(2P34' BBS3 Columbia ^nibersitp^TX' inti)eCitpof J^ctogorfe College of ^fjpsicians anb ^uigeonsi ^tttvmtt Ilibrarp r;:^ 1 Presented hy DR. WILLIAM J. GIES^^ to enrich the library resources availc\Sle to holders ofthe GlES FELLOWSHIP in Biolo3ical Chemistry 1f ^>p x/ ADVANCED LESSONS IN Practical Physiology FOR STUDENTS OF MEDICINE By RUSSELL BURTON-OPITZ S. M., M. D., Ph. D. Associate Professor of Physiology, Columbia University; Professorial Lecturer in Physiology in Teachers College and the Extension Department of Columbia University ILLUSTRATED PHILADELPHIA AND LONDON W. B. SAUNDERS COMPANY 1920 Copyright, 1920, by W. B. Saunders Company PRINTED IN AMERICA PRESS OF W. B. SAUNDERS COMPANY PHILADELPHIA CONTENTS PAGE Introduction 17 General Directions 20 LESSON I Muscle and Nerve 21 Ameboid and Ciliary Motion. Methods of Stimulation 21 LESSON^ II Muscle and Nerve (Continued) 25 Myography 25 LESSON III Muscle and Nerve (Continued) 35 Irritability, Conductivity, and Elasticity of Muscle. The Power of Muscle Tissue in Relation to the Cross-section and Arrangement of Its Fibers 35 LESSON IV Muscle and Nerve (Continued) 41 Single Contraction, Summation and Fusion of Contractions. Tetanus. Influence of Changes in the Strength of the Stimulus and Load of the Muscle 41 LESSON V Muscle and Nerve (Continued) 47 Influence of Temperature, Chemicals, and Fatigue Upon the Contraction of Muscle 47 LESSON VI Muscle and Nerve (Continued) 51 Contraction of Human Muscle. Influence of Blood-supply. Smooth Muscle 51 LESSON VII Muscle and Nerve (Continued) 59 Speed of the Nerve Impulse in the Frog and Man. Conduction in Both Directions 55 LESSON VIII Muscle and Nerve (Continued) 59 Conduction in Nerve. Action Current of Muscle and Nerve. Stimulation of Motor Points 59 LESSON IX Muscle and Nerve (Concluded) 63 Electrotonus. Cathodic and Anodic Excitation. Law of Unipolar Stimu- lation of Human Muscle and Nerve G3 LESSON X The Blood 67 The Coagulation of the Blood. Counting of the Blood-corpuscles 67 13 14 CONTENTS LESSON XI PAGE The Blood (Continued) 73 The Counting of Human Blood-corpuscles. Specific Gravity and Ap- pearance of Blood 73 LESSON XII The Blood (Concluded) 77 Medicolegal Tests for Blood 77 LESSON XIII The Heart 79 Registration of the Heart-beat. Refractory Period. Extrasystole. Ex- cised Heart. Action of Strips of Ventricular Tissue 79 LESSON XIV The Heart (Continued) 85 Inhibition and Acceleration of the Simple Heart. Action of Nicotin, Atropin, and Muscarin 85 LESSON XV The Heart (Continued) 89 Stannius' Experiment. Staircase Phenomenon. Summation of Stimuli. Action of the Constant Current, Ether, and Chloroform. Dissection of the Mammalian Heart 89 LESSON XVI The Heart (Continued) 91 The Beating Mammalian Heart. Heart-block. Fibrillation 91 LESSON XVII The Heart (Concluded) 95 Percussion and Auscultation of the Human Heart Under Different Con- ditions 95 LESSON XVIII The Circulation 99 The Capillary Circulation. Conversion of an Intermittent Into a Constant Flow. Schema of the Circulation 99 LESSON XIX The Circulation (Continued) 103 The Cause and Velocity of the Pulse. Direct Method of Ascertaining the Blood-pressure 103 LESSON XX The Circulation (Continued) 109 Venous Valves. Influence of Dyspnea Upon the Blood-pressure. Action of Amyl Nitrite and Ardenalin. Hemorrhage 109 LESSON XXI The Circulation (Continued) 113 The Effect of Divi.sion and Stimulation of the Vagus Nerve Upon the Blood- pressure and Action of the Heart 113 LESSON XXII The Circulation (Continued) 117 The Vasomotor Action of the Cervical Sympathetic, Depressor, and Sciatic Nerves 117 CONTENTS 15 LESSON XX 111 PAG.: The CmcuLATioN (Continued) 121 The Vasomotor Action of the Greater Splanchnic Nerve. The Vascularity of the Kidney. Oncometry 121 LESSON XXIV The Circulation (Continued) 12.5 The Indirect Method of Measuring Blood-pressure. Effect of Posture and Exercise 125 LESSON XXV The Circulation (Concluded) 129 The Character and Velocity of the Arterial and Venous Pulsations. Polyg- rajihy ■ 129 LESSON XXVI Respiration 133 Mechanics of Respiration 133 LESSON XXVll Respiration (Continued) : . 139 Stethography. Methods of Artificial Respiration. Pulmotor 139 LESSON XXVIII Respir.\tion (Continued) 141 Nervous Regulation of Respiration 141 LESSON XXIX Respiration (Continued) 145 Localization of the Respiratory Center. Placenta. Respiration in the Fish 145 LESSON XXX Respiration (Continued) 147 The Circulation in the Lung of the Frog. Phenomena of Inflammation. Effect of Changes in Intrathoracic Pressure Upon the Lesser Circuit . . 147 LESSON XXXI Respiration (Concluded) 151 Elimination of Carbon Dioxid and Consumption of Oxygen 151 LESSON XXXII The Nervous System 155 Reflex Action 155 LESSON XXXIII The Nervous System (Continued) 159 Reflex Action. Removal of Cerebrum 159 LESSON XXXIV The Nervous System (Continued) 163 Stimulation of the Cerebrum. The Function of the Roots of the Spinal Cord 163 LESSON XXXV The Nervous System (Conchided) 165 Reaction Time 165 LESSON XXXVI The Sense Organs 167 Cutaneous and Muscular Sensations 167 16 CONTENTS LESSON XXXVII PAGE The Sense Organs (Continued) 173 Taste, Smell, Hearing 173 LESSON XXXVIII The Sense Organs (Continued) 179 The Static and Dynamic Senses 179 LESSON XXXIX The Sense Organs (Continued) 183 Vision 183 LESSON XL The Sense Organs (Continued) 189 Vision 189 LESSON XLI The Sense Organs (Continued) 193 Vision 193 LESSON XLII The Sense Organs (Concluded) 199 Vision 199 LESSON XLIII Digestion 207 Deglutition 207 LESSON XLIV Digestion (Continued) 209 Secretion of Saliva 209 LESSON XLV Digestion (Continued) 213 Secretion of Pancreatic Juice. Action of Secretion. Gastro-enterostomy. 213 LESSON XLVI Digestion (Concluded) 215 Lacteals and Thoracic Duct. Peristalsis. Secretion of Bile 215 LESSON XLVII Absorption 217 Osmosis. Intestinal Peristalsis, Secretion of Intestinal Juice. Absorption From the Small Intestine 217 LESSON XLVIII Excretion 221 Secretion of Urine 221 LESSON XLIX Excretion (Continued) 223 Secretion of Sweat. Body Temperature 223 LESSON L Excretion (Concluded) 225 The Innervation of the Bladder. Pilomotor Reactions 225 Demonstrations to be Given in Connection with the PRECEniNG Lessons. 227 Weights and Measures 229 Index 231 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY INTRODUCTION In order to prepare the medical student for the clinical work that is to follow during his subsequent years of study, the subject of physi- ology must be presented to him in an eminently practical manner. For this reason the purely didactic lectures of not so many years ago have gradually been displaced by more or less informal discourses between the lecturer and students, pertaining more particularly to topics of unusual complexity and clinical value. Furthermore, the experi- ments which formerly constituted a large part of the physiologic lec- ture, have since been separated from the purely didactic subject matter and have been combined into a continuous course of practical exercises and demonstrations. The earlier "experimental lectures" have failed in their purpose, because much time was frequently wasted in overcoming technical dif- ficulties not apparent at the beginning of the hour, and because little opportunity was afforded the students to become acquainted with the apparatus and the technic required to perform physiologic experi- ments. These difficulties have been met in large part by instituting a course in practical physiology, designed so that the student himself may perform simple and instructive experiments. Obviously, the ac- quisition of knowledge by the laboratory method consumes a longer period of time and requires a definite experimental aptitude on the part of the student. Furthermore, this method of teaching entails the expenditure of large sums of money for apparatus and the salaries of additional teachers. These difficulties, however, have been overcome in recent years in all the schools of higher grade, and practical courses in physiology are now an accomplished fact, and rightly so, because the benefits which the students derive from work of this kind cannot be overestimatctl. - It cultivates the faculty of close observation and ac- curate rating of facts. It develops the power of logical thought and expression, and impresses upon them facts and principles otherwise scarcely noted and comprehended. Indeed, many students nnist see things in order to be able to obtain a clear mental picture of them, but when once seen, the impression is lasting. Where else than in medicine could this manner of teaching be of greater service? Quite aside from the fact that this method constitutes an admirable means of imparting physiologic knowledge, it also enables the students 2 17 18 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY to familiarize themselves with the use of operative instruments and the action of different drugs. During a course of this kind each student is repeated^ called upon to attend to the narcosis; to perform trache- otomj^; to expose and ligate blood-vessels, and to isolate nerves and other structures. It need scarcely be emphasized that the operative technic acquired by him upon animals under test conditions, will serve hmi in good stead later on when forced to repeat these procedures upon human beings. The contention that students may derive their knowledge of physi- ology wholly from practical work, is scarcely worthy of consideration. While the average student is well able to abstract definite single facts from experiments, he is as yet in no position to appraise these facts and to combine them into a connected story of physiologic events. Knowl- edge gained by experunentation alone is, indeed, very fragmentary. It is the duty of the lecturer to bridge over these defects and to supply the student with those fundamental data which he is to make use of later on in formulating physiologic principles. Facts, as such, are of little value unless they can be joined to yield certain truths which have a dii-ect bearing upon the student's subsequent clinical work. The student should be made to "physiologize" along lines more closely re- lated to his chosen profession and should attain this state in as short a time as possible. In many instances this mental evolution may be greatly facilitated by referring to problems of general interest, such as may be obtained from treatises upon comparative physiology, biology, physics, and chemistry. Comparative physiology, in particular, is very rich in facts which will greatly aid the lecturer in clearing up doubtful or complex points in special physiology. In the medical schools of higher grade about three hundred hours are allotted to physiology, exclusive of physiologic chemistry and clinical physiology or experimental medicine. This period of time is spent in part in the laboratory and in part in the lecture room. As a rule, one hundred and eighty hours are assigned to practical work and one hundred and twenty hours to lectures and conferences. Inasmuch as the academic year usually comprises thirty weeks, exclusive of the time set aside for examinations, the above enumeration leads us to infer that each student must devote ten hours per week to physiology. In many institutions, however, the ''concentrated" system of teaching is employed, enabling the student by constant daily attendance to com- plete his work in phj^siology within about four months — similar periods of time being set aside for anatomy and physiologic chemistry. Before submitting these lessons in practical physiology to the stu- dents I should like to mention that I have attempted to embody in them all those experiments which can be conveniently performed with the aid of simple apparatus. The lessons begin with experiments upon muscle and nerve, and gradually make a greater and greater demand upon the experimental aptitude of the student. Those experi- ments which require complex apparatus and may be more conveniently INTRODUCTION 19 displa^'cd to a large number of students, have been embodied in the demonstrations. A brief list of experiments of this kind is given on pages 227, 228. While it is difficult to perform physiologic experiments in accordance with a definite time-schedule, the material embodied in this book has been arranged in such a way that each lesson will require about three hours for its completion and each demonstration one hour, making a total of one -iiundrod and eighty hours. At the end of each period a few minutes should Ije set aside for a review of the work performed. Special attention should at this time be paid to those students who have failed to observe and formulate the essential facts and principles to be derived from any particular lesson. It would be a pedagogically un- sound principle to call the attention of the students to these facts before- hand, because introductory explanations tend to rob the student of the pleasure of independent investigation and thought. If the work in physiology is well balanced and co-ordinated between the class-room and the laboratory, preliminary talks pertaining to the general bearing of the different experiments are actually worse than useless. Such discussions should concern themselves more particularly with matters closely related to the methods and apparatus, so that the student may be in a more favorable position to avoid mistakes in his technic. I have endeavored to aid him in this regard by supplying him with this laboratory guide, amplified, for the reason just stated, with explana- tions bearing directly upon the experiments. R. Burton-Opitz. Columbia University, May, 1920. GENERAL DIRECTIONS Each class of students should be divided into sections of not more than 40 each. To each section should be allotted 4 assistants, so that each assistant may be held responsible for the work of 10 students, arranged in pairs. A larger number than this cannot well be attended to by one instructor. When mammals are being used, as many as 8 students may be assigned to one operating table. The formation of larger groups is not to be recommended, because it lessens the chances of the individual student to perform a considerable part of the work himself. Neither does it seem advisable to decrease this number materially, owing to the fact that such reduction would necessitate an extra expenditure for apparatus and material which is not proportional to the increase in the efficiencj^ of the teaching. Since the work of the students requires close supervision, one assistant should be assigned to each operating table. If an additional table is put in use, these students should re- ceive the necessary attention from the instructors at the two neighbor- ing tables. The function of the instructor is to advise the students how to proceed, and to guide them by pertinent questions and practical hints through the work assigned to them. Nothing should be told the stu- dents which they can readily discover for themselves, and nothing should be done for them which they can conveniently do themselves. At least, this plan of teaching should be followed as soon as the students have received their first instruction in etherization, in performing trache- otoni}', and in exposing different blood-vessels. A record should be kept of the work done by each student during every exercise, so that a different task may be assigned to him during the succeeding exercise. Each student should make brief entries in his note-book pertaining to the results and bearing of the experiments performed by him. In addition, this book should contain diagrams of the apparatus, explana- tory schemas, and the curves recorded by him in the course of these practical exercises. Each pair of students should be in possession of a set of operating instruments, embracing two pairs of forceps, two pairs of scissors of different size, and two scalpels of different size. Ligatures, sponges, ether, and towels will be supplied by the attendant. A rubber apron should be worn by every student during the experiments upon mam- mals. Dissecting gowns and instruments are not regarded with favor in the phj'siologic laboratory. At the end of each session the apparatus is to be taken apart and each piece carefully cleaned. Special receptacles are provided for the discarded organic material. 20 LESSON I MUSCLE AND NERVE AMEBOID AND CILIARY MOTION. METHODS OF STIMULATION 1. Ameboid Motion. — Place a few drops of a hay infusion upon a glass slide. Bring a large and active ameba into the field of the micro- scope. Observe carefully the behavior and position of the organism, making drawings of its shape at regular intervals. Add a few granules of India-ink to the medium and observe how these particles are engulfed. 2. Protoplasmic Streaming.^ — Examine with the low power of a microscope a leaflet of a fresh specimen of nitella. Observe the move- ment of the protoplasm. What part of the cell is in motion? In which direction does the flow take place? How is the movement changed by mechanical stimuli? Note the effect of warmth upon the movement. 3. Ciliary Motion. — Etherize a frog and destroy its brain and spinal cord. Place the animal upon its back. Make a median incision through the lower jaw, and retract the segments laterally. Place a small piece of cork upon the mucous surface between the eyes. Moisten the sur- face with normal saline solution, if necessary. Note how the piece of cork is gradually carried by the action of the cilia toward the esophagus. Determine its rate of movement. Moisten the surface with normal saline solution the temperature of which has been raised 2 or 3 degrees above that of the room. Note the effect upon the movement of the cork. Tilt the plate upon which the frog is resting until the cilia are no longer able to move the piece of cork. Hold the plate horizontally and put small bits of lead upon the cork until one is found which the cilia are unable to propel. What is your idea regarding the strength of these structures? Place a small segment of the gill-plate of a fresh clam upon a slide for microscopic observation. Straighten its edge and immerse the entire preparation in a few drops of the fluid obtained when the shell of the clam was opened. Study carefully the action of the cilia at in- tervals, and especially later on, when their movement has been consider- ably slowed so that single cilia may l)e clearly made out. What is the position of the cilia when at rest and when contracting? Apply normal saline solution which has been slightly heated (25° C). Note its effect upon the rapidity of the movement. 4. Structure of the Dififerent Types of Muscle Tissue. — Unless still quite familiar with the general structure of non-striated, striated, and cardiac muscle, examine preparations of these tissues under the micro- scope. Study the action of the myoids in stentor or vorticella. 21 22 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 5. Muscular Movement.— With a small blunt instrument scrape off the wing muscles of a beetle (hydrophilus) and place them upon a slide for microscopic study. Observe the waves of contraction passing over the individual muscle-fibers. Note the increase in the diameter of the fiber at the point of contraction. 6. Stimuli. Muscle-nerve Preparation. — Living substance possesses the properties of irritability, conductivity, and contractility, i. e., it is capable of receiving a stimulus, of conducting it to some other part of its substance, and of reacting toward it in accordance with its struc- tural peculiarities. A stimulus is any extraordinary change in the Fig. 1. — Muscles of Hind Leg of Frog. (Ecker.) environment of the living entity, in consequence of which it evolves some form of energy. In this way a muscle may be made to contract and a gland to secrete. As a matter of convenience we usually employ the former tissue and principally that derived from the frog. Grasp the pelvis of a lightly etherized frog between the thumb and index-finger of your left hand, allowing the ventral aspect of the thorax and head to rest upon your third and fourth fingers. With your right hand move the point of a small scalpel rapidly backward from between the eyes until you feel a depression at the junction of the head with the spinal column. This depression lies at the atlo-axoid articulation. MUSCLE AND NERVE 2'^ Gently pross tho point of tho scjilpol ti-:msvorse!y into this opening, dividinji; the si)in;il cord. Introduce ;i seeker throufi;li the incisi(jn, and, passing it upward into the cranial cavity, quickly destroy the cerebrum. Reverse the direction of the seeker and pass it downward through the vertebral canal, destroying the cord. This operation should consume only a few seconds of time. It is known as pithing, and corresponds to the destruction of the spinal cord of mammals by the excessive flexion of the head npon the spinal column. The odontoid process of the axis then lacerates the cord. Amputate one leg. Remove the skin from the thigh and isolate the sciatic nerve. Cut away the muscles of the thigh, })ut preserve the femur and nerve. Suspend the leg from a clamp fastened horizontally to an iron stand by fixing the femur in its screw clip. Attach the central end of the sciatic nerve to a needle-holder and moisten the preparation with an isotonic solution of sodium chloric! (0.7 per cent.). 7. Direct and Indirect Stimulation of Muscle. — Use the following means to cause a contraction of the calf muscle (gastrocnemius) : (a) Mechanical stimulation. Pinch the end of the nerve with the forceps. (6) Chemical stimulation. Dip the end of the nerve in a strong solution of sodium chlorid. Cut away the piece of the nerve used. (c) Thermal stimulation. Heat a piece of wire and bring it in con- tact with the nerve. {d) Electric stimulation. Apply the electrodes from the secondary coil of an inductorium to the nerve. Close, and open the key inserted in the primary circuit. (e) Photic stimulation. Under these conditions rays of light do not serve as a stimulus. Place your index-finger under the sole of the foot and repeat the electric stimulation. Explain the action of the gastrocnemius muscle. Remove the skin. Stimulate the muscle directly. Which stimulation is more effective? Locate the tendo achillis. Carefully dissect the other leg and iden- tify the sartorius and gracilis muscles. Open the abdomen of the frog and trace the sciatic nerve to its point of origin from the spinal cord. LESSON II MUSCLE AND NERVE (Continued) MYOGRAPHY 1. The Construction and Action of the Dry Cell. — The electric method of stimulation is employed most frequently in the laboratory because it is the most convenient. The electric enereiy is derived, as a rule, from a Voltaic cell. As a generator may be employed a Daniell, Grove, or Leclanch6 cell. The moist cells, however, have been dis- placed in the course of time by the so-called dry cells which give off no fumes and acids, need no refilling, and give, as a rule, good service at slighter cost. The dry cell connnonly used is a modification of the Leclanche cell. It consists of a jacket of zinc lined with plaster of Paris and saturated with ammonium chlorid. Its inner space is taken up by a carbon plate which is surrounded by black oxid of manganese. The plate of carbon projecting from this mixture forms the posi- tive pole or anode, whereas the negative pole or cathode is represented by the zinc. Electricity "flows" from a place of high potential to a place of low potential. Hence, if the carbon and zinc of the battery are con- nected by means of a conductor, say, a copper wire, a current is set up which leaves the generator at the former pole and enters it at the latter. Inside the cell the current flows from the zinc to the carbon to complete the circuit (Fig. 2). The difference in the potential between the two poles of a battery constitutes the electromotive force. It is maintained by the interaction of the chemical substances con- tained in the battery. The latter, therefore, corresponds to a reservoir of electricity which remains filled as long as there is enough material present to yield chemical energy. When this material has been used up, the difference in the electric po- tential disappears and the current ceases. In its passage through wires the electric current loses a certain amount of its initial energy, owing to the resistance which it must first overcome. Consequently, the strength of a current or the rate of flow Fig. 2. — Diagram of Daniell Cell. Cu, Copper plate (+); Z, zinc plate ( — ). The direc- tion of the current is indi- cated by the arrows. 26 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY of electricity between two different points of the conducting path is dependent not onl}^ upon the electromotive force but also upon the resistance of the conductor. A short and thick wu-e possesses less resistance than a long and thin wire; hence, provided that the electro- motive force remains constant, the flow of electricity will be greater in the first instance. Besides this external resistance encountered by the current in its passage from the copper to the zinc, it is also opposed b}'- an internal resistance resident in the constituents of the battery. In the latter case, the resistance is the less the larger the surface of the plates. A unit of current is designated as an ampere, a unit of electromotive force as a volt, and a unit of resistance as an ohm. An ohm equals the resistance of a volume of mercury 1 mm. in area and 1063 mm. in length at 0° C. The electromotive force of a Daniell cell is about 1 volt and that of an ordinary dry cell 1.5 volt. The relationship existing between these different factors is expressed by Ohm's law, in accordance with which the , , ^, electrom. force volts current strength = : ; or amperes = mt. res. and ext. res. ohms Any one of these factors may be determined as follows : volts = amperes X ohms amperes = volts -^- ohms ohms = volts -^ amperes Fig. 3. — Mercury Key. 2. The Simple Key. — Living substance may be stimulated with an electric current by simply touching it with the ends of the loose wires leading out from the poles of a battery. A better way, however, is to leave the wires in firm contact with the living substance and to stimu- late it by making and breaking the current by means of a key. Three kinds of keys are commonly used in the laboratory, namely, mercury, friction (DuBois-Reymond), and automatic keys. The mercury key consists of a round wooden base weighted with iron. The center of its upper surface is depressed for the recep- MUSCLE AND NERVE 2- tion of a small vulcanite cup which is partially filled with mercury. To the sides of the wooden base are attached two brass rods. The inner ends of these dip into the mercury, while their outer ends are Fig. 4. — Morse Key. connected by means of binding-posts with the poles of the battery. One of these rods is jointed so that its inner end may be dipped into the mercurj'- or removed from it at will, thereby making and breaking the current. The friction key consists of a vulcanite base to which are attached two oblong bars, II and III, each of which is equipped with two binding-posts. Bars II and III are joined by a third bar, IV, which is jointed at one end and may be elevated at its other end, thereby breaking the contact between II and III. On lowering this bridge the current is made, while on raising it it is broken. The automatic key presents many forms. It consists, as a rule, of a rotating disk to which are at- tached a number of contacts. Since the speed of the disk and the position of these contacts may be varied, it is possible to make and break the circuit without effort and at definite intervals. 3. Stimulating Electrodes. — The elec- tric current may l)e conve3Td through living matter by simply applying the ends of the copper wires to its surface. The closure of the key then completes the circuit from carbon to zinc. ]\Iost com- monly, however, the ends of the copper wires are brought close together and soldered to platinum points. They are then placed within a narrow piece of hard rubber, so that they can be conveniently handled. This form of electrode cannot be used for a long time, because the conduction of an electric current through moist Fig. 5. — Friction Key. 28 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY conductors, such as are presented by animal tissue, invariably leads to a polarization of the current. The two metals of the battery, copper and zinc, are smTOunded by electrolytes, the tendency of which is to pass toward the opposite pole. Thus, the positive ions, Cu and H, progress toward the cathode, whereas the OH and SO4 pass toward the anode, which inside the cell is the zinc. Presently the copper plate becomes covered with bubbles of H, which place a high resistance in the path of the current and eventually neutralize it. This phenomenon is known as polarization. A similar action takes place at the points of contact between the electrodes and the tissue. It may be prevented by the use of the so- called non-polarizable electrodes. Those devised by DuBois-Reymond consist of zinc terminals immersed in a solution of zinc sulphate. A Fig. 6. — Stimulating Electrodes. A, B, and C, Boot electrodes; D and E, clinical electrodes; F, hand electrodes. Apparatus Co.) {Harvard very simple form may be constructed by taking two pieces of glass tub- ing, measuring 4 mm. in diameter and 6 mm. in length. One end of each tube is filled with modeling clay moistened with normal saline solution. Above the plug the tube is filled with a saturated solution of sulphate of zinc into which is placed a short rod of amalgamated zinc carrying the ends of the copper wires. The points of contact with the tissue are wrapped in cotton moistened with saline solution. These electrodes must be immersed in saline solution for some hours before they are used so as to render the clay permeable (Fig. 7). 4. The Different Types of Electric Currents. — If the two poles of a battery are connected with one another by wires and a simple key, the current begins to flow as soon as the bridge has been closed, and ceases to flow after the latter has been opened. The strength of this current MUSCLE AND NERVE 29 remains the same as long as the electromotive force and the resistance do not change. A current of this kind is known as a constant or gal- vanic current. If a coil of insulated wire is arranged around a ring of iron, it will be found that the passage of a constant current through the iron sets up an electric variation in the outside spool of wire. This secondary current, however, develops only on the make and break of the primary current traversing the iron. An electric energy appearing in this form is called an induced current. Moreover, since the primaiy current may be made and broken at long and short intervals, we recognize single make and break shocks and rapidly repeated shocks. The latter form the so-called quickly interrupted or "tetanic" current. It will be noted that the induced current is independent of the primary current, and Fig. 7. — Non-polarizable Electrodes. M, Muscle or nerve; C, cotton or camel's-hair brush; S, solution of zinc sulphate; Z, amalgamated zinc. develops only on the make and break of the primary current. In be- tween these two points no induction takes place, although the primary current continues to flow. 5. The Induction Coil.— The apparatus by means of which the induced current is obtained is known as an inductorium. It consists of about 130 coils of insulated copper wire of medium thickness, the terminals of which are connected with a key and the two elements of a battery. These connections constitute the primary circuit. The core of the primary coil is filled with a bundle of iron wire coated with shellac. A second spiral consisting of about 6000 coils of insulated copper wire of a thickness of 6.1 mm. is adjusted around the primary coil in such a way that it may be moved nearer to or farther away from the primary. The two ends of the secondary wire are fastened to 30 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY binding-posts which, in turn, may be connected with the stimulating electrodes. These connections constitute the secondary circuit of the inductorium. As has been stated above, the making and breaking of the primary current gives rise momentarily to an induced current in the secondary coil. A rapid interruption of the primary current may be effected by closing and opening the key in quick succession with the hand. A #-<.V'w^-'WV* > K Fig. 8. — The Inductobixjm. /, Primary circuit and coil; //, secondary coil and circuit; K, key; j, automatic inter- rupter; n, nerve. more convenient means, however, is afforded by such automatic inter- ruptors as have been described by Neef. The latter mechanism con- sists of a vibrating rod and magnet, both of which are attached to the end of the inductorium. A glance at Fig. 10 will show that the current from the battery (A) is led into pillar B as far as the platinum contact D upon the vibrator V. If the latter is in contact with the end of the Fig. 9. — The Inductorium. {Harvard Apparatus Co.) wire of the primary coil at D, the current will traverse this spiral {PC) and return to pillar F and the battery by way of the double spiral E. But as the current passes through spirals E their iron cores are mag- netized and attract the iron plate H of the vibrator F, thereby break- ing the contact at D. When the primary current is broken in this manner the spirals (E) are again demagnetized. This plate {H) being released, the vibrating rod moves upward and again makes contact MUSCLE AND NERVE 31 at D. 