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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

:t.

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 63

LESSON X

The Blood 67

The Coagulation of the Blood. Counting of the Blood-corpuscles 67

13

4i^a4;j

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 Mammahan 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 L^pon the Blood-pressure. Action

of Amyl Nitrite and Ardenalin. Hemorrhage 109

LESSON XXI

The Circulation (Continued) 113

The Effect of Division 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 XXIII PAGE

The Circulation (Continued) 121

The Vasomotor Action of the Greater Splanchnic Nerve. The Vascularity

of the Kidney. Oncometry 121

LESSON XXIV

The Circulation (Continued) 125

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-

raphy 129

LESSON XXVI

Respiration 133

Mechanics of Respiration . . . . : 133

LESSON XXVII

Respiration (Continued) 139

Stethography. Methods of Artificial Respiration. Pulmotor 139

LESSON XXVIII

Respiration (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 (Concluded) 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 21?

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 Preceding 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 Httle
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 accompHshed fact, and rightly so, because the
benefits which the students derive from work of this kind cannot be
overestimated. 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 must 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
repeatedly called upon to attend to the narcosis; to perform trache-
otomy; 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
him 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 experimentation 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 direct 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
cUnical 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 physiology 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

displayed 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 hundred and eighty hours. At the end of each period a
few minutes should be 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
efficiency 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 shculd 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-
otomy, 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 physiologic 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 be clearly made out.. What is the
position of the cilia when at rest and when contracting? Apply normal
sahne solution which has been sUghtly heated (25° C). Note its effect
upon the rapidity of the movement.

4. Structure of the Different 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

Tib. ant. long.

Sartorius

Add. magn.
Gracilis

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 23

Gently press the point of the scalpel transversely into this opening,
dividing the spinal cord. Introduce a seeker through the incision, 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 upon 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, but 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 chlorid (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.

(b) 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 achiUis. 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 energy is derived, as a
rule, from a Voltaic cell. As a generator may be employed a Daniell,
Grove, or Leclanche 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 commonly used
is a modification of the Leclanche cell. It

consists of a jacket of zinc lined with plaster P^ \^

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

25

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[>

^

H "^

• ,'.'• •'

li

y.

' ''■^■'

r^

.=—

Zf.-r--

■'.■•:•■.

V Cu

:%

Ca

-^

~~" —

)4i\

.

~~

- -k.

" ••••:"•'.:•

\^

"HI —

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 only upon the electromotive force but also upon the
resistance of the conductor. A short and thick wire 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
by 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 = -^

int. 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

27

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 mercury 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 be conveyed 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. Most 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 surrounded 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. (Harvard

Apparatus Co.)

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 sahne solution for some hours before
they are used so as to render the clay permeable (Fig. 7) .

4. The Different T3rpes 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 primary 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 inductoriimi. 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

PW=:.

I

Fig. 8. — The Inductorium.
/, Primary circuit and coil; //, secondary coil and circuit; K, key; j,

rupter; n, nerve.

automatic mter-

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 V, 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 primary current is made and broken
an induced current is momentarily developed in the secondary coil.

6. Stimulation of Muscle and Nerve — The Constant Current. — Con-
nect in series two dry cells and a simple 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 ampHtude
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 varying 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, while 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 turn 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 stimidation. 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
coUs 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 writing lever is fastened to
the stand below the muscle clamp. The tendo achilhs of the gastroc-

MUSCLE AND NERVE

33

nemius is then cut across and the muscle peeled off from the bones of
the leg. Next the latter 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 sUght weight is attached which is pre-
vented from extending the muscle by an after-loading device. The
electrodes are adjusted upon the upper part of the muscle (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 by 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 Muscular Contraction.
St, Stand for holding of clamp C and writing lever 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, S. 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

34 AJ)VANCED 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
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
^ ,„ . C5 drum. Never permit the tracing

Fig. 12. — Arrangement for Smoking the ^ ^ . ,i i- i

Paper. {Univ. of Penna. Lab. Outlines.) tO extend acroSS the Ime 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 reduced 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 blood. 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 carefully 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 paralysis has been es-
tabHshed in about fifteen to twenty minutes ex-
pose both sciatic nerves and place them in loose
Ugatures. 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 current
just sufficient to cause a well-marked contraction. If a
strong current is used, the paralysis must be more com-
plete, which requires a larger amount of curare.

Curare paralyzes the motor plates in the muscle, and hence muscle (4) cannot
be activated through its nerve, while muscle (3) can be. Both sciatic nerves conduct
normally, as can be shown by attaching the poles of a galvanometer to them. In
fact, in many instances the stimulation of the nerve on the normal side (4) produces
a contraction of the gastrocnemius on the side of the ligature. The elicitation of

35

Fig. 13. — Inde-
pendent Irritabil-
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 cm*are establishes a block between the nerve-fibers and the substance of the
muscle, i. e., 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,
fH while its nerve is drawn through the openings of a
H small gas chamber. Pieces of moistened filter-paper
H are placed fiat 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
Apparatits 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 (A), but permits its conductivity to remain practically
normal (B) . 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 irritability 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

lever may record down-strokes. Record the zero line or abscissa. Put
ten weights of 10 grams each successively into the scale pan, recording
each time the extension which the muscle suffers. Carefully remove the
weights one by one, allowing the muscle to register its curve of deten-
tion. Does the lever return to the abscissa?

Obtain a curve of elasticity from a rubber band under similar con-
ditions. Compare the results. Adjust the stimulating electrodes upon
the upper part of the muscle. 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 betweeA this curve and that
obtained under ordinary conditions? Explain.

ioK

\

/

n\

Fig. 15. — Extensibility and Elasticity.
A, Rubber band, and B, gastrocnemius muscle of frog successively loaded with 10-
gram weights. The second 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, i. e., it recoils until its abscissa
has been reached, provided 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 lift
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 heavy 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

Fig. 16. — Schema to Show that
Contracting Muscle Does Not
Change its Volume.

M, Meniscus of saline solution;
S, electrodes through which muscle
in receptacle is stimulated.

W

I ^

I Z^

7^

F

w

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
hfted 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 the contracting muscle does not interchange material with
the medium, but merely shifts 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. — Determine
the position of the fulcrum, weight and power in the cases of the biceps
in flexing the forearm, triceps 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. — With chalk outline the feet of a person when
standing erect. Approximately determine by means of a ruler, held
vertical, ihh 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 be 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 Penna. Lah. Outlines.)

the drum. Raise the drum of the kymograph from its friction-surface
by properly adjusting the screw in the top of the rod.

Let the tuning-fork register its vibrations (x^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

tJu 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
in Y^xs 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 stimulate the

Fig. 21. — Fusion and Tetanus.

S, 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 Stimulus 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.

i

1 1 .1 L

0 I 2, 3 t S" 6 7 8 9 to il /2, IJ I'^ fb-

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 views 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 (6) 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 obtain a summation. Load the muscle with a weight of 10
grams, and move the drum a distance of about 5 mm. to the left. Re-
peat the stimulation. Continue to load the muscle successively with

O \0 ZO 30 "fO 50 to ")0 80 <J0 joo

Fig. 24. — Influence of Load.
This muscle has been successively loaded with 10-gram 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 writing lever, I, 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, ^. 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 chamber 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 Muscle Waemer.
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

48 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

directly behind the Hne where the edges of the paper have been glued
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 little at a time. At about 43° C. the frog's gastrocnemius enters the
state of heat-rigor, and finally shortens maximally. Remove the

V\^^L^WVAAAAAAAAAAAAAA/\yVV\AAAAAAA/VVVx

Fig. 27. — Effect of Changes in Temperature on Mxjscular 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 current
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 veratrin.

Annotation. — In order to economize, the other gastrocnemius muscle of the
frog used for the preceding experiment may be immersed for a few moments in a
1 per cent, solution of veratrin. If it is then adjusted in the recording apparatus, it
will give characteristic veratrin contractions.

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. Arrange 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 paper 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

Fig. 29. — Fatigue of Muscle.

A gastrocnemius muscle of the frog stimulated successively 150 times. The 1st, oOth,

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
line 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 irritability, increase the
number of the contractions between the successive records. Since a very 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 procedure 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 (Contintjcd)

CONTRACTION OF HUMAN MUSCLE. INFLUENCE OF BLOOD-SUPPLY.

SMOOTH MUSCLE

1. Contraction of Human Muscle. — Adjust your right forearm in
the holder of the ergograph and place the middle finger in the sUng
supporting a weight of 2 to 3 kilos. Attach a pointer to the latter,
permitting 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 accomphshed
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 last 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.

Annotation. — 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 holder, 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 you
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

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m

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— ■ """"""^IM

^

T

Fig. 31. — Spring Ergograph. (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 placed in the same ordinate below the first. Pull upon the
strings to ascertain whether these levers interfere with one another.
Attach a weight of 10 grams to each. Make a small opening in the skin
over the upper part of each gastrocnemius muscle. Fasten the wires
from the secondary coil of the indue torium near the knee-joint — one
on each side. Then complete the circuit by uniting the gastrocnemii
muscles by means of a short piece of flexible wire.

Allow the drum of the kymograph to revolve very slowly. Record
the contractions of these muscles in the same ordinate until completely
fatigued. Note that the bloodless muscle is much more easily fatigued.
Explain.

5. Smooth Muscle. — Connect the secondary coil of the induc-
torium with the two outside posts of a moist chamber and attach two
shorter wires of medium thickness to the corresponding inside posts.

Fig. 32. — Moist Chamber.

*S, Stand; M, muscle; E, electrodes; L, writing lever; TM, signal; K, simple key; PS,

inductorium; K', short-circuiting key. (Stirling.)

Place a piece of filter-paper moistened with saline solution against the
inner surface of the glass cover. If the temperature of the room is
low, place a lighted alcohol lamp at some distance below the floor of the
moist chamber. Arrange the electric apparatus for stimulation with
single induction shocks.

Obtain a preparation of smooth muscle tissue and fasten it in the
clamp at the end of the horizontal rod in the moist chamber. To its
other end tie a silk thread, which is then brought through the orifice in
the floor of the chamber and fastened to the writing lever directly
underneath the latter. The writing lever should be adjusted in a
horizontal position by moving it up or down. Do not tighten the after-
loading screw, because the lever should at first be able to move upward
as well as downward. Fasten the ends of the short wires in the top of
the preparation. Adjust a chronograph underneath the point of the

54 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

writing lever. Allow it to register at intervals of two seconds. Allow
the drum to revolve very slowly and observe whether the muscle records
spontaneous contractions.

Draw the abscissa, and adjust the writing lever properly in this Hne.
Start at the beginning of the paper and stimulate the muscle with a
single break shock. If the preparation does not react to this strength
of stimulus, put in two or more shocks in quick succession — makes and
breaks, if you choose. Note the unusual length of the latent period.
Allow the muscle to relax fully, which, if the contraction possesses a
height of about 5 cm., may require the entire length of the paper.

Produce a summation of contractions by stimulating the muscle first
by means of a make shock and again with a break shock very shortly
after it has entered upon its period of relaxation. Naturally, if single
stimuli do not prove effective, employ a number of them in quick suc-
cession.

Employ a brief tetanic current, being careful not to contract the
muscle excessively, otherwise it might not be able to complete its period

Fig. 33. — Contraction of Smooth Muscle (Cat's Bladder).
L, Latent period; C, period of contraction; R, period of relaxation; time in seconds.

of relaxation before the end of the paper has been reached. Does the
character of the ''tetanic" curve of smooth muscle differ from that of
the curve obtained with single stimuli?

Annotation. — Preparations of smooth muscle may be obtained most conveni-
ently from the stomach of the frog and the stomach, intestine, and bladder of the
cat. No doubt, the bladder is best adapted for this purpose. Having opened the
abdomen in deep narcosis, the bladder is partially emptied and hfted out of the
wound. A long silk thread is then tied around the urethra at a distance of 1 to 2
cm. from the cervix of the bladder. The upper pole of the fundus is securely fastened
to a pair of needle electrodes and quickly placed in the moist chamber prepared
as described above. The silk thread is attached to the writing lever placed at a
convenient distance below the floor of the chamber. Do not injure the organ
mechanically, and moisten it from time to time wdth slightly warmed saline solution.

If the stomach is employed, cut a ring about 1 cm. in width from its pyloric
portion and fasten it in this position to the rod of the moist chamber. To its upper
pole attach one of the wires from the secondary coil of the inductorium. To its
lower pole attach the writing lever by means of a thread and also the other wire
from the secondary coil. The same procedure is to be followed in the case of seg-
ments of intestine. Be sure not to arrange them horizontally, because only the
circular muscle-fibers will give a marked movement of the lever. Under proper
conditions of experimentation the frog's stomach will yield contractions 2 to 3 cm.
in height.

LESSON VII
MUSCLE AND NERVE (Continued)

SPEED OF THE NERVE IMPULSE IN THE FROG AND MAN.
TION IN BOTH DIRECTIONS

CONDUC-

1. Histologic Study of Nerve Tissue. — Examine nerve tissue under
the low and high powers of a microscope. Employ horizontal as well
as transverse sections. Identify the axis-cylinder with its fibrils, the
medullary sheath, neurilemma, and nodes of Ranvier.

2. Speed of the Nerve Impulse in Cold-blooded Animals. — Place
two pairs of needle electrodes upon the rod in the moist chamber, and
connect them by means of wire of medium caliber with their cor-
responding binding-posts inside the chamber. Attach the wires from

Fig. 34. — Speed of the Nerve Impulse.
M, Muscle and nerve connected with writing lever W and two pairs of electrodes
N and F. The wires from inductorium J are connected with the pole changer P, so that
the nerve may be stimulated either near to or far away from the muscle.

the secondary coil of the inductorium to either pair of outside posts.
Underneath the moist chamber adjust a writing lever and electromag-
netic signal. The writing point of the latter should be adjusted in the
same ordinate as the point of the recording lever. The binding-posts
upon the signal are connected, on the one hand, with post 1 of the
inductorium and, on the other, with the simple key. From the latter
the wire is continued onward to the dry cell and subsequently to post 2
of the inductorium. Adjust the secondary coil to give induction shocks
of medium strength.

Make a muscle-nerve preparation, taking care not to injure the nerve.
Permit the lower segment of the spinal cord to remain attached to it.

55

56

ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

In the frog the cord extends as far as the ninth vertebra (at the dorsal
prominence). From here the tenth vertebra or urostyle passes back-
ward to the tip of the animal. It is best to open the abdominal cavity
in the median line and to remove the viscera. Make two transverse
sections so as to isolate the seventh and eighth vertebrae and roots of
the sciatic nerve of one side. Trace these fibers through the pelvic
aperture and down upon the dorsal aspect of the thigh. Isolate the
gastrocnemius muscle and place the coiled up nerve temporarily upon
it, but do not allow it to come in contact with the skin. Remove the
muscles of the thigh and cut the femur. Adjust this preparation in
the clamp of the moist chamber and lay the nerve across the widely
separated needle electrodes. Moisten the nerve with saline solution
and replace the glass cover. Test the two electrodes to see whether
both are effective.

The procedure to be followed is the same as that described previously
for determining the different periods of the muscle twitch. Having set

Fig. 35. — Pohl's Commutator. {Univ. of Penna. Lab. Outlines.)

the tuning-fork in vibration, the muscle is made to contract by closing
the key, the contraction may occupy a single rotation of the drum,
and must be repeated a number of times on far stimulation as well as
on near stimulation. Obviously, the current may be diverted into
either pair of electrodes by simply changing the position of the wires
at the binding-posts outside the moist chamber. A pole changer may
also be employed, but since this requires considerable lengths of extra
wire the change may be more conveniently effected in the manner sug-
gested above.

Draw perpendiculars to determine the length of the latent period
on near and far stimulation. Measure the distance between the elec-
trodes in millimeters. The time occupied by the nerve impulse in
traversing the measured stretch of nerve, corresponds to the difference
in the latent periods. Calculate the velocity of the nerve impulse.

3. Rate of the Nerve Impulse in Man. — A simple method for deter-
mining the speed of the nerve impulse in man not being available, the

MUSCLE AND NERVE 57

following procedure may be tried: Connect a rubber ball by means of
rubber tubing with a recording tambour, and request the subject to
hold the ball between his middle finger and thumb. Adjust an electro-
magnetic signal underneath the tambour in such a way that their
writing points come to lie in the same ordinate. Place a tuning-fork
fastened to a separate stand below the latter, its pointer being directed
against the rotation of the drum. The binding-posts of the signal are
then connected in series with a key, posts 1 and 2 of the ihductorium,
and a dry cell. From the secondary coil two wires are led off to a pair
of clinical electrodes. The large indifferent electrode is placed upon the
outer aspect of the arm of the subject, whereas the pointed one is held
against the region of the median nerve at the bend of the elbow.

Allow the tuning-fork to vibrate. Spin the drum with your left
hand, and close the key with your right hand. The moment of
stimulation will be recorded by the signal, and the moment of con-
traction of the flexor muscles by the tambour. Draw ordinates and

Fig. 36. — Conduction in Both Directions in Gracilis Muscle.

A and B, Segments of gracilis muscle divided by cut (C); S, point of stimulation; A^,

motor nerve and its branches.

determine the length of the latent period. Repeat this experiment
while the stimulating electrode is held over the brachial nerves above
the clavicle. Again determine the length of the latent period. The
difference in the latency between the two contractions corresponds to
the time consumed by the impulse in its passage from the region of
the clavicle to the elbow. Measure this distance, and calculate from
these data the rate of transmission of the nerye impulse.

4. Nerve-fibers may be Made to Conduct in Both Directions. —
Pith a frog and reflect the skin from the ventral surface of the thigh.
Cut transversely across the sartorius muscle near the knee and again
near the ilium. Isolate the muscle along its outer border and turn its
entire mass inward, so that its under surface is brought into full view.
Its nerve will be seen to enter near the middle of its inner border, where
it divides, sending branches toward both poles of the muscle. With
the scissors cut transversely across the different muscle-fibers well into
the triangle formed by the dividing nerve, so as to destroy the con-

58 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

tinuity between the two ends of the muscle. Beginning at one end of
the muscle, cut across the nerve terminals repeatedly, noting that the
fibers in the other end of the muscle then contract. Do not stimulate
with the electrodes, because this might invite the criticism that the con-
traction of the distant fibers is due to current skipping. The neigh-
boring gracilis muscle may also be used for this experiment.

Annotation. — ^This motor nerve conducts ordinarily in a centrifugal direction.
Since the stimulation of its terminals in one end of the divided muscle also gives
rise to a muscular response in the other end of the muscle, the impulses here gener-
ated must be conveyed in an afferent direction to the nearest divisions of these
efferent fibers, whence they proceed over the normally efferent fibers to the other
pole of the muscle. In this way a normally efferent fiber may be made to conduct in
an afferent direction. While it is probable that this nerve contains a certain number
of afferent neiu-ons, their presence cannot nullify the significance of this experiment,
because in the event of their activation their impulses could only be transferred to
the other end of the muscle by changing their normally afferent into an efferent
type of conduction.

LESSON VIII
MUSCLE AND NERVE (Continwed)

CONDUCTION IN NERVE. ACTION CURRENT OF MUSCLE AND NERVE.
STIMULATION OF MOTOR POINTS

1. Motor Nerve More Irritable Near its Center. — Pith a frog.
Expose . the sciatic nerve in two places, namely : (a) in the pelvis by
an incision between the urostyle and the ilium, and (6) in the thigh
(dorsal) near the gastrocnemius muscle. Insulate both segments care-
fully by means of narrow strips of rubber membrane. Arrange the
electric apparatus for stimulation with single induction shocks and de-
termine the least strength of make or break shocks which will give a
contraction in these two places. Compare the results.

2. Influence of Temperature. — Isolate the nerve just used in its
entire length, and place it upon a layer of cotton moistened with warmed
saline solution (40° to 45° C.). Apply the electrodes to this stretch of
nerve, and determine the threshold value of the make shock now re-
quired to evoke a contraction of the gastrocnemius muscle. Quickly
place the nerve upon a piece of ice, and again determine the threshold of
the least effective make shock. , Compare the results.

3. Galvani's Experiment. — Destroy the brain of a frog and cut away
the forepart of its body. Also remove the viscera, ilium, and urostyle,
but without injuring the roots of the sciatic nerves. The latter then
form the only connection between the lower end of the spinal cord and
the legs. Remove the skin from the latter and pass a copper hook
through the spinal segment. Suspend this preparation from an ordi-
nary iron tripod. Tilt the latter so that the legs come in contact with
the iron. Vigorous contractions will result whenever the legs touch the
iron. Explain, giving Galvani's as well as Volta's view.

4. Action Current of Muscle. Rheoscopic Frog. — Prepare two
gastrocnemii muscles with long segments of nerve. Place both upon
a plate at some distance from one another, allowing the end of nerve A
to rest upon the raised electrodes, and nerve B of the other muscle
lengthwise upon muscle A. Moisten this preparation with saline, but
do not allow any of this solution to flow upon the plate. Arrange the
induction coil for stimulation with quickly repeated shocks. Stimulate
nerve A briefly, noting that muscle B reacts simultaneously with
muscle A.

Annotation. — The impulses set up in nerve A by the stimulation produce a
contraction of muscle A. Since the different segments of this muscle do not react
simultaneously but successively, certain segments of it must be at rest and others
active. The active ones are galvanometrically negative to the resting ones, and
hence a difference in electric potential is set up in this muscle which is sufficient to

59

60 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

stimulate. Consequently, the response of muscle B is the result of impulses which
are produced in nerve B by the current of action of muscle A.

5. Action Current of Nerve. — Cut nerve A near the muscle and
place it alongside nerve B, so that the two overlap for a distance of
about 2 cm. Stimulate nerve A briefly and note that muscle B con-
tracts.

Annotation. — ^Nerve tissue shows a difference in potential in accordance with
the progressive activation of its segments. This current of action in nerve A is
responsible for the excitation of nerve B and the contraction of the muscle. The
fact that it is not due to a direct escape of the faradic current may be proved by
placing a ligature upon nerve B. This effectively destroys the response of the
muscle.

6. Action Current of the Frog's Heart. — The fact that the beating
heart generates an action current may be easily proved by exposing the
heart of a rabbit during deep narcosis and placing the nerve of a muscle-

FiG. 37. — The Rheoscopic Frog Prepatation.
Muscle A, stimulated through its nerve at *S, generates an action current which causes

muscle B to contract.

nerve preparation lengthwise upon its surface. The muscle then re-
sponds to every systole of this organ.

While the uninjured heart of a frog does not show this phenomenon
very readily, it may be obtained in the following way : Excise the heart
of a pithed frog and permit it to continue its activity upon a plate.
Cut off its apex and apply to it the cut surface of the sciatic nerve.
Place the more distant segment of this nerve upon the surface of the
basal portion of the ventricle. The muscle then twitches with each
beat of the heart.

7. Paradoxic Contraction. — The sciatic nerve of the frog divides near
the knee into its peroneal and popliteal branches. The fibers con-
stituting these two minor nerves are not formed by a splitting of the
distal axons, but arise separately from the spinal cord and merely lie
alongside each other in the nerve itself. Isolate the outer or peroneal
branch and divide -it near the knee. Stimulate its central end with a
brief faradic current. When a certain strength of current is employed

MUSCLE AND NERVE

61

the muscles supplied by the pophteal branch will be thrown into tetanus.
This result is not due to the transmission of the nerve impulse in a cen-
tripetal direction in the peroneal fibers and in a centrifugal direction in
the popliteal fibers, but to the excitation of the latter by the action
current developed in the former.

