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QP44 .L83 Directions for labor

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COLLEGE OF PHYSICIANS
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DIRECTIONS

FOR

Laboratory Work in Physiology

FOR THE USE OF

MEDICAL STUDENTS

WARRKN P. LOMBARD, A.B., M.D.

PROFESSOR OF PHYSIOLOGY, UNIVERSITY OF MICHIGAN

GEORGE WAHR, Publisher

ANN ARBOR

Copyright, 1906

BY
GEORGE WAHR

J If Uxii^'O*^

G^ 1=4-4-

The Ann Arbor Press, Printers

PREFACE.

The course which is here outHned, is the result of four-
teen years of laboratory work with medical students. It con-
tains only such experiments as can be actually performed
by the student himself in the eight weeks allotted to the work
of experimenting, and like every such course necessarily
omits manv experiments which would be interesting and
instructive. It is supplemented by demonstrations by the
instructors and by such students as show special aptitude
for and have the time to devote to such work.

The experiments are arranged so as first to teach the
student the use of the graphic method, time recording in-
struments, and the electrical apparatus employed for exci-
tation. At the same time he becomes acquainted with the
general physiology of striated, non-striated, and heart mus-
cle and of the nerves of the frog. He then studies the reac-
tion of his own muscles and nerves to various forms of
electrical excitation. A little more than one half of the
course is thus spent, and at the end of this time the student
is prepared to take up the study of the subjects, so impor-
tant to every medical man, cen ral nervous processes, the
circulation and respiration. Only two experiments are made
on the mammal, but in these the circulation, respiration and
peristalsis are studied. Five of the eleven experiments on
ihe circulation are made on the human subject. It is be-^
lieved that the medical student should as far as possible study
the Physiology of man. and it is hoped that other exper-
iments of this character will be developed in the near future
and be substituted for those now made on animals. It is
needless to say that the frogs are rapidly killed before being
used, and that the mammals employed are thoroughly an-
aesthetized by the student, under the direction of an in
s true 'or.

xA-s most of the, students taking the course have no
knowledge of physiological methods, the directions for the
work have been made as explicit as possible with the object

IV " PREFACE

of saving time. Nevertheless, the harm which comes from
machine-Hke work is fully recognized, and students are en-
couraged to cultivate independence, and permitted to per-
form the experiments in other ways than those called for
in the notes. They are made to feel that the capacity to
observe and correctly interpret the results of an experi-
ment, is of even more importance than the ability to make
an experiment successfully, and that one who has trained
his powers of observation and has learned to accurately
report the phenomena he has witnessed, can make a relia-
ble diagnosis and keep a trustworthy case-book. As the
students at this University take a special course in Physio-
logical Chemistry, the work of this laboratory deals only
with the physical problems met in the body. For similar
reasons but little attention is given to the special senses.

It gives me great pleasure to acknowledge the valuable
aid of my past and present Assistants, Prof. Sidney P.
Budgett, Dr. Augustus E. Guenther, Dr. G. G. Crozier,
Prof. Wilbur P. Bowen, Dr. Carl J. Wiggers, Mr. Fred M.
Abbott, and Mr. Neal N. Wood, in developing the methods
employed in this course.

Warren Pi^impton Lomdard.
Physiological Laboratory,

University of Michigan,
August 1st, 1906.

CONTENTS.

General directions. Instruments, etc.. to be purchased
by students. List of apparatus to be supplied by
the laboratory. ^ xv

Experiment I.

Extensibility and Elasticity of a steel spring. . . i

Mounting of curves.
The student's notes.

Experiment II.

Extensibility and Elasticity of frog's muscle. . . 7

a. Experiment.

b. Plotting of curves.

Experiment III.

Response of muscle to making and breaking induction
shocks of various strengths, and use of the short-
circuiting key. 13

(Some facts regarding the- induction apparatus.)

a. Response to making and breaking shocks of in-
creasing strength.

b. Use of the short-circuiting key.

Experiment IV.

Relation of amount of load to height of lift and quan-
tity of work done. 21

a. Experiment.

b. Plotting of curves.

Experiment V.

Time relations of myogram 25

a. Influence of rate of drum on form of myogram.

VI - CONTENTS

b. Time relations of myogram.

c. Measurement of records and computation of
time intervals.

Experiment VI.

Genesis of tetanus. . . . . . . . -3^

a. Summation of two contractions.

b. Incomplete tetanus and complete tetanus.

c. Complete tetanus obtained with automatic in-
terrupter.

(Electrical connections in primary circuit of induc-
tion apparatus.)

d. Fatigue caused by tetanus.

Experiment \'II.

Independent irritability of muscle. . . . . -37
(Method of pithing frog, and of injecting curara.)

Experiment VIII.

Isolated conduction in muscle. . . . . • 43

(Method of unipolar excitation.)

Experiment IX.

Contractions of non-striated muscle. 47

a. Time relations of the myogram.

b. Rate required to tetanize.

c. Spontaneous contractions.

Experiment X.

The frog's heart ; its structure ; the relative time of ac-
tion of the different parts 51

a. (jross anatomy of frog's heart.

b. Origin and course of the wave of contraction.

1. Inspection.

2. The myocardiogram.

CONTENTS ': vii

Experiment XI.
Refractory period and compensatory pause. , . 57

Experiment XII.

Response of resting heart to stimulation by induction

shocks 61

a. Myogram of heart muscle.

b. Ijowditch's staircase.

c. All contractions maximal.

d. Effect of frequent stimuli.

Experiment XIII.

Location of a few motor points on the human arm. . 65
(The more efficient pole of an induction coil.)

Experiment XIV.

Response of human muscle to separate induction shocks

and to a tetanizing current. . . . -71

a. Making and breaking induction shocks of var-
ious strengths.

b. Tetanizing current.

Experiment XV.
Galvani's experiment. y"]

Experiment XVI.

Polarization of electrodes. 81

a. Polarizable electrodes.

b. Non-polarizable electrodes.
(Pfluger's Law.)

Experiment XVII.

Response of nerve to opening and closing of the direct
battery circuit, with currents of various
strengths. 8?

viii CONTJiNTS

Experiment XVIII.
vStimulation of human nerves by the direct current. . 9T

Experiment XIX.

Influence of the direct current on the irritability or hu-
man nerves. • • 97

Experiment XX. .

Currents of rest and action 103

a. Current of rest detected by a rheoscopic frog
preparation.

b. Current of action detected by a rheoscopic frog
preparation.

Experiment XXI.

The reflex frog 107

a. Time of recovery from shock.

b. Spread of reflexes.

c. Are reflexes purposeful?

d. Reflex time.

e. Spasm of muscles versus coordinated move-
ments.

Experiment XXII.
Reaction time for sound. 113

Experiment XXIII.

The knee-jerk as modified by reenforcing and inhibiting

influences. 117

a. Minimal blow necessary to excite.

b. Record of normal knee-jerk.

c. Motor reenforcements.

d. Reenforcement by sensory stimuli.

e. Psychic reenforcements.

CONTENTS IX

Experiment XXIV.

Conditions determining the blood pressure and the out-
put of the ventricle -125

Porter's artificial circulation apparatus.

a. Effect of changing peripheral resistance.

b. Effect of changing rate of heart beat.

c. Effect of changing the volume pumped per
beat.

d. Record of the pulse under different condi-
tions.

e. Comparison of arterial and ventricular pulse
curves.

f. Effect of lesions of heart valves.

Experiment XXV.

Circulation and respiration of the mammal. . . .133
(Schedule of work. List of apparatus. Directions
to student caring for apparatus. Directions to
Assistant. Anaesthesia. Directions to anaes-
thetizer. Operation for isolation of the carotid
and vagus.)

a. Measure of blood pressure in the carotid.

b. Maximal and minimal blood pressures.

c. Excitation of the peripheral end of the right
vagus.

d. Record of respiration with pneumograph.

e. Excitation of central end of vagus.

f. Excitation of peripheral end of left vagus.

g. Excitation of sciatic nerve.

h. Blood pressure during asphyxia,
i. Elasticity of lung tissue.

Experiment XXVI.

Circulation and respiration of the mammal contin-
ued. 149

a. Excitation of right depressor nerve.

b. Excitation of left depressor nerve.

c. Tracheotomy and artificial respiration.

X CONTENTS

d. Current of action of the heart.

e. Observation of exposed heart during vagus ex-
citation.

f. Tension of ventricle during systole and diastole.

g. Observation of the changes in heart during
death from asphyxia.

h. Innervation of diaphragm by the phrenic nerves,
i. Peristalsis of intestine.

Experiment XXVII.

Carotid pulse in man 155

a. Form of the pulse curve.

b. The pulse rate.

c. Duration of systole and diastole.

d. Effect of exercise.

Experiment XXVIII.

The radial pulse studied by the tambour method. . .159

a. Form of radial pulse.

b. Postponement of the radial pulse.

Experiment XXIX.

The radial pulse as recorded by the Jacquet Sphygmo-

graph 163

a. Normal curves and effect of position of body.

b. Effect of compressing brachial artery.

c. Effect of deglutition.

d. Effect of inhalation of Amyl Nitrite.

e. Valsalva's experiment.

f. Aliiller's experiment.

Experiment XXX.

Capillary circulation in the web of the foot of a frog 169

I. In small artery.

II. In small vein.

III. In capillaries.

IV. Vaso-motor action.

V. Diapedesis.

CONTENTS XI

Experiment XXXI.

Measurement of human blood pressure in different

positions. 173

a. The systolic pressure.

1. Gsertner's Tonometer.

2. The Riva-Rocci Sphygmomanometer.

3. Erlanger's Sphygmomanometer.

b. The Diastolic pressure.

Experiment XXXII.

The normal sounds of the heart 179

a. Auscultation over the lower part of the chest.

b. Auscultation over the base of the heart,

c. Time relations of heart sounds and pulse.

• Experiment XXXIII.

Thorasic and abdominal movements in respiration. . 185

a. Normal record.

b. Effect of using the voice.

c. Inhibitory effects of swallowing.

d. Effects of effort.

e. Relation of rate of respiration to rate of heart.