'At the moment when the priiiuuy current is made and broken an induced current is momentarily developed in the secondary coil. 6. Stimulation of Muscle and Nerve — The Condant Current. — Con- nect in scries two dry cells and a sunplc key and apply the ends of the wires leading away from them to the tongue. Make and break the current by closing and opening the key. When do you perceive the stimuli? Note that the make shock is the stronger of the two. Does the current stimulate while it continues to flow, i. e., between the make and break? Upon the basis that a stimulus arises in consequence of any extra- ordinary change in the environment, it may be said that an electric cur- FiG. 10. — The Automatic Interrupter of the Inductorium (Neef's). A, Entrance of current from battery into post B and vibrator V as far as D. In accordance with the position of the vibrating plate, the current now flows either back to the battery C through post F or into the primary coil PC through D. In the latter case, the current first traverses magnet E before it can reach the battery by way of post F. rent stimulates only when its intensity is rapidly altered. Such altera- tions occur only on the make and on the break of the current, and hence, no stimulation is evoked in between these two points. Inasmuch as the full electric potential is thrown into the living substance on the make of the constant current, the latter reacts with greater amplitude at this time than later on (break), when it has been partially adapted to this stimulus. Single Induction Shocks. — Connect in series two dry cells, a simple key, and posts 1 and 2 of the inductorium. This connection does not include Neef's automatic interruptor, and hence, the current may be made and broken at intervals of varj-ing length. Make and break the 32 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY primary current. When do you perceive the stimuH? Which stimula- tion is the stronger, the making or the breaking induction shock? Annotation. — If the direction of the induced current is determined by means of a galvanometer, it will be found that the making shock is opposed to the primary- current, Avhile the breaking shock passes in the same direction as the primary cur- rent. Secondly, the make induction develops more slowly than the break induction, because the entering primary current must first overcome the self-induction in the primary coil before it can produce a similar effect in the secondary coil. As it passes from one tiu"n of the primary wire to another, an induced current is momentarily set up in the secondary coil which possesses a direction opposite to the primary. Its strength is thereby diminished. On the break, this impediment is not present, and hence, the induction in the secondary coil is enabled to reach its maximal value with much greater rapidity. Quickly Repeated Induction Shocks or Tetanic Current. — Connect in series two dry cells, a key, and posts 1 and 3 of the inductorium. This connection brings Neef s hammer into the circuit and allows us to make and break the primary current in rapid succession, thereby pro- ducing an entire series of inductions. Compare the stimulating value of the quickly interrupted or tetanic current with that of single induc- tion shocks. 7. Changes in the Strength of the Current. — Use single induction shocks. Push the secondary coil of the inductorium over the primary. Stimulate. Gradually increase the distance between the secondary and primary coils and repeat the stimulation. What difference do you no- tice? Explain. Annotation. — The strength of the induction shocks depends first of all upon the electromotive force of the primary current. Secondly, it is proportional to the separa- tion of the secondary coil from the primary, becoming the weaker the greater the distance between them. The strength of the induction current may be indicated approximately by giving the strength of the battery and the distance between the coils in centimeters. The latter may be read off directly from the scale inscribed upon the base of the inductorium. 8. Direct and Indirect Stimulation. — Suspend the leg of a frog from the clamp in the manner described previously (p. 23). Place the sciatic nerve upon the electrodes. Moisten the preparation repeatedly with normal saline to prevent its drying. Stimulate it first with the constant and then with the interrupted current. Do the results agree with those obtained by stimulating your tongue or finger? Hold the electrodes firmly against the body of the gastrocnemius muscle. Repeat the stimulation with the same strength of current and compare the effects of stimulating the muscle directly and indi- rectly through its nerve. Which is the more irritable tissue of the two, as betrayed by the threshold value of the current required to activate it? 9. Myography. — The registration of the contraction of muscle neces- sitates a means of holding the muscle, a writing lever, and a surface upon which the record may be made. The wi'iting lever is fastened to the stand below the muscle clamp. The tendo achillis of the gastroc- MUSCLE AND NEUVE 33 nemius is then cut across and tlic muscle peeled off from the bones of the leg. Next the hitter are cut across near the knee-joint and dis- carded, together with the foot. A thread is then tied around the end of the tendon and connected with the writing lever near its center of rotation. Below the tendon a slight weight is attached which is pre- vented from extending the muscle l)y an after-loading device. The electrodes are adjusted upon the uj)per part of the nms(;le (Fig. 11). The recording surface is formed by a sheet of glazed paper which has been firmly attached to the surface of the cylinder of a kymograph and has been covered with a thin layer of soot. The smoking of the drum is accomplished most conveniently })y suspending it in a smoking rack. The drum is then revolved at the rate of about once in every Fig. 11. — A Method Used to Register Muscul.\r Contr.\ction. St, Stand for holding of clamp C and writinp: lover WL. The muscle M is attached to the lever by means of a small hook and string. The lever carries weight W. The stimula- tion is effected through the electrodes, 5. The speed of the kymograph K may be varied by fan F. second, while a broad gas flame is held directly underneath with its outer yellow zone barely touching the paper. Smoke the paper from left to right, remaining in the same place until an even brown surface has been produced. Never cease rotating the drum while the flame is directed against the paper, and do not overheat the latter, otherwise a burned gray surface will be obtained. When properly smoked, the paper should possess a velvety, chocolate-brown color (Fig. 12). Replace the drum upon the rotating disk of the kymograph. Adjust the writing lever with the least possible friction upon the paper, and take care that it writes as a tangent upon a sphere and in a straight vertical line. The writing lever is provided with an after-loading device consisting, as a rule, of a screw-support by means of which the lever 3 34 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY may be kept in the horizontal position without putting an additional weight upon the resting muscle. Stimulate the muscle successively with the make and break shocks of a constant current, moving the drum each time by hand a distance of a few millimeters. Repeat with single induction shocks of medium strength. Allow the drum to revolve first slowly and then more rapidly, and repeat the stimulations. Obtain intermediate speeds of the drum by placing fans of different size upon the pivot of the starting gear. Observe the changes in the out- line of the myogram as the speed is increased. Fasten a tuning-fork, vibrat- ing one hundred times in a second, to a separate stand, and allow its beats to be registered below the " L^n Fig. 12. — Arrangement for Smoking the Paper. {Univ. of Penna. Lab. Outlines.) myogram. Stimulate the muscle with a quickly interrupted current (posts 1 and 3) for a period of five seconds, and record its contrac- tion upon a slowly revolving drum. Never permit the tracing to extend across the line where the paper has been glued together. 10. Fixation of the Records. — Write your name upon the paper and label the different tracings. Remove the drum from the stand, and hold it in your left hand with the tip of the thumb upon the edge of the paper. Insert the tip of a small forceps underneath the paper near the line where its ends have been glued together. Break the paper in a straight line. Hold the paper firmly between your hands and draw it with the blackened surface turned upward through a solution of shellac in alcohol. Suspend the paper in the frame provided for this purpose and allow it to dry. Cut out the different tracings and paste them in your note-book in an orderly manner. 11. Isotonic and Isometric Myograms. — If a muscle is made to con- tract against a writing lever and a slight load, a very small portion of its energy will be used up in overcoming this resistance. By far the greatest amount of its energy, however, will be set free to yield visible mechanical energy, heat, and a small fraction of electricity. If the muscle is now attached near the fulcrum of the lever, while the end near the writing point is prevented from moving by a counter-force, the shortening of its fibers will be i-educed to a minimum and practically no mechanical energy will be liberated. A relatively much larger amount of the total energy will thereby be converted into heat. The former arrangement is characterized as isotonic and the latter as isometric. LESSON III MUSCLE AND NERVE (Continued) IRRITABILITY, CONDUCTIVITY. AND ELASTICITY OF MUSCLE. THE POWER OF MUSCLE TISSUE IN RELATION TO THE CROSS-SECTION AND ARRANGEMENT OF ITS FIBERS 1. Independent Irritability of Muscle. — Pith a frog and destroy its brain without losing any blootl. Immediately close the opening with the pointed end of a match. Make a median in- cision along the posterior surface of the left thigh. Isolate the sciatic nerve carefuUj^ without injur- ing the femoral vessels. Tie a ligature around the thigh, exclusive of the sciatic nerve. With a large hypodermic needle inject a few drops of curare under the skin of the back. Be sure that the solu- tion does not escape through the incision in the thigh. After its absorption the curare circulates and is carried to all the tissues except those of the ligated leg. When a complete motor paral\"sis has been es- tablished in about fifteen to twenty minutes ex- pose both sciatic nerves and place them in loose ligatures. Also expose both gastrocnemii muscles by cutting an oval window in the skin over each. Use weak induction shocks and stimulate the sciatic nerve on the side of the ligature (1) as well as on the normal side (2), In the same way stimulate both gastrocnemii muscles (3 and 4). The follow- ing results will be obtained: (1) positive, (2) nega- tive, (3) positive, (4) positive. Annotation. — A piece of solid curare (wurare or urare) is pulverized in a mortar and extracted with a solution of 0.7 per cent, sodium chlorid until dark in color. Its strength cannot be standardized, but must be determined by the physiologic result. Do not filter, but inject as it is. Test the current by applying the electrodes directly to the gastrocnemius muscle. Use a strength of ciu"rent just sufficient to cause a well-marked contraction. If a strong current is used, the paralysis must be more com- plete, which rcfjuires a larger amount of curare. Curare paralyzes the motor plates in the muscle, and hence muscle (4) cannot be activated tlirough its nerve, while muscle (3) can be. Both sciatic nerves conduct normally, as can be shown Ijy attacliing the poles of a galvanometer to them. In fact, in many instances tlie stimulation of the nerve on the normal side (4) jjroduces a contraction of the gastrocnemius on the side of the ligature. The elicitation of 35 iTY OF Muscle. A , Dorsal lymph sac into which curare is injected; L, liga- ture upon left thigh. The stimulation of the sciatic nerve at 1 is then effective, but is ineffective at 2. The gastrocnemii muscles, when stimulated di- rectly at 3 and 4, give a contraction. 36 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY this reflex proves that the impulses set up in nerve 2 are conveyed into the spinal cord and from here outward to the muscles of the non-curarized left leg. On stim- ulating either gastrocnemius muscle (3 and 4) a reaction is obtained. This proves that the curare establishes a block between the lierve-fibers and the substance of the muscle, /. c, it paralyzes the motor plates. Secondly, it may be concluded that a muscle which has been isolated in this manner from the central nervous system is still irritable and contractile. Consequently, muscle substance so isolated is capable of acting independently of the nervous tissue. 2. Irritability and Conductivity. — In order to distinguish between these two properties of living substance we usually make use of a nerve- muscle preparation which is placed upon a plate, while its nerve is drawn through the openings of a small gas chamber. Pieces of moistened filter-paper are placed flat across these openings. Inside the chamber the nerve rests upon a pair of needle elec- trodes {A), and outside the chamber upon a pair of ordinary platinum electrodes {B). Both pair of elec- trodes are connected with the end-cups of a pole changer. The side cups of the latter are then united with the secondary coil of an inductorium. The inlet tube of the gas chamber is made to communicate with a generator bottle containing pieces of marble. Stimulate successively at A and B with induction shocks of moderate strength. A positive result will be obtained in each case provided the nerve has not been injured. Pour a small quantity of 20 per cent. HCl upon the marble. Repeat the stimulations as soon as the CO2 has begun to pass over into the chamber. It will be found that the stimulation at A is now less effective than before or abolished altogether. Disconnect the generator and blow fresh air into the chamber. Stimulate again. Both excitations now give positive results. Fig. 14.— Gas Chamber for De- termining THE Ir- ritability AND Conductivity of Nerve. {Harvard Apparatus Co.) Annotation. — The carbon dioxid destroys first the irritability and later on also the conductivity. As this gas enters the chamber containing the nerve it diminishes the irritability of the latter (^1), but permits its conductivity to remain practically normal (5). Consequently, these properties of nerve are independent of one another. Pour a few drops of alcohol through the inlet tube of the gas chamber, but in such a way that it does not come in contact with the nerve. Stimulate at A as well as at B. It is to be noted that the stimulation at B now remains ineffective, because the vapors of alcohol have de- stroyed the conductile power of the nerve-fibers, while they have diminished their irrital^ility in a much slighter degree. 3. Extensibility of Muscle. — Use the same preparation; cut off the nerve near the muscle, and fasten the femur in the clamp. Attach the tendo achillis to the writing lever and adjust a large scale pan under- neath the tendon. Release the after-loading appliance so that the MUSCLE AND NERVE 37 Icvor may record down-strokes. Record the zero lino oi- abscissa. Put ten weifjhts of 10 firanis each successively into the scale pan, recording each time the extension which the nuisde suffers. Carefully I'cmove the weights one by one, allowing the muscle to register its curve of deten- tion. Does thp lever return to the abscissa? Obtain a curve of elasticity from a rubber band under similar con- ditions. Coqipare the results. Adjust the stimulating electrodes upon the upper part of the nmscle. Obtain a curve of elasticity from this muscle while it is being stimulated with a tetanic current of moderate strength. What differences do you detect i)etween this curve and that obtained under ordinary conditions? Explain. JLOK / Fig. 15. — Extensibility and Elasticity. A, Rubber band, and B, Ktistrooncmius muscle of frog successively loaded with 10- grani weights. The st>cond curve shows a decreasing extension for equal increments, hence, the line joining the ends of the ordinates is curved. Annotation. — A rubber band is perfectly elastic, ?'. f., it recoils until its abscissa has been reached, ]irovi(ied it has not been extended unduly. The same holds true of muscles in .situ; in fact, they are well protected against all excessive degrees of extension. Outside the body muscles are imperfectly elastic. After their con- stituent fibers have been stretched they cannot resume their original shape. A fatigued muscle (tetanized) can be extended much more easily and recoils with much greater difficulty. 4. Measurement of Muscular Power. — Prepare a gastrocnemius muscle of a recently killed frog and fasten the femur in the clamp. Connect its tendon with the writing lever. Adjust the after-loading mechanism so that the lever remains horizontal. Attach weights of 100 grams each to the lever until the muscle is no longer able to hft them when stimulated with a tetanic current of moderate strength and brief duration. Determine the maximal load lifted and also the weight of the muscle. Compute the power per gram of muscle substance. 5. Comparison Between Compact and Long Muscles. — Prepare the sartorius muscle of the opposite leg of the same frog. It is situated upon the inner aspect of the thigh and extends between the ilium and the tibia. Raise its tendon at the tibia and tie a fine silk thread around it. Separate the entire muscle from the fascia connecting it with other muscles and cut its other end, leaving the ilium attached. Determine the maximal load which this muscle is capable of lifting under condi- tions identical with those just described. Which muscle develops 38 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY more power, the long or the short and compact? does the latter possess over the former? What advantage Annotation. — Short compact muscles, such as the gastrocnemius, are meant to lift hea\y weights, while long, slender muscles, such as the sartorius, excel in height of contraction rather than in actual force. 6. Relation of Force to Cross-section. — Prepare the other gastroc- nemius muscle of the same animal. Fasten the one already used and this one side by side in the clamp and connect their tendons jointly with the writing lever. Determine the maximal load lifted by them in the manner described previously. Quickly disconnect and arrange these muscles tandem by uniting the tendon of one to the point of at- tachment of the other by means of a short wire. Adjust one wire from 'J ;m ;l:(|(iill(l llllhliiill =l# k' — • < W ~\ u ~ % 1 1( / ^ "" '^W' »- )[- - w F I ^ w Fig. 16. — Schema to Show that Contracting Muscle Does Not Change its Volume. M, Meniscus of saline solution; iS, electrodes through which muscle in receptacle is stimulated. I^ W Fig. 17. — Different Systems of Levers. F, Fulcrum; P, power; W, weight. the secondary coil of the inductorium to the body of the upper muscle and the other to the body of the lower muscle. Stimulate with the same strength of current used before, and determine the maximal load lifted by them when arranged in this way instead of side by side. 7. Effect of Contraction Upon the Volume of the Muscle. — Place one of these gastrocnemii muscles in the glass receptacle provided for this purpose. Be sure that its ends are firmly attached to the hooks projecting from the bottom and top of this receptacle. Fill the recepta- cle with boiled saline solution; close it, and adjust the capillary tube so that the "meniscus," indicating the level of the liquid, can be clearly seen. Connect the ends of the hooks with the secondary coil of an inductorium. Stimulate with single induction shocks, and note whether or no a decided change results in the position of the meniscus when the muscle contracts (Fig. 16). MUSCLE AND NERVE 39 Annotation. — Since tlic coiitractiiiK iiiusclt' does not iiitereliaiijje material with the inediuin, but nierely sliifts its substance, its volume is not altered. The men- iscus remains stationary, provided all the air has been driven out of the saline by boiling. 8. Manner of Attachment of the Muscles to the Bones. — DcternHiie the position of tiie t'lilciuin, \v(M}i;ht and power in tli(> cases of the biceps in fiexing the forearm, ti'iceps in extending the forearm, muscles upon the ventral aspect of the neck in moving the head, gastrocnemius in raising the body on tiptoe, tibialis anticus in raising the body on the heel, and the masseter in raising the jaw (Fig. 17). 9. Center of Gravity.— W it li chalk outline the feet of a person when standing erect. Aijproximatel}' determine by means of a ruler, held vertical, the position of his center of gravity. Attach a heavy load first to the front and then to the back of his body, and note the manner and degree in which the body is shifted to support the center of gravity. What use may l)e made of the legs and arms in gaining additional sup- port? Draw a diagram illustrating the progression of the center of gravity during the act of walking. LESSON IV .. MUSCLE AND NERVE (Continued) SINGLE CONTRACTION, SUMMATION AND FUSION OF CONTRACTIONS. TETANUS. INFLUENCE OF CHANGES IN THE STRENGTH OF THE STIMULUS AND LOAD OF THE MUSCLE 1. Single Contraction or "Twitch." — Attach a gastrocnemius muscle to the clamp and the writing lever. Place an electromagnetic signal directly below the writing lever, so that their points come to lie close together and precisely in the same vertical line (ordinate). Fasten a scale pan underneath the writing lever, but in such a way that it cannot interfere with the movement of the lever. Connect the signal in series with the cells and posts 1 and 2 of the inductorium. Adjust the sec- ondary coil to obtain induction shocks of medium strength. Fasten a tuning-fork to a separate stand which is placed to the left of the kymo- graph, so that the pointer of the fork vibrates against the rotation of Fig. 18. — Electromagnetic Signal. (Univ. of Pcnna. Lah. Oullines.) the drum. Raise the drum of the kymograph from its friction-surface l)y properly adjusting the screw in the top of the rod. Let the tuning-fork register its vibrations (y^o sec.) directly below the record of the signal. With your left hand then spin the drum once around its axis, and with your right hand close and open the key of the primary circuit. The speed of the drum should be such that the circuit may be made and broken conveniently during a single rotation of the drum. Repeat this experiment a number of times. Place a ruler vertically against the kymograph and draw perpendiculars through the: 41 42 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY (a) Moment of stimulation as indicated by the signal, (6) Point at which the muscle just begins to shorten, (c) Point at which the muscle shows its greatest degree of short- ening, and (d) Point at which the writing lever again reaches the abscissa. Fig. 19. — A Muscle Twitch. M, Make shock recorded by magnetic signal connected with primary circuit. Time in xJij sec; L, latent period; C, period of contraction; R, period of relaxation. Determine the duration of: (a) The latent period, (6) the period of contraction, and (c) the period of relaxation. Note that the muscle does not relax properly if the stimulus is too strong, and that the length of the curve increases after a time, owing to fatigue. 2. Summation of Contractions. — Remove the tuning-fork. Use a rapid speed of drum and again stimulate the muscle with a make and Fig. 20. — Summation of Contractions. M and B, Make and break shocks indicated by an electromagnetic signal. Time ui i^Tj sec. As the break contraction occurs during the period of relaxation of the make contraction, it is added to the first. break shock, but in such a manner that the break stimulus strikes the muscle during its period of relaxation. A second contraction then re- sults which is added to the first, thereby rendering it higher than the first. 3. Fusion of Contractions.^Reduce the speed of the drum. Repeat the previous experiment, gradually increasing the rate of stimulation until the contractions resulting from the separate stimuli are partially MUSCLE AND NERVE 43 and completely fused. This fusion of single contractions eventually gives rise to a tetanus. 4. Compound Contraction or "Tetanus."— Connect in series two dry cells, a simple key, and posts 1 and 3 of the inductorium. Change the gears of the kymograph so as to obtain the slowest possible speed of rotation. Use a moderate strength of current and stinuilate the Fig. 21. — Fusion and Tet.\nus. 5, Summation; F, fusion; T, tetanus. Time in seconds. The individual make and break shocks are repeated so quickly that a continuous contraction is obtained. muscle during a period of ten seconds. Compare this curve with the one obtained previously. Since the tetanic contraction is the result of the summation and fusion of simple twitches, it is much higher and longer than a twitch. If long continued, the height of the curve de- clines slowly, owing to fatigue. Fig. 22. — Tetanic Contraction. Recorded by means of Neef's automatic interrupter. Time in seconds. The decline of the curve is an indication of fatigue. 5. Relation of the Strength of Stunulus to the Height of Contraction. — Prepare a gastrocnemius muscle and fasten the femur in the clamp. Connect the tendon with the writing lever, and put a 10-gram weight into the scale pan. Record the abscissa. Retain the writing lever in this line by means of the after-loading screw. Apply the electrodes firmly to the upper part of the muscle. Push the secondary coil of the inductorium over the primary. Record the make contraction, keeping 44 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY the fingers of your right hand firmly upon the key. When the lever has again assumed the horizontal position, turn the drum with your left hand about 2 mm. to the left, and record the break contraction. Move the secondary coil outward for a distance of 1 cm. Turn the drum 5 mm. to the left. Again make and break the current as described. Repeat this experiment, constantly increasing the distance between the coils, 1 cm. at a time, until the stimuli cease being effective. In closing and opening the key, hold the handle firmly, so that a steady contact is obtained each time. Determine the threshold values of the make and break shocks in terms of "distance of coils" and "deviation of the secondary coil." Note that the maximal reactions are obtained at about 1 or 2 cm. distance of coils, and not when the coils are fully approximated. Beginning at this point the height of the contractions decreases gradually to zero, the make contractions disappearing sooner than the break contractions. Explain this difference upon the basis of the results of Lesson II. jLl in I 2, 3 t S" 6 7 8 9 to II /£, »5 I'^ '5 FiG. 23. — Successive Make and Break Contractions. The strength of the current is gradually diminished by more widely separating the secondary from the primary coil. The figures indicate this separation in centimeters of distance. M, Threshold of make; B, threshold of break. 6. Summation of Subminimal Stimuli. — With induction shocks which just fail to evoke a visible contraction, stimulate the muscle at intervals of one second. Repeat the stimulation at a much faster rate. Do the subminimal stimuli eventually become supraminimal? Annotation. — Two \aews may be held, namely: (a) that the individual electric potentials are added to one another and finally produce a potential of sufficient magnitude to stimulate, and (h) that the successive subminimal stimuli progressively increase the irritability of the muscle tissue until it eventually reacts to a stimulus which, when applied singly, does not activate it. The first view, therefore, advo- cates a summation of stimuli, and the second, a summation of protoplasmic exci- tability. 7. Relation of the Amount of the Load to the Height of Contrac- tion.— Prepare a fresh muscle and arrange the apparatus for stimulation with moderate break shocks. Attach a scale pan to the writing lever and record the abscissa. Keep the lever in this line by means of the after- loading device. Record a make and break contraction upon the stationary drum. In this case it is permissible to record both in the same ordi- nate, because the break contraction is higher than the make contrac- tion, but do not break the circuit too soon after the make, otherwise MUSCLE AND NERVE 45 you will ol)tain ;i simiinalioii. Load the muscle with a weight of 10 grams, and move the (hum a distance of about o mm. to the left. Re- peat the stinuilation. Continue to load the nmscle successively with O to zo io W SO to •)o 80 90 /oo Fig. 24. — Influence of Load. This muscle has been successively loaded with lO-grain weights. 10-gram weights until it ceases to show an appreciable contraction. Observe the general outline of the curve obtained, and formulate a general rule regarding the height of the contraction and the load. Fig. 25. — Diagram of Work-adder. A, Wheel which is turned by muscle M in direction of arrows. It i?' held in place by brake B. Each contraction of muscle raises weight W. 8. Muscular Work. — Obtain in millimeters the values for: L, the total length of the wiiting lever, /, the distance from its axis to the point of attachment of the muscle, and H, the height of each contraction. In accordance with the formula, L : H :: I : h, compute the height to which the weight has been lifted during each contraction (h). The 46 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY work (W) performed by the muscle each time equals the weight (w) multiplied by the height to which it has been lifted (h). The work of the muscle is expressed in gram-millimeters. 9. Addition of Work.^ — In order to determine the amount of work accomplished by a muscle in a given period of time we make use of an instrument which is known as a work-adder (Fick). Adjust this instrument upon the edge of the table, allowing the weight (10 grams) suspended from its pulley to touch the floor. Fasten the femur of a gastrocnemius preparation in the clamp and attach its tendon to the lever of the work-adder. Apply the electrodes to the upper part of the muscle, and stimulate it at the rate of once in every second during a period of thirty seconds. The individual make and break shocks may be put in successively, i. e., it is not necessary to short-circuit the makes. Compute the work performed during this period by multi- plying the weight by the height to which it has been lifted (W = wh). Annotation. — In short-circuiting the make, the cross-bar attached to the rods of the secondary coil is moved downward into its position of closure. The current is then made, but cannot reach the muscle because it selects the route of least re- sistance across the bar. Now open this bridge and break the circuit. The break shock may be short-circuited by simply closing the bridge directly after the make has been allowed to enter the muscle. LESSON V MUSCLE AND NERVE (Continued) INFLUENCE OF TEMPERATURE. CHEMICALS. AND FATIGUE UPON THE CONTRACTION OF MUSCLE 1. The Influence of Changes in Temperature on Contraction.— Fill the outer space of the muscle chanil^er with cracked ice and fasten it in the stand. Suspend a gastrocnemius muscle from the hook upon the inner surface of its cover and connect the tendo achillis by means of a long thread with a writing lever placed directly underneath the floor of Fig. 26. — The Musci^e Warmer. An apparatus for studying the influence of temperature on muscular contraction. {Porter.) the chamber. Fasten the ends of the wires from the secondary coil in the upper part of the muscle, and arrange the inductorium for stimula- tion with single induction shocks. Suspend a thermometer next to the muscle in the inner compartment, but in such a way that its bulb does not come in contact with the metal. When the temperature has reached a point near zero, record a single break contraction upon a rapidly revolving drum. Be sure to break 47 48 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY directly behind the hne where the edges of the paper have been ghied together. Without removing the writing lever from the drum, revolve the latter to this line. By means of an alcohol lamp gradually raise the temperature in the muscle chamber to 5° C. Make the current. Allow the drum to revolve, and when the writing lever has passed the first contraction, open the circuit. Again rotate the drum to the aforesaid Hne; adjust the writing lever in the abscissa, and heat to 10° C. Make the current and allow the drum to revolve, again break- ing the circuit directly after the second contraction. Repeat this pro- cedure at intervals of 5 degrees up to 40° C. Contrast the sluggish contractions obtained at low temperatures with the rapid twitches obtained at higher temperatures. Is the increase in the height and decrease in the length of the individual contractions uniform? Increase the temperature still further, and revolve the drum by hand a Kttle at a time. At about 43° C. the frog's gastrocnemius enters the state of heat-rigor, and finally shortens maximally. Remove the Fig. 27. — Effect of Changes in Temperature on Muscular Contraction. The temperature was raised 5 degrees each time. muscle from the chamber and examine its texture and appearance. Stimulate it and ascertain whether it contracts. Annotation. — By attaching an automatic key to the kymograph the cm-rent may be broken precisely at the same moment. This permits the individual con- tractions to become superimposed (Fig. 27). 