerve- fibre always remains quite distinct, never branching until it reaches its ter- mination, and never unit- ing with other nerve-fibres. The nerve-trunk is thus merely an association of individual fibres which have very difTerent activities and which may func- tion entirely independent of one another. Perhaps the best idea of the arrangement of ner\'e-fibres in a trunk can be obtained from a cross-section of a nerve such as is seen in Figure 179. Nerve centres. — Groups of nerve-cells exercising control over some definite function are called centres. Each of these centres is influenced by impulses from various parts of the body which travel along special nerves to these centres. Many of these cen- FiG. 178. — Diagram General Arrangement of SPINAL System. ILLUSTRATING THE THE CeREBRO- Chap. XIX] THE NERVOUS SYSTEM 375 tres are situated in the medulla and spinal cord. Most of the cen- tres in the medulla are concerned with processes that are absolutely necessary to life, hence are called vital centres. Examples of these are the centres controlling respiration and the cardiac centre. Intercentral neurones and relays. — Neurones whose processes do not pass outside of the brain or spinal cord are called intercentral or connecting neurones. An impulse passing from say the foot to the brain, might have to pass through two or three, or even Fig. 179. — Transverse Section of the Sciatic Nerve of Cat about X 100. — It consists of bundles (funiculi) of nerve-fibers ensheathed in a fibrous supporting capsule. more, neurones ; these neurones form a system of relays. A par- allel may be found in sending a telegraphic message ; the message may have to pass over several different systems of wires and even- tually be carried by messenger before it reaches its destination. These relays only occur in the brain and spinal cord. In the illus- tration referred to above, one relay would take the impulse to the spinal cord ; this naturally means a very long fibre ; one or several might be required to take it from the spinal cord to the brain. THE SYMPATHETIC SYSTEM The sympathetic system consists of three sets of ganglia and the nerves connected with them : — 1. Vertebral or lateral ganglia. 2. Collateral or prevertebral ganglia, and plexuses. 3. Terminal ganglia and plexuses. 4. Sympathetic ganglia in the brain and cord. 376 ANATOMY FOR NURSES [Chap. XIX The vertebral ganglia. — The vertebral ganglia consist of a chain of ganglia situated on each side of the spinal column, and extending from the base of the skull to the cocc^'x. There are about forty-nine of these ganglia, twenty-four on each side of the spine, and one in front of the coccyx. They are connected with each other by nerve-fibres called ganglia cords, and with the spinal nerves by branches which are called rami communicantes} They are also connected to the viscera and blood-vessels by branches which travel different pathways: (1) they pass directly to the viscera ; (2) they converge to form three main nerve-trunks, called the great splanchnic, the small splanchnic, and the least splanchnic, and then send branches from these trunks to the vis- cera ; (3) they join the collateral ganglia and plexuses ; (4) they join the spinal nerves, and in them reach the part of the body for which they were destined. The collateral ganglia. — The collateral or outlying ganglia consist of masses of gray matter and their nerves, which are located principally in the thoracic and abdominal cavities. They are connected with the spinal nerves, with the vertebral ganglia, and send branches to the viscera. These branches form plexuses, the most important of which are : (1) the cardiac plexus, located above the heart and supplying it with sympathetic fibres, (2) the solar plexus, located behind the stomach and supplying most of the ab- dominal viscera, (3) the hypogastric or pelvic plexus, located in the lower part of the abdomen and supplying the viscera of the pelvis. The terminal ganglia. — The terminal ganglia include all the ganglia situated in the walls of the organs themselves, as for in- stance those in the walls of the heart, and in the walls of the ali- mentary canal. These ganglia are directly connected with the collateral ganglia, and in some instances the nerves derived from the collateral plexuses form a secondary or terminal plexus on the organs. Sympathetic ganglia in the brain and spinal cord. — In connec- tion with a few of the cranial nerves, such as the third and fifth, certain ganglia are found. Sympathetic ganglia are also found in the spinal canal and in the medulla. (See vasomotor centres.) ^ Autonomic system is a name that has recently been suggested for the sympathetic system as outlined above. Prior to the introduc- » See page 377. « See page 378. Chap. XIX] THE NERVOUS SYSTEM 377 tion of this name, the fourth group was not included in the sym- pathetic system. The term autonomic impHes that these nerves are to some extent independent of the central nervous system and possess a certain amount of self-government. Rami communicantes. — The nerve-fibres that connect the vertebral ganglia and the spinal nerves are called rami communi- cantes. Each connection consists of two rami, one white and the other gray. The white ramus consists of medullated fibres, and these pass from the cord to the ganglion. The gray ramus consists of non-medullated fibres that pass from the ganglion to join the spinal nerve. Plexuses. — The term plexus has been used to designate a net- work of nerves. It is worthy of special mention because the nerve- fibres arborize with each other, and there is an interchange of fibres between the different nerve-trunks. The advantages of this ar- rangement are : (1) each nerve is less dependent on the unimpaired condition of any single portion of the nerve-trunk or nerve-centre, (2) each nerve has a wider communication with the nerve-centres, and (3) any given part of the body is not dependent on one nerve. The various plexuses of the sympathetic system serve all these purposes, and in addition the organs constituting any one system are brought into direct communication with each other. In this way coordination of action is secured. Distribution of sympathetic nerves. — Nerve-fibres from the sympathetic system are distributed: (1) to the heart, (2) to the involuntary muscles of the blood-vessels, lymphatics, and viscera, (3) to the secretory glands, and (4) to some of the special senses, such as those that regulate the pupil of the eye. Interdependence of the sympathetic and central nervous sys- tems. — The fibres which connect the s^^mpathetic ganglia and the spinal nerves form a direct pathway for impulses from all of the viscera to the spinal cord and brain. In addition many of the viscera are connected with the brain by the cranial nerves (see page 395). This means that there are often two sets of nerve-fibres distributed to an organ, and we know that in some instances the action of these fibres is antagonistic. This is true in the case of the inhibitory and accelerator fibres of the heart, and increased knowl- edge may prove it to be true in connection with all the organs of the body. 378. ANATOMY FOR NURSES [Chap. XIX Vasomotor centres. — The chief vasomotor centres are situated in the medulla oblongata, but there are also subsidiary centres in the spinal cord. The vasomotor nerves are of two kinds, — vaso- constrictor and vaso-dilator. While these nerves are always considered as belongino; to the sympathetic system, it should be noted that the centre that controls them is located in the medulla, which is part of the central nervous system. SPINAL CORD The spinal cord is that portion of the nervous system lodged within the spinal canal of the vertebral column. It consists of a collection of gray and white substance, extending from the foramen magnum of the skull, where it is continuous with the medulla oblongata of the brain, to about the second lumbar vertebra, where it tapers off into a fine thread. Before its termination it gives off a number of fibres which form a tail-like expansion, called the Cauda equina. Membranes of the cord. — Like the brain, the spinal cord is protected and nourished by three membranes. These membranes have the same names and practically exercise the same functions as those enveloping the brain (for description of which see page 384). The outer membrane is not attached to the walls of the spinal canal, being separated from them by a certain quantity or areolar and adipose tissue, and a network of veins. Structure of the cord. — The spinal cord does not fit closely into the spinal canal, as the brain does in the cranial cavity, but is, as it were, suspended within it. It diminishes slightly in size from above downward, with the exception of presenting two enlargements in the cervical and lumbar regions, where the nerves are given off to the arms and legs respectively. It is usually from sixteen to seventeen inches (400 to 425 mm.) long, and has an average diameter of three-fourths of an inch (19 mm.). The spinal cord is almost completely divided into lateral halves by an anterior and posterior fissure, the anterior fissure dividing it in the middle line in front, and the posterior fissure in the middle line behind. In consequence of the presence of these fissures, only a narrow bridge of the substance of the cord connects its two halves. This bridge, also called isthmus, is traversed throughout its entire length by a minute central canal. On making a trans- Chap. XIX] THE NERVOUS SYSTEM 379 verse section of the spinal cord, the gray matter is seen to be ar- ranged in the form of a butterfly with extended wings. The tips of each wing are called its horns or cornua, the anterior horns being thicker and larger than the posterior. The transverse bar of gray matter found in the isthmus is called the gr^y commissure, and it connects the two lateral masses of gray matter. The white matter is arranged around and between the gray matter, tne proportion of gray and white varying in different regions of the cord. The VCNTRO-MCDIAN FISSURE VENTRAL ROOTS VENTRAL HORN LATERAL HORN RETICULAR OORSAL HORN OORSO-LATERAL FISSURE OORSAL ROOTS OORSO-MEOIAN FISSURE Fig. 180. — Transverse Section of the Spinal Cord at the Middle of THE Thoracic Region. The neuroglia septum has been removed from between the dorsal columns. (Gerrish.) white matter is composed of medullated nerves, and the gray matter consists of cell-bodies, dendrites, axis cylinder processes, and collaterals, all held together and supported by neuroglia. The medullated nerve-fibres are grouped in bundles known as tracts or columns, and the majority run in a longitudinal direction. These tracts are classified under two main headings: (l)sensory, or those which carry impulses upward to the brain ; they begin in the gray matter of the cord, ascend, and terminate in the gray matter of the brain ; (2) motor, or those which carry impulses ,380 ANATOMY FOR NURSES [Chap. XIX downward ; they begin in the gray matter of the brain, descend, and terminate in the gray matter of the cord. The most im- portant tracts are : — Postero internal tract or Cohimns of Goll. Ascending or Postero external tract or Columns of Burdach. Sensory Antero lateral tracts. Postero lateral tracts. Descending or f Crossed pyramidal tract. Motor \ Direct pyramidal tract. In addition to these long tracts, there are shorter columns con- sisting of both sensory and motor nerves, which serve to connect centres at different levels in the cord, and on different sides of the cord. These are called lateral columns. SPINAL NERVES There are thirty-one pairs of spinal nerves, arranged in the following groups, and named from the region through which they pass. They are : — Cervical 8 pairs. Thoracic 12 pairs. Lumbar 5 pairs. Sacral 5 pairs. Coccygeal 1 pair. The first cervical nerve arises from the medulla oblongata and leaves the neural canal between the occipital bone and the altas. With this one exception the spinal nerves spring from both sides of the spinal cord, and with one exception — coccj^geal — they pass out through the intervertebral foramina. The coccyxgeal passes through the lower extremity of the canal. Mixed nerves. — The spinal nerves consist almost entirely of medullated nerve-fibres, and are called mixed nerves because they contain both sensory and motor fibres. Each spinal nerve has two roots, a ventral or anterior root and a dorsal or posterior root. The fibres connected with these two roots are collected into one bundle, and form one nerve just before leaving the canal through the intervertebral openings. Before joining to form a common Chap. XIX] THE NERVOUS SYSTEM 381 trunk, the fibres connected with the dorsal root present an en- largement, this enlargement being due to a ganglion, or small nerve-centre, situated in the intervertebral foramina. The fibres of the ventral root arise from the gray matter in the ventral horn, and are direct prolongations from the cell-bodies there. The fibres of the posterior root arise from the cells composing the enlargement or ganglion of the posterior root and pass toward the periphery ; each cell of the ganglion, besides sending toward Fig. 181. — Diagram of Nerve Roots emerging from Spinal Cord. P.R. posterior root. Sp.G. ijosterior root ganglion. A.R. anterior root. (Schematic.) (Collins.) the periphery the nerve-fibres just described, sends a branch along the posterior root up into the gray matter of the posterior horn, there to break up into branches articulating with other cells or dendrites. All the fibres making up the ventral root are efferent fibres, and convey nervous impulses from the spinal cord to the periphery. The fibres making up the dorsal root are aflFerent fibres, and convey nervous impulses from the periph- ery to the spinal cord. It should be borne in mind that the dorsal roots contain only sensory fibres, and that these fibres always have their origin outside of the cord (i.e. in the spinal ganglia), while the ventral roots contain only motor fibres, and these have their origin within the central nervous system. The relations of the roots, fibres, and so forth, can be best 382 ANATOMY FOR NURSES [Chap. XIX understood from a study of the accompanying diagrams (Figs. 181 and 182). Degeneration and regeneration of nerves. — Since, as has been stated, tlu' cc'll-hody is essential for tlie nutrition of the whole cell, it follows that if the processes of a neurone are cut oft", they will suffer from malnutrition and die. If, for instance, a spinal nerve be cut, all the peripheral part will die, since the fibres composing it have been cut oft" from their cell-bodies situated in the cord, or in the spinal ganglia. The divided ends of a nerve that has been cut across readily reunite by cicatricial tissue, — that is to say, the connective tissue framework unites, but the cut ends of tlie fibres themselves do not unite. On the contrary, the peripheral or severed portion of the nerve begins to degenerate, the medullary Fig. 182. — Degeneration of Spinal Nerves and Nerve-roots after Section. A, section of ncrvo-trunk beyond the ganglion; B, section of anterior root ; C, section of posterior root ; D, excision of ganglion ; a, anterior root ; p, posterior root ; g, ganglion. sheath breaks up into a mass of fatty molecules and is gradually absorbed, and finally the axis cylinder also disappears. In regen- eration, the new fibres grow afresh from the axis cylinder of the central end of the severed nerve-trunk, and penetrating into the peripheral end of the neurilemma, grow along this as the axis cylinder of the new nerve, each axis cylinder becoming after a time surrounded with a medullary sheath. Restoration of function in the nerve may not occur for several months, during which time it is presumed the new nerve-fibres are slowly finding their way along the course of those which have been destroyed. Distribution of the terminal branches of the spinal nerves. — After leaving the spinal canal each spinal nerve divides into two main trunks known as the anterior and posterior divisions. Each of these contain sensorv and motor fibres. The anterior division Chap. XIX] THE NERVOUS SYSTEM 383 supplies the extremities and parts of the body in front of the spine. The posterior division suppHes the muscles and skin of the back of the head, neck, and trunk. Each anterior division connects with the sympathetic system by means of fibres which pass from the nerve to the sympathetic system and vice versa. Previous to their final distribution in the cervical, sacral, and lumbar re- gions these nerves form plexuses known as the cervical, sacral, and lumbar plexuses. In passing to the viscera, muscles, skin, etc., these terminal nerves follow the same pathway as the blood- vessels. Names of peripheral nerves. — Many of the larger branches given off from the spinal ner^'es bear the same name as the artery which they accompany, or of the part which they supply. Thus the radial nerve passes down the radial side of the forearm, in com- pany with the radial artery ; the intercostal nerves pass between the ribs in company with the intercostal arteries. Functions of the spinal cord : — (a) Conduction, -or the conveyance of impulses and sensations between the centres and the periphery. (b) Reflex action, i.e. the origination of an impulse or action in response to a stimulation from the periphery, without of necessity involving the brain in the act or even without con- sciousness of the reflex act on the part of the individual. (c) Automatic acts, i.e. acts set up primarily in the cells of the cord by the cells themselves, and not as a result of stimula- tion by brain cells (voluntary acts) nor as result of peripheral stimulation. (d) Inhibition of reflex acts. — If every outside stimulation were allowed its full effects in the setting up of reflex acts, the body would be on " the jump " all the time. This overactivity is checked unconsciously by the cells of the spinal cord endowed with this function. (e) Transference, i.e. an apparent transferring of impulses from one set of fibres to another. BRAIN The brain, the most complex and largest mass of nervous tissue in the body, is contained in the complete bony cavity formed by the bones of the cranium. It is covered by three 384 ANATOMY FOR NURSES [Chap. XIX membranes (also named meninges), — the dura mater, pia mater, and arachnoid. The dura mater is a dense membrane of fibrous connective tissue containing a great many blood-vessels. It is arranged in two layers and the layers are attached except in a few places. The external layer is adherent to the bones of the skull, and forms their internal periosteum. The internal layer covers the brain and sends numerous prolongations inward for the support and protec- tion of the different lobes of the brain. These projections also form sinuses that return the blood from the brain, and sheaths for the nerves that pass out of the skull. It may be called the protective membrane. The pia mater is a delicate membrane of connective tissue, containing an exceedingly abundant network of blood and lymph vessels. It dips down into all the crevices and depressions of the brain, carrying the blood-vessels which go to every part. It may be called the vascular or nutritive membrane. The arachnoid is a delicate serous membrane which is placed between the dura mater and the pia mater. With the exception of the longitudinal fissure,^ it passes over the various eminences and depressions on the surface of the brain and does not dip down into them like the pia mater. Between the arachnoid and the pia mater is a space called the sub-arachnoid space in w'hich is a certain amount of fluid. This fluid is secreted by the arachnoid and is called the cerebro-spinal fluid. It serves to lubricate the other membranes and prevent friction. In cases of meningitis, i.e. in- flammation of these membranes, the amount of this fluid is very much increased. Structure of the brain. — The whole brain appears to consist of a number of isolated masses of gray matter — some large, some small — connected together by a multitude of medullated fibres (white matter) arranged in perplexing intricacy. But a general arrangement may be recognized. The numerous masses of gray matter in the interior of the brain may be looked upon as forming a more or less continuous column, and as forming the core of the central nervous system, while around it are built up the great mass of the cerebrum and the smaller mass of the cerebellum. This central core is connected by various bundles of fibres with the iSee page 389. Chap. XIX] THE NERVOUS SYSTEM 385 spinal cord, besides being, as it were, a continuation of the gray- matter in the centre of the cord. It is also connected at its upper end by numberless fibres to the gray matter on the surface of the cerebrum. Weight of the brain. — With the exception of the whale and the elephant, the human brain is heavier than that of any of the lower animals. The average weight of the brain in the male is forty-nine and a half ounces (1403 grams) ; in the female, forty-four ounces (1247 grams). It appears that the weight of the brain increases rapidly up to the seventh year, more slowly to between sixteen and twenty, and still more slowly to between thirty and forty, when it reaches its maximum weight. Beyond this age the brain diminishes slowly in weight, about an ounce every ten years. Divisions of the brain. — The brain is divided into four principal parts : the cerebrum, the cerebellum, the pons Varolii, and the medulla oblongata. The medulla oblongata. — The medulla oblongata, also known as the spinal bulb, is continuous with the spinal cord, which, on passing into the cranial cavity through the foramen magnum, widens into an oblong-shaped mass. It is directed backward and downward, its anterior surface resting on a groove in the occipital bone, and its posterior surface forming the floor of a cavity between the two halves, or hemispheres, of the cerebellum. It is hollow and the cavity, called the fourth ventricle, is an expanded continuation of the tiny central canal which runs throughout the whole length of the spinal cord. The gray matter is found in the interior, and the white matter on the exterior ; most of the gray matter is found on the floor of the fourth ventricle, and from this gray matter arise most of the cranial nerves. The medulla has an anterior and a posterior median fissure ; at the lower part of the anterior fissure are nerve-fibres which cross from one side to the other or decussate. Functions of the medulla oblongata. — The functions of the medulla are similar to the first three listed under the functions of the cord, i.e. conduction, reflex action, and automatic action. As all the impressions passing between the brain and spinal cord must be transmitted through the medulla, the function of con- duction is a very important one. As previously stated, the medulla contains important vital and reflex centres. The prin- cipal ones are : — 2c 386 ANATOMY FOR NURSES [Chap. XIX (1) The respiratory centres for regulating the function of respi- ration. (2) Accelerator centres for the heart. (3) Vasomotor centre to regulate size of arterioles in any part of the body, thus controlling the amount of blood furnished to that part. (4) Other centres, such as the vomiting centre, heat control- ling centre, etc. The student will readily appreciate that, the medulla being the seat of such important centres as those controlling respiration and the heart's action, if the medulla be seriously injured, death will result. Cerebellum. — The cerebellum, or " little brain," occupies the lower and back of the skull cavity, overhanging the medulla oblongata. It is of a flattened, oblong shape, and measures from three and a half inches to four inches (87 to 100 mm.) trans- versely, and from two to two and a half inches (50 to 03 mm.) from before backward. It is divided in the middle line into two lateral lobes, or hemispheres, and a median lobe, by a central depression, each lobe being subdivided by fissures into smaller portions. The surface of the cerebellum consists of gray matter and is traversed by numerous curves, or furrows, which vary in depth. The interior consists of white matter. Peduncles of cerehcUiim. — The cerebellum is connected with the rest of the cerebro-spinal system by many white nerve- fibres grouped in bundles called the peduncles. The peduncles are arranged in three pairs. The anterior (superior) peduncles pass forward from the cerebellum to enter into the cerebrum. The posterior (inferior) peduncles pass down to the medulla, where they are known as the restiform bodies. The middle pair pass into and make up the larger portion of the pons Varolii, thus serving as a means of intercommunication between the two halves of the cerebellum. Thus it is seen that the cerebellum communicates most freely with the entire cerebro- spinal system. Functions of the cerebellum. — The principal function of the cerebellum seems to be the coordination of ordinary movements, and the maintenance of equilibrium. The reason for this belief is that disease or destruction of the cerebellum apparently exerts Chap. XIX] THE NERVOUS SYSTEM 387 no malign influence on sensory nerves nor upon the intellect. The motor system is, however, profoundly deranged. IVIotion is itself not destroyed, but coordination is so interfered with that movements of one part of the body cannot be adapted to other parts. Pigeons deprived of the cerebellum will fly if thrown from a roof XT' XII- SYLVIAM FISSURC lion PER- ED SPACE INFUNOI* BULUM POSTEPIOR PER- FORATED SPACE CRUS CEREBRI ( 'i mSm I'm iiiii— imAWiT^ wi..i JZ_J_ T1...!II1!1L^\«— ( CEREBELLUM Fig. 183. — Under Surface of the Brain, showing the Superficial Origins of the Cranial Nerves. The Roman numerals indicate the nerves. (Gerrish.) but the delicacy of the coordination being lost, they turn a series of somersaults in the air and soon fall to the ground. Pons Varolii. - — The pons Varolii, or bridge of Varolius, lies in front of the upper part of the medulla oblongata. It consists of interlaced transverse and longitudinal white nerve-fibres intermixed with gray matter. The transverse fibres are those derived from the middle peduncles of the cerebellum and, as already stated, serve to join its two halves. The longitudinal fibres join the medulla with the cerebrum. Functions of pons Varolii. — The pons is a bridge of union be- tween the two halves of the cerebellum and a bridge between 388 ANATOMY FOR NURSES [Chap. XIX the medulla and the cerebrum. It is also a port of exit for the fifth, sixth, seventh, and eit^hth cranial nerves. Cerebrum. — The cerebrum is by far the largest part of the brain. It is egfj-shaped, or ovoidal, and fills the whole of the upper portion of the skull. The entire surface, both upper and under, is composed of layers of gray matter, and is called the cortex because, like the bark of a tree, it is on the outside. The bulk of the white matter in the interior of the cerebrum consists of very small fibres running in three principal directions : (1) from above down- JNTCRNAL JUCUUIfl P'iG. 184. — Falx Cerebri and Tentorium, Left Lateral View. (Gerrish.) ward, (2) from the front backward, and {'.]) from side to side. The fibres link the dift'erent parts of the brain together, and con- nect the brain with the spinal cord. Fissures and convolutions. — In early life the cortex of the cerebrum is comparatively smooth, but as time passes and the brain develops, the surface becomes covered with depressions which vary in depth. The deeper depressions are called fissures, the more shallow ones sulci, and the ridges between the sulci are called convolutions. The fissures and sulci are infoldings of gray matter, consequently the more numerous and deeper they are, the greater is the amount of gray matter, and the greater is the extent of surface for che termination of fibres. The number and depth of these fissures and sulci is thought to bear a Chap. XIX] THE NERVOUS SYSTEM 389 close relation to intellectual power ; babies and idiots have few and shallow folds, while the brains of men of intellect are always markedly convoluted. There are five important fissures which are always present. They are the following : — (1) The Great Longitudinal Fissure, which extends from the back to the front of the cerebrum, and almost completely divides it into two hemispheres, the two halves, however, being connected in the centre by a broad, transverse band of white fibres called the corpus callosum. A process of the dura mater extends down into this fissure and separates the two cerebral hemispheres. It is called the falx cerebri, because it is narrow in front, and broader behind, Fig. 185. — External View of Outer Side of Right Cerebral Hemi- sphere, SHOWING Rolando, Sylvian, and Parieto-occipital Fissures to- gether with Principal Convolutions. (Collins.) thus resembling a sickle in shape. In a previous chapter it was stated that the blood was returned from the brain in venous chan- nels called sinuses. Two important sinuses are lodged between the layers of the falx cerebri. The superior longitudinal sinus is contained in the upper border, and the inferior longitudinal sinus in the lower border. (2) The Transverse Fissure, which is between the cerebrum and the cerebellum. A process of the dura also extends into this fis- sure, and covers the upper surface of the cerebellum and the under surface of the cerebrum. It is called the tentorium cerehelli. 390 ANATOMY FOR NURSES [Chap. XIX There is one of each in each hemisphere. For location see Figs. 185 and 186. (3) Fissure of Rolando, or^ central fissure. (4) Fissure of Sylvius. (5) Parieto-occipital fissure. ^ Lobes of the cerebrum. — The longitudinal fissure divides the cerebrum into two hemispheres, and the transverse fissure divides the cerebrum from the cerebellum. The three remaining fissures divide each hemisphere into five lobes. With one exception these Fig. 186. — Mesial View of Left Cerebral Hemisphere, showing Ro- LANDIC AND PaRIETO-OCCIPITAL FiSSURES, TOGETHER WITH THE PRINCIPAL Convolutions. (Collins.) lobes were named from the bones of the cranium under which they lie ; hence they are known as : — (1) Frontal lobe. (2) Parietal lobe. (3) Temporal lobe. (4) Occipital lobe. (5) Central lobe, or Island of Reil (the exception). (1) The frontal lobe is that portion of the cerebrum lying in front of the fissure of Rolando, and usually consists of four main convolutions. (2) Parietal lobe is bounded in front by the fissure of Rolando, and behind by the parieto-occipital fissure. (3) Temporal lobe lies below the fissure of Sylvius and in front of the occipital lobe. Chap. XIX] THE NERVOUS SYSTEM 391 (4) Occipital lobe occupies the posterior extremity of the cerebral hemisphere. When one examines the external surface of the hemisphere, there is no marked separation of the occipital lobe from the parietal and temporal lobes that lie to the front ; but when the surface of the longitudinal cleft is examined, the parieto- occipital fissure serves as a boundary anteriorly for the occipital lobe. (5) Central lobe, or Island of Reil, is not seen when the sur- face of the hemisphere is examined, for it lies within the fissure Fig. 187. — The Lobes of the Convex Surface of the Hemisphere, Left Side. (Gerrish.) of Sylvius, and the overlying convolutions of the parietal and frontal lobes must be lifted up before the central lobe comes into view. Ventricles of the brain. — In describing the spinal cord, ref- erence was made to the central canal, being a minute canal running through the centre of the cord throughout its entire length, thus converting the cord into a tube with exceedingly thick walls but very small internal calibre. In the brain proper this same central channel persists, and just as the walls or solid portions of the brain are directly continuous with the wall or solid portion of the spinal cord, so is the internal hollow of the brain directly continuous with the hollow or central canal of the cord. The cavity in the brain presents some marked differences to that of the cord ; while 392 ANATOMY FOR NURSES [Ch.