ILLUSTRATIONS

1. Apparatus for recording the extensibility and elas-

ticity of a steel spring. i

2. Apparatus for recording the extensibility and elas-

ticity of a frog's muscle 7

3. Apparatus for recording contractions of a frog's

muscle, excited by induction shocks. . -13

4. Curve of lift and work 21

5. Apparatus for automatically exciting muscle, by

letting the drum open the key 26

6. Method of preparing myogram for determination

of latent period. . . ... . . .28

7. Apparatus for studying summation of contractions. 31

8. Scheme of electrical connections of primary coil

in two forms of induction apparatus. . . 33

9. Relation of brain to skull of frog. • • • 37

10. Dissection of right leg of frog 38

11. Apparatus recording beats of a frog's heart. . 52

12. The gross anatomy of a frog's heart. • • • 53

13. Apparatus to detect direction of flow of current in

a simple circuit 65

14. Apparatus to detect direction of flow of current

in secondary coil of an induction apparatus. . 66

15. Diagram of location of motor points on flexor side

of arm (after Erb) 66

16. Apparatus for unipolar excitation of hvmian

nerves 67

17. Arm rest for support of hand and electrodes. . 71

18. Apparatus for recording movements of thumb. 72

19. Apparatus for Galvani's experiment. . . . yy

20. Apparatus for observing polarization of electrodes. 81

21. Method of arranging non-polarizable boot elec-

trodes in moist chamber 83

22. Method of using rheocord 87

23. Apparatus for stimulating human nerves by the

direct current. 91

XIV IIvI<USTRATlONS

24. Apparatus for testing the efifect of the direct cur-

rent on the irritability of human nerves. . . 97

25. Apparatus for recording reaction time to sound. 113

26. Diagram of nervous paths followed by the nerve

impulses causing the knee-jerk and its reen-
forcements 117

27. Method of supporting thigh and foot, and of re-

cording the swing of the lower leg, in the knee-
jerk experiment 118

28. Recording tambour 128

29. Sphygmogram of a normal and of a dicrotic pulse. 128

30. Scheme of apparatus for studying the blood pres-

sure of a mammal. 135

31. Dissection of nerves of left side of neck of rabbit. 139

32. Method of inserting cannula into carotid artery. 140

33. Tambour and neck spring used to study the hu-

man carotid pulse. 155

34. Method of applying tambour to wrist, to obtain

sphygmogram from the radial artery. . -159

35. Scheme of Jacquet's sphygmograph. . , . 163

36. Laboratory form of Riva-Rocci instrument for

determining human blood pressure. . . -174

37. Diagram showing position of heart in chest, posi-

tion of valves as projected on wall of chest, and
the parts of the chest where the sounds of the
heart are heard best 179

GENERAL DIRECTIONS.

The laboratory hours are from one to five.

Each student must have receipt from the Treasurer, to
show that the laboratory fee has been paid, and have the
following articles, before beginning the work :

Towel.

Strong scissors with fine points.
Forceps with fine points.
Dividers.

Celuloid triangle (6 in.).
Reading glass.
Flesh pencil.
Tube of office paste.

2 sheets of millimeter, cross-section paper.
40 sheets of note paper of regulation size.
40 sheets of cardboard of regulation size.

In addition, each student must have a copy of these notes,
and must make a deposit of 25 cts. for key of desk.

Each section will be divided into two divisions. Divis-
ion A will make the experiments in the order in which they
are given in the notes. Division B will make the experi-
ments in the following order: I-VI inclusive: XXIV-
XXXIII, inclusive, and VII-XXIII, inclusive.

Two students will work together. They will be sup-
plied with most of the apparatus required in the course,
when assigned to their desks.

Each student is expected to perform every experiment,
and to give a full report of the results, accompanied by
graphic records which he himself has obtained, when such
are demanded by the experiment. For method of keeping
the notes and mounting the records see Experiment I.

Do not begin an experiuieut until yon have read the di-
rections in the notes, and have clearly in mind the object of
the experiment.

XVI

GENERAL DIRECTIONS

Be prepared for a quiz on each experiment at the time
it is made, and to pass an examination both on methods and
results at the end of the course.

Do not cut or mar desks or stools.

Learn to see dirt. Before leaving the laboratory see
that your table is clean and neat ; that all apparatus is dry ;
that the battery has been disconnected (it is not enough to
leave the key open) ; that all apparatus is covered.

A list of the following apparatus will be found in the
desk, and is to be checked up in the presence of the instruc-
tor and signed by both students. Larger special pieces of
apparatus will be supplied from time to time when needed.

Division A.

Acetic acid, lo per cent.

Battery jar.

Board for frog.

Brush for salt solution.

Bunsen burner, with tubing.

Two cells, dry.

Clamp, burette.

Two clamps, cabinet maker's.

Clamp, large muscle.

Six clamps, for rods.

Coil, aluminum.

Cloth to cover apparatus.

Dropper, coarse point.

Electrodes, boot form in dish.

Electrodes, copper.

Electrode, indifferent (sheet of

copper).
Electrode, active (brass).
Electrodes, pin.
Electrodes, platinum.
Filter paper.
Finger piece, wooden.
Fork and yoke.
Glass Slide on support.
Two Glasses, drinking.
Glass dish for Salt Solution.
Hook for frog.
Two hooks, pin.
Induction Coil.
Key, mercury.
Kymograph and drum.
Lever, heart, with support.
Lever, muscle, heavy.
Lever, muscle, light.

Ligatures.

Moist chamber, with wire.
Two pads, gauze.
Piece of metal to clamp to drum.
Pins.

Pinch cock.
Plate.

Potassic iodide and starch solu-
tion.
Pulley.
Ring stand.

Rod, glass with clips for boots.
Rod to support heart lever.
Rod, L, brass.
Rod, Iron.
Rod, L, nickled.
Rod, zinc.

Rubber band, large.
Two rubber bands, thin.
Two signals, electric.
Spring, steel with pointer.
Stand, long.
Stand, short.

Sodium chloride, 0.6 per cent.
Sulphuric acid, o.oi per cent.
20 Weights, ID grms.
Silk thread.

2 Wires, insulated, extra long.
2 Wires, insulated, long.
4 Wires, insulated, medium.
2 Wires, insulated, short.
Zinc Sulphate.
Two Zincs for Electrodes.

GENERAL DIRECTIONS

XVll

Division B.

Board for frog.

Brush for salt solution.

Cell, dry.

5 Clamps, for rod.

1 Clamp, cabinet maker's.
Cloth to cover apparatus.
Coil, aluminum.
Electrodes, pin.

Filter paper.
Fork, with yoke.

2 Glasses, drinking.
Glass, for salt solution.
2 Hooks, pin.
Induction coil.

Key, inercury.

Kymograph with drum, 4 fans.

Lever, muscle, light.

Lever, muscle, heavy.

Moist chamber with wire.

Pins.

2 Pinch cocks.

Plate.

2 Pneumographs.

Rod, nickled.

2 Rubber tubes, with glass Ts.

Signal, electric.

Sodium chloride, 0.6 per cent.

Spring, steel, with pointer.

Stand, long.

Stand, short.

Tambour, carotid with sprisg.

Tambour, radial.

2 Tambours, recording.

20 Weights, 10 grms.

Wire, fine copper.

2 Wires, insulated, extra long.

3 Wires, insulated, long.

2 Wires, insulated, medium.
2 Wires, insulated, short.

Students are to use the apparatus supplied them, and
no other. In no case is apparatus to be taken from the
shelves or borrowed from other students.

EXPERIMENT I.

p

Extensibility and Elasticity of a Steel Spring.

Apparatus. — The structure of the drum kymograph,
the method of fastening the paper on the drum, of blacken-
ing the paper, and of fixing the record, will be explained
by the instructor.

Examine your kymograph with care and be sure that
you understand how the clockwork is wound up ; how to
change the gearing so as to obtain the faster and slower
speeds of the drum ; how to arrange drum to be driven by
the clockwork or to be rotated by hand ; and how to raise
and lower the drum. The instrument will be in order when
you receive it and must be in order when you return it.

Mount spring and heavier mus-
cle lever on the longer iron stand.
0 i ir ^^ shown in diagram. The stand

fC^IJill^ holding the recording instruments

should always be placed to the
right of the kymograph, so that
these instruments shall point in
the direction that the drum re-
volves. The clockwork turns
the drum clockwise, and when
it is turned by hand it should
be rotated always in this direc-
tion. If the drum be rotated
backward, the recording points
are liable to be injured. All
records should read from left to right. Decide at what
part of the drum the record is to be made before finally
clamping the recording apparatus on the stand. Fasten
two pieces of thread to the writing lever at the hole second
from the axis, and attach one of the threads to the spring

rD

Apparatus for re-
cording extensibility and elas-
ticity of a steel spring. A,
joint of paper on drum; B,
lever; C, supporting screw; D,
pin hook for weight; E, steel
spring; F, V, clamps.

2 EXPERIMENT I.

8 cm. from brass supporting' rod. and the other to a pin
hook as shown in diagram. Observe the following cautions:

I. — See that the axis of the writing lever is horizontal.
2. — See that the thread connecting the lever with the
spring is vertical.

3. — See that the knots are securely fastened.

4. — See that every clamp is screwed firmly in place.

Now remove the drum from the k}mograph, fasten a
sheet of glazed "curve paper" smoothly aroinid the drum,
and blacken the surface evenly over the gas flame, rotating
the drum constantly so as not to burn the paper. Replace
the drum, place the kymograph so that the writing lever
is tangent to drum surface, touching lightly. Notice that
lever writes an arc on a curved surface. If barely touching
when horizontal, it will leave the surface and fail to vv'rite
as it moves up or down. The lever should press on the
drum just enough to write for 2 or 3 cm. above and below
the horizontal line falling through its axis. The position
of the point with reference to drum and joint of paper is
indicated in the diagram.

Experiment. — Turn the drum by hand in a clockwise
ilirection to draw a base line 3 or 4 inches long. Turn it
Lack (taking care not to injure writing points) to the smart-
ing point and mark the place by touching the lever lightly.
Now turn drum clockwise 3^ cm. and then carefully place
a 10 gram weight on the pin hook. Turn same distance
again and add another weight. Continue in this manner
until 9 weights have been added, then turn the drum Vi cm.
once more. The writing point has now recorded the curve
of extensibility of the spring. To obtain curve of elasticity,
turn drum 3/2 cm. in same direction and remove one weight,
and continue in this manner until all the weights are ofif,
then turn Yi cm. once more, and mark point by touching
lever.