2. Influence of Chemicals on Contraction. — Inject a few drops of a 1 per cent, solution of veratrin sulphate into the dorsal lymph-sac of a frog. Wait fifteen minutes. Prepare the gastrocnemius muscle in the usual manner, and fasten the femur in the clamp. Attach its tendon to the writing lever, and arrange the inductorium for stimula- tion with single induction shocks of moderate strength. Record several contractions upon a rapidly revolving drum. Study the character of the contraction of the veratrinized muscle. Wherein does it differ from the contraction of normal muscle? Also note that the veratrin MUSCLE AND NERVE 49 reactions commonly alternate with perfectly normal ones. The reason for this is not known. Heat neutralizes the influence of venitrin. Annotation. — In order to ('conoinizx', the other ^astrorneiiiius niiisele of the frog used for the precedinj^ experniient may l)e iininersed for a few moments in a 1 i)er rent, sohitioii of veratrin. If it is then adjusted in the recording apparatus, it will give eharacteristic veratrin rontraetions. 'Is'sic . . . • Fig. 28. — The Effect of Veratrin on Muscular Contraction. 3. The Effect of Excessive Stimulation on Contraction. Fatigue. — Attach a fresh gastrocnemius muscle to the recording apparatus. Put a 10-gram weight in the scale pan. Ai-range the electric apparatus for stimulation with single induction shocks of moderate strength. Make the current. Allow the drum to revolve at a rapid rate and break the current after the writing point has passed the line where the papei- has been glued together. Turn the drum by hand to the end of the paper without removing the writing lever. Now stimulate the muscle at brief intervals with twenty-five make and break shocks. After the twenty- sixth make contraction hold the bridge of the key down. Allow the •r Fig. 29. — Fatigue of Muscle. A gastrocnemius muscle of the frog stimulated successively 150 times. The 1st, aOth, 100th, and 150th contractions are recorded. drum to revolve and record the twenty-sixth break contraction directly after the first. Again stimulate the muscle twenty-five times near the Une where the paper has been pasted together, and record the fifty- first break contraction as described. Repeat this procedure, recording the contractions at these intervals until the muscle ceases to lift the lever. Compare the different curves with one another, noting their relative heights and lengths. Wherein does fatigue betray itself? Wait five minutes and stimulate the muscle again. Does it regain its power of contraction? Compare its behavior with that of a normal muscle after excessive exercise. 50 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY Annotation. — If this muscle possesses a high degree of irritabiUty, increase the number of the contractions between the successive records. Since a veiy responsive muscle may contract as many as 750 times against a weight of 20 grams before it is fatigued, the differences between the successive contractions might not be suf- ficiently evident unless some such procedm-e is followed to hasten the onset of fatigue. Naturally, fatigue may also be brought on more quickly by increasing the weight lifted by the muscle. As has been stated above, the writing lever should not be removed from the smoked paper, because this alters the friction and interferes with the steady decline and lengthening of the successive curves. Use the other gastrocnemius muscle of the same frog and attach it to the recording apparatus. Arrange the electric apparatus for stimula- tion with a quickly interrupted current (posts 1 and 3 of the induc- torium). Upon a slowly revolving drum record a tetanic contraction lasting twenty seconds. Directly underneath record a second contrac- tion of equal duration, and underneath this one, a third and fourth, until the muscle has been fatigued. ' LESSON VI MUSCLE AND NERVE (Continued) CONTRACTION OF HUMAN MUSCLE. INFLUENCE OF BLOOD-SUPPLY. SMOOTH MUSCLE 1. Contraction of Human Muscle. — Adjust your right foroarin in the holder of the crgogniph and place the middle finger in the sling supporting a weight of 2 to 3 kilos. Attach a pointer to the latter, permit ling it to rest against the paper of a kymograph. Make several voluntary contractions upon a rapidly revolving drum and above the record of a tuning-fork. Estimate the amount of work accomplished each time. Fig. 30. — Mosso's Ergograph. C is the carriage moving to and fro on runners by means of the cord d, which passes from the carriage to a holder attached to the hast two phalanges of the middle finger (the adjoining fingers are held in place by clamps); p, the writing point of the carriage, c, which makes the record of its movements on the kymographion; w, the weight to be lifted. {Howell.) Use a very slow drum. Flex the middle finger and retain it in this position until the end of the paper has been reached (tetanic contrac- tion). Note the oscillations and resulting fatigue. Use a very slow drum. Flex the middle finger at a definite rate, say, once in every second, until fatigue has resulted. Allow the speed of rotation to be indicated by a chronograph beating at intervals of two seconds. Annototion. — If Mosso's ergograph is not available, use a spring ergograph which consists of a horizontal lever attached to a metal upright. The fingers of the right hand are securely fastened in a liolder, while the index-finger of the same hand is abducted against the lever. Isotonic contractions are obtained if the rod resting 51 52 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY upon the index-finger and connecting the latter with the lever is moved far out toward the writing point. Isometric effects result if the vertical rod is adjusted near the metal support of the lever (Fig. 31). 2. Dynamometer. — Place a dynamometer in your right hand and contract the muscles against its spring. How great a force can 5^ou exert? Repeat with the left hand. Compare. 3. Ergographic Record of the Frog's Gastrocnemius. — Procure a metronome and insert it in the primary circuit of the inductorium. Adjust it to yield one stimulus in every second. Pith a frog and pre- pare a gastrocnemius muscle. Attach it to the writing lever in the usual manner. Allow the drum of the kymograph to revolve at a slow rate, and register the successive contractions of the muscle until fatigue Fig. 31. — Speing Ergogeaph. (^Harvard Apparatus Co.) has set in. How many contractions have been obtained and during how long a period? 4. The Influence of the Blood-supply Upon Muscular Contraction. — Procure a metronome and insert it in the primary circuit of the induc- torium. Adjust this instrument to stimulate once in every second. Pith a frog and block the opening with a pointed piece of match so that no blood is lost. Fasten the frog upon a narrow board of cork raised to the height of the upper margin of the drum of the kymograph. Isolate the femoral blood-vessels on one side and ligate them. Make an incision through the skin of the ankle and separate the tendo achillis from the bone. Attach a silk thread to the tendon and connect it across a pulley wheel with a writing lever adjusted upon the paper of the kymograph underneath the edge of the cork board. Isolate the oppo- site tendo achillis in the same way, and connect it with a second writ- MUSCLE AND NERVE 53 ing lever phicetl in the same (jidiiuite below the fiist. I'ull uixjii the strings to ascertain whether these levers interfere with one another. Attach a weight of 10 grams to (>ach. Make a small opening in the skin over the upper part of each gaslrociuMnius muscle, Fasten the wires from the secondary coil of the inductorium near the knee-joint — one on each side. Then complete the circuit by uniting the gastrocneniii muscles by means of a short piece of flexible wire. Allow the (h'um loo; the precise position and character of these absorption bantls. Fig. 47. — Spectroscope. P, Glass prism; A, collimator tube, showing the slit, per cent.) give rise to a single band, near the I) line. Employ solutions of 0.1 to 0.0 per cent, and use a cell the inner width of which measures 1 cm. Stoke's reducing fluid consists of a solution of ferrous suli^hate, to which a little tartaric acid has l)een added. When used, add annnonia till its reaction becomes alkaline. Its color then changes from yellow to dark yellow. 77 78 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 2. Examination of Suspected Blood. — Dissolve a small quantity of the suspected blood in normal saline solution. Search for corpuscles and apply the hemin test. Dissolve a small portion of the same ma- terial in water or in a dilute solution of caustic soda or potash and make a spectroscopic examination as described in the preceding paragraphs. Annotation. — The student should at this time be shown the lytic and precipitin reactions of blood-sera. Since it often takes several weeks to sensitize an animal, these tests for blood cannot be performed by students individuall3^ 3. Hemin Crystals. — Place a drop of blood upon a glass slide and dry it slowly in the gas flame. Add a few crystals of sodium chlorid and a drop of glacial acetic acid. Cover and gently heat until bubbles of gas are given off. Hemin crystals appear as minute, dark brown, Fig. 48. — Diagram of Spectroscope. rhombic crystals which cannot well be confounded with the irregular colorless crystals frequently seen in preparations of this kind. 4. Blood Crystals. — Mix a drop of rat's blood on a slide with a drop of water. After about five to ten minutes crystals of oxyhemoglobin will be seen to form. 5. Chemical Tests for Blood. — Add a small quantity of blood to tincture of guaiacum. Add a little hydrogen peroxid to this mixture. The blue color ensuing is due to the iron-containing radical in hemo- globin. Repeat this test with blood which has been boiled. The same reaction results. Dilute a little blood until practically colorless. Add to it a few drops of benzidin dissolved in glacial acetic acid and a few drops of hydrogen peroxid. A blue color develops. Repeat this test with blood which has been boiled. The reaction is now less intense. LESSON XIII THE HEART REGISTRATION OF THE HEART-BEAT. REFRACTORY PERIOD. EXTRA- SYSTOLE. EXCISED HEART. ACTION OF STRIPS OF VENTRICULAR TISSUE 1. Normal Heart-beat. — Apply a lifiatiiro to the nock of an pthorizcfl turtle directly Ix'hiiid tiie occiput, and destroy the hrain by pithing. Saw through the lateral aspect of the ventral shield or plastron, and remove the latter by cutting through the soft parts connecting it with the internal structures. Keep close to the bone so as to avoid the large blood-vessels. Identify the different superficial organs and note the texture, extent, and mode of attachment of the pericardial sac. Incise the latter by a longitudinal cut and separate the apex of the heart by dividing the strong band of connective tissue which unites it with the frenum. This band should be preserved to serve later on as an attach- ment for the hook of the writing lever. Fig. 49. — ARR.\N-ci;.MEN-T for Registering the Contractions of the Frog's Heart. (Univ. of Missouri Lab. Outlines.) Identify the venae cavae, sinus venosus, the right and left auricle, and the ventricle with its conus and main arterial trunks (aortae). Note the color and shape of the ventricle on systole and diastole, and study the sequence of contraction of the different segments of the heart, viz., sinus, auricles, ventricle. Insert a small hook in the apical band and connect it with a writing lever. Counterpoise the latter sufficiently to place the ventricle under a slight tension. Be sure that the plate upon which the turtle is resting is placed vertically under the writing lever, so that the heart is drawn 80 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY upwaiTd. Allow the ventricle to register its cycles upon the smoked paper of a slowly revolving kymograph above the record of a chrono- graph beating once in every two seconds. What is the rate of the heart per minute? Register the auricular beats in the same manner after having previously inserted the hook in the wall of one of the auricles. Note that the rhythm is the same in the two records, and that the force of the contractions of the ventricle is much greater than that of the auricles. Annotatioti. — ^'el•y good records may also be obtained from the heart of a frog. The animal is pithed in the usual way and fastened to a board by means of wire clips. A median incision is then made through the skin over the sternum, and the episternum raised with a pair of forceps. The edges of the sternum are cut through and the bone removed in its entirety. The pericardium is then lifted up and divided, thus exposing the beating heart. The sinus ^■enosus of this heart is formed by the imion of the large inferior vena cava and the two smaller superior venae cavse. It is continuous with the right auricle and ventricle. The latter continues as the bulbus aortje, which gives origin to the two aortse. From the latter arise the pul- monary arteries which supply the lungs. From here the blood is returned to the left auricle, whence it is again forced into the ventricle. Fig. 50. — Record of the Contractions of the Frog's Heart. The time is registered in seconds. The registration may be effected in two ways, namely, by: (o) The Supporting^ Method.— A vertical rod of straw is fastened by means of a thin wire to the long arm of an ordinary writing lever. The joint between them should be very loose. The other end of this rod is made cup shaped by means of a piece of wax molded to fit the surface of the ventricle. When the latter contracts the lever is raised. Consequently, the systolic period is indicated by the up-stroke and the diastolic period bv the down-stroke of each wave. (h) The Su.fpcJhsion Method— A fine thread is attached to the end of the short arm of an ordinarv writing lever. It is connected by means of a small hook with the apex of the heart. The long arm of the writing lever is weighted sufficiently to place a slight degree of tension upon the heart. In this case the up-strokes of the record correspond to the systoles of the organ. If a spring le^■er is employed, the tendencv of which is to move upward, the string must be fastened to its long arm.. The contraction of the heart then pulls the lever dov.nward, whereas the steel sprmg attached to the lever pulls it upward as soon as the cardiac musculature becomes passive during diastole. 2. Effect of Temperature.— Allow the ventricle to register its cycles upon the paper of a slowly revolving kymograph. By means of a pipet allow a few di-ops of iced saline solution (5° to 10° C.) to drop upon the TMK UK ART 81 heart. Note the rechictioii in tlie rate and slowinp; of eacli indivkhial beat. After the heart has a^aiii resumed its normal rate and ampH- tude of contraetion hathe it in the same maimer with warmed sahne sohition (20° to 25° ('.). Note the increase in its rate, thie to a greater rapi(Uty of the inchvichial contractions. 3. Refractory Period. Extrasy stole. — Leave tlie heart in position, ])ut place its ventricular portion in the cup of a heart-holder. Adjust the writing lever upon its surface, and connect the binding-posts with Fig. 51. — The Heart-holder. (Porter.) the secondary coil of an inductorium. Arrange the electric apparatus for stimulation with single shocks, and insert a signal in the primary circuit. Place the writing point of the latter in the same ordinate with that of the heart lever. Allow the ventricle to register its cycles upon a drum revolving at a moderate speed. Stimulate at intervals first during the systolic and then during the diastolic period of the heart. Note that the former stimuli remain without effect, whereas the latter produce an extra contraction (extrasystole). While the musculature is in contraction it remains impervious to stimuli (refractory period). CP Fig. 52. — Stimulation of Frog's Heart During Diastole. S, Moment of stimulation; E, extra contraction: CP, compensatory pause. 4. The Transmission of the Wave of Excitation. — The wave of exci- tation, ordinarily started at the venous entrance of the heart, is trans- mitted in the turtle and frog over muscular connections and activates its different segments consecutivel}'. The transmission of this impulse may be interfered with by compressing these muscular bridges by means of a screw-clamp applied to the auriculo ventricular junction. By grad- ually tightening this screw a degree of compression may be established which will allow only some of these waves of excitation to reach the 82 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY ventricle. Not all of the auricular contractions will then be followed bj'' ventricular contractions. This constitutes the condition of partial heart-block. 5. The Excised Heart. — Raise the heart as a whole by the frenum, and divide the aortse and venae cavse. Place the excised organ in a watch-glass in some of its blood and cover it with another watch-glass. Count the number of its beats, and note that it becomes soft and flaccid during diastole and adjusts itself at this time to the surface upon which it rests. Apply a drop of warmed saline solution to the sinus. Note the increase in the rate of this segment, which, in turn, brings about a similar change in the other portions of the heart. 6. Isolated Segments of the Heart. — The fact that a heart when separated from the central nervous system continues to beat, shows that it is automatically active. Cut transversely across between the sinus venosus and the auricles. The sinus continues to beat, whereas the rest of the heart ceases to beat for a time. This proves that the auricles and ventricle are ordinarily activated by a wave of excitation derived from the sinus. After a time the severed portion of the heart develops a beat of its own and continues to contract rhythmically. Sever the ventricle from the auricles. It ceases to beat, but may be made to contract at any time by stimulating it, for example, by pricking it with the point of a scalpel. It usually executes several beats. Cut off the apex of the ventricle, but preserve its basal portion. The former remains quiescent, but reacts promptly to all stimuli. Since the apex is free from nervous elements, this experiment is usually cited to prove that the heart-beat is of myogenic origin. 7. All-or-none Law. — Suspend this preparation of the apical portion of the ventricle by means of two silk threads between the writing lever and the plate. Apply the hand-electrodes to it and stimulate it suc- cessively with single induction shocks of different strength. Do you observe a difference in the amplitude of its contractions? How does striated and non-striated muscle tissue behave under these circum- stances? Inquire into the reason for this difference. 8. Isolated Strips of Ventricle. — Fasten one pole of the quiescent basal portion of the ventricle to the hook of a weight resting upon the bottom of a beaker, and its upper pole to the hook and string of a writ- ing lever. Counterpoise, so that this preparation is under the least possible tension. Pour a solution of 0.7 per cent, sodium chlorid into the beaker until it fully covers this preparation. Wait until the latter shows continued activity (twenty to thirty minutes), and record suc- cessive series of contractions at intervals of ten minutes. When the contractions have weakened, add a few drops of a 1 per cent, solution of calcium chlorid to the saline. The calcium stimulates cardiac muscle (systole), and hence the individual contractions should again assume their former amplitude. In small doses potassium favors the relaxation of cardiac muscle, while in larger doses it brings about a continued diastole. To show this THE HEAHT 83 effect, it may suffice to add several drops of a 0.9 per cent, solution of potassium chlorid to the saline solution. As soon as the preparation has })ecome quiescent, immerse it in fresh saline .solution or in Ringer's fluid, which contains the aforesaid .salts in the following proportion: NaCl, 0.7 per cent.; KCl, 0.035 per cent.; CaCl-, 0.026 per cent. The rhythm will presently be restored. Annotation. — Witli some rare a turtle's heart may Ix- made to last throughout these experiments. It" it does not, use a frog's heart to (•om|)lete this series. The action of tlie salts may also be studied separately upon different hearts. The pre- ceding order, however, should be adhered to, owing to the possibility of saving material. Conduction Through the Ventricle. — Pith a frog and expose the heart. Destroy the continuity of the nerve-fibers in the ventricle by makinitating cuts across it — two cuts startinj^ from its left border and two from its right. Since the wave of contraction nevertheless descends over this zigzag strip, the wave of excitation must be propagated by the muscular elements. Separate the ventricle from the auricles by a transverse cut. Note that the latter continue to beat synchronou.sly with the sinus, while the former remains quiescent. Apply the hand-electrodes successively to the base and apex of this zigzag strip of ventricle. Observe that the wave of contraction can thus be made to travel from base to apex as well as in the reverse direction. LESSON XIV THE HEART (Continued > INHIBITION AND ACCELERATION OF THE SIMPLE HEART. ACTION OF NICOTIN. ATROPIN, AND MUSCARIN 1. Inhibition of the Heart. — Apply a ligature tijilitly to the neck of an etherized turtle and destro}' the brain by pithing. Remove the ventral shield or plastron and clip away the projecting angles of the shoulder-blades. Arrange the inductorium for stimulation with a tetanic current of medium strength. Hold the extended neck of the turtle in place and carefully isolate the vagus nerve on each side. Place each in a loose ligature. Open the pericardial sac and connect the apical band of connective tissue with the writing lever. Adjust the Fig. 53. — CotRSE of Vagus Xerve in Frog. (Stirling.) SM, Suhmentalis; Li', lung; I', vagus; GP, glossopharyngeal; HS, hypoglossal; L, larj-ngeal; PH, SH, GH, OH, petro-, sterno-, goiiio-, aud omohyoid; HG, hypoglossus; H, heart; BR, brachial plexus. writing point of a chronograph underneath the writing point of the lever. Raise the left vagus nerve and place it upon the electrodes. Having recorded a number of normal heart-beats, stinuilate the afore- said nerve. If the heart is not inhil)ited, increase the strength of the current, but not excessively, becau.'^e an electrolysis might then result which would destroy conduction permanently. Make a number of these records, stimulating each time for a few seconds. During what period of the cardiac cycle is the heart arrested? 8n 86 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY Study the character of the heart-beats occurring directly after the inhibition. They may be small at first and gradually become larger, or large at first, and slowly decrease to normal. No explanation can be given for this difference. r \ r lY\l\l 11 \i 11 \i innn, mm y 11 \l 11 11 Fig. 54. — Record of the Contractions of the Frog's Heart During Stimulation OF THE Vagus Nerve (Tension Lever). The time is given in seconds, the stimulation is indicated by the signaL Stimulate the right vagus nerve with the same strength of current. Do the nerves possess the same inhibitory power? They differ, but not always in the same manner, i. e., the left or the right nerve may be more powerful, but most generally the right. The same differences may be LAS Fig. 55. — Schema of the Sympathetic Nerve in the Frog. OC, Occiput; LAS, levator anguli scapulae; Sym, sympathetic; GP, glossopharyngeus ; V-S, vagosympathetic; G, ganglion of the vagus; Ao, aorta; SA, subclavian artery. (Stirling.) noted in the mammals. Occasionally a turtle will be found in which neither vagus possesses this function. Stimulate either vagus nerve for three or four minutes. Note that the heart "escapes" from the inhibition in a very short time, and sub- sequently continues to beat in spite of the stimulation. THK iiKAirr 87 Tighten the li{i;atiiie.s upon both vugi nerves. Apply a secuiid Ujiu- ture to each at a distance of 2 mm. from the first. Cut between them. Stiniuiate both centra! ends successively. Do you observe a chane;e in the character of the recoril now made? Stimulate both distal ends successively. Do you observe a difTerence between this record and that obtained previously with the intact nerve? Apply the electrodes transversely to the sino-auricular region of the heart. Stimulate after you have recorded a limited number of normal beats. Does the inhibition produced in this way differ from that previously obtained by stinnilatin^ the vagi nerves? Atniotdtion. — A very convenieiit way is to trcpliiiic the ventral shield of the turtle in tiie rejtion of the heart. This saves nuich lal)or and jjievents loss of Ijlood ami drying of the tissues. Moreover, if small pulley-wlieels are at the dis])osal of the students, the heart should he allowed to act in its normal horizontal jjosition, while the string is made to move across the pulley, placed ol)lic|uely helow the writing lever. Do not allow the heart to act under too great a tension and allow it to rest from time to time hy disconnecting the string. In cast' it should cease contracting properly, ap])ly a few dro])s of warmed saline solution to its surface. Arhythmias are not unconunon and may he remedied in just this way. 2. Action of Nicotin. — By means of a dropper apply a small quantity of a 0.2 per cent, solution of nicotin to the heart. After five minutes connect its apex with the writing lever and stimulate the vagus nerve. The heart is not inhibited. Sthnulate the sino-auricular region directly. The heart is inhibited. What is your conclusion regarding the action of nicotin? Annotation. — Nicotin is a nerve-cell poison affecting the neuron at the synapse. In this case it causes a hreak between the vagal terminals and the recipient cells of the inhibitor plexus (Remack's), situated in the region of the sino-auricular groove. Consequently, the iniiihitor impulses set up by stimulating the vagus can never reach the postganglionic path and effector. The .stimulation of the plexus itself remains eti"e('ial care not to divide the mannnary arteries. Institute artificial lespiration, adjusting the volume of air so as to give a normal degree of expansion to the lungs. Stop bleeding by torsion Fig. 56. — Marey's Tamboi r. a, Axis of lever; h, metal tray covered with rubber incnilirane, and coninmnicating by tube /with the cannula. and ligation of the vessels. Separate the walls of the thorax by means of a string drawn around the board. Identify the pericardium and large blood-vessels leaving and entering the heart. Insert the end of a small cannula thi'ough an opening in the peri- cardial .sac, and secure it by means of a hgatuie. Connect its free end by means of narrow rubber tubing with a recording tambour adjusted against the paper of a kymograph. The pericardial sac acts in this case as a plethysmograph and yields a tracing of the volumetric dif- ference's which the heart displays during its cycle. Detach the rubber tube from the rcH'ording drum and blow a small quantity of air into the pericardial sac. What influence does the increase in intrapericardial pressure exert upon the activity of the heart? Note that this pro- cedure produces dynamic conditions such as are found in pericarditis. (3pcn the pericardial sac widely and i-eflect the pericardium upwai'd. Note the character of the fiuid escaping through the incision. What is its function? Identify the different parts of the heart. Which side of 91 92 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY the heart is more full}^ exposed to the view when the chest is opened? Palpate with the tip of your index-finger the walls of the right and left ventricles, observing in each case the difference in the texture of the cardiac muscle on systole and diastole. Also note the much greater thickness of the left musculature. Observe that the two auricles con- tract practically simultaneously, and that their contraction begins near the orifice of the venae cavse. Likewise, note that the two ventricles contract together as soon as the auricular systole has been completed. Expose the superior and inferior cavse and observe their pulsations (venous pulse). Expose the aorta and pulmonary artery and study their pulsations (arterial pulse). Place the tip of your index-finger upon the surface of the left auricular appendix. Press downward. Do you feel the flaps of the mitral valve hitting against your finger? Repeat this observation on the opposite side. Blow a spray of albulin upon the heart to prevent its drying. Fig. 57. — Cardiometer. The heart is inserted through a perfora- tion in rubber membrane (R) into cavity of a hemLspheric plass capsule (C). The latter is connected with a recording tam- bour (T). Fig. 58. — Clamp for Producing Heart- block. {After Erlanger.) Discontinue the artificial respiration for a brief period of time until the heart has been markedly slowed. Again study the progress of the wave of contraction and note the gradual change in the color of the heart. Its venosity is most clearly betrayed by the left auricle, the color of which gradually changes from bright red to dark purple. Ex- plain this phenomenon. Resume artificial respiration. Allow a few drops of a slightly warmed saline solution to fall upon the heart. Note the increase in its frequency. Procure a small cardiac plethysmograph, usually consisting of a hemi- spheric capsule of glass the orifice of which has been closed with a rubber membrane. Incise the rubber membrane near its center, and push the ventricular portion of the heart through this opening into the cardiom- eter. Connect the tubular outlet of the latter with a recording drum THE HEART 93 and ajiain rogistor tho vohiniotric clianuos of tho lioart. Ofolude the veiui' cavce for a few luorncnt.s. Explain tho resuh. Witluhiiw the ventricles from the cardiometer and allow the heart to recuperate. If necessary, cover it for a time with cotton moistened with warmed saline solution. Af^ain record the volume-curve of the ventricles. Temporarily obstruct the arch of the aorta. lOxplain the result. Allow the heart to rest. 2. Heart-block. Fibrillation.— Procure a clamp such as is represented in Fiacli is ina(l(> ui) of a nuinl)or of cardiac variations. Does the tracinj^ show Traubc-Horin^ curves, which are rhythmic waves including several respiratory variations? Ascertain the height of the j:)ressurc. Aniiotdtidii. It is lu'st to establisl) a certain (leRroe of pressure in the manometer before the Ijlood is actually allowed to act aj;ainst tlie mercury. In a cat or dog we may expect to obtain a pressure efiuallinj; 120 to KIO mm. Hj;. Thus, if we estab- lish a pressure of UK) nun. H^;. beforeliand, only a small (pumtity of 1)1o