^p. XIX the latter is a straight, fairly uniform canal of very small diameter, the former is at some points very narrow, and at others much widened out so as to form quite jrood-sized chambers, and these chambers are called the ventricles of the brain. These ventricles are filled with cerebro-spinal fluid, just as the canal of the cord is like\vise filled with the same material. The ventricles are five in number. The most posterior is the enlargement or expansion of the central canal, occupying the sub- stance of the medulla oblongata, and is called the " fourth ven- tricle." Leading forward from the anterior end of the fourth ventricle, the calibre of the canal again narrows to a very small diameter ; the tube, on reaching the brain substance uniting the two halves of the cerebrum, again expands into a somewhat smaller chamber, called the "third ventricle." The small canal already mentioned as joining the third and fourth ventricles is known as the aqueduct of Sylvius. Toward the forward end of the third ventricle there are noted two small channels, the foramina of Monro, one on either side leading in a direction forward, upward, and outward, each fora- men leading into a very large ventricle occupying the centre of its corresponding cerebral hemisphere, called the lateral ventricles. The fifth ventricle is very small, lies between the two lateral ventricles, and is not in communication with the other ventricles. The student will thus see that both the brain and spinal cord are really hollow. In some portions, however (as the spinal cord), the interior cavity is so minute and the walls so exceed- ingly thick that the cavity is a negligible quantity, and the mass can practically be considered as solid ; on the other hand, in the case of the ventricles, especially the lateral ventricles, the cavity is large enough to occupy an appreciable space, and may become overdistended with cerebro-spinal fluid in certain con- ditions of disease. On the whole, the cavity of the brain and cord occupies a more or less central position, having its walls at any given point of about equal thickness ; at certain points, however (the third and fourth ventricles especially), the cavity approaches so close to the surface that at these points one of its walls is thinned out to only a microscopic thickness. Chap. XIX] THE NERVOUS SYSTEM 393 Function of the cerebrum. — The nerve-centres which govern all our mental activities and the coordination of movements are centred in the cerebrum. These centres are the seat of reason, intelligence, will, memory, and all the higher emotions and feelings. Localization of brain function. — As the result of numerous experiments on animals, and close observation of individuals suffering from cerebral diseases or wounds, physiologists have been able to localize certain areas in the brain which control motor and sensory activity. They have also been able to gain some knowl- FiG. 188. — Localization of Function in the Cerebral Cortex. ■ " Surgical Anatomy.") (Woolsey's edge of the areas in the cerebrum which are concerned with the higher mental activities. Names of areas. — That portion of the cerebrum which governs muscular movement is known as the motor area, the portions controlling sensation as the sensory areas, and those connected with the higher faculties, such as reason and will, as association areas. Motor areas. — The surface of the brain assigned to the func- tion of motion is the posterior part of the frontal lobe, i.e. the gray matter immediately in front of the fissure of Rolando. A knowledge of the motor area enables physicians and surgeons, in many cases of convulsions or paralysis, to locate the exact por- tion of the brain that is affected, by close observation of the part 394 ANATOMY FOR NURSES [Chap. XIX of the body involved in the convulsion or loss of function. In this connection it must be remembered that the fibres extending from the brain into the cord, and from the cord into the brain, decussate or cross in the medulla. Sense areas. — The term " sense areas " is used to designate those parts of the brain to which sensation is due, and which control vision, hearing, smell, and taste. The visual area is situated in part of the occipital lobe ; the auditory area in the superior part of the temporal lobe ; and the olfactory and gustatory areas are in the anterior part of the temporal lobe. Location of speech areas. — " The speech areas, four in number and in kind, are in the left hemisphere in right-handed persons and in tlie right in left-handed persons. There are two types of aphasia, which is the loss of the power of speech, known as motor and sen- sory aphasia. The motor speech centre lies in the posterior part of the third frontal convolution just in front of the centre of the muscles of speech. A lesion of the motor speech centre causes motor aphasia, in which there is a loss of the word-forming power, although the tongue is movable and the patient may understand spoken and written language and knows what he wants to say. It is as if memory of the motor combinations essential to produce speech were lost. The power of writing is usually lost with motor speech. The probable location of its cortical centre is in the posterior two-thirds of the first, and perhaps in the second, temporal convolution. A lesion here causes ' word deafness,' a sensory aphasia in which the memory of the sounds of words is lost so that they are not under- stood, though hearing may be normal. Word-blindness (alexia), or the loss of memory of printed or written language, is caused by a lesion in the occipital lobe, though sight itself may be normal. "Thus the basis of language is a series of memory pictures: (1) of the sound of words; (2) of their appearance; (3) of the effort necessary to enunciate them ; and (4) to write their sjTnbols. As these memory pictures are connected with each other and with others that make up the concept by subcortical association fibres passing between them, a lesion in any of these association tracts Chap. XIX] THE NERVOUS SYSTEM 395 also leads to a defect of speech." (Woolsey, " Applied Surgical Anatomy.") Association areas. — Those parts of the cerebral cortex which are not the location of special centres are called association areas. It is here that the information received by the various sense centres is built up and coordinated into concepts or perceptions. The various parts of the association areas are connected with the sense centres by means of association fibres. The localization of function in the association areas is not yet determined. THE CRANIAL NERVES The cranial nerves consist of twelve pairs. They each have a superficial and a deep origin. The superficial origin is the point where they emerge from the under surface of the cerebrum and the medulla, but they can be traced back to various centres in the higher part of the brain, and these centres constitute their deep origin. Classification. — The cranial nerves are of three varieties : (1) sensory nerves, (2) motor nerves, and (3) mixed nerves or those containing both sensory and motor fibres. Many of the cranial nerves arise from several nerve-centres, and therefore con- sist of several bundles of nerve-fibres. After these nerves leave the cranium they split up into branches that are widely distrib- uted. Numbers and names. — They are named numerically according to the order in which they arise from the brain. Other names are also given to them, derived from the parts to which they are distributed or from their functions. Taken in their order from before backward, they are as follows : — 1. Olfactory (sensory). 2. Optic (sensory). 3. Motor oculi (motor). 4. Pathetic, or trochlear (motor). 5. Trifacial, or trigeminal (mixed, but mainly sensory). 6. Abducens (motor). 7. Facial (motor). 8. Auditory (sensory). 9. Glossopharyngeal (mixed). 10. Pneumogastric, or vagus (mixed). 396 ANATOMY FOR NURSES [Chap. XIX 11. Spinal accessory (motor). 12. Hypoglossal (motor). The following doggerel which has been handed down through countless generations of students may assist the beginner in learn- ing the order of the cranial nerves. Each capital letter denotes a cranial nerve. On Old ^Manhattan's Peaked Tops A Finn And German Picked Some Hops. (1) The olfactory ner\'e is the special nerve of the sense of smell Its origin is in the olfactory bulb, and its peripheral fibres are distributed to the upper third of the nasal cavity. (2) The optic nerve is the special nerve of the sense of sight. Its cell-bodies are situated in the retinal coat of the eye. (3) The motor oculi nerve supplies all the muscles of the eye except the superior oblique and the external rectus. It originates in the gray matter of the pons Varolii. (4) The pathetic, or trochlear, nerve supplies only the superior oblique muscle of the eye. It arises close to the preceding nerve. (5) The trifacial has two roots, — a dorsal, or sensory, and a ventral, or motor. The fibres from the two roots coalesce into one trunk, and then subdivide into three large branches : (1) the oph- thalmic, (2) the superior maxillary, and (3) the inferior maxillary. The ophthalmic branch is the smallest, and is a sensory nerve. It supplies the eyeball, the lacrimal gland, the mucous lining of the eye and nose, and the skin and muscles of the eyebrow, forehead, and nose. The superior maxillary, the second division of the fifth, is also a sensory nerve, and supplies the skin of the temple and cheek, the upper teeth, and the mucous lining of the mouth and pharynx. The inferior maxillary is the largest of the three divisions of the fifth, and is both a sensory and a motor nerve. It sends branches to the temple and the external ear ; to the teeth and lower jaw ; to the muscles of mastication ; it also supplies the tongue with a special nerve (the lingual) of the sense of taste. The cell-bodies of the motor fibres are situated in the pons ; while those of the sensory fibres, as in the case of the spinal nerves, are situated in a ganglion. This ganglion is called the Gasserian ganglion. (6) The abducens nerve supplies the external rectus muscle of the eye. (7) The facial nerve is the motor nerve of all the muscles of expression in the face ; it also supplies the neck and ear. Its Chap. XIX] THE NERVOUS SYSTEM 397 cells of origin, like those of the abducens nerve, are situated in the medulla. (8) The auditory nerve is the special nerve of the sense of hear- ing. It arises from cells which compose the organ of Corti in the internal ear, to which its fibres are exclusively distributed. (9) The glossopharyngeal nerve is distributed, as its name indicates, to the tongue and pharynx, being the nerve of sensa- tion to the mucous membrane of the pharynx, of motion to the pharyngeal muscles, and the special nerve of taste to part of the tongue. (10) The pneumogastric nerve has a more extensive distribu- tion than any of the other cranial nerves, passing through the neck and thorax to the upper part of the abdomen. It contains both motor and sensory fibres. It supplies the organs of voice and respiration with motor and sensory filaments ; and the pharynx, oesophagus, stomach, and heart with motor fibres (cardiac inhibi- tory). (11) The spinal-accessory nerve consists of two parts : one, the spinal portion, and the other, the accessory portion to the tenth nerve. It is a motor nerve supplying certain muscles of the neck. It differs from the other cranial nerves in arising from the spinal cord, but it leaves the skull by the same aperture as the pneumo- gastric and glossopharyngeal. (12) The hypoglossal nerve is the motor nerve of the tongue. Reflex acts. — The student doubtless can understand from the preceding portions of this chapter the general arrange- ment of the nervous tissues, and how simple impulses arising in brain cells pass along nerve-fibres, and, terminating in the end organs, produce, for example, a muscular contraction (mo- tor impulse), or how an outside stimulus applied to the skin will set up vibrations in suitable end organs to be transmitted along sensory nerve-fibres to end in sensory brain cells and pro- duce the appreciation by the mind of the fact that the stimu- lus has been applied. All of these are simple, straightforward functions of the neurones. There is a host of other more com- plex acts in which, for example, two or more neurones take part, which carry out a train of functions, each depending on the other, and may carry out their destiny so smoothly and accurately, so that the perception of the mind or consciousness of the act 398 ANATOMY FOR NURSES [Chap. XIX be entirely wanting, thus saving the brain an enormous amount of wear and tear. The simplest of these nervous mechanisms is the reflex arc, and the simplest form of nervous activity is " reflex action." Tw^o neurones enter into the formation of a reflex arc, a sensory neurone and a motor neurone. On applying an appropriate stimulus to the peripheral end of the sensory neurone, an impulse is generated which passes along the sensory neurone to the nerve- Fro. 189. — Reflex Arc. S, sensory neuron arising in tactile corpuscles. M, mo- tor neuron ending in muscle fibres. R, interlacing of dendrites. (Collins.) centre, and back again to the periphery by the motor neurone ; and, since the motor neurone terminates in a muscle (or some similar mechani.sm), we get a muscular response as the indirect result of stimulating the sensory nerve. This is a reflex act, and usually the exchange between the sensory and motor impulse takes place in the spinal cord. The sensory impulse, after delivering its stimulus to the motor neurone, may continue on up the spinal cord to terminate in the brain and give to the individual the consciousness of the stimulus, or, on the other hand, the sensory impulse, after arousing the motor act, may cease, and no impulse be transmitted to the brain, Chap. XIX] THE NERVOUS SYSTEM 399 the individual thus being totally oblivious to the reflex act. Even if the sensory impulse goes to the brain, the consciousness of the sensation by the individual is always later in point of time than the reflex act. For example : If, without a person's knowledge that the experiment is to be tried, one's finger be pricked with a pin, the finger is instantly pulled back and the act is done before the individual is conscious of the pain. In this experiment the sensory impulse of the pin prick passed to the spinal cord, set up the motor action necessary to withdraw the finger, and then passed on to the brain. Again, many sensory impulses produce their reflex without the brain bother- ing about the matter at all. An example of this is the act of walking. Walking is an exceedingly difficult accomplishment to learn, acquired in childhood only after laborious eft'ort, not because the muscles are weak, but because the human individual, when erect, is in an exceedingly unstable state of equilibrium, and constant contraction and relaxation of groups of muscles is necessary to maintain the balance. Here the sensory impulses of being out of balance arouse motor impulses in first one set of muscles, then another, to restore the balance. At first this is only accomplished with mental appreciation of the performance ; later on one learns the trick, and the act of walking or standing upright is performed without a moment's thought or even consciousness of the difficult task we are doing purely by reflex activity. The kind of stimulus which will call forth the nerve-impulse depends on the peripheral termination of the afferent nerve, and the kind of response which an appropriate stimulus will call forth depends on the mode of termination of the efferent nerve. Thus, light falling on the retinal coat of the eye (the peripheral termination of the sensory nerve) generates an impulse which passes to the centre by the optic nerve, and returns again by the motor oculi nerve to the periphery ; viz. the sphincter of the iris (the termination of the motor nerve), which by its contraction narrows the pupil. Hence arises the well-known phenomenon of the contraction of the pupil when light falls upon the eye. Also stimulation of taste fibres in the mouth causes a reflex secretion of the salivary glands. Innumerable examples of this kind might be given. Indeed, since physical life has been well- defined as the continual response to external stimuli, reflex 400 ANATOMY FOR NURSES [Chap. XIX action, which is the chief inethod of response, is the most im- portant vital phenomenon peculiar to animals possessing any nervous svstem whatsoever. Fig. 190. — Diagram of Nervous System, a, a, cortex of cerebral hemi- spheres ; h, b, cell-body and dendrites of upper motor neurone, situated in cerebral cortex ; h', axis cylinder of ujjper motor neuroiic, branching at its termination near the dendrites of lower motor neurone, situated in the ventral horn of gray matter in the spinal cord ; B, axis cylinder of lower motor neurone passing to its termina- tion in a voluntary muscle fibre B" ; C, cell-body and dendrites of upper sensory neurone, situated in the medulla oblongata ; C, C, axis cylinders of upper sensory neurone, terminating in cortex ; c, cell-body of lower sensory neurone, situated in the dorsal root ganglion ; c'", dendrite of lower motor neurone, conducting impulses from the periphery to the central nervous system ; c", long branch of lower sen- sory neurone, conducting impulses toward the brain ; c', short branch of lower sensory neurone, conducting impulses direct to ventral horn. (For the sake of simplicity the connections with the cerebellum are omitted.) Chap. XIX] SUMMARY 401 A careful study of Figs. 189 and 190 will make the typical reflex path perfectly intelligible to the student, and should on no account be omitted. All nervous action is fundamentally similar to this typical reflex action. Usually the number of neurones involved is greater, often very much greater, than two. The fewer the neurones, the simpler and more obviously machine-like the reaction. The more complex the path, the more uncertain and variable the reaction. When the path of the impulse does not involve the cerebrum, the reactions are unconscious and comparatively sim- ple ; but if the cerebral cortex be involved, the passage of the nerve-impulse is accompanied by the phenomenon of conscious- ness, and the reaction may be exceedingly complex, uncertain, and long delayed. These are the characteristics of what we call voluntary reactions. But, although the phrase " reflex action " is usually confined to those actions which are involuntary and of which we are unconscious, yet all nervous action is essentially the same, differing only in the complexity of the path followed by the impulse. Nervous System Parts of Nervous System Func- tions Divisions < SUMMARY Brain. Spinal cord. Sympathetic ganglia. Nerve-trunks. Organules. ■ Makes possible mental activities. Recognition of surroundings and accommodation to same. Motion and sensation. Equilibrium and coordination. Brain. Spinal cord. C Cerebro-spinal. Nerves < Cranial nerves. I Spinal nerves. 1. Vertebral ganglia. 2. Collateral ganglia. 3. Terminal ganglia and plexuses. 4. Sympathetic ganglia in the brain and cord. Central ner- vous sys- < tem SjTnpathctic system 2d 402 ANATOMY FOR NURSES [Chap. XIX Property of nerve- tissue I Irritability or the power to respond to stimulation. Conductivity or the power to transmit stimuli. Neurone or Nerve- ■ ceU Cell- body Cell- processes Cell-body Dendrites. Axis cylinder process. Nerve-fibres. Collaterals. Nerve-endings. ( Unipolar. Varieties i Bipolar. i Multipolar. Nutrition. Gives rise to nervous impulses. - , vc • 1 f Inhibition. Modifies impulses i „ [ Summation. Function ■ Dendrites ■ Short, break up into many branches. Rough outline — diminish in calibre. May be one, or many. . Function — Collect and carry impulses to cell-body. Synapse — Arborization of contiguous processes, not an anatomical continuation. Axis Cylinder Process Nerve- fibre Long, smooth outline, diminishes very little. Gives off collaterals. Continued as core of nerve-fibre. Function — Carry impulses from cell-body. Mcdul- lated Non- medul- lated Axis cylinder process. Medullary sheath-function Neurilemma. Axis cylinder process. Neurilemma. I Protection. \ Non-conduction. Nodes of Ranvier ■ Ring-like constrictions in medullated fibres, due to absence of medullary sheath. Function — Render easier the passage of blood-plasma to fibre. Collaterals — Minute side branches given off from axis cylinder processes, usually at nodes of Ranvier. Chap. XIX] SUMMARY 403 Nerve- endings Nerve- impulse 1. End arborizations 2. 3. Inter-epithelial arborizations ( Organules terminations in brain or cord. terminations of sensory fibres at the periphery J of the body. Motor plates — terminations of motor nerve-fibres in voluntary muscle. Plexus — terminations of motor nerve-fibres in involun- tary muscle. J Nature not positively known. I Presumably a physical molecular vibration. Classifi- cation of Nerve- fibres Efferent Excitatory , Inhibitory ' Excitatory Afferent . Inhibitory Reflex Inhibito- I'eflex f Motor , Secretory Inhibito- motor Inhibito- secre- tory Sensory Motor. Vasomotor. Cardiomotor. Visceromotor. Pilomotor. ' Salivary. Gastric. Pancreatic. Sweat. ( Subdivisions correspond- S ing to the varieties of i motor fibres above. Subdivisions correspond- ing to the varieties of secretory fibres above. Visual. Auditory. Olfactory. Gustatory. Pressure. Temperature. Pain. Hunger. Thirst, etc. J According to the efferent \ fibres affected. Inhibitory effects upon the conscious sensations are not demonstrated. The reflex fibres that cause unconscious reflexes are known to be inhibited in some cases at least. 404 ANATOMY FOR NURSES [Chap. XIX Speed Nerve- impulse of Afferent fibre — 140 ft. per second. Efferent fibre — 110 ft. per second. Light — 186,000 miles per second. Sound — 1100 feet per second. Cell-bodies. Varieties of Nerve < Tissue Gray matter White matter Nerve- trunks Dendrites. Commencement of axones. Collaterals. ( Brain. < Spinal cord. I Ganglia. Consists of medullated nerves. Brain. Spinal cord. Ganglia. Nerve-trunks. Neuroglia — Special tissue found in brain and spinal cord — function — support. Consists of ' Found in Found in Consist of Func- tion is connec- . tion of Bundles of nerve-fibres bound together to make funiculi. Funiculi bound together to make nerve-trunks. Connective tissue surrounds funiculi and nerve- trimks. 1. Different parts of nervous system. 2. Nerve-centres and the viscera. 3. Nerve-centres and the periphery. 4. Viscera and the surface of the body. Nerve- centres Vertebral Ganglia ■ Groups of nerv^e-cells exercising control over some definite function. Loca- j Brain, tion 1 Spinal cord. Ganglia — Collection of nerve-cells. ( Twenty-four on either side of spinal column. Number ^ ^ . , , , I One in front of coccyx. 1. With each other by ganglia cords. 2. With spinal nerves by rami communicantes. a. Pass directly to viscera. Con- I [ Great splanchnic. nected 1 3. With b. Converge to form < Small splanchnic. viscera I I Least splanchnic. c. Join collaterals and plexuses. d. Join spinal nerves. Chap. XIXl SUMMARY 405 Collateral Ganglia Located principally in thoracic and abdominal cavities. (With spinal nerves. With vertebral ganglia. With viscera. (Cardiac plexus. Solar plexus. Hypogastric or pelvic plexus. Terminal f Located on walls of organs themselves. Ganglia \ Connected with collateral ganglia. Sympathetic Ganglia are found in the medulla, spinal canal, and in connec- tion with some of the cranial nerves. Con- nected Form Distribu- tion of Sympa- thetic Nerves Spinal Cord To the heart. To the involuntary muscles of the blood-vessels, Ijnuphatics, and viscera. To the secretory glands. To some of the special senses. Located in spinal canal. Extends from foramen magnum to second lumbar vertebra, 16-17 in. long. ( Dura mater (outer). Meninges < Arachnoid (middle). I Pia mater (inner) . ' Gray matter in form of butterfly. (Sensory. Motor. Mixed, f Anterior divides front portion in lateral halves. 1 Posterior — divides back portion in lateral halves. Isthmus — connects lateral halves. Canal — centre of isthmus. 1. Conduction. 2. Reflex action. 3. Automatism. 4. Inhibition. 5- Transference. Consists of Fissures Functions 406 ANATOMY FOR NURSES [Chap. XIX Spinal Nerves Number , Variety Cervical 8 pairs. Thoracic 12 pairs. Lumbar 5 pairs. Sacral 5 pairs. Coccygeal 1 pair. 31 pairs. Medullated. Mixed (^J"f^^- 1 Motor. Origin — two roots Distribution trunks two Anterior in gray matter of cord. Posterior in spinal ganglia. Anterior, supplies extremities, and parts of body in front of spine. Posterior, supplies muscles and skin of back of head, neck, and trunk. Located in cranial cavnty. Covered by meninges — same as spinal cord. J Maile — 49^ oz. average. \ Female — 44 oz. average. Weight Medulla Cerebellum < Divisions < Description Function Description Function f Pons Varolii Description Function Cerebrum hemi- spheres Description { ' Oblong-shaped mass, upward continuation of cord. Gray matter in interior. . "VMiite matter on exterior. {Respirator}- centres. Accelerator centre for heart. Vasomotor centres, f Flat oblong-shaped mass, overhangs medulla. I 3-4^ in. transversely. I 2-2 1 from before backward. Gray matter on exterior. White matter in interior. f Coordination. i Maintenance of equilibrium. ■ A bridge of nerve-fibres con- necting two halves of cere- bellum and also medulla \\-ith cerebrum. Connect two halves of cere- bellum. j Connect medulla and cere- l brum. f Egg-shaped or ovoidal. ! Fills upper portion of skull. Gray matter on outside r Fissures. \ Sulci. I Convolutions. Chap. XIX] SUMMARY 407 < <; Divisions Description Fissures Ventricles < f f f White matter on inside. Great longitudi- nal fissure. Transverse fissure. Rolandic. Sylvian. Parieto-occipital. Frontal. Parietal. Cerebrum 2 Lobes { Occipital, hemi- { I Temporal, spheres { i Central. Fourth ventricle. Third ventricle. 2 lateral ventricles. ^ Fifth ventricle, f Motion. Sensation. Functions { Speech. Hearing. [ Memory and higher functions. Motor area — in front of Fissure of Rolando. Visual — occipital lobe. Auditory — superior part of the temporal Sense areas ] lobe. ^ ' ^ > anterior part of temporal lobe. I Gustatory] ^ ^ Association areas — parts of the cerebral cortex which are not the location of special centres. I. Olfactory. II. Optic. III. Motor oculi. IV. Pathetic. V. Trifacial. VI. Abducens. VII. Facial. VIII. Auditory. IX. Glossopharyngeal. X. Pneumogastric. XL Spinal accessory. XII. Hypoglossal. Reflex Act — Involuntary activity that is the result of stimulation by motor nerve-fibres. Impulses are transferred from sensory fibres and activate the motor fibres. Names of Areas Cranial Nerves < CHAPTER XX INTERNAL AND EXTERNAL SENSES: TASTE, SMELL, HEARING. AND SIGHT Definition of sensation, — Sensation is defined as perception through the sense organs, and is the result of stimulation of these organs. Organs necessary for sensation. — A peripheral organ for the reception of a stimulus, a nerve for its conduction, and a centre in the brain for the perception and interpretation are the three essential parts of a sense organ. It is by means of impressions received by the peripheral organs and conducted by the nerves to the brain that the mind is able to control the body and to take cognizance of the external world. Where sensations are interpreted. — Sensations are felt and interpreted in the brain. Our habit of projecting sensations to the part that is stimulated, tends to obscure this fact. In reality we see and hear with our brains, because the eye and ear serve only as end organs to receive the stimulus which must be carried to the brain and interpreted before we do see or hear. CLASSIFICATION OF SENSATIONS Sensations were formerly classified into two groups, i.e. special and common. The special senses were sight, hearing, touch, taste, and smell. All other sensations were grouped as common. A more recent classification is dependent on the part of the body to which the sensation is projected, and the two groups are named : (1) internal or interior senses, and (2) external or exterior senses. These classifications have much in common, but differ slightly. Internal or interior senses are those in which the sensations are projected to the interior of the body. It is by means of these senses that we acquire a knowledge of the condition of our body. They include hunger, thirst, pain, muscular sense, fatigue, and vari- 408 Chap. XX] INTERNAL AND EXTERNAL SENSES 409 ous obscure sensations which proceed from the viscera and give us the feehng of well-being or the reverse, also the desire for defecation or urination. External or exterior senses are those in which the sensations are projected to the exterior of the body. They form the means by which we become acquainted with the outside world. They include pressure and temperature sense, taste, smell, hearing, and sight. Even this classification is not absolutely distinctive, as some sensations may be projected either to the interior or exterior of the body. Temperature and pain are examples of this class. Hunger. — Hunger occurs normally at a certain time after meals and is usually projected to the region of the stomach. It is pre- sumably due to contractions of the empty stomach, which stimu- late the nerves distributed to the mucous membrane. In abnormal conditions the stomach need not be empty, for it must be remem- bered that physiologically food is not considered as being inside the body until it ha.s been digested and absorbed. Thus a diabetic may feel very hungry, although he has within a short time partaken of a huge meal. Thirst. — This sensation is projected to the pharynx. We know very little about the nervous mechanism involved, but it is thought that when the water content in the tissues falls below a certain amount the sensory nerve fibres in the pharynx are stimu- lated and' produce the sensation of thirst. The sense of thirst is more imperative than that of hunger ; a person can live several days without food, provided he has water, but if this latter is denied, he will soon die of exhaustion. Pain. — The sensation of pain is thought by some authorities to be due to stimulation of special nerves that give rise to the sense of pain. Other authorities question the existence of special nerves for thivs sense, and think it is due to overstimulation of any of the sensory nerves. For instance, extreme pressure or extremes of temperature cause overstimulation of the nerves of pressure or temperature, and the result is painful. Muscular sense. — The end organs of the muscular sense are situated in the tendons and between the fibres of the muscles. They convey to us the sense of resistance in the muscles when we attempt to lift anything. This is the muscular sense. 410 ANATOMY FOR NURSES [Chap. XX Through it precision of effort is rendered possible ; for by it we learn to adjust the force exerted to the weight of the object to be lifted. Thus the function of muscular sense is to enable us to estimate weight or resistance. It also aids in preserving equilibrium and in coordinating muscular action. Fatigue. — Prolonged or extreme muscular exercise results in the loss of nutrient material and the accumulation of waste prod- ucts in the muscles. These chemical changes alter the stimula- tion of the nerves connected with muscular sense, and the sensa- tion of fatigue results. Visceral sensations. — Sensations which give rise to the feeling of well-being or the reverse, also to the acts of vomiting, coughing, defecation, or urination, are caused by stimulation of the sensory nerves contained in the part of the body immediately concerned in the state or act in question. The sense of pressure or touch. — The nerves connected with the sense of pressure or touch are distributed over the entire sur- face of the body, being more or less numerous in all parts of the true skin and the adjoining mucous membrane. They end in two ways: (1) in a ring surrounding a hair follicle, so that pressure exerted upon the hair stimulates these end organs, and (2) in parts of the body where there are no hair follicles, in the tactile or Meissner corpuscles, which are also stimulated by pressure. The distribution of these nerves is not uniform. They are abundant and the pressure points are very close together on the lips and the tip of the tongue, also in parts of the hands and feet in which a delicate sense of pressure is present. The temperature sense. — In addition to the end organs of the sense of touch, there are also structures in the skin which are only stimulated by changes in temperature. These structures are of two kinds : hot and cold spots, stimulation of one causing the feel- ing of heat ; stimulation of the other, the feeling of cold. In addition to heat and cold these end organs are stimulated by other substances, i.e. menthol stimulates the cold spots and gives rise to a sensation £)f cold, carbon dioxide stimulates the warm spots and gives rise to a sensation of heat, while certain mechanical and electrical stimuli will cause a sensation of cold on a cold spot and of heat upon a warm spot. The hot and cold spots and the pressure points can be located Chap. XX] INTERNAL AND EXTERNAL SENSES 411 by passing a metallic point slowly over the skin. At certain points a feeling of contact or pressure will be experienced, and at other points a feeling of cold or heat, depending on whether the tempera- ture of the instrument is higher or lower than that of the skin. TASTE Necessary conditions. — Aside from the conditions which are always necessary for sense-perception, — viz. proper organs for receiving, communicating, and perceiving the sensory impulse, — there must be present a sapid substance which must be in solu- tion. The solution in the case of dry substances is effected by saliva. It is also necessary that the surface of the organs of taste shall be moist. The substances which excite the special sensa- tion of " taste " act by producing a change in the terminal fila- ments of the gustatory nerve (branch of the glossopharyngeal) and this change furnishes to it the required stimulant. Organs of taste. — The special organs of the sense of taste are end organs of nerve filaments w'hich are derived from the seventh and ninth cranial nerves. These end organs are called taste buds and are situated chiefly on the surface of the tongue, though there are some of these organs scattered over the soft palate, fauces, tonsils, and pharynx. The tongue. — The tongue is a freely movable muscular organ consisting of two distinct halves united in the centre. The base or root of the tongue is directed backward and is attached to the hyoid bone by numerous muscles. It is connected with the epi- glottis by three folds of mucous membrane, and with the soft palate by means of the anterior pillars of the fauces. PapillcB of the tongue. — The tongue is covered and lined with mucous membrane. The mucous membrane on the under surface is similar to that lining the rest of the mouth, but the mucous membrane on the upper surface is studded with papillae which pro- ject as minute prominences and give the tongue its characteristic rough appearance. Of these papillae there are three varieties : — (1) Circum vallate (walled in) papillae are the largest, are circu- lar in shape, and form a V-shaped row near the root of the tongue, with its open angle turned toward the lips. They serve to secrete mucus and contain taste buds in which the filaments of the glosso- pharj^ngeal nerve terminate. 