8. Nerve Currents. — Moisten a piece of koalin in normal saUne
solution and draw it out in two strips about 1 cm. in width and 6 cm.
in length. Bend each at right angles and hang them over the edge of
a plate of glass at a distance of about 6 mm. from one another. Place

HtgimMl'""^ \

U, flexor carpi ulnans

M. flex, digit, siibl.
(digit.- Indicis et
minimi)

^erv, ulnaris

M. palmaris brev.

M. abductor digit i

niin.

M. flexor digit, rain.

M. opponens digit.

luin.

M, lambricales<

M. flex. poll. brev.

M. adductor polllc. bre»-

Fig. 38. — Motor Points in Upper Extremity. (Howell.)

the nerve of a nerve-muscle preparation across these strips of clay,
allowing the muscle to rest upon the glass. Fill a small beaker with
normal sahne solution and dip the vertical ends of the clay into it.
The muscle contracts every time this contact is made, because it estab-
lishes a complete circuit for the interchange of its own demarcation
current.

9. Stimulation of Motor Points. — Connect the secondary coil of the
inductorium by means of wires of medium caliber with two clinical
electrodes (see Fig. 6, D and E), one of which is flat and the other
pointed. The flat, indifferent electrode is applied elsewhere to the

62

ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

integument, whereas the pointed one is used for stimulation. In order
to lessen the resistance, each electrode is equipped with a layer of cotton

!■ M. gluteus maximus

Nerv. ischiadicus

M. biceps fem. (cap. long.)
M. biceps fem. (cap. brev.)

N. peroneus
M, gastrocnem. (cap. extern.) / — #

M. soleus

M. flexor ballucis longus

M, adductor magnus
M. seraitendinosus
M. semimembranosus

N. tibialis

M. gastrocnem. (cap. int.)
M. soleus

M. fl ■>xor digltor. comm. longus
N. tibialis

Fig. 39. — Nerves and Motor Points in Lower Extremity. (Church and Peterson.)

moistened with saline solution. Localize different motor points, using
Figs. 38 and 39 as guides, and stimulate them with break shocks of
moderate intensity.

LESSON IX
MUSCLE AND NERVE (Concluded)

ELECTROTONUS. CATHODIC AND ANODIC EXCITATION. LAW OF
UNIPOLAR STIMULATION OF HUMAN MUSCLE AND NERVE

1. Electrotonus. — When a nerve is traversed by a constant or gal-
vanic current it undergoes certain physicochemical changes which be-
tray themselves in a change in its irritability at the points of entrance
and exit of the current. When the key is closed the excitation produc-
ing the nerve impulse is had at the cathode ( — ). The anode (+) is
depressed at this time. On opening the key the excitation is had at the
anode, while the cathode is depressed. The former condition is known
as anelectrotonus, and the latter as catelectrotonus. Obviously, during
the passage of the constant current, we obtain only the condition of
anelectrotonus, while the catelectrotonus de-
velops in the wake of the current, i, e., after
it has been broken.

Anodic Depression. — Fasten two holders
to the rod in the moist chamber and secure
in each a non-polarizable electrode. A con-
venient form of the latter is the clay-boot,
containing a rod of zinc. To begin with,
these boots should be immersed in normal
saline solution for a period of about twenty-
four hours to render the clay permeable to Fig. 40.— Method of
the electric current. They are then fastened CoNmT?oN^S^NERVE.^fSSer.)
in the holders. A zinc rod having been

placed in each, the remaining space is carefully filled by means of a
dropper with a solution of zinc sulphate (see Fig. 7).

Connect in series the binding-posts upon the rods, a key, and two
dry cells. Place a small tuft of cotton moistened with normal saline
solution upon each boot. Make a nerve-muscle preparation, and place
the nerve across the tufts of cotton, adjusting the distance between the
electrodes to suit the length of the nerve. Make and break the current
by closing and opening the key. With this strength of current a con-
traction is obtained only on the make of the current. Which electrode
is connected with the carbon (+) of the battery? Is the current ascend-
ing or descending in its direction?

Arrange the inductorium for stimulation with single induction shocks.
Apply the hand-electrodes to any part of the nerve and accurately de-
termine the strength of the make shock which is required to give a just
perceptible contraction. Now close the key in the circuit of the constant
current, and while this current is allowed to flow, stimulate the region

63

64

ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

of the anode of the nerve with a make shock possessing, as has just been
determined, a threshold value. The anelectro tonic diminution in the
excitability of the nerve will, in all probability, now render this stimulus
ineffective.

If not sufficiently decisive the depression may be increased by the
addition of another dry cell or two. It eventually becomes so strong
that it prevents the passage of the nerve impulse developed at the
cathode. In order to show this blocking effect place the anode near
the muscle, i. e., render the current ascending. On the make of this
current the excitation is developed at the cathode. The resulting nerve
impulse travels toward the muscle, but never reaches it, because it is
blocked by the area of depression in the region of the anode.

This point may also be proved by placing a drop of a solution of
sodium chlorid upon the nerve in the region of the anode, the anode

Fig, 41. — Method Used to Show Electrotonic Changes on Making and Break-
ing OF Galvanic Current.
K, Key for making and breaking of current; P, pole changer for making either end
of muscle (M) anodic or cathodic; D, clamp applied to muscle to destroy contraction
wave, but not wave of excitation; W, weight sattached to ends of muscle. These may
be displaced by writing levers.

being in this case situated near the muscles. Presently the muscles of
this leg will begin to twitch and finally become tetanically contracted.
Close the key in the circuit of the constant current. The excitability of
this region now having been diminished, the muscles will relax or at
least show a slighter degree of tetanus. Quickly change the wires so
that the cathode comes to lie near the muscle. The limb again becomes
tetanic. Repeat this test.

Knowing these facts, explain the third phase of the law of Pfliiger,
pertaining to the effect of the constant current upon normal excised
muscle and nerve.

2. Cathodic and Anodic Excitation.— When the constant current is
made, the stimulation arises at the cathode, and when broken, at the
anode. Suspend a sartorius muscle of a curarized frog vertically from

MUSCLE AND NEkVE 65

a hook. Place two non-polarizable electrodes against the opposite
borders of its upper portion. Make and break the current. When
made, the muscle deviates toward the cathode, and when broken,
toward the anode.

Slit this muscle longitudinally to near its upper end. Place a piece
of rubber membrane between its two halves and adjust a non-polariz-
able electrode upon the surface of each. On the make, its cathodic
half will contract, and on the break, its anodic half.

Isolate the opposite sartorius muscle with its attachments. Adjust
a screw clamp upon its central area and tighten it sufficiently so that
the wave of contraction is blocked without impairing the conduction
between its two ends. Suspend this preparation. Connect each end
of the muscle separately by means of a fine thread with a writing lever.
Adjust a non-polarizable electrode to each end. Make and break the
constant current. Note that the lever attached to the cathode moves
first on the make, whereas the lever attached to the anode rises first
on the break (Fig. 41).

3. Law of Unipolar Stimulation of Human Muscle and Nerve. —
Study the arrangement and, action of the apparatus, consisting of:
(a) 50 dry or moist cells connected in series, (b) a pole changer, and (c)
two clinical electrodes, one of which is broad and the other pointed.
The latter is equipped with a key, by means of which the current may
be made and broken. Moisten the felt lining of these electrodes with
saline solution, and apply the broad indifferent one to the shoulder.
The pointed stimulating electrode hold against the skin over the ulnar
nerve, near the internal condyle of the humerus. To begin with,
employ 8 cells, making and breaking the current while the anode is
over the nerve. Reverse the current, so that the cathode now lies
upon the nerve. Repeat the stimulations. Which stimulus is effective?

Increase the strength of the stimulation by the addition of several
cells (possibly 4 to 6). Repeat the stimulations while first the anode
and then the cathode lies over the nerve. Which stimuli are effective?
Add other cells, and repeat the stimulations. Tabulate the results and
compare them with those forming the basis of Pflliger's law of polar
stimulation. State why the latter is not apphcable to normal human
muscle and nerve" in situ f

Annotation. — Normal human muscle and nerve give the following results with
the constant current:

We%k.

Medium.

Strong.

ccc

CCC

CCC

ACC

ACC

AOC

AOC
COC

This shows that the cathodic closing stimulus is the strongest of all, and the cathodic
opening stimulus the weakest. Explain these results.

LESSON X
THE BLOOD

THE COAGULATION OF THE BLOOD. COUNTING OF THE BLOOD-
CORPUSCLES

L Preparation of the AnimaL — Place a cat under the bell-jar, con-
taining a small sponge moistened with ether, and carefully note its
behavior during the consecutive stages of the narcosis. When fully
under the influence of the ether transfer the animal to the operating
table, and apply a mask to its mouth, maintaining the anesthesia
throughout the following experiments.

Annotation. — Like in operations upon human beings, the depth of the narcosis is
ascertained by the intensity of the corneal reflex. On touching the cornea the eyelids
are closed. The quickness with which this reaction takes place serves as a guide in
administering the ether. If the reflex becomes sluggish in its character, give less
ether. If the reflex is abolished entirely, institute artificial respiration immediately
until the respiratory movements are again executed spontaneously. Also watch
the character of the respiratory movements, and note the size of the pupil, because
the abolition of the reflexes is accompanied by an extreme dilatation of the pupil.
The action of the heart usually ceases some time after the stoppage of respiration,
and hence it is possible to resuscitate the animal if prompt measures are taken.
The abdominal reflex may also be employed as a guide. On tapping upon the abdo-
men of the animal with the flat of the hand the abdominal muscles contract, render-
ing the abdominal wall tense. Obviously, if the narcosis has been carried too far,
this reaction does not take place, and the hand does not rebound.

A very efficient narcosis may also be established by means of urethane or chloral.
Chloretone is administered in doses of 0.25 gram per kilo of weight. Dogs should
receive | to ^ gr. of morphin and ^^o to tJtt gr- of atropin sulphate about thirty minutes
before ether is given. When chloral is administered the animal should be kept
warm, otherwise an excessive loss of heat may result. Ether narcosis is adhered to
in these experiments in order to give the student as much experience as possible
preparatory to his clinical work.

Tracheotomy: Insertion of Cannula.— Insert a cannula in the trachea
and connect it with a glass bottle containing a sponge moistened with
ether. Expose the right common carotid artery and left external
jugular vein and insert a straight glass cannula in the central end of
the former and the distal end of the latter blood-vessel.

Annotation. — ^The operation of tracheotomy is performed in the following man-
ner: Make a median incision in the skin of the neck, beginning about 2 cm. below
the larynx. Lay the scalpel aside and cut through the underlying fascia with the
scissors. With the help of two forceps separate the muscles in the median line^
until the trachea is brought into view. Separate the latter from the fascia surround-
ing it, and draw a loose cotton ligature around it. With your left hand raise the
trachea sufficiently to be able to make a transverse incision between two adjoining
rings of cartilage. Cut forward through two rings of cartilage. Quickly insert the
short arm of the tracheal cannula through this opening and tie the ligature around

67

68 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

it. To hold it firmly in place carry this ligature also around the free end of the
cannula. Connect the latter by means of a piece of large rubber tubing with the
ether bottle.

In inserting a cannula in the carotid artery proceed as follows: Identify the
sternocleidomastoid muscle. Loosen its inner border from the neighboring tissues
by means of the blunt end of forceps. Retract the muscle laterally outward. In
the bottom of the wound will be found the carotid artery, internal jugular vein, and
vagus nerve. The carotid artery is easily recognized as a pulsating blood-vessel
of considerable size. While your assistant retracts the margins of the wound, free
the artery from its sheath by means of two forceps. Place a silk ligature around
it and tie it. Grasp the ligatiu-e between the thumb and middle finger of your left
hand, and allow the artery to rest upon the tip of your index-finger. Apply to it a
spring clip at a distance of about 2 cm. centrally to the ligature. By means of scis-
sors held in your right hand make a transverse incision in the artery at a distance
of about 2 mm. centrally to the ligature. Insert the beveled end of a straight glass
cannula through this opening (toward the heart), and secure it by means of a silk
ligature.

In inserting a cannula in the distal end of the external jugular vein the same
procedure is to be followed. Make an incision along the outer margin of the sterno-
cleidomastoid muscle. Reflect the skin outward by separating it from the fascia

Fig. 42. — Tracheal Cannula, Fig. 43. — Artery Clamp.

(Harvard Apparatus Co.)

underneath. Cut close to the skin, because this vein lies very superficial and is
easily compressed. It is recognized by its large caliber and dark color which sharply
contrasts it against its investment of fatty tissue. Isolate it for a distance of 3 or
4 cm., and ligate it with a silk thread. Apply a spring clip about 2 cm. distally to
the ligature. Incise it transversely in the manner just described and insert a can-
nula, securing the latter by means of a silk ligature. Since the vein collapses after
the incision the opening is sometimes not easily found. The spring clip may then
be opened momentarily to allow a few drops of blood to escape. Always use a
cannula of about the same caliber as that of the blood-vessel into which it is inserted.

2. Arterial, Venous, and Asphyctic Blood. — Release the spring clips
upon the artery and vein sufficiently to allow the cannulas to become
filled with blood. Observe the difference in color. Explain. Close
the tracheal tube for a short time until the animal shows forced respira-
tory movements. Release the clip upon the artery, and allow the blood
in this cannula to be displaced by fresh blood. What is the color of
the latter? Compare it with that of the venous blood previously with-
drawn. Explain this difference. Clean both cannulas thoroughly by

THE BLOOD 69

means of a small plug of cotton fastened to the roughened end of a short
wire.

Annotation. — In operations upon animals the work should be divided in such a
way that every student has his own particular task to perform. Thus, one should
be assigned to give ether, another to perform the tracheotomy, and still another to
cannulaize the artery. During the next laboratory period the students should be
made to rotate, so that each has a different task to perform.

3. Coagulation of the Blood. — Expose the opposite external jugular
vein widely. Place two ligatures about 3 mm. apart around its central
portion. Again ligate twice its distal portion. Remove the interven-
ing segment of vein in its entirety by cutting between the two central
and two peripheral ligatures. Suspend this preparation for a period of
about forty minutes. Meanwhile perform the following experiments.

Annotation. — Unless the walls of the vein have been injured the blood in this
segment will remain fluid for an indefinite period of time, because no agent is present
therein to destroy the thrombocytes and to liberate thrombokinase.

Withdraw a small quantity of blood from the artery into a watch-
glass and observe the formation of the coagulum.

Allow a drop of blood to fall upon a glass shde, and observe under
the microscope the clumping of the corpuscles produced by the deposi-
tion of fibrin shreds.

Draw blood into a beaker and vigorously whip it for a few minutes
with a roughened piece of wood. Wash the fibrin attached to the stick,
and note its appearance, texture, and elastic properties. State why
blood from which the fibrin has been removed remains fluid. Thor-
oughly cleanse the cannula.

Collect a few cubic centimeters of blood in a test-tube and upon a
plate. Which specimen clots more rapidly?

Annotation. — Since the walls of the test-tube present a larger destructive sur-
face to the blood, this portion will clot more speedily.

Draw a small quantity of blood into a test-tube about 1 cm. in
diameter. Note the time of its withdrawal. Hold the test-tube steady
in your hand, sUghtly tilting it after one minute and again at intervals
of one-half minute until it can be inverted without the blood flowing
out. The time intervening between the withdrawal of the blood and
its coagulation is known as the coagulation time.

Withdraw a sample of blood into a test-tube and place the latter in
crushed ice. Since cold retards all chemical processes, it prolongs the
coagulation time.

Withdraw equal quantities of blood into two test-tubes, one of
which has been thoroughly anointed with vaselin. Give an explana-
tion for the fact that the blood in the latter clots less speedily.

Draw blood into one-quarter of its volume of a 1 per cent, solution
of potassium oxalate. Explain the fact that this blood remains fluid.

70 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

Later on add a few drops of a 2 per cent, solution of calcium chlorid.
Does this blood clot? Explain.

Draw blood into one-quarter of its volume of a saturated solution
of magnesium sulphate. Give a reason for its remaining fluid.

Thoroughly cleanse the glass cannula, and connect, it with a short
curved tube. Allow blood to enter this tube until the air has been
expelled from it. Then dip the tube into a receptacle filled with mer-
cury and allow a small quantity of blood to collect over mercury con-
tained in a narrow vessel. Does this blood which has not come in con-
tact with air clot?

Annotation. — Air is not an essential factor in the coagulation of the blood, and
hence a perfect clot is obtained under this condition.

Draw a small quantity of blood into a test-tube. Add a few drops
of distilled water. Note the changes in the color and general appear-
ance of this blood. Give their cause. Blood so hemolyzed is known as
laked blood.

To a thin layer of blood collected upon a slide add a drop of a solu-
tion of bile salts. Note under the microscope the rapid destruction of
the red corpuscles.

To another layer of blood add a drop of a hypertonic solution of
sodium chlorid. Study under the microscope the abnormal types of
red cells. Make sketches of them in different stages of crenation.

4. Relative Amounts of Plasma and Corpuscles. — Collect 30 c.c.
of blood in a test-tube. Immediately place it in the centrifuge opposite
a test-tube of the same size filled with water. Centrifugalize for a
period of five minutes. What is the proportion of plasma and cor-
puscles?

5. Enumeration of the Red Corpuscles. — Collect a drop of blood in
a watch-glass. Dip into it the end of a counting pipet (Thoma-Zeiss)
and aspirate gently upon the rubber tube until the pipet has been filled
with blood to line 1. Quickly cleanse its end with a piece of filter-
paper and dip it into Hayem's fluid. Aspirate until the bulb of the
pipet has been filled to line 101. Shake the tube well. Allow a drop
or two of this mixture to escape and place the next one upon the raised
base of the counting chamber. Do not allow it to overflow into the
space next to the base. Replace the cover, and determine under the
microscope the number of red cells in 20 squares. Take the average
and multiply this figure by 100 and 4000.

Annotation. — Since each square covers an area of 5ott sq. nim. and has a capacity
of 4 0*0 0 c.mm., 1 c.mm. must contain 4000 times the average number found in these
squares. Moreover, since the dilution is 1 : 100, the number of red corpuscles in 1
c.mm. of blood must correspond to the number of red cells in a square X 4000 X 100.

Hayem's fluid contains 2 grams of sodium chlorid, 10 grams of sodium sulphate,
1 gram of corrosive sublimate, and 400 grams of water.

The pipet is cleaned by drawing distilled water through it, then alcohol, and
lastly ether. A current of air is passed through it from a rubber bulb until dry.

THE BLOOD

71

The counting chamber is cleaned with distilled water and nothing rougher than a
camel's-hair brush. Do not use alcohol or ether.

6. Enumeration of the White Corpuscles. — Proceed as before, but
dilute the blood with a 1 per cent, solution of acetic acid. This agent
destroys the red corpuscles. The dilution usually made is 1 : 200.

=

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Fig. 44. — Hemocytometer. (Thoma-Zeiss.)

A, Pipet; B, glass bead; C, counting chamber seen from side; D, counting chamber seen

from above; E, field as seen under microscope.

7. Hemorrhage. — Remove the chp from the carotid artery and allow
the blood to escape into a tall beaker. Notice the differences in the
force of the flow and the changes in the character of the respiratory
movements, resulting in consequence of the progressive anemia and
insufficient aeration of the tissues (he;morrhagic dyspnea). Kill the
animal by giving an excessive amount of ether.

Place the beaker with the blood in a cool place and allow it to stand
for twenty-four hours. Study the appearance of the serum and coag-
ulum at the end of this period.

LESSON XI

THE BLOOD (Continued)

THE COUNTING OF HUMAN BLOOD-CORPUSCLES. SPECmC GRAVITY
AND APPEARANCE OF BLOOD

1. Microscopic Examination of Blood. — Pith a frog and open the
abdomen. Incise the ventricle and allow a few drops of blood to fall
into 20 c.c. of a solution of 0.7 per cent, sodium chlorid. Place a drop
of this mixture upon a glass slide and examine the corpuscles under the
microscope. Note their shape, size, and nucleus.

Place a droplet of blood from your finger upon a glass side and spread
it out by drawing the edge of a cover-glass through it. Note the shape
and size of the corpuscles. Move the cover-glass slightly so as to
obtain a lateral view of some of them. Note their shape.

Insert a thin layer of porous wood under the skin of the dorsal
lymph-sac of a normal frog. Allow it to remain there for twenty-four
hours. Remove it and carefully wash it in a few drops of normal saline.
Place a drop of the latter upon a slide and examine it for leukocytes.
Study the movements of one of these, making sketches in gross outline
at intervals of three minutes. If not actively moving, gently warm the
slide over an alcohol lamp. Add a few granules of powdered India-ink
and observe the manner in which the leukocytes envelop this foreign
substance.

2. Counting of Human Red Cells. — Wash the tip of your finger
with a cloth moistened in alcohol. Allow it to dry. Pierce the skin
of its dorsal surface with a lancet-shaped needle and squeeze the tissues
to obtain a droplet of blood as quickly as possible. Count the number
of the red corpuscles in the manner described in the preceding lesson.
Obtain a fresh droplet of blood and determine the number of the leu-
kocytes.

3. Simultaneous Count of Red and White Corpuscles. — Proceed as
described above when counting the red cells alone. Add a stain to the
diluting fluid that will color the white cells only, for example:

Methyl violet, 0.025 gram

Sodium chlorid, 1.0 '*

Distilled water, 100 c.c.

Count the red cells in a group of 36 spaces. Then count the white
cells in all of the 9 square millimeter spaces. Repeat with two or three
different samples. Obtain the average. Multiply by 4000 and again
by 100.

4. Estimation of the Percentage of Hemoglobin. — Procure a Fleischl
hemoglobinometer, glover's needle, and a small beaker. The metalUc

74 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

cup of the aforesaid instrument is divided into two compartments of
equal size, and has a glass bottom and detached glass top. Added to
it is a glass capillary tube held in a narrow metallic handle.

Cleanse the metallic cup thoroughly with water and dry it with a
cloth if necessary. Also cleanse the capillary tube with water and
hydrogen peroxid, and then again with water. Dry it by blowing a
current of air through it from a rubber pouch. Fill each side of the
metaUic cup with distilled water — about three-fourths full.

Collect a drop of blood upon the lobule of the ear of the subject.
Hold the end of the capillary tube horizontally against the drop. If
the tube is clean, it will fill rapidly by capillary attraction. Remove

Fig. 45. — Fleischl's Hemoglobinometer. (Hall.)

excess by touching its end carefully with filter-paper. Quickly put the
capillary tube in the water on one side of the metallic cup. Wave it
back and forth and finally allow a few drops of distilled water from a
dropper to flow through it. Fill each compartment with distilled water
to the brim, stirring the mixture of blood and water until completely
mixed. Close the cup with the cover-glass.

Adjust the hemoglobinometer in front of a gas-lamp in a dark
room, so that the light is reflected from the mirror equally into the two
compartments. Now, move the colored glass slide until the tint of the
diluted blood appears to be the same as that of the colored slide. Make
the reading. Repeat this procedure several times, resting your eyes
repeatedly. Obtain an average reading. Thus, if the colors are

THE BLOOD

75

matched, say, at division of 75, the blood contains 75 per cent, of the
normal quantity of hemoglobin.