;, but not too tightly. Raise the arm. Note the distended condition of the veins upon the dorsal aspect of the hand. Select the point of confluency of two veins. With the tip of the index-finger of your left hand occlude one branch tlistally to this point. With the tip of the index-finger of your right hand brush along this vein in a direction from periphery to center, emptying the blood into the collecting vein. Observe that the vein so emptied does not fill again until you have removed the distal finger and have allowed a Fig. 70. — Record of the Carotid Blood-pressure Dirinc; Dyspxea (Dog). At L the tracheal tube was hold shut until the blood-pressure bepan to drop. certain quantity of blood to flow into it from its tributaries. More- over, while emptied a marked prominence is developed at its point of confluency with the larger vein, indicating the position of the valve guarding its central orifice. This experiment was employed by Harvey to prove the circulation of the blood. Examine a preparation of a segment of vein preservcfl in alcohol. 2. Blood-pressure. Influence of Dyspnea. — Anesthetize a mammal and maintain the anesthesia until it has l)een killed. Perform trache- otomy. Insert a cannula in the carotid artery and connect it with the mercury manometer. Record the blood-pressure upon a slowly revolv- 109 110 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY ing drum. Occlude the tracheal cannula with the tip of your finger. Observe that the respii'atory movements gradually assume a labored character and that the respiratory variations in blood-pressure are therebj^ rendered more conspicuous. The blood-pressure rises grad- ually. The frequency of the heart, which is increased at first, is soon lessened. The heart then assumes a markedly diastolic character and causes the blood-pressure to fall. Immediately remove your finger from the tracheal cannula and wait until normal hemodynamic conditions have again been established. What factors are involved in the initial rise in blood-pressure? 3. Effect of Amyl Nitrite. — Place a glass bead filled with amyl nitrite in a small glass bottle. Break it between the tongs of an artery forceps. Place the palm of your hand over the mouth of the bottle. Record the blood-pressure upon a slowly revolving drum. Allow the animal to inhale the amyl nitrite by holding the end of the rubber tube attached to the tracheal cannula in the bottle. Remove the tube from the bottle as soon as the blood-pressure begins to fall. Naturally, the Fig. 71. — Effect of Amyl Nitrite on Blood-pressure (Dog). pressure will continue to drop even after this time until the amyl nitrite, which has been absorbed from the inspiratory air, has been rendered inert. Subsequent to this point, however, it will rise slowly until normal conditions have again been estabhshed. Explain in detail the action of this agent. What are the hemodynamic conditions established during attacks of angina pectoris? What changes may be effected during these attacks by inhalations of amyl nitrite? Replace the clip upon the artery after each experiment. If coagula- tion has set in, flush out the tubing as well as the cannula with sodium carbonate solution. 4. Effect of Adrenalin. — Add 1 c.c. of adrenahn (solution 1 : 1000) to 10 c.c. of saline solution. Expose the right external jugular vein. Place a clip upon it centrally and insert a cannula distally to the clip (toward the heart). Fill the cannula with normal saline solution and connect it by means of a short piece of rubber tubing with a pipet containing the aforesaid solution of adrenalin. Fasten the pipet in a THE CIIiCULATION 111 stand obliquely ahov'O the vein. Keconl the hloofl-pressure. Release tiie clip slightly and allow 1 to 2 c.e. of the solution of achcnalin to enter the venous circulation. Make a mark upon the paper, indicating the moment when the injection was made. Determine the length of the latent period intervening between the injection and the rise in blood-picssuic. Account for this interval. Note the character of the react i fiii^ois of (ho lijihl hand. T'loso tho oxhaust valve and compress the nihher hull) rapidly to raise the pressure to ai)out 140 nun. Hjj;. In a youiifj; person possessint^ an (>lastie vascular system and in the sittinf; position, we would not expect to find a pressure higher than this. Consequently, the pressuie in the cuff overcomes at this time the internal picssure. The brachial artery is fully compressed and the radial pulse ohliterated. Now gradually deflate; until the radial pulse just barely makes itself felt. Read the pressure and deflate rap- idly. Be sure to compress the arm for only the shortest possible time. Repeat agafii after intervals until you have acquired this technic thor- oughly and are able to obtain correct results. This gives the systolic blood-pressure. (6) Auscultation. — Place the chest-piece of a stethoscope over the region of the bifurcation of the brachial artery directly below the lower edge of the cuff. Inflate rapidly as before, then deflate gradually. No sound is heard when the brachial artery is obstructed. At the very moment, however, when the arterial pressure just overcomes the out- side pressure a sound is produced indicative of the systolic gushes of blood through the constriction. Read the pressure, which, as has just been stated, is the systolic. Practice this method a number of times. Compare these results with those obtained previously by palpation. The estimation of the diastolic pressure may be attempted during the process of palpation by carefully noting the amplitude of the oscilla- tions of the mercury of the manometer. When the systolic pressure breaks through the constriction these fluctuations are small, but become much larger as the diastolic value is approached. Below this point their amplitude again decreases. A better way is to ascertain this value by the method of auscultation. Having determined the moment when the systolic sound just appears, continue to deflate slowly. The sound becomes louder; soon reaches a maximum, and then suddenly disappears. Read the pressure at this point. It indicates the diastoUc pressure. Deduct the value of the diastolic pressin'o from that of the systolic. This gives the pulse-pressure, which varies under ordinary conditions between 35 and 40 nun. Hg. 2. Effect of Posture. — Determine the systolic and diastolic pressures of the subject while resting horizontally upon the table with his head upon a pillow. Repeat this test after he has assumed the sitting posi- tion, and again after he has assumed the standing position. Tabulate the results and determine the pulse-pressure. Explain the results. What bearing do they possess upon the condition of the vascular sj'stem? Crampton has attempted to obtain an approximate estimate of the condition or vascular tone of a person bj^ balancing the increase in the heart rate with the increase or decrease in blood-pressure resulting on standing up. The range of the sj'stolic pressure has been found to be between -|-10 and — 10 mm. Hg, and the increase in the frequency of the heart between 0 and 44. By assigning equal percentages to these 128 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY the following; scale has .been constructed, in accordance with which the vascular tone may be expressed in percentages: Heart rate, Systolic blood-pressure, increase. , Increase . . Decrease . + 10 +8 +6 +4 +2 0 -2 -4 -6 -8 -10 Oto 4 100 95 90 85 80 75 70 65 60 55 50 5 to 8 95 90 85 80 75 70 65 60 55 50 45 9 to 12 90 85 80 75 70 65 60 55 50 45 40 13 to 16 85 80 75 70 65 60 55 50 45 40 35 17 to 20 80 75 70 65 60 55 50 45 40 35 30 21 to 24 75 70 65 60 55 50 45 40 35 30 25 25 to 28 70 65 60 55 50 45 40 35 30 25 20 29 to 32 65 60 55 50 45 40 35 30 25 20 15 33 to 36 60 55 50 45 40 35 30 25 20 15 10 37 to 40 55 50 45 40 35 30 25 20 15 10 5 41 to 44 50 45 40 35 30 25 20 15 10 5 0 Thus, a person who on standing up shows an increase in the cardiac rate of 10 beats, and an increase in the blood-pressure of 10 mm. Hg, would be in the condition A (95 per cent.). Barach calculates the energy-index in accordance with the following example : Pressure. Heart rate. Index. In systole 120 mm. Hg X 72 = 8.640 mm. Hg In diastole 70 mm. Hg x 72 = 5.040 mm. Hg In both 190 mm. Hg X 72 = 13.680 mm. Hg The highest energy-index in a still normal person has been found to lie close to 20,000 mm. Hg in a minute, and the lowest somewhere about 10,000. 3. The Effect of Exercise. — Determine the normal systolic blood- pressure and rate of the heart with the subject standing. Repeat these determinations immediately after the subject has made forty flexions and extensions of the arms or thirtj^ knee bendings in one minute. Re- peat one, two, three, four, and five minutes afterward. Construct a curve to show the course of the pressure and cardiac frequency. Determine the cardiac frequency and blood-pressure in a subject before and after he has made a stationary run lasting one-half minute. Determine the cardiac frequency and blood-pressure in a subject before and after he has ascended forty steps in the course of one minute. 4. Venous Pressure. — Hold the hand against thfe chest in the region of the heart. Note the degree of filling of the veins. Raise the hand slowly until the veins collapse. Determine the distance between this level and the level of the heart. It corresponds to the height of the column of blood supported by the heart. LESSON XXV THE CIRCULATION (Concluded) THE CHARACTER AND VELOCITY OF THE ARTERIAL AND VENOUS PULSATIONS. POLYGRAPHY 1. The Application of the Sphygmograph. — Determine the rate of the subject's licart l)y palpation of the radial pulse. How is the rate affected by the act of swallowinsi;? Study the construction of the sphyj2;mo^raph. It usually consists of a vibrating rod which acts in magnified form upon a recording lever. The end of the rod is equipped with an oval projection which is adjusted over the artery. Apply this instrument securely to the radial artery and record a number of normal sphygmographic curves. Study their character. Fig. 83. — The Dudgeon Sphygmograph in Position. (Howell.) Ask the subject to close his mouth and nostrils with the fingers of the free hand and exhale forcibly. Explain the result (Valsalva's experiment) . 2. Relation Between the Arterial Pulse and the Action of the Heart. — Obtain a sphygmographic record of the radial pulse in proper relation with a record of the apex-beat registered by means of a cardiograph. Note whether any extrasystoles are present. Allow a cardiograph and a sphygmograph (radial artery) to register their excursions in the same ordinate upon a rapidly rotating drum, above the record of a tuning-fork. Obtain the approximate distance between the ascending aorta and the radial artery, and ascertam the speed of the pulse- wave by comi:)uting the difference of the cardiac and radial impulses. 3. The Use of the Phlebograph. — Apply a metal or glass cup to the jugular fossa and connect it with a recording tambour. Also register 9 129 130 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY the time. Study the character of the phlebogram, and compare it with the curve of intra-auricular pressure. Under what conditions does the phlebogram become of special value? What changes would tricuspid regurgitation produce in the character of the tracing? Obtain a phlebogram in proper relation with a sphygmogram of the radial artery, or with a cardiogram. When would a record of this kind prove of special diagnostic value? L Fig. 84. — Pneumograph. (Harvard Apparatus Co.) Annotation. — As the name indicates, a jugular cup consists of a hemispheric capsule of metal or glass which is placed flat against the region of the central end of the external jugular vein. The pulsations of tlais blood-vessel are transmitted to a recording drum. 4. Relation Between the Cardiac and Respiratory Activities. — Ad- just a stethograph upon the chest of the subject and connect it with a recording tambour. Place a receiving cup over the region of the carotid artery and connect it with a recording drum arranged to register in the Fig. 85. — Marey's Pneumograph. (Verdin.) The instrument consists of a tambour (0, mounted on a flexible metal plate (p). By- means of the bands c and c the metal plate is tied to the chest. Any increase or decrease in the size of the chest will then affect the tambour by the lever arrangement shown in the figure. These changes in the tambour are transmitted through the tube r as pressure changes in the contained air to a second tambour (not shown in the figure) which records them upon a smoked drum. (Howell.) same vertical line as the former. Beneath these writing levers adjust the marker of a Jaquet chronograph. While the subject assumes a perfectly inattentive attitude, record a number of respiratory cycles upon a drum revolving at a moderate speed. How many cardiac cycles does each respiratory cycle embrace? Do you observe an increase in the cardiac frequency on inspiration? Explain this variation. Annotation. — A simple stethograph may be made by fastening a small rubber pouch by means of a broad linen strap against the chest. The single orifice of this pouch is connected Vjy means of a cannula and a piece of rubber tubing with a record- THE CIUCULATION 131 ing tamhour. Anotlier convenient form consists of a long rubber tube about 2 cm. in diameter and closed at one end. Its otlu-r end is connected with a recording tambour by means of small tubing (Fig. S 4). The interior of the hirge tube is occii- l)ied by a long spiral spring. When applied transversely around the chest this tube will be lengthened on inspiration and air will be drawn into it, c-ausing the membrane of the recording tambour to be displaced inward. On expiration, the recoil of the tube, aided by the spiral, increases the pressure within its lumen and forces the rubber membrane of the tambour outward. Marey's stethograph (Fig. So) consists of a metal plate which is fastened to the surface of the chest by means of a strap. The changes in the tension of this plate suffered by it in con.sequence of the respira- tory movements, are conunimicated by means of a lever to a receiving drum. The latter, in turn, communicates with a recording drum. LESSON XXVI RESPIRATION MECHANICS OF RESPIRATION 1. The Spirometer. — Study the construction of the spirometer (Hutchinson). Breathe normally, then close the nostrils and exhale normally through the mouthpiece of this instrument. Determine the movement of the pointer and calculate the volume of the tidal air. Fig. 86. — Winthich's Modification of Hutchixsox's Spirometer. (Reichert.) Breathe normally; then exhale forcibly through the mouthpiece. Determine the volume of the supplemental air. Set the spirometer at 5000 c.c. Breathe normally ; then inspire deeply through the mouthpiece. Determine the volume of the complemental air, 133 134 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY Set the spirometer at zero. After several normal respirations, in- spire as deeply as possible and immediately expire as much as possible through the mouthpiece of the spirometer. Ascertain the vital capacity. 2. Schema Illustrating the Action of the Thorax.— Examine the con- struction of the model represented in Fig, 87. (a) Normal Respiration. — Lower and raise the rubber membrane closing the bell-jar. Observe that the rubber pouch representing the lung is expanded during the first movement, and decreased in size during the second. Clearly, these changes are brought about by an action upon the entire external surface of the rubber pouch. When the pressure in the "intrapleural space" (between the surface of the rubber pouch and the wall of the bell-jar) is decreased by the downward move- FiG. 87. — Apparatus Illustrating the Expansion of the Lung, (Laulanie.) n. Bell jar; B, lung in form of rubber balloon; M, manometer in connection with "intrapleural space." Another manometer may be connected with the inlet-tube to register the "intrapulmonic pressure." ment of the "diaphragm" (rubber membrane), the walls of the "lung" (rubber pouch) are pulled uniformly outward. An area of low pressure is thereby established within the "lungs," forcing a certain quantity of air to flow through the "trachea" (inlet tube) into the pouch. The reverse relationships are established by the upward movement of the "diaphragm," simulating expiration. The two manometers fastened to the top of this model are connected, on the one hand, with the "intrapleural space" and, on the other, with the "trachea," Carefully observe the variations in the pressures dur- ing inspiration and expiration, showing that the fall in "intrapleural pressure" is responsible for the expansion of the "lung" and the subse- quent influx of air into its spaces. Normally, of course, the intrapleural RESPIRATION 135 space is a capillary space filled with pleural fluid. This implies that the surface of the lung is everywhere in dose coiita(!t with the inner surface of the wall of the thorax. (b) Forced Respiration.- IjOwvv and raise the "diaphragm" more forcibly, thereby producing a more ample expansion of tlie ''lung" and more decisive variations in pressure. (c) Dyspnea and Asphyxia.^Tho former condition may be repro- duced in a mechanical way l)y partially closing the stop-cock with which the inlet tul)(> is equipped. This would coirc'spond to an incomplete closure of the trachea and would greatly imj)air the interchange of the respiratory air. Note the resistance now acting against the "dia- phragm." Obviously, this diminution in the caliber of the inlet tube must augment the variations in the intrapleural and intrapulmonic pressures. Close the stop-cock completely, simulating the condition of asphyxia, or complete absence of air. (d) Collapse of the Lungs. — Expand the "lung" by moving the "diaphragm" downward. Suddenly permit air to rush into the "intra- pleural" space by slightly tilting the rubber cork closing the upper orifice of the bell-jar. Observe the immediate loss of "intrapleural" pressure and collapse of the "lung." Having in this way destroyed the "intrapleural" pressure, endeavor to expand the "lung" by moving the "diaphragm" downward. 3. Application of Above Principles to the Thorax of the Mammal. — Anesthetize a cat and maintain the anesthesia throughout the following experiments: Perform tracheotomy. Make a median incision through the skin in the midventral line of the body, beginning near the tip of the sternum and extending well along the linea alba. Reflect the skin on each side so as to expose the ventral aspect of the thorax. Study the mechanism of normal respiration. Note the excursions of the diaphragm and contraction of the neighboring intercostal muscles. Observe the downward movement of the liver and stoniach on inspira- tion. Which part of the chest is affected most in quiet breathing? Produce forced respiration by partially closing the rubber tube attached to the tracheal cannula. The normally diaphragmatic type of respira- tion is now gradually augmented by costal respiration. Observe also that the accessory movements of respiration are now much more con- spicuous. 4. Action of the Diaphragm. — Open the abdominal cavity by an incision through the linea alba. Petract the margins of the wound and depress the liver. Observe: (a) The nmscular and tendinous portions of the diaphragm, (6) the general shape of this septum, (c) the course of the fibers composing its muscular part, (d) the manner of attachment and insertion of these fibers, and (e) the character of their contraction. Determine the distance traversed by the tendinous portion of the diaphragm on quiet inspiration. Identify the complemental space, bounded by the upper surface of the diaphragm and the opposite wall 13G ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY of the chest. Observe that this space is widened on inspiration and that the lower borders of the lungs are then drawn into it. Trans- illuminate this region, so that indi\'idual alveoli may be made out. Note that the tissue of the lung is in absolute contact with the tendinous portion of the diaphragm. 5. Intrapleural Pressure. — Procure a water manometer. Color the water with a little indigo-carmin. Connect the central tube of this manometer with a metal cannula, about 10 cm. in length and curved at its end. Force the end of this cannula through the soft tissues of the seventh intercostal space and immediate^ turn it so that it comes to lie flat between the surface of the lung and the chest wall. Do not move it excessively, because this might give rise to a leakage of air into the intrapleural space and a collapse of the lung. Observe that the hquid in the manometer is drawn toward the chest as soon as the end of the cannula has perforated the wall of the thorax and has forced the lung tissue away from the inner surface of the chest wall. The .end of the cannula thus comes to He between the visceral and parietal layers of the pleura. The air in this artificial cavity, and hence also the liquid in the manometer, is exposed to the elastic recoil of the lung tissue. The force of this recoil is indicated by the inward movement of the liquid (cm. H2O). Inasmuch as the lung tissue is more highly stretched during the inspiratory period, this press- ure must fluctuate. It approaches zero (line of atmospheric pressure, 760 mm. Hg) at the end of expiration and assumes a value of as much as — 5 mm. Hg (756 to 755 mm. Hg) on quiet inspiration. Partially occlude the rubber tube attached to the tracheal cannula. As the breathing assumes a labored character, these differences in the intrapleural pressure become more apparent ( — 8 to — 10 mm. Hg, in cats) , because the lung tissue is now put under a greater elastic tension than during normal respiration. 6. Collapse of the Lung. — Inspect the tendinous portion of the dia- phragm through the wound in the abdominal wall. Note that the pink pulmonary tissue hes in absolute contact with it. Twist the cannula slighth', allowing air to enter the pleural sac. The lung tissue will then be seen to recoil from the diaphragm (pneumothorax). This procedure most generally leads to the collapse of only one lung, while the other lung remains expansible and is capable of effecting an adequate inter- change of the gases. Discuss the effect of placing the chest and posterior part of the animal in a compartment in which a negative pressure may be produced equaling the intrapleural. Open the cavity of the thorax by a cut through the median line of the sternum. Institute artificial respiration through the ether bottle. Note the position of the cannula in the now actual and greatly enlarged intrapleural space. Withdraw it. Temporarily discontinue tlie artificial respiration. Observe that the respiratory muscles continue to contract in spite of the fact that the lungs can no longer be expanded. As the CO2 accumulates in the RESPIRATION 137 system, stiinulatinji the respiratory center to inoreased activity, these reflex movements frequently assume a spasmodic character. Inspect the internal aspect of the chest wall, and note the shape of tlie thoracic cavity. Identify the pulmonary Ijlood-vessels. Trans- illuminate the border of either lung, notinfi its alveolar structure. Iden- tify portions of the visceral pleura below the apex of tlie heart. Note its structural peculiarities. 7. The Phrenic Nerves. — Isolate both phrenic nerves above the diaphraurm and place tiiem in loose ligatures. These nerves are easily found, because they descend in close proximity to the heart, the right selecting the highway of the inferior vena cava. Stimulate them separately with single induction shocks of moderate strength. Observe the resultant contraction of the corresponding half of the diaphragm and note the effect of this contraction upon the position of the ab- dominal organs. Kill the animal by an overdose of ether. Trace the course of each phrenic nerve to its origin ui the cervical portion of the spinal cord. 8. Swim Test. — Grasp the tracheal cannula with your left hand, and separate the trachea and lungs, together with the heart and large blood-vessels, from the neighboring parts. Place this mass in water, observing that the buoyancy of the lungs is sufficient to carry con- sideral^le additional weight. How would an atelectatic lung behave under these circumstnnces? What use is made of these facts medico- legally? 9. The Excised Lung. — Remove the metal caimula from the model, illustrating the manner in which the lungs are expanded. Insert this cannula in the trachea of the excised lungs, and suspend this preparation in the bell-jar. Repeat the observations made previously with the rubber pouch. Remove the lungs. Compress them in the palm of your hand. Are you able thereby to expel all the air from them? Repeat the swim test. Explain your inabiUty to render them air free. LESSON XXVII RESPIRATION (Continued) STETHOGRAPPiY. METHODS OF ARTIFICIAL RESPIRATION. PULMOTOR. 1. Frequency of Respiration. — Stiuly the movements of the thorax and abdomen. Differentiate between diaphragmatic and costal breath- iiifj;. INIeasure the cireumferenee of the chest at the level of the nipples on deep expiration and inspiration. Count the number of respirations of the subject first in the horizontal and then in the erect position. Count again after a stationary run lasting thirty seconds, and again after forty to fifty flexions and extensions of the arms or knee bendings. Explain the result. 2. Percussion and Auscultation. — Familiarize yourself with the nor- mal percussion sound of the lungs as ol)tained, say, in the region below the clavicle. Outline the upper boundary of the liver and the area of cardiac dulness. Make a diagram showing the position of the thoracic viscera. Familiarize yourself with the normal vesicular sounds of the lungs. Auscultate over the bronchi and trachea. 3. Stethography.— Adjust a stethograph to the chest of the subject while he is (juietly sitting beside a table (see Fig. 84). Allow a recording drum to register the respiratory movements over the record of a Jaquet chronograph. Ask the subject to take two or three deep breaths in quick succession. Explain the result. Record normal curves of respiration for about twenty seconds. Read aloud during the next forty seconds. Carefully note the modi- fications produced by the voice. Ask the subject to hold his breath after a moderate inspiration. The breaking point will be reached in about forty seconds. Repeat after a deep inspiration. The breaking point will now be reached after about fifty seconds. Repeat after having breathed forcibly for two or three minutes. The brealcing point then occurs after two or three minutes. Since the imperative demand to respire is due principally to the accumulation of carbon dioxid, and only in a lesser degree to the scarcity of oxygen, the breaking point cannot be much prolonged by the previous inhalation of oxj'gen. Register a normal curve of respiration for about twenty seconds. Drink half a glass of water without stopping. Explain this modifica- tion. Record normal curves of respiration. Ask the subject to approxi- mate the tips of his two index-fingers. Explain the change in the char- acter of the respiratory movements. Take tracings of the modified respiratory curve of laughing, sneez- ing, and coughing. 139 140 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 4, Influence of Carbon Dioxid. — Compress the nostrils of the sub- ject and allow him to breathe from and into a rubber bag containing about 30 liters of air. As soon as the CO2 has accumulated sufficiently the subject will breathe more rapidly and more deepl}'^ until his rate is about forty to the minute. Stop the experiment soon after the occur- rence of the hyperpnea. Repeat this experiment after having interposed a receptacle of 1 or 2 liters capacity containing soda-lime or sticks of sodium hydrate. The carbon dioxid will be absorbed, while the oxj^gen in the bag is being used up. Consequently, there will be no hyperpnea. Only a few minutes will be required to establish this fact. ImmecUately allow the subject to breathe normal air, otherwise the oxygen deficiency will lead to cyanosis, frontal headache, and unconsciousness. 5. Artificial Respiration. — Familiarize yourself with the Sylvester and Schafer methods of artificial respiration. Place the subject upon his back with the feet somewhat elevated. Take a position at the head ^^^^^^^^^^^^^^^ ' 1 r^ cs^ Fig. 88. — Position to Be Adopted for Effecting Artificial Respiration in Cases OF. Drowning. {Sr.haefer.) of the subject and grasp his wrists. Now bring the forearms against the sides of the chest and press gently inward and downward against the ribs. Release the pressure, allowing the elasticity of the chest wall to restore normal conditions. Bring the arms above the head so as to stretch the accessory muscles and to enlarge the chest still further. Repeat this procedure at the rate of eighteen times in a minute (Syl- vester) . Place the subject upon his ventral surface with a roller cushion under the epigastric region. Take a position over the legs of the subject, fac- ing his head. Place the palms of your hands against the posterior and lateral aspect of the subject's lower ribs. Bring an even and gentle pressure to bear upon this region. Release the pressure so as to allow the elasticity of the chest wall to restore normal conditions. Repeat this procedure at the rate of sixteen to eighteen times in a minute (Schafer). What are the advantages of this method? Study the construction and action of the pulmotor. What are its advantages and disadvantages? Contrast. LESSON XXVIII RESPIRATION (Continued' NERVOUS REGULATION OF RESPIRATION 1. Accessory Movements of Respiration.- Aiicstlu-tizc a mammal and continiu' the ancstht'sia Ihruu^liouL tlic following experiments: Perform trj\c'heotomy. Observe the movements of the facial muscles and note especially the changes in the size of the nostrils during inspira- tion and expiration. Render these movements more conspicuous by temporarily occluding the rubber tube attached to the tracheal cannula. 2. Self-regulation of Respiration. — Attach a pair of bellows to the tracheal cannula. Suddenly inflate the lungs. Note the expiratory effort immediately ensuing. Suddenly deflate the lungs and observe that the animal makes an inunediate effort at inspiration. Explain these results upon the basis of the self-regulatory function of the vagi nerves. 3. The Trigeminal and Glossopharyngeal Nerves. — Apply a stetho- graph to the chest of this animal and register the respiratory movements upon the paper of a slowly revolving kymograph. Stinmlate the nasal lining by means of a small plug of cotton attached to the end of a stick of wood. Note the resultant inhibition of respiration and forced ex- piratory efforts (act of sneezing). Enumerate the different nervous parts involved in this reflex. Stimulate the lining of the fauces and plmrynx in the same manner, producing thereby those modifications of respiration which constitute the act of coughing. Trace the course of this reflex. 4. The Larynx. — IVIake a median incision through the skin covering the region of the larynx and hyoid bone. Ligate the vein crossing the larynx and reflect the skin. Identify the thyroid and cricoid cartilages. Note the movability of the larynx and trachea. Isolate the superior and inferior laryngeal branches of the vagus on both sides, and place them in loose silk ligatures. Annotation. — The superior laryiifjeal ner\e pursues a course transversely across from the vagus nerve, and enters the hiteral a.spect of the thyroid cartihige. It is the largest nerve of this region. The inferior laryngeal nerve is isolated most readily lielow the larynx. It piu-sues a course upward along the trachea to enter the inferior aspect of the larynx. Cut across the pharynx between the hyoid bone and upper margin of the thyroid cartilage. Bring the tip of the epiglottis through the incision and secure it by means of a pair of artery forceps. Enlarge the incision laterally so that the laiynx may be raised and an unol> structed view be obtained of its interior. Identify the true and false vocal cords, the glottis, and the ventricles. Observe the alterations in the size and shape of the glottis in quiet inspiration and expiration. 141 142 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY Temporarily occlude the rubber tube attached to the tracheal cannula, producing dyspnea and thereby rendering these variations more con- spicuous. Stimulate the lining of the larynx with a tuft of cotton fastened to a wooden stick. Note the resultant inhibition of respiration and the forced efforts at expiration (act of coughing). Compare these effects Fig. 89. — Lateral View of Larynx TO Illustrate the Action of the Crico- thyroid Muscle. H, Hyoid bone; M, thyrohyoid mem- branes; PA, pomum Adami; T, thyroid cartilage; C, cricoid cartilage; Tr, trachea; CT, cricothyroid m-uscle; P, vertical plate of cricoid with {A) arytenoid cartilages placed transversely upon its articulating processes; VC, vocal cords; 72, imaginary center of rotation of cricoid. When crico- thyroid muscle contracts, T and C are brought closer together, while A is forced away from PA. Fig. 90. — The Innervation of the Larynx (Posterior View; One Side). B, Base of tongue; E, epiglottis; A, arytenoid muscles; CA, crico-arytenoid muscle; T, trachea; V, vagus nerve; SL, superior laryngeal nerve; / and O, its inner and outer branches; JL, inferior laryngeal nerve; Br, vagal fibers innervating bron- chial musculature. with those commonly observed after the entrance of a foreign body into the larynx. 5. The Superior Laryngeal Nerve.— Place the intact superior laryn- geal nerve in shielded electrodes and stimulate very briefly. Analyze the effect produced thereby upon (a) the general character of the respiratory movements, and ih) the action of the laryngeal muscles. Divide the superior laryngeal nerve between two ligatures. Stimu- late its distal as well as its central end repeatedly, analyzing the effects producecj in each case. RESPIRATION 143 Annotation. — T1m» superior Iiiryii<;i'al nerve is eliiefly Ji sensory nerve, hut also embraces a eertain nuiiiluT of motor fillers wliich innervate tlie ericothyroicl muscle. Consec|uently, the stimulation of the intact nerve must give rise to an inliihitifin of respiration and forctnl expiratory efforts, and secondly, to an apjiroximation of the cricoid and thyroid cartilages and a greater tension of the vocal cords. G. The Inferior Laryngeal Nerve. — Place the intact inferior laryn- gval norve in shielded electrodes. .Stimulate briefly and note the effects of the stimulation upon (a) the general character of the respiratory movements, and (6) the action of the laryngeal nmscl(\s. Divide the inferior laryngeal nerve between two ligatures. Stimu- late its distal as well as its central end, and study the effects (if any) produced in each case. B Fig. 91. — Diagrvm lLLrsTR.