412 ANATOMY FOR NURSES [Chap. XX (2) Fungiform papilla' are the next in size, and are so named because they resemble fungi in shape. They are found principally on the tip and sides of the tongue. Each fungiform papilla? con- tains a loop of capillaries and a nerve-fibre derived from the glosso- pharyngeal nerve. Fig. 191. — The Upper Surface of tuk i onhue. 1, 2, circumvallate papillae ; 3, fungiform papilla? ; 4, filiform papillae ; 6, mucous glands. (Sappey.) (3) Filiform papillae are the smallest and most numerous. They are found all over the tongue, except at the root, and bear on their free surface delicate hair-like processes which seem to be specially connected with the sense of touch, which is very highly developed on the tip of the tongue. Nerve supply of the tongue. — The nerve-fibres which terminate in the taste buds are : (1) filaments of the lingual nerve, which is a Chap. XX] INTERNAL AND EXTERNAL SENSES 413 branch of the fifth or trifacial, (2) filaments of the chorda tympani, a branch of the seventh or facial, and (3) filaments of the ninth or glossopharyngeal nerve. ^ The twelfth or hypoglossal nerve is distributed to the tongue, but is a motor nerve and is not concerned in the sense of taste or touch. Other sensations in the tongue. — The sense of touch is very highly developed here, and with it the sense of temperature, pain, etc. ; upon these tactile and muscular senses to a great extent depend the accuracy of the tongue in many of its important uses — speech, mastication, deglutition, sucking. We often confound taste with smell. Substances which have a strong odor, such as onions, are smelled as we hold them in our mouths ; and if our sense of smell is temporarily suspended, as it sometimes is by a bad cold in the head, we may eat garlic and onions and not taste them. Hence the philosophy of holding the nose when we wish to s\^allow a nauseous dose. SMELL Necessary conditions. — The first essentials are a special nerve and nerve-centre, the changes in whose condition are perceived as sensations of odor. No other nerve structure is capable of such sensations, even when acted on by the same cause. The special organs for this sense must be in their normal condition, and a stimulus (odor) must be present to excite them. Odors are caused either by minute particles of solid matter or by gases which are in the atmosphere, and they must be capable of solution in the mucus of the pituitary membrane. Odorous particles in the air, passing through the lower, wider air passages, pass by diffusion into the higher, narrower, nasal chambers, and falling on the membrane which is provided with olfactory nerve-endings, produce sensory impulses, which, ascending to the brain, give rise to the sensation of smell. If we wish to smell anything particularly well, we sniff the air up into the higher nasal chambers, and thus bring the odorous particles more closely into contact with the olfactory nerves. Each substance we smell causes its own particular sensation, and we are not only able to recognize a multitude of distinct 1 This is the generally accepted view, but other statements may be found in the various text-books. 414 ANATOMY FOR NURSES [Chap. XX odors, but also to distinguish individual odors in a mixed smell. The sensation takes some time to develop after the contact of the odorous stimulus, and may last a long time. When the stim- ulus is repeated, the sensation very soon dies out, the sensory terminal organs quickly becoming exhausted.^ Olfactory nerves. — The olfactory nerves are the special nerves of the sense of smell, and are spread out in a fine network over the surface of the superior tur- binated processes of the ethmoid bone and on the upper third of the septum. The nerves end in special organs known as olfac- tory cells, which lie under the epithelium, but send prolonga- tions between the mucous cells to the surface. The central por- tions of the olfactory cells are prolonged as nerve-fibres into a mass of gray matter, called the olfactory bulb, which rests upon the cribriform plate of the The nerves which ramifv over Fig. 192. — Vertic.vl Longitudinal Section or Nas.^.l Cavity. 1, olfactory ethmoid bonC. nerve ; v, branch of fifth nerve ; h, hard palate. the lower part of the lining membrane of the nasal cavity are branches of the fifth or tri- geminal nerve. These nerves furnish the tactile sense and enable us to perceive, by the nose, the sensations of cold, heat, tickling, pain, and tension or pressure. It is this nerve which is affected when strong irritants, such as ammonia or pepper, are appreciated by the nose. HEARING The auditory apparatus consists of : (1) the external ear ; (2) the middle car ; (3) the internal ear ; and (4) the auditory nerve. External ear. — The external ear consists of an expanded por- tion named pinna, or auricle, and the auditory canal, or meatus. » This accounts for the fact that one may easily become accustomed to foul odors, and is of special importance to nurses. Foul odors are quickly noticed by any one coming into a sick room from out of doors, but a nurse who is in the sick room constantly may become accustomed to such odors. Hence the importance of act- ing on the first sensation of a disagreeable odor. Chap. XX] INTERNAL AND EXTERNAL SENSES 415 The auricle, except the lower portion, consists of a frame- work of cartilage, containing some fatty tissue and a few muscles. In the lower portion, which is called the lobe, the cartilage is replaced by connective tissue. The auricle is covered with skin, and joined to the surrounding parts by ligaments and a few muscular fibres. It is very irregular in shape, and appears to be an unnecessary appendage to the organ of hearing, except that the central depression, the concha, serves to some extent to collect sound-waves, and to conduct them into the auditory canal. The auditory canal is a tubular passage, about an inch (25 mm.) in length, leading from the concha to the drum-membrane. The Fig. 193. — Semi-diagrammatic Section through the Right Ear. M, concha ; G, the external auditory canal ; T, tympanic, or drum-membrane ; P, tympanum, or middle ear ; o, oval window ; r, round window. Extending from T to o is seen the chain of the tympanic bones ; R, Eustachian tube ; V, B, S, bony labyrinth ; V, vestibule ; B, semicircular canal ; S, cochlea ; b, I, v, membranous labyrinth in semicircular canal and in vestibule. A, auditory nerve dividing into branches for vestibule, semicircular canal, and cochlea. exterior portion of the wall of the auditory canal consists of carti- lage, which is continuous with that of the auricle ; the posterior portion is hollowed out of the temporal bone. This canal is slightly curved upon itself so as to be higher in the middle than at either end, and its direction is forward and inward. Lifting the auricle upward and backward tends to straighten the canal ; except in the case of children it is best straightened by drawing the auricle 416 ANATOiMY FOR NURSES [Chap. XX downward and backward. It is lined by a prolongation of the skin, which in the outer half of the canal is very thick and not at all sensitive, and in the inner half is thin and highly sensitive. Near the orifice the skin is furnished with a few hairs, and far- ther inward with modified sweat-glands, the ceruminous glands, which secrete a yellow, pasty substance resembling wax. This wax is thought, to be offensive to insects, and consequently a defence against their intrusion. Middle ear. — The middle ear, or t\Tnpanum, is a small, ir- regular bony cavity, situated in the petrous portion of the temporal bone, and lined with mucous membrane. It is separated from the external auditory canal by the drum-membrane (membrana tympani), and from the internal ear by a very thin, bony wall in which there are two small openings covered with membrane — the oval window, or fenestra ovalis, and the round window, or fenestra rotunda. The cavity of the middle ear is so small that probably five or six drops of water would completely fill it. It communicates below with the pharynx by the small passage called the Eustachian tube.^ The function of this tube is to ventilate this cavity and keep the atmospheric pressure equal on each side of the drum-membrane. The middle ear also communicates above with a number of bony cavities in the mastoid portion of the temporal bone. These cavities, called mastoid cells, are lined with mucous membrane, which is continuous with that covering the cavity of the tympa- num. Membrana tympani (membrane of the drum). — It is a tough, fibrous membrane set in the bony opening of the external audi- tory canal. The degree of tension of the membrane is regulated by the tensor tympani muscle. This muscle is lodged in a bony canal that is above and parallel with the Eustachian tube. Ossicles. — Stretching across the tympanic cavity is a chain of tiny, movable bones, three in number, and named from their shape the malleus, or hammer, the incus, or anvil, and the stapes, or stirrup. The handle of the hammer is attached to the drum- membrane, and the opposite end or head of the hammer is at- ' This direct connection between the ear and the pharynx is one of the impor- tant reasons for the frequent cleansing of the mouth necessary in infectious and contagious diseases. The Eustachian tube forms a passageway for germs to travel from the mouth to the middle ear and there cause various infections. Chap. XX] INTERNAL AND EXTERNAL SENSES 417 tached to the base of the anvil. The long process of the anvil is attached to the stapes, and the footpiece of the stapes is attached to the fibrous membrane that is stretched across the oval window. These little bones are held in position, attached to the drum-mem- brane, to each other, and to the membrane of the oval window by minute ligaments and muscles. They are set in motion with every movement of the drum-membrane. Vibrations of the mem- brane are communicated to the hammer, taken up by the an^'il, Fig. 194. — Ossicles of the Tympanum, X 4. I, ossicles of the left ear ; 1, malleus; 2, incus; 3, stapes. II, ossicles of the right ear; 1, malleus; 2, long process ; 3, handle ; 4, long process of the incus ; 5, short process of the incus ; 6, stapes. (Flint.) and transmitted to the stirrup, which rocks in the fenestra ova- lis, and is therefore capable of transmitting to the fluid in the cavity of the labyrinth the impulses which it receives. Internal ear. — The internal ear, or labyrinth, receives the ulti- mate terminations of the auditory nerve, and is, therefore, the essential part of the organ of hearing. It consists of a bony labyrinth, which is composed of a series of peculiarly shaped cavities, hollowed out of the petrous portion of the temporal bone, and named from their shape : — (a) The vestibule. (6) The semicircular canals. (c) The cochlea (snail-shell). Within the bony labyrinth is a membranous lab3rrinth, which is composed of a series of sacs, or tubes, fitting more or less closely within the vestibule, semicircular canals, and coclilea. In some 2e 418 ANATOMY FOR NURSES [Chap. XX places it is attached to the bone by bands of fibrous tissue. The cavity within the membrane is filled with a fluid called endolymph, and the space between the membrane and the bone is filled with perilymph. The vestibule is the central cavity situated between the cochlea in front and the semicircular canals behind. It communicates with the middle ear by means of the oval window in its outer wall. The vestibular membrane is constricted in the centre so that it Fig. 196. — The Left Bony Labyhinth of a New-born Child, Forward and Outward View, X 4. From a photograph, and slightly reduced. 1, the wide canal, the beginning of the spiral canal of the cochlea ; 2, the fenestra rotunda; 3, the second turn of the cochlea; 4, the final half-turn of the cochlea; 5, the border of the bony wall of the vestibule, situated between the cochlea and the semicircular canals ; 6, the superior, or sagittal semicircular canal ; 7, the portion of the semicircular canal bent outward ; 8, the posterior, or transverse semicircular canal ; 9, the portion of the posterior connected with the superior semi- circular canal ; 10, point of junction of the superior and the posterior semicircular canals ; 11, the ampulla ossea externa ; 12, the horizontal, or external semicircular canal. (Flint.) consists of two small sacs, called respectively the saccule and the utricle. The saccule is in front and nearer the cochlea, and the utricle is back and nearer the semicircular canals. These sacs are connected by a tube called the endolymj)h duct, which is shaped like an inverted Y (X). The walls of these sacs contain numerous columnar cells provided with stiff hairs which project into the endol\-mph. These cells are in relation with fibres of the vestibular branch of the auditory nerve and serve as end organs. Among these hair-cells rest several small crystals of calcium car- bonate which are called otoliths. Chap. XX] INTERNAL AND EXTERNAL SENSES 419 The cochlea opens from the front end of the vestibule and saccule. It resembles a snail shell and consists of a spiral tube of two and one-half turns around a central pillar called the modiolus. Projecting from the modiolus is a thin lamina or plate of bone. At its outer margin this lamina connects with a membrane which extends to the outer wall of the cochlea. This lamina and mem- brane divide the spiral canal into two passages or scahne. The lower portion of this membrane is called the basilar membrane, and con- sists of a network of fibres which forms the foundation for thou- sands of cells which serve as the end organs of the auditory nerve. These end organs constitute a structure that is known as the organ of Corti. They receive nerve-fibres which arise in the ganglia con- tained in the cavity of the modiolus. Both the modiolus and lam- ina are pierced by numerous openings for the passage of these nerves. The semicircular canals are three bony canals lying above and behind the vestibule, and communicating with it by five openings, in one of which two tubes join. They are known as the posterior, vertical, and horizontal canals, and their position is such that each one is at right angles to the other two. One end of each tube is enlarged and forms what is known as the ampulla. The membrane of the ampulla is covered with cells that are similar to those found in the utricle and saccule. These hair-cells serve as end organs for the vestibular branch of the auditory nerve. The auditory nerve. — The eighth or auditory nerve is a sensory nerve and contains two distinct sets of fibres, which differ in their function, origin, and destination. One set of fibres is known as the cochlear division and the other as the vestibular. The fibres of the cochlear nerve arise from bipolar cells that are situated in the modiolus of the cochlea. One axis cylinder from each cell passes through the foramina of the modiolus or lamina, and terminates in and around the cells that constitute the organ of Gorti. The other axis cylinder passes through the intepial auditory meatus to a portion of the brain, called the cochlear root of the auditory nerve. This root is located at the lower edge of the pons Varolii. The nerve-fibres which pass from the ear to the pons or from the pons to the ear are not continuous strands, as there are several relays of ganglia in which the axones of one cell interlock with the dendrites of another cell. 420 ANATOMY FOR NURSES [Chap. XX The fibres of the vestibular nerve haw their orighi in the gray matter of the pons \ arolii. Some of these fibres extend to the cerebelkim and to motor centres of the si)inal nerves. Other fibres extend to tlie vestibnle and are (Hstril)uted around the liair-eells of the saccule, utricle, and the ampulla of the semicircuhir canals. Physiology of hearing. — All bodies which produce sound are in a state of vibration, and communicate their vibrations to the air with which they are in contact. When these air-waves, set in motion by sonorous bodies, enter the external auditory canal, they set the drum-membrane vibrat- ing, stretched membranes taking up vibrations from the air with great readiness. These vibrations are communicated to the chain of tiny bones stretched across the middle ear, and their oscilla- tions cause the membrane leading into the internal ear to be alternatively pushed in and drawn out, and vibrations are in this way transmitted to the perilymph. The movements of the peri- lymph are transmitted to the basilar membrane, and set some of the strings in motion. In some unknown way tliese movements are transmitted to the hair-cells and through them to the nerve- fibres at their base. By means of the nerve-fibres the stimulus is conveyed to the brain and'interpreted there, so that it is with the brain that we hear. The sense of equilibrium. — Among the various means (such as sight, touch, and muscular sense) whereby we are enabled to maintain our equilibrium, coordinate our move- ments, and become aware of our po- sition in space, one of the most im- portant is the action of the vestibule and semicircular canals. Though these structures are found in the inner ear and communicate with the coch- lea, it is now thought that they are not connected with the sense of hear- ing. Just how they perform their function is not known, but it is thought that movements of the head set up movement in the endol^'mph of the canal, and this acts as a stimulus to the nerve-endings around the hair-cells. Fig. 196. — Diagram show- ing Relative Position of the Planes in which the Semi- circular Canals Lie. Rt., right ear; Lt., left ear; A.V., anterior vertical canal; P.V., posterior vertical canal ; H., horizontal canal ; a, ampulla of Rt. anterior vertical canal ; a', ampulla of Lt. posterior vertical canal. CiL\p. XX] INTERNAL AND EXTERNAL SENSES 421 The canals are so arranged (Fig. 196) that any movement of the head causes an increase in the pressure of the endol;^Tiiph in one ampulla, and a corresponding diminution in the ampulla of the parallel canal on the opposite side. Thus, a nodding of the head to the right would cause a flow of the endoh-mph from a to 6 in the right anterior vertical canal, but fror& h' to a' in the left poste- rior vertical canal. Hence the pressure upon the hairs is decreased in a, but increased in a'. Such stimulations of the sensory hairs are transmitted by the dendrites of the vestibular nerve, through the cell-bodies of the vestibular ganglion and the axis cylinders of the auditory nerve, to the pons Varolii and thence to the cere- bellum. It is thought that the cerebellum is the centre in the brain which interprets and adjusts the impulses that arise from stimula- tion of the sensory nerves concerned with muscular sense. It is also the centre that interprets and adjusts impulses that arise from stimulation of the vestibular nerve-endings. From this it follows that the cerebellum controls equilibrium. SIGHT The Adsual apparatus consists of the eyeballs, the optic nerves, and the nerve centres in the brain. In addition to these essential organs, there are accessory organs which are necessary for the protection and functioning of the eyeball. Accessory organs of the eye. — Under this heading we class : (1) eyebrows, (2) eyelids, (3) lacrimal apparatus, and (4) muscles of the eyeball. Eyebrows. ^ The eyebrows are composed of two arched emi- nences of thickened skin, covered with hairs. They are situated on the upper border of the orbits, and protect the eyes from too vivid light. Eyelids. — The eyelids are two folds projecting from above and below in front of the eye. They are covered externally by the skin, and internally by a mucous membrane, the conjunctiva, which is reflected from them over the globe of the eye. They are composed for the most part of connective tissue, which is dense and fibrous under the conjunctiva, where it is known as the tarsal cartilage. Arranged in a double or triple row at the margin of the lids are the eyelashes ; those of the upper lid more numerous and 422 ANATOMY FOR NURSES [Chap. XX longer than those of the lower. The upper lid is attached to a small muscle wliich is called the elevator of the upper lid (levator palpebraB superioris), and arranged as a sphincter around both lids is the orbicularis palpebrarum muscle, which closes the eyelids, and is the direct antagonist of the elevator of the upper lid. The slit between the e*dges of the lids is called the palpebral fissure. It is the size of this fissure which causes the appearance of large and small eyes, as the size of the lobe itself varies but little. The outer angle of this fissure is called the external can- thus ; the inner angle, the internal canthus. The eyelids are obviously provided for the profection of the eye; movable shades which by their closure exclude light, par- ticles of dust, and other injurious substances. Tarsal glands (Meibomian glands). — Embedded in the tarsal cartilage of each eyelid is a row of elongated sebaceous glands, — the tarsal ^ glands, — the ducts of which open on the edge of the eyelid. The secretion of these glands is provided to prevent adliesion of the eyelids. Lacrimal apparatus. — This apparatus consists of : (1) the lacrimal gland, (2) canaliculi, (3) lacrimal sac, and (4) nasal duct. The lacrimal gland is a compound gland, closely resembling the salivary glands in structure, and is lodged in a depres- sion at the upper and outer angle of the orbit. It consists of two portions, an upper por- tion about the size and shape of an almond, and a lower portion consisting of a group of small glands arranged in a row. These two portions are only partially separated by a fibrous septum. ' By everting the eyelids, these glands may be seen through the conjunctiva lying in parallel rows. Fig. 197. — The Lackimal Apparatus. (Note that preference is given to the spelling "lacrimal" as found in text, instead of "lachry- mal" as found on illustration.) Chap. XX] INTERNAL AND EXTERNAL SENSES 423 Seven to twelve minute ducts lead from the gland to the surface of the conjunctiva of the upper lid. The secretion (tears) is usually just enough to keep the eye moist, and after passing over the surface of the eyeball is sucked into two tiny canaliculi through the punctae and is conveyed into the lacrimal sac, which is the upper dilated portion of the nasal duct. The nasal duct is a membranous canal, about three-quarters of an inch (19 mm.) in length, which extends from the lacrimal sac to the nose, into which it opens by a slightly expanded orifice. The tears consist of water containing a little salt and albumin. They are ordinarily carried away as fast as formed, but under certain circumstances, as when the conjunctiva is irritated, or when painful emotions arise in the mind, the secretion of the lacrimal gland exceeds the drainage power of the nasal duct, and the fluid, accumulating between the lids, at length overflows and runs down the cheeks. The conjunctiva. — The conjunctiva is the mucous membrane which lines the eyelids and is reflected over the front of the eyeball. It is often considered part of the lacrimal apparatus as it secretes a fluid like that of the lacrunal gland. Muscles of the eye. — For purposes of description the muscles of the eye are divided into two groups : (1) intrinsic, and (2) extrinsic. The intrinsic muscles are the ciliary muscle, and the muscles of the iris. (See page 426.) The extrinsic muscles are those which move the eyeball and include the four straight, or recti, and the two oblique. They have been described in Chapter VII. Nerves of the eye. — The nerves which are supplied to the eye are: (1) the optic nerve, which is concerned with vision only; (2) the motor oculi nerve controls the internal rectus, the superior rectus, the inferior rectus, and the inferior oblique muscles; (3) the pathetic nerve controls the superior oblique muscle; (4) the abducens controls the external rectus; and (5) the ophthalmic, which is a branch of the trifacial nerve, supplies gen- eral sensation. The orbits. — The orbits are the bony cavities in which the eyeballs are contained. Seven bones assist in the formation of each orbit, namely, frontal, malar, maxilla, palate, etlmioid, sphenoid, and lacrimal. As three 424 ANATOMY FOR NURSES [Chap. XX of these bones are mesial (frontal, ethmoid, and sphenoid) there are only eleven bones forming both orbits. The orbit is shaped like a four-sided pyramid ; the apex, directed backward and inward, is pierced by a large opening — the optic foramen — through which the optic nerve and the ophthalmic artery pass from the cranial cavity to the eye. A larger opening to the outer side of the optic foramen — the sphenoidal fissure — provides a passage for the ophthalmic vein and the nerves which SUPERIOR RECTUS CHOROrO OPTIC NERVE iNFERIOBRfCTUS Fig. 198. — Diagrammatic Section of the Eye. (Flint.) carry impulses to and from the muscles, i.e. the motor oculi, the pathetic, the abducens, and the ophthalmic. The base of the orbit, directed outward and forward, forms a strong, bony edge for protecting the eyeball from injury. Each orbit averages about 2 inches (50 mm.) in depth, is lined with fibrous tissue, and contains a pad of fat, which serves as a support for the eyeball. A condition of emaciation is usually accompanied by sunken eyes, which results from the absorption of this fat, and the consequent sinking of the eyeballs in the orbits. Between the pad of fat and the eyeball is a serous sac — =- the capsule of Tenon — which envelops the eyeball from the optic nerve to the ciliary region and forms a socket in which the eyeball rotates. This sac secretes a lubricating fluid, the function of which is to prevent friction when the eyeball moves. Chap. XX] INTERNAL AND EXTERNAL SENSES 425 The eyebalL — The eyeball is spherical in shape, but its trans- verse diameter is less than the antero-posterior, so that it projects anteriorly, and looks as if a section of a smaller sphere had been engrafted on the front of it. The eyeball is composed of three coats, or tunics, and contains three refracting media or humors. They are as follows : — Tunics. — 1. Sclera and cornea. 2. Choroid, ciliary body, and iris. 3. Retina. Refracting media. — 1. Aqueous. 2. Crystalline lens and capsule. 3. Vitreous. The sclera. — The sclera, or " white of the eye," covers the posterior five-sixths of the eyeball. It is composed of a firm, unyielding, fibrous membrane, thicker behind than in front, and serves to protect the delicate structures contained within it, and maintain the shape of the eyeball. It is opaque, white, and smooth externally, and behind is pierced by the optic nerve. In- ternally it is stained brown where it comes in contact with the choroid coat. It is supplied with very few blood-vessels, and the existence of nerves in it is doubtful. The cornea. — The cornea covers the anterior sixth of the eye- ball. It is directly continuous with the sclera, which, however, overlaps it slightly above and below, as a watch crystal is over- lapped by the case into which it is fitted. The cornea, like the sclera, is composed of fibrous tissue, which is both firm and un- yielding, but, unlike the sclera, it has no color, and is perfectly transparent ; it has been aptly termed the " window of the eye." The cornea is well supplied with nerves and lymph-spaces, but is destitute of blood-vessels, so that it is dependent on the lymph contained in the lymph-spaces for nutriment. Choroid. — The choroid, or vascular coat of the eye, is a thin, dark brown membrane lining the inner surface of the sclera. It is composed of delicate connective tissue, the cells of which are large and filled with pigment, and it contains a close network of blood- vessels. The pigment cells and blood-vessels render this mem- brane dark and opaque, so that it darkens the chamber of the eye by preventing the reflection of light. It extends to within a short distance of the cornea. 426 ANATOMY FOR NURSES [Chap. XX BADIATING I VESSELS OF IBIS ' The ciliary body, — The ciHary body is located between the clioroid and tlie iris, and contains the ciliary processes, and the ciliary muscle. Just behind the edge of the cornea, the choroid is folded inward and arranged in radiating folds, like a phiited ruffle, around tlie lens. There are about seventy of these folds, and they constitute the ciliary processes. They are well supplied with nerves and blood-vessels, and also support a muscle, the ciliary muscle. The fibres of this muscle arise from the sclera near the cornea, and extending backward are inserted into the outer surface of the ciliary processes and the choroid. The action of this muscle determines the position of the lens. Iris. — The iris (iris, rain- bow) is a colored, fibro-muscu- lar curtain hanging in front of the lens and behind the cornea. It is attached at its circumference to the ciliary processes, with wliich it is practically continuous, and is also connected to the sclera and cornea at the point where they join one another. Except for this attachment at its circumference, it hangs free in the interior of the eyeball. In the middle of the iris is a cir- cular hole — the pupil — through which light is admitted into the eye chamber. The iris, like the choroid, is composed of con- nective tissue containing a large number of pigment cells and numerous blood-vessels. It contains, in addition, two sets of mus- cular fibres. One set is arranged like a sphincter with its fibres encircling the pupil, and is called the contractor of the pupil. The other set consists of fibres which radiate from the pupil to the Fig. 199. — Segment of the Iris, Ciliary Body, and Choroid. Viewed from the internal surface. (Gerrish.) Chap. XX] INTERNAL AND EXTERNAL SENSES 427 outer circumference of the iris, and is called the dilator of the pupil. The action of these muscle fibres is antagonistic. The posterior surface of the iris is covered by a thick layer of pigment-cells designed to darken the curtain and prevent the en- trance of light. The _^ anterior surface of the iris is also covered with pigment cells, and it is chiefly these latter which cause the beau- tiful colors seen in the iris. The different col- ors of eyes, however, are mainly due to the amount, and not to the color, of the pigment deposited. Function of the iris. — The function of the iris is to regulate the amount of light enter- ing the eye, and thus assist in obtaining clear images. It is enabled to perform this function by the action of the muscles described above, as their contraction or relaxation determines the size of the pupil. When the eye is accommodated for a near object, or stimulated by a bright light, the sphincter muscle contracts and diminishes the size of the pupil. When, on the other hand, the eye is accommodated for a distant object, or the light is dim, the dilator muscle contracts, and the pupil is pulled wider open. Retina. — The retina, the innermost coat of the eyeball, is the most essential part of the organ of sight, since it is the only one directly sensitive to light. The sclera is the protective, the choroid the vascular, or nutritive, and the retina is the visual, or perceptive, layer of the eyeball. It is a transparent mem- brane of a grayish color that is formed by the spreading out or expansion of the optic nerve. It is situated between the inner surface of the choroid and the outer surface of the vitreous humor, Fig. 200. — Choroid Membrane and Iris exposed by the removal of the sclera and Cornea. Twice the natural size, d, one of the segments of the sclera thrown back ; I and k, iris ; c, ciliary nerves ; e, one of the veins of the choroid. The ciliary muscle is crossed by the line from k, and should be represented as radiating. (Collins.) 