Annotation. — Gower's hemoglobinometer, which may also be used, consists of
a measuring pipet, a graduated tube, and a sealed tube containing a standard colored
solution. This standard represents the color of a 1 per cent, solution of normal
blood. The graduated tube is marked in 100 or more parts, each part representing
20 c.c. The capacity of the capillary tube is 20 c.c. Thus, if the blood examined
is normal, it will be necessary to add water to mark 100 to make the colors corre-
spond. If the blood is not normal, the percentage can be read off from the graduated
tube above the diluted blood.

The pipet is filled in the usual way from a drop of blood collected upon the
lobule of the ear of the subject. Wipe away any excess of blood after it has been
filled. Then blow the blood drop by drop into the water. Shake this tube gently
until a thorough mixture has been obtained. Suck a few drops of distilled water
into the pipet and add this amount to the mixture. Place this tube beside the one
containing the standard solution. Add distilled water drop by drop until the color

n/7

100

%0

90

80
70
to

— 50
fO
30
• iO
■10

^

\7

iOc.rrm.

B

N/
D

(Gowers.)

Fig. 46. — Hemoglobinometer.
A, Tube filled with colored fluid; B, tube for mixing blood; C, receptacle for distilled
water with dropper; D, pipet.

of the blood mixture corresponds precisely with that of the standard. Make the
reading at this time, the percentage of hemoglobin being indicated upon the grad-
uated cylinder.

5. The Specific Gravity of the Blood.— Procure a specific gravity
bulb or hydrometer, a cylindric graduated glass tube about 15 cm. in
height, a pipet or pointed glass rod, a stirring rod, a glover's needle, and a
mixture of benzol and chloroform. Secure a drop of blood in the usual
way and allow it to fall into this mixture. If the drop of blood remains
in the center of the mixture, its specific gravity equals that of the mixture.
If it rises, it is lighter than the mixture, and if it gravitates downward,
heavier than the mixture. In the former case, add benzol, and in the

76

ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

latter, chloroform, until the drop retains a central position. The spe-
cific gravity of the mixture is then determined by means of the hy-
drometer.

Annotation. — Since the specific gravity of normal blood varies with the amount
of iron in the corpuscles, it must also vary with the percentage of hemoglobin.
Thus, the former corresponds to the following values of hemoglobin :

1.033 to 1.035 = 25 to 30 per cent. Hb.

1.035 to 1.038 = 30 to 35

1.038 to 1.040 = 35 to 40

1.040 to 1.045 = 40 to 45

1.045 to 1.048 = 45 to 55

1.048 to 1.050 = 55 to 65

1.050 to 1.053 = 65 to 70

1.053 to 1.055 = 70 to 75

1.055 to 1.057 = 75 to 80

1.057 to 1.060 = 85 to 90

LESSON XII

THE BLOOD (Concluded)

MEDICOLEGAL TESTS FOR BLOOD

1. Spectroscopic Examination of Blood. — Place a few drops of blood
in the glass cell provided for this purpose. Dilute it with water until
a 0.3 per cent, solution has been obtained. Examine it with a spectro-
scope. Identify the « and /5 bands. Burn a few crystals of sodium
in the flame to produce a distinct Fraunhofer D line.

Make a sketch showing the precise position and character of these
absorption bands.

Fig. 47. — Spectroscope.

P, Glass prism; A, collimator tube, showing the slit, S, through which the light is

admitted; B, telescope for observing the spectrum. (Howell.)

Reduce the oxyhemoglobin in the above solution by the addition of
a few drops of Stoke's fluid. Repeat the examination. Identify the
r band.

Add to diluted blood a solution of caustic soda or potash, and warm.
Reduce, and examine spectroscopically.

Annotation. — Greater concentrations than 0.65 per cent, produce a coalescence
of the a and /? bands, while very dilute solutions (0.01 to 0.03 per cent.) give rise to
a single band, near the D line. Employ solutions of 0.1 to 0.6 per cent, and use a
cell the inner width of which measures 1 cm.

Stoke's reducing fluid consists of a solution of ferrous sulphate, to which a little
tartaric acid has been added. When used, add ammonia 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 individually.

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 ligature to the neck of an etherized
turtle directly behind the occiput, and destroy the brain 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. — Arra.ngement for Registering the Contractions of the Frog's Heart.
(Univ. of Missouri Lab. Outlines.)

Identify the venae cavse, sinus venosus, the right and left auricle,
and the ventricle with its conus and main arterial trunks (aortse).
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

upward. 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.

Annotation. — Very good records ma}^ 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
dips. 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 venosus of this heart is formed by the
union of the large inferior vena cava and the two smaller superior vense cavse.
It is continuous with the right auricle and ventricle. The latter continues as the
bulbus aortae, 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 or the Contractions of the Frog's Heart.
The time is registered in seconds.

The registration may be effected in two ways, namely, by:
(a) 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 by the down-stroke of each wave.

(h) The Suspension Method. — A fine thread is attached to the end of the short
arm of an ordinary wTiting 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
tendency of which is to move upward, the string must be fastened to its long arm.
The contraction of the heart then pulls the lever downward, whereas the steel spring
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 drops of iced saline solution (5° to 10° C.) to drop upon the

THE HEART

81

heart. Note the reduction in the rate and slowing of each individual
beat. After the heart has again resumed its normal rate and ampli-
tude of contraction bathe it in the same manner with warmed saline
solution (20° to 25° C). Note the increase in its rate, due to a greater
rapidity of the individual contractions.

3. Refractory Period. Extrasystole. — Leave the heart in position,
but place its ventricular portion in the cup of a heart-holder. Adjust
the writing lever upon its surface, and connect the binding-posts with

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 systoUc and then during the diastoHc 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 consecutively. 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

6

82 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

ventricle. Not all of the auricular contractions will then be followed
by 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 HEART 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 become 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.; CaCh, 0.026 per cent. The
rhythm will presently be restored.

Annotation. — With some care a turtle's heart may be made to last throughout
these experiments. If it does not, use a frog's heart to complete this series. The
action of the 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
making four interdigitating cuts across it — two cuts starting 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 synchronously 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 tightly to the neck of
an etherized turtle and destroy 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. — Course of Vagus Nerve in Frog. {Stirling)
SM, Submentalis; LU, lung; F, vagus; GP, glossopharyngeal; HS, hypoglossal; L,
laryngeal; PH, SH, GH, OH, petro-, sterno-, genio-, and 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, stimulate the afore-
said nerve. If the heart is not inhibited, increase the strength of the
current, but not excessively, because 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?

a5

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.

Fig. 54. — Record of the Contraction's 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

^o

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.

THE HEART 87

Tighten the ligatures upon both vagi nerves. Apply a second liga-
ture to each at a distance of 2 mm. from the first. Cut between them.
Stimulate both central ends successively. Do you observe a change in
the character of the record now made? Stimulate both distal ends
successively. Do you observe a difference 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 stimulating the vagi nerves?

Annotation. — A very convenient way is to trephine the ventral shield of the
turtle in the region of the heart. This saves much labor and prevents loss of blood
and drying of the tissues. Moreover, if small pulley-wheels are at the disposal of
the students, the heart should be allowed to act in its normal horizontal position,
while the string is made to move across the pulley, placed obliquely below the
writing lever. Do not allow the heart to act under too great a tension and allow
it to rest from time to time by disconnecting the string. In case it should cease
contracting properly, apply a few drops of warmed saline solution to its surface.
Arhythmias are not uncommon and may be 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. Stimulate 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 break between the vagal terminals and the recipient cells
of the inhibitor plexus (Remaek's), situated in the region of the sino-auricular groove.
Consequently, the inhibitor impulses set up by stimulating the vagus can never reach
the postganglionic path and effector. The stimulation of the plexus itself remains
effective, because the postganglionic elements are thereby excited directly.

3. Action of Atropin. — Apply to the heart of the same turtle a few
drops of a 0.5 per cent, solution of atropin sulphate. After a few minutes
stimulate the plexus situated at the sino-auricular junction. Observe
that this stimulation now fails to inhibit the heart. Explain.

Annotation. — ^This experiment should, of course, be performed upon a fresh
turtle. It will then be found that the atropin destroys the inhibitor power of the
vagus as well as that of the plexus at the sino-auricular groove. This result is due to
its paralytic effect upon the distal terminals of the postganglionic fibers. Atropin is
primarily a nerve-fiber poison. Since in the above experiment the stimulation of
the vagus has already been rendered ineffective by the nicotin, this effect cannot be
noted. It is for this reason that a fresh turtle should be used for the atropin. With
a class of, say, 100 students this would entail a considerable expense which may be
avoided by supplying this information or by permitting one group of students to per-
form the experiment with nicotin, and another the experiment with atropin.

4. Action of Muscarin. — Apply to the ventricle of the same turtle
a few drops of normal saline to which a little muscarin has been added.

88 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

A 1.0 per cent, solution of pilocarpin acts in the same way as muscarin.
Note the gradual inhibition of the ventricle.

Annotation. — It will be remembered that this poison produces its characteristic
effect either by paralyzing the contractile elements of the muscle-fibers or by stim-
ulating the inhibitor nerve mechanism. The latter view seems the more plausible,
because if a few drops of a 0.5 per cent, solution of atropin are applied to a heart
which has been arrested with muscarin, this organ resumes its beat. Atropin acts
antagonistically to the muscarin by counteracting the effect of the latter.

5. Reflex Cardiac Inhibition. — Etherize a frog and lay it upon its
back. Make a rounded orifice in the ventral surface of the thorax in the
region of the heart so as to expose this organ fully to the view. With
the flat handle of a scalpel continue to tap lightly upon the ventral
aspect of the abdomen until the heart shows a material reduction in its
frequency. Explain this result, comparing it with the symptoms follow-
ing strokes upon the solar plexus in man.

Divide both vagi nerves and repeat this experiment. Note that the
aforesaid procedure now fails to inhibit the heart, because the paths by
means of which these impulses reach the heart have been cut.

Annotation. — In the frog the vagi nerves are not easily found. Insert a glass
rod in the esophagus to distend it. Remove the tissues over the petrohyoid muscle,
extending from the angle of the jaw to the thyroid process of the hyoid bone. Two
nerves will be seen pursuing a course across this muscle, namely, the hypoglossal
and the glossopharyngeal. The first is easily recognized by tracing its course to
the tongue. It lies closer to the midUne. Next to the lower border of the petrohyoid
muscle and close to a blood-vessel lies the vagus (Fig. 53).

6. Acceleration of the Heart. — Arrange the apparatus for registering
the contractions of the frog's heart upon the smoked paper of a moder-
ately rapid kymograph. Pith a frog and expose the heart by making a
median incision through the wall of the thorax. Expose the spinal
column at the base of the skull by pushing the esophagus and trachea
to one side. Identify the vagus ganglion. It lies under the upper part
of the levator scapulae muscle. After its formation the sympathetic
nerve turns outward along the base of the jaw to become united with
the vagal fibers. Black pigment marks the course of this nerve. Isolate
this portion and insulate it with a narrow strip of rubber membrane.
Allow the heart to register its beats while the drum revolves once around
its axis in about one minute. Add the record of a chronograph. Di-
rectly underneath register a second line of heart-beats, but stimulate
the sympathetic nerve during this entire period with a tetanic current
of very moderate intensity. Count the beats in each line, and com-
pare. The stimulation of this nerve in the frog does not produce a very
decisive acceleration; still, records of this length should show a difference
of from ten to fifteen beats.

LESSON XV

THE HEART (Continued)

STANNIUS^ EXPERIMENT. STAIRCASE PHENOMENON. SUMMATION
OF STIMULI. ACTION OF THE CONSTANT CURRENT, ETHER, AND
CHLOROFORM. DISSECTION OF THE MAMMALIAN HEART

1. Stannius* Experiment. — Pith a frog and expose the heart by a
median incision through the wall of the thorax. Use two thin silk
threads. Place one around the sino-auricular groove, and tighten it
moderately until the auricles and ventricle cease beating. Apply a
second ligature to the auriculo ventricular groove, and tighten it suf-
ficiently until all three parts of the heart beat again. Explain this
phenomenon.

2. Staircase Phenomenon. — Remove the ligature previously applied
to the auriculoventricular groove, so as to render the auricles and ven-
tricle again quiescent. Connect the latter with a light heart lever
(suspension method), and stimulate its substance with single induction
shocks at intervals of five seconds. Each time move the stationary-
drum a short distance. The heart usually reacts to stimuli of different
strengths by giving maximal contractions, but its amplitude of reaction
is determined chiefly by its condition. In the Stannius preparation
certain conditions have arisen which convert the first four or five con-
tractions into an ascending series.

3. Summation of Stimuli. — The Stannius preparation may also be
made to show the phenomenon of summation of stimuli. To accom-
plish this end separate the secondary coil from the primary until the
break shock just ceases to be effective. Stimulate the heart with this
subminimal stimulus in quick succession until a contraction is obtained.

4. Incomplete Tetanus. — The Stannius preparation may also be
made to yield an incomplete tetanus by passing a quickly interrupted
current through it.

5. Effects of the Constant Current. — Remove the ligature which
has previously been applied to the sino-auricular groove. The heart
should resume its normal beat. If not, use a fresh preparation. Insert
in the frog's mouth the wire connected with the zinc of a dry cell
(cathode). Place the flat end of the wire attached to the carbon
(anode) upon the surface of the ventricle. As the well-filled ventricle
contracts, that portion of it which rests against the anode will remain
relaxed and present a flushed appearance. In this way a local diastole
is produced in a general field of systole. Suddenly remove the wire,
breaking the circuit. The area just alluded to now remains contracted,
and shows, therefore, a pale appearance. A local systole arises within
a field of general diastole. This experiment may be employed to show
that the anode depresses on the make, but stimulates on the break.

90 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

The wires should now be reversed to show the cathodal excitation
on the making and the cathodal depression on the breaking of the con-
stant current.

6. Action of Chloroform and Ether. — Excise two frogs' hearts and
place each in a watch-glass. Cover them equally with a sufficient
quantity of saline solution (5 c.c). Add a drop of pure chloroform to
one and a drop of ether to the other. Note that the heart in the former
solution loses its tonus rapidly and soon ceases to beat, while the action
of the other does not seem to have been materially impaired. In order
to produce the same effect with the ether, as many as 10 drops might
have to be added to the original solution.

7. Dissection of the Mammalian Heart. — Procure the heart of an ox
or sheep. Ask to have the "tubes cut long." Identify its different parts
and test the relative thickness of the walls of its chambers. What is
the functional significance of this difference in the volume of the mus-
cle substance? Identify the aorta, pulmonary artery, venae cavse, and
pulmonary veins. Note the appearance and strength of the walls of
these blood-vessels. Trace the coronary arteries from the arch of the
aorta and identify the coronary sinus.

Explore the auricles and ventricles by inserting the index-finger
through the stumps of the different vessels. Palpate the interauricular
septum and locate the fossa ovalis. Slit open the two auricles and ex-
amine their walls and recesses. Note that the venous orifices are not
guarded by valves.

Beginning at the apex of the heart make a series of transverse sec-
tions until both ventricles have been opened. Note that the left cavity
is incised first and possesses a much thicker wall than the right. Obtain
an unobstructed view of the tricuspid and mitral valves by making a
longitudinal incision through the wall of each ventricle. Study the
appearance and distribution of the papillary muscles, columnse carnese,
moderator bands, and chordae tendineae. Approximate the valve flaps
and note the manner of insertion of the chordae tendineae. Trace the
course of the bundle of His.

Tie a short glass funnel in the stump of the ascending aorta. Hold
the heart vertically and pour water into the funnel. Observe that the
semilunar valve closes, thereby preventing the water from escaping" into
the left ventricle. By means of a long probe push one of the flaps aside.
Note the rush of water into the ventricle. This condition represents
aortic insufficiency (regurgitation). Repeat the experiment on the
right side. The sinuses of Valsalva are here more prominent, because
the vessel wall is much thinner.

LESSON XVI

THE HEART (Continued)

THE BEATING MAMMALIAN HEART. HEART-BLOCK. FIBRILLATION

1. The Beating Mammalian Heart in Situ. — Test the artificial
respiration apparatus to see whether everything is in proper working
condition. Have the ether bottle and connecting parts ready for use.
Etherize a cat and maintain deep anesthesia throughout these experi-
ments and until the animal has been killed.

Perform tracheotomy in accordance with the directions given on
page 67. Make a median incision through the skin covering the
sternum. Cut through the ensiform cartilage and median line of the
sternum, taking special care not to divide the mammary arteries.
Institute artificial respiration, 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 Tambour.
a, Axis of lever; h, metal tray covered with rubber membrane, and communicating by

tube / with the cannula.

and hgation 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 through an opening in the peri-
cardial sac, and secure it by means of a ligature. 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-
ferences which the heart displays during its cycle. Detach the rubber
tube from the recording 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.

Open the pericardial sac widely and reflect the pericardium upward.
Note the character of the fluid 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 fully 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 cavae and observe their pulsations
(venous pulse). Expose the aorta and puknonary 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 hemispheric glass capsule (C). The
latter is connected with a recording tam-
bour (T).

Fig. 58. — Clamp for Producing Heart-
block. {After E danger.)

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 saHne solution to fall upon the heart. Note
the increase in its frequency.

Procure a small cardiac plethy sinograph, 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 again register the volumetric changes of the heart. Occlude the
venae cavae for a few moments. Explain the result. Withdraw 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.

Again record the volume-curve of the ventricles. Temporarily
obstruct the arch of the aorta. Explain the result. Allow the heart to
rest.

2. Heart-block. Fibrillation. — Procure a clamp such as is represented
in Fig. 58. Remove the loose connective tissue from the wall of the
aorta along a line forming the right edge of the mass of fat which covers
the anterior aspect of this blood-vessel. Set the point of the hook in
this place, corresponding to the tip of the membranous septum of the
ventricles. Direct the needle obliquely downward and toward the
lumen of the aorta and force it into the left ventricle, approximately at
the junction of the right and posterior flaps of the mitral valve. Turn
the point of the hook backward, so that the short arm of the L-shaped
clamp comes to lie parallel to the ventricular septum. Now, move the
bar until it lies parallel to the first part of the arch of the aorta and
force the short arm of the hook into the septum at a point about 3 to
6 mm. below the auriculo ventricular junction and somewhat posterior
to the mesial flap of the mitral valve. Do not include the main trunk
of the coronary artery in the clamp. Tighten the clamp sufficiently
to cause a partial block. Not every auricular contraction will then be
followed by a ventricular contraction. This condition simulates the
condition of heart-block in man, usually brought about by inflammatory
lesions along the course of the bundle of His.

If done in an improper manner, the ventricle will immediately be
thrown into a condition of fibrillation. Its musculature then executes
irregular wave-like contractions. This condition may also be pro-
duced by injections of strophanthin (about 0.0003 gram). Shortly before
the onset of the fibrillation the heart frequently shows a typical block.

LESSON XVII

THE HEART (Concluded)

PERCUSSION AND AUSCULTATION OF THE HUMAN HEART UNDER
DIFFERENT CONDITIONS

1. The Area of Cardiac Dulness. — Percuss the region of the heart
of the subject, beginning in each case well without the boundaries of
this organ, and passing radially toward the sternal articulation of the
third rib. Accurately note the point where the deep resonance of the
lung passes over into the area of dulness of the heart. Outline the
boundaries of the latter with colored chalk. What is its size and posi-
tion? How is this area changed by the movements of the lungs on
inspiration and expiration? Explain. If abnormalities in' its size are
found,' give probable cause. Outline the area of cardiac flatness.

Annotation. — Percussion is usually practised by placing the middle and index-
fingers of your left hand flat against the wall of the chest. Tap upon them sharply
with the index and middle fingers of your right hand. In tapping, the right hand
should be held lose at the wrist, and the second and third phalanges should be flexed
upon the first at right angles.

2. The Rate of the Heart. — Determine by auscultation the number
of the heart-beats of the subject while he successively assumes the re-
cumbent, sitting, and standing position. Tabulate the results and
ascertain the differences. Have the subject make forty flexions and
extensions of the arms in one minute. Again determine the cardiac
rate. Repeat the count after the subject has made thirty deep knee
bendings in one minute, and again after a stationary run lasting one-
half minute. Arrange your results in the form of a table.

Determine the heart-rate for one minute. Ask the subject to swal-
low. What difference do you note?

Determine the heart-rate. Ask the subject to concentrate his atten-
tion upon his heart. Do you note any difference? Ascertain whether
the subject is able to increase his cardiac rate volitionally.

Annotation. — ^The method of auscultation is conveniently practised by applying
the ear to the chest of the subject, preferably in the region between the left nipple
and the sternum. The rounds are loudest in this area. Since we are dealing in the
above experiments with the frequency of the heart, you may allow a thin garment
to intervene between your ear and the skin of the subject.

3. The Cardiac Impulse or Apex-beat. — Carefully observe the chest
in the region of the apex of the heart, i. e., in the fifth intercostal space,
and at a distance of about 2 cm. to the right of the left nipple. Note
the periodic protrusion of the chest wall. Mark the location of this

95

96

ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

impulse with a blue pencil. Observe the changes in its conspicuousness
when the position of the subject is changed and during inspiration and
expiration. Explain the results. If the impulse is not in its normal
place, ascertain the direction and degree oif its displacement. Give its
probable cause. Palpate the radial artery and note the interval of time
between the radial pulse and the cardiac impulse. Palpate the carotid
artery low in the neck. Note that the difference in time between this

Fig, 59. — Cardiograph.
The tape is strapped around the chest. The central button is applied to the "apex-
beat" and its pressure on the chest wall regulated by means of the three screws at the
sides. The tube at the upper part of the instrument serves to connect the drum of the
cardiograph with a registering tambour. (Sanderson.)

pulse and the cardiac impulse is much less, a result easily explicable
upon the ground of distance.

Adjust a cardiograph to the area of the cardiac impulse. Connect
it with a recording tambour and allow the latter to register its excursions
upon the smoked paper of a kymograph revolving at a moderate speed.
This record should be made above a time-curve, registered by a Jaquet
chronograph.

C

Stc

Fig. 60. — Cardiogram.
AB, Systole; BC, plateau; CD, diastole; DA, pause; time in seconds.

Explain the character of the cardiogram so obtained. Excepting
the cardiac rate, is it possible to derive valuable data from this curve
which more particularly pertain to the quality of the contractions of
the heart? Give reasons for your conclusions.

Annotation. — ^The method of palpating the radial artery is practised as follows:
With your left hand support the right hand of the subject in a position of slight
extension. As a rule, the right artery gives better results. Place the second and

THE HEART 97

third fingers of your right hand upon the radial artery close to the wrist. It is then
a simple matter to determine the frequency of the pulse. Besides, the third finger
may be employed to compress the artery and the second to palpate. In this way the
experimenter may obtain an idea regarding the tension prevailing in the vascular
system of the subject.

4. The Heart Sounds. — Adjust your ear directly to the area of the
apex-beat of the subject. Study the quality and intensity of the car-
diac sounds. How many sounds do you hear? Note the pause fol-
lowing the second sound. Palpate the radial pulse and determine
whether these sounds are produced during ventricular systole or diastole.
Ascertain precisely when they occur and where they are most intense.
Request the subject to stop respiring after a deep inspiration and
observe the lesser audibility of these sounds. State the reason for this
change. Ask the subject to cease respiring after a forced expiration.
Why are these sounds now more clearly heard?