The vertical lines on the drum should be of equal length.
If they are not, try to account for the error. Since steel is
])erfectly elastic, the writing point should return to the base
line. Tf it does not. trv to account for the difference.

KLASTICrTV OF STEEI. SPRING.

MOUNT !XG OF CL'RVES.

With triangle and a needle, or other instrument with a
sharp point, draw a rectangle about each record worih
preservation. It is desirable to leave a generous margin
about the curve. Cut out piece thus outlined, and mount
on the cardboard by glueing the corners on with a little
paste. If a knife be used to cut off the piece, cut upon a
piece of cardboard. Do not cut on the table. To protect
the curves, place over them the sheet of paper upon which
the notes concerning the experiment have been written.
TvCt the right hand end of the sheet overlap the cardboard
slightl}\ and fasten it to the back of the cardboard with
paste.

THE student's notes.

Write as plainly as possible on the upper left hand corner
of the paper which covers the curves, your name and the
number of each of the experiments mounted on the card.
Also head each mounted curve with the number of the
experiment and the letter of the subheading to which it
belongs, and label the corresponding notes on the cover
paper in like manner.

The notes should contain an accurate statement, not of
what the books say on the subject, but of the results act-
ually obtained by you in performing the experiment. Do
not describe the method of the experiment unless it is
different from the directions in these notes, in wdiich case
let the explanation contain all the facts required to let
another understand the exact conditions of the work. Men-
tion all sources of error which are likely to arise from the
method used. This is most important. An apparatus is
a servant employed to make observations. You must know
in what respects its report is to be trusted and where it is
liable to deceive. It is worse than useless to employ appar-
atus in experiments or in physical examinations unless you
know your apparatus thoroughly. If the results obtained
differ from those which you know to be usually obtained in
similar cases, try to explain why the dift"erence occurs.

4 EXPERIMENT I.

Look Upon each experiment as a piece of original research,
and do not be satisfied with simply carrying out directions.
Learn to cultivate the power of independent observation
and thought. You will be judged as much by the original-
ity displayed in your reports as by the accuracy of your
work. If you can learn to observe accurately and to record
your observations concisely and at the same time in suffi-
cient detail to make another understand the results of your
experiments, you will be able to make a valuable physical
examination and keep a reliable case book.

FJ,ASTIC1TY OF STEEL SPRING.

EXPERIMENT r.

ICLASTICITY OF FROG S MUSCLE).

EXPERIMENT II.

Extensibility and Elasticity of Frog's Muscle.

Apparatus. — Mount moist chamber on standard, and
fasten threads to lever so that it will magnify the movement
6 times. Have all apparatus in readiness and the drum
blackened before preparing the muscle.

MUSCLE PREPARATION.

Kill a frog under the direction of a demonstrator.
Straighten hind legs by letting hand glide over body, and

wrap legs in dry cloth. Insert
one blade of strong scissors into
mouth as far back as angles of
jaw, and with the other blade
across the head as far back as
possible, remove skull by a single
cut of the scissors. In making the
cut, hold frog, head down, over
a plate. Cut off hind legs close
to body. As there is a possibil-
ity that the brain may recover
from the shock, complete its
destruction by thrusting a blade
of the scissors into the cranial
cavity and breaking up the brain. There is no evidence
that the rest of the nervous system is capable of feeling;
nevertheless, as a matter of precaution, destroy the spinal
cord and all remnants of the brain with a pithing needle.
Be sure that all of the central nervous system has been
destroyed, for even comparatively small parts in cold-
blooded animals can recover from severe shock.

Remove the skin from the leg, and see that it does not
touch the muscles, as there is a secretion upon the skin
which is injurious. Now put leg on piece of filter paper
moistened with physiological salt solution. Clean off the

/

P \

A

d

=

a3te

p

n

1

1 ^

\

Fig. 2. Apparatus for record-
ing extensibility and elasticity
of frog's muscle. A, moist
chamber; B, femur fastened in
bone clamp; C, muscle.

8 EXPERIMENT 11.

thigh muscles from femur without injuring tendon of the
gastrocnemius muscle. Cut tendo-Achillis below ankle and
separate gastrocnemius from tibia. Remember that you are
not in the dissecting room, and that you are dealing with
living tissues. Do not touch the muscle with the fingers,
nor pinch it. nor injure it by pulling on it, etc. It can be
handled by holding the tendon with forceps. Cut off tibia
just below knee, insert and fasten femur in clamp in moist
chamber, put pin hook through middle of tendo-Achillis,
and in doing this avoid pulling on muscle. Place a piece
of wet filter paper in the moist chamber.

a. Experiment. — Repeat the work of Experiment i,
allowing an interval of ten seconds between the addition
or removal of any two weights. The drum should be moved
at the end of the lo seconds, in order that any delayed effect
of the change in load may be recorded in the proper place.
After removing last weight and waiting to seconds, if the
writing point has not returned to the base line, turn drum
again and wait one minute ; repeat this, turning drum at
intervals of one minute, until lever ceases to rise or base
line is reached. Plot the curves of extensibility and elas-
ticity of muscle. If several curves are taken with the same
muscle, keep them all and label t. 2, 3, etc. Explain in
your notes the differences observed.

b. Pi,oTTiNG OF Curves. — The curves drawn by the
writing point are inexact in two respects : the point does not
move in a vertical line, and the drum may not be moved
equal distances. To obtain exact curves of the extensibility
and elasticity, proceed as follows. Take a piece of cross sec-
tion paper and draw heavy lines for the two axes. Mark dots
at equal distances along the horizontal axis (the abscissa)
and number them 0-10-20, etc., to represent the weights
used. Place along the vertical axis (the ordinate) at equal
distances the numbers 0-5-10-20, etc., to represent the num-
ber of millimeters through which the writing point moved.
As the separate movements are small, it may be wise to
let each millimeter of movement be represented by 2 or 5
millimeters of the paper. Measure with the aid of a
magnifying glass the exact height of each movement record-

ELASTICITY OF FROG S MUSCLE. 9

£d. It is usually best to make the measurements all from the
base line. The amount of the individual movements can
be obtained by subtraction. Give these measurements in
your notes, in order that they may be checked, and enter
the results on the chart, by marking, for each observation,
a dot at the point of intersection of the vertical line corres-
ponding to the weight, and the horizontal line corresponding
to the height of lift. Now connect the dots by straight
lines. Mount the plotted curve at the side of the original.
How does extensibility differ from elasticity? How do the
curves obtained from muscle differ from those obtained
from a steel spring? How do the different curves of elas-
ticity obtained from the same muscle differ? Explain.

ro EXPERIMENT II.

KI.ASTlCiTY OI" F'KCH-;. S fJlISCLP;.

EXPERIMENT II.

RESPONSE OF MUSCI.E TO INDUCTION SHOCKS.

13

EXPERIMENT III.

Response of Muscle to Making and Breaking Induction

Shocks of Various Strengths, and Use of

Short Circuit Key.

Apparatus. — Before preparing the muscle, arrange
apparatus as indicated in the diagram, mounting the moist
chamber and lever on the tall stand. Employ the light
muscle lever in this experiment. When the weight is sup-
ported so as not to bring a strain on the muscle until it

^^^

Pig-. 3. Apparatus for recording contractions of frog's muscle, excited by in-
duction shocks. A, pin electrode; B, primary coil; C, C, posts i and 2; D, dry
cell; B, mercury key; F, secondary coil; G, short-circuiting key; H, light
muscle lever; I, yoke of lever arranged to support it; J, scheme of mercury key
in primary circuit.

contracts, we have what is known as an "after-loaded con-
traction." In this case the muscle is to be after-loaded.
Connect the muscle with the sixth hole of the lever ; see
that the thread is vertical ; rotate the yoke carrying the axis
of the lever, until it supports the lever when the thread is
tense, and tighten the screw that fastens the yoke to the
rod. Now suspend ten grams from the lever. To obtain
good results it is necessary to observe the following direc-
tions :

14 EXPERIMENT III.

I. — Clamp mercury key to edge of table.

2. — Clean and brighten all wires at points of metallic
contact.

3. — Connect wires of battery circuit (the primary cir-
cuit) to posts I and 2 of induction apparatus.

4. — Turn binding screws firmly down.

5. — Leave key in battery circuit open when not in use,
to prevent waste of battery.

6. — See that surface of mercury in key is bright, and
that. platinum loop touches mercury in both cups when key
is closed.

7. — Avoid closing key so forcibly as to jar mercury
globules.

8. — See that thread is tense when lever is properly sup-
ported.

9. — When it is not the intention to stimulate the muscle,
see that short-circuiting key is closed, to guard muscle
against accidental closures of primary circuit.

Some facts Regarding Iiidiictioji Apparatus.

Recall the following facts concerning the induction
apparatus. The wire of the primary coil, through which
the battery current flows, has no metallic connection with
the ware of the secondary coil, and consequently the battery
current does not enter the secondary coil. The current
which is used to excite the muscle is an induced current of
very brief duration, which develops in the secondary coil
at the instant that the battery current is thrown into, or is
withdrawn from the primary coil. It is the disturbance of
the magnetic field about the primary coil, that causes the
induced currents in the secondary, and the induced currents
are of very brief duration, lasting only until equilibrium
has been established. The nearer the secondary approaches
the primary coil, the more it comes under the influence of
the magnetic field about it, and the stronger the induced cur-
rents become. Like movements of the secondary coil, result
in a more and more rapid growth in the intensity of the in-
duced currents as the primary coil is approached ; a move-
ment of a millimeter when the secondary is close to the pri-

RESPONSE OF MUSCLE TO INDUCTION SHOCKS. 15

mary increases the induced current as much as a movement
of a centimeter or more when the coils are far apart. Rota-
tion of the secondary coil on the pivot, because changing the
angle at which the lines of magnetic force will cut the wind-
ings, also influences the development of the induced cur-
rents, and they become less the more the angle between the
tv/o coils approaches a right angle.

Why is the making, weaker than the breaking induction
shock ? When the battery current is made, an electro-
motive force is set up in the primary coil, and this force
induces a counter electro-motive force in that coil of opposite
direction to that of the battery current. As a result, the
disturbance in the magnetic field about the primary coil is
slow to develop and comparatively slight, and the making
induced current in the secondary coil gains its full intensity
slowly and is feeble. When the battery current is broken,
the electro-motive force induced in the primary coil has the
same direction as that of the battery current, and conse-
quently the breaking induced current in the secondary coil
gains its full intensity very rapidly and is very strong.

a. Response to Making and Breaking Shocks of Increas-
ing Strength.