\^TiNG the Abduction and Adduction of the Vocai. Cords. A, Abduction: 1, point of insertion of the post, crico-arytonoid muscle; G, glottis. B, adduction: 2, points of insertion of the lat. crico-arytenoid and thyro-arytenoid muscles; 3, point of insertion of the arytenoid muscles. The dot indicates the position of the center of rotation of the arytenoid caitila^es. Annotation. — ^The inferior laryngeal nerve is a motor nerve, innervating the muscles of the larynx, except the cricothjToid. Consequently, its stimulation must give rise to peripheral eflFects only. These consist chiefly in contractions of the arytenoid muscles which have to do with the approximation of the vocal cords and the size of the glottis. In the dog the innervation of this nerve, as well as that of the superior laryngeal nerve, is unilateral. 7. The Main Trunk of the Vagus Nerve. — Expose both vagi nerves below their superior laryngeal branches. Divide each nerve between two ligatures. Observe that the rate of the respiratory movements is now greatly reduced, whereas their depth is increased. The total gas interchange is hot seriously impaired, Stmiulate the central end of either nerve with weak, medium, and strong currents. Discuss the part which the vagi nerves play in regulating the frequency and am- phtude of the respiratory movements, formulating a concise pictiu'e of the self-regulation of respiration by means of these nerves. Administer an overdose of ether to the animal. LESSON XXIX RESPIRATION (Continued) LOCALIZATION OF THE RESPIRATORY CENTER. PLACENTA. RESPIRA- TION IN TPIE FISH 1. The Localization of the Respiratory Center. — Anesthetize a eat and maintain the anesthesia until the animal has been killed. Perform tracheotomy. Place the animal upon its ventral surface. Make a median incision through the skin covering the region of the lower cer- vical and upper thoracic vertebrae. Identify the spinous process of the seventh cervical vertebra and follow this projection to the laminse, re- tracting the spinal muscles. Stop bleeding l)y applying dry tampons or by torsion and ligation of the blood-vessels. Cut away the laminse and process of the seventh vertebra until a short segment of the spinal cord has been exposed. With a curved needle draw a loose ligature around the cord. Apply a stethograph to the chest of the animal and allow the record- ing drum to register the respiratory movements upon a slowly revolving kymograph. A sufficienth' long normal record having been obtained, raise the spinal cord and divide it. The animal continues to respire normall}', showing thereby that this lesion does not interfere with the efferent impulses to the muscles of respiration. Divide the students into three groups, and proceed as follows: Group A. — Expose the spinal cord in the region of the third cervical vertebra. Place a loose hgature around it, and divide it after a short normal tracing has been taken. The respiratory movements cease almost immediately, owing to the fact that the transection has separated the nuclei of the respiratory nerves, principally those of the phrenic nerves, from the respirators^ center. The latter, therefore, must lie above this section. Group B. — Make a median incision through the skin covering the occiput. Advance in the direction of the foramen magnum. Enlarge the opening until a clear view of the region of the pons is obtained. Divide the latter structure transversely above the medulla oblongata. Since the animal continues to breathe, the principal center of respiration must be situated below this level. Group C. — Make a median incision through the skin covering the occiput. Palpate this region until a depression in the vertebral column is clearly felt through which it is possible to reach the medulla directl}'. Pierce this structure with a pointed instrument. Respiration ceases immediately. Compile the results of the three groups of students and draw con- clusions regarding the location of the respiratory center. 10 145 14(5 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 2. The Placenta. — Procure a placenta. Wear rubber gloves or handle this organ only with instruments. Study its appearance and draw a diagram to illustrate its position in the uterus. Divide the umbilical cord and identify its constituent blood-vessels. Observe the character of the outer and inner surfaces of the placenta. Note that the umbihcal vessels complete their subdivision before the substance of the placenta is reached. Follow a cluster of vessels and separate the tissue suppHed by them from the tissue supplied by neighboring groups of vessels. Suspend the fringed tissue so isolated in a beaker filled with water. By this means one may reproduce the conditions normally existing in this organ, the water representing the maternal blood with which the fetal blood is in diffusion relation. 3. The Respiratory Movements in Fishes. — Carefully study the opening and closing of the gill plates. What is the relation between this movement and the movements of the floor of the mouth? Draw diagrams to show the parts involved in these movements. Show the position of the maxillary and bronchostegal valves during inspiration and expiration. LESSON XXX RESPIRATION (Continued) THE CIRCULATION IN THE LUNG OF THE FROG. PHENOMENA OF INFLAMMATION. EFFECT OF CHANGES IN INTRATHORACIC PRESSURE UPON THE LESSER CIRCUIT 1. The Lung of. the Frog.^Pith a frop. Open its jaws widely, and draw a small curved needle and silk thread through the soft tissues around the orifice of the trachea. Insert the end of a straight glass cannula in the tracheal orifice and secure it by means of the ligature. Attach a short piece of rubber tubing to the cannula. Open the ab- dominal cavity of the frog widely. Blow air gently through the can- nula until both lungs have been fully inflated. Kink the rubber tube and apply a cHp. Remove both lungs with the heart and suspend them until thoroughh' dried. Transilluminate them. Note the large central cavity in each as well as the indi\'idual alveolar spaces along the wall. Cut each lung in half and inspect its interior. 2. The Capillary Circulation in the Frog's Lung. — Pith a frog with- out losing any blood. Block the opening by means of a pointed piece of match. Proceed as has been described in paragraph 1, imparting to the lungs a moderate degree of inflation. Raise one lung out of its cavity and place it upon the glass fitted in the orifice of a plate of cork, such as has been described upon, page 99. Place a cover-slip upon the upper surface of this lung and apply gentle pressure to flatten the latter. Study the blood flow under the low and high powers of a microscope. Examine a preparation of injected pulmonary capillaries under the microscope. 3. Phenomena of Inflammation. — Allow a drop of a dilute solution of mustard to be drawn by capillarit}' under the glass covering the sur- face of this lung. Study the resultant phenomena of inflammation as exemplified b}- changes m the circulation, viz., the relaxation of the capillaries, the retardation of the flow, the greater vascularity of this part, the gradually increasing numbers of white blood-cells, the fixa- tion of these cells to the walls of the vessels, and their final migration into the neighboring tissues. 4. Effect of Variations in Intrathoracic Pressure Upon the Blood- flow Through the Lungs. — With the help of the apparatus represented in Fig. 92 studj- the effect of the inspiratory increase and expiratory decrease in intrathoracic pressure upon the blood-flow. The large orifice of a bell-jar is closed with a rubber membrane. To its central 147 148 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY area is attached a metal plate and ring, so that the membrane as a whole may be lowered and raised. The upper orifice of the bell-jar is closed by means of a rubber cork bearing a relatively narrow inlet tube. This chamber is traversed b}'- a horizontal tube of very soft rubber, draining a receptacle filled with water. Allow the water to flow steadily through this tube. Then lower the rubber membrane (diaphragm), thereby decreasing the pressure in the glass compartment (intrathoracic pressure). Note that the "pul- FiG. 92.— Device to Illustrate the Influence of the Respiratory Movements UPON THE Flow of the Blood through the Pulmonary Blood-vessels. (Hering.) A, Bell jar; B, rubber membrane closing it; V, soft-rubber pouch to imitate the pul- monary blood-vessels; GH, arrangement for forcing water through V under a constant pressure; j, manometer connected with "intrapleural space." On inspiration, pro- duced by moving the rubber membrane downward, the intrapleural pressure is decreased. This gives rise to an aspiration which tends to pull the wall of V outward, facilitating the flow from G to H. monary blood-bed," as represented by the thin rubber tube, is now large, allowing a free through flow. The opposite effect is produced by rais- ing the diaphragm. The caliber of the pulmonary blood-vessels is then (lccr(>ased and the pulmonary resistance increased. .5. Effect of Decreased Atmospheric Pressure. — Place a mouse under the bell-jar of an ordinary air-pump. Allow the pressure existing within this compartment to be recorded by means of a mercury manometer connected with the suction tube of the pump. Apply suction, lowering RESPIRATION 149 the pressure gradually to oiic-lialt' aiul one-third of an atmosphere (700 nun. ?Ip;). Under normal coiidilions oxygen exerts a pressure of 20.94 per cent, of an atmosphere or about lo3 mm. Hg. At 10 per cent, (one-half of an atmosphere) the animal will l>ecome restless and dyspneic, and at 7 per cent, (one-third of an atmosphere) lose conscious- ness and die. This pressure corresponds to the pressure prevailing at an altitude of 30,000 feet. LESSON XXXI RESPIRATION (Concluded) ELIMINATION OF CARBON DIOXID AND CONSUMPTION OF OXYGEN 1. The Elimination of Carbon Dioxid and Water.— Kxliulc repeatedly through a ji;lass tube into a beaker lilled with lime-water. Explain the resultant turbidity. Procure a 4-ouncc Woulffc bottle with three necks and the necessary delivery tubes and stoppers; three 5-inch calcium chlorid tubes with side tubes and perforated stoppers; a (Jeissler l)ull) with KOH and C'aCb tubes, two small flasks with stoppers, and two glass tubes; a 2-liter bottle in which the animal is placed ; and two 8-Hter bottles. The tubes containing the calcium chlorid should be put in the diy- ing oven at a temperature of 100° to 120° C. for several hours. They arc then cooled in a desiccator. Weigh two of them, marked e and /. The Woulffe bottle and Geissler bulbs are filled with a 50 per cent, solution of KOH. To the latter is attached the CaCh part and rubber connecting tubes, which are then clamped. The whole is weighed. The two flasks h and h are filled with a strong solution of Ba (0H)2. Weigh the bottle d into which the animal is to be placed later on. Connect these parts and fill one of the siphon bottles (8 Uters). Arrange the other {k) at a distance of 1 m. below the filled one (i). Place a white rat into the 2-liter l)ottle and weigh. Connect this bottle with the others. Start the siphon. Adjust the distance of the siphon bottles so as to give a sufficient ventilation to the animal (indi- cated by its rate of respiration). When the upper bottle has been nearly emptied, clamp the tube connecting it with the adjoining flask and quickly put the second (now filled) bottle in its place. Remove the clamp, and again siphon. Continue this procedure for about one hour. At the end of this period clamp the siphon tube, turn the stoppers of the CaCla bottles, and disconnect the tubing. Weigh tubes d, e, f, and g. Obviously, parts a, h, and c remove the HoO and CO2 from the air supplied to the animal, whereas parts e, f, and g collect the H2O and CO2 given off by the animal in the course of this experiment. By weigh- ing these parts before and after this test a means is provided for deter- mining the amount of these excreta. Determine the loss in weight suffered by the animal during this test. Ascertain how much H2O and CO2 left the animal during this period. Do these amounts correspond to the loss in weight of the animal? Explain. 2. The Consumption of Oxygen. — Fill the pressure tube B with a solution of potassium pyrogallatc, made bj^ mixing 2 parts of a 25 per 151 152 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY cent, aqueous solution of KOH and 1 part of a 5 per cent, aqueous solution of pyrogallic acid. The air must be analyzed as it passes into KOH BaiOH). CaCk ^""««' CaCk CaClt j^amOiCli Fig. 93. — Appaeatus for Estimating the CO2 and H2O of the Expired Air. (Hall.) the apparatus represented in Fig. 93 and again as it leaves the siphon bottle. To accomplish this end fill the gas buret A with water by -JB Position 1. Position 2. Positions Fig. 94. — Gas Burets for Determination of Oxygen. (Hall.) suction. Connect its upper end with tube K of the respiration appa- ratus (Fig. 93), and allow the siphoned air to displace the water in the RESPIRATION 153 buret. Turn the stop-cocks upon its two ends, and connect its lower entl with the rubber tube of the pressure bottle B, containing; the potas- sium pyrof!;allate. Expel th(^ air from the eomieetiiiK tube and turn the three-way stop-cock so that the pyro{z;allate may flow into the buret. Raise the pressure tube and finally clamp the connecting tube close to the l)uret. Turn the buret repeatedly (ten minutes) and open the clamp, allowing the potassium pyrogallate to take the place of the absorbed oxygen. Then remove the clamp, but allow the tubes to remain in connection for another ten minutes. At the end of this period adjust the level of the solution in the buret to the level of the solution in the pressure tube. Take the reading. Analj'ze the oxygen content of the normal air. Sul)tract the amount of oxygen of the respired air from that found in the noi-mal air. The result corresponds to the amount of oxygen consumed by the animal. LESSON XXXII THE NERVOUS SYSTEM REFLEX ACTION 1. Histologic Study of Different Neurons. — Examine under the microscope motor neurons from llie cerebral cortex, cells of Purkinje from the cerebellum, motor cells from the anterior horn of the spinal gray matter, and sensoiy cells from the spinal ganglion. Draw a dia- gram of each. Orient yourself regarding the principal tracts of the spinal cord, the formation of the spinal roots and their function, and other data of general interest. 2. Dissection of the Nervous System of the Frog.— Kill a frog with ether. ^lake a median incision tlnougii the skin covering the skull cap. Hold the scalpel slantingly and perforate the bone about midway between the eyes, taking care not to penetrate too deeply. With a pair of small forceps cut away the bone around the perforation, enlarg- ing the opening considerably. Having uncovered the white cerebral hemispheres and olfactory lobes, dissect backward until j'ou have brought into view the rounded, grayish optic lobes or corpora bigemini. The cerebellum is rudimentarj^ and occupies a position in front of these bodies. Identify the optic nerves. Expose the entire spinal cord by breaking away the vertebra? along the dorsal aspect of the animal. Identify the spinal nerves and spinal roots. 3. Reflex Action. — Pith a frog and destroy its brain (not the spinal cord). Suspend the animal from a stand over a plate. Pinch the toes of one foot with the forceps. Observe that the foot is withdrawn from the seat of the stimulation by muscular activity. Produce this reaction by immersing the foot in a weak solution of acetic acid. Repeat by applying the electrodes to the sole of the foot and stimulating with a brief tetanic current of moderate strength. Destroy the spinal cord with a wire. Repeat the electric excitation and observe whether or no the different impulses so generated still induce motor response's. Draw conclusions regarding the part played by the spinal cord in this reaction. Annoiation. — The solution of acetic acid should be weak, possibly 3 drops of glacial acetic acid to about 20 c.v. of water. Strengthen it in case it should fail to stimulate. Immerse the foot in clean water after every stimulation. When the electric current is employed as a means of inducing reflex action, differentiate sharply between the local nniscular contractions and those co-ordinated general contractions which eventually cause the removal of the foot from the seat of the stimulation. In order to save material the student may omit destroying the spina! cord with the wire. This procedure, as may l)e surmised, destroys the spinal reflex ac- 156 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY tions, because it jji-oduces a break bet\Yeen the afferent and efferent arcs of the reflex circuits. 4. Localization of the Reflex Center for the Hind Legs. — If the spinal cord has not been destroj^ed in the frog used for Experiment 3, this animal may now be employed for the following test: Suspend the brainless frog in the usual way. Open its abdominal and thoracic cav- ities and remove the viscera. Identify the vertebral column with its nine vertebrae. Produce a reflex by stimulating the sole of the foot electrically. Now make a transverse cut between the second and third vertebrae. Test the reflexes again. Cut between the third and fourth Fig. 95. — Diagrammatic Representation OF THE Brain of the Frog. ON, Olfactory nerves; OL, olfactory lobe; C, cerebrum; T, tween brain; OpL, optic lobes; Cc, cerebellum; M, medulla; Co, spinal cord. The cranial nerves are indicated by Roman numerals. Fig. 96. — Diagram to Show the Posi- tion OF THE Reflex Centers in the Spinal Cord of the Frog. BC and BN, Brachial center and nerve; A, center for the parts of the trunk; SC and »SA'', sciatic center and nerve. The numbers indicate the different vertebrae. vertebrae and again test the reflexes. Continue this process until no longer able to elicit this reflex. At which level do you localize the sciatic center? Annotation. — -The frog possesses nine vertebrje. Its vertebral coUnnn ends at the dorsal prominence. From here the tenth vertebra or urostyle extends backward to the tip of the body. Notice that the three roots of the sciatic nerve enter the cord at different levels, the arrangement being such that a transverse cut made t)etween the sixth and seventh vertebrae traverses the upper extent of the sciatic center, destroying the reflexes executed with the help of this nerve. 5. Localization of Function. — The same frog may be used for the following test: Identify the three roots of one sciatic nerve and place them in loose ligatures. Place the frog upon a moistened plate and stimulate each root separately with single induction shocks of very THE NERVOUS SYSTEM 157 moderate intensity. Divide them ami sliimilatc the distal end of each. ()l)servo that they iimci-vatc dit'tcrcnt groups of muscles. A similar localization of function may ho detected in the sciatic center itself. \'ery fine needle electrodes should be used in mappinj^ out this area. 0. Summation of Afferent Impulses.^ — Destroy the ]>rain of a frog (not the cord). Adjust two thin coppei- wires to one foot about 1 cm. apart and connect them with the secondary coil of an inductoi'ium. Stimulate with a subminimal-refiex induction shock, i. e., with one which does not evoke a reflex, but may cause a local muscular reaction. Stimulate with two or three of these sho(;ks in quick succession, antl observe the reflex action ultimately resulting in consequence of this summation. 7. Effect of Thermal Stimuli. — Remove the wires from the frog used in ExpcM-iment G. Dip the foot at intervals into water of 10°, 20°, and 30° C. Which is the most efficient stimulus? Finally, immerse the foot in cold water, which is then heated gradually until an intense reflex is evoked. 8. Spreading of Reflexes. — Apply the electrodes to the foot of this frog and stimulate first with a weak current and then with a strong current. Note that the weak stimulation gives rise to a perfectly local- ized reflex, whereas the strong stimulation evokes, in addition, move- ments of the other leg, trunk, and forelimbs. In other words, the strong stimulation causes the primary impulses to spread to other reflex circuits. Hold the foot of one leg between your fingers. Place a small piece of filter-paper moistened with modcratelj' dilute acetic acid, upon the skin of the ventral aspect of the thigh of the same leg. Observe that the impulses so elicited eventually involve other reflex circuits, caus- ing the opposite leg to be moved. Naturally, if the filter-paper is brushed away by these movements, this result has a purely mechanical cause. Immerse the frog in fresh water. 9. Reflex Time. — Suspend the frog in the usual wa.y and stimulate the sole of one foot several times wath weak and strong electric cur- rents. Count in each case the number of seconds elapsing between the moment of stimulation and the onset of the reflex action. This interval is the so-called reflex time. What is the relationship between this period and the intensity of th(> stimulus. 10. Inhibition of Reflexes Upon Central Paths. — Expose and ligate the sciatic nerve of one side. Divide the nerve distally to the ligature. Apply the electrodes to the central end of this nerve. Immerse the foot of the opposite leg in a weak solution of acetic acid and simulta- neously stimulate the central end of the sciatic nerve with a weak tetanizing current. Note the resultant inhibition of the reflex. At what point of this reflex system do the impulses from the central end of the opposite sciatic nerve interfere with the impulses from the foot inmierscd in the acid? LESSON XXXIII THE NERVOUS SYSTEM (Continued) REFLEX ACTION. REMOVAL OF CEREBRUM 1. Inhibition of Reflexes by Higher Centers. — Kthorize a frog. Make a median int-ision tlirouKii the skin coxcrinfi; the skull-cap. Per- forate with (he point of a knife and enlarfj;e the opening by means of a pair of foreeps. Identify the eerebral hemispheres and remove them. After an interval suspend the frog and determine the reflex time in the usual way. Sprinkle a few cr\'stals of sodium chlorifl upon the upper surface of the optic lobes, and again ascertain the reflex time. Since these bodies possess an inhibitor action upon spinal reflex action, this means of stimulation will tend to lengthen this period. Remove both optic lobes, and again determine the reflex time. Obviously, their removal nmst destroy this inhibitor influence and intensify spinal reflex action. 2. Exaggeration of Reflexes by Means of Strychnin. — Inject a drop or two of a 0.5 per cent, .solution of sulphate of strychnin into the dorsal lymph-sac of a frog. After a few minutes stimulate the foot of this frog mechanically. Repeat at brief intervals, noting the progressive char- acter of the nmscular seizures. Blow 3^our breath at the frog or tap upon the table upon which it is resting. Upon which elements of the reflex circuit docs the strychnin exert its action? 3. Reflexes in Man.— Let the subject open his mouth. Touch the uvula with the end of an aseptic gla.ss rod. It will rise. Touch the fauces. The response may be either a movement concerned with the act of swallowing or the gagging reflex, an act tending to protect the digestive tract. Make a sudden movement in front of the eyes of the subject as if you were going to strike him in the face. The eyelids are closed. Touch the outer surface of the cornea of the subject with a cotton fiber. An immediate closure of the eyelids is the result. In all these instances, however, the character of the reflex may be modified vohtionally (in- hibition by the cerebrum). Shield the eye of the subject for a few seconds with your hand. Suddenly withdraw the latter, allowing Hght to enter the pupil. Ob- serve the decrease in the size of this orifice, brought about by the con- traction of the circular muscle cells of the iris (light reflex). Request the subject to accommodate alternately for far and near objects. The pupil is enlarged during far vision and constricted during near vision (accommodation reflex). Pinch the skin of the neck. The pupil will dilate (cihospinal reflex). 159 160 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY A simple secretory reflex may be produced by moistening the mucous lining of the mouth with a few drops of very dilute acetic acid or b.y chewing a piece of rubber or paraffin. The sneezing reflex may be elicited by touching the mucous lining of the nasal cavity with a few cotton fibers. Inhibit this reflex by pressing upon the upper lip with the index-finger. 4. Tendon Reflexes in Man. — Cross your legs, allowing one leg to hang perfectly free. Let the assistant strike the patellar ligament of the free leg with the outer margin of his hand. Note the contraction of the quadriceps muscle and the upward kick of the leg and foot. During this test the subject should be perfectly inattentive, otherwise cerebral inhibition will result. Interlock the index-fingers of your hands. While you make a forced effort to separate these fingers let the assistant elicit the patellar reflex. Note that the kick is now much stronger than before (reinforcement of reflexes). Explain. Stand beside a low chair with your leg resting upon it. Let the assistant strike the tendo achillis. The foot will be extended, owing to the contraction of the gastrocnemius muscle. While the ankle-clonus is not observed in healthy persons, the student should familiarize himself with the method employed in eliciting it. The patient is seated and rests his leg upon a chair of equal height, allowing the foot to project beyond its edge. Steady the leg with your left hand and with your right hand suddenly flex the foot upon the leg, so as to put the tendo achillis on the stretch. A series of clonic con- tractions of the corresponding muscles will result in persons afflicted with certain spinal diseases. Another peculiar phenomenon noted in certain spinal diseases is the so-called Babinski phenomenon. Under normal conditions the tickling of the sole of the foot results in a flexion of the toes upon the foot (plantar reflex), whereas under certain abnormal circumstances the first toe may be extended and the others flexed. 5. Muscle Tonus. — Etherize a frog under a bell- jar. When all sensibility has been lost, open the abdomen. Place the sciatic nerve of one side in a loose ligature. Suspend the frog in the usual way. Note that the legs are held in a position intermediate between complete re- laxation and contraction (tonus). Divide the sciatic nerve previously placed in the ligature. Observe that the corresponding leg now assumes a more dependent position, i. e., relaxes more completely. Remove the skin from the normal leg, and again note the position of this leg. It will now assume the level of the opposite leg, the sciatic nerve of which has been divided. Explain this result, making use of the contention that the tonus of skeletal muscles is dependent upon afferent stimuli (k^rivod from the integument, 6. Threshold of Stimulation. — Pith a frog. Carefully expose one sciatic nerve in the thigh. Determine the least strength of tetanizing current which will cause a spreading of reflexes when applied to the skin THE NERVOUS SYSTEM 101 of the foot. Apply the same stiimilus to the liniik of the sciatic nerve. The intensity of the stimulus n'(|uir('(l to evoke reflex aetion is usually less when appHed to the sense orj^ans. Make a median incision through the skin eoverinp; the dorsal aspect of this frog. Raise the skin and identify one of the many nerve-fibers crossing the dorsal lymph-space to innervate the skin overlying. Cut out a piece of skin al)out 1 cm. scjuan*, containing the terminals of this nerve. Raise this skin-tlaj), but allow it to remain in connection with the body by^ means of the nerve. Determine the least strength of stimulus required to cause a reflex movement when applied to the sur- face of this flap of skin Repeat, applying the electrodes to the afore- said nerve. As a rule, the threshold value of the current will b(> found to be lower in the former instance. 7. Effect of Removal of the Cerebrum. — Etherize a male frog under a bell-jar. When completely insensitive make a median incision through the skin covering the skull-caj) and perforate the skull with the point of a scalpel. Enlarge the opening and remove the cerebral hemispheres and olfactory lobes. Note that the junction between the cerebrum and the optic lobes is indicated externally by an imaginary hne drawn through the anterior margins of the ear drums. Work rapidly but care- fully. Bring the edges of the wound together by means of two or three sutures, and moisten the skin rci)eatcdly with fresh water. Allow the animal to recover fully. Carefully study its behavior: (a) What is its posture? Pass your hand in front of its eyes. Is it made to move thereby? Repeat this test upon a normal frog. Com- pare. (6) Gently pinch the toe of the decerebrated frog. Do you note any abnormality in its manner of jumping? Place the animal in water. Is its power of swimming affected in any way? Does it retain its upright position? (c) Place the frog upon its back. Does it right itself ? (d) Place the frog upon a somewhat roughened flat surface. Tilt the board gradually and note how wtII it adapts the axis of its l)ody to the surface. Repeat this test bj' placing the frog upon a small Ferris wheel. Gradually turn the wheel, noting that the frog attempts to reach the top by moving against the direction of the rotation. Repeat this test by placing the frog upon a rotating surface arranged horizon- tally. The long axis of its body will then be bent against the direction of the rotation (compensator}' movements of equilibration). (e) Hold a small tuft of cotton moistened with a few drops of acetic acid in front of its nostrils. The frog will make protective movements with its forelimbs and move away from the seat of the stimulation (trigeminal reflex). (/) Place a narrow board between the frog and an incandescent light. Force the frog to jump toward the Hght. It will avoid the object casting the shadow (retinal reflex). ig) Pass your index -finger over the skin covering the dorsal surface 11 162 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY of this frog. Observe that the decerebrated animal produces a pecuUar sound whenever touched. The same result may be obtained by grasp- ing the frog in such a way that your thumb and index-finger come to he laterally upon the abdomen'. Stimulate a normal frog in the same manner. Compare. Annotation.- — The test described last is one of the best means of ascertaining the function of the cerebrum. In the normal animal the act of croaking is imder the control of the cerebral hemispheres, i. e., it is an associated act. Consequently, it will be almost impossible to evoke it by inadequate stimuli. The removal of the cerebrimi, on the other hand, changes this complex act into a simple reflex. The influence of the higher centers having been destroyed, it may then be evoked by ordinary stimuli in a reflex way. A male frog may be recognized by the cushion-like thickening at the base of the innermost digit of the hand. Besides, the male rana esculenta possesses a bladder-like resonating pouch on each side of the mouth. Attention should also be called to the fact that an animal without cerebral hemispheres is incapable of "feeling." The sensorium ceases to exist after the removal of these structures, and only the ordinary reflex sensory mechanism remains behind. 8. Influence of the Cerebrum. — Place a normal frog in a basin filled with water. Warm the water slowly, and note that the frog will make complex efforts to escape as soon as the temperature of this medium has risen to about 25° C. Place a frog, the cerebrum of which has been destroyed, in cold water. Warm the water to 40° C, and observe the reflex movements resulting in consequence of the thermal stimulation. WTiile this ani- mal may escape from the basin, this result is accidental, and is due solely to the reflex contractions of the muscles. LKSSON XXXIV THE NERVOUS SYSTEM (Continued) STIMULATION OF THE CEREBRUM. THE FUNCTION OF THE ROOTS OF THE SPINAL CORD 1. Cerebral Localization. — Procure a pair of a(ljusta))l(' clcH'trodcs and coiinec't (Iumii with the secondary coil of an inductoriiiin. Arrange the electric apparatus for stimulation with a quickly interrupted cur- rent. Anesthetize a cat and maintain the anesthesia throughout the following experiments: Perform tracheotomy. Place the animal on its side. Make a median incision through the skin covering the skull- cap, and separate the edges of the temporal nmscles from the bone underneath. Adjust a trephine, about 1.5 cm. in diameter, to the anterior area of the right parietal bone at a distance of 0.5 cm. from the median line. Carefully work the trephine until it has penetrated the skull. Do not press upon it heavily so as not to break through suddenly, piercing the substance of the cerebrum. Remove the round plate of bone with a pair of forceps. Apply dry cotton, and stop the bleeding by pressing soft wax against the edge of the cut bone. Identify the dura mater and its blood-vessels. Observe that the surface of the dura rises with every systole of the heart and also during inspiration. Insert a thistle tube in the trephine opening. Fill it partly with warm saline solution and connect it with a recording tamliour. Register these pulsations upon the smoked paper of a kymograph. The w'anial cavity is in this way converted into a plethysmograph, registering the cardiac and respiratory changes in the volume of the brain. Remove the thistle tube and enlarge the trephine opening by means of a pair of bone forceps until the crucial area of the cerebrum has been completely uncovered. Stop the bleeding by means of wax and cotton tampons. Incise the dura mater, noting the escape of liquor cerebro- spinalis. Reflect the dura and expose the surface of the cerebrum along the crucial sulcus (fissure of Rolando). Place the animal on its right side and unfasten the left fore- and hind limbs. Using Fig. 97 as a guide, stimulate the surface of the cerebrum in the vicinity of the crucial sulcus with a weak tetanizing current. If no results are obtained, increase the strength of the current gradually and lessen the depth of the narcosis. Analyze the movements resulting in consequence of the stimulation of these different areas. 