Repeat these tests with the help of a stethoscope. Place its chest-
piece over different regions of the heart. Compare the relative in-
tensity of the sounds when heard at the apex and when heard over the
junction of the second right costal cartilage. Do you obtain a dif-
ference? Give reasons for it.

Having thoroughly familiarized yourself with the character of the
normal heart sounds, study a simple murmur, such as may arise in con-
sequence of mitral stenosis or aortic regurgitation. Note its char-
acter, point of greatest intensity, and relation to the carfliac cycle.
Also familiarize yourself with the so-called extracardiac friction sounds,
hemic murmurs, and arterial and venous bruits.

7

LESSON XVIII
THE CIRCULATION

THE CAPILLARY CIRCULATION. CONVERSION OF AN INTERMITTENT
INTO A CONSTANT FLOW. SCHEMA OF THE CIRCULATION

1. The Capillary Circulation. — Procure a microscope with low- and
high-power objectives, a thin cork board about 20 cm. long and 10 cm.
wide, and a few pins. Bore a hole about 1 cm. in diameter close to
the margin of the cork board. Pith a frog, being careful not to lose
any blood. Immediately close the opening with the pointed end of a
short piece of wood. Place the frog, dorsum turned upward, upon the
board and bring one foot over the hole in the cork board. Stretch the
web uniting the second and third toes across the opening, and hold the
toes in place by means of pins or threads. Do not stretch the web
unduly, so as not to block the blood-vessels. Adjust the body of the
frog in an easy position.

Fasten the cork board to the stage of the microscope and illuminate
the web under an objective of low power. Moisten the frog repeatedly
with saline solution. Observe the movement of the blood and differ-
entiate between the red and white corpuscles. Note the differences
in the caliber of the blood-vessels and the speed of the blood flow.
Ascertain whether a certain vessel is an arteriole, a true capillary,
or a venule. Select a true capillary and observe how the red cells force
their way through it, elongating if necessary. Find a capillary which is
so small that only plasma passes through it. Do you observe an inter-
mittency in the flow anywhere in the field? What is its probable cause?
Have you seen a reversion of the blood flow? Give its cause.

Carefully adjust the high-power objective to the web, and repeat the
preceding observations.

2. Intermittent, Remittent, and Constant Flow. — Procure a piece of
band-tubing about 1.5 m. in length. Insert in one of its ends a glass
cannula, and in the other a valved rubber syringe. Dip the inlet tube
of the latter in a basin of water and ask the assistant to hold the end of
the band-tubing over the sink.

Compress the rubber bulb at intervals of five seconds. Note that
the tubing fills gradually, but does not discharge until it has attained
a definite degree of distention. It then discharges a certain quantity
of water with every compression of the bulb (intermittent flow). Com-
press at a faster rate until the flow does not cease entirely during the
interims (remittent flow). Compress at still briefer intervals until
the tubing attains a high degree of distention and continues to empty
its contents evenly during the time when the rubber bulb aspirates
(constant flow). Obviously, the successive muscular efforts required to

99

100

ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

compress the rubber bulb are stored in the wall of the tubing in the
form of elastic tension. As soon as the internal pressure is lessened
during the interims this elastic power acts upon the water within the
tubing and continues to force it onward through the outlet. To ac-
complish this end the tubing must be highly distended, i. e., it must be

Fig. 61. — Simple Schema to Illustrate the Factors Producing a Constant Head
OF Pressure in the Arterial System.
a, A syringe bulb with valves, representing the heart; b, glass tube with fine point
representing a path with resistance alone, but no extensibility (the outflow is in spurts
synchronous with the strokes of the pump); c, outflow with resistance and also extensible
and elastic walls represented by the large rubber bag, e, the outflow is a steady stream due
to the elastic recoil of the distended bag, e. (Howell.);

retained in a condition of hyperfilling. To what constituents of the
vascular system may the different parts of this apparatus be compared?
Remove the narrow glass cannula (capillaries) from the end of the
band-tubing (arteries). This decreases the peripheral resistance. What
effects do you observe? Insert a narrow glass cannula and note the
effects of this increase in the peripheral resistance upon the distention

Fig. 62. — Artificial Schema of the Circulation. (Porter.)

of the band-tubing and the escape of water. In the latter case you may
materially decrease the number of the compressions without destrojdng
the constancy of the flow.

3. Schema of the Circulation. — The basin of water represents the
left auricle, the rubber bulb the left ventricle, and the large rubber tube
the aorta. The large glass tube next to the basin contains the mitral

THE CIRCULATION

101

valve, and the one distally to the bulb the aortic semilunar valve. The
side branch from the ventricle may be connected by means of a thistle
tube with a membrane manometer, and may thus be used to register
the changes in pressure in the ventricle. In a similar manner the
changes in pressure in the aorta may be recorded (arterial pulse).
Beyond the aorta lies the remaining portion of the arterial system, to
which there is attached a mercury manometer for measuring the arterial
pressure. Into the dish opens the venous system. It is equipped with
a mercury manometer for measuring the venous pressure. Between
the arteries and veins are the capillaries, represented in the schema by
a short piece of porous bamboo, and a side branch bearing a clamp.

Fig. 63. — More Recent Schema of the Circulation.
The action of the heart is here iraitated by a tambour, rhythmically compressed by
hand. The veins empty their contents into a receptacle (right auricle) fastened to the
side of the upright stand. (Harvard Apparatus Cp.)

A. Normal Circulation. — Dip the inlet and outlet tubes of this
system into the water in the basin and pump gently with the rubber
bulb until the different tubes have been filled with water. Clamp the
side branch between the arteries and veins. Pump gently at the rate
of about sixty times in a minute, and observe the following:

(a) The action of the valves,

(6) The arterial pressure and its changes,

(c) The venous pressure,

(d) The pulse in the aorta, and

(e) The character of the flow from the veins.

Open the clamp slightly, so as to simulate dilatation of the arterioles,
and pump as before. What is the effect of this procedure on the arterial
and venous pressures and on the character of the venous flow?

102 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

Open the clamp widely, and pump at the rate of about twelve times
in a minute. Effect?

Determine the respective conditions under which the venous flow
becomes intermittent, remittent, and constant.

Try to discover the causes, in the normal circulation of the blood,
of the great difference between the arterial and venous pressures, and
the absence of a pulse in the veins.

B. Intraventricular Pressure. — Place a thistle tube against the mem-
brane closing the lateral tube of the rubber bulb (ventricle) and con-
nect it with a recording drum. Register the changes in pressure occur-
ring within the ventricle upon the smoked paper of a slowly revolving
kymograph.

C. Pulse. — Place the thistle tube upon the "aorta" and register its
pulsations.

D. Mitral Insufficiency. — Remove the rubber sheath from the glass
tube representing the mitral valve. This produces a condition analogous
to mitral insufficiency. Pump at a normal rate. Observe the effect
of this lesion upon the intraventricular pressure, the arterial pressure,
the aortic pulse, and the venous discharge. Replace the sheath.

E. Mitral Stenosis. — Tie a thread around the sheath of the mitral
valve, thereby restricting the size of this opening. This produces a
condition analogous to mitral stenosis. What effects do you notice?

F. Aortic Insufficiency. — Remove the sheath from the semilunar
valve, producing thereby a condition analogous to aortic insufficiency.
What changes do you observe? Replace the sheath.

G. Aortic Stenosis. — Tie a thread around the sheauh of the semilunar
valve so that the opening becomes smaller. This condition simulates
aortic stenosis. Observe the results.

LESSON XIX

THE CIRCULATION (Continued)

THE CAUSE AND VELOCITY OF THE PULSE. DIRECT METHOD OF
ASCERTAINING THE BLOOD-PRESSURE

1. Schema Illustrating the Differences in the Velocity of the Blood

Flow. — Procure a glass bulb, such as is represented in Fig. 64. Con-
nect its inlet tube by means of a relatively narrow glass tube with the
water hydrant. On opening the stop-cock the
water will advance to a higher level, its flow
being most rapid in the narrow inlet tube, very
slow in the enlarged central portion, and inter-
mediate in the outlet tube. If all the arteries,
capillaries, and veins could be united into single
tubes, the calibers of these three divisions would
differ in the same way, i. e., the bed formed by
the arteries would be the smallest of all, and
that of the capillaries the largest. Since the
speed of flow is inversely proportional to the
lumen of the vessel, the blood must attain its
greatest velocity in the arteries, and its slightest
velocity in the capillaries.

2. Schema Illustrating the Cause and Velocity
of the Pulse. — Procure four glass tubes, each
about 1 m. in length and 1 cm. in diameter.
Arrange them vertically about 20 cm. apart,
and connect them in series by means of band-
tubing, each piece being about 50 cm. in length.
Attach a valved rubber bulb to the end of this
system, and allow its inlet tube to dip inttD
a basin filled with water. Compress the bulb
rhythmically until this entire system has been well filled. The water
then rises in the laterals to a certain level, indicating the pressure ex-
isting at these different points. Secondly, each compression of the bulb
then produces an oscillation of the water in the successive laterals, the
water in the lateral nearest the rubber bulb being moved first (Fig. 65).

3. The Direct Method of Determining the Arterial Blood-pressure.
— Weigh the animal and compute the quantity of blood present in its
body. Give it ether and maintain the anesthesia until it has been killed.
Perform tracheotomy. Expose the carotid artery on the left side and
the external jugular vein on the right side. (See Lesson X.) Place a
silk thread loosely around each blood-vessel. Raise both sufficiently to
occlude them. Notice that the artery is more highly distended on the

103

Fig. 64. — Schema
Illustrating the Dif-
ference IN THE Veloc-
ity OF THE Blood Flow.
A, Arteries; C, cap-
illaries: V, veins.

104

ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

central side of the ligature, and that its distal end does not collapse
altogether, owing to the fact that the carotid arteries anastomose rather
freely with one another. Observe that the distal end of the vein is
highly distended, whereas its central end is collapsed. This is one of
the tests which Harvey employed to prove the circulation of the blood.
Observe the changes in the caliber of the vein during inspiration
and expiration. During the former period its size is decreased, and
during the latter, increased. These changes are referable to the aspira-
tory action of the thorax, because the inspiratory movement augments
the elastic pull of the lung tissue upon the yielding walls of the central
venous trunks. During expiration, on the other hand, the lung tissue
recoils more completely, and does not exert so powerful a traction upon
the venous trunks and their contents. Accordingly, the inspiratory
movement decreases the pressure in the central veins and draws a
larger quantity of blood into them and the right side of the heart.

Fig. 65. — Schema Illustrating the Cause and Velocity of the Arterial Pulse.
W, Basin with water; P, valved rubber bulb; B, band-tubing between the laterals C.

Observe the changes in the caliber of the artery during inspiration
and expiration. It increases during the former period, and decreases
during the latter. Since the heart receives a larger quantity of blood
during inspiration, it is capable of transferring a larger amount of it
into the arteries. The pulmonary blood-vessels are at this time more
widely dilated, and permit a free through flow.

Free the common carotid artery from its fascia and insert in it a
glass cannula. Fill the latter with a solution of sodium carbonate.
Fill the rubber tubing and central limb of the mercury manometer with
the same solution. Determine the zero-line or hne of atmospheric
pressure (760 mm. Hg.). Connect the arterial cannula with the man-
ometer.

Annotation. — ^The zero-line is ascertained as follows: Bring the level of the mer-
cury in the central limb of the manometer on the same level with the carotid artery.
Connect the rubber tubing with a glass bulb filled half-way with a solution of sodium
carbonate. Adjust the level of this solution to the level of the mercury in the
central limb of the manometer. At this time the recording needle of the float,

THE CIRCULATION

105

resting upon the mercury in the distal limb of the manometer, is set at zero. In
order to be able to retain this line during the succeeding experiments, adjust the sta-

FiG. 66. — Schema to Show the Connection Made Between the Artery and Man-
ometer.
M, Manometer; H, mercurial column; F, float; D, recording needle; K, kymograph;
B, tube leading to reservoir filled with solution of sodium carbonate; R, rubber tubing
filled with sodium carbonate solution; C, glass cannula in artery; A, cUp upon artery;
V, maximal-minimal valve (Frank) to be inserted in this Circuit; 1, maximal, 2, minimal
side; Vu maximal valve of Hurthle. A minimal valve is obtained by inverting the central
tube.

Fig. 67. — Diagram to Show the Adjustments Necessary for Determining the

Zero-line of the Manometer (M).

Its central limb (A) is brought upon the same horizontal line as the level of the water in

the glass bulb (B) when held at the level of the blood-vessel (C).

tionary recording lever of the manometer to the level of the writing needle of the
float. The latter may then rise above this zero-line to indicate the blood-pressure.

106

ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

The recording needle of the manometer having been placed against
the smoked paper of the kymograph, allow a small quantity of sodium

Fig. 68. — Record of Blood-pkessure Showing the Cardiac and Respiratory Varia-
tions.
The time, registered in seconds, serves as the abscissa.

carbonate to enter the connecting tubes from a iQceptacle suspended
above the manometer. Remove the chp from the artery, and adjust

Fig. 69. — Traube-Hering Curves.
The time is given in seconds. The smallest pulsations represent the cardiac varia-
tions, those of intermediate size the respiratory variations, and the large waves the
Traube-Hering variations.

the speed of the drum so as to render the individual cardiac variations
clearly perceptible. Observe the character of the respiratory varia-

THE CIRCULATION 107

tions in pressure and note that each is made up of a number of cardiac
variations. Does the tracing show Traube-Hering curves, which are
rhythmic waves including several respiratory variations? Ascertain the
height of the pressure.

Annotation. — It is best to establish a certain degree of pressure in the manometer
before the blood is actually allowed to act against the mercury. In a cat or dog we
may expect to obtain a pressure equalling 120 to 130 mm. Hg. Thus, if we estab-
lish, a pressure of 100 mm. Hg. beforehand, only a small quantity of blood need pass
into the glass cannula to produce the additional pressure. On the other hand, if
the recording needle is allowed to remain at zero to begin with, the aforesaid
degree of pressure can only be produced by the passage of a considerable portion of
the blood into the connecting tubes. In small animals this would give rise to a
material decrease in pressure, and would greatly favor the occurrence of coagulation
in the connecting tube.

To obtain the blood-pressure, measure the distance between the zero-line and
the midline of the oscillations recorded by the manometer (H). Employ the formula:

P = 2H — --

13.5

Obviously, the recording needle registers merely the upward movement of the
mercury in the distal limb of the manometer. It must be remembered, however,
that the mercury in the central limb moves at this time an equal distance in a down-
ward direction, and hence the distance between the zero-line and the oscillations in
pressure, as registered by the needle, must be multiplied by 2. In addition, the cor-
rection .„"_ must be made, because the blood acts against mercury, which is 13.5

lo.O

times as heavy as water.

In order to obtain a more accurate mean pressure a large number of measure-
ments must be made, first, of the systolic pressure, and secondly, of the diastolic
pressure. The arithmetic mean between the averages of these pressures may be
taken to be the mean blood-pressure. More accurate determinations require piano-
metric measurements.

4. Influence of Posture. — Remove the clip from the artery, and
again record the blood-pressure. Raise the posterior extremities of the
animal vertically upward. Keep them in this position for ten seconds
and again lower them slowly. By this means a large quantity of blood
is forced into the head-circuit of the animal, occasioning a rise in the
carotid pressure. Such increases in blood-pressure are usually asso-
ciated with a reflex slowing of the heart.

5. Compression of the Abdominal Aorta. — The preceding result may
also be obtained by temporarily occluding important subdivisions of
the vascular system. Thus, if the thumb is pressed flat against the
spinal column somewhat below the left costal arch of the animal, the
resultant compresssion of the abdominal aorta must lead to an engorge-
ment of the head-circuit and a corresponding rise in the carotid pressure.
Observe that the sudden release of the compression usually causes the
pressure to fall below normal, and that several seconds then commonly
elapse before it again assumes its normal height. It is only natural
to assume that the sudden inrush of the blood into the previously empty

108 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

blood-vessels of the posterior part of the body must cause a temporary
reduction in the quantity of the blood allotted to the head-circuit.

6. Influence of Hemorrhage. — Insert a cannula in the femoral artery.
While a tracing of the carotid pressure is being recorded remove the clip
from the femoral artery and allow 20 c.c. of blood to escape into a beaker.
Observe the systolic increase in the force of the ejection. Again apply
the clamp and allow the pressure to adjust itself. What factors are
involved in this compensation? Again withdraw 20 c.c. of blood, and
continue this procedure until the pressure has fallen to zero. Care-
fully observe the symptoms of excessive hemorrhage, as displayed by the
changes in the character of the respiratory movements and the rate and
force of the heart. How much blood has been withdrawn, and what
proportion of the total quantity present in this animal? Kill the ani-
mal by giving an excessive amount of ether.

LESSON XX
THE CIRCULATION (Continued)

VENOUS VALVES. INFLUENCE OF DYSPNEA UPON THE BLOOD-PRESS-
URE. ACTION OF AMYL NITRITE AND ADRENALIN. HEMORRHAGE

1. Position and Function of the Venous Valves. — Ask the subject
to hold his arm in a dependent position. Encircle the forearm with a
piece of rubber tubing, 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 distally 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

jM.

*gi%(p»

-iWi»»

. J'nfiffiwfifnViniff^

Fig. 70. — Record of the Carotid Blood-pressure During Dyspnea (Dog).
At L the tracheal tube was held shut until the blood-pressure began 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 preserved in alcohol.

2. Blood-pressure. Influence of Dyspnea. — Anesthetize a mammal
and maintain the anesthesia until it has been 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 respiratory movements gradually assume a labored
character and that the respiratory variations in blood-pressure are
thereby 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 established. Explain in detail
the action of this agent.

What are the hemodynamic conditions estabUshed 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 saJine 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 CIRCULATION 111

stand obliquely above the vein. Record the blood-pressure. Release
the clip slightly and allow 1 to 2 c.c. of the solution of adrenalin 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-pressure. Account for this interval.
Note the character of the reaction and explain its cause.

What is the effect of adrenalin when appHed to bleeding surfaces?
State why adrenaUn is added to solutions used for purposes of infusion
after hemorrhage.

Fig. 72. — Effect of Adrenalin on Blood-pressure (Dog).

Annotation. — Since adrenalin deteriorates on standing, and especially when
exposed to light, its strength can only be determined in a physiologic way. Conse-
quently, adjust the dose to the reaction obtained, i. e., give it in smaller quantities
if the rise is excessive and if the heart-beats assume a pronouncedly diastolic char-
acter.

5. Hemorrhage and Saline Injection. — Heat a considerable quantity
of physiologic salt solution to 38° C. Draw 100 c.c. of this solution into
a pipet and connect the latter with the cannula in the jugular vein.
Record the blood-pressure. Bleed the animal through the femoral ar-
tery until the carotid pressure has fallen to about 50 mm. Hg. Allow
50 c.c. of saUne solution to enter the venous circulation. What effect
is produced thereby? Repeat the injection until the pressure has be-
come normal. How large an amount of the solution has been injected?
Kill the animal by giving an excessive amount of ether.

A

LESSON XXI
THE CIRCULATION (Continued)

THE EFFECT OF DIVISION AND STIMULATION OF THE VAGUS NERVE
UPON THE BLOOD-PRESSURE AND ACTION OF THE HEART

1. Stimulation of the Intact Vagi Nerves. — Etherize a mammal and
continue the anesthesia until the animal has been killed at the end of
the following experiments: Perform tracheotomy. Listen to the heart
sounds and locate the cardiac impulse. With the tips of your index-
fingers press gently upon the skin of the neck overlying the vagi nerves.
Do you notice a reduction in the rate of the heart? Expose the com-
mon carotid artery on the left side and insert in it a straight cannula
to be connected later on with the mercury manometer. Also expose the

Fig. 73. — Record of Carotid Blood-pressure.

S, Stimulation of left vagus nerve. The fall in pressure is followed by compensatory

changes before the normal pressure is again established.

common carotid artery on the right side, and separate both vagi nerves
from the sheaths of these blood-vessels. Place each in a loose silk
ligature. Arrange the stimulating apparatus to yield a quickly inter-
rupted current of medium strength.

Apply the electrodes to the left intact vagus and stimulate briefly,
while the normal blood-pressure is being recorded. In case the efi'ect
is too indefinite, increase the strength of the current slightly. Test
the opposite nerve in the same manner and with the same strength of
current. Do you notice a difference in the inhibitor power of these
nerves? In each case allow the pressure to return to normal before you

8 113

114 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

stimulate again. Note the compensatory variations occurring at this
time.

2. Division of One Vagus Nerve. — Apply another loose ligature to
each vagus nerve. Record the normal blood-pressure. Ligate one
vagus twice and cut between the Hgatures, so that its central and distal
stumps may be stimulated separately. Indicate the moment of the
division upon the tracing. What changes do you observe in the blood-
pressure? Obtain the cardiac frequency from the tracing before and
after the section. To what factor do you attribute the rise in pressure?

Stimulate the distal end of this nerve. After the pressure has re-
turned to normal stimulate the central end of this nerve. What deduc-
tions may be drawn regarding the inhibitor qualities of the vagi?

Annotation. — It has been stated above that the inhibitor power of the vagi
nerves differs in different animals. Thus, cardio-inhibition is easily obtained in
the dog, but only with difficulty in cats. Secondly, in certain animals the stimulation
of the central end of one vagus — the other being intact — produces a reflex slowing
of the heart.

3. Division of Both Vagi Nerves. — Record the blood-pressure and
divide the opposite vagus in the same manner. Determine the cardiac
rate before and after the section. Are the effects previously noted now
more pronounced? Stimulate the distal and central ends of this nerve.
Compare the inhibitory power of the left nerve with that of the right.

Annotation. — ^The inhibitor power of these nerves varies considerably. Some-
times the left and sometimes the right nerve is the stronger of the two, but most
generally the right. With both nerves divided, the stimulation of either central end
must necessarily fail to produce a reflex slowing of the heart.

4. Inhibition of the Exposed Heart. — Test the artificial respiration
apparatus and adjust the check- valve for an air current of medium
volume. Connect the tracheal cannula of the animal with the ether-
bottle. Incise the skin over the sternum. By means of a pair of
strong scissors cut through this bone directly in the median hne, avoid-
ing the mammary arteries. Institute artificial respiration. Vary the
position of the stop-cock upon the inlet tube to give to the lungs a normal
degree of inflation. Stop the bleeding by applying a compress or by
torsion and hgation of the vessels. Pull the edges of the sternum apart
by means of a strong string drawn around the board. Open the peri-
cardial sac and inspect the heart, repeating the observations made
in the course of Lesson XVI. Stimulate the distal end of either vagus
nerve. Note that the heart stops in diastole, greatly distended by
blood. Observe the swollen condition of the central veins, indicating a
rise in venous pressure.

Endeavor to regain the heart in the inhibited condition by prolong-
ing the duration of the stimulation. What happens? When the heart
resumes its beat it is apparent that it contracts first in the region of the
pace-maker, giving a well-marked contraction wave.

THE CIRCULATION

115

5. Intracardiac Pressure. — Expose the right external jugular vein.
Place a clip upon it centrally and ligate it about 2 cm. farther distally.
Open this vein between the clip and the ligature and insert the end of a
long, hollow probe filled with physiologic salt solution. Place a liga-
ture rather loosely around that portion of the vein which contains the
end of the catheter. Connect the latter with a membrane manometer.
Remove the clip from the vein and push the catheter slowly downward
until its free end comes to lie in the right auricular cavity. Obtain a
tracing of the right intra-auricular pressure.