Experiment. — Place muscle preparation in the moist
chamber, insert pin electrode into the tendo-Achillis (not
the muscle substance). Connect the short wire fastened
to a bit of nickled rod, with binding post on support
which carries the muscle clamp. The exciting current
will pass through muscle from end to end. Place
kymograph so that lever bears lightly on drum near
the joint of the paper. Move secondary coil as far from
primary as the construction of instrument permits, then
turn it on the pivot until it is at right angles to the primary
coil. Now open short circuit key and make and break the
primary circuit by means of the mercury key : no contrac-
tion. The simulus is sub-minimal. Gradually turn the
coil to strengthen the induced current, making and breaking
the circuit at each new position of coil. A position will be
found, either while turning the coil or afterwards by sliding
3

1 6 EXPERIMENT III.

it towards the primary, at which a small contraction will
result. Notice that the contraction occurs on breaking the
circuit and that no corresponding making contraction is
seen. Now give muscle a rest of 3^ a minute and then
try to put the secondary coil in such a position that the
contraction will be so small as to be scarcely visible. Such
a contrac:ion is said to be minimal. These later trials should
be made at intervals of not less than lo seconds. Now move
the drum a few centimeters, and record first a minimal con-
traction, and then, i cm. apart, a series of breaking con-
tractions obtained by stimulating with gradually increasing
stimuli. In stimulating, make the circuit, wait 5 seconds,
then break, and wait 10 seconds. Soon a contraction will
appear when the circuit is made, but smaller than the break-
ing contraction that goes with it. If the secondary coil has
not been moved too rapidly this first making contraction
will be nearly minimal. After a minimal making contraction
has been obtained, continue stimulating and recording as
before, excepting that now drum is to be turned ^ cm.
after each contraction. After a time the breaking and mak-
ing contractions will be maximal, i. e., will cease to grow
with increasing strength of current, and if the work is
continued, a second growth in height of contractions may
be seen, and supra-maximal contractions be recorded. Mark
on the record to indicate which contraction is a minimal
break, a minimal luake, a maximal break and a maximal
make.

b. Use of Short Circuit Key.

Move drum away, then slide secondary coil to a posi-
tion which excites making contractions about half as high
as the corresponding breaks. Return drum and record four
making and four breaking contractions, stimulating with
same time intervals as in part a, but with the strength of
current unchanged. Close the short circuit key and stimu-
late : no contraction. Two paths are now open to the cur-
rent, and the current is divided between them in inverse
proportion to the resistances. The muscle, having much
Sfreater resistance than the metal of the short circuit

KKSPONSE OF MUSCLE TO IXDLXTIOX SHOCKS. 1 7

key, gets so little current that the stimulus is sub-minimal.
This method of dividing the current is techincally known
as "shunting."

Leaving coil in same position, record a series of four
making contractions, cutting out breaks with short circuit
key, then record a series of four breaks, cutting out the
makes in the same manner. Indicate which are makes and
which are breaks in the last group of records.

:xi'r;RiMF.N"i' J 1 1.

RESPONSE OF MUSCLE TO INDUCTION SHOCKS. I 9

KXPEKIAII' NT 111

CUR\E OF WORK. , , . . 21

EXPERIMENT IV.

Relation of Amount of Load to Height of Lift and
Quantity of Work Done.

Apparatus. — The same apparatus is to be employed as
in Experiment 3, except that the heavy muscle lever is to
be used. Because of the heavy load to be carried, care
must be taken to fasten securely all clamps, threads, and
hooks. The muscle is to be after-loaded, and the support-
ing screw must be carefully adjusted so that the whole
height of each contraction shall be recorded. Have 20 ten-
gram weights ready for use.

a. Experiment. — Place muscle in moist chamber, and
make electrical connections as in Experment 3. Find
strength of current required to produce maximal breaking

contractions of unloaded mus-
cle. In doing this avoid fa-
tiguing muscle by too frequent
excitations. For stimuli use
maximal breaks at intervals of
15 seconds, and cut out the
makes with short-circuiting
key. Record on the drum at
distances of ^ cm., the con-
tractions obtained with o, 10,
20, 30, etc. grams, and contin-
ue the addition of weights un-

Fig. 4. Curveofliftandofwork. ^{\ ^\jq muSClc CaU UO lougcr
A, curve of hit; B, curve of work. "

lift the load. If more than one
experiment is made with the same muscle, state the fact,
since fatigue will modify the results.

b. Plotting of Curves. — State in tabular form on the
cardboard, by the side of the original curve, the recorded
height of lift, and the actual work done by each of the con-
tractions, (the work being th*e product of the height times
the weight lifted).

30

V

so

\

A

10

\

'\.^

0

\

/grms

sw>

/

lOV

\

y

6v(/

B

22 EXPERIMENT IV.

To plot the curves of lift and work, take a piece of cross-
section paper, about lo cm. square, and lay off axes as
shown in diagram. Plot above the abscissa line a curve
showing the heights of the contractions, — the ordinates rep-
resenting" the distances through which the weight was moved
and the abscissas the weights. Plot below the abscissa line
the curve of work, the ordinates representing the work and
the abscissas the weights. In plotting the curves, i mm. of
cross section paper can be used to represent any desired
value of the curve to be plotted. The curve can magnify
or reduce the values actually obtained. For example, i; 2,
or 3 mm. on the cross-section paper can stand for i mm. of
lift, and 5, 10 or 20 mm. on the paper can represent 100
grammillimeters. Be sure to state on the plotted curve the
values of ordinates and abscissas.

With what weight was the greatest amount of work
done? What was the actual amount of work done with
this weight? Have the results any practical bearing?

curve; of work. 23

24 EXrURIMRNT IV.

TIME RELATIONS OF MYOGRAM. 25

EXPERIMENT V.

Time Relations of Myogram.

The record of a single muscle contraction is called a
myogram. Hitherto we have been concerned onl}' with
the height of the myogram, which can be best observed
when recorded on a stationary- drum. In order to study the
time relations of the myogram, the record will have to be
taken on a moving drum, and the rate of movement of the
drum be determined with a tuning fork.

a. Influence of Rate of Dniiii on form of Myogram.

There are toda}^ a great variety of methods for
obtaining graphic records of physiological processes and
the changes which they undergo under normal and patho-
logical conditions. In many cases these records are taken
on moving surfaces, and it is important that one should be
able to estimate the influence of the rate of motion of the
surface on the shape of the curve.

Apparatus. — The apparatus for supporting the muscle
and recording its contraction, and the electrical connections
with the induction coil are to be the same in this, as in
Experiment 3, the lighter muscle lever being used. In this
experiment, however, the key in the primary circuit, instead
of being opened by hand, is to be opened automatically by
the drum when it is revolved. That this may be done,
fasten a frog board by its iron rod to clamp on short stand.
Place key in primary circuit on the board, so that it projects
for two-thirds of its length bcA'ond it, and clamp key to
board by a cabinetmaker's clamp. Adjust board so that
top of key is just above the level of the top of the drum.
Clamp to the top of the drum, so that it projects a couple
of cm. beyond it, the piece of metal supplied for this pur-
pose. See that the piece of metal does not change its place,
as it must hold a constant position with respect to the sur-
face of the drum. Now move the key just near enough to
enable the projecting piece of metal to open it.

26

KXPF.RIMENT V.

net maker's clamp; C, mercury key;
D, handle of key; E, piece of metal;
F, wires to primary circuit; G. tuning
fork; H, yoke.

Experiment. — Blacken a
drum ; bring key into position
to be opened when drum is
turned ; leave key open when
the current is not wanted.

Prepare a gastrocnemius
muscle ; suspend it in moist
chamber and connect it with
lever ; thrust pin of pin elec-
trode through tendon ; adjust
support so that muscle shall
Fig. 5. Apparatus for automatically be aftcr-loadcd zvJicii thread

exciting muscle by letting the drum • . j ±1 1 • 1

open the key. A, frog boird; B, cabi- W tCllSC mid tllC leVCl' IS llOK-

izontal. Let short-circuiting
key be closed when it is not
desired to excite muscle ;
place secondary coil so that muscle shall give a maximal
breaking contraction ; short circuit all making shocks ;
rotate drum so that the part which opens key will point
away from it. Now place stand so that the lever will write
well upon the drum. Close key in primary circuit and then
open short-circuiting key. Now open key in primary circuit
by rotating drum by hand very slowly. A breaking con-
traction will be recorded. Do not move the kymograph, or
the stands holding key and lever. Repeat the experiment
four times, each time rotating the drum somewhat faster.
Fix the record. State in notes in what respects the myo-
grams obtained differ. Save the muscle to test the appar-
atus in part h.

b. Time Relations of Myogram.

Apparatus. — Use the same apparatus as in a, with the
following additions : Mount on long stand beneath the
muscle lever a tuning fork, to mark rate of movement of
drum. Put on the wire spring, used in Experiment I, a
celluloid pointer, and clamp the spring beneath the fork, to
give a base line to be used in measuring the curves. See
that the three writing points are in the same vertical line.

Experiment. — The latent period, the duration of the
])eri()d of rise and of the ])eriod of fall, are all longer for

TIME RELATIONS OF MYOGRAM. 27

a fatigued than for a fresh muscle; it is therefore best to
test apparatus with muscle used in part a. When you have
learned to perform the experiment promptly prepare a fresh
muscle. Ascertain the current just strong enough to give
a maximal breaking contraction, and in doing this avoid
exciting the muscle more often than once in ten seconds,
and call out as few contractions as possible. If you have
to repeat the experiment frequently, state the number of
the contraction the curve of which is measured. After the
drum has been blackened, and the mercury key has been
placed so that it will be opened when the drum revolves,
see that the lever is horizontal when resting on its support
with thread tense. Then move long stand so that fork and
muscle lever will write on drum. If now the drum is
revolved, the mercury key will be opened when the muscle
lever is at a certain point on the drum surface. To find
what this point is, with short circuit key closed, close mer-
cury key ; then open short circuit key, and open mercury
key by revolving the drum z'ery slozuly. The recorded myo-
gram should be almost a single line. The contraction
of the muscle will mark the point of drum which was oppos-
ite the end of the lever when the muscle was stimulated.
Now, without changing position of key, drum, or lever,
close short circuit key, revolve drum two-thirds the way
round, put yoke on fork, close mercury key ; then pull yoke
ofif of fork and immediately open mercury key by revolving
drum rapidly. Stop drum at the close of one revolu'don.
If the muscle had contracted immediately the second curve
would have begun to rise at the same point as the first.
It does not, because the muscle has a latent period. The
distance between the beginning of the two curves shows
the length of this period, because the tuning fork curve
enables us to know how long the drum took to traverse this
distance.

c. Measurement of Records and Coiupntation of Time
Interz'als.