428 ANATOMY FOR NURSES [Chap. XX and extends from the entrance of the optic nerve forward to the margin of the pupil. The retina is usually described as consisting of eight layers and two limitinii; membranes ; of these layers, three are most impor- tant : — (1) Eighth layer, or layer of nerve-fibres, is the internal layer. (2) Seventh layer is the layer of nerve-cells. (3) First layer, or layer of rods and cones, is the external layer. (See Summary, page 440.) The fibres of the optic nerve, after piercing the sclera and choroid at the back of the eye, spread out and form the eighth, or innermost, layer of the retina. The fibres then pass, with more or less direct communications, pe- ripherally through the other layers, until they may be said to terminate in the layer of rods and cones. Rays of light produce no efi'ect upon the optic nerve without the in- tervention of the rods and cones, which act as end organs. Blind spot. — The optic ner\e pierces the eyeball not exactly at its most posterior point, but a little to the iimer side. This point where the optic nerve enters is called the blind spot. There are no rods and cones at this spot, and rays of light falling upon it produce no sensation. Macula lutea. — There is one point of the retina that is of great importance, and that is the macula lutea, or yellow spot. It is situated about one-twelfth inch (2.08 mm.) to the outer side of the Fio. 201. — Diagrammatic bEcrioN of THE Human Retina. 8, layer of nerve- fibreo; 7, layer of nerve-cells; 1, layer of rods and cones. (M. Schultze.) Chap. XX] INTERNAL AND EXTERNAL SENSES 129 exit of the optic nerve, and is the exact centre of the retina. Li its centre is a tiny pit, — fovea centralis, — which is the centre of direct vision ; that is, it is the part of the retina which is always turned towards the object looked at. From this point the sensi- tiveness of the retina grows less and less in all directions. At this point (fovea centralis) are found none of the fibres of the optic nerve, but a great increase in the number of cones, as well as in their size. Perception of light. — 'Wlien light waves fall upon the retina they act as a stimulus, and it is supposed that they cause chem- ical changes in the rods and cones which give rise to im- pulses that are carried by the optic nerve to the brain, and result in sight. Just how this is accomplished is not known, but the rods contain a kind of pigment which is called visual purple, and this as well as the pigment of the retina may func- tion in these changes. The optic chiasm. — The fact that the two retinse and the two eyeballs work in unison is largely due to the crossing of the nerve fibres at the optic chiasm. The optic nerve from each eye passes backward through the optic foramen, and shortly after leaving the orbit the two nerves come together, and the fibres from the inner portion of each nerve cross. This is called the optic chiasm, and is really an incomplete crossing of fibres, as the outer fibres do not cross. (See Fig. 203.) Aqueous humor. — The space bounded by the cornea in front and by the lens, suspensory ligament, and ciliary body be- hind is filled with a colorless, transparent, watery fluid, the aqueous humor. This space is known as the aqueous chamber, and is' partially divided by the iris into an anterior and posterior chamber. Fig. 202. — The Posterior Half of THE Retina of the Left Eye viewed FROM Before. Twice its natural size, s, cut edge of the sclera ; ch, choroid ; r, retina ; in the interior at the middle, the macula lutea with the depression of the fovea centralis is represented by a slight oval shade ; toward the left side the light spot indicates the entrance of the optic nerve or blind spot. (Collins.) 430 ANATOMY FOR NURSES [Chap. XX Vitreous humor. — The posterior four-fifths of the globe of the eyeball is filled with a semi-fluid, gelatinous substance, the vit- reous humor, or body, so called from its glassy and transparent appearance. It is enclosed in a thin membrane — the hyaloid membrane. This mem- ^1 A brane is attached to the ^>~^r )jf^ retina at the back of the \ ^^ /^ eyeball, and furnishes a sus- p ic nerM \^k. /jW peusory ligament to the lens. Optic chiasm. — ■ \ ^^f^ Elscwhcre it is perfectly / y^^^^^^ separable from its surround- optic tract ^y/ ^%^ "^Ss- The vitreous humor enclosed in this capsule dis- FiG. 203. — DiAGR.wi OF Optic Chiasm. tends the greater part oi the sclera, supports the retina, which lies upon its surface, and preserves the spheroidal shape of the eyeball. Its refractive power, though slightly greater than that of the aqueous humor, does not differ much from that of water. Crystalline lens. — The crystalline lens is a transparent, refrac- tive body, with convex anterior and posterior surfaces, placed directly behind the pupil, where it is retained in position by the counterbalancing pressure of the aqueous humor and vitreous body, and by its own suspensory ligament described above. The posterior surface is considerably more curved than the an- terior, and the curvature of each varies with the period of life. In infancy, the lens is almost spherical ; in the adult, of medium convexity ; and in the aged, considerably flattened. It is a fibrous body, enclosed in an elastic, non-vascular capsule. Just beneath the capsule the substance is soft and gelatinous, but deeper it becomes hard and firm. Its refractive power is much greater than that of the aqueous or vitreous humor. Refraction. — Refraction is the bending or deviation in the course of rays of light in passing obliquely from one transparent medium into another of difl'erent density. (See page 496.) The refractive apparatus. — In order that our vision of objects looked at should be clear and distinct it is necessary that the rays of light entering the eye should be focussed on the retina. In the normal eye this is secured by the mechanism of accommodation (see next paragraph). The refractive apparatus consists of the Chap. XX] INTERNAL AND EXTERNAL SENSES 431 aqueous humor, the vitreous humor, and the crystalHne lens which have just been described. Accommodation. — Accommodation is the ability of the eye to adjust itself so that it can see objects at varying distances. Tlie changes which occur in the eye during accommodation for near objects are three in number : (1) the pupil contracts, (2) the lens becomes more convex, and (3) the axes of the eyeballs are turned inward by the action of the internal recti muscles. A normal eye is capable of distinct vision throughout an im- mense range. We can see the stars millions of miles away, and with the same eye, though not at the same time, we can see ob- jects within a few inches of us. To be able to see objects mill- ions of miles away and within a short range, the eye has to accommodate or adjust itself to different distances. This accom- modation is accomplished mainly by the lens changing its con- vexity. In accommodation for near objects, the lens becomes more convex (advances), and the pupil of the eye hkewise con- tracts. This convexity is brought about by the action of the ciliary muscle, and is always more or less fatiguing. The ac- commodation for distant objects is a passive condition, the convexity of the lens being unaltered and the pupil of the eye dilated, and it is on this account that the eye rests for an indefi- nite time upon remote objects without fatigue. Common conditions that affect accommodation. — The condi- tions that affect accommodation are : (1) hypermetropia, (2) myo- pia, (3) presbyopia, and (4) astigmatism. H3rpermetropia. — Hypermetropia or far-sightedness is a condi- tion in which rays of light from near objects do not converge soon enough and are brought to a focus behind the retina. This is usu- ally caused by a flattened condition of the lens or cornea, or an eyeball that is too shallow, and convex glasses are used to con- centrate and focus the rays more quickly. Myopia. — Myopia or near-sightedness is a condition in which rays of light converge too soon, and are brought to a focus before reaching the retina. This is the opposite of hj-permetropia and is caused by a cornea or lens that is too convex, or an eyeball of too great depth. To remedy this condition concave glasses are worn to disperse the rays and prevent their being focussed too soon. 432 ANATOMY FOR NURSES [Chap. XX Presbyopia. — Presbyopia is a defective condition of accom- modation in which distant objects are seen distinctly, but near objects are indistinct. This is a physiological process which affects every eye sooner or later, and is not due to disease. It is said to be caused by a loss of elasticity of the l^ns. Astigmatism. — Astigmatism is the condition in which the different meridians ^ of the cor- nea are not equally convex, and so there is interference with the formation of distinct images on the retina. Inversion of images. — Fol- lowing the general laws for the formation of images in connec- tion with the lens, an inverted image of external objects is formed on the retina. " The question then arises, WTiy is it that objects do not appear to us to be upside down ? This cannot be satisfactorily answered without entering into matters which require a previous psychologi- cal training. Suffice it to say here that the localization of objects in space depends not only on the retina, but also on tactile and general experience ; that the mind localizes objects with reference to its own body, and that from the first it knows nothing of the in- version of the retinal image, as its powers of localization only ap- pear with developing general experience." (Halliburton.) • The meridian of the eye is an imaginary line drawn around the eyeball. Fig. 204. — Diagram illustrating Ray.s of Light converging in (A) a Normal Eye, (B) a Myopic Eye, and (C) A Hyper.metropic Eye. Chap. XX] SUMMARY 433 SUMMARY ' Perception through the sense organs. Sensation Organs necessary for sensa- tion Classification < End organ for the reception of a stimulus. A nerve for conduction of the stimulus. A centre in the brain for the perception and interpretation. 1. Internal or those in which the sensa- tions are pro- jected to the in- terior of the body. 2. External or those in which the sensa- tions are pro- jected to the ex- terior of the body. Hunger. Thirst. Pain. Muscular sense. Fatigue. Visceral sensations . Pressure. Temperature. Taste. Smell. Hearing. Sight. Hunger Thirst Pain Presumably due to contractions of empty stomach, act- ing on nerves distributed to mucous membrane. In abnormal conditions it may be due to failure to assimi- late food. / Presumably due to stimulation of nerves of pharynx by 1 low water content in tissues. f May be due to stimulation of special nerve endings, or to I overstimulation of any of the sensory nerves. Muscular Sense — Due to stimulation of sensory nerves distributed to muscles. Weight or resistance serves as stimulus. Fatigue — Due to stimulation of sensory nerves distributed to muscles. Loss of nutrient material or accumulation of waste products acts as stimulus. Visceral Sensations — Due to stimulation of sensory nei-ves distributed to the \'iscera. r End organs distributed over entire surface of body. Pressure • | -^ j / Nerve filaments surround hair foUicles. i 1 Tactile or Meissner corpuscles. End organs distributed over entire surface of body. r Temperature higher than body. Hot spots I Carbon dioxide. Temperature { ^^^ organs J Electricity. ^ ( Temperature lower than body. Cold spots I Menthol. I Electricity. 2f 434 ANATOMY FOR NURSES [Chap. XX Taste Tongue 1. Taste-buds are end organs. Sensory &p- 2. Nerve-fibres of trifacial, facial, and glos- paratus | sopharyngeal nerves. . 3. Centre in brain. Solution of sapid substances must come in contact with taste-buds. (Surface of tongue. Soft palate and fauces. Tonsils and pharynx. Freely movable muscular organ. Attached to hyoid bone, epiglottis, and pillars of the fauces. ICircumvallate. Fungiform. Filiform. ■ Lingual, branch of trifacial. Nerves Sense of Sensory Motor — 1. Taste 2. Temperature 3. Pressure 4. Pain Chorda tympani, branch of the facial. Glossopharyngeal. Hypoglossal. Are all well developed. Smell Hearing C Olfactory nerve-endings. Sensory ap- olfactory nerve-fibres. para us |^ Centre in brain — olfactory bulb. I Minute particles of ( Must be capable solid matter < of solution in Gases I mucus. Olfactory nerve-ending found in lining upper part of nose (smell). Branches of trigeminal nerve found in lining of lower part of nose (pressure). ' External ear. Middle ear. Auditory ap- < Internal ear. paratus Auditory nerve. . Centre in brain. Air-waves enter external auditory canal and cause vibra- tions of drum-nicmbrane. The \4brations are conveyed to nerve-endings of organ of Corti, and thence by the auditory nerve to the brain. Chap. XXJ SUMMARY 435 Ear . Pinna, auricle or External Ear. Structure Fxmction Middle Ear - Cartilaginous framework, some fatty and muscular tissue, cov- ered with skin. Collects sound- waves and re- flects them into the audi- tory canal. ' 1 in. long, partly cartilage, partly bone. Closed inter- nally by the drum- membrane Hairs directed outward. Ceruminous glands secrete a yellow, pasty substance. An irregular cavity in the temporal bone. Five or six drops of water will fill it. r Malleus (hammer). < Incus (anvil). I Stapes (stirrup). ■ Fenestra ovalis — closed by a membrane and the stapes. Fenestra rotunda — closed by a membrane. Eustachian tube — con- nects with the pharynx, allows entrance of air. Auditory canal Membrana tympani. Bones Openings 436 ANATOISIY FOR NURSES [Chap. XX Internal ear Ear Vestibule — antechamber just inside of fenestra oralis . Semicir- cular canals Cochlea Auditory nerve Three in num- ber. Open into ves- tibule. Vestibular branch of audi- Bony tory nerve tlistributed to labyrinth I vestibule and semicircu- lar canals. A spiral tube. 2^ turns around modiolus. Fenestra ro- tunda. Cochlear branch of the audi- tory nerve. ' Surrounded by perilymph. Contains endoljTiiph. Lines the vesti- f Saccule, bule \ Utricule. Lines the semicircular canals. Lines the cochlea, and here Membranous i it is called the canalis labyrinth cochlearis, or scala media. Menibrana basilaris is name given to membrane at base of canal. Organ of Corti, name given to end organs of auditory nerve lodged on mem- brana basilaris. Cochlear — terminates in and around cells of organ of Corti. Vestibular — terminate in hair-cells of saccule, utricle, and ampulla. Chap. XX] SUMMARY 437 Sense of Equilibrium Sight Ascessory Organs Function of the vestibule and semicircular canals. Lining membrane supplied with sensory hairs which con- nect with vestibular nerve. Contain several small otoliths which float intheendoljanph. Flowing of the endolyraph stimulates the sensory hairs; this is transmitted to the vestibular nerve, thence to auditory nerve, thence to brain. ' Eye. Optic nerve. Centre in brain. Eyebrows. Accessory Eyelids. organs ] Lacrimal apparatus. Muscles. Vibrations in the ether enter eye and strike on retina, which contains end organs of the optic nerve; thence sensation is carried to visual centre in brain. Visual ap- paratus Eyebrows Eyelids Arched eminences of skin furnished with short, thick hairs. Control to a limited extent amount of light admitted to eye. ' Folds of connective tissue covered with skin, lined with mucous membrane (con- junctiva), which is also reflected over the eyeball. Provided with lashes. Closed by orbicularis palpebrarum muscle. Upper lid raised by levator palpebrae su- perioris. Slit between lids called palpebral fissure. Inner angle of slit called internal canthus. Outer angle of slit called external canthus. Function is protection. Serve as shades. Tarsal glands are a row of glands embedded in tarsal cartilage of each lid. 438 ANATOMY FOR NURSES [Chap. XX Accessory Organs Nerves of Eye Lacrimal apparatus Tears Consist of Lacrimal gland — in the upper and outer part of tlie orbit. Secretes tears. Ducts — 7 to 12 lead from gland to con- junctiva. Canaliculi — 2 canals y to ^ in. long, begin at punctae and open into lacrimal sac. Lacrimal sac — upper dilated portion of the nasal duct. Xasal duct — canal f in. long, extends from lacrimal sac to the nose. Secretion constant. Moisten the eyeball and help to moisten inspired air. f Water. { Salt. I Albumin. Carried off by nasal duct. ' Superior rectus. Inferior rectus. Internal rectus. External rectus. Superior obUque. , Inferior obUque. Determines the position of the I lens, r Contractor of pupil. I Dilator of pupil. ■ 1. Optic nerve concerned with vision only. Internal rectus muscle. Superior rectus muscle. Inferior rectus muscle. Inferior obUque muscle. 3. Pathetic controls the superior obUque muscle. 4. Abducens controls the external rectus muscle, l 5. Ophthalmic. Muscles Extrinsic Intrinsic Ciliary muscle Muscles of iris 2. Motor oculi controls Chap. XX] SUMMARY 439 Orbit Eyeball Bony cavity formed by seven bones Frontal. Malar. Maxilla. Palate. Ethmoid. Sphenoid. Lacrimal. Lined by fibrous tissue. Contains pad of fat — supports eyeball. Capsule of Tenon — prevents friction when eyeball moves. Shaped Uke four-sided pyra- J Apex directed backward. mid \ Base directed forward. Optic foramen — opening for passage of optic nerve and ophthalmic artery. Sphenoidal fissure — opening for passage of ophthalmic vein and motor oculi, pathetic and abducens nerves. ■ Spherical in shape. Transverse . . . 1.00 inch (25 mm.) Vertical 96 inch (24 mm.) Antero-posterior . .96 inch (24 mm.) Optic nerve and Dimensions I sheath 16 inch (4 mm.) Lens — ^ antero-pos- terior 19 inch (4.75 mm.) Lens — transverse .35 inch (8.75 mm.) Pupil (average) . .14 inch (3.5 mm.) Tunics Media 1. Sclera and cornea. 2. Choroid, ciliary body, and iris. 3. Retina. 1. Aqueous. 2. Crystalline lens and capsule. 3. Vitreous. Sclera Cornea Choriod Ciliary Body ( Tough, fibrous, opaque. Protective. I Covers posterior | of eyeball. I Stained brown internally. Fibrous, transparent — covers anterior I of eyeball. Well supplied with nerves, r Vascular coat, lines the sclera. I Composed of connective tissue cells filled with pigment. i Terminates in front by the ciliary processes. Ciliary processes 70 to 80 parallel folds of the choroid, rising gradually from behind and forming a plaited zone between the choroid and iris. Support ciliary muscle — action of this muscle determines the position of the lens. 440 ANATOMY FOR NURSES [Chap. XX Iris Retina Refractive Apparatus A circular curtain. Central perforation — pupil. Pupil contracted by circular muscle-fibres. Pupil dilated by radial muscle-fibres. Contains pigment — amount gf which determines color of the eyes. Hangs free except for attachment at circumference to the ciliar}' processes and choroid. Function — Regulates amount of light entering eye. Visual layer — transparent membrane of nervous and con- nective tissue situated between the choroid and vitreous humor. Formed by the spreading out of optic nerv'c. Has eight layers and two membranes. Counting from the choroid inward as follows : — Pigment layer, usually described as a membrane. 1. Layer of rods and cones (perceptive layer) — external layer. 2. Limitans externa, 3. External granules. 4. External molecular. 5. Internal granules. 6. Internal molecular. 7. GangUon or nerve-cells. 8. Optic nerve-fibres — innermost layer. Membrana Umitans interna. ( Entrance of optic nerve. < There are no rods and cones. [ Totally insensitive to light. 1^ in. outside the blind spot. Central pit — fovea centralis — is the centre of direct vision. Blind spot Macula lutea Aqueous Vitreous Crystal- line lens Aqueous chamber is between cornea in front and lens, suspensorj' ligament, and ciliarj' body behind. Aqueous humor is a colorless, trans- parent, watery fluid. ■ Semi-fluid, gelatinous substance. Fills the posterior four-fifths of the globe of the eyeball, and is enclosed in the hyaloid mem- brane. Distends the sclera and supports the retina. Situated behind the pupil. Double convex in shape. Fibrous body enclosed in an elastic capsule. Held in position by counterbalancing of the aqueous and vitreous humor and the sus- pensory ligament. Chap. XX] SUMMARY 441 Refraction — Bending or deviation in the course of rays of light, in pass- ing obUquely from one transparent medium into another of different density. Accommodation — AbiUty o£ the eye to adjust itself so that it can see objects at varying distances. Conditions that affect Accommo- dation Hypermetropia Myopia Presbyopia Astigmatism Far-sightedness. Cause — Rays of hght do not con- verge soon enough. Xear-sightedness. Cause — Rays of light converge too soon. Defective condition of accommodation in which distant objects are seen distinctly, but near objects are in- distinct. Condition in which the different merid- ians of the eye are not equally convex. Interferes with distinct CHAPTER XXI THE ORGANS OF GENERATION : PHYSIOLOGY OF REPRODUCTION Female generative organs. — The female generative organs are divided into an internal and an external group. The internal are contained within the pelvis, and the external are grouped under the name of vulva or pudendum. INTERNAL GENERATIVE ORGANS The internal generative organs comprise the following struc- tures : — (1) Ovaries, two glandular organs in which the ova are formed. (2) Fallopian [uterine] tubes, two canals through which the ova reach the uterine cavity. (3) Uterus, a hollow, pear-shaped organ, which receives the ovum. (4) Vagina, a canal extending from the uterus to the vulva. Ovaries. — The ovaries are two small, almond-shaped glandular bodies, situated one on each side of the uterus, in the posterior fold of the broad ligament, behind and below the Fallopian tubes. Each ovary is attached by its inner end to the uterus by a short liga- ment, — the ligament of the ovary, — and by its outer end to the Fallopian tube by one of the fringe-like processes of the fimbriated extremity. The ovaries each measure about one and a half inches (38 mm.) in length, three-fourths of an inch (19 mm.) in width, and one-third of an inch (8.5 mm.) in thickness, and weigh from one to two drachms (3.7 to 7.5 grams). Function. — The function of the ovaries is to produce, develop, and mature the ova, and to discharge them when fully formed. In addition, the ovary doubtless furnishes an internal secretion, which is picked up by the blood. Structure. — If the substance of an ovary be minutely examined it is found to consist of: (1) a stroma or bed composed of white 442 Chap. XXI] THE ORGANS OF GENERATION 443 and yellow fibrous tissue, blood-vessels, lymphatics, and nerves, (2) Graafian or vesicular follicles, and (3) a covering of columnar epithelial cells, called germinal epithelium, which is continuous with the peritoneum. Graafian (vesicular) follicles. — The Graafian follicles are sacs or vesicles which contain the ova and are embedded in the meshes of the stroma. Each follicle consists of : (1) an outer coat of fibrous tissue that is derived from the stroma, and connected with it by a plexus of Fig. 205. — Uterus, Fallopian Tubes, and Ovaries — Posterior View. 1, ovaries; 2, 2, uterine tubes; 3, 3, fimbriated extremity of the left uterine tube, seen from its concavity ; 4, opening of the left tube ; 5, fimbriated extremity of the right tube, posterior view ; 6, 6, fimbrise which attach the extremity of each tube to the ovary ; 7, 7, ligaments of the ovary ; 8, 8, 9, 9, broad ligaments ; 10, uterus; 11, cervix uteri ; 12, os uteri ; 13, 13, 14, vagina. (Sappey.) blood-vessels, and (2) an inner layer of nucleated cells. With the exception of the, smallest vesicles each one is filled with fluid, and suspended in this fluid is an ovum surrounded by a mass of cells, called the discus proligerus. At birth the ovaries are said to contain about 36,000 vesicles, each measuring from gro to j^ of an inch in diameter, but only a small number of these ever develop, as the great majority shrink and disappear. At the time of puberty the ovaries enlarge, be- come very vascular, and some of the follicles increase in size. As the follicles increase in size they approach the surface and begin to form small protuberances on the outside of the ovary. When 444 ANATOMY FOR NURSES [Chap. XXI fully matured the wall of the ovary and the wall of the follicle burst at the same point, and the contents of the follicle — the fluid, the ovum, and the surrounding cells — escape. This process of development, maturation, and rupture of a follicle is kncnvn as ovulation, and continues at regular intervals from puberty to the menopause. The corpus luteum. — After the rupture of a follicle, and the escape of the ovum, the walls collapse and the cavity becomes filled with blood which forms a clot. Later this clot becomes surrounded by cells containing a yellow pigment, which gives the follicle a yellow color, and hence it is known as the corpus luteum. The size and duration of the corpus luteum is dependent on whether fertilization occurs or not. If fertilization does not occur the cor- pus luteum increases in size for two or three weeks and then is ab- sorbed. If fertilization does occur and the woman becomes preg- nant, the corpus luteum increases in size during the first few months, and does not show retrogressive changes until about the sixth month. The function of the corpus luteum is unknown. Some physiologists regard it as a protective mechanism by means of which the cavity resulting from the rupture of the follicle is filled with a tissue which can be easily absorbed. Others attribute to the corpus luteum the formation of the internal secretion of the ovaries. This will be discussed later. Fallopian tubes. — The Fallopian tubes or oviducts are two in number, one on each side, and pass from the upper angles of the uterus in a somewhat tortuous course between the folds and along the upper margin of the l)road ligament, towards the sides of the pel- vis. They are about four inches (100 mm.) long, and at the point of attachment to the uterus are very narrow, but gradually increase in size so that the distal end is larger. The margin of the distal end is surrounded by a number of fringe-like processes called fim- briae. . One of these fimbrise is attached to the ovary. The uterine opening of the tube is minute, and will only admit a fine bristle ; the abdominal opening is comparatively much larger. The uterine tube consists of three coats : — (1) Serous. — The external, or serous, coat is derived from the peritoneum. (2) Muscular. — The middle, or muscular, coat has two layers : one a layer of longitudinal fibres and the other of circular fibres. Chap. XXI] THE ORGANS OF GENERATION 445 (3) Mucous. — The internal, or mucous, coat is arranged in longitudinal folds and covered with ciliated epithelium. It is con- tinuous at the inner end with the mucous lining of the uterus, and at the distal end with the serous lining of the abdominal cavity. This is the only instance in the body in which a mucous and serous lining are continuous with one another. Function. — The function of the Fallopian tubes is to convey the ova from the ovaries to the uterus. Just how the ovum, after its discharge into the abdominal cavity, reaches the Fallopian tube is not known. It is thought that the movement of the cilia on the fimbriae and in the tubes produces a current which draws the ovum into the tube. After the ovum enters the tube it is carried to the uterus by the peristaltic action of the tube and the move- ment of the cilia. It is considered probable that many of the ova discharged from the ovaries remain in the abdominal cavity, because of failure to reach the tubes. These ova disintegrate, are absorbed, and carried away by the blood. Occasionally such an ovum becomes impregnated and ectopic gestation results. The Uterus. — The uterus is a hollow, pear-shaped organ. In the virgin state it is situated in the pelvic cavity between the blad- der and the rectum. Its length is estimated to be about three inches (75 mm.), its width two inches (50 mm.), and its thickness one inch (25 mm.). During pregnancy the uterus becomes enormously en- larged, attains the length of a foot (300 mm.) or more, measures about eight to ten inches (200 to 250mm.) transversely, and extends into the umbilical region. After parturition the uterus returns to almost its original size, but is always larger than before pregnancy. After the menopause, the uterus becomes smaller and atrophies. Divisions. — For purposes of description the uterus is divided into three parts : the fundus, body, and neck. The fundus is the convex part above the entrance of the tubes. The body is the part between the fundus and the neck. The cervix or neck is the lower constricted part and extends from the body of the uterus into the vagina. The cavity of the uterus is small ; that part within the body is triangular in shape (v), and has three openings, one at each upper angle, communicating with the Fallopian tubes, and one, the internal orifice, opening into the cavity of the cervix below. The cavitv of the cervix, which is, of course, continuous with the cavity 446 ANATOMY FOR NURSES [Chap. XXI in the body, is constricted above, where it opens into the body by means of the internal orifice (internal os), and below, where it opens into the vagina by means of the external orifice (external os). Fig. 206. — Internal Organs of Generation. Showing the uterus in its nor- mal position between the bladder and the rectum. (Cooke.) Between these two openings the canal of the cervix is somewhat enlarged. Structure. — The walls of the uterus are thick and consist of three coats : — (1) An external serous coat derived from the peritoneum. It covers all of the uteru.s, and the posterior surface of the cervix, but not the anterior surface. (2) A middle muscular coat which forms the bulk of the uterine walls. It consists of layers of plain muscular tissue intermixed with blood-vessels, l\Tnphatics, and nerves. The arrangement of the muscle fibres is very complex, as they run circularly, longi- tudinally, spirally, and cross and interlace in every direction. (3) An internal mucous membrane, which is continuous with that lining the vagina and Fallopian tubes. It is highly vascular, pro- Chap. XXI] THE ORGANS OF GENERATION 447 vided with numerous mucous glands, and is covered with ciliated epithehum. Blood supply of uterus. — The uterus is abundantly supplied with blood-vessels. The blood reaches the uterus by means of the uterine arteries from the internal iliacs, and the ovarian ar- teries from the aorta. Where the neck joins the body of the uterus, the arteries from both sides are united by a branch vessel, called the circumflex artery. If this branch is cut during a surgical opera- tion, or a tear of the neck during parturition extends so far as to sever it, the hemorrhage is very profuse. The arteries are re- markable for their tortuous course and frequent anastomoses. The veins are of large size, and correspond in their behavior to the arteries. Position of the uterus. — The uterus is not firmly attached or ad- herent to any part of the skeleton. It is, as it were, suspended in the pelvic cavity, and kept in position by ligaments. A full bladder pushes it backward; a distended rectum, forward. It alters its position, by gravity, or with change of posture. During gestation it rises into the abdominal cavity. The fundus of the uterus is inclined forward, and the external orifice is directed downward and backward. (See Fig. 206.) Anteversion is the condition where the fundus turns too far forward. Retroversion is the condition where the fundus inclines backward. A bend may exist where the neck joins the body, and if the body is bent forward, it is described as anteflexion ; if bent backward, retroflexion. Ligaments. — The uterus is maintained in position by five ligaments. Three are arranged in pairs. 