2. The Function of the Roots of the Spinal Cord. — Close the wound by means of a continuous sutur(\ Make a median incision through the skin covering the spinous processes of the lumbar v(M-tebra?. By means of forceps separate the fascia and muscle tissue from these processes. 163 164 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY Stop bleeding by tampons, torsion, and ligation of the blood-vessels. Expose the laminae of several adjoining vertebrae. Cut through them and remove the dorsal wall of the spinal canal of this region. Take care not to injure the spinal nerves. Incise the dura mater. Expose the spinal cord and identify the anterior and posterior roots of one of the spinal nerves. Isolate these roots and place each in a loose ligature. Stimulate each with a weak tetanizing current. Eventually tie these hgatures, the one upon the anterior root close to the cord, and the one upon the posterior root far Fig. 97. — Diagram Showing the Motor Points in the Cerebrum of the Dog. Fig. 98. — The Membranes of the Spinal Cord. 1, Dura mater; 2, arachnoid; 3, pos- terior root of spinal nerve; 4, anterior root of spinal nerve; 5, ligamentum dentatum; 6, linea splendens. {After Ellis.) away from the cord. Stimulate the distal end of the former with a weak tetanizing current. Repeat the stimulation upon the central end of the latter. Tabulate the results, and determine the direction of conduction in each root. Kill the animal by an overdose of ether. Remove a segment of the spinal cord, noting the size and shape of the subdural space, and the manner in which the spinal nerves are enveloped by dura. Remove the brain. Identify its different parts, and especially those to which attention has been called in the lectures. LKSSOX XXXV THE NERVOUS SYSTEM (Concluded) REACTION TIME 1. Reaction to Touch. — Ananp;o tho olcctric apparatus for stimula- tion with siniflc induct ion shocks. Insci-t a sij^nal and two simple kej'S in the primary circuit of an induction apparatus, and connect a pair of platinum electrodes with the secondary coil. Arrange to record the movements of the signal. Add a tuning-fork. Tho latter should be fastened to a separate stand and be allowed to record from left to right, ?". e., against the direction of rotation of the drum of the kymograph. Let the subject hold the electrodes against his tongue with his left hand, while his right hand grasps the handle of one of the two keys. Let the observer then spin the drum and close the other key. As soon as the; subject feels the make shock, let him break the current by opening his key. Draw ordinates to the curves and determine the time which has elapsed between the make and the break of the current. Repeat this experiment several times and ascertain the average reaction time. Fi(!. 99. — Re.\ction to Touch. Record of signal hdow (hat of tuniriK-fork (^Jti sec). S, Moment of stimulation; R, mo- ment of reaction. Repeat this experiment with a stronger stimulus. What relation- ship exists between the strength of the stimulus and the length of the reaction time? 2. Reaction to Light. — Arrange 5 dry cells in series, their total strength amounting to about 7 volts. Connect these cells with a small incandescent lamp (5 or 6 volts), a signal, and two simple keys. Ar- range to register the movements of the signal above the record of a tuning-fork vibrating in hundredths of seconds. Let the subject hold the l)ridge of one key in the position of closure. Shield the other key and apparatus from the subject by a large card])oard. Let the observer spin the drum and suddenly light the lamp by closing the bridge of the second key. The subject should open his key as soon as he perceives the light. Determine the average reaction time of several tests of this kind. 165 166 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 3. Reaction to Sound. — Arrange in series 2 or 3 dry cells, a simple key, a signal, a hammer, and a metal plate. Arrange to record the movements of the signal and of a tuning-fork. Let the subject hold the ke}' closed. Let the observer spin the drum and sharply tap with the hammer upon the plate, thereby making the circuit. Let the sub- ject open the simple key as soon as he hears the sound. Determine the average reaction time of several tests of this kind. 4. Reaction Time with Choice. — Arrange the electric apparatus for stunulation with single induction shocks and insert a signal and two simple keys in the primary circuit. Connect the secondary coil with a rocking bridge or mercury pole changer, and, in turn, each pair of connectors with electrodes. Let the subject hold the electrodes to his tongue, one on each side of it, and instruct him to open his key only when the right side of his tongue has been stimulated. Shield the apparatus by a large cardboard. Set the rocking key for stimulation of either side of the tongue. Spin the drum and close your key. Re- peat several times, changing the point of stimulation, so that the sub- ject is forced to judge which side has been stimulated. Does choice prolong the reaction time? 5. Patellar Reflex Time. — Let the subject be seated and cross his legs. Adjust to the thigh of the crossed leg a rubber cuff, and connect the latter by means of rubber tubing with a recording tambour. Ad- just a tuning-fork upon a separate stand and arrange it to register its vibrations from left to right, i. e., against the direction of rotation of the drum of the kymograph. Spin the drum and tap the patellar ligament of the subject, while he endeavors to reinforce the patellar reflex by simultaneous efforts. The record of the tambour will show two oscillations, namely, a wave due to the blow upon the ligament and one caused by the contraction of the muscles of the thigh. Draw an ordinate at the beginning of each wave, and determine the time which has elapsed between the moment of stimulation and the reaction. 6. Reflex Winking Time. — Connect the upper eyelid of the subject by means of a fine thread and soft wax with a recording lever. Insert a signal in the primary circuit of an induction apparatus, and place the writing point of the signal vertically below that of the recording lever. Allow a tuning-fork to record below the signal. Place upon the lower eyelid a pair of stimulating electrodes. While the drum is revolving at a rapid rate stimulate with a single make or break shock of suitable strength. Draw ordinates and measure the interval between the mo- ment of stimulation and the moment when the upper eyehd began to react. LESSON XXXVI THE SENSE ORGANS CUTANEOUS AND MUSCULAR SENSATIONS 1. Histologic Examination of Tactile Corpuscles.— Place difForont tactile corpuscles under the low and high powers of a microscope and study their structure. 2. Touch Localization. — Touch the skin of the hand of the subject with the pointed end of a pencil, his eyes being kept closed throughout this experiment. Let him then place the l)lunt end of a pencil upon the area stimulated. Measure with a millimeter scale the error made by him. Repeat the foregoing experiment upon the forearm and cheek of the same subject. Touch the skin of the subject twice in quick succession, selecting for the two stimulations either precisely the same point, or two points lying close to one another. Let the subject state whether two areas have been stinuilated or only one. 3. Touch Discrimination.^ — By touching different areas of the sur- face of the hand, arm, and face with the points of a caliper ascertain how Fig. 100. — Esthesiometer with Gu.\rded Points. (Stirling.) widely this instrument must be opened in order that its points may be felt as two. Record in millimeters the results for each part stimulated, and compare them, paying special attention to the relative sensitiveness of the lips, cheeks, tongue, and the flexor and extensor surfaces of the arm. In the latter case observe that the sensibility increases in the direction of the fingers and also in the transverse direction rather than along the longitudinal axis of the limb. 4. Action of Cocain.— Press the point of a needle upon the tongue and note the degree of pressure necessary to produce a distinct sensa- tion of pain. Touch this area with the end of a camel's-hair brush, moistened with a 4 per cent, solution of cocain. What changes do you note? 5. Aristotle's Experiment. — Cross the right middle and index-fingers and place them upon the palmar surface of the left hand. Place a small shot between them and roll it about in the palm of the hand. Describe the sensation. 167 168 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY Cross the fingers in the same way and rub them against the tip of the nose. Describe the sensation. Annotation. — Ordinarily the tactile corpuscles upon the outer surface of the index-finger and inner surface of the middle finger act in unison, producing har- monious impressions. If the corpuscles upon the inner aspect of the index-finger are now brought in relation with those upon the outer aspect of the middle finger, two impulses must result in consequence of the stimulation of dissimilar tactile points. 6. Peculiar Phenomena and Illusions of Touch and Pressure. — Place the cross-section of a tube against the skin of the forearm. An impression of a transversely oval object is produced thereby. Separate the points of a compass about 2 cm. and draw them in a straight line downward across the skin of the forearm, wrist, palm of hand, and fingers. A sensation of a single line opening up into two is produced; moreover, these lines appear to be more widely apart at the wrist, to converge in the palm, and to diverge toward the tips of the fingers. Close your eyes, and follow the circumference of a round object first with a short rod and then with a long rod, held between your fingers in the usual way. The object will appear to be much larger when out- lined with the short rod. Apply the points of a compass simultaneously to the skin of the subject, his eyes being closed. Allow the subject to obtain a clear im- pression of the distance between the points. Apply only one of the points, and move this point rapidly an equal distance across the skin. In the former instance the distance will seem greater. Make a knot in a coarse thread about 30 cm. in length. Allow the subject to hold the knot between the thumb and index-finger of his right hand, his eyes being closed. Pull the thread through his fingers first slowly and then more quickly. Is the subject capable of estimating the length of the thread? Apply a comb to the dorsal surface of the subject's hand, his eyes being closed. Ask him to indicate the length of the comb actually applied. It will appear shorter to him than it really is. Draw the same distance of comb slowly across the surface. It will now seem longer than it actually is, because movement leads to an exaggerated sensation of length. Draw the head of a pin rapidly to and fro across the skin of the fore- arm of the subject, his eyes being closed. The subject will perceive the motion some time before he is able to determine its direction. Touch your forehead with your finger. The finger ''feels" the fore- head. Rapidly draw the finger across the skin of the forehead. The sensation will now be referred to the forehead. 7. Adaptation to Touch Sensations. — Place an object, such as a cork, upon the skin of the forearm. The initial sensation of pressure will gradually give way to an indifferent sensation. Dip your index-finger into a tube filled with mercury. Presently THK SENSE ORGANS 100 only the sonsation of prossuro at the surfaco of tho morcury will fomain behind; in fat-t, eventually even the latter will appear only when the finger is moved. 8. Touch Sensations Modified by Movement. — Touch the skin of the dorsal surface of the arm with the tij) of \()Ui' index-finj^er. Note the quality of the sensation. Draw the finger slowly across this surface. The sensation of touch is changed into one of stroking, due in all prol)- ahility to the activation of the nerve plexuses investing the roots of the hail's. Feel an}' surface with the tip of your index-finger. Draw the finger across the surface. Note that the sensation of simple contact is now amplified hv s(Misations of motion and space. 9. Projection of the Sensations of Touch. — Hold a metal rod be- tween your fingers and draw its end across a roughened surface. The sensation will be referred to the end of the rod, i. c, be projected beyond the skin. Dip the elbow in cold water. The initial sensation of cold at the point of contact with the water will soon give way to a similar sen- sation in the region innervated by the ulnar nerve. 10. Mechanical Stimulation of the Hot and Cold Spots. — Close your eyes and instruct the assistant to touch the tlorsal aspect of your hand with the blunt i)oint of a [x^ncil. In certain areas you will obtain a sensation of cold, and in others, of heat. These spots arc separated by areas in which no sensations of temperature are evoked. Allow the assistant to draw the point of a pencil slowly across the surface, noting that distinct points of cold flash out. Sensations of heat are not so easily elicited. 11. Thermal Stimulation of the Hot and Cold Spots. — Employ a metal rod, about 10 cm. in length and 1 cm. in diameter. Its pointed end projects from a covering made of rubber tubing. Cool the rod in ice-water and map out a circumscribed area upon the dorsal aspect of the subject's hand. Mark the cold spots with black ink. Warm the rod to 70° C. and proceed as before, marking the warm spots in red ink. Observe that the latter are less easily found and that their stimulation is followed by a long(M- latent period. 12. Chemical and Electric Stimulation of the Temperature Spots. — Apply objects of different heat-absorbing power to the skin, such as wool and a piece of metal. The latter feels colder because it gives rise to a greater loss of heat, thereby stimulating the cold spots. Rub menthol upon the skin of the hand or forehead. A sensation of cold is obtained because this agent renders the skin hyperesthetic. Identify a cold spot upon the dorsal surface of the hand. Employ two electrodes, one pointed and the other flat. The former is applied to the cold spot and the latter elsew'here upon the hand. Stimulate with a weak induction current until a distinct sensation of cold is ob- tained. 1.3. "After-images" of Temperature. — Place a cold coin on the 170 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY forehead or on the palm of the hand for about half a minute. Does the sensation of cold continue even after the coin has been removed, allow- ing the temperature of the skin to rise? Repeat this test with a slightly heated coin. 14. Acuity of the Temperature Sense. — Insert the index-finger in a beaker filled with water of 30° C. Raise the temperature of the water quickl}' a few tenths of a degree. How small a difference are you able to perceive? 15. Temperature Contrast. — Place the index-finger of your right hand in water of 40° C. and the index-finger of your left hand in water of 20° C. Wait a short time until the initial sensations of warmth and cold have become less intense. Transfer both fingers into water of 30° C. Note that the right finger feels cold because heat is lost by it, whereas the left finger feels warm owing to a certain stagnation of its heat. Place one index-finger in water of 32° C. and the other in water of 45° C. Wait half a minute and transfer both in water of 10° C. An- alyze the sensation. 16. Thermal Illusions. — Employ two disks of metal of equal size, one warm and the other cold. Place them successively upon the skin of the subject, whose eyes are closed. The cold disk will feel heavier than the warm one. 17. Pain Spots. — Map out the dorsal surface of the hand of the sub- ject with the point of a sewing needle, noting the points where a distinct sensation of pain is perceived. 18. Discrimination of Weight: Weber's Law. — Place a small box containing 10 shot upon the palmar surfaces of the tips of the middle and index-fingers of the subject. Support his hand at the wrist, and ask him to close his eyes. When he has obtained a clear impression of the weight, add or subtract shot until he notices a distinct difference. Repeat this experiment several times and obtain a mean value for the number of shot added or removed. Repeat this test with 30 and 50 shot respectively in the box. Tabulate the results. 19. Relation of Weight to Area Stimulated. — Place two objects of equal weight but unequal size upon the dorsal aspect of the subject's hand, his eyes being closed. Most generally, that weight will be thought to be heavier which presents a greater surface to the skin, i. e., stimulates the largest number of tactile corpuscles. Request the subject to lift three cylinders of equal weight, but unequal size, and determine which is the heaviest. The largest cylinder is usually thought to be the heaviest. 20. Illusions Relating to Weight. — Lift an object first rapidly and then slowly, and note that its weight seems less in the former instance. Lift a certain weight with one hand while clenching the other. The weight seems lighter in consequence of the simultaneous effort. 21. Simultaneous Movements.^ — Stand erect before a blackboard. Close your eyes and -draw with both hands placed at the same height two THE SKNSE ORGANS 171 leaf pattorns of equal size. Draw from left to rip;ht witii a "free hand" motion of the arms, produced hy simultaneous impulses directed eciually to the two sides. Note th(> relative siz(> and position of the figures. Repeat this experiment, but place one hand about 12 cm. above the other. Obviousl}', the nuisde sense is not well trained in the averap^e person. 22. Sensation of Motion at the Elbow. — Place the forearm upon a boartl which it is possible to move, thereby imitatinj^ the flexion of the forearm upon the arm. Close the eyes. While an assistant raises or lowers the free end of th(^ arm-board, state when >'ou perceive a dis- tinct motion of your forearm. How great an angular movement is necessary in order to produce a sensation of motion? 23. Paradoxic Resistance. — Fasten a weight to a string about 2 m. in length. Close your e3'es and grasp the string anywhere, suspending the weight in space. Quickly lower the weight upon a felt cushion. When contact is made a definite sensation of resistance arises, as if the hantl were supported by a rod. LESSON XXXVII THE SENSE ORGANS (Continued) TASTE, SMELL, HEARING 1. Structure of the Taste-buds.— Study histologic preparations of the tast('-l)U(ls. 2. Distribution of Taste. — Place a crystal of cane-sugar upon the tip of the tongue. Note that there is a definite latency caused by the fact that solid substances cannot be tasted. They must first go into solution. Place a crystal of cane-sugar upon the tip of the tongue and another upon its posterior area. Where is the sweet taste most pronounced? Employ a solution of sulphate of quinin (bitter), a 5 per cent, solu- tion of cane-sugar (sweet), a 10 per cent, solution of NaCl (saline), and a 1 per cent, solution of acetic acid (sour). Apply these solutions to different parts of the tongue by means of a camel's-hair brush, and observe wherc^ each is tasted most acutely. 3. "Threshold Value" of Taste.— Moisten the tongue with ^ tea- spoonful of a 1 : 1(300 solution of cane-sugar. Do you perceive a sweet taste? Rinse the mouth and repeat the experiment with solutions of the following strengths: 1 : 800, 1 : GOO, 1 : 400, and 1 : 200. Which solution produces the least perceptible sweet taste? How does the acuity of taste in smokers compare with that in non-smokers? 4. Taste Reaction of Single Papilla.— By using a lens select a fungi- form papilla near the tip. or side of the tongue. Apply to it the tip of a camel's-hair brush moistened with one of the fluids provided for this purpose, xdz., weak anrl strong solutions of cane-sugar, sodium chlorid, tartaric acid, and ciuinin. The subject should indicate the taste which he perceives. Does the papilla exp(>rimented with respond to more than one of the agents used? Test other papillae in the same manner. Explain. If a papilla be found which reacts to bitter, paint it with a solution of cocain. To another^ which is particularly responsive to sweet, api)l\- a saturated alcoholic solution of gymnemic acid. Note the result in each case. 5. Electric Stimulation. Inadequate Stimuli. — Connect two small zinc electrodes with a series of 4 chy cells. Apply one of the electrodes to the upper and the other to the lower surface of the tongue. An acid taste will be obtained at the positive and an alkaline one at the negative pole. The objection that electrolysis is the cause of these sensations may be met by employing non-polarizable electrodes. Moreover, even single shocks which cause practically no electrolysis, give rise to taste sensations. 173 174 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 6. Elimination of Sweet and Bitter. — Apply a 5 per cent, decoction of gymnema sj^vestris to a limited area of the tongue. Twenty to thirty seconds later rinse the mouth thoroughly and test the taste with the solutions used for Experiment 2. What solutions remain effective? 7. Structure of Olfactory Cells. — Study hitologic preparations of the olfactory area. 8. Distribution of Olfactory Cells. — Place a glass funnel over some odoriferous substance. Insert the tip of- the funnel first into the lower posterior and then into the upper anterior region of the nasal cavity. Which region is the more sensitive to the odor? Where is the olfactory area located? 9. Olfactory Latency. — Smell oil of cloves held close to the nose, and determine the time intervening between this act and the perception of the sensation. Give a reason for this latency. 10. Olfactory Fatigue. — Smell tincture of camphor, tincture of iodin, or oil of cloves with one nostril until the olfactory cells have been fatigued. Note the time it takes for the fatigue to set in and for the acuteness of smell to be re-established. 11. Qualitative Changes Before Exhaustion. — Inhale oil of cloves through one nostril and observe the changes which occur in the quality of the sensation before it ceases. 12. "Threshold Value" of Sounds. — Determine the greatest dis- tance at which the subject can still hear the tick of a watch placed on the level of his right or left ear, the other ear having been closed with cotton. To avoid inattention the subject should shut his eyes. When just at the threshold of audibility the sound varies greatly in its intensity. Place the handle of a vibrating tuning-fork upon the head. Note the intensity of the sound, and then remove the fork quickly before the sound ceases completely. Observe that the change to complete silence seems much greater than the apparent low intensity of the sound would justify. 13. Auditory Fatigue. — Insert the ends of a Y-shaped rubber tube into the openings of the ears. Place a vibrating tuning-fork upon the tube in such a way that the sounds seem equally intense to both ears. Remove the tuning-fork. After a brief interval occlude the tube on one side by pinching it, and place the vibrating tuning-fork in its former position. When the sound has nearly ceased to be audible, open the pinched tube. The sound now appears to be much stronger in the rested ear than in the other. 14. Location of Tones. — Place the handle of a vibrating tuning-fork upon the top of the head. In what part of the head does the sound seem to be localized? Close one ear and observe the change in the apparent localization of the sound. Explain this phenomenon. Note the effects produced by placing the tuning-fork upon different parts of the head. Place the tuning-fork upon the teeth. Close one ear and note the apparent change in the location of the sound. THE SENSE ORGANS 175 Place first the right side and then the left side of your head flat against a pillow. Do you hear the sounds of your heart? In which ear are they perceived most clearly? Give an explanation of this phenomenon. 15. Compound Tones. — Set in vibration a violin string fixed be- tween two points. Touch the center of the string with a rod. Observe that the original fundamental tone is now obliterated, the lowest tone being an octave higlici-. 1(). Observation of the Membrana Tympani in Man. — Fasten the reflector to Vour lorehcad, and duvet the rays from a lantern into the right external auditory meatus of the subject. With your left hand pull the external ear l)ackward and upwartl, and with your right hand insert the funnel-shaped tul)(>, taking great care not to injure the skin of the meatus or the membiana tympani. Concentrate the light upon this membrane by moving the reflector either nearer to or farther away from Membrana flaccida Posterior ligament Anterior ligament — /Jf— ~-Loy)g process of incus - End of manubrium of malleus Fig. 101. — Membr.\na Tympani, as Seen with the Otoscope. (Hcustnan.) the ear. Adjust the tube by tilting it, so that a view of the entire membrane may be had. The light should be placed about 60 cm. from the reflector, and the reflector about 17 cm. from the membrane. Near the upper anterior border of th(> membrane will be seen the short process of the malleus, the handle of the malleus extending down- ward and backward from the short process. Locate the "umbo," which is the most retracted area of the membrane, and identify the "pars flaccida," the "pars tensa," and the "annulus cartilagineus." 17. Pressure in the Tympanum. — Close the mouth and nostrils. Attempt to inspire, and swallow. Note the pecuUar sensation in the ears and the diminution in the acuity of hearing. Close the mouth and nostrils. Attempt to expire, and swallow, A similar sensation is produced. Show how these acts affect the pressure in the tympanum and the vibratory quality of the ear drum. 18. Models of the Middle Ear. — Examine such models as may be available for illustrating the action of the ossicles. 176 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 19. Observation of the Interior of the Larynx in Man. — Place a light near the side of the subject's head. Seat yourself in front of him, Fig. 102. — Diagrammatic Repre- sentation OF THE Different Parts of THE Ear. 1, Pinna; 2, external auditory meatus; 3, ear drum; 4, middle ear containing the ossicles; 5, eustachian tube; 6, vesti- bule of the internal ear; 7, auditory nerve; di^^ding into two branches, one of which innervates the cochlea, and the other the semicircular canals; 8, parotid gland. Lamp Fig. 103. — Diagrammatic View of the Internal Ear. 1, Tympanic cavity; 2, eustachian tube; 3, incus; 4, stapes; 5, vestibule of the internal ear (perilymph); 6, utricle; 7, central canal of the cochlea; 8, scala vestibuli; 9, saccule; 10, endolymphatic duct between saccule and utricle; 11, ampulla of semicircular canal; 12, canalis reuniens; 13, scala tympani; 14, helico- trema; 15, fenestra ovalis. Concave Mirror Fig. 104. — Diagram of Laryngoscope. {From Stewart's A Manual of Physiology, Wil- liam Wood & Co., Publishers.) and direct him to incline his head slightly backward, to open his mouth, and to hold his tongue forward with the aid of a handkerchief. Illumin- ate the pharynx of the subject by means of a reflector fastened to your TfIR SENSE ORGANS 177 forehead. Slightly warm the laryngeal mirror, and pass it into the subject's mouth, carrying the miri'or hoiizonlally backward until its back touches tlic base of the u\uia. Avoid pressure upon the uvula or contact with the other soft parts. Concentrate the light upon the mirror, and tilt the latter until a view is obtained of the interior of the larynx, remembering that the parts are seen inverted in the mirror. Identify the dorsum of the tongue, the slightly yellowish e|)iglottis with its "cushion," and the glosso-epiglottidean folds of nnicous mem- l)rane. Identify the white and shining "true" vocal cords, the pink or red "false" vocal cords, the arj^epiglottidean folds, and the mucous membrane covering the arytenoid cartilages and cartilages of Santorini. Observe th(> diff(M-(>nces in the form of the glottis: 1. During quiet ami forced respiration, 2. While the subject sings a low and a high note, and 3. While the subject sings th(> vowel sounds: A, E, I, O, U. LESSON WW III THE SENSE ORGANS (Continued) THE STATIC AND DYNAMIC SENSES 1. Dissection of the Ear of the Dog-fish. — Keniove the cartilage be- tween the eyes. Identify the diflerent parts of the brain. Proceed toward its hinder part, carefully reuiovinu; the cartilage from within outward. Having reached one of the semicircular canals, remove its upper wall as far as possil)le. Identify its membranous canal w'ith its ampulla. Follow this canal until it joins a meml)ranous sac, the utricle. Carefully expose the other s(Mnicircular canals. Open one of the am- pulla and itlentify the crista acustica, a transverse ridge carrying the sensory epithehum. Fig. 105. — Position' of the Three Semicircular Canals ix the Skill of the Pigeox. (Ewalrl.) 2. The Position of the Semicircular Canals. — Procure a human skull in which the semicircular canals have been exposed, /. e., the bone has been removed, leaving only the bony walls of the canals behind. In- side this shell lies the membranous canal containing endolymph and invested by perilymph. Hold the skull in its proper position and indicate by a diagram the position of these canals. How many are there and what position do they occupy toward one another? What planes in space do they cor- respond to? Diagrammatically represent the canals on the other side of the head, and compare their positions with those just sketched. Note that the canals are paired, comprising the following groups: the two horizontal 179 180 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY ones, the right anterior and left posterior, and the left anterior and right posterior. Identity the ampulla of each canal and determine its position. Tilt the skull in different directions, and state which canals are involved in any particular movement. 3. Model Illustrating the Action of the Semicircular Canals. — Secure a model, such as is represented in Fig. 106. Rotate the circular glass tube containing water. Observe that the tube moves first and that at this time the water is still stationary The bristles, representing the hair processes of the cells lining the ampulla, are deviated against the direction of the rotation. Presently the water will move with practically the same velocity as the tube. The hair processes then extend straight into the fluid. On stopping the tube the water will continue to move onward, deviating the hair processes in the direction of its flow. Fig. 106. — Diagrammatic Representation of a Model Illustrating the Deviation OF THE Hair Processes of the Ampulla. D, Disk rotated by hand; T, circular glass tube filled with water; B, bulbular enlargement containing a long camel's-hair brush, vertically placed. While a free movement of the endolymph is not possible, this schema illustrates at least the principle involved in the activation of the hair cells. 4. Acuity of the Dynamic Sense. — Sit upon a revolving chair. Close your eyes and lift the feet from the floor. Instruct the assistant to turn the chair a short distance. What canals are involved in this movement? Determine the number of degrees through which the rota- tion has taken place. Ascertain the least possible rotation which will impart a sensation of movement. How would you rate the acuity of this sense? Bend your head forward. Repeat these tests. What canals are involved in this position? Is the sensitiveness of these canals toward this particular movement greater or slighter than that of the horizontal canals? 5. Rotation Effects in Mammals. — Place a rabbit in a long and narrow box which may be rotated around its vertical axis. Revolve the box at a moderate speed al^out ten times around its axis. Imme- diately tilt the box so that the rabbit slides out upon the table. Observe THE SENSE OROANS 181 tho nystagmus, the change in the diroction of the long axis of the ral)- bit, the change in the position (;f its head, and the compensating mus- cular movements made by it in order to retain its equilibrium. Do nut rejH'at this (experiment many times. Stantl erect and rotate a few times around the long axis of your body. Repeat this test with your eyes closed. Analyze the peculiar phenomena appearing when you cease rotating. In what direction ilo the walls move? How do you endeavor to counteract this impression? Since some persons are unusually sensitive to rotation, these experiments should be performed with some care. Do not rotate excessively until you have determined by a few rotations just how receptive you are. Repeat the rotation around yoiir vertical axis while you hold the head forward. Retain this position of the head at the end of the rota- tion. What canals are involved, and what is th(> character of the after- effects? Repeat the rotation around your vertical axis with the head bent forward. On ceasing to rotate, raise the head. Analyze the after- effect. 