To determine the latent period, it is first necessary
to fix the exact points at which the two contractions
began. Draw through the point of origin of the first

28

EXPERIMENT V.

recorded contraction the line MN, perpendicular to the
base line. To fix the point at which the second contraction
began, draw on the curve two fine parallel lines, one just
above and one just below the line traced by the lever, as
at AB, to aid the eye in fixing the point. Draw through it
the line OP and estimate MO, the latent period, in thou-
sandths of a second. One double vibration of the fork is
ten thousandths of a second. A good way of ascertaining
the length of the latent period, is to estimate the value of
one millimeter of drum surface in thousandths of a second,
by dividing the time of one double vibration of the fork

Fig. 6. Method of preparing myogram for de-
termination of latent period.

by the number of millimeters in the wave which is recorded
most nearly between MO, and multiplying this value by t4^
number of millimeters in the recorded latent period.

To detenPiine the period of contraction, draw TQ per-
pendicular to MN and tangent to the muscle curve at Q.
With a radius equal to the length of the writing lever and
a center on the base line traced by the muscle lever, as at
R, revolve Q to this base line at S. draw the perpendicular
UV through S, and estimate the number of thousandths
of a second between OU. To do this count the complete
waves, and estimate in tenths the fractions of waves. The
line UV must not be drawn through Q, because the distance
WQ is due to the fact that the muscle lever draws an arc
instead of a straight line. To determine the period of relax-
ation, draw XY through the point where the muscle curve
strikes the base line at X.

State in notes length of latent period, contraction period,
and relaxation period, in tabular form. Also mention the
most likelv sources of error.

TIME RELATIONS OE MYOGRAM. 29

30

kxpkkimknt v.

CKNESIS 01' TJCTANUS.

31

EXPERIMENT VI.

Fig. 7. Apparatus for studying sum-
mation of contractions. A, block of
wood wound with aluminum wire;
B, primary coil; C, C, posts i and 2;
U, dry cell; E, bare end of insolated
wire turned back on itself.

Genesis of Tetanus.

Apparatus. — The apparatus is to be arranged as in
Experiment 3, except that the mercury key is to be omitted,
and the current of the battery circuit is to be made and
broken as follows.

Fasten the block of wood
on which the aluminum
wire is wound, to the edge
of the table by a cabinet
maker's clamp. Connect the
binding post on block with
post I of coil ; connect post
2 of coil with one pole of
dry cell ; and fasten an in-
sulated wire to the other
pole. Now bend the free
end of this wire back on
itself, so that the end shall
be smooth and rounded. "See that the wire is bright. If
this wire be touched to any part of the aluminum coil the
primary circuit will be made, and if the wire is drawn
across the coils, a series of making and breaking shocks
will be given.

a. Sitmiuatioii of Tzuo Contractions.

If two stimuli reach a muscle at a sufficiently short inter-
val the second contraction process may begin before the
first one is completed. What will be the result? In this,
as in the preceding experiments, each student is to do the
work independently.

Experiment. — Blacken drum and arrange for quick

speed ; make a muscle preparation and mount it in moist

chamber, as in Experiment 3 ; place drum so that lever

will record well. Open short circuit key ; with the drum

4

32 EXPERIMENT VI.

still, excite the muscle by drawing free end of wire con-
nected with battery across the last turn of aluminum wire
on block (Fig. y, A) ; choose a strength of induced current
which will give a good breaking and no making contraction.
Let muscle rest. Now start drum, and draw wire across
windings a and b, at such a rate as to cause two separate
contractions ; repeat several times, and more quickly each
time, until the two contractions look like one. Do not stop
the drum between the tests ; either perform them in rapid
succession, or let the drum revolve several times, making
a test with each revolution and at such a time that the
records of the succeeding tests will follow each other. How
do the records differ?

b. Incomplete Tetanus and Complete Tetanus.

Apparatus. — Use the same apparatus as in a, and in
addition mount a time signal (chronograph) so that the
writing point will write below and in same vertical line
with the muscle lever. Connect the signal with the bind-
ing posts on the side of the desk. In the time circuit, there
is a battery, and a clock which interrupts the circuit once
a second. The signal should record seconds on the drum.
The drum should run 4 cm. per second.

Experiment. — Make experiment as in a, only this time
draw wire across all the windings of the aluminum coil.
In doing this see that the hand is moved at an even rate
across the coil. The experiment is a test not only of the
behavior of the frog's muscle under varying rates of
stimuli, but your capacity to move the hand constantly at
different speeds, i. e., muscle coordination. State in notes
approximately the number of excitations per second required
to tetanize. A complete tetanus is an apparently continuous
contraction produced by a series of excitations. All our
movements are tetani.

c. Complete Tetanus Obtained ivith Automatic Interrupter.

Apparatus. — The apparatus is the same as in Experi-
ment 3, excepting that the battery and key are connected
with different posts of the primary coil.

GENESIS OF TETANUS.

33

Electrical Couiiectiojis in Primary Circuit of Induction
Apparatus.
Two kinds of coils are used by the students. Model A
in which the secondary coil slides on metal rods, and Model
B in which the secondary coil slides on the wooden base.
The way in which the binding posts belonging to the pri-
mary circuit are connected with the primary coil and the
automatic interrupter is different in these two forms of
apparatus.

..^

Fig. 8. Scheme of electrical connections of primary coil in two forms of in-
duction apparatus. A, soft iron wires in primary coil; B, hammer; C, contact
screw; I, 2, 3, binding posts.

Model A — To obtain single making and breaking shocks
use posts I and 2. To obtain tetanizing current use posts

1 and 3.

Model B — To obtain single making and breaking shocks
use posts I and 2. To obtain tetanizing current use posts

2 and 3. In each apparatus if single shocks are needed,
the battery and key are connected with the posts to which
the two ends of the wire of the primary coil are directlv
attached. If a long series of rapidly following shocks are
needed, as for tetanus, the battery and key have to be so
connected as to bring the automatic interrupter into the cir-
cuit. This is done in Model A by connecting the battery
with posts I and 3. The current can then enter by post 3.
pass to the contact screw, down the spring, then through
the wire of the primary coil, and away by post i. In Model
B, posts 2 and 3 are used. The current enters by post 3.
passes to contact screw, down the spring, through the coil,
and awav bv post 2.

34 EXPERIMENT VI.

In each case, as the current flows through the coil it
magnetizes iron wires inside it, and the hammer is attracted.
The movement of the hammer breaks the contact between
the spring and the contact screw, and the current ceases to
flow ; the soft iron wires lose their magnetism, the hammer
is released, and the spring again makes contact with the
contact-screw. Thus the primary current is being contin-
ually made and broken, and a series of rapidly following
induction shocks develop in the secondary coil.

Notice. — In order that the automatic interrupter may
work well, the contact-screw is screwed up until it barely
touches the spring when at rest.

Experiment. — After the apparatus has been arranged,
the automatic interrupter tested, and a fresh drum black-
ened, prepare a muscle and mount it in the moist chamber.
Now adjust lever to drum; see that short-circuiting key
is closed ; close key in primary circuit ; start kymograph
clockwork (quick speed) ; open short circuit key for a few
seconds ; then close short circuit key ; stop drum a few
seconds later and open key in primary circuit. If the curve
does not return to the base line promptly when the excita-
tion ceases, it is because the after contraction, known as
"Contracture," is present.

d. Fatigue Caused by Tetanus.

Experiment. — This experiment is to be made in the
same manner as c, excepting that the drum should revolve
slowly and the tetanic excitation be permitted to act on
the muscle until it is completely fatigued.

GENESIS OF TETANUS. 35

36

KXPKRIMF.NT VI.

indep]e;ndent irritability of muscle.

EXPERIMENT VII.

Independent Irritability of Muscle.

Arrange the induction apparatus for tetanizing current,
and connect a pair of copper electrodes to the secondary
circuit.

a. Experiment. — Kill a frog by pithing the brain,
(Method will be demonstrated.) Have a pointed match at
hand, and as soon as pithing needle is withdrawn plug the
skull cavity through the foramen magnum, to prevent loss

of blood and to insure destruc^
tion of brain. Slit the skin on
the back of left thigh longitud-
inally, separate the semimem-
branosus from the ileofibularis
muscle, and expose the sciatic
nerve, (see Fig. lo. Dorsal
View). Carefully separate a
portion of the nerve from the
surrounding tissues without in-
jury to the nerve or the blood
vessels. Pass a ligature under
the nerve, carrying the ends
around to the front of the thigh, and tie tightly, thus in-
cluding all the structures of the limb except the nerve.
Cover exposed nerve with filter paper moistened with salt
solution.

Inject into the dorsal lymph sac about i cc. of a stock
solution of curara. Use for this purpose a pipette with
fine point and rubber bulb. To insert pipette, raise loose
skin of back over forward part of dorsal lymph sack with
forceps, and make small opening in skin with scissors. Lay
the frog on a plate and cover it with moist filter paper. Ob-
serve that pinching the toes of either hind leg slightly,
causes a contraction of the muscles of the leg thus irritated.
As the drug takes effect, the ability of the right leg to re-

Fig. 9. Relation of brain to
skull of frog. A, cerebral hemi-
spheres; B, eyes; C, thalamen-
cephalon; D, opticlobes; E, tym-
panic membrane; F, cerebellum;
G, medulla oblongata; H, spinal
cord.

38 EXPERT MEXT VII.

spond to such irritation gradually becomes less, and after
20 or 30 minutes it ceases altogether, although the left leg
will respond as before.