Push the catheter through the auriculoventricular orifice into the
right ventricle, taking care not to injure the tricuspid valve. Obtain
a tracing of the right intraventricular pressure. Withdraw the catheter
and replace the clip upon the vein.

^:^<^}^^a^^

tn.

Fig. 74. — Diagram of Membrane Manometer,

M, Rubber membrane connected with writing lever (L). The drum (T) is connected with

the cannula in the blood-vessel: R, rod to fasten manometer to stand.

Study the character of each tracing and compare them with one
another. Calculate the pressures so obtained by comparing the oscilla-
tions of the membrane with those of a mercury manometer.

6. Entrance of Air Into the Circulation. — Insert a glass cannula in
the right external jugular vein. Record the blood-pressure, and apply
a stethoscope to the chest wall. Force a small amount of air into the
aforesaid vein. After a short latent period the blood-pressure will begin
to fall, this fall being accompanied by a peculiar noise produced by the
frothing of the blood within the heart, as the valve flaps beat against
the bubbles of air.

Kill the animal by an overdose of ether. Open the heart and ex-
amine the character of the blood. Dissect the heart, repeating the
observations made in the course of Lesson XV.

LESSON XXII

THE CIRCULATION (Contmucd)

THE VASOMOTOR ACTION OF THE CERVICAL SYMPATHETIC,
DEPRESSOR, AND SCIATIC NERVES

1. The Cervical Sympathetic Nerve. — Etherize a rabbit and main-
tain the anesthesia throughout the following experiments: Perform
tracheotomy. Make an incision along the inner border of the sterno-
cleidomastoid muscle, and retract this muscle laterally outward. Do
not disturb the relationship of these parts by dissection. Identify the
carotid artery and the large vagus nerve right neighboring. In addi-
tion, identify two delicate nerves, one white and one gray in color.
The former are the depressor fibers of the vagus which pursue a separate
course in the rabbit, and the latter, the sympathetic fibers uniting the
inferior and superior cervical ganglia of this sys-
tem. Place each in a loose silk ligature. Shift
the head of the animal so that the ear on the
side operated on may be placed in a position for
inspection. Hold an incandescent lamp behind
it. Identify the central artery of the ear and
the lateral venous collecting channels. Arrange
the electric apparatus for stimulation with a
quickly interrupted current of very moderate
intensity. Gently raise the cervical sympath-
etic nerve from the wound and place it in
small shielded electrodes. Stimulate for a
period of about fifteen to twenty seconds. Note
that after an appreciable latent period the
central artery becomes less conspicuous and
eventually disappears altogether. Discontinue the stimulation and
allow circulatory conditions to become normal again. What conclusions
may be drawn from this experiment regarding the vasomotor action of
this nerve?

Raise the cervical sympathetic nerve and cut it between two liga-
tures. Inspect the blood-vessels of this ear. Note that its vascularity
is now much greater than before and exceeds that of the opposite organ.
It also possesses a higher temperature. Obviously, the division of this
nerve has given rise to a relaxation of the blood-vessels of the correspond-
ing ear. Stimulate the distal end of the divided nerve and repeat the
observations made previously (Fig. 76).

It might be well to allude at this time to the influence of this nerve
upon the size of the pupil, although the student cannot be expected as
yet to be famihar with this particular reaction. Since the cervical

117

Fig. 75. — Shielded

Electrodes.

{Harvard Apparatus Co.)

118

ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

sympathetic nerve contains certain fibers which innervate the radial
muscle cells of the iris, its excitation must give rise to an increase in the
size of the pupil. Consequently, if any doubt exists as to the character
of the nerve isolated, this reaction may be employed to make sure that
it is the sympathetic.

Fig. 76. — The Vasomotor Reaction in the Ear of the Rabbit on Division and

Stimulation of the Cervical Sympathetic Nerve.

A, Normal, B, After division of the cervical sympathetic nerve. C, On stimulation of the

distal end of the divided cervical sympathetic nerve.

2. The Depressor Nerve. — Insert a straight cannula in the left
common carotid artery and connect it with the mercury manometer.
Place the depressor nerve in shielded electrodes, and arrange the electric
apparatus for stimulation with a quickly interrupted current of mod-

FiG. 77.

-Record of the Carotid Blood-pressure in Rabbit During Stimulation
OF the Depressor Nerve.

erate strength. Record the blood-pressure and stimulate the aforesaid
nerve for about twenty seconds. Note the fall in blood-pressure and
also the decrease in the frequency of the heart. Allow the pressure to
return to normal.

THE CIRCULATION

119

Apply two ligatures to this nerve, a few millimeters apart, and cut
between them. Record the blood-pressure and stimulate its central
and distal (heart) ends successively at intervals. Since the excitation
of the distal end remains ineffective, what conclusions may be drawn
regarding the direction of conduction in this nerve? What two factors
should be held responsible for the fall in blood-pressure?

Divide both vagi nerves and repeat the stimulation of the central
end of the depressor as soon as the changes ordinarily following the
section of the aforesaid nerves, have become thoroughly established.
Observe that henceforth the fall in blood-pressure is no longer asso-
ciated with a reduction in the frequency of the heart. Give a detailed
explanation of the function of the depressor nerve, and mention condi-
tions during which this mechanism is called into play.

-=^si-

Fig. 78. — Diagram to Show the Course of the Depressor Nerve in the Rabbit.
L, Larynx; T, thyroid gland; j, int. jugular vein; C, carotid artery; S, sympathetic
nerve extending between the superior and inferior cervical ganglia; V, vagus nerve;
SL, sup. laryngeal nerve; D, depressor nerve, entering the vagus by two branches.
The vagus is pulled over, permitting the sympathetic to appear next to the carotid artery.

3. The Sciatic Nerve. — Test the artificial respiration apparatus and
connect the ether-bottle with the tracheal cannula. Prepare a solution
of curare. Inject 1 c.c. of this solution intravenously by means of a
syringe. Allow this agent to produce its characteristic effect, and
institute artificial respiration as soon as the diaphragm shows the first
indications of ceasing its -action (fifteen minutes). Expose the sciatic
nerve in the thigh; place a Hgature upon it, and cut it distally to the
ligature. Record the carotid pressure and stimulate the central end
of this nerve with a quickly interrupted current of moderate strength.
As a rule, currents of medium strength and frequency give rise to a
reflex vasoconstriction, and hence to an increase in the carotid blood-
pressure. Since the motor plates of the skeletal musculature have been
paralyzed by the curare, this result cannot be referred to the mechanical
influence of contracting muscle tissue.

120 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

Weaken the strength of the current considerably by moving the
secondary coil farther away from the primary. Stimulate the nerve in
the same manner with single induction shocks repeated at intervals of
about half a second. This procedure usually gives rise to a reflex vaso-
dilatation, and hence to a fall in the carotid blood-pressure. Conse-
quently, the sciatic nerve contains vasoconstrictor as well as vaso-
dilator fibers. Kill the animal by an overdose of ether.

Annotation. — In isolating the sciatic nerve make use of the following landmarks:
Seek a point midway between the ischium and great trochanter of the femur, and
draw an imaginary line from here to the anterior aspect of the knee-joint. Direct
the incision along this line about the middle of the thigh and separate the adjoining
muscles until the fatty tissue investing the sciatic nerve has been exposed.

LESSON XXIII
THE CIRCULATION (Continued)

THE VASOMOTOR ACTION OF THE GREATER SPLANCHNIC NERVE.
THE VASCULARITY OF THE KIDNEY. ONCOMETRY

1. The Greater Splanchnic Nerve. — Anesthetize a cat and maintain
deep anesthesia throughout the following experiments : Perform trache-
otomy. Insert a straight cannula in the left common carotid artery
and arrange the apparatus for recording the blood-pressure. Make a
median incision through the skin of the abdomen and incise the linea
alba. Introduce the middle and index-fingers of your left hand through
this opening and by using them as a guide enlarge the incision upward
as far as the ensiform cartilage, and downward as far as the region of

Fig. 79. — Region of Left Kidney.
JC, Inferior vena cava; RV, renal vein; K, kidney; SC, left adrenal body with cor-
responding vein; <S, greater splanchnic nerve; A, abdominal sympathetic nerve; Af, minor
splanchnic nerves, from lumbar ganglia to suprarenal plexus below adrenal body; D,
diaphragm; TS, thoracic sympathetic nerve.

the bladder. Apply a cloth moistened with warmed saUne solution to
the abdomen.

Arrange the electric apparatus for stimulation with a quickly inter-
rupted current of medium strength. Procure a pair of small shielded
electrodes and connect them with the secondary coil of the inductorium.
Ask the assistant to expose the region above the left kidney, holding
this organ and the liver away from the field of operation. Identify the
left suprarenal body at the junction of the left suprarenal vein with the
inferior vena cava. It appears as a rounded, pea-shaped mass, possess-
ing a pink color. With two forceps split the peritoneum and fascia

121

122

ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

along its right (as you look at it) upper margin. Yery carefully search
for a small nerve in the fatty tissue of this region pursuing an oblique
course upward through the crus of the diaphragm. This is the left
greater splanchnic nerve, connecting the thoracic sympathetic system
with the solar plexus. Place a loose silk hgature around it and secure
it in shielded electrodes. Insulate by means of a narrow piece of rubber
membrane and dry cotton. Allow the parts to close in around the
electrodes and apply a warm cloth to the abdomen.

Allow the carotid blood-pressure to be recorded. Stimulate the
aforesaid nerve for about ten seconds until you have obtained an appre-

/^>0j^

^%«Sf«S0>jii^^

Fig. 80. — Splanchnic Rise in Blood-pressure.

ciable rise in pressure,
the clip to the artery.

Repeat this procedure after an interval. Apply
Study the character of the tracing so obtained.

Annotation. — The rise in blood-pressure usually consists of two phases. The
first is brought about by the vasoconstriction, resulting in the so-called splanchnic
organs in consequence of the excitation of this nerve. This rise appears within a
few seconds after the onset of the stimulation and finds its origin in a rapid transfer
of blood from the abdominal organs into the channels of the general circulatory
system. The second rise appears about ten seconds after the first, and is due to the
constriction of the blood-vessels of the general system by the adrenin liberated in
consequence of the excitation of this nerve. Obviously, only the left adrenal body is
involved, because the innervation of these organs by the splanchnic nerve is uni-
lateral.

Record the blood-pressure. Quickly tighten the silk ligature so as
to crush this nerve. Observe the gradual fall in pressure which is

THE CIRCULATION 123

brought about by the fact that the abdominal blood-vessels innervated
by this nerve, lose their tonus and relax. Consequently, a certain
quantity of blood will now find its way from the general circulation
into the relaxed blood-vessels of the splanchnic organs.

Apply the shielded electrodes to the distal (abdominal) end of the
divided nerve. Replace the abdominal organs and cover the abdomen
with a warm, moist cloth. Record the blood-pressure and stimulate
the splanchnic nerve as described above. Owing to the lower general
pressure, the rise will now be more pronounced. Disconnect the man-
ometer and ligate the carotid artery.

2. The Vasomotor Supply of the Kidney. — Procure an oncometer
large enough to contain the kidney of this animal. Fill the outer com-
partments of this instrument with warm water until their membranous
inner walls have become moderately distended. Separate the left
kidney from the fatty tissue surrounding it, but do not injure its cap-
sule. Place the lower hemispheric part of the oncometer underneath
this organ. Adjust its cover so that the, kidney assumes a central
position between the rubber membranes, taking special care that its
blood-vessels as well as the ureter pursue a perfectly normal course
through the sht-Uke lateral orifice of the oncometer. Connect the
compartment in the cover of this instrument by means of a piece of
rubber tubing with a membrane tambour or piston recorder. It is not
essential that this connecting tube be filled with water. Cover the
abdomen with a warm, moist cloth.

Register the excursions of the recording lever upon the smoked
paper of a slowly revolving kymograph. Observe that the volume of
the kidney undergoes cardiac and respiratory variations, i. e., it is
increased during each systohc phase of the heart and suffers a more
general increase during the entire inspiratory period.

Temporarily obstruct both femoral arteries. Note the effect upon
the volume of the kidney. Explain. Temporarily occlude the carotid
arteries. Observe the change in the volume of the kidney. Explain.

Adjust the shielded electrodes to the distal end of the divided left
greater splanchnic nerve. While registering the volume curve of the
corresponding kidney stimulate this nerve with a quickly interrupted
current of moderate strength. Account for the decided reduction in
its volume. Kill the animal by an excessive amount of ether.

Dissect the region of the left kidney and adrenal body. Identify
the organs on the opposite side, and also the suprarenal, mesenteric, and
celiac ganglia and plexuses of the solar sympathetic system. Trace
the greater splanchnic nerve into the thorax, identifying the thoracic
sympathetic nerve and stellate ganglion. Enucleate the adrenal bodies.
Bisect them and identify their cortical and medullary portions.

3. Vasomotor Phenomena in Man.— Fill a large beaker with ice-
water and another with water heated to 40° C. Introduce your hands
for a short time. Withdraw, and note the effect upon the color and
condition of the skin. Explain.

LESSON XXIV

THE CIRCULATION (Continued)

THE INDIRECT METHOD OF MEASURING BLOOD-PRESSURE.
OF POSTURE AND EXERCISE

EFFECT

1. The Application of the Sphygmomanometer. — Place the index-
finger of your left hand upon the skin over the brachial artery of the
subject. Palpate the radial pulse with the index- and middle fingers
of your right hand. Gently compress the brachial artery until the
radial pulse can no longer be felt.

Place the index-finger of your left hand upon the skin over the
brachial artery. With- your right hand adjust the chest-piece of a

Fig. 81. — Riva-Rocci's Sphygmomaxometkr, Early Type.

Study of Blood-pressure.")

'Clinical

stethoscope upon the flexor surface of the elbow-joint. Do you hear a
sound? Gently compress the brachial artery. Describe the character
of the sound now heard. Explain its cause.

The sphygmomanometer most commonly used in making these tests
consists of (a) a mercury manometer, (6) a narrow rubber cuff to fit
around the arm, and (c) an inflating bulb with exhaust valve. In the
sphygmotonometer the place of the mercurial indicator is taken by a steel

125

126

ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

spring which must be caUbrated from time to time by comparing its
movements with those of a column of mercury under equal degrees of
pressure. Since the mercury manometer usually consists of one vertical
limb leading away from a central reservoir, the pressure may be read
off directly without correction. Some instruments, however, contain a
U-shaped tube, in which case the pressure, as read off from the ascend-
ing limb, must be multiplied by 2.

Fig. 82. — Sphygmomanometer, Recent Type. {Manufactured hyW. A. Baum Co., N. Y.)

The subject should be comfortably seated in a chair with his right
forearm resting upon a table. Adjust the armpiece of the sphyg-
momanometer (modification of the Riva-Rocci instrument) to the arm
of the subject. Be sure that the lower edge of the cuff does not encroach
upon the elbow and is not applied too loosely. Two methods may be
followed in determining the blood-pressure, namely, palpation and
auscultation.

(a) Palpation. — Having adjusted the armpiece accurately, locate the

THE CIRCULATION 127

radial pulse with the fingers of the right hand. Close the exhaust valve
and compress the rubber bulb rapidly to raise the pressure to about
140 mm. Hg. In a young person possessing an elastic vascular system
and in the sitting position, we would not expect to find a pressure higher
than this. Consequently, the pressure in the cuff overcomes at this
time the internal pressure. The brachial artery is fully compressed
and the radial pulse obliterated. 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 again after intervals until you have acquired this technic thor-
oughly and are able to obtain correct results. This gives the systoUc
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 systohc 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 pressure from that of the systolic.
This gives the pulse-pressure, which varies under ordinary conditions
between 35 and 40 mm. Hg.

2. Effect of Posture. — Determine the systohc 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 system?

Crampton has attempted to obtain an approximate estimate of the
condition or vascular tone of a person by balancing the increase in the
heart rate with the increase or decrease in blood-pressure resulting on
standing up. The range of the systolic 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
he close to 20,000 mm. Hg in a minute, and the lowest somewhere
about 10,000.

3. The Effect of Exercise. — Determine the normal systohc 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 thirty 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 the 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 heart by palpation of the radial pulse. How is the rate
affected by the act of swallowing?

Study the construction of the sphygmograph. 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 ascertain the
speed of the pulse-wave by computing 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?

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 this 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 by means of a cannula and a piece of rubber tubing with a record-

THE CIRCULATION 131

ing tambour. Another convenient form consists of a long rubber tube about 2
cm. in diameter and closed at one end. Its other end is connected with a recording
tambour by means of small tubing (Fig. 84). The interior of the large tube is occu-
pied 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, causing the membrane
of the recording tambour to be displaced inward. On expiration, the recoil of the
tube, aided by the spiral, increases the pressiu-e within its lumen and forces the
rubber membrane of the tambour outward. Marey's stethograph (Fig. 85) 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 consequence of the respira-
tory movements, are communicated 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.— Wintrich's Modification of Hutchinson'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 close contact with the inner surface
of the wall of the thorax.

(6) Forced Respiration. — Lower and raise the "diaphragm" more
forcibly, thereby producing a more ample expansion of the ''lung" and
more decisive variations in pressure.

(c) Dyspnea and Asphyxia. — The former condition may be repro-
duced in a mechanical way by partially closing the stop-cock with which
the inlet tube is equipped. This would correspond to an incomplete
closure of the trachea and would greatly impair the interchange of the
respiratory air. Note the resistance now acting against the ''dia-
phragm." Obviously, this diminution in the caHber 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 hangs. — 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 stomach 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. Retract the margins of the wound and
depress the liver. Observe: (a) The muscular 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

136 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 individual 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 immediately 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 lie 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 hquid (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 wafl. Note that the pink
pulmonary tissue lies in absolute contact with it. Twist the cannula
slightly, 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 the 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 CO 2 accumulates in the

RESPIRATION 137

system, stimulating the respiratory center to increased activity, these
reflex movements frequently assume a spasmodic character.

Inspect the internal aspect of the chest wall, and note the shape
of the thoracic cavity. Identify the pulmonary blood-vessels. Trans-
illuminate the border of either lung, noting its alveolar structure. Iden-
tify portions of the visceral pleura below the apex of the heart. Note
its structural peculiarities.

7. The Phrenic Nerves. — Isolate both phrenic nerves above the
diaphragm and place them 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 in 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-
siderable additional weight. How would an atelectatic lung behave
under these circumstances? What use is made of these facts medico-
legally?

9. The Excised Lung. — Remove the metal cannula 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 inability to render them air free.

LESSON XXVII

RESPIRATION (Continued)

STETHOGRAPHY. METHODS OF ARTIFICIAL RESPIRATION. PULMOTOR.

1. Frequency of Respiration. — Study the movements of the thorax
and abdomen. Differentiate between diaphragmatic and costal breath-
ing. Measure the circumference 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. — Failiiharize yourself with the nor-
mal percussion sound of the lungs as obtained, 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 quietly 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 breaking 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 oxygen.

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 CO 2 has accumulated sufficiently
the subject will breathe more rapidly and more deeph' 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 hj^drate.
The carbon dioxid will be absorbed, while the oxygen in the bag is being
used up. Consequently, there will be no hyperpnea. Only a few
minutes will be required to establish this fact. Immediately 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

Fig. SS. — Position to Be Adopted for Effecting Artificial Respiration in Cases
OF Drowning. (Schaefer.)

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. — Anesthetize a mammal
and continue the anesthesia throughout the following experiments :
Perform tracheotomy. 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 immediate effort at inspiration. Explain
these results upon the basis of the self-regulatory function of the vagi
nerves.

3. The Trigeminal and Glossopharjnigeal Nerves. — Apply a stetho-
graph to the chest of this animal and register the respiratory movements
upon the paper of a slowly revolving kymograph. Stimulate 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
pharynx 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. — Make 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 laryngeal nerve pursues a course transversely across
from the vagus nerve, and enters the lateral aspect of the thyroid cartilage. It is
the largest nerve of this region. The inferior laryngeal nerve is isolated most
readily below the larynx. It pursues 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 larynx may be raised and an unob-
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 Hning 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.

U, Hyoid bone; M, thyrohyoid mem-
branes; PA, pomum Adami; T, thyroid
cartilage; C, cricoid cartilage; Tr, trachea;
CT, cricothyroid muscle; P, vertical plate
of cricoid with {A) arytenoid cartilages
placed transversely upon its articulating
processes; YC, vocal cords; R, 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 nerv^e; J and O, its inner
and outer branches; JL, inferior laryngeal
nerve; Br, vagal fibers innervating bron-
chial musculature.

with tljose commonly observed after the entrance of a foreign body into
the larynx.

5. The Superior Larjmgeal 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 (5) 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
produced in each case.

RESPIRATION

143

Annotation. — The superior laryngeal nerve is chiefly a sensory nerve, but also
embraces a certain number of motor fibers which innervate the cricothyroid muscle.
Consequently, the stimulation of the intact nerve must give rise to an inhibition of
respiration and forced expiratory efforts, and secondly, to an approximation of the
cricoid and thyroid cartilages and a greater tension of the vocal cords.

6. The Inferior Laryngeal Nerve. — Place the intact inferior laryn-
geal nerve in shielded electrodes. Stimulate briefly and note the effects
of the stimulation upon (a) the general character of the respiratory
movements, and (b) the action of the laryngeal muscles.

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.

Fig. 91. — Diagram Illustrating the Abduction and Adduction of the Vocal Cords.
A, Abduction: 1, point of insertion of the post, crico-arytenoid 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 cartilages.

Annotation. — ^The inferior laryngeal nerve is a motor nerve, innervating the
muscles of the larynx, except the cricothyroid. Consequently, its stimulation must
give rise to peripheral effects 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 Hgatures. Observe that the rate of the respiratory movements is
now greatly reduced, whereas their depth is increased. The total gas
interchange is not seriously impaired. Stimulate 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 picture 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 THE FISH

1. The Localization of the Respiratory Center.— Anesthetize a cat
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 laminae, re-
tracting the spinal muscles. Stop bleeding by applying dry tampons
or by torsion and ligation of the blood-vessels. Cut away the laminae
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 sufficiently long normal record having been obtained,
raise the spinal cord and divide it. The animal continues to respire
normally, 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 respiratory 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 directly.
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

146 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 aRCUIT

1. The Lung of the Frog. — Pith a frog. 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 clip. Remove both lungs with the heart and suspend them
until thoroughly dried.

Transilluminate them. Note the large central cavity in each as
well as the individual 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-shp 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 capillarity under the glass covering the sur-
face of this lung. Study the resultant phenomena of inflammation as
exempHfied by changes in 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 study 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 by 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; 3, 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
decreased 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 one-half and one-third of an atmosphere
(760 mm. Hg). Under normal conditions oxygen exerts a pressure of
20.94 per cent, of an atmosphere or about 153 mm. Hg. At 10 per
cent, (one-half of an atmosphere) the animal will become 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

L The Elimination of Carbon Dioxid and Water. — Exhale repeatedly
through a glass tube into a beaker filled with lime-water. Explain the
resultant turbidity.

Procure a 4-ounce Woulffe bottle with three necks and the necessary
delivery tubes and stoppers; three 5-inch calcium chlorid tubes with
side tubes and perforated stoppers; a Geissler bulb with KOH and
CaCh tubes, two small flasks with stoppers, and two glass tubes; a
2-hter bottle in which the animal is placed ; and two 8-hter bottles.