0. Rotation Effects in the Frog. — Place a frog under a bell-jar upon a revolving chair. Turn the latter slowly, noting that the frog bends its head and body against the direction of the rotation. Place a frog upon a somewhat roughened ])oard. Tilt the board and observe that the frog bends its body, and chiefly its head, against the inclination. Carefully force the frog to move and make it move across the edge of the gradually raised board and down its opposite side. 7. Equilibrium a Combined Sense. — Close your eyes and try to stand on one leg for one minute. Open your eyes and repeat this test. Employ a tactile sensation in addition to the visual. Note that you can retain your equilibrium with greater ease if the sensations from the labyrinth are augmented by other sensations. 8. Railroad Nystagmus. — While riding in a street car observe that the eyes of the person seated opposite to you are first deviated laterally and are then quickly moved into a median position. This nystagmus is not of labyrinthine origin, because it may be made to cease by accom- modation for a stationary object or by shielding the eyes. 9. Otolithic Cavity in the Frog. — Etherize a frog. Open its mouth widely and make an incision through the membrane covering its roof on the median side of the orifice of the Eustachian tube. Remove the surface layer of the bon(> of this region, thereby exposing a white otolithic mass. Thoroughly destroy this mass. Let this animal rest for some time, and then observe the position of its head and limbs. Rotate this frog and look for compensating movements. Does this frog possess a normal power of locomotion? How do its swimming movements compare with those of a normal frog? Destroy the otohthic cavity on the opposite side, and repeat the observations just made. Compare. LESSON XXXIX THE SENSE ORGANS (Continued) VISION 1. Dissection of the Eye. — Procure an ox eye. Having itlontificd the hds, conjunctiva, and different structures attached to the eyeball, isolate the optic nerve and cut away the muscles and fatty tissue. Open the anterior chainl)er of the eye by a transverse incision throufi;h the cornea. Study the physical characteristics of the aqueous humor. Remove the cornea and examine the iris and neighboring parts. By exerting a gentle pressure upon the outer coat of the eyeball force the Fig. 107. — Diagram of a Horizontal Section Through the Human Eye. C, Cornea; A, antorior cavity; P, po.stcrior cavity; L, Ions; J, iris; T, conjunctival sac; CL, ciliary ligament; CB, ciliary body; CM, ciliary niu.«cle; OS, ora serrata; CS, canal of Schlenim; R, retina; Ch, choroid; S, sclera; OA', optic nerve; A, retinal artery; B, blind spot; Y, yellow spot; OA, optical axis; VA, visual axis; H, hyaloid canal. lens through the pupillary orifice. Examine the lens, noting the degree of convexity of its anterior and posterior surfaces. Hold it over print. Place it under water. Can it be readily seen now? Explain. Open the posterior chamber widely, noting the differences in the color of the fundus. Explain. Identify the optic papilla and obtain an idea re- garding the location of the yellow spot. Note the characteristics of the vitreous humor. Examine histologic preparations of the cornea, iris, lens, and retina. 183 184 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 2. Formation of the Image Upon the Retina. — Place a fresh ox eye in a watch-glass. Make a small square opening in its upper wall directly behind the ciliaiy body. Direct the pupil of this eye toward an incan- descent lamp (optical lantern), the rays of which have been rendered parallel by the interposition of projection lenses. Vary the distance between the light and the eye until the rays have been made to inter- sect sharply upon the retina. Place a diaphragm with an upright arrow in front of the projection lens. Note the condition of the image. By means of a diagram show why the image must be inverted. Move the incandescent lamp (optical lantern) shghtly in different directions and observe the direction of the movement of the unage. Endeavor to thin the eyeball in the region of its posterior pole by removing the sclera. This means is frequently resorted to in order to obtain a clearer image. It illustrates the manner of focalizing an object upon the ground glass of a photographic camera. 3. Changes in the Size of the Pupil. — Light Reflex. — Observe the changes in the size of the pupil in a subject who alternately accom- modates for a window and a darkened wall. Cover the eye of the sub- ject with the flat of your hand for a few moments. Remove the hand. Note the constriction of the pupil. Again close one eye with your hand and observe the size of the pupil of the other eye. Suddenly re- move the hand. Note that the pupil of the other eye also constricts. The cornea acts as a planoconvex glass and gives a larger size to the pupil than it actually possesses. To show this take an ox eye, the cornea of which has been removed. Place a watch-glass in front of it. The pupil immediately appears larger. In order to show the movements of the iris in your own eye proceed as follows : With your right eye look at a uniform white surface through a pinhole in a card, preferably at the white shade of a reading lamp. Close your left eye. Obtain a concept of the size of the circular visual field. Open the left eye. The field becomes smaller and brighter, owing to the constriction of the pupil. Again close the left eye. The field gradually enlarges and is slightly dulled, owing to the dilatation of the pupil. Accommodation Reflex. — Observe the changes in the size of the pupil in a subject who alternately looks at objects near to and far away from his eye. 4. Changes in the Shape of the Lens. — Look at the eye of the sub- ject from the side, observing the position of the iris when accommodated for a far object. Ask the subject to accommodate for a near object. Note that the iris is forced forward into the aqueous chamber, owing to the fact that the lens now becomes more convex. Insert an ordinary watch-glass in a tube of black paper, its con- vexity being turned outward. A few centimeters behind it adjust a biconvex lens. Hold the tube toward a candle, and note the three images reflected from this system, viz., one from the watch-glass (cor- nea), one from the anterior surface of the lens, and one from the pos- THE SENSE ORGANS 185 terior surface of th(> lens. The first two iiiKi;;('s arc upright and the third inverted. In a thoroughly (hirkened room phicc your eyes about 2o cm. in front and to the h>ft of th(> rinht eye of the observed person. W"\\\\ your left hand hold a large cardboard direcll}- beside tiie right side of Fig. 108. -Reflected Images of a Candle Flame as Seen in the Ptpil of an Eye at Rest and Accommodated for Near Objects. (IVillianni.) your head. With your right hand hold a lighted candle .somewhat to the right of the cardboard, i. e., to the right of the visual axis of the eye of the observed person. Vary the position of the candle and approach the eye of the subject until you can clearly make out three unages, viz., one from the cornea, one from the anterior surface of the lens, and Fig. 109. — Diagram Illustrating Course of the Rays Through the Phacoscope. A, Observed eye; B, opening allowing acconiniodation for near and far objects; (', source of light; D, observer's eye; 1, images from cornea; 2, anterior surface of lens; 3, posterior surface of lens. one from the posterior surface of the lens. The gaze of the subject should at this time be directed straight ahead upon a distant object. Note the position and appearance of the images. Ask the subject to accommodate for a n(>ar object, but without changing his visual line. What changes do you note in the position and shape of the images? 186 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY Draw conclusions regarding the relative importance in accommodation of these refractive surfaces. Repeat these observations with the help of the phacoscope (Hehn- holtz). Annotation. — The phacoscope consists of a roughly triangular box. The ob- server's eye is placed in the apertiu-e at A and focalizes a far object through apertiu-e B. Orifice C contains two prisms, through which light is reflected upon the eye of the observed person. The observer notes the images tlirough the orifice D. The observed person then accommodates for the pin situated in aperture B (Fig. 109). Since the image from the cornea does not change its position or shape, the cornea does not alter its refractive power. The inverted image from the posterior surface of the lens undergoes a very slight change, showing that this refracting surface remains practically unchanged. Contrariwise, the image from the anterior siu-face of the lens becomes more rounded and moves toward the corneal image. This change proves that this refracting siu-face suffers the principal change in ac- commodation. 5. Wabbling of the Lens. — Gaze upon a Hght wall or ceiling. Do you notice black dots traversing the visual field (muscse vohtantes)? If you do, quickly accommodate for a near object and note that the spots execute a jerky lateral movement. This fact indicates that ac- commodation relieves the tension under which the lens is ordinarily held and allows it to deviate somewhat from its optical axis. This phenomenon constitutes the so-called wabbling of the lens. 6. Formation of the Retinal Image. — Accommodate for a light ob- ject situated about 6 m. from the eye. Hold the index-finger of your right hand in the visual axis of this eye. Draw a diagram to show why the finger appears indistinct. Repeat this experiment, but accom- modate for the finger. Draw a diagram showing why the far object is not clear. Look at a window through wire netting held about 25 cm. in front of the eyes. Later on accommodate for the netting. Explain. 7. Scheiner's Experiment. — Make two small holes in a card at a distance of 4 mm. from one another. Close one eye and hold the open- ings in front of the pupil of the other eye. Accommodate for a pin held about 18 cm. in front of the eye. The pin is seen single. Now, accommodate for a pin held at a distance of 60 cm. from the eye. The far pin is seen single and the near pin double. Close the left opening in the card and observe which image disappears when accommodating for the far pin and which when accommodating for the near pin. Draw diagrams showing the course of the rays, and explain the peculiar blocking of the images following the closure of one or the other of the openings in the card. The psychic element in vision is also clearly betrayed by the follow- ing experiment: With the left hand hold a card bearing a pinhole about 3 or 4 cm. in front of the eye. The other eye should be closed at this time. With the right hand bring the head of a pin from below into the field of vision, adjusting the pin as close as possible to the pupil. Note THE SENSE ORGANS 187 that the pin appears to enter the visual field from above. Draw a diagram to illustrate the course of the rays and explain this peculiar phenomenon. 8. The Emmetropic Eye. — Adjust the optical box at a distance of about 15 cm. from the optical lantern. Obtain parallel rays by placing the tin tube containing the projection lenses in front of the incandescent light. Lessen this bundle of light by a diaphragm, Ix'aring the outlines Fig. 110. — Optical Lantern and Box. {Harvard Apparatus Co) of the letter L. Close the round opening in the optical box by a fiat piece of window glass (cornea). In the holder directl}' behind this opening place a convex lens of 10 cm. focal distance (10 diopters). Arrange the solid black screen (retina) near the center of the optical box. Close the box with a large plate of clean glass and burn a small amount of Japanese incense in the box. ]\Iove the optical box as well as the screen (retina) until a perfectly clear image of object L is obtained upon the latter. 188 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 9. Circles of Dispersion. — j\Iove the screen farther forward and then farther backward. Note that the rays now strike the retina widely apart, i. e., thej^ form a dispersion circle upon this receptor. The same end may be attained by moving the lantern either farther away or nearer to the optical box (lens). Draw diagrams showing the course of tlie rays under these two conditions. 10. Near Point. — Again adjust the screen (retina) in such a way that the rays of light emitted b}^ object L are brought to a sharp intersecting point (emmetropia) . With a ruler determine the distance between object L and the lens of the optical box. This distance constitutes the anterior focal distance of this lens and indicates the position of its near point. Move the lantern closer to the optical box. Observe that the rays immediately pass into dispersion and finally leave the posterior surface of the lens very divergently, illuminating the screen widely. A precise focal point cannot be obtained if the object is situated inside the near point. 11. The Ametropic Eye. Hypermetropia, Myopia. — Construct an eye that is too short. To accomplish this end move the screen 2.5 cm. in front of the position occupied by it when the eye was emmetropic. This adjustment simulates the condition of hi/permetropia or far-sighted- ness. Theoretically speaking, the focal point of these rays lies behind the screen. In order to render this eye emmetropic place a convex lens in front of the aperture in the box (cornea), its strength being just sufficient to converge the rays so that they intersect upon the screen. A lens of 2 D. should accomplish this end. If a number of different lenses are available, other degrees of hypermetropia may be established. Construct an eye that is too long. To accomplish this end move the screen a distance of 2.5 cm. behind the position occupied by it in the emmetropic eye. Note that the intersecting point of the rays now lies in front of the screen (vitreous humor) and that the rays then diverge and strike the screen in dispersion. This condition is known as myopia or near-sightedness. In order to correct this condition interpose a concave lens in front of the optical box (cornea). The entering rays are thereby rendered more divergent, so that they are focalized exactl}^ upon the retina. A —2 lens ( — 2D.) will accomplish this end, provided the degree of myopia which has been established is not greater than specified. Draw diagrams to show the manner of refraction in hypermetropic and myopic eyes, and also indicate how these errors may be corrected. At the close of this exercise replace every lens in its proper paper envelope. LESSON XL THE SENSE ORGANS (Continued) VISION 1. The Ametropic Eye. Astigmatism.^ Adjust the optical lantern and box to I'oiin an onnnotiopic eye. Insert the diaphragm with the 2 mm. aperture in the opening of the optical lantern. Place a beaker with water directly in front of the cornea. Note that the image now simulates a vertical line. Close the top of the beaker by means of a small piece of cardboard. Hold the beaker between your thumb and index-finger and place it horizontally in front of the cornea. Note that the image now simulates a horizontal line. Draw a diagram to show the course of the refracted parallel rays. Repeat the preceding tests by holding a cylindric lens in front of the cornea, first with its greatest curvature adjusted in the vertical direction and then adjusted in the horizontal direction. By this means may be imitated the conditions of "mth-the-nde" and "ayainst-the- rulc" regular astig7}iatism. It will be remembered that the astigmatism which the phj'sician is usually called upon to correct is due to a faulty curvature of the cornea. In each case move the screen farther forward and backward and note the changes in the shape of the image. Explain these changes by means of a diagram. By means of a cj-lindric lens establish the condition of "with-the- rule" astigmatism. Move the screen so as to obtain as distinct an image as possible. Correct this condition by interposing in front of this cylindric lens another one of the same refractive power, but ad- justed in such a way that its greatest curvature comes to lie in the horizontal plane of the cornea. Establish and correct the condition of "against-the-rule" astigmatism in the same manner. Explain the fact that in the absence of a faulty curvature of the cornea, all round luminous objects, such as lamps and stars, do not appear round, but as radiate figures. 2. Chromatic Aberration.^ — Let the rays from the lantern emerge parallel through the 2 nun. aperture. Hold a lens of 10 D. about 15 cm. in front of the lantern, i. e., at a distance greater than the focal distance of this lens. Place a white sheet of paper in the path of the converging bundle of fight at a distance of about 15 cm. from the lens. Note the colors around the margin of the image. Correct this aberra- tion by covering the edges of tiie lens with a circle cut out of cardboard. How is chromatic aberration prevented in our eye? Make a pinhole in a card and place it upon cobalt glass. Close one eye and with the other gaze at a gas flame through the pinhole. The 189 190 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGi cobalt glass permits only the red and violet rays to pass. In accom- modating for the red rays a violet halo is obtained and on accommodat- ing for the violet rays, a reddish halo. On a black background place a strip of red paper and one of blue paper. The red appears nearer than the blue. Since the red rays are less refrangible, a greater effort at accommodation is required to focal- ize them. This gives rise to an erroneous judgment of distance. Place a heart colored red upon a bright blue sheet of paper. In a room lighted only by a candle hold the heart below the level of the eyes and move it gently from side to side. The red heart will then appear to flutter over the blue background. 3. Spheric Aberration. — Construct an emmetropic eye. Note that while the focal point upon the screen seems perfectly sharp, a close observation shows that this "point" is really drawn out backward. This distortion is due to the development of caustics, i. e., the rays of light traversing the marginal zone of the lens are focahzed somewhat behind those traversing its central area. Correct this defect by cover- ing the peripheral sphere of the lens with a circle cut out of paper. How is spheric aberration prevented in our eye? 4. Mechanical Stimulation of the Retina. Phosphenes.— Shut one eye and turn it inward. With the point of a pencil press gently upon the outer surface of the upper eyeHd. To what part of the field of vision is the yellowish circular image referred. Explain. Place a light in front of the eyes. Close them and move them quickly from side to side. When the eyes reach an extreme position, observe the rapidly disappearing bluish spot surrounded by a yellow halo. Obviously, this movement stimulates the retina around the optic papilla in a mechanical way. Note that mechanical stimuli are inadequate stimuh. W^hile they produce visual sensations, they can- not give visual concepts. Moreover, all retinal impressions are al- ways projected into the opposite visual field, i. e., into that part of the field with which that particular area of the retina is in functional relation. 5. The Field of Vision. — Fasten a sheet of white paper 60 cm. square upon a piece of pasteboard and make a small cross mark about 30 cm. to the right of the left margin of the paper. Let the subject rest his chin upon an iron support, and adjust the paper in such a way that his right eye is in a direct line with the cross mark. Move the verticall}^ placed paper close enough so that he cannot look beyond its edges. Let the experimenter fasten a small piece of white paper to a straw, move it horizontally inward from without, and mark on the white sheet the point at which this object becomes clearty perceptible to the person. Determine in this way also the boundaries of the visual field of this eye in the vertical direction, and in two or three intermediate directions. Outline the inner side of the field in a corresponding man- ner. Connect the different pencil marks to form a continuous hne. The visual field of the left eye may then be mapped out in a similar THE SENSE ORGANS 191 WE}'. Tho shoot of papor, Iiowovor, must thon ho adjustod in front of this eye and hoar a cross mark near its rifi;ht marfi;iii. If a perimeter is availahlo, the suhjoct should ho comfortal)ly seated at a tahle with his chin resting upon tho sujjport. Either the right or tho left eye shoukl thon ho focalized steadily upon the white dot in the center of tho somicircl(\ Tho metal arch l)oais a sliding path in which is moved the oi)joct, generally a small white scjuaro, from without inward, its movement heing indicated in degrees upon a scale inscrihed upon the arch. The point at which tho ohjoct hocomos first visihio Fig. 111. — The Perimeter. is then indicated upon a small piece of paper upon which different meridians have heen drawn out to correspond to those of the metal arch. Study the general outline of the visual field of each eye. Whj^ is it not round, hut oval, with its more pointed area toward the nasal side? Do 3"0U note any iiTogularities in its outline which cannot be ascrihed to a faulty technic? Enumerate the causes which might be held re- sponsible for such restrictions of tho visual field. G. The Fields for Colored Objects. — Proceed as described in para- graph 5, but insert red, blue, and green squares in the holder upon the 192 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY metal arch. While the subject gazes fixedh^ at the mark in the center of the arch, move these colors interchangingly from without inward along the different meridians of the eye. As soon as the subject per- ceives the color clearl}^, indicate this point in degrees upon the smaller chart. Eventually, connect all the points of the same color with one another. Fig. 112. -Perimeter Chart to Show the Field of Vision for a Right Eye When KEPT IN A Fixed Position. While the results differ materially with the saturation of the dif- ferent colors, most generally the red field is the largest, then follows the blue, and lastly the green. 7. Entoptic Phenomena Produced by the Tears. — Evoke a mild hypersecretion of lacrimae by holding a cut onion at some distance be- low the eye or imitate this condition by moistening the eyelids with fresh water. Close the eyelids somewhat, so as to deepen the layer of lacrimae upon the central area of the cornea. What effect has this upon refraction and the formation of the retinal image? Draw a dia- gram to show how refraction is affected under water. LESSON XLI THE SENSE ORGANS (Continued) VISION 1. The Near and Far Points of the Eye. — Hold a pin 50 cm. from your eyes antl move it slowly toward thciii until a point has been reached beyond which this object no longer produces a clear image. Measure the distance of this point from your eyes and determine whether, in accordance with your age, it is situated at a normal distance. Deter- FiG. 113. — Ophthalmometer. {Hardy.) mine the near point for each eye. In the emmetropic eye the far point lies at the horizon. Select a number of students with abnormal vision and determine the near and far points in each. Ascertain whether they are far-sighted or near-sighted. 13 193 194 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 2. Detection of Astigmatism. — Determine the near point for a pin held vertically and one held horizontally. Note whether the distances correspond. If not, what are your conclusions. Draw two lines 5 cm. in length and intersecting at right angles. Each right angle again bisect and each oblique angle again by other lines, until a radiate figure is obtained. Interpose this figure at the near point of accommodation. Note whether any of these lines appear blurred. Explain. 3. Measurement of Astigmatism. — Carefully study the construc- tion of the ophthalmometer (Helmholtz), and discuss the principle involved in this method of detecting and measuring astigmatism. 4. Visual Angle. — The visual angle is the angle formed by the lines drawn from the two extremities of an object through the nodal point of the eye (optical center of the lens). It is situated 7 mm. behind the cornea and 15 mm. in front of the retina. Since these lines traverse the nodal point unrefracted, the size of the retinal image may be ob- tained from this projection. Draw a diagram to show that, in order to subtend at the same angle, objects must be made increasingly larger, the farther they are removed from the retina. Thus, the letter A seen clearly at 6 m., would have to be ten times as large at 60 m. in order to be seen equally well. At a distance of 1 m. this letter should be 1 cm. in height in order to be seen clearly by the emmetropic eye. 5. Snellen's Test Tjrpes. — Determine the normal acuity of vision by distinguishing different letters subtending at an angle of 5 degrees. If the distance indicated can be exceeded or cannot be reached, the acuity of vision may be expressed as = -j- In this formula D stands for the given distance, at which the angle of 5 degrees is subtended, and d for the distance at which the letters can be recognized. Equip the ametropic person (myopic or hypermetropic) with lenses of different refractive power until able to recognize these letters clearly. 6. Ophthalmoscopic Examination of the Emmetropic Artificial Eye by the Direct Method. — Remove the projection-lens from the optical lantern. Adjust the emmetropic artificial eye for far vision at zero, and place it to the left of the lantern and on a level with your own eye. With the right hand hold the ophthalmoscope close to your right eye and about 30 cm. from the artificial eye. Make the visual axis of your right eye coincide with that of the artificial eye by keeping your head erect. Look through the opening in the mirror and throw the light into the pupil of the artificial eye. Accommodate your own eye for an imaginary object placed at some distance precisely behind the artificial eye. Gradually move your head toward the artificial eye until the mirror lies in the anterior principal focus of the latter, i. e., about 5 cm. in front of the cornea of the artificial eye. When the fundus of the artificial eye has become visible, find the optic disk. Draw a diagram showing the course of the rays of light. In case the observer is myopic or hypermetropic, he must first cor- THE SENSE ORGANS 195 rect his error in refraction by placinp; a suital)le lens behind the opening in the mirror. 7. Ophthalmoscopic Examination of the Ametropic Artificial Eye by the Direct Method.— Hciidcr tlic arliticial eye ametropic by pu-siiin^ its two parts closer together or by separating them more widely. Ex- amine its retina with the ophthahiioscope hold at a distance of from 30 to 50 cm, in front of it. Wiien the details of the funchis have lx>- come visible, move youi' head together with the of)hthalmoscope from side to side. In the hypermetropic eye the retinal vessels will appear Fig. 114. — Loring's Ophthalmoscope, with Tiltixg Mirkor, Complete Disk of Lenses from — 1 to — S and 0 to + 7, .\nd Si,"pplement.\l Quadr.\nt Containing = 0.5 .\ND ± 16 D. This Affords 66 Gl.\sses or Combinations from + 23 to — 24 D. to move in the same direction, and, in the myopic eye, in the opposite direction. Having in this way determined whether the Qyo is myopic or hypermetropic, measure the degree of tliis ametropia in the following manner: Place the ophthalmoscope in the anterior focal plane of the artificial eye, i. e., 5 cm. in front of its cornea. Illuminate the pupil and accom- modate your own eye for a distant point. If th(> artificial eye is myopic, place behind the opening in the mirror concave lenses of different strengths, until the lens has been found which renders a certain part of the optic disk — for example, a peripheral blood-vessel — perfectly 196 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY clear. If the artificial eye is hypermetropic, use convex lenses instead of concave. The focal power of the lens which is needed in order to be able to see the fundus of the eye of the subject clearly, is the lens needed to overcome the ametropia of tliis eye. In prescribing glasses for patients the strength of the lens is somewhat exaggerated, i. e., we prescribe in hypermetropia the strongest convex lens with which the observer is still able to see the details of the fundus, and in myopia the weakest concave lens. Why? Draw diagrams to show the course of the rays emitted by myopic and hypermetropic eyes. Also indicate how these conditions may be corrected by the interposition of suitable lenses. 8. Ophthalmoscopic Examination of the Artificial Eye by the In- direct Method. — Place a convex lens of 5 diopters behind the opening in the mirror of the ophthalmoscope, and hold the latter about 30 cm. in front of the artificial eye. Interpose at a distance of 5 cm. from the cornea of the artificial eye a +20 lens, held between the thumb and forefinger of the left hand. The rays which issue from the artificial eye are focalized in space after they have passed through the +20 lens. This image you study with the aid of the +5 lens. Draw a diagram to show the course of the rays emitted by this eye. 9. Skiascopy or the Shadow Test. — Hold the plane mirror of the ophthalmoscope in front of your eye and at a distance of 1 m. from the emmetropic artificial eye. Throw a beam of Hght upon this eye. That portion of it which falls upon the pupil is condensed on the retina and forms here an area of light which moves in accordance with the move- ment of the mirror. Consequently, the same condition is obtained here as when Hght is reflected against a wall by means of a mirror. Draw a diagram to show the real movement of the light upon the retina, note that its movement, as seen through the pupil, is the same as that of the hght on the face. Render the artificial eye myopic by drawing its halves farther apart. Place the mirror at a distance of 1 m. from the eye and tilt it gently. Note that the pupillary reflection now moves in a direction opposite to that of the mirror. Move closer to the eye until a point has been reached at which it is impossible to tell which way the light moves. Move still closer to the eye and observe that the light now moves with the rota- tion of the mirror. It is to be remembered that the myopic eye con- verges the rays leaving it. The point in space at which they intersect is the point of reversal. Obviously, distally to this point the light must move against, and inside this point, with the rotation of the mirror. Hence, skiascopy is simply an accurate method of determining this point of reversal. Draw a diagram illustrating the reflection in myopia. Render the artificial eye hypermetropic by bringing its halves closer together. Place your eye at a distance of 1 m. from the artificial eye. Move back and forth and note that the movement of the pupillary light is with the rotation of the mirror, no matter what position you occupy. This is due to the fact that the hypermetropic eye does not form a THE SENSE OROANS 197 point of reversal because it emits divergent rays. Now interpose a convex lens in front of the artificial ejx', therein' converging these rays and producing an artificial point of reversal and, so to speak, an artificial myopia. This lens accomplishes two things, namely, it neutralizes the divergence of the rays, and secondly, converges them sufficienfly to inter- sect. In order to ol)tain the degree of hypermetropia existing in this eye, determine the point of reversal as in normal myopia. Sul)tract the degree of myopia from the total strength of the lens. The remainder of the focal strength of the lens is the strength whicii is requiicd to over- come the hypeYmetropia. Draw a diagram showing the reflection in the hypermetropic eye. Select a number of students who are either near-sighted or far- sighted and determine the degree of ametropia in each. For example, if the erect movement is obtained as close as 55 cm. from the eye and the reversal as near as 80 cm., the point of reversal lies at a distance of about 67 cm. The myopia equals 1.50 D. Again, supposing that the movement of the hght in the pupil is found to be with the mirror at all distances, then interpose a 5 D. (convex) lens. If the point of re- versal is now at a distance of 1 m., 4 D. have been used to neutralize the divergency and 1 D. to render the rays convergent. Consequently, the degree of hypermetropia equals 4 D. LESSON XLII THE SENSE ORGANS (Concluded) VISION 1. The Blind Spot. — Make a small cross mark upon a white strip of paper. AboUt 8 cm. to the right of it make a black dot of the size of a large pea. Close your left eye and with your right eye gaze fixedl\' at the cross lines, allowing the dot to he in the outer visual fi(>ld. Bring the card closer to the eye until the dot disappears completely. Move the card still closer; the dot reappears. Draw a diagram explaining this defect in the visual held. What position does the yellow spot occupy in relation to the bhnd spot, antl how is this disturbance over- come in binocular vision. With yoin- right eye gaze at an object placed at a distance of 6 m. from you. Adjust the position of a fellow student in such a way that his head disappears conipletel}'. Make a small cross upon a white strip of paper. On each side of it and about 4 cm. from it make two black dots. Hold your left hand with its inner margin against the bridge of your nose. With your right hand hold the above figure in front of your eyes, and while steadily fixing the cross move the paper to and fro until you reach the cUstance at which both dots disappear. 