When all the body but the left leg has become com-
pletely paralyzed, open the abdominal cavity and remove
the vicera, care being taken not to injure the nerves behind
them, (see Fig. 10, \'entral Mew). Cut the body in two,
leaving the last two vertebrae connected with the legs. Split

Vkntral View Doksal Vihw

Fig. 10. Dissection ofriglit leg of frog. A, sciatic plexus; B, cniralis; C, sar-
torius; D. gracilis magnus; E, gastrocnemius; K. glutaeus niagnus; G, sciatic
nerve; H, llio-fibularis; I. semimembranosus.

these vertebrae lengthwise, and holding the fragments with
forceps, dissect out the sciatic plexuses supplying the hind
legs. Do not take hold of nerves with forceps, and avoid
stretching them. Fasten pair of electrodes to the posts of
secondary coil. Stimulate these plexuses in turn with the
letanizing current. What is the result? Now apply the
stimulus directly to the muscles of the legs. What is the
result ?

INDEPENDENT IRRITABILITY OF MUSCLE. 39

Keep the preparation, to use in Experiment 8, which
should immediately follow this one.

Answer the following questions in your notes, and state
proofs :

Can curara paralyze before it produces anaesthesia?

Does curara poison nerve fibres?

Does it poison muscles?

What does it poison?

How did the drug reach the leg?

When an electric current is sent through a non-cur-
arized muscle, as in the preceding experiments, what two
kinds of stimuli mav act on the muscle?

40 i;xpe;riment vii.

INDKPF.NDDNT IRRITABILITY OF MUSCLE- .41

EXPERIMENT VII.

ISOLATED CONDUCTION OF MUSCLE. 43

EXPERIMENT VIII.

Isolated Conduction in Muscle.

Although the separate fibers of a striated muscle are in
close contact, they are like the nerve fibers in a nerve trunk,
independent mechanisms. If a fiber is excited, the condition
of activity which is aroused runs the length of the fiber
but does not spread to neighboring fibers. This fact can
be demonstrated most readily on a curarized muscle, and
by employing unipolar excitations.

Apparatus for Unipolar Excitation. — Arrange in-
duction coil to give tetanic excitations. Connect one
pole of the secondary coil by an insulated wire with
the binding post on the sheet of copper. The other pole
of the secondary coil may be left free, or, if a strong cur-
rent is needed, be connected with a gas pipe and so with
the earth.

Experiment. — Remove the sartorius muscle (see Ven-
tral \'iew. Fig. lo), from the curarized leg of the frog
used in the Experiment VII. Lay the muscle on
the copper plate. Start the automatic interrupter
and touch one edge of the muscle for a moment with
the point of a needle or other metallic instrument with
sharp point. The muscle will be seen to contract along the
edge that is touched and to curl towards that side. If the
other edge be touched, the muscle will draw together on
the other side. With a reading glass one can see that the
only fibers to contract are those near the point touched.
The current enters the muscle wherever it is in contact
with the copper plate (the indififerent pole), but being diffuse
fails to excite ; it leaves the muscle, to charge up the body
of the experimenter, at the point that is touched by the
needle (the active pole) and the dense stream causes excit-

44 EXPERIMENT VI 1 1.

atioii at that point. The strict Hmitation of the contraction
process to the fibers excited, shows that the excitation does
not spread from fiber to fiber.

Why is it necessary to supply a curarized muscle in
this experiment?

ISOLATED CONDUCTION OF* MUSCLE. 45

46

i<;xiM',Ki.v;i:N'r VI II

CONTRACTIONS OF NON-STRIATED MUSCLES. 47

EXPERIMENT IX.

Contractions of Non-Striated Muscle.

Apparatus. — Set up apparatus like that used in b of
Experiment V, with the exception of the foric, which is
replaced by a signal connected with the clock circuit, so as
to give the time in seconds. No weight should be used
on the lever.

Experiments. — Kill a frog, remove the stomach, cut
off from stomach a ring from 3 to 5 mm. wide, and hang this
ring of non-striated muscle on a pin hook which has been
fastened vertically in the clamp intended for femur. Con-
nect the lower border of the ring with the pin hook attached
to writing lever, and the pin of pin electrode. Keep moist
chamber closed and moisten muscle frequently, as it is so
small that it is especially liable to be injured by drying.

a. Time Relations of Myogram. — Proceed at once to
determine the time relations of non-striated muscle. The
method given in b of Experiment V is to be used, with the
exception that the drum is to be revolved by the clockwork,
and to have a rate of 2 mm. per second. See that writing
points are in the same vertical line, and put part of curve
showing this in your notes. Find the latent period, and the
time of the rise of the curve.

b. Rate Required to Tetanise. — Set the drum turn-
ing slowly and find by experiment slowest rate of stimula-
tion which will tetanize non-striated muscle (see Experiment
VI, b). In order to tetanize, a second contraction should
be called out a short time before the preceding contraction
has reached its full height. If one knows the latent period
and the contraction period, one can make a fair estimate
of the required rate of excitation. It may be of advantage
to introduce a signal magnet in the primary circuit to mark
the time of excitation.

c. Spontaneous Contractions. — Set the drum to run
at the rate of i mm. per second or slower, and record a

48 EXPERIMENT IX.

series of spontaneous contractions. L,et the time be recorded
in seconds. Spontaneous contractions may occur from the
first, and interfere with the determination of time relations.
If such is the case, the only way to secure the results is to
give the stimuli at such a time that one can be sure whether
the following contraction is a response to the stimulus or
a spontaneous contraction.

How does the latent period and the contraction period
of this non-striated muscle compare with that of the gas-
trocnemius? What rates were needed to tetanize these
muscles? What was the rate of the spontaneous con-
tractions ?

CONTRACTIONS OP NON-STRIATED MUSCLES. 49

50

KXPKRIMIvNT JX.

WAVE OF CONTRACTION IN FROGS HEART. 51

EXPERIMENT X.

Frog's Heart — Its Structure, and the Relative Time of
Action of the Different Parts.

Apparatus. — Set up as shown in Figure ii. Clamp
horizontally on short stand, the nickled rod with hole for
wire and binding screw in end (A), letting the free end of
the rod project about 7 cm. beyond the stand. Place a
clamp on the end of the rod, and fasten vertically in this
clamp the rod (B) carrying the lighter muscle lev-
er. Thus arranged the lever can be either raised
or lowered, or can be rotated so as to bring the
point against the drum. Loosen the screw fastening the
yoke (C) of the lever to the rod, and turn the yoke until
it supports the lever with the tip 2 cm. below the horizontal
plane passing through its axis ; then turn the screw home.
Now bring the drum up to the lever, and see that when it
is horizontal it has such a height that it can be made to
write on any part of the drum by raising or lowering the
drum. Clamp the frog board (G) to the stand below the
lever. Introduce into the fourth hole of the lever the short
piece of copper wire (B) with cork button at the end, and
fasten the piece of flexible insulated wire (F) to the binding-
post on the frog board. Observe that the two wires which
project through the button may, when brought in contact
with the heart, be used as electrodes. Put time signal on
long stand, at such a height that it will write just below
the lever when it is horizontal. In this experiment the
signal will be used only to give a base line. Blacken the
drum.

Operation. — Choose an active frog ; pith brain as
described in Experiment YII ; cut off the projecting end
of match ; and put frog, back down, on the plate. Operate
at once, before the effects of the shock have passed off. Make
median skin incision from one half centimeter above pubis to

52

EXPERIMENT X.

one half centimeter below jaw. Raise ensiform cartilage with
forceps, and with sharp scissors cut in median line through
sternum, pectoral girdle, and muscles of throat, always
keeping point of scissors well away from the pericardium
and aortae. Prolong incision .through abdominal wall,
avoiding the large vein. Slight haemorrhage can be checked
with dry absorbent cotton. Now slide the heart lever up
out of the way, and place the frog on the frog board so

Fig. II. Apparatus for recording the beat of a frog's heart. A, horizontal
roil carrj'ing binding screw for wire; B, vertical rod carrying lever; C, yoke sup-
porting axis of lever; D, time signal; ii, copper wire, connecting lever with
cork button to rest on the heart; K, piece of flexible insulated wire, connecting
short piece of copper wire, passing through cork button with binding post
on frog board; G, frog board.

that its ventricle lies directly beneath the cork button on
the prop of the lever. With the frog in this position, draw
the fore legs widely apart so as to expose the heart beating
within the pericardium, and pin these legs firmly to the
frog board. Now pick up the pericardium over the bulbus
arteriosus, and slit the pericardium throughout its length
with sharp pointed scissors.

WAVE OF CONTRACTION IN FROGS HEART.

53

a. G?-oss Anatomy of the Heart.

Moisten the heart from time to time with normal salt
solution ; it must not be allowed to dry. Observe the posi-
tion of the bulbus arteriosus (H) and the two aortic arches
(A) ; the relation of the two auricles (B, C) to each other
and to the ventricle (£). (the line of separation of the
auricles lies behind the bulbus arteriosus) ; and the well
marked auriculo-ventricular groove. Lift the ventricle with
a camel's hair brush moistened with saline solution, and
notice the place where the vena cava inferior opens into
the sinus venosus (F) \ the white crescentic line where the

Dorsal View

Ventral View

b'ig. 12. The gross anatomy of frog'8 heart. (Ventral view after Cyou, dorsal
view after Howes.) A, aortae; B, right auricle; C, left auricle; D, pulmonary vein
K, ventricle; F, sinus venosus; G, sinu-auricular valves; H, bulbus arteriosus.

sinus joins the auricle ; also the frenum, a slender ligament
which attaches the dorsal wall of the ventricle to the peri-
cardium.

b. Origin and Course of the JVavc of Contraction.

I. — Inspection. — Try to observe the place where the
wave of contraction begins, and the order in which it spreads
over the different chambers of the heart. See that when a
part contracts and drives the blood out, it grows paler,
while the part receiving the blood swells and flushes. Ans-
wer in your notes the following questions : What is the
action of the auricles during the ventricular diastole, and
during the ventricular s)'Stole? What changes are observed
in the ventricle during auricular diastole, and during auric-
ular svstole?