The tubes containing the calcium chlorid should be put in the dry-
ing oven at a temperature of 100° to 120° C. for several hours. They
are 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 CaCl2 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 (OH) 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 {%).

Place a white rat into the 2-liter bottle 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 CaCh bottles, and disconnect the tubing. Weigh tubes d, e,
f, and g. Obviously, parts a, b, and c remove the H2O 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 pyrogallate, made by 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

Fig. 93. — Apparatus 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 accompHsh this end fill the gas buret A with water by

Position 1. Position 2. Position 3

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
end with the rubber tube of the pressure bottle B, containing the potas-
sium pyrogallate. Expel the air from the connecting tube and turn
the three-way stop-cock so that the pyrogallate may flow into the buret.
Raise the pressure tube and finally clamp the connecting tube close to
the buret. 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. Analyze the oxygen content
of the normal air. Subtract the amount of oxygen of the respired
air from that found in the normal 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 the cerebral cortex, cells of Purkinje
from the cerebellum, motor cells from the anterior horn of the spinal
gray matter, and sensory 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. Make a median incision through 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 you have
brought into view the rounded, grayish optic lobes or corpora bigemini.
The cerebellum is rudimentary and occupies a position in front of these
bodies. Identify the optic nerves.

Expose the entire spinal cord by breaking away the vertebrae 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 responses. Draw conclusions regarding the part played
by the spinal cord in this reaction.

Annotation. — ^The solution of acetic acid should be weak, possibly 3 drops of
glacial acetic acid to about 20 c.c. 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 muscular 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 spinal cord
with the wire. This procedure, as may be surmised, destroys the spinal reflex ac-

155

156

ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

tions, because it produces a break between 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 destroyed 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; Ce, 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
ner\'e ; A , center for the parts of the trunk ;
SC and SN, 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 vertebrse. Its vertebral column 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
between the sixth and seventh vertebrse 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 and stimulate the distal end of each.
Observe that they innervate different groups of muscles.

A similar localization of function may be detected in the sciatic
center itself. Very fine needle electrodes should be used in mapping
out this area.

6. Summation of Afferent Impulses. — Destroy the brain of a frog
(not the cord). Adjust two thin copper wires to one foot about 1 cm.
apart and connect them with the secondary coil of an inductorium.
Stimulate with a subminimal-reflex 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 shocks in quick succession, and
observe the reflex action ultimately resulting in consequence of this
summation.

7. Effect of Thermal Stimuli. — Remove the wires from the frog used
in Experiment 6. 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 moderately 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 way and stimulate
the sole of one foot several times with 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 the stimulus.

10. Inhibition of Reflexes Upon Central Paths. — Expose and ligate
the sciatic nerve of one side. Divide the nerve distally to the hgature.
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
immersed in the acid?

LESSON XXXIII

THE NERVOUS SYSTEM (Continued)

REFLEX ACTION. REMOVAL OF CEREBRUM

1. Inhibition of Reflexes by Higher Centers. — Etherize a frog.
Make a median incision through the skin covering the skull-cap. Per-
forate with the point of a knife and enlarge the opening by means of a
pair of forceps. Identify the cerebral hemispheres and remove them.
After an interval suspend the frog and determine the reflex time in the
usual way.

Sprinkle a few crystals of sodium chlorid 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 must 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 muscular seizures. Blow your breath at the frog, or tap
upon the table upon which it is resting. Upon which elements of the
reflex circuit does the strychnin exert its action?

3. Reflexes in Man. — Let the subject open his mouth. Touch the
uvula with the end of an aseptic glass 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 volitionally (in-
hibition by the cerebrum).

Shield the eye of the subject for a few seconds with your hand.
Suddenly withdraw the latter, allowing Ught to enter the pupil. Ob-
serve the decrease in the size of this orifice, brought about by the con-
traction of the circular muscle ceUs 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 (ciUospinal reflex).

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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 by 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
tickhng 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 derived 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 161

of the foot. Apply the same stimulus to the trunk of the sciatic nerve.
The intensity of the stimulus required to evoke reflex action is usually
less when applied to the sense organs.

Make a median incision through the skin covering 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 about 1 cm. square, containing the terminals of this
nerve. Raise this skin-flap, 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 be 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-cap 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 line 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 repeatedly 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 well it adapts the axis of its body
to the surface. Repeat this test by 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 (compensatory 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 light. It will avoid the
object casting the shadow (retinal reflex).

(g) 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 under 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
cerebrum, 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. While this ani-
mal may escape from the basin, this result is accidental, and is due
solely to the reflex contractions of the muscles.

LESSON 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 adjustable electrodes
and connect them with the secondary coil of an inductorium. 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 muscles 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 tambour. Register these pulsations upon the smoked paper
of a kymograph. The cranial 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 suture. Make a median incision through the
skin covering the spinous processes of the lumbar vertebrae. 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 Ugature. Stimulate each with a weak
tetanizing current. Eventually tie these ligatures, 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.

LESSON XXXV

THE NERVOUS SYSTEM (Concluded)

REACTION TIME

1. Reaction to Touch. — Arrange the electric apparatus for stimula-
tion with single induction shocks. Insert a signal and two simple keys
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. The 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.

Fig. 99. — Reaction to Touch.
Record of signal below that of tuning-fork {^^^ 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 arid 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 sipall
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 bridge of one key in the position of closure. Shield the other key
and apparatus from the subject by a large cardboard. 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.

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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 key 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
stimulation with single induction shocks and insert a signal and two
simple keys in the primary circuit. Connect the secondarj^ 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 hgament
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 eyeUd 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 different
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 blunt end of a pencil upon
the area stimulated. Measure with a milUmeter 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 stimulated 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 caUper ascertain "how

Fig. 100. — Esthesiometer with Guarded 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 camePs-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 Hne 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-
fined 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 gre^.ter.

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

THE SENSE ORGANS 169

only the sensation of pressure at the surface of the mercury will remain
behind; in fact, 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 tip of your index-finger. 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 prob-
ability to the activation of the nerve plexuses investing the roots of the
hairs.

Feel any surface with the tip of your index-finger. Draw the finger
across the surface. Note that the sensation of simple contact is now
ampHfied by sensations 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. e., 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 dorsal aspect of your hand
with the blunt point of a pencil. In certain areas you will obtain a
sensation of cold, and in others, of heat. These spots are 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 longer 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 elsewhere upon the hand. Stimulate
with a weak induction current until a distinct sensation of cold is ob-
tained.

13. "After-images" of Temperature. — Place a cold coin on the

170 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

forehead or on the pahn 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 shghtly
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
quickly 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 w^ater 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. niusions 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 SENSE ORGANS 171

leaf patterns of equal size. Draw from left to right with a ''free hand'^
motion of the arms, produced by simultaneous impulses directed equally
to the two sides. Note the relative size and position of the figures.

Repeat this experiment, but place one hand about 12 cm. above the
other. Obviously, the muscle sense is not well trained in the average
person.

22. Sensation of Motion at the Elbow. — Place the forearm upon a
board which it is possible to move, thereby imitating the flexion of the
forearm upon the arm. Close the eyes. While an assistant raises or
lowers the free end of the arm-board, state when you 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 eyes 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
hand 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 taste-buds.

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 sohd 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 where each is tasted most acutely.

3. "Threshold Value" of Taste. — Moisten the tongue with J tea-
spoonful of a 1 : 1000 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 : 600, 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, viz., weak and strong solutions of cane-sugar, sodium chlorid,
tartaric acid, and quinin. The subject should indicate the taste which
he perceives. Does the papilla experimented 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, apply
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 dry 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 sylvestris 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? W^here 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 quahty
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. Compoimd 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 obhterated, the lowest tone
being an octave higher.

16. Observation of the Membrana Tympani in Man.— Fasten the
reflector to your forehead, and direct the rays from a lantern into the
right external auditory meatus of the subject. With your left hand pull
the external ear backward and upward, and with your right hand insert
the funnel-shaped tube, taking great care not to injure the skin of the
meatus or the membrana tympani. Concentrate the hght upon this
membrane by moving the reflector either nearer to or farther away from

Membrana flaccida Posterior ligament

Anterior ligament-

'Long process of incus

- End of manubrium of malleus

Fig. 101. — Membrana Tympani, as Seen with the Otoscope. (Heusman.)

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 the 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 pecuHar 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; T, auditory
nerve; dividing into two branches, one
of which innervates the cochlea, and the
other the semicircular canals; 8, parotid
gland.

Lamp

Fig. 103. — DiagramSiatic 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

Laryox,

Fig. 104. — Diagram of Laryngoscope. {From StewarVs 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

THE SENSE ORGANS 177

forehead. Slightly warm the laryngeal mirror, and pass it into the
subject's mouth, carrying the mirror horizontally backward until its
back touches the base of the uvula. 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 epiglottis
with its ''cushion,'' and the glosso-epiglottidean folds of mucous mem-
brane. Identify the white and shining ''true" vocal cords, the pink or
red "false" vocal cords, the aryepiglottidean folds, and the mucous
membrane covering the arytenoid cartilages and cartilages of Santorini.

Observe the differences in the form of the glottis :

1. During quiet and forced respiration,

2. While the subject sings a low and a high note, and

3. While the subject sings the vowel sounds: A, E, I, O, U.

12

LESSON XXXVIII

THE SENSE ORGANS (Continued)
THE STATIC AND DYNAMIC SENSES

1. Dissection of the Ear of the Dog-fish. — Remove the cartilage be-
tween the eyes. Identify the different parts of the brain. Proceed
toward its hinder part, carefully removing the cartilage from within
outward. Having reached one of the semicircular canals, remove its
upper wall as far as possible. Identify its membranous canal with its
ampulla. Follow this canal until it joins a membranous sac, the utricle.
Carefully expose the other semicircular canals. Open one of the am-
pulla and identify the crista acustica, a transverse ridge carrying the
sensory epithelium.

Fig. 105.

-Position of the Three Semicircular Canals in the Skull of the Pigeon.

{Ewald.)

2. The Position of the Semicircular Canals. — Procure a human skull
in which the semicircular canals have been exposed, i. 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.

Identify 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 Djmamic 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 about ten times around its axis. Imme-
diately tilt the box so that the rabbit slides out upon the table. Observe

THE SENSE ORGANS 181

the nystagmus, the change in the direction of the long axis of the rab-
bit, the change in the position of its head, and the compensating mus-
cular movements made by it in order to retain its equilibrium. Do not
repeat this experiment many times.

Stand 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 do
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 your 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 the 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.

6. 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 board. 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 bone of this region, thereby exposing a white
otohthic 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 identified
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 chamber of the eye by a transverse incision through 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, anterior cavity; P, posterior cavity; L, lens; J, iris; T, conjunctival sac;
CL, ciliary ligament; CB, ciliary body; CM, ciliary muscle; OS, ora serrata; CS>, canal of
Schlemm; R, retina; Ch, choroid; aS, sclera; ON , 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 cc^or 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 Retma. — Place a fresh ox eye
in a watch-glass. Make a small square opening in its upper wall directly
behind the ciliary 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) slightly in different directions and
observe the direction of the movement of the image.

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 shghtly 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 the lens. The first two images are upright and the
third inverted.

In a thoroughly darkened room place your eyes about 25 cm. in
front and to the left of the right eye of the observed person. With
your left hand hold a large cardboard directly beside the right side of

Fig. 108. — Reflected Images of a Candle Flame as Seen in the Pupil of an Eye at
Rest and Accommodated for Near Objects. {Williams.)

your head. With your right hand hold a lighted candle somewhat to the
right of the cardboard, ^. 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 images,
viz., one from the cornea, one from the anterior surface of the lens, and

Fig. 109. — Diagram Illustrating Course of the Rays Through the Phacoscopb.
A, Observed eye; B, opening allowing accommodation for near and far objects; C,
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 near 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 (Helm-
holtz).

Annotation. — ^The phacoscope consists of a roughly triangular box. The ob-
server's eye is placed in the aperture at A and focalizes a far object through aperture
B. Orifice C contains two prisms, through which light is reflected upon the eye of
the observed person. The observer notes the images through 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
surface of the lens becomes more rounded and moves toward the corneal image.
This change proves that this refracting surface 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 volitantes)?
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
tune. 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, bearing 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 flat
piece of window glass (cornea). In the holder directly 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. Move 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. — Move the screen farther forward and then
farther backward. Note that the rays now strike the retina widely
apart, i. e., they 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 the rays under these two conditions.

10. Near Point. — Again adjust the screen (retina) in such a way that
the raj^s of light emitted by 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 hypermetropia 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 hypermetropic 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 exactly
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 (Continocd)

VISION

1. The Ametropic Eye. Astigmatism.— Adjust the optical lantern
and box to form an emmetropic 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 fine. Draw a diagram to show the
course of the refracted parallel rays.

Repeat the preceding tests by holding a cyhndric 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 ^'with-the-rule^' and "against-the-
rule'^ regular astigmatism. It will be remembered that the astigmatism
which the physician 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 cylindric 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 mm. 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 light 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 the 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 PHYSIOLOGY

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 focalized 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 eyeUd. 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. While 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
vertically 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 clearly 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

way. The sheet of paper, however, must then be adjusted in front of
this eye and bear a cross mark near its right margin.

If a perimeter is available, the subject should be comfortably seated
at a table with his chin resting upon the support. Either the right or
the left eye should then be focalized steadily upon the white dot in the
center of the semicircle. The metal arch bears a sliding path in which
is moved the object, generally a small white square, from without
inward, its movement being indicated in degrees upon a scale inscribed
upon the arch. The point at which the object becomes first visible

oooo

Fig. 111. — The Perimeter.

is then indicated upon a small piece of paper upon which different
meridians have been drawn out to correspond to those of the metal arch.

Study the general outline of the visual field of each eye. Why is
it not round, but oval, with its more pointed area toward the nasal side?
Do you note any irregularities in its outline which cannot be ascribed
to a faulty technic? Enumerate the causes which might be held re-
sponsible for such restrictions of the visual field.

6. 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 fixedly 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 clearly, 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 lacrimse 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 and move it slowly toward them 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 Hues 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 Types. — 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 = -7. 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 placing a suitable lens behind the opening
in the mirror.

7. Ophthalmoscopic Examination of the Ametropic Artificial Eye by
the Du-ect Method.— Render the artificial eye ametropic by pushing
its two parts closer together or by separating them more widely. Ex-
amine its retina with the ophthalmoscope held at a distance of from
30 to 50 cm. in front of it. When the details of the fundus have be-
come visible, move your head together with the ophthalmoscope from
side to side. In the hypermetropic eye the retinal vessels will appear

Fig. 114. — Loring's Ophthalmoscope, with Tilting Mirror, Complete Di8k of
Lenses from — 1 to — 8 and 0 to + 7, and Supplemental Quadrant Containing ±
0.5 and =fc 16 D. This Affords 66 Glasses 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 eye is myopic
or hypermetropic, measure the degree of this ametropia in the following
manner:

Place the ophthalmoscope in the anterior focal plane of the artificial
eye, i. 6., 5 cm. in front of its cornea. Illuminate the pupil and accom-
modate your own eye for a distant point. If the 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 ordei- to
be able to see the fundus of the eye of the subject clearly, is the lens
needed to overcome the ametropia of this 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 studj^ 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 light 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 fight is reflected against a wall by means of a mirror. Draw
a diagram to show the real movement of the li^ht upon the retina,
note that its movement, as seen through the pupil, is the same as that
of the fight 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 ORGANS 197

point of reversal because it emits divergent rays. Now interpose a
convex lens in front of the artificial eye, thereby 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 sufficiently to inter-
sect. In order to obtain the degree of hypermetropia existing in this
eye, determine the point of reversal as in normal myopia. Subtract
the degree of myopia from the total strength of the lens. The remainder
of the focal strength of the lens is the strength which is required to over-
come the hypermetropia. 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 hes 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 fixedly
at the cross lines, allowing the dot to lie in the outer visual field. 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 field. What position does the yellow spot
occupy in relation to the blind spot, and how is this disturbance over-
come in binocular vision.

With your 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 completely.

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 distance
at which both dots disappear.

2. The Contours of the Blind Spot. — Place the chin of the subject
upon a support and adjust a sheet 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 oblique lines. 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 flat 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 yellow 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 yellow, through which dark figures are passing. The latter
assume the character of a network, in agreement with the branching
blood-vessels (Purkinje's figures). By this means shadows of the
blood-vessels are cast upon regions of the retina not ordinarily exposed
to them. It is essential, however, that these shadows move, because
the retina quickly adapts itself to continued stimulation.

Make a pinhole in a card and hold it directly in front of one eye, 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 light emitted by the figure are focalized in the fovea, i. e., in the
region of the greatest acuity of vision. When\<made to fall upon out-
lying districts of the retina the rays cannot form a precise image.

Gaze at an object in a brightly illuminated room. Note that the
object is unconsciously brought into direct line with the fovea. Darken
the room. Note that at first your vision is very poor, but gradually
adapts itself to the low intensity of fight. Also observe that you now
endeavor to focalize objects by bringing them upon the outer zones of
the retinae.

Focalize a single word upon a page of print. Note that only the
word looked at is perfectly clear, while those farther away from it in
any direction are not clear.

Draw radiate lines upon the blackboard and equip each with cross
marks at distances of 5 degrees from one another. Fix any one of the
cross marks and note that the others are at this time not perfectly clear.

6. Associated Movements of the Eyes. — Close one eye and place
the tip of your index-finger upon the upper eyelid. Note that the focal-
izing of an object with the other eye invariably produces a co-ordinated
movement in the closed eye.

7. Positive After-images. — Having rested the eyes for a short time,
look suddenly at a lighted incandescent lamp and shut the eyes again
after a distinct image of the lamp has been formed. Note the after-
effect.

THE SENSE ORGANS 201

Close the eyes for a few seconds. Look at a gas flame in which some
common salt is burning, and then at a sheet of white paper. Does the
after-image move with the eye?

Obtain an after-image by suddenly turning off the gas in a dark room,
or by gazing at a window for half a second and then closing the eyes.

8. Negative After-images.— Having rested the eyes, gaze for about
half a minute at a small white square on a black background. Suddenly
place a sheet of white paper over the black. How does the present
after-image differ from those obtained previously.

Look at a black square on a white ground; then suddenly let the
eyes rest upon a gray screen. Observe the after-image, and note the
apparent increase in its size when the gray screen is moved farther
away from the eye.

Gaze at a bright red square upon a black ground; then look at a
white surface. Does the bluish-green after-image show periodic varia-

FiG. 115. — Rothe's Rotatory Apparatus for Color Disks. It is so Arranged as to
Give Various Rates of Rotation by Combining the Motions of 1, 2, and 3.

tions? Repeat the experiment with a green square. Note that the
color of the after-image is complementary to that of the square.

Place the red and green squares side by side on the black surface.
Look at them steadily for about twenty seconds, and then shp a sheet
of white paper over the whole.

9. Fusion of Gray and White. — By means of Maxwell's color mixer
rotate the black and white disk supplied for this experiment until you
have obtained complete fusion of the black and white in the outer zones
of the disk.

Increase the frequency of the revolutions of the disk until even the
central zones appear of a uniform gray color. Darken the room some-
what, and determine how many revolutions are necessary to produce
a gray of the same quality as before.

10. Fusion of Colors.— Rotate two large disks, colored respectively
red and green, and adjust the colored areas so as to obtain a dark yel-

202 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

low. Match this color by inserting two small disks, black and yellow
respectively. Obtain a blue color by means of two large disks colored
green and yellow. Match the blue color by means of two small disks,
respectively blue and black.

Use three disks colored red, green, and violet. The wave-lengths of
these colors should correspond as closely as possible to those of the
corresponding colors of the solar spectrum. Arrange the colored areas
in the proportion of red, 118 degrees; green, 146 degrees; and violet,
96 degrees. Rotate the disks until you have obtained a gray color.
Match this gray by means of two small disks, colored black and
white.

11. Complementary Colors. — Select from the series of colored disks
provided for this experiment one of a blue color. Determine what
color, when mixed with this blue in definite proportion, will turn it
gray or nearly white. The color-mixer should make from 40 to 50
revolutions in a minute. If the gray remain slightly tinged with color,
add a small section of a third color disk, neutralizing with green if the
tinge inclines toward red, and with red if the tinge exhibits a greenish
hue. Determine in the same manner the colors complementary to red,
yeUow, orange, and green.

12. Intensity of Light and Quality of Color (Purkinje*s Phenom-
enon).— Take two small squares of red and blue paper respectively,
which in a moderately bright light possess nearly the same intensity
of color. Observe them again in a partially darkened room. Which
color appears to be the brighter?

13. Color-blindness. — Place Holmgren's worsteds upon a well Hghted
sheet of white paper. Employ as a test color hght green, i. e., a, mixture
of white and pure green, and ask the subject to soject from a lot of skeins
all those which appear to him to be of this light green color. If he
choose one or more ''confusion-colors" — in this case pink or yellow —
he should be given a skein of a pale rose color, and be asked to pick out
all the skeins which he thinks would match it. If the subject be red-
bhnd, he will select blue and violet; if green-blind, gray and green.

Ask the subject to match a bright red skein. If red-blind, he will
choose green and brown ; if green-blind, red and light brown.

14. Contrast. — Of two equalty large strips of gray paper, place one
upon a sheet of white paper, and the other upon a sheet of black. Which
strip appears to be the brighter ?

Place these sheets close together, each sheet bearing its gray slip.
Gaze at both slips for twenty seconds, and .then shut the eyes. Which
after-image seems the brighter?

Place a cross of gray paper in the middle of a large sheet of green
paper and cover both cross and background with tissue paper. Note
the color now imparted by the cross. Place the gray cross upon a red
background instead of a green. Cover the whole with tissue paper as
before and note the color of the cross.

Place a strip of gray paper across the junction of a red and a green

THE SENSE ORGANS 203

sheet of paper and cover the whole with tissue paper. Note the ap-
parent color of the strip.

15. Irradiation. — Place a circular piece of black paper 1 cm. in
diameter upon a white circle of paper 2 cm. in diameter, and a white
circle 1 cm. in diameter upon a black circle 2 cm. in diameter. Hold
the circles at some distance from the eyes and note their apparent size.

Divide a square into four small squares of equal size, and blacken the
left upper and the right lower of these four fields. Observe that the
white squares appear to be larger than the black.

16. Single and Double Images. — Adjust your vision so as to see
clearly with both eyes a vertical rod held 60 cm. in front of them.
Hold upright the index-finger of one hand in the binocular fine about
35 cm. from the eyes, and observe the double image of the finger.
Close the right eye and note whether the right or the left ihiage dis-
appears. Accommodate for the finger, and observe the resulting double
image of the rod. Close one eye and note which image disappears.
Explain.

Accommodate for an object placed about 2 m. in front of the eyes.
Hold a pencil upright in the binocular line about 30 cm. from the eyes.
Move the pencil slightly toward the right eye. Observe that one image
disappears when the images lie asymmetrically to one side of the fine
of vision only, the image in the right eye being perceptible in the
present case. Close the right eye and in this way render the second
image perceptible.

17. Binocular Fusion of Dissimilar Images. — Fasten a red and a
green postage stamp upon a piece of cardboard at a distance equaling
the interocular distance. Observe them in the stereoscope and note^
that their images are fused into a single one.

18. Relation of Binocular Vision to Judgments of Direction. — Draw
a sheet of paper, with a pinhole in it, horizontally past the eyes, starting
well to the right of the eye. To what plane of the head are the two
successive images referred?