2. The Contours of the Blind Spot. — Place the chin of the subject upon a support and adjust a slun^t of white paper about 50 cm. vertically in front of him. Ask him to gaze with his right eye at a small black dot upon the paper. Fasten a pin with a large black head upon a straw, and move this pin from without inward along the horizontal meridian of the eye. Indicate upon the paper the moments when the head of the pin disappears and reappears. Draw a vertical line about midway be- tween these two points and also several obUque hnes. Indicate upon all these lines the moments when the pin disappears and reappears. Connect these points to obtain a continuous line. Note that the field is irregularly oval in its outline, owing to the fact that the blood-vessels emerging from the optic disk are also insensitive to the light rays. 3. The Yellow Spot. — Having rested the eye for a minute or two, look through a fiat bottle containing a fairly strong solution of chrome alum. It is best to hold the bottle against a sheet of white paper. Since the pigment of the j'cllow spot absorbs the blue and green rays and transmits the others, the predominant tinge imparted to the area corresponding to the macula lutea will be red (purple). 4. The Retinal Blood-vessels. — While the subject turns his eyes laterally upon a dark wall, concentrate a beam of light from the optical lantern upon the exposed sclerotic coat directly behind the region of 199 200 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY the ciliary body. Give the lens used to concentrate the light a gentle rocking motion. The visual field will then appear to the subject as reddish 3'ellow, through which dark figures are passing. The latter assume the character of a network, in agreement with the branching blood-vessels (Purkinje's figures). Bj^ this means shadows of the blood-vessels are cast upon regions of the retina not ordinarity exposed to them. It is essential, however, that these shadows move, because the retina quickl}- adapts itself to continued stimulation. Make a pinhole in a card and hold it directly in front of one e3'e, the other being closed. Direct the visual axis upon a bright and evenly illuminated sheet of white paper placed in front of a lamp. Move the card from side to side. Vertically running figures will be apparent. Move the card up and down. Horizontal vessels will now be in evidence. Gaze at a white cloud through a thick piece of blue glass. Many bright points followed by shadows will be seen to traverse the visual field in a constant procession. The latter, in all probability, represent the red blood-corpuscles. 5. Direct and Indirect Vision. — Draw a figure upon a white sheet of paper, consisting of one central dot surrounded by six others at a slight distance from it. With your right eye fixate a small object at a distance of 50 cm. from you. Bring the aforesaid figure slowly into the line of vision. Note that the individual dots coalesce at some distance from the latter. They are severally in evidence only when the figure is brought into the visual line. Obviously, at this time, the rays of fight emitted by the figure are focalized in the fovea, i. e., in the region of the greatest acuity of vision. When',n added. Keep the ends of the intestinal segment above the surface of the solution. Observe the peristalsis. After about twenty minutes measure the quantity of fluid which has been secreted into the lumen of the segment. Since the quantity of the fluid surround- ing this loop has not been lessened, the secretion must have been formed from the material stored in the cells at the time of their removal from the body. 8. Influence of Adrenal Extract on Intestine. — Remove a piece of duodenum, al)out 10 cm. in length, and place it in cold Ringer's solu- tion. After a time cut off a piece 2 cm. in length and suspend it in a beaker filled with Ringer's solution. Connect its lower end with a weight placed upon the bottom of the receptacle and its upper end with a writing lever properly counterpoised. Place a small flame underneath the beaker and slowly raise the temperature of the fluid to 30° C. Start the recording drum and reg- ister the movements of this strip. Add 0.5 c.c. of adrenalin to the Ringer fluid (300 c.c). Note the effect upon the length of the strip (tonus) as well as upon its con- tractions. 9. Rapidity of Absorption and Elimination. — Into each of ten test- tubes pour 5 c.c. of thin starch paste and 2 c.c. of concentrated nitric acid. Swallow a capsule containing 10 grains of potassium iodid and rinse your mouth thoroughly. Increase the secretion of saliva by ch(>w- ing a piece of paraffin and collect at intervals of two minutes a quantity of saliva in the corresponding test-tubes. Rinse the mouth after each collection. How soon after ingestion can this agent be recognized in the saliva? 10. Histologic Examination of Preparations of Intestinal Mucosa. — Study the structure of a villus, mucous cells, and glands of Lieberklihn. LESSON XLVIII EXCRETION SECRETION OF URINE 1. The Drop Method of Registering the Flow of Urine. — Anesthetize a mammal and continue the anesthesia throupihout the followinfj; experi- ments: Perforin trachelotomy. Expose the left common carotid artery and insert in it a strai,u:ht glass cannida. Fill it with a solution of sodium carbonate, and connect it with the mercury manometer. Isolate the vagus nerve on the same side and place it in a loose silk ligature. On the opposite side expose the external jugular vein. Clamp it centrally; hgate it about 2 cm. distally to the clamp, and insert a straight glass cannula toward the heart. Fill this cannula with normal saline solution. Open the abdominal cavity in the linea alba below the umbilicus. Identify the bladder and the two ureters leading awa.y from its posterior surface. Insert a straight cannula in each (toward the kidney) and connect them by means of short pieces of ru))ber tubing with a Y-tube. Allow the end of the Y-tube to project beyond the edge of the board, at a distance of about 20 cm. above the spoon-shaped lever of the receiving tambour. Connect the latter by means of a long piece of rubber tub- ing with a recording tambour placed against the paper of the kymograph. Adjust the recording needle of the mercury manometer in such a way that it registers in the same ordinate as the writing lever of the record- ing tambour. Allow a chronograph to register seconds below these levers. 2. Normal Secretion of Urine. — Allow the kymograph to revolve at a moderate speed, and register the drops of urine secreted in relation with the curve of the blood-pressure. Remember that the formation of urine is often greatly lessened during ether narcosis. If this condition prevails in the animal used for this experiment, stimulate the flow in the manner described in paragraph 3. 3. Action of Glucose.^ — Prepare a concentrated solution of glucose (25 c.c). Filter it and draw 10 c.c. of the filtrate into a pipet. Con- nect the latter with the cannula inserted in the external jugular vein. Allow this quantity of glucose to enter the circulation, but slowly, so that the height of the blood-pressure is not altered. After a certain latent period drops of urine will be seen to enter the Y-tube at intervals. Observe the rapidity with which they are secreted. It is said that glucose stimulates the renal cells directly, giving rise to diuresis. Record the flow in relation with the blood-pressure. 4. Action of Sodium Chlorid.— When the diuresis produced by the glucose has nearly subsided, inject 100 c.c. of warmed saline solution. Register the flow of urine in the manner described above. Repeat the injection if the effect is not sufficiently decisive. 221 222 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY The injection of so large a quantity of solvent is prone to produce a material rise in the blood-pressure, thereby increasing the filtration pressure. For this reason the diuretic effect of sodium chlorid is fre- quently referred to this cause, in combination with hydremia and osmotic changes, and not to a direct stimulating action upon the renal cells. 5. Effect of Changes in Blood-pressure. — When an active secretion has been produced, stimulate the vagus nerve, thereby evoking a material reduction in the general blood-pressure. While the secretion of urine is then greatly lessened, note that the flow does not return to normal until a considerable time after the cessation of the stimulation. This fact tends to show that while the blood-pressure is an important factor in the production of urine, the secreting cells are not dominated by pressure alone. Dilute a 1 : 1000 solution of adrenahn sufficiently to cause a moder- ate rise in blood-pressure (2 c.c. of the solution to 20 c.c. of sahne). Register the flow of urine. Inject a small quantity of the aforesaid Fig. 123. — Effect of Stimulation of the Vagus Nerve Upon the Secretion of Urine. solution of adrenalin in the external jugular vein. Note that the flow of urine is greatly lessened thereby in spite of the high blood-pressure. This discrepancy is easilj'- explained, because the adrenalin constricts the blood-vessels of the kidney, and gives rise to a lessened vascularity of this organ and lessened secretory power of its cells. 6. Rapidity of Elimination. — Prepare a saturated solution of indigo- carmin. Inject 5 c.c. of this solution in the external jugular vein, not^ ing the moment of the injection. Again determine the time when this pigment appears in the urine. Kill the animal by an overdose of ether. 7. Dissection of the Region of the Kidney. — Identify the suprarenal bodies on each side. Carefully remove the left organ and expose the suprarenal plexus, greater and lesser splanchnic nerves, and fibers of the renal plexus. Open the pelvis of the kidney and study the characteristics of the cut surface of this organ. Identify the papillae, pyramids, medulla, cortex, and capsule. Remove the capsule. Is it closely adherent to the sub- stance of the kidney? LESSON XLIX EXCRETION (Continued) SECRETION OF SWEAT. BODY TEMPERATURE 1. Sweat Nerves. Am'stlu'tizc ii cut and iiuiintain the anesthesia until the animal has l)(>en killed by an overdose of ether. Expose the sciatic nerve, apply a ligature, and cut centrally to the liji;ature. Stiniu- late the distal end of the divided nerve with a quickly interrupted current of moderate intensity. Observe the beads of sweat collecting; upon the pads of the feet. Take the rectal tenipeiature of this animal. Apply a cloth moistened with warm water to the upper part of its body, thereby raising its body temperature. Sweating is also evoked by this means. Explain its purpose. Expose the external jugular vein and inject 3 milligrams of atropin sulphate. Note that the stimulation of the sciatic nerve now remains ineffective. The atropin paralj'zes the secretory nerve endings. Inject 10 milligrams of pilocarpin. Sweat will again be secreted, be- cause this agent excites the cells of the sweat-glands directly. Kill the animal by an o\'er(lose of ether. 2. Sweating in Man. — Procure a piece of paper sensitized with silver nitrate. Cleanse the pahn of the hand and after a certain interval appl}^ the paper to this surface. The orifices of the sweat-glands will be marked upon the paper as spots of silver chlorid. Apply to this area a small pad of cotton moistened with a 1 per cent, solution of atropin sulphate. Repeat the aforesaid test. Since atropin paralyzes the end- ings of the secret(My nerVes, this test will now remain negative. 3. Body Temperature.— Determine the body temperature of the subject by means of an ordinar}^ thermometer, the bulb of which is placed beneath the tongue. Ask the subject to close the lips. Observe the rapidity with which the temperature becomes constant. How long a time must the thcM-mometer be left iti situ before the mercury remains stationary? Determine the axillary temperature in the same manner. Compare. Place the bulb of the thermometer in the palm of the closed hand. Read the temperature. Compare, Wrap the hand in a thick woolen cloth. Why is the temperature now higher? Place the same hand in water of 20° C. for thirty seconds. Again determine its temperature. Explain the result. Request the subject to make thirty flexions of the arms and legs. Quickly determine the body temperature. For how long a time does the rise persist? 223 LESSOX L EXCRETION (Concluded) THE INNERVATION OF THE BLADDER. PILOMOTOR REACTIONS 1. The Function of the Hypogastric Nerves. — Anesthetize a cat and maintain the anesthesia throujihout the following experiments: Per- form tracheotomy. Open the alxlominal cavity by a median incision in th(> linea alba. Itlentify the urinary bladder, and raise its fundus sufficiently to expose the fatty tissue investing its cervical portion. By careful dissection isolate th(^ nerve-fibers which ascend from here to the fundus. Place them in shielded electrodes, and arrange the elec- tric apparatus for stimulation with a tetanizing current of medium strength. Insert a small hook in the top of the fundus of the bladder and connect it by means of a thread with the end of a writing lever (suspen- sion method). Counterpoise the lever so as to place the musculature of the bladder under a certain tension. Place cotton moistened with warm saline solution around the base of the bladder to protect the abdominal organs against evaporation and thermal influences. Allow the drum to revolve at a slow rate and stimulate the hypogastric fibers until a contraction of moderate height has been obtained. Cut one nerve and stimulate the central end of this nerve. Note that the bladder is now made to contract reflexly through the hypo- gastric center and intact nerve on the opposite side. 2. Pilomotor Efifects. — Unite the margins of the wound in the abdomen l)y a few sutures. Make a median incision through the skin covering the base of the tail and posterior extent of the vertebral column. Reflect the muscles. Clip away the spinal processes and adjoining laminse of several vertebrse near the base of the tail. Apply a cotton tampon until the bleeding has stopped. Incise the dura mater and identify the chorda equinse. Isolate several of its constituent nerve-fibers close to the base of the tail and place them in loose liga- tures. Smooth the hairs of the tail and place the latter upon a sheet of white paper. Note its volume. Stinnilate the nerve-fibers just isolated successively^ with a weak tetanizing current, until one is found which causes an erection of the hairs of the tail. Again smooth the tail and repeat this experiment. Explain the mechanism by which hairs are erected. Kill the animal by an overdose of ether. Repeat the stimulation of these pilomotor fibers after an interval of several minutes. Note that this mechanism remains effective for some time after death. 15 225 DEMONSTRATIONS TO BE GIVEN IN CONNECTION WITH THE PRECEDING LESSONS 1. (a) The dcterinination of the strcngtli of tlic make and break incliu'tioii shocks by means of the galvanometer. Pro- jection method. (6) The procUiction of acid in contracting nmscle. Acid fuclit;in method. 2. Electrotonus. Pfliiger'.s law of contraction. 3. The current of injury and current of action in muscle and nerve. Projection method. 4. The action of electric currents of high voltage. 5. (a) Extraction of the gases of the blood by means of the mer- cury pump. Baicroft-Haldane blood-gas apparatus. (6) ^'iscosinleter (Burton-Opitz). 6. (a) Projection of the spectrum. Formation of the bands of oxyhemoglobin and reduced hemoglobin. (6) The capillary circulation in the mesentery or bladder of the frog. Projection method. 7. (a) The action of the valves of the heart. Gad's method. (6) The vitelline area in the developing chick. 8. (a) The construction and action of different types of galvan- ometers. (6) Einthoven's string galvanometer and the action current of the heart. 9. Electrocardiography. Normal and abnormal records. 10. The registration of the sounds of the heart. Normal and ab- normal records. 11. The effect of increases in intracranial pressure upon the circula- tion and respiration. 12. The blood-supply of the intestines, demonstrated by means of the recording stromuhr of Burton-Opitz. Stimulation of the splanchnic nerve. 13. The vasomotor function of the spinal cord. Division and stimulation of the cord. 14. Fluoroscopic examination of the heart and lungs in man. 15. Perfusion of the excised mannnalian heart. 16. The application of the polygraph (Mackenzie). 17. Projection of the larynx. Stimulation of the superior and in- ferior laryngeal nerves. 18. Abolished and exaggerated reflexes in man in consequence of "high'' and "low" lesions of the nervous sj'stem. 19. (a) The decerebrated pigeon. (6) The decerebrated cat. 228 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 20. (fl) Lesions of the cerebellum in pigeons. (6) Cerebellar defects in man. Nj'stagmus. 21. (a) Stimulation of the semicircular canals in the turtle. (6) Lesions of the semicircular canals in pigeons. 22. Hemiplegia, aphasia, and hemianopsia in man. 23. The dissociation of the cutaneous sensations. Syringomyelia. Sensory anesthesia. 24. The accommodation of the eye of the frog, turtle, and fish. 25. (a) Large demonstration ophthalmoscope. (6) Astigmatism determined by means of the ophthalmotonom- eter of Helmholtz. 26. Myopia and hypermetropia displayed by means of a large Kiihne's artificial eye. 27. Fluoroscopic observation of the movements of the stomach and intestines in a mammal. 28. Removal of the thyroid and parathyroid bodies. 29. Removal of the suprarenal bodies. 30. (a) Dog with gastric fistula. (6) Diffusion demonstrated with the help of the apparatus de- scribed by Abel. WEIGHTS AND MEASURES* In the niPtric syt^ti-ni the liter is a unit (if caparity cquivalont to the volume occupied hv the mass of 1 kilogram of pure water at its maximum density. It is equivalent in volume to l.()()(M)27 cubic decimeter. Under this definition a milli- liter (0.001 of a liter) i.s different from a cubic centimeter by a verv minute frac- tion. However, as "cubic centimeter" is the term u.sed throughout medical literature we shall use it in this book, though both the U. S. and British Pharmacopoeias have adopted the term "milliliter" (.niil) i" its place. A. METRIC _, . , Approximate n eight: Writtin. i', 109 Ear. diagrammatic representation of, 170 middle, models of, 175 of dog-Hsh, dissection of, 179 Elbow, sensation of motion at, 171 Electric and chemical stimulation of temiK-rature spots, 169 currents, types, 2S stimulation of muscle, 23 Electrodes, non-polarizable, 29 stimulating, 27, 28 Electrotonus, G3 Elimination and absorption, rapiditj- of, 219 ^ rapidity of, 222 Emmetropic artificial eye, ojihthalmo- scopic examination of, bv direct method, 194 eye, 187 Entoptic phenomena produced bv tears, 192 iMjuilibrium a combined .s(>nse, 181 Ergograph, Mosso's, 51 si)ring, .52 Ergographic record of frog's gastroc- nemius, 52 Esophagus, division of, 207 isolation, 207 Esthesiometer, 167 Ether and chloroform, action on heart, 90 Excised heart, 82 Excitation wave of heart, transmission of, 81 Excretion, 221, 223, 225 Ivxercise, elTect of, on blood-pressure, 12S ivxperimental jaundice, 210 I'vXlensibilit V of muscle, 30 Exlnisystole, Si lOye, anielro|)ie, 18.S, 189 dissection of, 18.3 emmetropic, 1,S7 artiliciai, o|)litli;dmoscopic examina- tion of, by direct method, 191 near and i.ir points of, l'.)3 Eyes, associated niovemenls of, 2(M) Far and near points of eye, 193 Far-sightedness, 188 Fatigue, auditory, 174 muscle, 49 Fibrillation, 93 Field of vision, 190 Fields for colored objects, 191 I'"ish, respiratorj' movements, 146 Fistula, gastric, 218 Fleischl's hemoglobinometer, 74 Formation of image upon retina, 184 Friction key, 27 Frog, gastrocnemius of, ergographic rec- ord, .52 heart of, action current of, 60 otohthic cavity in, 181 rhcoscopic, 59 rotation effects in, 181 I''unction of roots of spinal cord, 103 Fusion, binocular, of dissimilar images, 203 of colors, 201 of gray and white, 201 of muscle contraction, 42 Galvanic current, 29 (Jalvani's experiment, .59 (lastric fistula, 218 (!astrocn(>mius, frog's, ergographic record of, 52 (iastro-enterostomy, 214 (ilossopharyngeal nc^rves, 141 (Jlueose, action of, 221 Ciower's hemoglobinometer, 75 Gravity, center of, 39 Gray and white, fusion, 201 Hearinc;, 173 com|)ound tones, 175 location of tones, 174 threshold value of sounds, 174 Heart, acceleration of, 88 action, arterial pulse and, relation be- tween, 129 of ether and chloroform on, 90 of muscarin on, 87 of nicotin on, 87 activities, respiratory activities and, relation between, 130 apex-beat of, 95 234 INDEX Heart dulness, area of, 95 effects of constant current on, 89 excised, 82 excitation wave, transmission of, 81 exposed, inhibition of, 114 frog's, action current of, 00 impulse, 95 inhibition of, 85 reflex, 88 isolated segments, 82 mammalian, beating, in situ, 91 dissection of, 90 rate of, 95 sounds, 97 staircase phenomenon, 89 Stannius' experiment, 89 stimulation of, 85 summation of stimuli, 89 ventricle of, isolated strips, 82 Heart-beat, conduction through ven- tricle, 83 effect of temperature on, 81 normal, 79 refractory period, 81 registration of, 79 Heart-block, 93 Hemin crystals, 78 Hemocytometer, 71 Hemoglobin percentage, estimation of, 73 Hemoglobinometer, Fleischl's, 75 Gowers', 75 Hemorrhage, 71 and saline injection, effect of, on blood- pressure, 111 influence of, on blood-pressure, 108 Hot and cold spots, mechanical stimu- lation of, 169 thermal stimulation of, 169 Hypermetropia, 188 Hypogastric nerves, function of, 225 Illusions, optical, 204 relating to weight, 170 thermal, 170 Images, dissimilar, binocular fusion of, 203 Indirect and direct vision, 200 method for ophthalmoscopic exam- ination of artificial eye, 196 Induction coil, 29 Inductorium, 30 Inflammation of lung, phenomena of, 147 phenomena of, 147 Inhibition of heart, 85 reflex, 88 of reflexes upon central paths, 157 Innervation of bladder, 225 Insufficiency, aortic, schema of, 602 mitral, schema of, 102 Intensity of light and quality of color, 202 Intestinal juice, secretion of, chemical stimulation of, 218 into excised loops, 219 mucosa, preparations of, histologic ex- amination of, 219 Intestine, influence of adrenal extract on, 219 osmotic power of, 217 Intracardiac blood-pressure, 115 Intrapleural pressure, 136 Intrathoracic pressure, effect of varia- tions in, on blood-flow through lungs, 147 Intraventricular pressure, schema of, 102 Irradiation, 203 Irritability of muscle, independent, 35 of nerve, 36 Isolation of esophagus, 207 of secretory nerves, 209 Isometric myograms, 34 Isotonic myograms, 34 Jaundice, experimental, 216 Key, simple, 26 Kidney, dissection of region of, 222 vasomotor supply of, 123 Lacteals, 215 Laryngeal nerve, inferior, 143 superior, 142 Laryngoscope, 176 Larynx, 141 interior of, in man, observation of, 176 Law, all-or-none, 82 Lens, changes in shape of, 184 wabbling of, 186 Levers, systems, 38 Light, intensity of, and quality of color, 202 reaction to, 165 reflex, 184 Localization, cerebral, 163 touch, 167 Loring's ophthalmoscope, 195 Lungs, blood-flow through, effect of variations in intrathoracic pressure on, 147 collapse of, 135, 136 effect of decreased atmospheric pres- sure on, 148 excised, 137 frog's, capillary circulation in, 147 circulation in, 147 inflammation of, phenomena of, 147 Mammalian heart, beating, in situ, 91 dissection of, 90 Mammals, rotation effects in, 180 Man, speed of nerve imi)ulse in, 56 vasomotor phenomena in, 123 Manometer, membrane, 115 Marey's pneiunograph, 129 tambour, 91 Mechanical stimulation of hot and cold spots, 169 INDEX 235 Mochanical stimuliitioii of niusclf, '2'A of ri'tiiia, HM) Mcilicolcfiitl tests for blood, 77 Mciiiliraiia tyiiiparii in man, ol)S('rva- tioii of, 175 Mciiihraiic inaiioiiictcr, IIT) Mcrciirv kt'V, 2() Metric wcifrlit, 229 exact ('(luivaleiit, 2)50 Microscopic examination of blood, 7.'i Mitral insufliciencv, schema, 102 stenosis, schema of, 102 Morse key, 2(i Mosso's er^fof^rapii, ol Motion, amel)oid, 21 ciliary, 21 sensation of, at elbow, 171 Motor nerve, irritability near renter, o!) jjoints, stimulation of, (il Mov(Mnent, touch sensations modified by, l()i) sinuiltanpous, 170 Miilier-Lyor fipiires, 205 Muscarin, action on heart, 87 Muscle, 21 action current, 59 contraction, compound, 43 clTect of excessive stimulation on, 49 of veratrin on, 49 on volume, 38 fusion of, 42 height of, relation of load to, 44 of strength of stimulus to, 43 influence of blood-supply on, 52 of chemicals on, 48 of temperature changes on, 47 method of registering, 33 of human, 51 ])aradoxic, 60 single, 41 siuiimation, 42 cross-section, relation of force to, 38 extensibility of, 36 fatigue, 49 human, law of unipolar stimulation, 65 indeijcndent irritability, 35 long and compact, comparison be- tween, 37 manner of attachment to bones, 39 movement, 22 j)ower, measurement, 37 smooth, 53 stimulation of, 31 direct. 23, 32 indirect, 23, 32 stimuli, 22 relation of strength of, to height of contraction, 43 subminimal summation of, 44 tetanus, 43 tissue, structure of different types, 21 tonus, 160 twitch, 41 warmer, 47 work, 45 Muscle work, addition of, 46 Muscular and cutaneous sensations, lt>7 Myograms, isometric, 34 isotonic, 34 Myctgrapliy, 25, 32 reconis of, fixation, 34 Myopia, iss Nkak and far j^oints of eye, 193 point, 18.S Near-sightedness, 1.S8 Negative after-images, 201 Nerve, 21 action current of, 60 anodic excitation, ()4 catliodic excitation, (>4 chorda tymj)aiii, function of, 210 conductivity of, 3(i currents, (il glossopharyngeal, 141 human, law of unipolar stimulation, 65 hypogastric, function of, 225 impulse, speed of, in cold-blooded ani- mals, 55 in man, 56 influence of temperature on, 59 irritability of, 3<) motor, irritability near center, 59 phrenic, 137 .secretory, isolation of, 209 stimulation of, 31 direct, 32 indirect, 32 sui)erior laryngeal, 142 supi)lv of submaxillarv gland, .schema illustrating, 209 sweat, 223 sympathetic, function of, 210 tissue, histologic study, 55 trigeminal, 141 vagus, influence of, 207 main trunk, 143 Nerve-fibers, conduction in both direc- tions by, 57 Nervous regulation of respiration, 141 .system, 1()3, 165 frog's dissection of, 1,55 localization of function in, 156 reflex action, 155 Neurons, histologic study, 155 Nicotin, action on heart, 87 Non-polarizable electrodes, 29 Nystagmus, railroad, 181 Observation of interior of larynx in man, 176 of membrana tymjiani in man, 175 Olfactory cells, distribution of, 174 structure of, 174 fatigue, 174 latency, 174 qualitative changes before exhaustion, 174 236 INDEX Ophthalmoniotor, 19;> Ophthalmoscope, Loriiig's, 195 Ophthahnoscopic examination of ametro- pic artificial eye by direct method, 195 of artificial eye by indirect method, 196 of ennnetro])ic artificial eye by direct method, 194 Optical illusions, 204 Osmometer, 217 Osmosis, 217 Osmotic power of intestine, 217 Otolithic cavity in frog, 181 Pain spots, 170 Pancreas, position of ducts of, diagram showing, 213 Pancreatic juice, collection of, 213 Paradoxic contraction of muscle, GO resistance, 171 Patellar reflex time, 16G Percussion, 139 of human stomach, 208 Perimeter, 191 Peristalsis, 215, 218 influence of salts on, 218 Phenomenon, Babinski, ehciting of, 160 Purkinje's, 202 Phlebograph, use of, 129 Phosphenes, 190 Photic stimulation of muscle, 23 Phrenic nerves, 137 Pilomotor reactions, 225 Pithing, 23 Placenta, study of, 146 Plasma, blood, relative amounts, 70 Plethysmograph, cardiac, 92 Pneumograph, Marey's, 129 Pohl's commutator, 56 Polarization, 28 Polygraphy, 129 Positive after-images, 200 Posture, effect of, on blood-pressure, 127 influence of, on blood-pressure, 107 Preparation of secretin, 213 Pressure and touch, peculiar phenomena and illusions of, 168 in tympanum, 175 intrapleural, 136 intraventricular, schema of, 102 secretory, 210 Primary current, 29 Protoplasmic streaming, 21 Pulmotor, 140 Pulse, arterial, character and velocity, 129 heart action and, relation between, 129 cause and velocity, schema ilhistrating, 103 schema of, 102 venous, character and velociity, 129 Pupil, size of, changes in, 184 Purkinje's phenomenon, 202 (ii'ATJTY of color and intensity of light, 202 Quickly interrupted current, 29 Railroad nystagmus, ISl Rapiditj' of absorption and elimination, 219 of elimination, 222 Reaction time, 1()5 with choice, 166 to light, 165 to sound, 166 to touch, 165 sensation, 165 Reactions, pilomotor, 225 Red blood cells, human, counting of, 73 corpuscles, enumeration, 70 simultaneous count, 73 Reflex, accommondation, 184 action, 159 study of, 155 centers for hind legs, localization of, 156 light, 184 time, 157 patellar, 166 winking time, 166 Reflexes, action, 159 exaggeration of, by means of strychnin, 159 in man, 159 inhibition of, by higher centers, 159 upon central paths, 157 spreading of, 157 tendon, in man, 160 Relation of weight to area stimulated, 170 Resistance, paradoxic, 171 Respiration, 133 accessory movements, 141 action of thorax in, 134 artificial, 140 center of, localization, 145 elimination of carbon dioxid in, 151 of water in, 151 forced, 135 frequency, 139 glossopharyngeal nerve in, 141 inferior laryngeal nerve in, 143 influence of carbon dioxid in, 140 larynx in, 141 main trunk of vagus nerve in, 143 mechanics of, 133 nervous regulation of, 141 normal, 134 placenta in, 146 self-regulation, 141 superior laryngeal nerve in, 142 trigeminal nerve in, 141 Respiratory activities, heart activities and, relation between, 130 movements in fish, 146 R(!tina, formation of image upon, 184 mechanical stimulation of, 190 Retinal blood-vessels, 199 image, formation of, 186 iNi>i:x 2:i7 Ulicoscopif froK, ^^ Hiva-K«><"«'i's spliynmomanoinotor, 121 Udots of spinal cord, fimclion of, Id.) Rotation i-ffcots in frofi, isl in inanunals, ISO Rotatory api)aratus for color disks, 2 '1 Sai.ink injection and licniorrliajic, clTi ct of, on hiood-pn'ssurc. Ill Saliva, secretion of, 2(Kt Salivary glands, dissection of, 211 Salts, inlliieyce of, on peristalsis, 21 S Scheiners experiment, ISIl Sciatic nerve, vasomotor action of, lis, 119 Secondary cinnMit, 2i) Secretin, action of, 21 1 prejiaration of, 2i:> Secretion hy bloodless ^laiid, 210 normal, of urine, 221 of l)ile, 21.") of intestinal juice into excised loops, 21!) of saliva, 2()!» of sweat, 22;i Secretory nerves, Lsolation of, 209 pressure, 210 Semicircular canals, action of, model illustrating, ISO position of, 179 Sen.sation of motion at elbow, 171 Sens(> organs, 1G7, 1715 Shadow test, 19() Shape of lens, changes in, 184 Simultaneous movements, 170 Single and double images, 203 Size of pupil, changes in, 184 Skia-copv, 190 Smell, 173 Smooth muscle, 53 Snellen's test types, 194 ' Sodium chlorid, action of, 221 Solidity, judgments of, relation of binocu- lar vision to, 203 Sounds, reaction to, 166 threshold value of, 174 Specific gravity of blood, 75 Spectroscopic examination of blood, 77 Spheric aberration, 190 Sphvgmograph, application of, 129 Didgeon, 129 Sphygmomanometer, application of, 125 Sphygmotonometer, 125 Spinal cord, roots of, fvmction of, 163 Spirometer, 133 Splanchnic nerve, greater, va.somotor action of, 121 Spot, blind, 199 contours of, 199 pain, 170 yellow, 199 Spring ergograj)!), 52 Staircase j)henoinenon, S9 Stannius' experiment, 89 Static and dj'namic senses, 179 Stenosis, aortic, schema f»f, 102 mitnd, schema of, 102 Stethograph. Mareys, I.'IO, 131 Sletliograpliy, 139" Stimulating ele<'tronce of, influence of, 203 Vocal cords, abduction of, 143 and adduction of, 143 Wabbling of lens, 186 Warmer, muscle, 47 Water, elimination of, in respiration, 151 Wave of deglutition, 207 Weber's law, 170 Weight, apothecaries', 229 exact equivalent, 230 discrimination of, Weber's law, 170 illusions relating to, 170 metric, 229 exact equivalent, 230 relation of, to area stimulated, 170 Weights and measures, 229 White and gray, fusion of, 201 blood corpuscles, enumeration of, 71 Winking time, reflex, Wintrich's modification of Hutchinson's spirometer, 133 Work, muscular, 45 addition of, 46 Work-adder, 45 Yellow spot, 199 Zollner's lines, 204 COLUMBIA UNIVERSITY LIBRARIES This book is due on th» date indicated below, or at the ^^■„„ nt a definite period after the date of borrowing, as ^rolided b; the'l1b«;'^es or by special arrangement with the Librarian in charge. C28(3-62)»OOM