1. The broad, or lateral ligaments, two in number, are folds of peritoneum slung over the front and back of the uterus, and extending laterally to the walls of the pelvis. They are composed of two opposed, serous layers, and between these layers are found the following structures : (a) Fallopian tubes ; {h) the ovaries and their ligaments ; (c) the round ligaments ; {d) blood-vessels and lymphatics ; (e) nerves ; (f) some smooth muscle-fibres. The posterior fold covers the back of the uterus, and extends far enough below to also cover the upper one-fifth of the back wall of the vagina, when it turns up and is reflected over the anterior wall of the rectum. Thus the uterus, with and between its two 448 ANATOMY FOR NURSES [Chap. XXI broad ligaments, forms a transverse partition in the pelvic cavity, the bladder, vagina, and urethra being in the front compartment, and the rectum in the l)ack compartment. The smooth muscular fibres of the broad ligaments are derived from the superficial muscular layer of the uterus. They pass out between the serous folds and become attached to the pelvic fascia, and thus help to sustain the uterus. 2. The round ligaments are two rounded, fibro-muscular cords, situated between the folds of the broad ligament. They are about four and a half inches (113 mm.) long, and take their origin from the upper angle of the uterus (on either side) in front and a little below the attachment of the Fallopian tube. They extend forward and outward, and finally end in the tissues of the labia majora and mons Veneris. The round ligaments are composed of muscle- fibres, areolar tissue, blood-vessels, and nerves. 3. The utero-sacral ligaments extend between the cervix and sides of the rectum. They ser\'e to connect the cervix and % agina with the sacrum, and are partly serous, partly of smooth muscular fibres. 4. Anterior ligament. — Between the bladder and uterus the peritoneum forms a shallow pouch called the utero-vesical pouch. This peritoneum, which forms the floor of the pouch, is described as the anterior ligament of the uterus. 5. Recto-vaginal. — Behind the uterus the peritoneum forms a second and deeper pouch called the recto-vaginal, or cul-de-sac, of Douglas. This peritoneum is described as the recto-vaginal ligament. Function. — The function of the uterus is to receive the ovum from the Fallopian tubes, and if it becomes fertilized to retain it during its development. Later when the ovum has developed into a mature foetus, it is expelletl from the uterus, chiefly by the contraction of the uterine walls. The Vagina. — The vagina is a musculo-membranous canal which encircles the lower portion of the cervix, and extends downward and forward from the uterus to the \Tjlva. The posterior wall is about three and a half inches (88 mm.) long, while the anterior wall is only three inches (75 mm.). The front, or anterior wall, is united by connective tissue with the posterior walls of the bladder and urethra, the partition, or septum, Chap. XXI] THE ORGANS OF GENERATION 449 between the bladder and vagina being called the vesico- vaginal, and that between the urethra and vagina the urethro-vaginal, septum. Structure. — The vagina is made up of three coats : an outer, fibrous ; middle, muscular ; and inner, mucous, which in the ordinary contracted state is thrown into fold, sits anterior and posterior walls being in contact. The muscular coat increases during pregnancy, and the mucous coat, because of the transverse PREPUCE OF. CLITORIS CLANS CLI TORIOIS Fig. 207. — Sagittal Section of the Vagina and Neighboring Parts. (Gerrish.) folds, or rugae, allow of dilatation of the canal during labor and birth. THE EXTERNAL ORGANS As previously stated the external organs of generation are grouped under the name of vulva or pudendum and include the following : — 1. Mons Veneris 4. The Clitoris 2. Labia Majora 5. The H^men 3. Labia ^Minora G. Glands A'ulvo-vaginal Urethral Mons Veneris. — The mons Veneris is an eminence situated in front of the pubic bones. It consists of areolar, adipose, and fibrous tissue covered with skin and after puberty with hair. 2g 450 ANATOMY FOR NURSES [Chap. XXI Labia majora. — The labia majora (" greater lips ") are two longitudinal folds of skin containing adipose and connective tissue. They are continuous with the mons Veneris in front, and extend to within an inch (25 mm.) of the anus behind. Labia minora. — The labia minora ("smaller lips") are two longitudinal folds of modified epithelium situated between the MONS VENERIS Fro. 208. — Vulva of a Virgin. The labia have been widely separated. Foss. Nav., fossa navicularis ; Int. Vag., introitus vaginae ; Lab. Miu., labium minus; Vestib., vestibule. (Gerrish.) labia majora. They are joined anteriorly in the hood or prepuce of the clitoris, and extend downward and backward for about one and one-half inches (38 mm.). The clitoris. — The clitoris is a small body situated at the apex of the triangle formed by the junction of the labia minora. It contains many vessels and nerves and is almost completely covered by the hood or prepuce. Chap. XXI] THE ORGANS OF GENERATION 451 The hymen. — The hymen is a fold of mucous membrane which surrounds the lower part of the vaginal orifice and renders the orifice smaller. Occasionally it extends entirely across and closes the orifice altogether. This condition is spoken of as imperforate hymen. Glands. — In connection with the vulva are found — (1) Vulvo-vaginal glands or glands of Bartholin. (2) Urethral glands. The vulvo-vaginal are two round, or oval, glands, situated on either side of the vagina. Their ducts open into the vulval canal, one on either side, in the groove between the hymen and labia minora. Their secretion lubricates the vulval canal. The urethral glands are found chiefly beneath the walls and floor of the urethra. They secrete mucus. Perineimi. — The perineum properly signifies the parts bounded by the outlet of the pelvis, but we generally apply it to the tri- angular portion between the vagina and rectum. It is made up of muscles strengthened with very strong fasciae, and covered v/ith skin. It is distensible, and stretches to a remarkable extent during labor. Nevertheless it is frequently torn, and when the tear is of any extent, and is not repaired, the vagina and uterus lose the support afforded by it, and various abnormal conditions follow. PHYSIOLOGY OF THE FEMALE GENERATIVE ORGANS Ftmction, — The function of the female generative organs is : (1) the formation and development of the ovum, (2) the reten- tion and sustenance of the fecundated ovum until it develops into a mature foetus ready to live outside the body, and (3) the expulsion of the foetus. Puberty. — Puberty is the period at which the sexual organs become matured and functional and the girl develops into a woman. The event is not accomplished at once, but extends over considerable time. The girl undergoes a gradual change in figure, the hips broaden, the breasts develop, and for the first time a menstrual flow is noticed. At first the menstrual periods are scanty and irregular, but after a few months they settle down to the characteristic rate and duration. In temperate climates 452 ANATOMY FOR NURSES [Chap. XXI the age at which girls usually attain puberty is about foiuteen years. In southern countries it is somewhat earlier, and in the arctic regions, a year or two later. However, no fixed rule can be given, as the time of arrival at puberty varies with every individual, depending on race, temperament, hygiene, and general surround- ings. The period preceding puberty, during which the physical changes are occurring, is known as the period of adolescence. Ovulation. — Ovulation includes the process of the develop- ment and maturation of the follicle and its ovum, and the rupture of the follicle. The commonly accepted theory is that about or shortly before the age of puberty the Graafian follicles begin to discharge their ova, and that this process continues until the menopause. The frequency with which well-developed ova are discharged is the subject of much dispute. The most conservative view is that there is one mature ovum discharged for each menstrual epoch, probably some days before the period occurs. Menstruation. — Menstruation consists of the periodical discharge of bloody fluid from the uterine cavity, "\^^len once established it occurs on the average every twenty-eight days from the time of puberty to the menopause, with the exception of the periods of pregnancy and lactation. The average duration is from four to five days and the amount of blood lost is about six ounces. The menstrual fluid consists of mucus, epithelial cells, and blood. Some authorities are of the opinion that the mucous membrane of the uterus is normally shed during this process, others do not share this opinion. The menopause or climacteric. — By menopause or climacteric is meant the physiological cessation of the menstrual flow, and the end of the period during which the Graafian follicles develop in the ovaries, and consequently the end of the child-bearing period. It is marked by atrophy of the breasts, uterus, tubes, and ovaries. The age of menopause varies as does the age of puberty ; in general, we may say the earlier the puberty the later the menopause, and vice versa. In temperate climates the average period tor the arrival of the menopause is at the age of forty-five years. Changes in the generative organs in connection with menstrua- tion. — At the beginning of menstruation there is a general con- Chap. XXI] THE ORGANS OF GENERATION 453 gestion of the generative organs, including the breasts, accom- panied by more or less discomfort and even pain. The mucous membrane of the uterus undergoes the following changes : (1) there is marked hypertrophy and congestion of the mucous membrane, (2) during menstruation there is capillary hemorrhage and the epithelium of the mucous membrane is cast off, (3) following menstruation a new epithelium is formed and the mucous mem- brane returns to its normal size. Comiection between ovulation and menstruation. — Whether ovulation depends upon menstruation or menstruation upon ovulation, or whether either has any connection with the other, is a matter of lengthy controversy. At the present time the generally accepted view is that menstruation is dependent upon the ovaries, and that their influence is exerted through the medium of the blood. It is thought that an internal secretion is formed in the ovaries, possibly by the corpus luteum. This secretion is carried to the uterus by the blood and is responsible for the hyper- trophy and congestion that precedes menstruation. So far it has not been possible to decide whether the internal secretion is en- tirely responsible for menstruation, or whether it is partly due to a power inherent in the uterine muscle. The fact that operations for the removal of the ovaries are followed by atrophy of the uterus and cessation of menstruation, supports the theory that the ovaries are responsible for menstruation. Purpose of menstruation. — The purpose of the hypertrophy and congestion of the uterus is thought to be nature's way of preparing the uterine walls for the reception of the ovum should it become fertilized. Mammary glands. — The two mammary glands, or breasts, may be considered as accessory organs of generation. Function. — The function of the mammary glands is to secrete the milk which is needed for the nourishment of the young infant. Location. — Each breast covers a nearly circular space in front of the pectoral muscles, extending from the second to the sixth rib, and from the sternum to the border of the arm-pit. Structure. — The breasts are covered externally by skin, are convex in shape, and about the centre of the convexity a papilla projects, which is called the nipple. The nipple contains the 454 ANATOMY FOR NURSES [Chap. XXI openings of the milk ducts, and is surrounded by a small circular area of pink or dark colored skin, which is called the areola. The areola is dotted over with projections formed by the sebaceous glands. They are compound glands, and are divided by connec- tive tissue partitions into about twenty lobes, each of which PCCTORALIS MAJOR fibrous septum guano substance Kdipose tissue THIRD RIB AREOLAR TISSUE FIRST RIB SECOND RIB PCCTORALIS MINOR INTERCOSTALES SHEATH OF PEC- TORALIS MAJOR SUPERFICIAL FASCIA FOURTH RIB LUNG ADIPOSE TISSUE HORIZONTAL PLANt OF NIPPLE SIXTH RIB Fig. 209. — Bight Breast in Sagittal Section, Inner Surface of Outer Segment. (Gerrish.) possesses its own excretory duct, which as it approaches the top of the breast dilates and forms a small reservoir in which milk can be stored during the period when the gland is active. Each duct opens by a separate orifice upon the surface of the nipple. The lobes are subdivided, and the small lobes, or lobules, are made up of the terminal tubules of the duct, which lie in a mesh of fibrous areolar tissue containing considerable fat. Chap. XXI] THE ORGANS OF GENERATION 455 Blood-vessels and nerves. — The mammary glands are well supplied with blood brought to them by branches of the axillary, internal mammary, and intercostal arteries. The nerves are chiefly intercostal nerves. Development of the mammary glands. — The increase in the size of the mammary glands at the time of puberty is due to an increased development of the connective tissue and fat. The glandular tissue remains undeveloped and does not function unless conception takes place. When conception occurs the glandular tissue undergoes a process of gradual development that produces marked changes. The breasts become larger and harder, the veins on the surface become more noticeable, the areola becomes enlarged and darkened, the nipple becomes more prominent, and toward the end of pregnancy a fluid called colostrum can be squeezed from the orifice of the ducts. After delivery the amount of colostrum increases for a day or two, and then its composition changes to that of milk. The primary development and later functioning of the mam- mary glands suggests an intimate connection between these glands and the uterus and ovaries. The present theory is that the in- crease in the size of the breasts at the time of puberty is influenced by the internal secretion of the ovaries, for if the ovaries are re- moved before puberty, the breasts do not develop, or if the ovaries are removed after puberty, the breasts are apt to atrophy. The development of the glandular tissue that follows conception is thought to be due to some chemical substance that results from the metabolism of the foetus. The chemical nature of this substance is not known, but presumably it stimulates the development of the gland, and also prevents secretion, as active secretion does not commence until after delivery, and if conception occurs during the months of lactation, the character of the milk is changed and its secretion checked. The stimulus which causes the active secre- tion of milk is thought to result from the emptying of the milk ducts, because of the fact that when a woman does not nurse her infant, the secretion of milk is checked, and the breasts return to their usual size. The active secretion of milk is also influenced by the nervous system, and this influence is probably exerted through the vasomotor nerves which control the size of the blood- vessels, and consequently the amount of blood sent to the gland. 456 ANATOMY FOR NURSES [Chap. XXI The secretion of milk. — The secretory portion of the mammary glands are the milk ducts, and these are lined with secreting cells. Some of the constituents of the milk, i.e. water, salts, and sugar, are secreted by these cells from the blood, but it is thought that the cells themselves disintegrate and form the proteins and fat. The sugar contained in the milk is lactose, and the sugar of the blood is glucose, so if the first is derived from the second, some chemical change must take place either during or after secretion. Colostrum and milk. — The secretion of the mammary glands during the first few days of lactation is called colostrum. It is a thin, yellowish fluid, composed of proteins, fat, sugar, salts, and water, but not in the same proportion as in milk. It also contains numerous cells containing large masses of fat. These are called colostrum corpuscles, and are secreting cells that are not completely broken down. Human milk is specially adapted to the requirements of the infant and so diflFers in some respects from that of all other animals. Cow's milk is most frequently substituted for human milk and the relative composition of the two can be seen in the following table : — Human (average) Cow's (average) Water 87.30% 1.50% 4.00% 7.00% 0.20% 87 00 % Proteins Fat Lactose Salts 4.00% 4.00% 4.30% 0 70% In substituting cow's milk for human milk the differences that must be taken into consideration are not only the different relative proportions, but also the following : (1) the difference in the pro- teins ; the protein of human milk is one-third caseinogen, and two- thirds lactalbumin, and that of cow's milk is five-sixths caseinogen and one-sixth lactalbumin ; (2) the difference in the curds formed in the stomach ; human milk curdles in small flocculi, and cow's milk curdles in large heavy curds ; and (3) the reaction of both human and cow's milk is amphoteric, but cow's milk is more nearly acid than human milk. Chap. XXI] THE ORGANS OF GENERATION 457 Male generative organs. — The male generative organs consist of the following structures : — Testes, two glandular organs which produce the spermatozoa. Vas Deferens Seminal Vesicles Ejaculatory Ducts The Scrotum The Spermatic Cords The Penis The Urethra The Prostate Gland Cowper's Glands Testes. — The testes are two glandular organs which are sus- pended from the inguinal region by the spermatic cords, and are surrounded and sup- ported by the scrotum. Each gland weighs from five to eight drachms (18.5 to 30 grams) and consists of two por- tions : (1) the testicle proper, and (2) the epididymis. (1) The testicle proper is ovoid in shape and covered exteriorly by fibrous tissue which sends incomplete parti- tions into the central portion of the gland, dividing it into commu- nicating cavities. In these cavities are wind- ing tubules which are surrounded by blood- vessels and held together by interstitial tissue. These tubules inosculate in a sort of mesh (rete testis) and finally all unite in the epidid.>Tnis. Fig. 210. — Male Sexual Apparatus. (Hall.) 458 ANATOMY FOR NURSES [Chap. XXI (2) The epididymis is a long, narrow body which Hes along the posterior portion of the testicle and consists of a tortuous tubule, which is lined with mucous membrane, and contains some muscular tissue in its walls. If unravelled it is found to be about twenty- feet (5 metres) long. It connects the testicle proper with the vas deferens. Function. — The function of the testes is the production of sper- matozoa. These spermatozoa are the essential part of the seminal fluid. The spermatozoa originate in the cells of the testes lining the tubules which compose the bulk of the testes. An internal secretion is also supposed to be formed here. Descent of the testes. — In early fcetal life the testes are abdominal organs lying in front of and below the kidneys. Dur- ing the process of growth they are drawn downward through the inguinal canal and shortly before birth are normally found in the scrotum. Sometimes, particularly in premature infants, the testis is found in the inguinal canal or even in the abdominal cavity ; as a rule it soon descends and occupies its proper posi- tion ; but occasionally it does not descend and an operation is necessary. The vas deferens. — The vas deferens is a continuation of the epididjinis, and is the excretory duct of the testicle. After a very devious course it joins the duct of the seminal vesicle at the base of the bladder. It consists of three coats, an external areolar, a middle muscular, and an internal mucous coat. The seminal vesicles. — The seminal vesicles are two pouches which are placed each one on the outer side of each vas deferens, between the bladder and the rectum. They are pyramidal in form, with the broad ends directed backward and widely separated. The anterior portions converge, become narrowed, and unite on either side with the corresponding vas deferens to form the ejacu- latory duct. Function. — The seminal vesicles serve as a reservoir for the semen, to which they add a secretion of their own. The ejaculatory ducts. — The ejaculatory ducts are two in niun- ber, one right and the other left. They are formed by the union of the seminal vesicle and vas deferens of each side. They run downward and converge as they descend, enter and pass between the lobes of the prostate gland and open into the floor of the pros- Chap. XXI] THE ORGANS OF GENERATION 459 tatic portion of the urethra. Each has an external areolar, middle muscular, and internal mucous coat. The scrotum. — The scrotum is a pouch which contains the testes and a part of each spermatic cord. It consists of a layer of skin, and the dartos. The skin is thick and dark, presents folds or rugae, is furnished with sebaceous glands, and covered with short hairs. The dartos is a thin tunic of a reddish color consisting of muscular fibres and elastic tissue and containing numerous blood- vessels. It is continuous with the superficial fascia of the groin and perineum. It sends in a partition, which separates the two testes. The spermatic cord, — The spermatic cord forms the pedicle of each testis and extends from the internal abdominal ring to the back of the testis. Each cord consists of the vas deferens, arteries, veins, lymphatics, nerves, the layers of fascia which cover the testis, and the remains of the peritoneal testicular process. These parts are connected together by areolar tissue. The penis. — The penis consists of three more or less cylindrical bodies of erectile ^ tissue enclosed in fibrous sheaths. The two corpora cavernosa lie above and receive between them below the corpus spongiosum, in which the urethra is contained. The glans penis is continuous with the corpus spongiosum. The cov- ering of the penis is of loose skin, but over the glans penis and lining the prepuce it resembles mucous membrane. In this region there is an abundant subcutaneous nerve plexus and numerous Pacinian ^ corpuscles, so that it is possessed of acute sensibility. The urethra. — The urethra extends from the bladder through the corpus spongiosum to the end of the penis. It is usually di- vided into three parts: (1) the prostatic urethra, (2) the mem- branous urethra, and (3) the penile or spongy portion. The length is usually given as eight inches (200 mm,), a large part of which lies inside the pelvis. It is lined with mucous membrane and furnished with numerous muscular fibres. ' Erectile tissue is found in the clitoris, penis, and the nipples. The form, size, and consistency of this tissue change according to the amount of blood contained in it. An increased amount of arterial blood causes swelling, and consequent press- ure on, and occlusion of, the veins. 2 Pacinian corpuscles are specialized nerve-endings found in the genital organs of both sexes, also in the palms of the hands, and the soles of the feet. (See Fig. 177.) 460 ANATOMY FOR NURSES [Chap. XXI The prostate. — The prostate gland is situated in front of the neck of the bladder and around the commencement of the urethra. It resembles a chestnut in form and consists of a dense fibrous capsule containing glandular and muscular tissue. The glandular tissue consists of tubules which communicate with the urethra by minute orifices. Function. — The function of the prostate gland is to secrete the prostatic fluid, which is an essential element of the seminal fluid. Cowper's glands. — These are two small bodies about the size of a pea situated one on each side, adjacent to, and opening into the membranous urethra. They secrete a fluid which goes to form part of the seminal fluid. Puberty. — This occurs in the male about a year later than in the female, about fifteen years of age. At this time the " Adam's Apple " develops, producing a marked change in the voice, the ex- ternal genitals grow somewhat rapidly, hair grows on the face, pubes, axillae, and other parts of the body, and seminal fluid begins to be secreted. At the same time sexual desires unknown before are experienced. Semen. — The semen is a fluid derived from the various sexual glands in the male. The main elements in this fluid are the sper- matozoa ; the other constituents are derived from the seminal vesicles, prostate gland, and Cowper's glands. PHYSIOLOGY OF REPRODUCTION Reproduction. — The purpose of reproduction is the continua- tion of the species, and is accomplished by means of the reproduc- tive organs, whose importance is in their adaptation to produce another being. Impregnation. — The term impregnation or fertilization is ap- plied to the union of the spermatozoon or male cell, with the ovum or female cell. The ovum. — The ovum is a minute globular cell about j^-g inch (0.2 mm.) in diameter. The component parts have received special names. The ceU-wall is a thick, surrounding envelope, or membrane, called the vitelline membrane. Chap. XXI] THE ORGANS OF GENERATION 461 The cell-body is a mass of cytoplasm filled with fatty and albuminous granules, and usually called the vitellus. The cell nucleus, or germinal vesicle, is a transparent, sharply outlined nucleus, embedded in the vitellus. The nucleolus, or germinal spot, is a small, dark spot situated in the fluid nucleus. The cell-body or cytoplasm contains the food material, and the nucleus contains chromatin material. Chromatin is of special interest because it is believed that it is through the chromatin material that hereditary characteristics are transmitted. The spermatozoon. — The spermatozoon is the male generative cell and its function is to fertilize the ovum and produce impregna- tion. It is much smaller than the ovum, being only 5^ inc^ (0.1 mm.) in length. It consists of an elliptical head, a rod-shaped middle piece, and a tail that gradually tapers. The head contains nuclear material and chromatin. There is an active vibratory motion of the tail which allows it quite free motion in the seminal fluid. Because of this free motion the spermatozoa are able when depos- ited in the vagina to travel upward into the uterus, and into the tubes even against the current produced by the cilia of the tubes. Site of impregnation. — It is thought that impregnation takes place in the Fallopian tubes. When the Graafian follicle ruptures and an ovum escapes into the abdominal cavity, the current pro- duced by the cilia of the tubes is thought to draw it into the tube. Once in the tube the peristaltic action of the tube and the action of the cilia propel it slowly along to the uterus. If the ovum does not become impregnated it passes into the uterus and is cast off in the next menstrual flow. If, however, it comes in contact with the spermatozoon in its passage through the tube, the spermato- zoon enters the ovum and segmentation or the process of cell divi- sion begins at once. Segmentation. — After the union of these two, the cell rapidly divides into two, each of these two into other two, and so forth, until we have a number of cells where formerly there was one. At this stage the collection of cells is called the blastoderm. Grad- ually these cells which constitute the blastoderm become arranged in three layers, the outer called the ectoderm, an inner called the entoderm, and a middle layer called the mesoderm. (See page 27.) 462 ANATOMY FOR NURSES [Chap. XXI The passage of the fertiUzed ovum through the tubes requires about eight days, and during this time many thousands of cells are formed and enclosed in a sac called the amnion. The collection of cells surrounded by the amnion is called an embryo. After entering the uterus the embryo attaches itself to the mucous mem- brane, in the upper portion, usually near the opening of the Fallopian tubes. Changes in the uterine lining. — The preparation of the mucous membrane of the uterus for the reception of the impregnated ovum includes changes that are similar to those that precede menstrua- tion. The mucous membrane becomes softer, thicker, and highly congested. In this condition it is known as the decidua vera, and the point to which the ovum becomes attached and whicji later develops into the placenta is called decidua scrotina. Intrauterine growth. — During the period of intrauterine life growth takes place rapidly. From the union of the ovum, which is ll^ inch (0.2 mm.) in diameter, and the spermatozoon, which is much smaller, there is developed in two weeks' time an embryo which is about the size of a bean. At the end of four weeks it is the size of a walnut, and at four months it is called a foetus, because it has the appearance of a human being, with well-developed eyes, fingers and toes separated, and the external genitals sufficiently formed to determine the sex. The usual duration of pregnancy is nine lunar or ten calendar months, but at the end of sLx months the foetus is sufficiently developed to live outside the mother's body, but it is fragile and requires a great deal of care. For further details on the subject of reproduction the student is referred to standard works on physiology and obstetrics. Chap. XXI] SUMMARY 463 SUMMARY Female Generative Organs Internal organs External organs Ovaries Ovaries — two glandular organs in which the ova are formed. Fallopian tubes — two canals through which the ova reach the uterine cavity. Uterus — a hollow, pear-shaped organ which receives the ovum. Vagina — a canal that extends from the uterus to the vulva. Mons Veneris — a cushion of areolar fibrous and adipose tissue, in front of pubic bones, covered with skin and after puberty with hair. Labia majora — two folds that extend from the mons Veneris to within an inch of the anus. Labia minora — two folds situated between the labia majora. CUtoris — small body, situated at apex of the triangle formed by junction of labia minora. Well supplied with nerves and blood-vessels. Hymen — fold of mucous membrane that sur- rounds vaginal orifice. ' Vulvo-vaginal — oval bodies situated on either side of the vagina. Urethral — glands found chiefly be- neath the walls and floor of urethra. Two almond-shaped glandular bodies. Situated in posterior fold of broad ligament. To uterus — by hgament of ovary. To tubes — by fimbriae. If inches long, f inch wide. [ I inch thick. Weight — 1-2 drachms. Fibrous tissue. Blood-vessels, Lymphatics. Nerves. Graaf- ian fol- licles Covering of germinal epithelium. J Produce, develop, mature, and discharge ova. \ Form an internal secretion. Glands Attached Size Structure Stroma " 1. Outer coat fibrous tissue. 2. Inner layer of cells contain ovum. Function 464 ANATOMY FOR NURSES [Chap. XXI Fallopian Tubes Uterus- V^agina Location Divisions < Three coats Enclosed in layers of broad ligament. Extend from upper angles of uterus to sides of pelvis. 1. Isthmus — or inner constricted portion near portion which curves Divisions Three coats Blood- vessels Isthmus - uterus. Ampulla — dilated over ovary. Infundibulum — trumpet-shaped extremity — fimbriae. External, or serous. Middle, or muscular. Internal, or mucous, arrranged in longitudinal folds and covered with cilia. Function — Convey ova to uterus. Hollow, thick-walled organ, placed in pelvis between bladder and rectum. Fundus = rounded upper portion, above the entrance of the tubes. Body = portion below fundus, above neck. Cervix = lower and smaller portion which ex- tends into vagina. ■ External, or serous, derived from peritoneum. {Circular fibres "i Interlaced in Longitudinal fibres > every direc- Spiral fibres J tion. Mucous membrane, lines the uterus. Uterine arteries from internal iliacs. Ovarian arteries from aorta. Remarkable for tortuous course and frequent anastomoses. ■ Broad, or lateral — two layers of serous mem- brane. Round — two fibro-muscular cords. Utero-sacral — two partly serous, partly mus- cular, ligaments. Anterior — peritoneal floor of the utero-vesical pouch. Recto-vaginal — peritoneal floor of the recto- vaginal pouch. Function — To receive ovum, and if it becomes fertiUzed to retain it until developed and then to expel it. Canal — Ebctends from uterus to vulva. C Outer coat is fibrous. { Middle coat is muscular. [ Mucous coat, or lining, arranged in rugae. Location — Placed between urethra and rectum. Ligaments ' Three coats Chap. XXI] SUMMARY 465 Physiology of Gen- erative Organs Changes in connection with men- struation Connection between ovu- lation and menstruation Mammary Glands Function ( ^o^^^ation and development of ovum. I Retention and sustenance of fecundated ovum. Puberty — Age at which sexual organs become matured and functional. Girl changes to woman. Ovulation / ^^°^*^^^ ^^ development and maturation of fol- [ licle and ovum, and discharge of ovum, f A flow of blood from the uterus. Occurs on an average every twenty-eight days. Extends from puberty (14 years) to the menopause, or climacteric (about 45 years). This period represents the child-bearing period of a woman's life. 1. General congestion of genera- tive organs including breasts. 