19. Relation of Binocular Vision to Judgments of Solidity.— Ex-
amine a series of pictures in the stereoscope. Draw a diagram to show
the manner in which judgments of solidity are formed.

20. Relation of Binocular Vision to Judgment of Distance.— Close
one eye and hold the index-finger of the left hand vertically in front
of the other eye. Try to strike the left index-finger with the index-
finger of the right hand.

Close one eye and try to dip the index-finger of one hand into the
mouth of a bottle held about 25 cm. in front of the other eye.

With the left hand hold a pencil vertically about 25 cm. in front of
the eyes. Gaze at the pencil for a few seconds, close the left eye; then
cover the lower part of the pencil with your right index-finger held
vertically between the object and the eyes. Try to strike the pencil
with the finger.

21. Influence of Convergence of the Visual Axes. — Gaze at an

204

ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

object through two blackened tubes of paper. Cause the tubes to
converge slowly and observe the apparent increase in the size of the
object.

/K .\

//
//
//
//

//

/

\

\

\

\

\ //

\

\

\ A

/

/

V vK

\

\

/

X N^ ^^

\\

\

\

/

Fig. 116. — Zollner's Lines.

22. Optical Illusions. — Examine a series of figures, such as the fol-
lowing, and give reasons for the illusion :

D B

Fig. 117. — To Illustrate the Illusion of Subdivided Space.

(a) Make two lines parallel and draw short oblique lines through
them. Note that the lines now slope in accordance with the direction
of the oblique lines (Fig. 116).

(6) Make three black dots (A, B, and C) at equal distances from

, THE SENSE ORGANS 205

one another. Between A and B make several dots of equal size. A
and B will then appear farther apart than B and C (Fig. 117).

(c) Draw two horizontal hnes of equal length and parallel to one
another. Upon the ends of one draw obhque hnes outward and upon

Fig. 118. — Muller-Lyer Figures to Show Illusion in Space Perception. The Lines

A AND B ARE OF THE SaME LeNGTH.

the ends of the other similar Hnes turned inward. The latter will then
appear to be shorter than the former.

(d) Draw two lines of equal length parallel to one another. Next
to this figure draw another of the same dimensions with several inter-

Fig. 119. — To Illustrate the Overestimation of Vertical Lines.

coursing lines. Note that the second figure appears to be larger than
the first (Fig. 117).

(e) Place a vertical line beside a horizontal line of the same length.
The former appears to be the longer (Fig. 119).

LESSON XLIII

DIGESTION

DEGLUTITION

1. Isolation of the Esophagus.— Anesthetize a mammal and main-
tain the anesthesia throughout the following experiments: Perform
tracheotomy low down. Separate the trachea from the esophagus, and
excise the piece of trachea situated between the cricoid cartilage and
the metal cannula. Palpate the esophagus, noting its texture and
movability.

Expose both vagi nerves and place them in loose ligatures. In
addition, expose their superior laryngeal branches and place them in
loose ligatures.

Make a median incision through the linea alba. Follow the an-
terior wall of the stomach until the esophageal gastric junction has
been reached. Insert a straight cannula in the orifice of the esophagus,
and connect it with a manometer containing water. Cover the ab-
dominal wound with a cloth moistened with warm saline solution.

2. Wave of Deglutition. — Open the mouth of the animal and touch
the fauces with a moistened plug of cotton. Observe the swallowing
movements evoked thereby. Note that they begin in the mouth and
travel downward in the form of a peristaltic wave, involving the different
segments of this passage consecutively.

Observe the displacement of the column of water, and determine
approximately the interval of time between the beginning of this act
and the moment when the wave has reached the level of the larynx,
and again when it has arrived at the cardiac end of the stomach. In
which segment is its progress slowest?

Evoke these movements by stimulating the central end of the
superior laryngeal nerve.

3. Division of Esophagus. — Cut transversely across the cervical
portion of the esophagus. Stimulate the central end of the superior
laryngeal nerve, evoking peristalsis. Does the wave proceed as before,
or is it blocked at the line of the section? Explain.

Raise the orifice of the lower segment slightly. Insert an eUiptic
piece of smooth wood secured by means of a thread. Does the intro-
duction of this body lead to a wave of deglutition in this segment?
If not, excite a wave in the normal way, either by stimulating the
superior laryngeal nerve or by stimulating the mucous membrane of
the mouth. Is the wood now propelled onward? Explain.

4. Influence of the Vagi Nerves.— Divide the right vagus nerve.
Excite deglutition by stimulation of the superior laryngeal nerve. Study
the character of the wave. Divide the left vagus nerve and repeat this

207

208 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

stimulation. What differences do you observe? What part do the
vagi nerves play in deglutition ? Kill the animal by an overdose of
ether. Open the thorax and trace the esophagus through the chest.
Measure its total length, and determine the velocity of the wave of
deglutition.

5. Deglutition in the Human Subject. — Let the subject take a
swallow of water while you auscultate first over the region of the larynx
and again over the cardiac orifice of the esophagus. Describe the
character of the noises heard. Determine the approximate interval
between them. Chew a piece of bread and swallow in the usual way.
Determine the interval between the aforesaid noises. The time of
deglutition is much longer in the latter instance.

6. Percussion of the Human Stomach. — Let the subject take sodium
bicarbonate in conjunction with tartaric acid and assume the horizontal
position. Percuss the region of the stomach, outlining this organ with
colored chalk. Determine the position of the pyloric orifice. What
relation does the lower boundary of the stomach bear to the umbilicus?
Where would this boundary be found in a dilated organ? Explain the
fact that gas is not erupted until the subject assumes the recumbent
position.

LESSON XLIV

DIGESTION (Continued)

SECRETION OF SALIVA

1. Isolation of the Secretory Nerves.— Anesthetize a mammal and
maintain the anesthesia throughout the following experiments until the
animal has been killed. Perform tracheotomy. Expose the left com-
mon carotid artery and insert in its central end a straight cannula. On
the opposite side make a longitudinal cut through the skin a Httle to
one side of the median line, and beginning at a point opposite the canine
teeth. Prolong it backward to the angle of the jaw. Cut through the
platysma myoides. The next layer of muscle-fibers is arranged trans-
versely. Carefully spht this layer (muse, mylohyoideus) with forceps,
reflecting its halves to the right and left. Let the assistant place his
index-finger upon the floor of the mouth and pull it away from the side
of the lower jaw. Identify the hngual nerve which passes transversely

Fig. 120. — Schema Illustrating the Nerve Supply of the Submaxillary Gland.
SG, Submaxillary gland ; supplied by a small artery from the carotid system (CA) .
It is drained by a small vein which generally enters the facial (FV) at its point of con-
fluence with the lingual vein (LV). The external (ESV) and internal (JSV) maxillary
veins invest the gland and unite to form the external jugular vein (EJV). The sympa-
thetic nerve supply is derived from the sup. cerv. ganglion (SCG). The chorda tympani
(CT) attaches itself to the lingual nerve LN and then to Wharton's duct (TT); S, lower
jaw.

across the floor of the mouth at about the junction of the middle and
posterior thirds of the jaw. Follow the latter in a central direction until
you reach ,the chorda tympani nerve and the duct of the submaxillary
gland (Wharton's). Isolate the chorda tympani nerve at the point
where it leaves the lingual nerve, and place it in shielded electrodes.
Ligate the duct of the submaxillary gland and stimulate the chorda
tympani for a few seconds, so as to distend the duct with saliva. Insert
a cannula. Expose the vagosympathetic nerve of the same side, cut
it, and arrange for stimulating its central end (toward the head) with a
weak tetanizing current. "

14 209

210 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

2. Function of the Chorda Tympani Nerve. — Stimulate the chorda
tympani for fifteen seconds and count the number of drops of sahva which
escape during this time. Observe the degree of viscosity of the sahva.
Pour it from one beaker into another, noting its viscidity. Repeat this
test.

3. Function of the Sympathetic Nerve. — Stimulate the central end
of the sympathetic nerve and count the number of drops of saliva. Ob-
serve its viscosity and viscidity. Contrast it with the chorda sahva.

4. Secretory Pressure. — Record on the kymograph the blood-
pressure prevailing in the carotid artery of this animal. Disconnect
the carotid artery from the manometer and connect the latter with the
duct of the submaxillary gland. Stimulate the chorda tympani for a
considerable time, with occasional intervals of rest, and record the
pressure under which secretion still takes place. Allow the drum to
revolve very slowly. The pressure in the salivary duct may be raised
a considerable distance above the general blood-pressure, proving thereby
that filtration is not the only factor concerned in the formation of this
secretion. Enumerate the other factors.

5. The Vasomotor Changes in the Submaxillary Gland Produced by
Stimulation of the Chorda Tjmipani and Sympathetic Nerve. — Reflect
the skin and expose the large veins in the vicinity of the submaxillary
gland. Ligate the internal maxillary and facial veins opposite the
anterior end of the gland, and hgate the sublingual vein about 2 cm.
distally to its junction with the facial vein. Carefully destroy by tor-
sion the larger cutaneous veins which empty their contents into the
aforesaid veins centrally to the ligatures. The vein which returns the
blood from the submaxillary gland pursues a very irregular course. In
most cases, however, it joins one or the other cf the above-mentioned
veins at a point nearer to the heart than where the hgatures have been
applied. If this relationship prevails in the mammal used for this
experiment, only the blood returned from the submaxillary gland will
be able to enter the external jugular vein.

Insert a cannula in the distal end of the external jugular vein near
the point where the internal and external maxillary veins unite. Con-
nect the cannula with a bottle having an inlet and an outlet tube, and
containing a solution of magnesium sulphate. When the blood is al-
lowed to flow into the bottle it will displace an equal quantity of this
solution, which can be measured in a graduated cyhnder.

Measure the blood flow for a short time, then stimulate the chorda
tympani nerve until you have obtained a decided increase in the blood
flow. Allow this flow to become normal again. Stimulate the sympa-
thetic nerve until the blood flow has been considerably lessened. These
results are referable to the fact that the chorda possesses vasodilator
qualities, whereas the sympathetic is a vasoconstrictor nerve.

6. Secretion by the Bloodless Gland. — Render the submaxillary
gland bloodless by ligating the blood-vessels supplying the head, or by
decapitating the animal. Stimulate the chorda tympani, and measure

DIGESTION 211

the quantity of saliva secreted. How long after the cessation of the
blood flow may saliva be obtained? What conclusion seems justified
regarding the secretory activity of the cells of this gland?

7. Dissection of the Salivary Glands. — Isolate the sublingual and
parotid glands and their excretory ducts.

Examine preparations of resting and active tissue from the parotid
or submaxillary gland under the microscope.

LESSON XLV
DIGESTION (Continued)

SECRETION OF PANCREATIC JUICE. ACTION OF SECRETIN. GASTRO-
ENTEROSTOMY

1. Preparation of Secretin. — Anesthetize a mammal and maintain
the anesthesia throughout the following experiments: Perform trache-
otomy. Open the abdomen by an incision through the hnea alba.
Identify the pyloric sphincter. Beginning at this point isolate a
segment of intestine about 1 m. in length. Remove it; sUt its wall,
and wash it thoroughly in running water. Kill the animal by an
overdose of ether. Scrape off the mucous lining of the segment of in-
testine just removed with a piece of glass, and immerse this material
in saline solution and sand. Add to it three or four times its volume of
0.4 per cent. HCl and place it in the ice-chest. Shortly before being

Fig. 121. — Diagram to Show the Position of the Ducts of the Pancreas.
D, Duodenum; P, pancreas; />C, ductus choledochus; DW, ductus Wirsungianus; DS,

ductus Santorini.

used add KOH to this decoction of the duodenal mucosa until changed
to an alkaline reaction. Strain through muslin and filter. As much
as 50 c.c. of this preparation should be used at a time. Since the acidi-
fied decoction may be kept for some time, it is advisable for economic
reasons to prepare it from some of the animals used during one of the
exercises immediately preceding. If an animal has been used especially
for obtaining secretin, it should be kept until the end of this exercise
for purposes of dissection.

2. Collection of Pancreatic Juice. — Anesthetize a mammal and main-
tain the anesthesia throughout the following experiments: Perform
tracheotomy. Open the abdominal cavity by an incision in the linea

213

214 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

alba. Identify the pyloric sphincter and duodenum. Note the posi-
tion, shape, color, etc., of the pancreas. Inspect the body of this organ.
Note how closely it invests the duodenum. Identify the duct of Wir-
sung. Open the duodenum in this region and locate the papilla through
which the pancreatic and common bile-ducts discharge their contents.
Insert a straight glass cannula in this orifice, and place a chp upon the
common duct farther distally.

Adjust the mouth of the cannula so that the drops of pancreatic
secretion may fall upon the spoon of a receiving tambour. By means
of narrow rubber tubing connect this tambour with a recording drum
registering the number of drops upon the paper of a slowly revolving
kymograph. Add a time-curve.

3. Action of Secretin. — Expose the right external jugular vein and
insert a cannula in its central end (see Lesson X). Slowly inject 50 c.c.
of the activated preparation of duodenal mucosa. Register the drops
of pancreatic juice in the manner just described. Compare the results.
Disconnect the apparatus.

4. Gastro-enterostomy. — Procure curved needles, catgut, and oper-
ating instruments. Select a segment from the upper portion of the
jejunum. Bring its flat surface against the region of the greater curva-
ture of the stomach, avoiding the blood-vessels of this region. Approxi-
mate these surfaces, being careful to give a normal curvature to the
duodenum. Make an incision about 6 cm. in length in the anterior
wall of the stomach at a safe distance from the blood-vessels passing
along the greater curvature. Make a similar incision in the convex
side of the loop of the jejunum. Suture the two orifices in apposition,
first by an external serous suture carried along one side of the orifice
and then by an internal rqw of sutures embracing the mucosa. Repeat
on the other side in the reverse direction. What is the purpose of this
operation? Discuss physiologic points for and against this operation.
Under what circumstances may it produce beneficial results? Kill the
animal by an overdose of ether.

LESSON XLVI

DIGESTION (Concluded)

LACTEALS AND THORACIC DUCT. PERISTALSIS. SECRETION OF BILE

1. Lacteals. — Anesthetize a cat which has been fed with fatty food
several hours beforehand, and maintain the anesthesia throughout the
following experiments: Perform tracheotomy. Open the abdomen by
a longitudinal cut in the median line, and thus expose the viscera.
Throughout the subsequent experiments keep the viscera warm by
applying cloths moistened with warm physiologic salt solution. Ex-
amine the walls of the intestine and the mesentery. Identify the lac-
teals filled with chyle, and note their beaded appearance. These con-
strictions indicate the positions of the lymphatic valves. Trace the
lacteals to the receptaculum chyh, the enlarged abdominal end of the
thoracic duct, which lies opposite the kidneys.

2. Peristalsis. — In the cat, spontaneous peristaltic movements of
the small intestine are seldom in evidence. Give reasons for this
motor quiescence. Stimulate the intestine mechanically and elec-
trically and watch the resulting contractions.

Is the stomach contracting? Stimulate its surface at the fundus
and at the pylorus. Compare the results.

Expose the right vagus nerve; cut it, and stimulate its distal stump.
Observe the movements of the stomach and intestine. What is their
character?

3. Chyle. — Slit open a distal lacteal. With a pipet transfer a few
drops of chyle to a watch-glass and observe the coagulation. Place a
drop on a glass slide and examine it microscopically, identifying white
corpuscles and fat globules. Close the opening in the lacteal by means
of an artery clamp.

Expose the region of the hepatic artery and trace the numerous
lymphatics to the hilum of the liver. What is their appearance? What
is the character of their contents?

4. Secretion of Bile. — Ligate the common bile-duct just above its
entrance into the duodenum, and insert a cannula in its hepatic end.
Empty the gall-bladder by gently squeezing it between your fingers and
occlude the cystic duct by means of an artery clamp. Connect the
cannula with a graduated cyUnder. Read off the quantity of bile so
far collected. Note the effect upon its level of the respiratory move-
ments. Ascertain by reading the amount of bile that is secreted in a
given period of time. After fifteen minutes place the graduated cyl-
inder in a vertical position, and determine the pressure under which the
bile is being secreted. What is the relationship between the secretory

215

216 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

pressure and the blood-pressure in the portal vein? Obviously, the bile-
pressure is determined in this case in mm. H2O. Divide by 13.5 in
order to obtain the corresponding value in mm. Hg. Since the portal
pressure in cats amounts to about 7 mm. Hg while the secretory press-
ure frequently rises to 15 mm. Hg, it may be concluded that the hepatic
cells are capable of secreting even against a pressure higher than that
under which they obtain their material.

5. Experimental Jaundice. — Inject into the bile-duct a saturated
solution of indigo-carmin, noting by a watch the time when the injec-
tion has been begun. Clamp the common duct. Watch for the blue
color to appear in the skin, the mucous membrane of the mouth, the
conjunctiva, and the chyle in the lacteals. Squeeze the urinary bladder
at intervals and expel a small quantity of urine. How soon after the
beginning of the injection does the urine assume a blue color?

6. Thoracic Duct. — Arrange for artificial respiration. Open the
chest and expose the thoracic duct on the left side of the spinal column.
It is now rendered clearly visible by the blue chyle.

7. The Stomach Contents. — Palpate the stomach. Has the food
been fully reduced mechanically? Evacuate its contents. Wash the
gastric mucosa and note its soft velvety texture. Examine preparations
of gastric glands under the low and high powers of a microscope. Iden-
tify the chief and parietal cells.

LESSON XLVII

ABSORPTION

OSMOSIS. INTESTINAL PERISTALSIS, SECRETION OF INTESTINAL
JUICE. ABSORPTION FROM THE SMALL INTESTINE

1. Osmosis. — Prepare an osmometer by tying a piece of fish condom
or other semipermeable membrane over the orifice of a thistle tube.
Fill the chamber of this tube with a concentrated solution of mag-
nesium sulphate. Fill a beaker with distilled water and suspend the
filled thistle tube in the water so that the levels of the fluids agree.
Attach a narrow glass tube, about 1 m. in length, to the end of the
thistle tube, and allow the apparatus to stand for twenty-four hours.

■:

lilll

=ii

. , —

- -. ,'

-

--■ f-.:.

-_.

__—

— ^_

^H

r™ :

H— ^^

,0

Fig. 122. — A Simple Osmometer.
The receptacle contains water, and the cell a solution of magnesium sulphate. As
the molecules of water are drawn through the semipermeable membrane the level of the
MgS04 solution rises.

Already in the course of an hour or two it will be observed that the level
of the solution of magnesium sulphate has risen a considerable distance.
The solution of magnesium sulphate possesses a greater osmotic press-
ure and draws molecules of water through the membrane.

2. The Osmotic Power of the Intestine. — Anesthetize a cat and
maintain the anesthesia until the animal has been killed by an overdose
of ether. Perform tracheotomy. Open the abdominal cavity by a
small longitudinal incision in the hnea alba. Pull a loop of small in-

217

218 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

testine about 20 cm. in length through this opening. The jejunum is
usually empty. If not, gently squeeze its contents along into the
lower bowel. Tie a ligature tightly about the middle of the exposed
segment, and a second and third about 8 cm. distally and centrally to
this one. In this way two segments of intestine have been isolated.
Into one of these inject 5 c.c. of a saturated solution of magnesium sul-
phate, and into the other 30 c.c. of a 0.7 per cent, solution of sodium
chlorid. Note that the former segment feels perfectly empty, whereas
the latter is highly distended. Replace the entire loop in the abdominal
cavity, marking its upper end with a colored piece of cord. Close the
opening in the abdominal wall with a clamp. Cover the animal with
a warm cloth and allow it to rest under anesthesia for thirty minutes.
At the end of this period expose the aforesaid segments and determine
their degree of distention. It will now be found that the loop contain-
ing the Mg SO4 is highly distended, whereas the loop with the NaCl is
practically empty. Obviously, the Mg SO4, possessing a greater osmotic
pressure ■ than the body fluids, has abstracted water from the latter.
Contrariwise, the 0.7 per cent, solution of NaCl has been removed from
the loop. Using these facts as a basis, explain the action of the saline
cathartics.

3. Chemical Stimulation of the Secretion of Intestinal Juice. —
Insert a cannula in the external jugular vein, and empty a loop of
duodenum about 30 cm. in length. Inject intravenously from 1 to
3 c.c. of M/8 solution of barium chlorid or sodium citrate. Observe
the peristalsis which results almost immediately and measure the
quantity of intestinal juice obtainable from this segment. Kill the
animal by an excessive amount of ether.

4. Gastric Fistula. — Procure curved needier., a needle-holder, and
clamps. Bring the wall of the pylorus in the wound and anchor it by
means of a continuous suture. Decrease the length of the wound by
sutures. Incise the gastric wall and suture it to the edges of the wound.
Insert a gastric cannula and secure it by additional sutures.

5. Peristalsis. — Anesthetize a rabbit and maintain the anesthesia
during the following experiments and until the animal has been killed
by an overdose of ether. Perform tracheotomy. Open the abdominal
cavity by a median incision through the linea alba. Observe the
peristalsis. The intestine of the rabbit invariably shows most intense
peristaltic movements when exposed to the cooler air or stimulated
mechanically. Note the pendular movements and also the regular
peristalsis.

Compare the length and general appearance of the intestines of the
rabbit with those of the intestines of the cat and dog, noting especially
the predominance of the large intestine in the former animal. Discuss
the functional significance of this difference.

6. The Influence of Salts on Peristalsis. — Apply a few drops of
M/320 solution of barium chlorid or sodium citrate to the peritoneal
surface of a loop of intestine. Observe the marked peristalsis which

ABSORPTION 219

follows. Inhibit this movement by applying a solution of calcium
chlorid or magnesium chlorid.

7. Secretion of Intestinal Juice into Excised Loops. — Empty a loop
of small intestine about 10 cm. in length by gentle pressure exerted with
your fingers. Place two pairs of ligatures around the intestine so as to
isolate this segment. Ligate the corresponding blood-vessels. Re-
move this segment from the body by cutting between each pair of
ligatures. Kill the animal by an overdose of ether. Suspend the ex-
cised loop at 38° C. in a measured quantity of M/8 sodium chlorid to
which from one-seventieth to one-fiftieth of its volume of M/8 barium
chlorid has been 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, about 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 chew-
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 Lieberkiihn.

LESSON XLVIII

EXCRETION
SECRETION OF URINE

1. The Drop Method of Registering the Flow of Urine.— Anesthetize
a mammal and continue the anesthesia throughout the following experi-
ments : Perform tracheotomy. Expose the left common carotid artery
and insert in it a straight glass cannula. 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 away from its posterior
surface. Insert a straight cannula in each (toward the kidney) and
connect them by means of short pieces of rubber 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 adrenalin sufficiently to cause a moder-
ate rise in blood-pressure (2 c.c. of the solution to 20 c.c. of saline).
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 easily 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. — Anesthetize a cat and maintain the anesthesia
until the animal has been killed by an overdose of ether. Expose the
sciatic nerve, apply a ligature, and cut centrally to the hgature. Stimu-
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 temperature 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 paralyzes 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 overdose of ether.

2. Sweating in Man. — Procure a piece of paper sensitized with
silver nitrate. Cleanse the palm of the hand and after a certain interval
apply 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 secretory nerves, this test will now remain negative.

3. Body Temperature. — Determine the body temperature of the
subject by means of an ordinary 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 thermometer be left in 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?