54 EXPERIMENT X.

2. — The Myocardiogram. — Adjust the cork on the
prop of the lever, to the ventricle, with the prop vertical and
the lever horizontal. Be careful that both of the wire
points on the under surface of the cork are in contact with
the ventricle, and that the cork does not touch the auricle
so as to be moved directly by it. Once rightly adjusted,
it should not be necessary to alter the position of the lever
during the afternoon. The prop should be connected with
the hole in the lever which will give a writing of one and a
half to two centimeters in height. Record the beats with
slow, medium and rapid speeds of the drum, studying the
heart itself while the curves are being written. Mark on the
record the part of the cardiac cycle which is responsible for
each wave of the curve. How and why does the beat of
the auricle show in the curve? Which part of the curve
was made by the ventricular systole? Does the lever fall
or rise in the ventricular diastole? Explain.

WAVE OF CONTRACTION IN FROGS HEART. 55

56 KXPERIMKnT X.

REFRACTORY PERIOD.

EXPERIMENT XL

Refractory Period and Compensatory Pause.

Apparatus.— The same frog and the same apparatus
for recording the contractions of the heart may be used as
in the preceding experiment. In addition arrange an induc-
tion coil to give single shocks, placing a time signal in the
primary circuit, and arranging it to write just below and
in the same vertical line with the heart lever. One cell in
the primary circuit, with the secondary coil pushed half
way up, usvially gives sufficient strength of current. One
of the wires from the secondary coil is to be fastened to
the binding post on the frog board, and be brought in com-
munication with the ventricle by means of the fine insulated
wire passing to one of the pins in the piece of cork resting
on the ventricle (see Fig. 1 1 ) ; the other wire is to be fastened
to the horizontal rod supporting the heart lever, through
which it communicates with the heart.

Experiment. — When all is ready, mark the relative
position of the writing points on the drum. Don't forget
that unless this is done, and the length of the lever is given
in the notes, the experiment will not be accepted. Also,
either before or after the experiment, place the lever hor-
izontal, and let it record a base line to be used in measuring
the curve. Let the drum run at the rate of 20 mm. per sec-
ond. While the heart records its contractions , stimulate the
ventricle with single breaking shocks every fifth or sixth
beat, the makes being short circuited, to test the effect of
exciting it at the following times, — during the systole of
the ventricle, and early and late in the diastole of the
ventricle.

State in notes in which case the stimulus produces no
effect (the "Refractory period'') ; when it produces a con-
traction of increased height ; when an extra contraction of
less height than usual ; and when one of usual height. No-
tice that an extra contraction is followed by a pause. Is

58 EXPERIMENT XL

the pause long enough to compensate for the extra contrac-
tion, so that the rhythm of the beat is not changed after-
ward ? Such a pause is called a "Compensatory pause."
and is explained on the theory that the irritability of the
ventricle is lessened by its extra contraction, so that it can-
not respond to the stimulus which comes to it from the
auricle at the usual time for the next beat. Can you detect
a beat of the auricle at the time it usually comes, during
the compensatory pause?

The curve of contraction is distorted by the fact that
the lever records an arc. To determine the part of a con-
traction at which a stimulus was applied, it is necessary to
draw a vertical line through the point of excitation as given
by the time signal, to a base line which corresponds to the
position of the heart lever when horizontal, and then hav-
ing allowed for the relative position of the writing points,
to draw through the heart curve an arc. the axis of which
is on this base line and the radius of which is equal to the
length of the lever.

RKFRACTORY PERIOD. 59

6o EXPERIMENT Xr.

EXCITATION OF THE RESTING HEART. 6 1

EXPERIMENT XII.

Response of the Resting Heart to Stimulation by Induc-
tion Shocks.

Apparatus. — Use apparatus the same as in Experiment
XI, and in addition, mount a tuning fork on large stand
above the electric signal. Be sure that the writing points
are in the same vertical line. Prepare a frog, and expose
heart, losing as little blood as possible.

Experiment. — Bring heart to rest by tying a ligature,
the first Stannius ligature, about the juncture of the sinus
with the auricles. To do this pass ligature under the aortic
arches close to the auricles, then pass the ends around the
heart posteriorly so that the ligature lies at the base of the
auricles, and tie a single knot loosely over the crescentic
line where the sinus and the auricles join. Make sure that
the ligature is in the proper place, then tighten and tie
securely. The heart should stop beating. If it does not do
so within a few seconds, tie a second ligature closer to the
auricles.

a. Myogram of Heart Muscle.

As soon as the beat stops, place frog on board and con-
nect heart with lever. Move coil far away, and find small-
est stimulus that will cause a contraction ; then mark on
drum relative position of writing points ; finally record the
curve of contraction and beneath it the tuning fork curve,
and the moment of make and break of the primary circuit,
as shown by the signal. Turn the drum by hand at rate of
about lo cms. per second. Assume that the signal records
the exact moment of excitation, and calculate from the rec-
ord the time relations of the myogram, as in Experiment V.
Save a part of the record which shozvs that the zvriting
points are in the same vertical line, and state in notes length
of lever in millimeters. In what respect does the myogram
obtained from the heart diflfer from that of striated muscle?

62 EXPERIMENT XII.

b. Bozi'ditch's Staircase.

As soon as a sufficient number of myograms have been
recorded, remove the fork, and stimulate about 15 times
with same strength of current at intervals of 5 seconds,
recording on drum moving 2 mm. per second. A gradually
increasing height of contraction is usually given, which is
called a staircase, and explained as a result of increased
irritatibility due to frequent repetition of the stimulus.

c. All Contractions Maximal.

Now stimulate about ten times with gradually increas-
ing current at intervals of 30 seconds, recording contractions
on drum about i cm. apart. There is no increase in height
of contraction due to increased stimulus. Any stimulus
sufficient to cause heart muscle to contract causes a maximal
contraction. This is often spoken of as the law of "All
or none."

d. Bifcct of Frequent Stimuli.

Connect wires of primary circuit with automatic inter-
rupter and record the response of the heart to frequent
stimuli, using first a weak and then a medium current. Drum
should turn 5 mm. per second. Weak stimuli should cause
separate beats and stronger stimuli, increase of tonus, indi-
cated by a higher base line.

EXCITATION OF THE RESTING HEART. 63

54 EXPERIMENT XII.

MOTOR POINTS ON THE ARM. 65

EXPERIMENT XIII.

Location of a Few Motor Points on the Human Arm.

The few motor points surrounded by a circle in the dia-
gram (Fig. 15), are to be located on each arm. In doing
this, the unipolar method of excitation is to be employed.
To use this effectively, the more efficient pole of the induc-
tion coil will have to be used.

The more Efficient Pole of an Induction Coil. —
When the manner of winding and connecting wires with
posts can be plainly seen, the direction of induced currents
can be found easily, for the direction of the primary cur-
rents can be observed by inspection of the battery and its
connections, and the induced current flows in the opposite
direction to the battery current at the time of the make, and
in the same direction at the time of the break. But in most
coils the windings and connections are hidden, making it
necessary to determine the point in question in some other
way.

Connect a dry cell with a key and a pair of platinum
electrodes as shown in Figure 13. Lay a small piece of

filter paper on a clean plate,

^ (f?^""""' '"■^--M ^^^^ slightly moisten it

'C~~-~-'^^*~~- --'-''^"^ c with only a few drop*^ of

, , a solution of starch and po-

Fig. 13. Apparatus to detect direction . . ,. , -^

of flow of current in a simple circuit. taSSUUll lodldc. Draw the
A, dry cell; B, mercury key; C, electrode. 1 r 1 1

ends of the electrodes slow-
ly and lightly across the moistened paper, first with the
circuit open and then with it closed. Observe the dark line
given at the anode while the current is passing, and the ab-
sence of color at the kathode. The current decomposes the
potassium iodide, and the iodine, being the acid ion. goes
to the anode and there gives the color reaction with the
starch.

Now connect the cell to the primary coil of induction
apparatus, the anode v^^ith post i and kathode with post 2.

66

EXPERniENT XIII.

Connect the platinum electrodes to the posts of the second-
arv coil. Place the ends of the electrodes on the moistened
paper and make the primary circuit, then slide the electrodes

Kig. 14. Apparatus to detect direction of flow of current in secondary coil
of an induction apparatus. A, dry cell; B, mercury key; C, primary coil;
U, secondary coil; E, electrode.

lo a fresh place and break. A dark dot will be given at one
pole on making and at the other on br.eaking, but no effect
will be seen during the time the primary current is flowing.
Remembering that the color reaction indicates the anode,
we can determine the direction of the current in the second-
ary circuit when the primary is made and when it is broken.
Since the excitation developed at the kathode where the
current leaves the tissue, is stronger than that developed at
the anode where the current enters it, and since the break
induction shock is stronger than the make, it follows that the

Fig. 15. Diagram of location of motor points on flexor side of arm. (After
Erb.) A, median nerve in upper arm; B, flexor longus policis; C, median nerve
at wrist; D, ulnar nerve in upper arm; E, ulnar nerve in groove between the
internal condyle of the humerus and the olecranon process; F, flexor profundus
digitorum; G, flexor sublimis digitorum; H, ulnar nerve at wrist; I, abductor
minimi digiti.

more efficient pole of the secondary circuit is the one that
is the kathode when the primary circuit is broken. Make
a note of this point, stating whether the more efficient pole
is the one to which the short circuit kev is attached or the

MOTOR POINTS ON THE x\RM.

67

opposite one. Of course it must be remembered that these
are correct only when the primary circuit is connected as
directed here.

Pre;paration op Skin. — Since the epidermis when dry
offers great resistance to the current, it is necessary to
moisten it thoroughly. For this purpose use a warm sok:-
tion of com^mon salt and borax. The solution can be
warmed in a granite dish, standing on a tripod over
a gas flame. Apply the solution with a sponge or cloth
to the parts to be stimulated at intervals of a few min-
utes ; or a pad soaked in the solution may be bound
on and left 10 or 15 minutes. Unless the skin is thoroughly
moistened, the stimuli are apt to be painful and inefficient.
Do not spill the solution on tables or apparatus.

Apparatus. — Connect two dry cells and a key to the
primary coil of an induction apparatus, and connect a large
copper plate (the indifferent electrode), to the least efh-
cient pole of the secondary coil, and a small electrode (the
active electrode), to the more efficient pole.

►^

-| n

^ -J

J D U

d

-1/ — — — Q^~Q)'

Fig. 16. Apparatus for unipolar excitation of human nerves. A, battery; B,
mercury key; C, primary coil; D, secondary coil; E, copper plate used as indif-
ferent electrode; F, exciting electrode.