2. Hypertrophy and congestion Menstrua- I connection I of mucous membrane of tion 1 with men- I uterus. Capillary hemorrhage. Epi- thelium is cast off. Following menstruation a new epithehum is formed. ' Probably dependent on internal secretion of ovaries, and pos- sibly is aided by power in- herent in uterine muscle. Purpose — Nature's way of preparing uterine I walls for reception of fertilized ovum. I Menopause — Physiological cessation of the menstrual flow. Accessory organs of generation. Function — To secrete milk to nourish infant. Location / ^^^nd from second to sixth rib. I Sternum to arm-pit. ' Outer surface convex — papilla projects from centre — called nipple — contains openings of milk ducts. Nipple surrounded by areola. Consists of connective tissue framework which divides the gland into about twenty lobes. Lobes are subdivided into lobules. Lobules are made up of the terminal tubules of the duct. Each lobe possesses its own excretory duct, I which is called lactiferous and is sacculated. r Axillary. < Internal mammary. I Intercostal. Structure Blood- vessels 2h 466 ANATOMY FOR NURSES [Chap. XXI Mammary Glands Colostrum MUk Nerves Develop- ment Secretion of milk Male Gen- erative Organs Intercostal. Primary development at time of puberty, prob- ably due to internal secretion of ovaries. Functional development follows conception, probably due to chemical substances that result from metabolism of foetus. Active se- cretion stimulated by emptying milk ducts and influenced by nervous system. Water \ Salts > Secreted from blood. I Sugar J Proteins Fat Formed by disintegration of cells lining lactiferous tubules. Thin yelIo\A'ish fluid secreted during first few days of lactation. Composi- tion Composi- tion Proteins Fat . Sugar Salts . Water Water . Proteins Fat . . Lactose Salts Human 87.30 % 1.50% 4.00 % 7.00 % 0.20 % 5.71 per cent 2.04 per cent 3.74 per cent 0.28 per cent 88.23 per cent 100.00 per cent Cow's Differ- ences 100.00 % Diff'erent relative proportions. Human / Caseinogen § 87.00 % 4.00 % 4.00 % 4.30 % 0.70 % 100.00 % Difference in proteins Difference in reaction Cow's \ Lactalbumin |. J Caseinogcn ^. I Lactalbumin |. Difference in J Human — small flocculi. curds \ Cow's — heavy curds. Human — amphoteric. Cow's — amphoteric, but more nearly acid. Testes. Vas deferens. Seminal vesicles. Ejaculatorj'' ducts. The scrotum. Spermatic cords. The penis. The urethra. The prostate gland. Cowper glands. Chap. XXI] SUMMARY 467 Testes Structure Location Function Two glandular organs which produce the spermatozoa. Testicle proper — ovoid body covered by fibrous tissue. Central portion consists of irregular cavities filled with seminiferous tubules and blood-vessels. Epididymis — tortuous tubule, forms long, narrow body which lies along posterior por- tion of testes. (In early foetal life in abdomen below kidneys. Before birth is normally drawn downward to scrotum, and is suspended by spermatic cord, f Production of spermatozoa. I Production of internal secretion. Vas Deferens — Continuation of epididymis, and serves to connect the epididymis and the seminal vesicle of each side. Two pouches located between bladder and rectum on outer side of each vas deferens. Connect vas deferens with ejaculatory duct. Function — Serve as reservoirs for semen, to wliich they add a secretion of their own. Formed by union of seminal vesicles and vas deferens of each side. Run downward, converge, pass between lobes of prostate gland and open into the floor of the prostatic portion of the urethra . Pouch wliich contains testes and part of each spermatic cord. Covered with thick dark skin. Dartos — reddish tunic under skin, consists of muscular and elastic tissue with numerous blood-vessels. Divided by septum into two halves. ' Consists of the vas deferens, arteries, veins, lymphatics, nerves, and layers of fascise connected by areolar tissue and serving as pedicle for testes. Extends from the internal abdominal ring to the back of the testes. ( Consists of three cylindrical J 1. Corpora cavernosa. I bodies of erectile tissue I 2. Corpus spongiosum. { Contains urethra wliich extends from bladder to the end of penis. Covered with skin and mucous membrane. ' Extends from the bladder through the corpus spongiosum to the end of the penis. Length 8 inches. ( Prostatic portion. Divisions < Membranous portion. I Penile or spongy portion. Consists f Mucous fining. of I Numerous muscular fibres. Seminal Vesicles Ejaculatory Ducts Scrotum Structure Spermatic Cords Penis Urethra 468 ANATOMY FOR NURSES [Chap. XXI The Pros- tate Cowper's Glands Puberty Semen Reproduc- tion Consists of tion Ovum Situated in front of the neck of the bladder and around the commencement of urethra. Shape — resembles chestnut. Fibrous capsule containing glandular and mus- cular tissue. Glandular tissue consists of tubules which empty into urethra. Function — Secretion of prostatic fluid. Located one on each side of membranous urethra into which they empty. About the size of a pea. Function — Secretion of a fluid wliich forms part of seminal fluid. Age at which sexual organs become matured and functional. Boy changes to a man. j Fluid derived from the various sexual glands in the male. I Spermatozoa are the main elements. Function — Produce another being. Impregna- f Union of spermatozoon and ovum. \ Occurs in Fallopian tubes. Globular cell fonned in ovaries, jls inch in diameter. Cell- wall = zona pellucida. CeU-body = cjiioplasm, serves as food. Cell nucleus = germinal vesicle, contains chromatin. . Nucleolus = germinal spot. A long, narrow cell formed in testes, ^Jo of an inch in length. ■ EUiptical head which contains nuclear material and chroma- Consists of { tin. Rod-shaped centre piece. Tail. Capable of independent motion in a fluid medium. Function to fertilize o^^im. Di\'ides into many cells surrounded by amnion and called embryo. Attaches itself to upper part of uterine ca\'ity in soft mucous mem- brane prepared for its reception. (Entoderm. Mesoderm. Ectoderm. Two weeks — size of a bean. Four weeks — size of a walnut. Four months — foetus — human characteristics are marked. Consists Sperma- tozoon Develop- ment of { Embryo ovum METRIC SYSTEM I 1 Inch 4 I 5 Centimetres The area of the figure within the heavy lines is that of a square decimetre. A cube, one of -whose sides is this area, is a cubic decimetre or litre. A litre of water at the temperature of 4° C. weighs a kilogramme. A litre is 2.11 pints or 33.81 ounces. A pint is 0.473 of a litre. (Liquid measure.) A litre is 1.76 pint. A pint is 0.568 litre. (Dry measure.) The smaller figures in dotted lines represent the areas of a square centimetre and of a square inch. A cubic centimetre of water at 4'^ C. weighs a gramme. 1 Metre = 39. .370432 inches. 1 Decimetre = 3.937043 inches. 1 Centimetre = .393704 inch. 1 Millimetre = .039370 inch. 1 Gramme 1 Decigramme 1 Centigramme 1 Milligramme 1 Dekagramme 1 Ilektogramme 1 Kilogramme 1 Kilogramme 1 Kilogramme 15.432 grains. 1.543 grains. .154 grain. .015 grain. 154.323 grains. 1543.235 grains. 15432.350 grains. 35.274 ounces. 2.204 pounds. Avoirdupois weights are used in weighing the organs of the body. One ounce avoirdupois = 28.35 grammes. 469 GLOSSARY Abdo'men. [From the Lat. abdo, to " conceal."] The largest cavity of the body, containing the liver, stomach, intestines, etc. ; the belly. Abdu'cens. [From the Lat. ab, " from," and duco, to " lead."] A term applied to the sixth pair of cranial nerves which supply the external recti (abductor), muscles of the eye. Abduc'tion. [From the Lat. ab, " from," and duco, to " lead."] Drawn away from the middle line of the body. Absorp'tion. [From the Lat. ab, " from," and sorbeo, to " suck up."] The process of taking up into the vascular system either digested food from the alimentary canal, or other substances from the various tissues. Acetab'ulum. [From the Lat. acetum, " vinegar."] A name given to the cup-shaped cavity in the os innominatum, resembling in shape an old-fashioned vinegar vessel. Acromeg'aly. [From the Gr. akron, an " extremity," and megas, " great."] A disease characterized by an overgrowth of the extremities and the face as well as the soft parts. Acro'mion. [From the Gr. akron, " summit," and omos, the " shoulder."] The triangular-shaped process at the summit of the scapula. Adduc'tion. [From the Lat. ad, " to," and duco, to " lead."] Brought to or nearer the middle line of the body. Ad'enoid. [From the Gr. aden, a " gland," and eidos, " form," or " re- semblance."] Pertaining to, or resembling a gland. Ad'ipose. [From the Lat. adeps, " fat."] Fatty. Adre'nal. [From the Lat. ad, "to," and ren, the "kidney."] Same as supra-renal. A small gland situated on the top of the kidneys. Afferent. [From the Lat. ad, " to," and Jero, to " bear," to " carry."] Bearing or carrying inwards, as from the periphery to the centre. Agminated. [From the Lat. agmen, a " multitude," a " group."] Ar- ranged in clusters, grouped together as the agminated glands of Peyer in the small intestine. Akine'sis. [From the Gr. a, "without," and kinesis, "motion."] Without motion. Fission or direct division of cells. 471 472 GLOSSARY Albu'mins. [From the Lat. albus, " white."] Thick, viscous substances containing nitrogen, that are soluble in water, dilute acids, dilute salines, and concentrated solutions of magnesium sulphate and so- dium chloride. They are coagulated by heat and strong acids. Ex- amples are : egg albumin and serum albumin of blood. Albuminu'ria. [A combination of the words " albumin " and " urine."] Presence of albumin in the urine. Alimentary. [From the Lat. alimentum, "food."] Pertaining to ali- ment, or food. Alve'oll. Plural of alveolus. [From the Lat. alveolus, a " little hollow."] Any little cell, pit, cavity, fossa, or socket. Socket of a tooth or an air-cell. Amoe'ba. [From the Gr. ameiho, to " change."] A single-celled organ- ism, which is constantly changing its form by protrusions and with- drawals of its substance. Amphiarthro'sis. [From the Gr. ampho, " both," and arthron, a " joint."] A mixed articulation ; one which allows slight motion. Amphoteric. [From the Gr. amphoteros, " both."] Partly acid and partly alkaUne in reaction ; having t;he power of turning red Utmus paper blue, and blue htmus paper red. Ampul'la. [From the Lat. ampulla, a " globular vessel."] The dilated part of a canal. Amylop'ins. [From the Gr. amylum, " starch," and opsis, " appear- ance."] An enzjone of the pancreatic juice that has the power to change starch into malt sugar, or maltose. Same as diastase. Anabol'ism. [From the Gr. anabole, a " thromng up."] The process by means of which simpler substances are built up into more complex substances. Anaesthe'sia. [From the Gr. a, an, " without," and aisthanomai, to " perceive," to " feel."] A condition of insensibihty. Anastomo'sis. [From the Gr. ana, " by," " tlirough," and stoma, a " mouth."] Conmiunication of branches of vessels with one another. An'nular. [From the Lat. aymulus, a " ring."] Ring-like, such as the Ugaments found at some of the joints. Aor'ta. [From aorte, to " carry."] The great artery that carries blood from the left ventricle of the heart. Apnoe'a. [From the Gr. a, " without," and pnwa, " breath."] Absence of breathing. Aponetiro'sis. [From the Gr. apo, "from," and neuron, a "sinew" or GLOSSARY 473 " tendon."] A flat wide band of fibrous tissue which is attached to a muscle. Arach'noid. [From the Gr. arachne, a " spider," a " spider's web," and eidos, " form," or " semblance."] Resembling a web. The middle of the three membranes of the brain and spinal cord. Arboriza'tions. A growth or an appearance resembhng the figure of a tree or plant. Are'olar. [From the Lat. areola, a " small space," dim. of area.] A term apphed to a connective tissue containing small spaces ; also to the colored area surrounding the nipple. Arrec'tor. [From the Lat. arrectus, " set up erect."] That which arrects. The arrector of the hair. Arte'rioles. [Arteriola, dim. of Lat. arteria, ^' artery."] A small artery. Arteriosclero'sis. [See artery below. Lat. scleroticus, from Gr. skleroo, to " harden."] Hardening of the arteries. Ar'tery. [From the Gr. aer, " air," and tereo, to " keep."] Literally, an air-keeper (it being formerly believed that the arteries contained air). A blood-vessel which carries blood from the heart. Arthro'dia. [From the Gr. arthron, a " joint."] A variety of movable joint. Articula'tion. [From the Lat. articulus, " a joint."] The more or less movable union of bones, etc. ; a joint. Asphyx'ia. [From the Gr. a, " without," and sphyxis, the " pulse."] Literally, without pulse. Condition caused by non-oxygenation of the blood. Assimila'tion. [From the Lat. ad, " to," and similis, " Uke."] The conversion of food into living tissue. At'las. The first cervical vertebra by which the head articulates with the spinal column, so called because it supports the head as Atlas was fabled to support the world on his shoulders. At'rophy. [From the Gr. a, " without," and trophe, " nourishment."] Wasting of a part from lack of nutrition. Aud'itory. [From the Lat. audio, auditum, to " hear."] Pertaining to the sense or organ of hearing. Augmenta'tion. The act of increasing or making larger. Aur'icle. [From the dim. of Lat. auris, the " ear."] A little ear, a term apphed to the ear-shaped cavities of the heart, also to the expanded portion of the external ear. Automat'ic. [From the Gr. automatos, "self -moving."] Not voluntary, not under the control of or affected by voUtion. 474 GLOSSARY Az'ygos. [From the Gr. a, " without," and zygos, a " yoke."] Without a fellow ; hence, unpaired, single. Bi'ceps. [From the Lat. bis, " twice," and caput, the " head."] A term apiilicd to muscles having a double origin or two heads. Bicus'pid. [From the Lat. bis, " twice," and cuspis, the " point of a spade."] Having two points or flaps. Blas'toderm. [From the Gr. blastos, a " bud," and derma, " skin."] The primitive membrane or layer of cells resulting from the subdivision of the germ. Brach'ial. [From the Lat. brachium, the " arm."] Belonging to the arm. Brachio-cephal'ic. [From the Lat. brachium, the " arm," and cephalicus, " of or pertaining to the head."] Of or pertaining both to the upper arm and the head ; as the brachio-cephalic (innominate) artery and veins. Bron'chi, pi. of Bronchus. [From the Gr. bronchos, the " wind pipe."] The two main branches of the trachea. Bron'chioles. A small bronchial tube. Buc'cal. [From the Lat. bucca, the " cheek."] Pertaining to the mouth or cheeks. Buc'cinator. [From the Lat. buccinare, " blow a trumpet."] The trum- peter's muscle. A thin, flat muscle that helps to form the wall of the cheek. Bur'sal. [From the Gr. bursa, a " bag."] Pertaining to bursce, mem- branous sacs. But'tock. The part at the back of the hip, which in man, forms one of the protuberances on which he sits. Butyr'ic Acid. [From the Lat. butyrum, " butter."] A colorless liquid having a strong rancid smell and acrid taste. C3H7COOH. Cae'cum. [From the Lat. ccecus, " bUnd."] The blind gut. Calca'neum. [From the Lat. calx, the " heel."] The bone of the heel. Cal'culi, pi. of Cal'culus. [From the Lat. calculus, " a pebble."] Stones. Caly'ces, pi. of Ca'lyx. [From the Gr. kalyx, a " cup."] Anatomists have given this name to small cup-Uke membranous canals, which surround the papillae of the kidney, and open into its pelvis. Canalic'ulus, pi. Canalic'uli. [Dim. of Lat. canalis, a " channel."] A small channel, or vessel. Can'cellated. [From the Lat. canccZ/MS, " lattice-work."] A term used to describe the spongy lattice-work texture of bone. GLOSSARY 475 Ca'nine. [From the Lat. canis, a " dog."] Name given to the third tooth on each side of the jaw; in the upper jaw it is also known as the eye-tooth, pointed hke the tusks of a dog. Can'thus. [From the Gr. kanthos, the " angle of the eye."] The angle formed by the junction of the eyelids, the internal being the greater, the external the lesser, canthus. Cap'illary. [From the Lat. capillus, " hair."] A minutely fine vessel, re- sembling a hair in size. Car'dio-inhib'itory. [From the Gr. kardia, " heart," and inhibere, to " restrain."] An agent which restrains the heart's action. Carot'ids. [Perhaps from the Gr. karos, " stupor," because pressing on them produces stupor.] The great arteries conveying blood to the head. Car'pus. [From the Gr. karpos, the " wrist."] The assemblage of bones forming the wrist. Car'tilage. [From the Lat. cartilago, " gristle."] A soUd but flexible ma- terial, forming a part of the joints, air-passages, nostrils, etc. Gristle. Ca'seinogen. [From the Lat. caseus, "cheese."] The curd separated from miUc by the addition of rennet, constituting the basis of cheese. Cataly'zer. [From the Gr. kata, " down," and luein, to " loose."] A sub- stance which hastens chemical reactions, but does not enter into the reactions. Enzymes are described as catalyzers. Caud'a Equi'na. [Lat. " Horse-tail."] A term applied to the termina- tion of the spinal cord, which gives off a large number of nerves which, when unravelled, resemble a horse's tail. Cau'date. [From the Lat. Cauda, a " tail."] Tail-like. Centrifugal. [From the Lat. centrum, the " centre," and fugere, " flee."] Flying off or proceeding from the centre. Centrip'etal. [From the Lat. centrum, the " centre," and petere, " seek, move toward."] Tending or moving toward the centre. Opposed to centrifugal. Cen'trosome. [From the Gr. kentron, " centre," and soma, the " body."] A pecuUar rounded body lying near the nucleus of the cell. It is regarded as the dynamic element by means of which the machinery of cell division is organized. Cerebel'lum. [Dim. of Lat. cerebrum, the " brain."] The hinder and lower part of the brain ; the little brain. Cer'ebrum. [Lat. the " brain."] Chief portion of brain. 476 GLOSSARY Ceru'minous. [From the Lat. cerumen, " ear-wax."] A term applied to the glands secreting cerumen, ear-wax. Cer'vix. [Lat.] The neck (httle used). Part of an organ Ukened to a neck. Choles'terin. [From the Gr. chole, " bile," and stear, " fat."] A taste- less, inodorous, fatty substance found in small quantities in the pro toplasm of all cells, especially in nerve tissue, blood corpuscles, and bile. Its origin and function are not known. Chon'drin. [From the Gr. chondros, " cartilage."] A kind of gelatine obtained by boihng cartilage. Chor'da Tym'pani. [Lat.] The tympanic cord, a branch of the facial, or seventh cranial, nerve which traverses the tympanic cavity and joins the gustatory, or lingual, nerve. Chor'dae Tendin'eae. [Lat.] Tendinous cords. Cho'roid. [From the Gr. chorion, " skin," and eidos, " form," or " re- semblance."] A skin-like membrane; the second coat of the eye. Chyle. [From the Gr. chidos, " juice."] Milky fluid of intestinal diges- tion, found in the lymphatics of the intestines. Chyme. [From the Gr. chumos, " juice."] Food that has undergone gastric but not intestinal digestion. (Both chyle and ch3Tne signify literally liquid, or juice.) Cica'trix. [Lat. a " scar."] The mark, or scar, left after the healing of a wound. Cil'ia. [Lat. the " eyelashes."] Hair-like processes of certain cells. Circumval'late. [From the Lat. circumvallo, to " surround with a wall."] Surrounded by a icall. Clav'icle. [From the. dim. of Lat. clavis, a " key."] The collar-bone, so named from its shape. Coagula'tion. [From the Lat. coag'ulo, to " curdle."] Applied to the process by which the blood clots or solidifies. Coalesce'. [From the Lat. con, " together," and alere, to " nourish."] To grow together. Coc'cyx. [Lat. the " cuckoo."] The lower curved bone of the spine, resembling a cuckoo's bill in shape. Coch'lea. [Lat. a " snail," a " snail-shell " ; hence, anything spiral.] A term appUed to a cavity of the internal ear. Coe'Uac. [From the Gr. koilos, " hollow."] Pertaining to the abdominal cavity. GLOSSARY 477 CoUat'erals. [From the Lat. con, " together," and lateralis, " of the side."] Situated at the side ; hence, also secondary. Co'lon. [Gr. kolon.] That portion of the large intestine which extends from the caecum to the rectum. Colum'nae Car'neae. [Lat.] " Fleshy columns " ; muscular projections in the ventricles of the heart. Com'missure. [From the Lat. con, " together," and njitto, missum, to " send."] A joining or uniting together. Something which joins together. Con'cave. [From the Lat. con, " together," and cavus, a " hollow."] The interior of a curved surface. Con'cha. [Lat. a " shell."] A term applied to the hollow portion of the external ear. Con'dyloid. [From the Gr. kondulos, a " knob," or " knuckle," and eidos, " hkeness."] A term applied to joints and processes of bone having flattened knobs or heads. Congen'ital. [From the Lat. con, " together," and gignere, to " beget."] Existing from birth. Conjuncti'va. [From the Lat. con, " together," and jungo, junctum, to " join."] A term appUed to the delicate mucous membrane which lines both eyeUds and covers the external portion of the eyeball. Contig'uous. [From the Lat. contiguus, akin to contingere, " to touch on all sides."] Adjacent; near; in actual contact. Convec'tion. [From the Lat. con, "together," and vehere, to " carry."] A process of transfer or transmission as of heat or electricity. The term " convection currents " is used in the text, and appUes to cur- rents of air produced by differences in temperature and density. Warm air expands, becomes less dense, and is forced upward by the cooler air, which is heavier and sinks down. In this way convection currents are established. Converge'. [From the Lat. con, " together," vergere, to " inchne."] To join at a point. Con'vex. [From the Lat. convexus, " vaulted."] The exterior of a curved surface. Convolu'tions. [From the Lat. con, and vol'vo, to " roU together."] The tortuous foldings of the external surface of the brain. Cor'acoid. [From the Gr. korakos, a " crow," and eidos, " form."] Pro- cess of the scapula, so named because it was thought to be the shape of a crow's beak. 478 GLOSSARY Co'rium. [Lat. the " skin."] The deep layer of the skin ; the derma. Cor'nea. [From the Lat. cormi, a " horn."] The transparent anterioi portion of the eyeball. Cor'onary. [From the Lat. corona, a " crown."] A term apphed to vessels, ligaments, and nerves which encircle parts like a crown, as the coronary arteries of the heart. Cor'pora Aran'tii. [From the Lat. corpus, the " body."] Fibro-cartilagi- nous nodules situated one in the centre of the free edge of each of the segments of the aortic and pulmonary valves. Named from Aranzi, an ItaUan anatomist. Cor'pus Callo'sum. [Lat.] " Callous body," or substance. A name given to the hard substance uniting the cerebral hemispheres. Cor'tex. [Lat. " bark."] External or surface layer of an organ, such as the kidney or brain. Cos'tal. [From the Lat. costa, a " rib."] Pertaining to the ribs. Cox'a, pi. Coxae. [From the Lat. coxa, " hip."] The hip bone, os coxae or OS innominatum. Crena'ted. [From the Lat. crena, a " notch."] Notched on the edge. Crib'riform. [From the Lat. cribrum, a " sieve," and forma, " form."] Perforated like a sieve. Cri'coid. [From the Gr. kri'kos, a " ring."] A cartilage of the larynx resembling a seal-ring in shape. Cru'ra Cer'ebri. [From the Lat. crxis (pi. crura), a " leg."] Legs, or pillars, of the cerebrum. Crypt. [From the Gr. knjpto, to " liide."] A secreting cainty ; a folUcle, or glandular cavity. Cune'iform. [From the Lat. cunetis, a " wedge," and forma, " shape."] Having the shape or form of a wedge. Name given to two carpal and six tarsal bones. Cu'ticle. [From the dim. of Lat. cutis, the " skin."] A term apphed to the upper, or epiclormal, layer of the skin. Cu'tis Ve'ra. [Lat.] The true skin; that underneath the epidermal layer. Cys'tic. [From the Gr. kustis, the " bladder."] Pertaining to a cyst, — a bladder or sac. Cy'toplasm. [From the Gr. kidos, a " cell," and plasso, to " form."] The name given by Kolliker to the contents of a cell; same as pro- toplasm. GLOSSARY 479 Decid'uous. [From the Lat. deciduus, " that falls down."] FaUing or liable to fall. Not permanent. Decussa'tion. [From the Lat. decusso, decussaium, to " cross."] To cross in the form of the letter X. Degluti'tion. [From the Lat. de, " down," and gliditio, " swallow."] The act or power of swallowing. Del'toid. Ha\ang a triangular shape ; resembling the Greek letter A(deUa) . Den'drite. [From the Gr. dendrites, " pertaining to a tree."] The name given to the branching processes of the neurone wliich begin to divide and subdivide as soon as they leave the nerve-cell. Denti'tion. [From the Lat. dentitio, " teetliing."] L The process of cutting teeth. 2. The time during wliich teeth are being cut. 3. The kind, number, and arrangement of teeth proper to any animal. Diabe'tes Mel'litus. [From the Gr. dia, " through," baino, to " go," and Lat. mel, " honey."] Excessive flow of sugar-containing urine. Diapede'sis. [From the Gr. dia, " through," and pedad, to " leap," to " go."] Passing of the red blood-corpuscles through vessel walls without rupture. Di'aphragm. [From the Gr. diaphrasso, to " divide in the middle by a partition."] The partition muscle dividing the cavity of the chest from that of the abdomen. Diarthro'sis. [From the Gr. dia, " through," as implying no impediment, and arthron, a " joint."] A freely movable articulation. Di'astase. [From the Gr. diastasis, " separate."] An enzyme of the saliva and pancreatic juice capable of decomposing carbohydrates. Dias'tole. [From the Gr. diastello, to " dilate."] The dilatation of the heart. Diath'esis. [From the Gr. dia, " through," and tithenai, to " place."] A congenital condition of the system which renders it peculiarly liable to some diseases. Dichot'omous. [From the Gr. dichotomos, " cutting in two."] Pertaining to or consisting of a pair or pairs. Divided into two. Diges'tion. [From the Lat. digestio, " arrangement."] The process of converting the food from the state in which it enters the mouth to that in which it can pass from the alimentary canal into the blood- vessels and lymphatics. Dip'loe. [From the Gr. diploo, to " double," to " fold."] The osseous tissue between the tables of the skull. 480 GLOSSARY Disac'charid. [From the Lat. (lis, " twice," and saccharon, " sugar."\ A complex sugar which on hydrolysis yields two molecules of a simple sugar. Disaccharid Glucose Fructose CnH^jOn + HoO^CeHnOe + CeHiA Dis'cus Prolig'erus, or germ disk. A term appUed to a mass of cells clinging to the ovum when it is set free from the ovary. More recent term is " ovarian mound." Disintegra'tion. [From the Lat. dis, " twice," and integer, " entire, wliolc."] A breaking apart. Distilla'tion. [From the Lat. distillatio, a " dripping down."] The act of distilling or of falling in drops. The operation of drixing off gas or vapor from volatile liquids or solids, by heat in a retort or still, and the condensation of the products as far as possible by a cool receiver. Dor'sal. [From the Lat. dorsum, the " back."] Pertaining to the back, or posterior part, of an organ. Duode'num. [From the Lat. duodeni, " twelve each."] First part of small intestines, so called because about twelve fingers' breadth in length. Du'ra Ma'ter. [Lat.] The " hard mother," called dura because of its great resistance, and mater because it is the guardian or protector of the brain. The outer membrane of the brain and spinal cord. Dyspnce'a. [From the Gr. dys, " difficult," and pneo, to " breathe."] Difficult breathing. Ec'toderm. [From the Gr. ektos, " outside," and denna, the " skin."] The completed outer layer of cells, or outer blastodermic membrane. Same as epiblast. Ectop'ic. [From the Gr. ek, " out of," and topos, " place."] Characterized by being out of place. Efferent. [From the Lat. ex, " out," and fero, to " carry."] Bearing or carrying outwards, as from the centre to the periphery. Elemen'tary. Pertaining to or of the nature of an element or elements. Elimina'tion. [From the Lat. e, "out of," and lirmn, liminis, a " thresh- old."] The act of expelling waste matters. EUminate signifies, literally, to throw out of doors. Em'bolus. [From the Gr. embolos, a wedge.] A portion of a blood clot which has been formed in one of the larger vessels, and has afterward been forced into one of the smaller vessels where it may act as a wedge. GLOSSARY 481 Em'bryo. The ovum and product of conception up to the fourth month, when it becomes known as the foetus. Emul'sion. [From the Lat. emulgere, to " milk."] A mixture of liquids, insoluble in one another, where one is suspended in the other in the form of minute globules, as the fat in milk. Enarthro'sis. [From the Gr. en, " in," and arthron, a " joint."] An articulation in which the head of one bone is received into the cavity of another, and can be moved in all directions. Endocar'dium. [From the Gr. endon, " within," and kardia, " heart."] Lining of the heart. . En'dolymph. [From the Gr. endon, " within," and Lat. lympha, " water."] The fluid in the membranous labyrinth of the ear. Endos'teum. [From the Gr. endon, " within," and osteon, a " bone."] The lining membrane of the medullary cavity of a bone ; the internal periosteum. Endothe'lium. [From the Gr. endon, " within," and thele, the " nipple."] A term appUed to single layers of flattened transparent cells, applied to each other at their edges and Uning certain surfaces and cavities of the body. In contradistinction to epithelium. En'siform. [From the Lat. ensis, a "sword," and forma, "form."] Shaped like a sword. En'toderm. [From the Gr. endon, " within," and derma, the " skin."] The completed inner layer of cells, or inner blastodermic membrane. Opposed to ectoderm. Same as hypoblast. En'zyme. [From the Gr. en, " in," and zume, " leaven."] A term applied to a class of ferments. Ep'iblast. [From the Gr. epi, " upon," and blastos, a " germ," or " sprout."] The external, or upper, layer of the germinal mem- brane. Epicra'nial. [From the Gr. epi, " upon," and kranion, "the cranium."] That which is upon the cranium or scalp. Epider'mis. [From the Gr. epi, " upon," and derma, the " skin."] The outer layer of the skin. Epigas'tric. [From the Gr. epi, " upon," and gaster, " stomach."] Lying upon, distributed over, or pertaining to the abdomen or the stomach. Epiglot'tis. [From the Gr. epi, " upon," and glottis, the " glottis."] The cartilage at the root of the tongue which forms a Ud or cover for the aperture of the larnyx. 