LESSON L

EXCRETION (Concluded)

THE INNERVATION OF THE BLADDER. PILOMOTOR REACTIONS

1. The Function of the Hypogastric Nerves.— Anesthetize a cat and
maintain the anesthesia throughout the following experiments: Per-
form tracheotomy. Open the abdominal cavity by a median incision
in the linea alba. Identify the urinary bladder, and raise its fundus
sufficiently to expose the fatty tissue investing its cervical portion.
By careful dissection isolate the 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 Effects. — Unite the margins of the wound in the
abdomen by 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 laminae of several vertebrae 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. Stimulate 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 determination of the strength of the make and break

induction shocks by means of the galvanometer. Pro-
jection method.
(6) The production of acid in contracting muscle. Acid fuchsin
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 mei>

cury pump. Barcroft-Haldane blood-gas apparatus.
(6) Viscosimeter (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.
(b) 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 mammalian heart.

16. The application of the polygraph (Mackenzie).

17. Projection of the larynx. Stimulation of the superior and in-
ferior laryngeal nerves.

18. AboHshed and exaggerated reflexes in man in consequence of
^'high" and ''low" lesions of the nervous system.

19. (a) The decerebrated pigeon.
(W The decerebrated cat.

227

228 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

20. (a) Lesions of the cerebellum in pigeons.
(6) Cerebellar defects in man. Nystagmus.

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 metric system the Uter is a unit of capacity equivalent to the volume
occupied by the mass of 1 kilogram of pure water at its maximum density. It is
equivalent in volume to 1.000027 cubic decimeter. Under this definition a milli-
hter (0.001 of a liter) is different from a cubic centimeter by a very minute frac-
tion. However, as "cubic centimeter" is the term used throughout medical literature
we shall use it in this book, though both the U. S. and British Pharmacopceias have
adopted the term "milliliter" (mil.) in its place. /

A. METRIC

Weight:

1 milligram (mg.)

10 milligrams = 1 centigram (eg.).
10 centigrams = 1 decigram (dg.).
10 decigrams = 1 gram (gm.).

Written.

0.001
0.01
0.1
1.0

1000 grams = 1 kilogram (kilo.) 1000.0

Volume:

1 milliliter (mil.) 1.0

1 cubic centimeter (c.c.) 1.0

(1 c.c. of water weighs 1 gm.)

1000 cubic centimeters = 1 liter (L.) 1000.0

Length:

1 millimeter (mm.)

10 miUimeters = 1 centimeter (cm.)

10 centimeters = 1 decimeter (dm.)

10 decimeters = 1 meter (M.)

Approximate
equivalent.

^\ grain
5 grain
1^ grains
15 grains
2 J pounds

15 minims
15 minims

34 fiuidounces

^ inch
f inch
4 inches

40 inches

B, APOTHECARIES

Approximate
equivalent.

Weight (Troy):

1 grain (gr.) 0.065 gm

10 grains 0.7 gm

20 grains = 1 scruple (3) 1.3 gm

3 scruples = 1 dram (5) 4.0 gm

8 drams = 1 ounce (§) 30.0 gm

12 ounces = 1 pound (lb) 372.0 gm

Volume:

1 minim (ttr) 0.06 c.c.

60 minims = 1 dram (5) 4.0 c.c.

8 drams = 1 ounce (5) 30.0 c.c.

16 ounces = 1 pint (O) 475.0 c.c.

2 pints = 1 quart (Oij) 950.0 c.c.

8 pints = 1 gallon (Cong.).

(1 gill = 4 fluidounces.)

Length:

1 inch (in.) 2.5 cm.

♦From Bastedo's "Materia Medica, Pharmacology, Therapeutics, and Pre-
scription Writing."

230 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY

■KT , ,1. m Approximate

Noteworthy Terms: equivalent.

1 ounce avoirdup)ois 437.5 grains

1 ounce troy 480.0 grains

1 fluidounce of water (the standard of volume) 455.7 grains

1 pound avoirdupois is 7000.0 grains

1 pound troy is 5760.0 grains

1 minim of water weighs -^ grains = 0.95 grain = 61.61 mg.

15 grains of water = 16 minims; 1 grain of water measures

1.05 minims = 0.0648 c.c.
An imperial pint is 20 ounces; a United States pint is 16 ounces.

EXACT EQUIVALENTS OF METRIC AND APOTHECARIES' WEIGHTS
AND MEASURES ACCORDING TO THE U. S. PHARMACOPCEIA

_. , Approximate

Volume: equivalent.

1 C.C 16.23 minims

1 liter (1000 c.c.) 33.8 oz.

1 minim (ttk) 0.061 c.c.

1 fluidram (3) 3.696 c.c.

1 fluidounce (5) 29.57 c.c.

1 pint (O) 473.18 c.c.

Weight:

1 milligram, 0.001 (mg.) 0.0154 grain

1 centigram, 0.01 (eg.) 0.1543 grain

1 decigram, 0.1 (dg.) 1.543 grains

1 gram, 1.0 (gm.) 15.4324 grains

30 grams, 30.0 462.9 grains

31 grams 478.4 grains

1 grain (gr.) 0.065 gm.

10 grains 0.648 gm.

15 grains 0.972 gm.

1 scruple O) 1.296 gm.

1 dram (5) • 3.89 gm.

1 ounce troy (5) 31.1 gm.

1 ounce avoirdupois 28.35 gm.

INDEX

Abdominal aorta, compression of, 107
Abduction of vocal cords, 143
Aberration, achromatic, 189

spheric, 190
Absorption, 217

and elimination, rapidity of, 219
Acceleration of heart, 88
Accommodation reflex, 184
Achromatic aberration, 189
Action current of frog's heart, 60
of muscle, 59
of nerve, 60

of cocain, 167

of glucose, 221

of secretin, 214

of sodium chlorid, 221
Acuity of dynamic sense, 180

of temperature sense, 170
Adaptation to touch sensations, 168
Adduction of vocal cords, 143
Adrenal extract, influence of, on intc >

tine, 219
Adrenalin, effect of, on blood-pressure,

110
Afferent impulses, summation of, 157
After-images, negative, 201

of temperature, 169

positive, 200
Air, entrance of, into circulation, 115
All-or-none law, 82
Ameboid motion, 21

Ametropic artificial eye, ophthalmoscopic
examination of, by direct method,
195

eye, 188, 189
Amyl nitrite, effect of, on blood-pres-
sure, 110
Anelectrotonus, 63
Anodic excitation of nerve, 64
Aorta, abdominal, compression of, 107
Aortic insufficiency, schema of, 102

stenosis, schema of, 102
Apex-beat of heart, 95
Apothecaries' weight, 229
exact equivalent, 230
Aristotle's experiment, 167
Arterial blood, 68

blood-pressure, direct method of de-
termining, 103

pulse, character and velocity, 129
heart action and relation between, 129

Artificial eye, ametropic, ophthalmo-
scopic examination of, by direct
method, 195
emmetropic, ophthalmoscopic ex-
amination of, by direct method,
194
opthalmoscopic examination of, by
indirect method, 196
respiration, 140
Asphyctic blood, 68
Asphyxia, 135

Associated movements of eyes, 200
Astigmatism, 189
detection of, 194
measurement of, 194
Atmospheric pressure, decreased, effect on

lungs, 148
A tropin, action on heart, 87
Auditory fatigue, 174
Auscultation, 139

Axes, visual, convergence of, influence of,
203

Babinski phenomenon, eliciting, 160
Bile, secretion of, 215
Binocular fusion of dissimilar images, 203
vision, relation of, to judgments of
direction, 203
of distance, 203
of solidity, 203
Bladder, innervation of, 225
Bhnd spot, 199

contours of, 199
Blood, arterial, 68
asphyctic, 68

cells, red, human, counting of, 73
chemical tests for, 78
coagulation of, 69
corpuscles, red, enumeration, 70
simultaneous count, 73
relative amounts, 70
white, enumeration of, 71
simultaneous count, 73
crystals, 78
experiments on, preparation of animal

for, 67
flow through lungs, effect of variations
in intrathoracic pressure on, 147
velocity of, differences in, schema
illustrating, 103

231

232

INDEX

Blood, medicolegal tests for, 77
microscopic examination, 73
plasma, relative amounts, 70
specific gravity, 75
spectroscopic examination of, 77
suspected, examination, 78
venous, 68
Bloodless gland, secretion by, 210
Blood-pressure, arterial, direct method of
determining, 103
carotid, record of, 113
effect of adrenalin on, 110
of amy] nitrite on, 110
of changes in, 222
of division of both vagi nerves on, 114

of one vagus nerve on, 114
of exercise on, 128
of hemorrhage and saUne injection

on, 111
of posture on, 127

of stimulation of intact vagi nerves
on, 113
estimation by indirect method, 125
influence of dyspnea on, 109
of hemorrhage on, 108
of posture on, 107
intracardiac, 115
venous, 128
Blood-supply, influence of, on muscle

contraction, 52
Blood-vessels, retinal, 199
Body temperature, 223
Bones, manner of attachment of muscles
to, 39

Capillary circulation, 99

in frog's lung, 147
Carbon dioxid, elimination of, in res-
piration, 151
influence of, in respiration, 140
Cardiac plethysmograph, 92
Cardiogram, 96
Cardiograph, 96
Cardiometer, 92

Carotid blood-pressure, record of, 113
Catelectrotonus, 63
Cathodic excitation of nerve, 64
Cell, Daniell, 25

dry, construction and action, 25
Cerebral localization, 163
Cerebrum, influence of, 162

removal of, effect, 161

stimulation of, 163
Cervical sympathetic nerve, vasomotor

action, 117
Chemical and electric stimulation of
temperature spots, 169

stimulation of muscle, 47

of secretion of intestinal juice, 218

tests for blood, 78
Chemicals, influence of, on muscle con-
traction, 48
Chloroform and ether, action of, on

heart, 90

Chorda tympani nerve, function of, 210
Chyle, 215
Ciliary motion, 21
Circles of dispersion, 188
Circuit, primary, 29

secondary, 30
Circulation, capillary, 99
in frog's lung, 147
constant-flow, 99
entrance of air into, 115
in frog's lung, 147
intermittent flow, 99
schema, normal, 101
remittent flow, 99
schema, 100
Coagulation of blood, 69
Cocain, action of, 167
Coil, induction, 29

Cold and hot spots, mechanical stimu-
lation of, 169
thermal stimulation of, 169
Cold-blooded animals, speed of nerve

impulse in, 55
Collapse of lung, 136
Collection of pancreatic juice, 213
Color-bhndness, 202
Colored objects, fields for, 191
Colors, complementary, 202
contrast, 202
fusion of, 201
Commutator, Pohl's, 56
Complementary colors, 202
Conductivity of nerve, 36
Constant current, 29
Contraction, muscle, compound, 43

effect of excessive stimulation on, 49
of veratrin on, 49
on volume, 38
fusion of, 42

height of, relation of amount of load
to, 44
of strength of stimulus to, 43
human, 51

influence of blood-supply on, 52
of chemicals on, 48
of temperature changes on, 47
method of registering, 33
paradoxic, 60
single, 41
summation of, 42
Contrast colors, 202
Convergence of visual axes, influence of,

203
Corpuscles, blood. See Blood corpuscles.
tactile, histologic examination of, 167
Crystals, blood, 78

hemin, 78
Currents, electric, types, 28
Cutaneous and muscular sensations, 167

Daniell cell, 25
Deglutition, 207

in human subject, 208

wave of, 207

INDEX

233

Drpicssor norvc, vasomotor action of, US
Ditiphragiii, action of, 135
Didficon spliv^^nio^iiapli, 121)
Digestion, 207, 209, 213, 215
Direct ami indirect vision, 200

method for oplithalnioscopic; examina-
tion of ametropic artihcial
eye, 195
of ennnetrojjic artificial eye, 1*.)4
Direction, judgments of, relation of

binocular vision to, 203
Discrimination of weight, Weber's law,

170
Dispersion, circles of, 188
Dissection of ear of dog-fish, 179

of ey(% 183

of region of kidney, 222

of salivary glands, 211
Distance, judgment of, relation of bin-
ocular vision to, 203
Double and single images, 203
Drop method of registering (low of urine,

221
Dry cell, construction and action, 25
Dynamic and static senses, 179

sens(>, acuity of, 180
Dynamometer, 52
DysiHiea, 135

influence of, on blootl-pressure, 109

Ear, diagrammatic representation of, 176

middle, models of, 175

of dog-fish, dissection of, 179
Elbow, sensation of motion at , 171
Electric and chemical stimulation of
temperature spots, 169

currents, types, 28

stimulation of nmscle, 23
Electrodes, non-polarizable, 29

stimulating, 27, 28
Electrotonus, 63

Elimination and absorption, rapidity of,
219

rapidity of, 222
Emmetropic artificial eye, ophthalmo-
scopic examination of, by direct
method, 194

eye, 187
Entoptic phenomena produced by tears,

192
Equilibrium a combined sense, 181
Ergograph, Mosso's, 51

spring, 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 , t ransmission of,

81
Excretion, 221, 223, 225

Exercise, effect of, on blood-pressure, 128

Experimental jaundice, 216

Ext(Misil)ility of muscle, 36

Ext rasy stole, Si

Eye, ain(>tropic, 188, 189

dissection of, 183

emmetropic, 187

artificial, ophthalmoscopic examina-
tion of, by direct method, 19-1

near and far points of, 193
Eyes, associated movenu'uts of, 2(K)

Fah and near points of eye, 193
Far-sightedne.ss, 1 88
Fatigu(», auditory, 174

muscle, 49
Fibrillation, 93
Field of vision, 1<K)
I'ields for colored objects, 191
Fish, respiratory 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 curnMit of, 60

otoUthic cavity in, 181

rheoscopic, 59

rotation effects in, 181
Function of roots of s|)inal cord, 163
Fusion, binocular, of dissimilar images,
203

of colors, 201

of gray and white, 201

of muscle contraction, 42

Galvanic current, 29

Galvani's experiment, 59

Gastric fistula, 218

Gastrocnemius, frog's, ergographic record

of, 52
Gastro-enterostomy, 214
Glossopharyngeal nerves, 141
Glucose, action of, 221
Gower's hemoglobinometer, 75
Gravity, center of, 39
Gray and white, fusion, 201

Hearing, 173

compound 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, IM)
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, 60

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 stimuH, 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 impulse in, 56

vasomotor phenomena in, 123
Manometer, membrane, 115
Marey's pneumograph, 129

tambour, 91
Mechanical stimulation of hot and cold

spots, 169

INDEX

235

Mechanical stimulation of muscle, 23

of retina, 190
Medicolegal tests for blood, 77
Membrana tympani in man, observa-
tion of, 175
Membrane manometer, 115
Mercury key, 20
M(>tric weight, 229

exact equivalent, 230
Microscopic examination of blood, 73
Mitral insufficiency, schema, 102

stenosis, schema of, 102
Morse key, 26
Mosso's ergograph, 51
Motion, ameboid, 21
ciliary, 21

sensation of, at elbow, 171
Motor nerve, irritability near center, 59

points, stimulation of, 61
Movement, touch sensations modified by,
169
simultaneous, 170
Miiller-Lyer figures, 205
Muscarin, action on heart, 87
Muscle, 21

action current, 59
contraction, compound, 43

effect 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
paradoxic, 60
single, 41
summation, 42
cross-section, relation of force to, 38
extensibility of, 36
fatigue, 49

human, law of unipolar stimulation, 65
independent irritability, 35
long and compact, comparison be-
tween, 37
manner of attachment to bones, 39
movement, 22
power, 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, 167
Myograms, isometric, 34

isotonic, 34
Myography, 25, 32

records of, fixation, 34
Myopia, 188

Near and far points of eye, 193

point, 188
Near-sightedness, 188
Negative after-images, 201
Nerve, 21

action current of, 60
anodic excitation, 64
cathodic excitation, 64
chorda tympani, function of, 210
conductivity of, 36
currents, 61
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, 36

motor, irritability near center, 59
phrenic, 137

secretory, isolation of, 209
stimulation of, 31
direct, 32
indirect, 32
superior laryngeal, 142
supply of submaxillary 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, 163, 165

frog's dissection of, 155
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 tympani in man, 175
Olfactory cells, distribution of, 174
structure of, 174
fatigue, 174
latency, 174

qualitative changes before exhaustion,
174

236

INDEX

Ophthalmometer, 193
Ophthahiioscopo, Loring's, 195
Oj)hthahnoscopic examination of ametro-
pic artificial eye by direct method,
195
of artificial eye by indirect method,

196
of emmetropic 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, 60

resistance, 171
Patellar reflex time, 166
Percussipn, 139

of human stomach, 208
Perimeter, 191
Peristalsis, 215, 218

influence of salts on, 21.S
Phenomenon, Babinski, eliciting of, 1(>()

Purkinje's, 202
Phlebograj^h, 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-pressin*(\ 1 27

influence of, on blood-pressure, 107
Preparation of secretin, 213
Pressure and touch, peculiar ])hen()m(Mia
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 illustrating,
103

schema of, 102

venous, character and velocity, 129
Pupil, size of, changes in, 184
Purkinje's phenomenon, 202

Quality of color and intensity of light,

202
Quickly interrupted current, 29

Railroad nystagmus, 181
Rapidity of absorption and elimination,
219

of elimination, 222
Reaction time, 165
with choice, 166

to hght, 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, locaUzation of, 156

light, 184

time, 157
patellar, 166

winking time, 166
Reflexes, action, 159
• exaggeration of, by means of strvchnin,
159

in man, 159

inhibition of, by higher centers, 159
ui)()n ccMitral patlis, 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, lol

forced, 135

frequency, 139

glossopharyngeal nerve in, 141

inferior laryngeal nerve in, 143

influence of carbon dioxid in, 140

larynx in, 141

main tnmk 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
Retina, formation of image upon, 184

mechanical stimulation of, 190
Retinal blood-vessels, 199

image, formation of, 186

INDEX

237

Itheoscopic frog, 59
Riva-Rocci's sphygmomanometer, 12.")
Roots of spinal cord, function of, 163
Rotation effects in frog, 181

in mammals, 180
Rotatory apparatus for color disks, 2)1

Saline injection and hemorrhage, effect

of, on blood-pressure, 111
Saliva, secretion of, 209
Salivary glands, dissection of, 211
Salts, influence of, on peristalsis, 218
Scheiner's experiment, 186
Sciatic nerve, vasomotor action of, 118,

119
Secondary current, 29
Secretin, action of, 214

preparation of, 213
Secretion by bloodless gland, 210

normal, of urine, 221

of bile, 215

of intestinal juice into excised loops, 219

of saliva, 209

of sweat, 223
Secretory nerves, isolation of, 209

pressure, 210
Semicircular canals, action of, model
illustrating, 180
position of, 179
Sensation of motion at elbow, 171
Sense organs, 167, 173
Shadow test, 196
Shape of lens, changes in, 184
Simultaneous movements, 170
Single and double images, 203
Size of pu])!!, changes in, 184
Skiascopy, 19()
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, 1()()

threshold value of, 174
Specific gravity of blood, 75
Spectroscopic (examination of ))lood, 77
Spheric aberration, 1<M)
Sphygmograph, application of, 129

Didgeon, 129
Sphygmomanometer, application of, 125
Sphygmotonometer, 125
Spinal cord, roots of, function of, 163
Spirometer, 133
Splanchnic nerve, greater, vasomotor

action of, 121
Spot, blind, 199

contours of, 199

pain, 170

yellow, 199
Spring ergograph, 52
Staircase phenomenon, 89
Stannius' experiment, 89
Static and dynamic senses, 179

Stenosis, aortic, schema of, 102

mitral, schema of, 102
Stethograph, Marey's, 130, 131
Stethography, 139
Stimulating electrodes, 27, 28
Stimulation, excessive, effect on iiuisclc
contraction, 49
of cerebrum, 163
of muscle, 31
direct, 32
indirect, 32
of nerve, 31
direct, 32
indirect, 32
threshold of, 160
Stimulus, inadequate, 173

muscle, relation of strength of,
to height of contraction, 43
subminimal, summation of, 44
thermal, effect of, 157
Stouiach contents, 216

human, percussion of, 208
Streaming, protoi)lasmic, 21
Stry(!hnin, exaggeration of reflexes by

means of, 159
S\ibmaxillary gland, nerve supply of,
schema illustrating, 209
vtxsomotor changes in, produced by
stimulation of chorda tympaiii and
sympathetic; nerve, 210
Sweat nerves, 223
secretion of, 223
Sweating in man, 223
Swim test, 137

Symjjathetic nerve, cervical, v.isomotor
action, 117
function of, 210

Tactile corpuscles, histologic; examina-
tion of, 167
Tambour, Marey's, 91
Taste, 173

distribution of, 173

(electric stimulation, 173

elimination of sweet and bitter, 174

inadequate stimuli, 173

reaction to single papilla, 173

threshold value of, 173
Taste-buds, structure of, 173
Tears, entoptic phenomena produced by,

192
Temperature, after-image of, 169

body, 223

changes, influence on muscle contrac-
tion, 47

contrast, 170

effect of, on heart-beat, 80

influence of, on nerve, 59

sense, acuity of, 170

spots, chemical and electric stimula-
tion of, 169
Tendon reflexes in man, KM)
Test, swim, 137

types, Snellen's, 194

238

INDEX

Tetanic current, 29

Tetanus, incomplete, of heart, 89

muscle, 43
Thermal illusions, 170

stimulation of hot and cold spots, 1G9
of muscle, 23

stimuli, effect of, 157
Thoma-Zeiss hemocytometer, 71
Thoracic duct, 216
Thorax in respiration, action of, 134
Tones, compound, 175

location of, 174
Tonus, muscle, 160

Touch and pressure, peculiar phenomena
and illusions of, 168

discrimination, 167

localization, 167

projection of sensation of, 169

reaction to, 165

sensations, adaptation to, 168
modified by movement, 169
reaction to, 165
Traube-Hering curves, 106
Trigeminal nerves, 141
Twitch, muscle, 41
Tympanum, pressure in, 175
Types, test, Snellen's, 194

Unipolar stimulation of human muscle

and nerve, law of, 65
Urine, flow of, drop method of registering,
221

normal secretion of, 221

Vagi nerves, both, division of, effect of ,
on blood-pressure, 114
influence of, 207

intact, stimulation of, effect on blood-
pressure, 113
Vagus nerve, one, division of, effect on
blood-pressure, 114
main trunk, 143
Valves, venous, position and function, 109
Vasomotor action of cervical sympathetic
nerve, 117
of depressor nerve, 118
of greater splanchnic nerve, 121
of sciatic nerve, 118, 119

Vasomotor changes in submaxillary gland
produced by stimulation of chorda
tympani and sympathetic nerve, 210
phenomena in man, 123
supply of kidney, 123
Venous blood, 68
blood-pressure, 128
pulse, character and velocity, 129
valves, position and function, 109
Ventricle of heart, conduction of heart-
beat through, 83
isolated strips, 82
Veratrin, effect on muscle contraction, 49
Vision, 183, 189, 193, 199

binocular, relation of, to judgments of
direction, 203
of distance, 203
of solidity, 203
field of, 190
Visual angle, 194

axes, convergence of, influence of, 203
Vocal cords, abduction of, 143
and adduction of, 143

Wabbling of lens, 186
Warmer, muscle, 47

Water, ehmination 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 gra^ ,. 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 Unes, 204

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