2i 482 GLOSSARY Epimys'ium. [From the Gr. epi, " upon," and miis, " muscle."] The slicath of connective tissue surrounding an entire muscle. Epistro'pheus. [From the Gr. epi, " upon," and strephein, " turn."] The second cervical or odontoid vertebra; the axis; so called because the atlas turns upon it. Epithe'lial. [From the Gr. epi, " upon," and thele, the " nipple."] Per- taining to the epithelium, the cuticle covering the nipple, or any mucous membrane. The term epithelium is now appUed to the tissue composed of cells covering or hning all surfaces of the body. Eryth'rocyte. [From the Gr. eruthros, "red," and kutos, a "cell."] A fully developed red blood-corpuscle. Eth'moid. [From the Gr. ethmos, a " sieve," and eidos, " form," " re- semblance."] Sieve-like. A bone of the cranium, part of which is pierced by a number of holes. Evapora'tion. [From the Lat. e, " out," and vapor, " steam."] The act of resolving into vapor. In order to produce vapor, heat is necessary, and if not supphed, is taken from near objects. Thus the heat neces- sary for the evaporation of perspiration is taken from the body. Excre'tion. [From the Lat. excer'no, to " separate."] The separation from the blood of the waste particles of the body ; also the materials excreted. Expira'tion. [From the Lat. expi'ro, to " breathe out."] The act of forcing air out of the lungs. Fac'et. [From the Lat. fades, " face."] A small, flat, articular surface.] Fal'ciform. [From the Lat. falx, a " sickle," and forma, " shape." Sickle-shaped. Fallo'pian. A term apphed to tubes and hgaments first pointed out by the anatomist Fallopiics. Fascic'tilus, pi. Fasciculi. [Lat. a "bundle."] A bundle of close-set fibres. Fau'ces. [Lat., pi. of faux, fauds, the " throat."] The cavity at the back of the mouth from which the larynx and pharynx proceed. Fecunda'tion. [From the Lat. fecundatio, " impregnation."] The act of making fruitful or prolific. Impregnation. Fenes'tra. [Lat.] A window. Fermenta'tion. [From the Lat. fermentum, " ferment " ; perhaps from fervere, " to boil."] The process of undergoing an effervescent change as by the action of yeast. In physiology it refers to the GLOSSARY 483 transformation of an organic substance into new compounds by the action of a ferment. Fibril'la, pi Fibril'lae. [Dim. of Lat. fibra, a " fibre."] A little fibre. Fibrin'ogen. A protein in blood plasma, the main constituent of fibrin. Fi'brous. [From the Lat. fibra, " fibre."] Containing or consisting of fibres. Having the character of fibres. Fib'ula. [Lat. a " clasp."] The long sphnter bone of the leg. Fil'ifonn. [From the Lat. filum, a "thread," and forma, "form."] Thread-like. Fim'briae. [Lat. a " fringe."] A border, or fringe. Fis'sion. [From the Lat. findo, fissum, to " cleave."] A cleaving, or breaking up into two parts. Fo'cus. [From the Lat. focus, " hearth or fireplace."] A po^'nt at which the rays of light meet, after being reflected or refracted. Point at which an image is formed. Foe'tus. The child in utero from the fifth month of pregnancy till birth. Fol'licle. [From the dim. of Lat. follis, a " bag."] A little bag; a small gland. Fontanelle'. [Fr.] A httle fountain. A term appUed to the mem- branous spaces between the cranial bones in the new-born infant, in which the pulsation of the blood in the cranial arteries was im- agined to rise and fall like the water in a fountain. Fora'men, pi. Foram'ina. [Lat.] An opening, hole, or aperture. Fos'sa, pi. Fos'sae. [From the Lat. fodio, fossum, to " dig."] A depres- sion, or sinus ; literally, a ditch. Fo'vea Centralis. [Lat.] Central depression of the macula lutea. The point of most acute vision. Fun'giform. [From the Lat. fungus, a " mushroom," Sind forma, *' form."] Having the shape of a mushroom. Funic'ulus, pi. Funic'uli. [Dim. of Lat. funis, a " rope."] A little cord, or bundle, of aggregated fibres. Fu'siform. [From the Lat. fusiis, a " spindle," and forma, " form."] Spindle-shaped. Gang'lia, pi. of Gang'lion. [From the Gr. gagglion, a " knot."] A collection of nerve-cells in the course of a nerve that has the ap- pearance of a knot. Gas'tric. [From the Gr. gaster, the " stomach."] Pertaining to the stomach. 484 GLOSSARY Gastrocne'mius. [From the Gr. gaster, the " belly," and kneme, the " leg."] The belly-shstped muscle of the leg. Gas'tro-pul'monary. Same as gastro-pneumonic. [From the Gr. gaster, "stomach," and pnevmoji, a "lung": Lat. pulmo, a "lung."] Pertaining to the stomach and the lungs*: applied to the continuous mucous membrane of the respiratory and digestive tracts. Gen'erative. [From the Lat. generare, to " beget."] Pertaining to generation, or propagation. Connected with or resulting from the process of begetting. Genioglos'sus. [From the Gr. geneion, the " chin," and glossa, the " tongue."] A muscle connected with the chin and tongue. Gen'itals. [From the Lat. genitalis, " of or belonging to generation."] Pertaining to the organs of generation. Gesta'tion. [From the Lat. gestare, " carry, bear."] The act or condition of carrying young in the womb from conception to delivery. Preg- nancy. Ging'lymus. [From the Gr. gigglunios, a " hinge."] A hi7i^e-]omt. Gladiolus. [Dim. of Lat. gladiiis, a " sword."] The middle piece of the sternum. Glair'y. [From the Lat. clarws, " clear " ; Fr. clair.] Like the clear white part of an egg. Gland. [From the Lat. glans, an " acorn."] A secreting organ. An organ that abstracts certain materials from the blood and makes of them a new substance. Gle'noid. [From the Gr. glene, a " cavity," and eidos, " form," " resem- blance."] A name given to a shallow cavity. Glob'ulins. [From the Lat. globus, perhaps akin to glomus, " a ball."] Protein substances somewhat similar to the albumins, but differing in their solubility. Glomer'ulus. [Dim. of Lat. glojyius, a " ball."] A botanical term signi- fying a small, dense, roundish cluster : a term appUed to the ball- like tuft of vessels in cortical portion of the kidneys. Glos'sopharynge'al. [From the Gr. glossa, the " tongue," and pharygx, the " pharynx."] Belonging to the tongue and pharynx. Glot'tis. [Gr. the " mouthpiece of a flute."] The aperture oi the lar^mx. Glute'i, pi. of Glute'us. [From the Gr. gloutoi, the " buttocks."] The muscles forming the buttocks. Graafian Fol'licles, or Ves'icles. A term appUed to the sacs in the ovaries, which contain the ova or ceUs. GLOSSARY 485 Granula'tions. [From the Lat. granulum, diminutive of granum, " grain."] Grain-like, fleshy bodies that form on the surface of wounds and ulcers. Gus'tatory. [From the La,t. gusto, gustatum, to "taste."] Belonging to the sense of taste. Haemoglo'bin. [From the Gr. haima, " blood," and Lat. globus, a " globe," or " globule."] A compound protein found in the red corpuscles of the blood ; its molecules consist of a protein portion and of a pigment portion, the latter containing one atom of iron. Haemorrhoi'dal. [From the Gr. haima, " blood," and rhed, to " flow."] Pertaining to haemorrhoids, small tumors of the rectum, which frequently bleed. Haver'sian Canals. Canals in the bone, so called from their discoverer, Dr. Clopton Havers. Hemophil'ia. [From the Gr. haivia, " blood," and philein, " to love."] A congenital, morbid condition, characterized by a tendency to bleed immoderately from any insignificant wound, or even spontaneously. Hepat'ic. [From the Gr. hepar, the " liver."] Pertaining to the liver. Hi'lum, sometimes UTitten Hi'lus. [Lat.] It is the depression (usually on concave side) of a gland, where vessels, nerves, and ducts enter or leave. Histol'ogy. [From the Gr. histos, a " web, tissue," and logos, " word."] That branch of anatomy which is concerned with the structure, especially the microscopic structure, of the tissues of the body. Homoge'neous. [From the Gr. homos, " the same," and genos, " kind."] Of the same kind or quality throughout ; uniform in nature, — the reverse of heterogeneous. Hor'mone. [From the Gr. hormao, " to set in motion."] A chemical substance which is produced in one organ, and on being carried by the blood to another organ, stimulates this latter to functional activity. Hu'merus. [Lat. the " shoulder."] The arm-bone which concurs in forming the shoulder. Hy'aline. [From the Gr. hyalos, " glass."] Glass-like, resembhng glass in transparency. Hy'aloid. [From the Gr. hyalos, " glass," and eidos, " form."'] The name given the membrane which encloses the vitreous humor of the eye. It invests the vitreous humor except in front, where it is continuous with the suspensory ligament of the crystalUne lens. 486 GLOSSARY Hydrotherapy. [From the Gr. hudor, " water," and therapeuein, to " heal."] A mode of treating disease by the copious use of pure water, both internallj' and externally. Hy'oid. [From the Gr. letter upsilon, v, and eidos, " form," " resem- blance."] The bone at the root of the tongue, shaped Uke the Greek lett^'r upsilon, v. Hypermetro'pia. [From the Gr. hyper, " over," " beyond," metron, " measure," and dps, the " eye."] Far-sightedness. Hyperpnoe'a. [From the Gr. hyper, "over," and pneo, to "breathe."] Energetic or labored respiration. Hyper'trophy. [From the Gr. hyper, " over," and trophi, " nourish- ment."] Excessive growth ; thickening or enlargement of any part or organ. Hy'poblast. [From the Gr. hypo, " under," and blastos, a " sprout," or " germ."] The internal, or under, laj'er of the germinal membrane. Hypochon'driac. [From the Gr. hypo, " under," and chondros, a " carti- lage."] A term apphed to the region of the abdomen under the car- tilages of the false ribs. Hypogas'tric. [From the Gr. hypo, " under," and gaster, " stomach."] Situated below the stomach. Pertaining to the hjTDOgastrium. Hypoglos'sal. [From the Gr. hypo, " under," and glossa, the " tongue."] A name given to the motor nerve of the tongue. Hypoph'ysis. [From the Gr. hypo, "under," and phusis, a "growing."] Tlie pituitary body of the brain which is lodged in the central de- pression of the sphenoid bone. Il'eum. [From the Gr. eileo, to " twist."] The twisted portion of the small intestine. H'ium, pi. Il'ia. [From the Lat. ilium, the" flank."] The upper part of the OS innominatum. Inci'sor. [From the Lat. inci'so, to " cut."] Apphed to the front teeth of both jaws, which have sharp cutting edges. In'cus. [Lat.] An anx-il ; the name of one of the bones of the middle ear. Inflamma'tion. [From the Lat. inflammatio, a " setting on fire."] A morbid condition characterized by pain, heat, redness, sweUing, and usually loss of function. Infundib'ula. [Lat. pi. of infundibulum, a " funnel."] Funnel-sh&ped canals. GLOSSARY 487 Ingest'. [From the Lat. in, "in," and gerere, to " bear."] Taking food into the stomach. In'guinal. [From the Lat. inguen, the " groin."] Pertaining to the groin. Inhibi'tion. [From the Lat. inhibere, " restrain."] The lowering of the action of a nervous mechanism by nervous impulses reaching it from a connected mechanism. Innom'inate. [From the Lat. innominatus, " nameless."] A name given an artery, vein, and a bone. Inoc'ulate. [From the Lat. in, "in," and oculus, "bud."] The insertion of virus into a wound or abrasion for the purpose of communicating a disease. Inos'culate. [From the Lat. in, " into," and osculum, a " Uttle mouth."] To unite, to open into each other. In'sulate. [From the Lat. insula, an " island."] To isolate or separate from surroundings. Integ'ument. [From the Lat. in, and te'go, to " cover."] The skin, or outer covering of the body. Intercel'lular. Lying between cells. Intercos'tal. [From the Lat. inter, " between," and costa, " rib."] Situ- ated or intervening between successive ribs of the same side of the body. Interlob'ular. That which Ues between the lobules of any organ. Inter'stice. [From the Lat. inter, " between," and sto, or sisto, to "stand."] The space which stands between tilings ; spaces between parts. Intersti'tial. Pertaining to or containing interstices. Intes'tine. [From the Lat. in'tus, " within."] The part of the alimentary canal which is continuous with the lower end of the stomach ; also called the bowels. Intralob'ular. That which lies within the lobules of any organ. I'ris. [Lat. the " rainbow."] The colored membrane suspended behind the cornea of the eye. It receives its name from the variety of its colors. Is'chium. [From the Gr. ischio, to " support."] The lower portion of the OS innominatum ; that upon which the body is supported in a sitting posture. Jeju'num. [From the Lat. jejunum, " fasting," " empty."] The part of the small intestine comprised between the duodenum and ileum. It has been so called because it is almost always found empttj after death. 488 GLOSSARY Ju'gular. [From the L&t. jugulum, the "throat."] Pertaining to the throat. Katabol'ism. [From the Gr. katabole, " a throwing down."] Pertaining to katabolism, the process by means of which complex substances are rendered more simple and less complex. The opposite of anabolism. Karyokine'sis. [From the Gr. karuon, " a nut," and kinein "to move."] The indirect division of cells, in which prior to the division of the cell protoplasm complicated changes take place in the nucleus, at- tended with movement of the nuclear fil:)rils. Lac'rimal. [From the Lat. lacrima, " tear."] Of or pertaining to tears. Lacta'tion. [From the Lat. lac, ladis, " milk."] The period of gi\'ing 7mlk. Lactiferous. [From the Lat. lac, " milk," and ferre, " bear."] Bearing, or conveying, milk, as a lactiferous duct. Lacu'na, pi. Lacu'nse. [Lat. a " cavity," an " opening."] A httle hollow space. Lambdoi'dal. [From the Gr. letter A (Lambda), and eidos, " fonn," " rosemblanco."] ResembUng the Gr. letter A. Lamel'la, pi. Lamel'lae. [Lat.] A thin plate, or layer. Laryn'goscope. [From the Gr. laryg.v, the " larynx," and skopeo, to " look at."] The instrument bj' which the larynx may be examined in the living subject. Lar'ynx. The upper part of the air-passage, between the trachea and the base of the tongue. Latis'simus Dor'si. [Lat. superlative of latus, " broad," " wide," and dorsum, the "back."] The widest muscle of the back. Lens. [From the Lat. lem, " a lentil."] A transparent substance, ground ^^^th two opposite regular surfaces, either both curved, or one curved and one plane. There are two general classes of lenses : (1) concave, which are thinner at the centre than at the edges; and (2) convex, which are thicker at the centre than at the edges. (See page 43 L) Lip'ase. [From the Gr. lipos, " fat."] An enzyme of the pancreatic juice, capable of decomposing fats. Same as steapsin. Lob'ule. [From the dim. of Lat. lobus, a " lobe."] A stnall lobe. Lum'bar. [From the Lat. lumbaris, the " loin."] Pertaining to the loitis. GLOSSARY 489 Lymph. [From the Lat. hjmpha, " water."] A colorless fluid, resem- bling water in appearance. Lymph'ocyte. [From the Lat. lympha, "water, " and Gr. kutos, " a cell."] Name given to recently formed white blood-corpuscles that later become leucocytes. Lymph'oid. [From the Lat. lympha, " water," and Gr. eidos, " form," " resemblance."] Having resemblance to lymph. Mac'ula Lute'a. [Lat.] Yellow spot. Ma'lar. [From the Lat. jnala, the " cheek."] Pertaining to the cheek. Malle'olus, pi. Malle'oli. [Dim. of Lat. malleus, a "hammer."] A name given to the pointed projections formed by the bones of the leg at the ankle-joint. Malpigh'ian Bod'ies. [So called in honor of Malpighi, a celebrated Italian anatomist.] A term applied to small bodies, or corpuscles, found in the kidney and spleen. Mam'mary. [From the Lat. mamma, the " breast."] Of or pertain- ing to the breast. Man'dible. [From the Lat. mandere, " chew," " masticate."] The under jaw, or inferior maxillary, as distinguished from the upper jaw, or superior maxillary. Manu'brium. [Lat. a " haft," a " handle."] Name given to the upper portion of the sternum or breast bone. Mas'seter. [From the Gr. massaomai, to " chew."] One of the muscles of mastication. Mas'toid. [From the Gr. mastos, the " breast," and eidos, " form," " re- semblance."] Shaped like the breast. Ma'trix. [Lat.] The womb. Producing or containing substance. Matura'tion. [From the Lat. maturatio, a " hastening."] The process of bringing, or of coming to maturity. Medul'la Oblonga'ta. [Lat.] The " oblong marrow " ; that portion of the brain which lies within the skull, upon the basilar process of the occipital bone. Meibo'mian. A term appUed to the small glands between the conjunctiva and tarsal cartilages, discovered by Meibomitis. ISIore recent term is tarsal glands. Mem'brane. [From the Gr. membrane, " parchment."] An enveloping or a liriing tissue of the body. 490 GLOSSARY Menin'ges. [The pi. of Gr. vienigx, " membrane."] Term ap- plied to the three membranes that invest the brain and spinal cord. Mes'entery. [From the Gr. mesos, " middle," and enteron, the " in- testine."] A duplicature of the peritoneum covering the small intestine, which occujiies the middle, or centre, of the abdominal cavity. Mes'oblast. [From the Gr. mesos, " middle," and blastos, a " germ " or " sprout."] The middle layer of the germinal membrane. Mesoco'lon. A dupUcature of the peritoneum covering the colon. Mes'oderm. [From the Gr. mesos, " middle," and derma, the " skin." The middle germinal layer of cells lying between the ectoderm and entoderm. Same as mesoblast. Metab'olism. [From the Gr. metabole, " change."] The changes taking place in cells, whereby they become more complex and contain more force, or less complex and contain less force. The former is construc- tive metabolism, or anaboUsm; the latter, destructive metabolism, or kataboUsm. Metacar'pus. [From the Gr. m£ta, " after," or " beyond," and karpos, the " wrist."] The part of the hand comprised between the ivrist and fingers. Metatar'sus. [From the Gr. meta, " after," or " beyond," and tarsos, the " instep."] That part of the foot comprised between the instep and toes. Mi'tral. ResembUng a mitre. Mo'lar. [From the Lat. mola, a " mill."] A term applied to the teeth, wliich bruise, or grind, the food. Monosaccharid. [From the Gr. monos, " one, single," and sakcharis, " sugar."] A simple sugar. CeHnOs- Mo'tor Oc'uli. [Lat.] Mover of the eye. Mu'cin, the chief constituent of mucus. Mus'cle. [From the Gr. mus, " muscle."] A kind of animal tissue con- sisting of bundles of fibres whose essential physiological characteris- tic is contractiUty. Myocar'dium. [From the Gr. mus, mnos, a " muscle," and kardia, the " heart."] The muscidar structure of the heart. Myo'pia. [From the Gr. 7nu6, to " contract," and dps, the " eye."] Nearsightedness. My'osin. Cliief protein substance of muscle. GLOSSARY 491 Na'ris, pi. Na'res. [Lat.] A nostril. Neurax'oi^. [From the Gr. neuron, " nerve," and axon.] An axis cylinder process. Neurilem'ma. [From the Gr. neuron, a " nerve," and lemma, a " coat," or " covering."] Nerve-sheath. Neu'rone. [From the Gr. neuron, a " nerve."] The nerve-cell, inclusive of all its processes. Node. [From the Lat. norfi/s, a " knot."] A knot, or what resembles one. A lymphatic ganghon. Nucle'olus, pi. Nucle'oli. [Dim. of Lat. nucleus, a "kernel."] A smaller nucleus within the nucleus. Nu'cleus, pi. Nu'clei. [Lat. a " kernel."] A minute vesicle embedded in the cell protoplasm (cytoplasm). Nutri'tion. [From the Lat. nu'trio, to " nourish."] The processes by which the nourishment of the body is accompUshed. Occip'ital. [From the Lat. occiput, occipitis, the " back of the head."] Pertaining to the occiput, the back part of the head. Odon'toid. [From the Gr. odous, odontos, a " tooth," and eidos, " form," " resemblance."] Tooth-like. (Ede'ma. [From the Gr. aided, to " swell."] A swelling from effusion of serous fluid into the areolar tissue. (Esoph'agus. [Gr. oisophagos, from oiso (fut. of oio) to " carry," and phagein, " to eat."] The gullet. Olec'ranon. [From the Gr. 6le7ie, the " elbow," and kranion, the " head." The head of the elbow. Olfac'tory. [From the Lat. olfacio, olfactum, to " smell."] Belonging to the sense of smell. Omen'tum. [Lat. " coverlet."] A dupUcature of the peritoneum, which hangs in front of the intestines. Ophthal'mic. [From the Gr. ophthalmos, the " eye."] Belonging to the eye. ^ Op'sonins. [From the Gr. opsono, " prepare food for."] A name given to chemical substances found in blood plasma which make microbes more susceptible to phagocytes. Op'tic. [From the Gr. opsis, " sight."] That which relates to sight. Orbicula'ris. [From dim. of Lat. orbis, an " orb," or " circle."] Name of the circular muscles. Or'bital. [From the Lat. orbita, a " track," " rut of a wheel."] Pertain- ing to the orbit, the bony ca\'ity in which the eyeball is suspended. 492 GLOSSARY Or'gan. [From the Gr. organon, an " instmment, implement, tool.") Any part of the body with a special function. O'rifice. [From the Lat. os, oris, a "mouth," and facere, "to make."] An opening. Os, pi. Ora. [Lat.] A mouth. Os, J)!. Ossa. [Lat.] A bone. Os Cox'ae. The hip bone, or os innominatum. Oscilla'tion. [From the Lat. oscillare, "to swing."] Swinging backward and forward; vibration. Os'sa Innomina'ta, pi. of Os Innomina'tum. [Lat.] " Unnamed bones." The irregular bones of the pelvis, unnamed on account of their non- resemblance to any known object. Os'seous. [From the Lat. os, a " bone."] Consisting of or resembling bone. Os'sicle. [From the Lat. ossicvlum, dim. of os, a " bone."] A small bone. Os'teoblasts. [From the Gr. osteon, a " bone," and blastos, a " germ," or " sprout."] The germinal cells deposited in the development of bone. O'toliths. [From the Gr. om.s, otos, the " ear," and lithos, a " stone."] Particles of calcium carbonate and phosphate found in the internal ear. O'vum. pi. O'va. [Lat. an " egg."] The human germ-cell. Pal'ate. [From the Lat. pala'tum, the " palate."] The roof of the mouth, consisting of the hard and soft palate. Pal'pebra, pi. Pal'pebrae. [Lat.] The eyehd. Pan'creas. [From the Gr. pan, " all," and kreas, " flesh."] A compound secreting gland ; one of the accessory organs of nutrition. The sweetbread of animals. Papil'lae. [Lat. pi. of papilla, a " nipple," a " pimple."] Minute emi- nences on various surfaces of the body. Pari'etal. [From the Lat. paries, parietis, a " wall."] Pertaining to a wall. Parot'id. [From the Gr. para, " near," and om, otos, the " ear."] The large salivary gland near the ear. Parturi'tion. [From the Lat. parturio, parturitum, to " bring forth."] The act of bringing forth, of giving birth to young. Patel'la. [Lat " a httle dish."] A small, 6ou7-shaped bone ; the knee- pan. GLOSSARY 493 Pec'toral. [From the Lat. pectus, pectoris, the " breast."] Pertaining to the breast, or chest. Ped'icle. [From the dim. of Lat. pes, pedis, a " foot."] A stalk. Pedun'cle. [From the Lat. pedunculus, dim. of pes, a " stalk," a " foot."] A narrow part acting as a support. Pel'vic. [From the Lat. pelvis, a " basin."] Pertaining to the pelvis, the basiii, or bony cavity, forming the lower part of the ab- domen. Pep'sin. [From the Gr. pepto, to " digest."] A ferment found in gastric juice, having power to convert proteins into peptones. Pep'tone. [From the Gr. pepto, to " digest."] A term applied to protein material digested by the action of the digestive juices. Pericar'dium. [From the Gr. peri, " about," " around," and kardia, the "heart."] The serous membrane covering the heart. Perichon'drium. [From the Gr. peri, " about," " around," and chondros, a " cartilage."] The serous membrane covering the cartilages. Per'ilymph. [From the Gr. peri, " about," " around," and the Lat. lympha, " water."] The fluid in the osseous, and surrounding the membranous labyrinth of the ear. Perimys'ium. [From the Gr. peri, " around," and mus, " muscle."] The connective tissue septa connecting and enveloping the separate fas- ciculi of a muscle. Perine'um. [From the Gr. perinaion.] The region of the body between the thighs, extending from the anus to the fourchette in the female, or to the scrotum in the male. Perios'teum. [From the Gr. peri, " about," " around," and osteon, a " bone."] The membrane covering the bones. Periph'eral. [From the Gr. peri, " about," " around," and phero, to " bear."] Pertaining to the periphery, or circumjerence; that which is away from the centre and towards the circumference. Peristal'sis. [From the Gr. peristello, to " compress."] Peristaltic ac- tion. A term appUed to the worm-like movement of the intestines by which its contents are propelled downward. Peritone'um. [From the Gr. periteino, to " stretch around," to " stretch all over."] The serous membrane lining the walls and covering the contents of the abdomen. Permeable. [From the Lat. per, " through " and meare, " to pass."] Capable of being passed through; substances which allow the pas- sage of fluids. 494 GLOSSARY Perone'al. [From the Gr. perone, the " fibula."] Pertaining to the fibula; a term applied to muscles, or vessels, in relation to the fibula. Pe'trous. [From the Gr. petra, a " rock."] Having the hardness of rock. Phag'ocytes. [From the Gr. phagein, " eat," and kutos, a " cell." A Ij'^mph-corpuscle, or white blood-corpuscle, regarded as an organism capable of devouring what it meets, especially pathogenic microbes. Phalan'ges. [Lat. pi. of phalanx, a " closely serried array of soldiers."] A name given to the small bones forming the fingers and toes, be- cause placed alongside one another hke a phalanx. Phar'ynx. [From the Gr. pharugx, the " throat."] The cavity forming the upper part of the gullet. Phonation. [From the Gr. phone, the " voice."] Utterance of vocal sounds. Phren'ic. [From the Gr. phren, the " diaphragm."] Pertaining to the diaphragm. Pi'a Ma'ter. [From the Lat. pia (fem.), " tender," " delicate," and mater, " mother."] The most internal of the three membranes of the brain. Pig'ment. [From the Lat. pigmentum, " paint," " color."] Coloring matter. Pin'na. [Lat. a " feather," or " wing."] External cartilaginous flap of the ear. Same as auricle. Pi'siform. [From the Lat. pismn, a " pea," and forma, " form."] Having the form of a pea. One of the carpal bones. Pitu'itary. [From the Lat. pituita " phlegm."] Secreting or containing ■ mucus, or supposed to do so. (It was formerly supposed that the secretions of the nose proceeded from the brain.) Placen'ta. [From the Gr. plakous, a "cake."] A flat, circular, vascular substance which forms the organ of nutrition and excretion for the fa?tus in utero. Plan'tar. [From the Lat. planta, " the sole of the foot."] Pertaining to the sole of the fooc. Platys'ma. [From the Gr. plains, " broad."] A thin, broad muscle situated immediately beneath the skin at the side of the neck, and extending from the chest and shoulder to the face. Plex'us. [From the Lat. plecto, plexum, to " knit," or " weave."] A net- work of nerves or veins. Pneumogas'tric. [From the Gr. pneumon, a " lung," and gaster, the " stomach."] Pertaining to the lungs and stomach. GLOSSARY 495 Polyhe'dral. [From the Gr. -polys, " many," and hedra, a " side."] Many-sided. Polysaccharid. From the Gr. polys, "many," and Lat. saccharum, "sugar."] A complex sugar, which when decomposed gives many molecules of a simple sugar. Poplite'al. [From the Lat. poples, poplitis, the " ham," the " back part of the knee."] The space behind the knee-joint is called the popliteal space. Premo'lar. [From the Lat. proe, " before," and molaris, " molar."] An- terior in position to a molar ; as premolar tooth. Prismat'ic. Resembhng a prism, which, in optics, is a sohd, triangular- shaped glass body. Prona'tion. [From the Lat. pronus, " incUned forwards."] The turning of the hand with the palm downward. Prona'tor. The group of muscles which turn the hand palm down- ward. Pro'toplasm. [From the Gr. protos, " first," and plasso, to " form."] X first -formed, organized substance; primitive organic cell matter. Pso'as Mag'nus. [From the Gr. psoa, " loin," and Lat. magnus, " great."] A muscle of the loins and pelvis. The tenderloin. Psy'chical. [From the Gr. psyche, the " soul."] Pertaining to the mind. Pter'ygoid. [From the Gr. pterux, a " wing," and eidos, " form," " re- semblance."] Wing-Uke. Pty'alin. [From the Gr. ptyalon, " saliva."] A ferment principle in saliva, having power to convert starch into sugar. Pu'berty. [From the Lat. pvher, " adult."] The age at which re- production becomes possible; sexual maturity in the human race. Pu'bes, gen. Pu'bis. [Lat.] The hairy region above the genitals, also used for os pubis, the portion of the os innominatum forming the front of the pelvis. Pul'monary. [From the Lat. pulmo, pi. pulmones, the " lungs."] Re- lating to the lungs. Pulse. [From the- Lat. pello, pulsum, to " beat."] The striking of an artery against the finger, occasioned by the contraction of the heart ; commonly felt at the wrist. Pylo'rus. [From the Gr. pvlouros, a " gate keeper."] The lower orifice of the stomach, furnished Avith a circular valve which closes during stomach digestion. 496 GLOSSARY Pyrex'ia. [From the Gr. pyresso, (fut.) pyrexo, to " have a fever."] Ele- vation of temperature ; fever. Quad'rate. [From the Lat. quadratus, '' make four-cornered, or square."] Siiuare. (A small lobe of the liver.) Quad'riceps. [From the Lat. quatuor, " four," and caput, the " head."] A term applied to the extensor muscle of the leg, having four heads, or parts. Rac'emose. [From the Lat. racemus, a "bunch of grapes."] Temi appUed to compound, saccular glands, from their supposed resemblance to a bunch of grapes. Radia'tion. [From the Lat. radiare, to " furnish with spokes or wheels."] The (hffusion of rays of hght. Ra'dius. [Lat. a " rod," the " spoke of a wheel."] The outer bone of the forearm, so called from its shape. Rile. [From the Fr. raler, to " rattle in the throat."] A rattling, bub- bhng sound attending the circulation of air in the lungs. Different from the murmur produced in health. Rec'tus. pi. Rec'ti. [Lat.] Straight. Reflec'tion. [From the Lat. re + flectere, to "bend or turn."] The return of rays, beams, sound, or the like from a surface. Reflection of light is of two kinds, regular and diffused. When a beam of light enters a darkened room through a small opening and strikes a mirror, a reflected beam will be seen travelling along some definite path. This is called regular reflection. Should the light, however, fall on a piece of white paper, it would be reflected and scattered in all direc- tions. Tliis is called diffused reflection and is caused by the inequali- ties of the reflecting surface. All rough surfaces, as well as dust and moisture in the atmosphere, serve to diffuse light. If this were not the case, it would be dark everj'where except in the direct path of light from some luminous body. Refrac'tion. [From the Lat. re -\- frangere, to "break."] The bending or deviation in tlic course of rays of hght in passing obliquely from one transparent medium into another of different densitj'. Light waves travel with different velocities in mediums of different dei>- sities, the more dense the medium, the less the velocity. For instance, light will travel less rapidly in water than in air. For this reason where a ray of light in air strikes a body of wat«r obliquely, it will be bent out of a straight hne, as shown in the GLOSSARY 497 following diagram; the light ray AC, instead of following the straight line AB, is bent on striking the surface of the dense medium, thereby being bent from its direct path toward C. Re'nal. [From the Lat. ren, rents , the " kidney . " ] Per- taining to the kidneys. Ren'nin. [Rennet.] The milk- curdUng enzyme which constitutes the active prin- ciple of rennet. Resil'iency. [From the Lat. re, " back," and silere, to " leap."] The act of resil- ing, leaping, or springing back ; the act of rebound- ing. Respira'tion. [From the Lat. res'piro, to " breathe frequently, comprising two acts, or breathing out. Res'tiform. [From the Lat. Testis, a " cord, rope," and/orwa, " form."] In anatomy denoting a part of the medulla oblongata, called the restifonn bodj'. Retic'ular. [From the Lat. reticulum, a " small net."] Resembling a small net. Ret'iform. [From the Lat. rete, a " net," and forma, " form."] Having the form, or structure, of a net. Ret'ina. [From the Lat, rete, a " net."] The most internal membrane of the eye ; the expansion of the optic nerve. Ru'gae. [Lat. pi. of ruga, a " wrinkle."] A term applied to the folds, or wrinkles, in the mucous membrane, especially of the stomach and vagina. The function of breathing, inspiration, or breathing in, and expiration, Sa'crum. [Lat. neut. of sacer, " sacred."] The large triangular bone above the coccyx, so named because it was supposed to protect the orgarxs contained in the pehas, which were offered in sacrifice and considered sacred. 2k 498 GLOSSARY Sag'ittal. [From the Lat. sagitta, an " arrow."] Arrow-like. Saliva'tion. [From the Lat. scdivare, to " salivate."] An excessive secretion of saliva. SapiToid, 315. parotid, 257. prostate, 468. salivary, 257. sebaceous, 349, 360. secreting, 135. simple, 135. sublingual, 257. Glands — continued submaxillary, 257. summary of, 139. suprarenal, 316. sweat, 350, 360. tarsal, 422. thynuis, 315. thyroid, 313. urethral, 451. vulvo-vaginal, 451. Glenoid cavity, 71. fossa, 57. Glisson's capsule, 278. Globulins, 148. Glomerulus, 327. Glossopharyngeal nerve, 397. Glottis, 236. Glucose, in urine, 336. Gluten, as food, 287. Gluteus maximus, 115. medius, 115. minimus, 115. Glycogenic function of liver, 278. Glycosuria, 336. Goitre, 315. exophthalmic, 315. "Goose flesh," 348. Graafian follicles, 443, 463. Green-stick fracture, 42. Gristle, 40 ; and see Cartilage. Gullet, 261, 281. Haemoglobin, 143. Hairs, 347, 360. Hamstring muscles, 1 16. Hand, body of, 74. bones of, 74. Haversian, canal, 44, 48. system, 44, 48. Head, 52. bones of, 53. muscles of, 95. of bone, 52. Hearing, 414. 420, 434. Heart, 161, 180. auricle, 164. -beat, 216, 228. cause of, 216. blood supply of, 168, 181. cavities of, 164, 180. chordae tendineae, 166. murmurs, 216. muscle fibres of, 162. nerve supply of, 168, 181, 217. orifices of, 165, 180. papillary muscles, 166. sounds of, 216, 228. causes of, 228. summary, 180. valves of, 166, 181, 218. bicuspid, J 66, 181. function of, 167, 168. influence of.^n circulation, 218. INDEX 513 Heaxt — continued mitral, 166, 181. semilunar, 167, 181. tricuspid, 166, 181. ventricles, 164. Heat, bodily, 352. centres for, 355. distribution of, 353. loss of, 353, 361. production of, 352. regulation of, 354, 355, 361. variation in, 357. where produced, 352, 361. Heel bone, 80. Hemophilia, 150, 159. Hemorrhage, regeneration of blood after, 152, 159. Hemorrhoidal artery, superior, 195. Hepatic, artery, 277. cells, 276. duet, 277. flexure, 270. vein, 277. Hernia, 109. Hiccough, 249. Highnaore, antrum of, 63. Hip, bones of, 74. Hippuric acid, 336. Hormones, 137. Humerus, 71. Humor, aqueous, 429, 440. vitreous, 430, 440. Hunger, 409, 433. Hyaline cartUage, 40. Hyaloid membrane, 430. Hydrate, 8. Hydration, 8. Hydrochloric acid in gastric juice, 295. Hydrolysis, 8, 29C. Hymen, 451. imperforate, 451. Hyoid bone, 63. Hypermetropia, 431, 441. Hyperpncca, 247. Hypochondriac regions of abdomen, 262. Hypogastric, artery, 197. region of abdomen, 262. Hypoglossal nerve, 397. Hypophysis, 316, 322. Iced food or drinks injurious, 292. Ileo-csecal valve, 270. Ileum, 266. Iliac, arteries, 197, 198, 212. regions of abdomen, 262. veins, 207, 213. Iliopectineal line, 76. Ilium, 75. Images, inversion of, 432. Immune bodies, in blood, 149, 158. Impregnation, 460, 468. site of, 461. 2l Incisor teeth, 259. Incus, 416. Indican, in urine, 337. Inferior maxillary nerve, 396. turbinated bones, 60. Inflanimation, circulatory changes in, 145, 157. Infundibulum of lungs, 240. Infusion, intravenous, 152, 160. Inguinal canal, 109. ligament, 107. regions of abdomen, 262. Inhibition, 366. Inhibitory nerve fibres, 372, 403. Innominate artery, 190. vein, 205, 212. Inorganic compounds, 5. Inosculation of arteries, 185. Insalivation, 291. Inspiration, 242, 252. Intercellular substance, 25. Intercentral neurones and relays, 375. Intercostal arteries, 193. muscles, 105. Interepithelial arborizations, 369. Interlobular veins, 276. Internal, 17. oblique muscle of abdomen, 107. secretions, 313. in blood, 149, 158. Intervertebral disks, 66. Intestinal digestion, 305. glands, 237. juice, 298. Intestine, discharge of waste matters from, 325. large, 270 ; and see Large intestine. small, 265 ; and see Small intestine. thick, 270 ; and see Large intestine. thin, 265 ; and see Small intestine. Intralobular veins, 277. Intravenous infusion, 152, 160. Inversion of images, 432. Iris, 426, 440. Irritability, 91. Ischium, 75. Island of Reil, 391. Islands of Langerhans, 273. Jejunum, 266. Joints, 82. ball-and-socket, 86. classification of, 82. condyloid, 86. freely movable, 85. gliding, 85. hinge, 86. immovable, 82. movements of, 87. pivot, 86. reciprocal reception, 88. saddle, 86. shghtly movable, 84. 514 INDEX Joints — continued summary of, 87. sutures, 82. Jugular veins, 201, 212. Karj-okinesis, 24. Katabolism, 23. Kidneys, 326, 339. blood supply of, 327, 339. calyces, 339. capsule, 326, 327. function of, 330, 340. glomerulus, 327, 329. Malpighian corpuscles, 327, 339. matters eliminated by, 325. nerves of, 329^ 340. papilltB, 327. pelvis, 326. pyramids, 327. structure, 325, 328. supports, 326. uriniferous tubules, 327, 339. Kinetic theory, 10. Knee-cap, 77. Labia majora, 450. minora, 450. Labyrinth, 417, 436. bony, 417, 436. membranous, 417, 436. Lacrimal apparatus, 422, 438. bones, 61. gland, 422. sac, 423. Lacteals, 175, 176, 182. Lactose, 456. Lacunx' of bone, 44. Laraclhe of bone, 43. Langerhans, islands of, 273. Language, basis of, 394. Large intestine, 270, 282. action of bacteria in, 300. changes undergone by food in, 299. coats of, 271. divisions of, 270. functions of, 271. movements of, 299. secretion of, 299. Larj'nx, 250. Lateral, 17. Latissimus dorsi, 103. Laughing, 249. Leg, bones of, 74. Legumin, 287. Leucocytes, i44. Leucocytosis, 144. Leucopenia, 144. Levatores costarum, 105. Levator palpebrse superioris, 99, 422. Lieberkiihn, crypts or follicles of, 267. Ligamenta flava, 37, 67. Ligaments, 37. annular, 118. Ligaments — continued inguinal, 107. of uterus, 447, 465. Ligamentum nuchae, 102. Light, perception of, 429. rays of, in hypermetropic eye, 431, 432, in myopic eye, 431, 432. in normal eye, 431, 432. Limbs, 20. Linea alba, 108. Lipase, 295, 297. Liver, 273, 283. discharge of waste matters by, 325. fissures, 274. functions of, 278. ligaments, 273. lobes, 275. loVmles of, 275. lymphatics, 278. minute anatomy, 275. nerves, 278. vessels, 295. Localization of brain function, 393. Lower extremities, bones of, 74. muscles of, 112, 125. Lower jawbone, 63. Lumbar arteries, 197. fascia, 107. regions of abdomen, 262. Lungs, 230, 251. anatomy of, 240. blood-vessels of, 240. capacity of, 245, 253. infundibulum of, 240. lobule of, 241. matters eliminated by, 325. nerves of, 240. Lymph, 141, 153, 160, 223, 230. differences between blood and, 153. flow of, 223, 230. formation of, 223, 230. function, 153, 160. interchange between blood and, 154. sources of, 153, 160. Lymphatic duct, right, 174, 182. part drained by, 173, 175. Lymphatics, 172, 174, 182. classification of, 175. function of, 176. Lymphatic vessels, 172, 174, 182; and see Lymphatics. Lymph nodes, 172, 176, 182, 183. function of, 178, 183. location of, 178, 183. Lymph nodules, aggregated, of Peyer, 269. solitary, 269. Lymphocytes, 144. Lymphoid tissue, 40. Lymph spaces, 172, 174, 182. Macula lutea, 429. Malar bone, 61. INDEX 515 Malleolus, external, 78. inner, 78. lateral, 78. medial, 78. Malleus, 416. Malpighian corpuscles, of kidney, 327, 339. of spleen, 318. Malpighian layer of skin, 344, 359. Mammary glands, 453, 465. Mandible, 63. Manubrium, 68. Marrow of bone, 44, 48. Mastication, 291. muscles of, 99, 121. Mastoid, cells, 56, 416. process, 56. Matter, changes in, 4. definition of, 3. forms of, 3. Maxilla, 62. Maxillary bones, 62, 63. Measurements, table of, 25. Meatus, external auditory, 414. of bone, 52. Medial, 17. Median line, 17. Mediastinal arteries, 193. Mediastinum, 242, 252. Medulla oblongata, 385, 406. centres in, 386. functions of, 385, 406. Medullary canal of bone, 50. sheath, 367. MeduUated nerve-fibres, 367. Meibomian glands, 422. Meissner's corpuscles, 410. Membrana tympani, 416, 435. Membrane, or membranes, 37, 127. basement, 127. classification of, 127. cutaneous, 134. hyaloid, 430. mucous, 130 ; and see Mucous mem- brane. pituitary, 234. Schneiderian, 234. serous, 127 ; and see Serous membranes. summary of, 137. synovial, 129 ; and see Synovial mem- branes. Meninges of brain, 384. of spinal cord, 378. Menopause, 452. Menstruation, 452, 465. and ovulation, 453, 465. changes in connection with, 452. purpose of, 453. Mesenteric artery, inferior, 195. superior, 194. Mesentery, 255. Mesoderm, 27, 33. Metabolic changes, 307. factors promoting, 308. Metabolism, 23, 307, 319. changes occurring in, 307, 308. factors promoting, 308. functions of, 308. of carbohydrates, 309, 320. of fats, 308, 320. of proteins, 310, 320. Metacarpus, bones of, 74. Metatarsus, 80. Micturition, 332, 341. involuntary, 333. Milk, composition of, 456, 466. human and cow's, 456. secretion of, 455, 456, 466. Milk sugar, 456. Mineral matter as food, 302. Mixtures, 4. Modiolus, 419. Molar teeth, 260. Molecule, 3, 6. Moleschott's diet, 312. Monosaccharids, 288. Monro, foramen of, 392. Mons Veneris, 449. Motor areas of brain, 393, 407. nerve fibres, 371, 372, 403. plates, 370. tracts of spinal cord, 380. Motor-oculi nerve, 396. Mouth, 234, 255, 279 ; and see Buccal cavity. changes undergone by food in, 291, 304. digestion in, 291. Mucous membranes, 130. function of, 133. gastro-pulmonary, 130. genito-urinary, 131. structure of, 131. summary of, 138. Mucus, 140. Muscle, or muscles, 89. adductors of thigh, 115. arrector, of hairs, 348. attachment of, to skeleton, 94. automaticity of, 93. biceps, of arm. 111. of leg, 115. blood vessels of, 92. buccinator, 100. cardiac, 91, 162. characteristics of, 91. classification of, 89, 119. contractility of, 91, 93, 120. contractor of pupQ, 426. deltoid, 110. diaphragm, 105. dilator of pupil, 427. elasticity of, 92. extensibility of, 92. extensors of forearm, 112. external oblique, of abdomen, 107. fatigue of, 94. olG INDEX Muscle, or muscles — continued fibres, 90. of heart, 1G2. flexors of forearm, 112. gastrocnemius, 118. genioglossus, 101. glutei, 114. gluteus, maximus, 115. medius, 115. minimus, 115. gracilis, 115. hamstring, 116. iliacus, 114. inferior oblique, of eyeball, 98. insertion of, 95. intercostals, 105. internal oblique, of abdomen, 107. involuntary, 90. irritability of, 91. latissimus dorsi, 103. levatores costarum, 105. levator palpebrre superioris, 99, 422. names of, 95. nerves of, 92. non-striated, 90. occipito-frontalis, 96. of abdomen, 102, 107, 123. action of, 109. of arm. 110. of back, 102, 122. of chest, 102, 103, 123. of expression, 100, 122. of eyeball, 97, 423, 438. of face, 95, 97. of forearm, 110, 112. of head, 95. of lower extremity, 112, 125. of mastication, 99, 121. of neck, 95, 101, 122. of orbit, 97, 121. of shoulder, 1 10. of thorax, 102, 105. 123. of tongue, 95, 101, 122. of trunk, 102. of upper extremity, 109, 124. orbicularis oris, 100. palpebrarum, 422. orbital, 97. origin of, 95. pectoral, 103. pectoral is major, 103. minor, 105. plain, 90. platysma, 101. posterior femoral, 116. pronators, of forearm, 112. properties of, 91. psoas magnus, 113. quadriceps extensor, 116. recti, of eyeball, 97. rectus abdominis, 108. femoris, 117. sartorius, 115. Muscle, or muscles — continued semimembranosus, 115. semitcndino.sus, 115. skeletal, 89, 94. soleus, 118. sterno-cleido-mastoid, 101. stimuli of, 91. striated, 89. striped, 89. styloglossus, 101. summary, 119. superior oblique, of eyeball, 97. supinators, of forearm, 112. tables of, 121 to 126. tetanus of, 94. tonicity of, 92. transversalis, 108. trapezius, 102. triceps. 111. varieties of, 89. vastus, extcrnus, 117. intermedius, 117. internus, 117. visceral, 90. voluntary, 90. Muscular contractility, 91. sense, 409, 433. system, 26, 32. tissue, 89 ; and see Muscle. Muscularis mucosse, 132. Myelin sheath, 367. Myocardium, 162. Myology, definition of, 14. Myopia, 431, 441. Myxoedema, 314. Nails, 347, 360. Nasal bones, 60. breathing, advantages of, 234, 250. cavities, 19, 20, 234. 250. duct, 423. fossae, 233, 250. Neck, muscles of, 95. 101, 122. Nerve, or nerves, abducens, 396. auditory, 397, 419, 436. -cell, 364, 402. centres, 374, 404. cerebrospinal, 363. cochlear, 419, 436. cranial, 364, 395. degeneration of, 382. -endings, 368. 403. reaction of. 373. facial. 396. -fibres, 367, 402. afferent, 371, 372, 403. classification of, 371, 403. decussation of, 385. efferent, 371, 372, 403. excitatory, 372, 403. funiculi of, 374. • inhibitory, 372, 403. meduUated, 367. INDEX 517 Nerve fibres — continued motor, 371, 372, 403. non-medullated, 368. reflex, 372, 403. secretory, 372, 403. sensorj', 371, 372, 403. ganglia, 376, 381, 404. glossopharyngeal, 397. hypoglossal, 397. impulse, 403. direction of, 371. identity of, 372. nature of, 370. speed of, 373, 403. stimulus necessary for, 399. inferior maxillary, 396. mixed, 380. motor oculi, 396. of eye, 423. of nose, 414. of tongue, 412. olfactory, 396. ophthalmic, 396. optic, 396. pathetic, 396. peripheral, 383. plexus, 370, 377. pneumogastric, 397. processes, 366. regeneration of, 382. spinal, 364, 380, 406. spinal accessory, 397. stimulation, artificial, 370. physiological, 371. superior maxillary-, 396. tissue, properties of, 364, 402. varieties of, 404. trifacial, 396. trochlear, 396. trunks, 404. formation of, 373. vasoconstrictor, 169, 181, 378. vasodilator, 169, 181, 378. vasomotor, 169, 181, 378. vestibular, 420, 436. Nervous system, 26, 32, 363. autonomic, 376. central, 363. interdependence of, 377. divisions of, 363, 401. functions of, 363, 401. gray matter of, 373. parts of, 363, 401. regulation of bodily heat by, 354. sympathetic, 364. white matter of, 373. Neuraxon, 366. Neurilemma, 367. Neuroglia, 364, 373, 404. Neurology, definition of, 14. Neurones, 364, 365, 402. intercentral, 375. Neutralization, 8. I Nipple, 454. I Nitrogen equilibrium, 311, 320. Nodes of Ranvier, 402. Non-medullated nerve-fibre, 368 Nose, 232, 250. external, 232, 250. functions of, 250. internal, 250. nerves of, 414. sinuses communicating with, 234, 250. Nucleus of cell, 22. Obesity, causes of, 309, 320. Oblique muscles, of eyeball, 97. Occipital bone, 53. lobe of cerebrum, 391. Occipito-frontalis, 96. Odontoid process, 66. Odors, 413, 4.34. (Edema, 224, 231. CEsophageal arteries, 193. (Esophagus, 261, 281. Olecranon process, 72. Olfactory bulb, 414. nerve, 414. Omentum, 255, 264. Ophthalmic nerve, 396. Opsonins, 145, 158. Optic chiasm, 429. foramen, 439. nerve, 396, 423. Orbicularis oris, 100. Orbit, 423, 439. bones of, 423, 439'. Orbital cavity, 19, 20. muscles, 97, 423, 438. Organ, 25, 32. of Corti, 419, 436. Organic compounds, 5. Organules, 363, 369. Os coxae, 74. Osmosis, 10, 154. Osmotic pressure, 11. Osseous tissue, 42 ; and see Bone. Ossicles of ear, 416, 435. Osteology, definition of, 14. Otoliths, 418. Ovarian arteries, 197. Ovaries, 442, 463. Overeating, efifects of, 321. Oviducts, 444, 464. 0\-ulation, 452, 465. and menstruation, 453, 465. 0\-um, 443, 460, 408. lecundated, development of, 468. segmentation of, 461. Oxidation, 8. Oxide, 7. acid, 7. basic, 7. Oxyhaemoglobin, 143. Pacini, corpuscles of, 370, 459. Pain, 409, 433. 518 INDEX Filiate, 256. Palate bones, 61. Palatine arches, 256. Palmar arch, deep, 193. superficial, 193. fascia, 37. Pancreas, 272, 283. functions of, 273. structure of, 272. Pancreatic juice, 297. action of, upon food, 297. secretion of, 296. Papillae of skin, 345. of tongue, 411, 434. on mucous membrane, 133. Papillary muscles, 166. Paraglobulin, 14>S, 158. Parathyroids, 315, 322. Parietal bones, 54. lobe of cerebrum, 391. Parotid glands, 257. Patella, 77. Pathetic nerve, 396. Pavement epithelium, 28. Pectoralis major, 103. minor, 105. Pectoral muscles, 103. Pelvic cavity, 20. Pehns, 75. brim of, 76. false, 76. female, 75, 76. inlet of, 76. male, 76. outlet of, 76. strait of, 76. true, 76. Penis, 459, 467. Pepsin, 295. Pericardial arteries, 193. Pericardium, 128, 163. Perichondrium, 42. Perilj-mph, 418. ' Perineum, 451. Periosteum, 44, 48. function of, in growth of bone, 46. Periphery, 17. Peristalsis, 293, 296. Peritoneum, 128, 255. Peroneal artery, 200. Perspiration, 350, 360. insensible, 351. quantity, ,351. .360. sensible. 351. Peyer's glands, or patches, 269. Phagocytosis. 145. Phalanges, of foot, 80. of hand, 74. Pharynx, 234, 260. 280. Phrenic arteries, 197. Physical change, 4. sciences, 3. Physics. 3. Physiological saline solution, 152. Physiology, definition of, 14. Pia mater, 384. Pinna, 414, 435. Pituitary body, 316. membrane, 234. Placenta, 224. Plantar, arch, 200. arteries, 200. fascia, 37. Plasma, -142, 147, 157. Platysma, 101. Pleura, 128, 242, 252. Plexus, arterial, 185. ner\'e, 370, 377. Pneumogastric nerve, 397. Polysaccharids, 288. Pons Varolii, 387, 406. functions of, 388, 406. Popliteal artery, 200. Portal system, 210. vein, 276. Position, anatomical, 14. Poupart's ligament, 107. Premolar teeth, 259. Presbyopia, 432, 441. Pressure sensation, 410, 433. Prickle cells, 30. Process, acromion, 71. ensiform, 69. mastoid, 56. nerve cell, 366. odontoid, 66. of bone, 52. olecranon, 72. xiphoid, 69. Pronator muscles, of forearm, 112. Prostate, 460, 468. Protecting sheaths, 367. . Proteins, adequate, 311. as food, 287, 302. cla.ssification of, 311, 320. digestion of, 290. function of, 311. inadequate, 311. in blood, 147, 158. metabolism of, 310, 311. Prothrombin, 150. Protoplasm, 21. Proximal, 17. Psoas magnus, 113. Ptyalin, 292. Puberty, in female, 451, 465. in male, 460, 468. Pubes, 75. Pulmonary, artery, 185. system, 185, 210. veins, 187. Pulse, 221, 2.30. frequency of, 222, 230. locations where it may be felt, 222, 230. points to note, in feeling, 222, 230. INDEX 519 Pulse — continued ratio of, to respiration, 223. variations in, 223. Pupil, of eye, 426, 440. contraction of, 426. dilatation, 427. Pus, in urine, 338. Pylorus, 263. Quadriceps extensor muscle, 116. Rachitis, bones in, 43. Radial artery, 193. veins, 202. Radius, 72. Rales, 245. Rami communicantes, 376, 377. Ranke's diet, 312. Ranvier, nodes of, 368, 402. Receptaculum chyli, 174. Reciprocal reception, 88. Recti muscles, of eyeball, 97. Rectum, 271. Rectus abdominis, 108. femoris, 117. Reflex act, 397, 407. • arc, 398. nerve fibres, 372, 403. Refracting media, 439. Refraction, 430, 441. Refractive apparatus, 430, 440. Regeneration of nerves, 382. Reil, island of, 391. Relays, 375. Relay station, 369. Remak, fibres of, 368. Renal arteries, 195. corpuscles, 327, 339. Renuin, 295. Reproduction, 460, 468. Reserve air, 246. Residual air, 246, 253. Respiration, 242, 252. abnormal types of, 247, 253. cause of, 243, 252. cause of first, 244, 253. Cheyne-Stokes, 248. control of, 243. effect of, on air, 253. effect of, on blood, 245, 253. effect of, on blood pressure, 220. effect of, on lymph flow, 224. external, 242, 252. frequency of, 245. function of, 242, 252. heat regulation by, 354. internal, 242, 252. cedematous, 248. rate of, 253. ratio of, to pulse, 223, 253. Respiratory centre, 243, 252. reflex stimulation of, 244. movements, modified, 249. Respiratory — continued sounds, 245. system, 26, 32, 232, 234. Restiform bodies, 386. Reticular tissue, 39. Retiform tissue, 39. Retina, 440. layers of, 440. Ribs, 69. Rickets, bones in, 43. Rods and cones, 428. Rotation, 87. Round ligaments, of uterus, 448. Rugae, of stomach, 265. of mucous membrane, 133. of vagina, 449. Rupture, 109. Saccule, 418, 436. Sacral artery, middle, 197. Sacrum, 68, Saline solution, physiological, 152. Saliva, 291. functions of, 292. secretion of, 291. Salivary glands, 257, 280. Salt, 7. as food, 287. in blood, 147, 148, 158. Saphenous veins, external, 206. internal, 205. long, 205. short, 205. Saponification, 289. Sarcolemma, 90. Sartorius, 115. Scapula, 71. Scarpa's triangle, 200. Schneiderian membrane, 234. Sclera, 425, 439. Scrotum, 459, 467. Sebaceous glands, 349, 360. Sebum, 349. Secretin, gastric, 294. Secreting glands, 135. Secretions, 136. external, 136. internal, 136, 313. summary of, 139. table of, 140. Secretory nerve fibres, 372, 403. Segmentation of ovum, 461. Semen, 460, 468. Semicircular canals, 419, 436. Semilunar valves, 167, 181. Semimembranosus, 115. Seminal vesicles, 458, 467. Semitendinosus, 115. Sensations, 408, 433 ; and see Senses. classification of, 408, 433. definition of, 408. organs necessary for, 408, 433. where interpreted, 408. 520 INDEX Sense or senses ; and see Sensations. areas of brain, 394, 407. exterior. 409, 433. external, 409, 433. interior, 408, 433. internal, 408, 433. mu.scular, 409. of e(|uilihrium, 420, 437. of fatigue, 410. of hearing, 420. of hunger, 409. of pain, 409. of pressure, 410, 433. of sight, 421, 429, 437. of smell, 413. of taste, 411. of temperature, 410, 433. of thirst, 409. of touch, 410. visceral, 410. Sensory area of brain, 394, 407. fibres, 371, 372, 403. tracts of spinal cord, 380. Serous sacs, 176. membranes, 127, 137. classes of, 128. function of, 128. of capsule of Tenon, 128. of cavities, 128. of cerebrospinal axis, 128. of vascular system, 128. proper, 128. secretion, 138. Serum, 159. albumin, 148, 158. Sesamoid bones, 49. Sharpcy, fibres of, 44. Sheath, myelin, 367. Shin-bone, 78. Shoulder blade, 71. muscles of, 110. Sighing, 249. Sight, 421, 429, 437. Sigmoid flexure, 270. Simple epithelium, 28. Sinews, 37. Sinuses communicating with nose, 234, 250. of bone, 52. of head, 59. venus, of skull, 201. Sinusitis, 59. Skeletal muscles, 89, 94. Skeleton, 49. attachment of muscles to, 89, 94. divisions of, 52. Skin, 344, 359. appendages, 347. 359. blood-vessels of, 346, 359. discharge of waste matters by, 325, .352. functions of, 344, 352, 359. heat regulation by, 354. Skin — continued layers of, 344, 359. nerves of, 346, 359. summary, 359. Skull, 52. as a whole, 58. bones of, 52. diploe of, 58. Small intestine, 265, 281. action of bacteria in, 299. changes undergone by food in, 296. coats of, 265. digestion in, 295, 305. divisions of, 265. functions of, 269. glands of, 267. lymph nodules of, 268. movements of, 296. Smell, 413, 4.34. necessary conditions for. 413, 434. Sneezing, 249. Sobbing, 249. Soleus, 118. Solution, physiological saline, 152. Speaking, 249. Specific gravity, 9. Speech areas in brain, 394. Spermatic arteries, 197. cord, 459, 467. Spermatozoon, 461, 468. Sphrnoidal fissure, 439. Sphenoid bone, 58. Spina bifida, 68. Spinal-acce.ssory nerve, 397. Spinal canal, 18, 20, 391. cord, 378, 405. central canal of, 391. functions of, 383, 405. membranes of, 378, 405. section of, 379. structure of, 378, 405. tracts of, 380. ganglia, 381. nerves, 364, 380, 406. degeneration of, 382. distribution of terminal branches of, 382. ganglion on posterior root of, 331. regeneration of, 382. roots of, 380. Spinous processes, of bone, 52. of ilium, 75. Splanchnology, definition of, 14. Spleen, 317, .323. Splenic artery, 194. flexure, 271. Sprain, 87. Stapes, 416. Starch, action of saliva on, 292. of pancreatic juice on, 297. Steapsin, 297. Sterno-cleido-mastoid, 101. Sternum, 68. INDEX 521 Stimuli, muscular, 91. nerve, 370, 371. Stomach, 263, 281. blood-vessels of, 265. coats of, 263. digestion in, 293, 305. functions of, 265. glands of, 265. nerves of, 265. peristaltic action of, 293. Stratified epithelium, 30. Styloglossus, 101. Subarachnoid space, 384. Subclavian arteries, 192. veins, 204, 212. Sublingual glands, 257. Subniaxillary glands, 257 Succus entericus, 298. Sugar, 288. in blood, 148, 158. Summation, 366. Superior maxillary nerve, 396. Supinator muscles, of forearm, 112. Suprarenal arteries, 196. capsules, 316, 322. Sutures, 82, 87. coronal, 82. frontal, 83. lambdoidal, 82. of skull, 83, 84. sagittal, 83. Swallowing, 292. Sweat, 350 ; and see Perspiration. Sweat-glands, 350, 360. Sylvius, aqueduct of, 392. Sympathetic ganglia, 376, 405. system, 375, 401. interdependence of, 377. Symphysis, 84, 88. pubis, 75. Synapse, 366, 402. Synarthroses, 82, 87. Synchondrosis, 83, 87. Syndcsmology, definition of, 14. Syndesmosis, 85, 88. Synovia, 129. Synovial membranes, 129. function of, 130. System, 26, 32. Systole, 216. Tactil.e corpuscles, 370. Tarsal cartilages, 421, 422. glands, 422. Tarsus, bones of, 78, 81. of eye, 421, 422. Taste, 411, 434. buds, 411, 434. necessary conditions for, 411. organ of, 411, 434. sense of, 411, 434. Taste buds, 411, 434. Tears, 438. Teeth, 257, 280. function of, 260. permanent, 259. temporary, 259. Temperature, necessary for digestion, 292. sense of, 410, 433. subnormal, 358. variations in, 357, 358, 362. Temporal bones, 55. mastoid portion of, 56. petrous portion of, 55. squamous portion of, 55. lobe of cerebrum, 391. Tendo Achillis, 118. Tendons, 37, 94. Tenon, capsule of, 424. Terminal ganglia, 376, 405. Testes, 457, 467. descent of, 458. Testicle, 457 ; and see Testes. Tetanus of muscle, 94. Thermogenetic centres, 355. Thermolytic centres, 355. Thermotactic centres, 355. Thigh, adductor muscles of, 115. bones of, 77. Thirst, 409, 433. Thoracic cavity, 19, 20. duct, 174, 182. parts drained by, 173, )?4, 182. Thorax, 67, 68. bones of, 68. muscles of, 102, 105, 123. Thrombin, 150. Thrombus, 152, 159. Thymus, 315, 322. Thyroid, accessory, 314. cartilage, 235. foramen, 75. gland, 313, 321. Tibia, 78. Tibial arteries, 200. veins, 205. Tidal air, 245. Tissue, or tissues, 25, 32. adenoid, 40. adipose, 38. areolar, 34. classification of, 26, 32. connective, 34 ; and see Connective tissues. definition of, 25. elastic, 37. epithelial, 27 ; and see Epithelial tissue. fibrous, 35. lymphoid, 40. muscular, 89 ; and see Muscle. nerve, 364 ; and see Nerve. origin of, 26, 32. osseous, 42 ; and see Bone. reticular, 39. retiform, 39. • 522 INDEX Tone, arterial, 170. Tongue. 257, 280. 411. 434. muscles of, try a required study and it is rapidly becoming recognized, in an increasing number of states, as a necessary part of the course. Up to the present, no textbook on elementary chemi'.try has been published distinctly tor nurses. Dr. Ottenberg has, therefore, prepared this splcndiii little book, which presents the subject, for the course in training schools, with s m- plicity and thoroughness. The fault of the elementary textbooks on chemistry, previously used in this course for want of a distinct te.xt for nurses, seems to lie in the fait that tliey do not take up the special points without which a knowledge of Dietetics or food values is impossible, while the more advanced te.xts are entirely too difficult for nurses, since they presuppose an amount of preliminary training which very few nurses have. It is believed that Chemistry for Nurses will fill a definite need, as pupil nurses have repeatedly asked for a text-book to answer their peculiar require- ments. Bacteriology for Nurses Including Schedule for Laboratory Exercises, etc. By IS.^BEL McISAAC Superintendent United States Army Norse Corps; Author of " Hygiene for Nurses," etc Second Edition. Revised. Cloth, illustrated, $ 1.25 This is a completely revised edition of the well-known textbook which has, for years, been ihe only book written distinctly for the use of nurses, and much new material has been added. The author has carefully confined herself to the needs of the c ass for whom it is intended and she has been singularly success- ful in avoiding unnecessary digfression, making clear the practical as well as the theoretical. The scheme of the original work has been maintained. There are chapters on Structure, Mode of Development, and Composition of Bacteria ; The Effect of Physical and Chemical Agents upon Bacteria, and the Kffects of Bacterial Growth; The Relations of Bacteiia to Disease; Immunity; Inflammation, Suppuration, Pneumonia, Epidemic Cerebro-Spinal Meningitis; Typhoid Fever (Enteric Fever) ; Asiatic Cholera, Relapsing Fever; Infectious Diseases of Unknown Cause, and Bacteria in Air, Soil, Water, and Food. THE MACMILLAN COMPANY Publishers 64-66 Fifth Avenue New Tork NEW AND STANDARD BOOKS FOR NURSES Hygiene for Nurses By ISABEL McISAAC Superintendent U. S. Army Nurse Corps. Formerly Superintendent of the Illinois Training School of Nurses Cloth, 127710, $1.25 The pages of this book are full of just the information that every woman in charge of souls and bodies needs. The chapters on food, ventilation, sewage, causes and dissemination of disease, household, personal, and school hygiene, the hygiene of occupation, disinfection, etc., are all of the most vital interest and value to the nurse. Primary Nursing Technique FOR FIRST YEAR PUPIL NURSES By ISABEL McISAAC Cloth, 127710, $1.25 A valuable and thorough book for nurses starting on their course of study. It is written with the one object in view of inculcating into the minds of its readers the fact that an accurate knowledge of the human body is the first essential to successful nursing. Nursing the Insane By CLARA BARRUS Woman Assistant Physician in the Middletown State Homeopathic Hospital, Middletown, N.Y. Cloth, 8vo, $2.00 This is an illuminative, sensible, straightforward book covering the various features of the nurse's work in caring for the insane. There are directions, not only for medical and clinical care of the insane, for their occupation and amusements, with directions as to how they may be moved, but above all there are some very interesting chap- ters on psychology, so that the nurse may appreciate patients' states of mind and sympathize with their peculiarities. THE MACMILLAN COMPANY Publishers 64-66 Fifth Avenue New York NEW AND STANDARD BOOKS FOR NURSES The Life of Florence Nightingale WITH PHOTOGRAVURE PORTRAITS By sir EDWARD COOK Two vols., cloth, 8vo. $7.jo "A masterly biography which not only puts into a permanent record her whole-souled devotion and humanity, but relates the his- tory of one of the greatest and most fruitful movements of modern times. He has put the essence of saintliness into good literature and sober history." — Pall Mall Gazette. " We have no hesitation in saying that this work will live as one of the greatest biographies in the English language.'"— The Daily Chronicle. London. " No one can read this remarkable book with its detailed descrip- tion of brave and unflagging work without endorsing so fine a tribute. There are portraits in these volumes, and the work, apart from its fascmation as a biography, throws a flood of life on the manner in which Florence Nightingale lifted nursing from a despised calling to one of the most honorable vocations open to modern womanhood." — The Standard, London. The Life of Florence Nightingale By SARAH A. TOOLEY Author of " Personal Life of Queen Victoria," etc. With twenty-two Illustrations. Cloth, i2mo, $i.7S In writing this book the author has had the assistance of many of Miss Nightingale's closest associates during her active years, and has produced a singularly interesting volume that reflects Miss Nightin- gale's character and personality in the happiest way. THE MACMILLAN COMPANY Publishers 64-66 Fifth Avenue New York " We have no hesitation in saying that this work will live as one of the greatest biographies in the English language." — The Daily Chronicle, London. The Life of Florence Nightingale By sir EDWARD COOK, WITH PHOTOGRAVURE PORTRAITS Cloth, Svo, $7.50 carriage extra TWO VOLUMES "This book," says the author in his Introductory remarks to this notable biography, "is not a history of the Crimean War, nor of nursing, nor of Indian administration. Something on all these matters will be found in it; but only so much of detail as was necessary to place Miss Nightingale's work in its true light and to exhibit her charac- teristic methods. So, also, many other persons will pass across the stage — persons drawn from many different classes, occupations, walks in life; but the book does not aim at giving a detailed picture of 'Miss Nightingale's circle.' Her relations, her friends, her acquaintances, her correspondents only concern us here in so far as their dealings with her affected her work, or illustrate her character." The biography is in two volumes and is divided into seven Parts. Part I tells the story of Florence Nightingale's early years and her early aspirations for a Hfe of active use- fulness. Part II is devoted to the Crimean War, where it was as Administrator and Reformer rather than as the Ministering Angel — the Lady With the Lamp — that her peculiar powers were shown. Part III portrays her laying her plans for the health of the British Soldier — the period of her close co-operation with Sidney Herbert. Part IV describes, as its main themes, the work she did as Hospital Reformer and the Founder of Modern Nursing. Part V deals with a new interest in her life and a new sphere of her work. Her efforts on behalf of the British soldier at home led to a like attempt for the army in India. Then gradually she was drawn into other questions, till she became a keen Indian reformer all along the line. Part VI continues this subject, and intro- duces another sphere in which her influence had important significance, namely, the reform of the Workhouse Nursing; and as one thing led to another it will be seen that Florence Nightingale deserves also to be remembered as a Poor Law Reformer. Part VII comprises the last thirty-eight years of her life — a period which, though it has admitted of more summary treatment, was full of interest. It deals with her literary work and her studies in Plato and Christian Mystics. An endeavor is made to portray her as the "'Mother-Chief" (as she was called) of the nurses. It describes other of her projects and realizations, and so brings the long and wonderful life to a close. It should be pointed out that for the purposes of this work Sir Edward Cook has had access to the family papers, and has therefore been able to prepare the first full and authentic record of Florence Nightingale's character and career. The volumes are rendered additionally attractive by the inclusion of several interesting portraits. PRESS COMMENTS "A masterly biography which not only puts into a permanent record her whole-souled devotion and humanity, but relates the history of one of the greatest and most fruitful movements of modern time. For as Sir Edward well says, her nursing mission in the Crimean War was only thfe starting point. . . . "He has put the essence of saintliness into good literature and sober history." — The Pall Mall Gazette. ''.\ noble biography." — The Daily News, London. "A book of surpassing charm, worthy of the theme; in fine, a great biography of a great woman. ... A wonderful life-story of Florence Nightingale." — The Daily Chronicle, London. "No one can read this remarkable book with its detailed description of brave and un- flagging work without endorsing so fine a tribute. There are portraits in these volumes, and the work, apart from its fascination as a biography, throws a flood of light on the manner in which Florence Nightingale lifted nursing from a despised calling to one of the most honourable vocations open to modern womanhood." — The Standard, London, PUBLISHED BY THE MACMILLAN COMPANY Publishers 64-66 Fifth Avenue New York