Experiment. — Locate the motor points on the left arm
first. Fasten with elastic band the copper plate on the back
of the left hand, putting a wet gauze pad between to pre-
vent the metal from touching the skin. Hold the stimulat-
ing electrode in the right hand and press it firmly upon the
skin at the point to be stimulated. Let your companion
make and break the circuit, first with the secondary coil
moved far away and then with it closer to the primary,
until a position of the coil is found that gives a moderate
stimulus. As soon as a suitable stimulus is found, try to
establish on your own arm the motor points corresponding
to those marked with a circle in the diagram. Find for

(8 EXPERIMENT XIII.

each point the position of the electrode at which the best
motor response is given. The stimulating electrode must
be kept well moistened. If a good contraction cannot
be obtained without the sensation being painful, it indi-
cates either that the epidermis is not sufficiently moistened
or that the right position for stimulation has not been found.
Locate carefully the motor points on both arms of each
student. Mark the points on the skin. Demonstrate to
instructor. No notes are required.

MOTOR POINTS ON THR ARM. 69

yo EXPERIMENT XIII.

ELECTRICAL EXCITATION OF HUMAN MUSCLE.

71

EXPERIMENT XIV.

Response of Human Muscle to Separate Induction
Shocks and to a Tetanizing Current.

Wet the left arm over the motor point for the flexor
longus pollicis, bind on a wet pad, and then arrange the ap-
paratus. See that the hands are dry in handling the appar-
atus.

Apparatus. — This consists of an arm rest, recording
instruments, and the stimulating outfit used in Experiment
XIII. The arm rest is to be placed on the table before
which the subject is to stand, with the recording apparatus
to the left, and the stimulating outfit to the right, with key
and coil within easv reach of his hand. The arm is to

Fig. 17. Arm rest for support of hand and electrodes. A, arm rest; B, hori-
zontal rod fixing hand; C, vertical rod on arm rest; D, copper plate, the indif-
ferent pole, on which is the gauze pad; E, exciting electrode; F, vertical rod,
clamped to horizontal rod on the arm rest.

lie in supination on the arm rest, and the hand is to be fixed
by a horizontal rod (B) which presses lightly on the palm,
and is clamped to the vertical rod on the arm rest.

The movement of the thumb is to be transmitted by a
thread, which is fastened by a loop to the thumb and passes
round a pulley to a lever, which is connected by another
thread to a rubber band supported on an L rod, clamped
to the same stand as the lever and above it. The thread
from the thrmib is fastened to the second, and that from the

72

EXPERIMENT XIV.

finger to the third hole in the lever. When the flexor longus
pollicis contracts, the lever will be drawn down, and when
it relaxes the rubber band will pull the lever upwards . A
time signal is to be placed in the primary circuit of the
induction apparatus, and an indifferent and a stimulating
electrode connected with the posts of the secondary coil.
The copper plate (Fig. 17, D),
which is to act as the indifferent
pole, is to lie on the arm rest in
such a position that the back of the
hand will press on a wet pad placed
over the plate. Care must be taken
that the pad does not come in con-
tact with the vertical rod on the
arm rest. The active pole (E) in-
stead of being held in the hand, is
to be fastened above the arm in a
clamp on a horizontal rod, which
in turn is clamped to a vertical rod
(F), which is supported by a clamp
fastened to the horizontal rod at
the side of the arm rest. This ar-
rangement permits the exciting
electrode to be fastened at any de-
sired point on the arm.

Lnj>

Kig. 18. Apparatus for re-
cording movement of thumb.
G, rubber band supported by
Iv rod; H, recording lever; I,
time signal; J, pully; K,
thread to thumb.

a. Making and Breaking Induction Shocks of Various
Strengths.

Experiment. — Put the wet pad on the indifferent elec-
trode ; then place the arm on the arm rest, so that the back
of the hand rests on the pad ; and fix the hand by fastening
the horizontal rod across the palm. Adjust the active elec-
trode over the motor point of the flexor longus pollicis mus-
cle. Connect the thread to the thumb, and move the arm
rest so that the thread shall have the proper position with
respect to the pulley, and the elastic band be slightly
stretched. Place drum in position. The lever should now
be about horizontal, and flexion of the finger cause it to
write well on the drum. The subject handles the key and

ELECTRICAL EXCITATION OF HUMAN MUSCLE- 73

coil while his associate has charge of the kymograph, and
turns the drum by hand. To stimulate, close the key,
wait 2 or 3 seconds, then open, and wait lo seconds. The
student attending to the kymograph should keep the time
with his watch and tell the subject when to stimulate. Be-
gin with the coil placed so as to give no effect, and move
it up a short distance after each time the circuit is broken.
The signal marks the time of slimulation, and thus shows
what stimuli fail to give contractions. In case insufficient
current is obtained, cut out the time signal. Unless the
current causes too much discomfort, continue until both
making and breaking contractions of fair size are recorded.
During the experiment the arm should be completely re-
laxed. Vohmtary movemicnts should be avoided as far as
possible, and should be noted when they occur.
b. Tetaiiizing Current.

Apparatus. — Connect battery, key, and signal with the
automatic interrupter of the induction coil.

Experiment. — Moisten electrodes. Choose strength of
current sufficient to cause a tetanic contraction. Start drum
at fast speed and obtain a record.

74 EXPERIMENT XIV.

KLKCTRICAL I;XCITATI0N OF HUMAN MUSCI,E. 75

76 EXPERIMENT XIV.

GALVANl's EXPERIMENT. 77

EXPERIMENT XV.
Galvani's Experiment.

Arrange apparatus as shown in the diagram, making

sure that the zinc rod and brass hook are bright and clean.

Kill a frog, open the abdomen, and

remove the viscera from the posterior

part, taking care not to injure the

^ ^ nerves. Cut the body in two trans-

y versely ^ cm. above the point of exit

of the nerves from the spinal column.

Remove the skin from the lower part

of the body, cut a small slit through

B the back between the nerves and the

spine, and hang the preparation by this

slit upon the brass hook. Adjust the

zinc rod so that upon giving the prep-

„. , aration a slight swing the outside of

Fig.ig. Apparatus ^ ^ .,,.,.

for Galvani's experi- tlic thigh near the kucc Will stnkc it.

ment. A, brass hook, r, , • • • tt

supported on L rod; B, Set the preparation swinging. Upon

zinc rod. , i r i i • j ,i

each touch of the leg against the zinc
rod a contraction should occur, throwing the preparation
away, and this should be repeated every time the swing
brings the leg against the zinc.

We have here two unlike metals moistened by a liquid
which is practically continuous through the tissues of the
preparation ; in other words, we have the essentials of what
is called a Galvanic battery. This experiment is of consid-
erable historical interest, for it was the observation of the
contraction of frogs' muscles in a similar case that led
Galvani to make his famous studies of what he supposed
to be animal electricity, and which was followed later by
the invention of the first battery by Volta.

We see here that a battery current, like an induced cur-
rent, is able to excite muscle. In the next few experiments

cO

jS EXPERIMENT XV.

the effects of the direct battery current upon nerve and
muscle will be observed. Save the preparation for the next
experiment, if made the same day.
No notes required.

c,A],vANrs i;xperim]<;nt. 79

8o EXPERIMENT XV.

POLARIZATION OF ELECTRODES.

EXPERIMENT XVI.

Polarization of Electrodes.

a. Polarizable Electrodes.

Apparatus. — Arrange apparatus as shown in Fig. 20.
Use an electric light switch as a short-circuiting key, fasten-
ing two wires to each
binding post. One wire
from each post of the key
is to be connected with a
post on the outside of the
moist chamber, and one
wire from each post of the
key is to be connected with
the battery. Until every-
thing is ready, however,
leave one end of one of the
battery wires disconnected.
Fasten two short wires to
the posts inside the moist
chamber and place the
free, bare ends so that a
nerve can be laid across
them, i. e., arrange these
wires to be used as polar-
izable electrodes. It is
best to have the connections with the battery so that, when
the short-circuiting key is open and the battery circuit is
closed, the anode will be nearest the muscle, and an ascend-
ing current, i. e., away from the muscle, will flow through
the nerve.

Experiment. — Make a nerve-muscle preparation from
the frog used in the preceding experiment, (method of mak-
ing preparation will be demonstrated) ; place the prepara-
tion in the moist chamber, and let the nerve rest across the

Fig. 20. Apparatus tor observing polar-
ization of electrodes. A, nerve; B, bare
copper vsrires; C, electric light switch
used as short circuiting key; D, battery.

82 EXPERIMENT XVI.

two copper wires. Bring the writing point of the lever
against a drum, and arrange the kymograph to turn the
drum 2 mm. per second. Start the kymograph, and let it
run continuously until the end of the experiment. With
key closed, connect wire with battery, and then open the
key and let the current flow through the nerve for thirty
seconds ; ( uiark the contraction ivhich should occur zvhcn
the key is opened, c, because the current has been closed
through the nerve) ; now disconnect the wire from the bat-
tery ; (mark the contraction, if any occurs, o) ; then begin
closing and opening the key regularly, once a second. If
contractions result, continue until they cease. Notice wheth-
er the contractions are given on closing or on opening the
key. or both, and mark them accordingly, C and 0, since
it is now the polarization current which is closed and opened.
Notice carefully, throughout the experiment any change
in the contraction following closing and opening the cir-
cuit. The contractions observed after the battery has been
disconnected are caused by a current going in the opposite
direction from the battery current, i. e., a descending cur-
rent. This current results from electrolysis which has taken
place at the points of contact of the nerve with the wires.
The condiiion set up at these points by the passage of the
battery current is the same as that seen in a storage battery,
and the wires are said to be polarized. In order to avoid
such disturbing currents it is necessary, whenever the direct
current is used as a stimulus, to employ non-polarizable
electrodes .

b. Non-Polaricable Electrodes.

Ai'PARATus. — The non-polarizable electrodes used in
this course, consist of two boot-like pieces of porous baked
claw hollowed at the top to hold a solution of zinc sulphate,
in which two small pieces of zinc are immersed. The boots
of the non-polarizable electrodes should have stood for some
lime in physiological salt solution, so that they are thorough-
ly saturated with it at the time they are employed. When
they are to be used, dry the glazed tops thoroughly ; put the
metal clips on the tops of the boots ; fasten the clips on a

POLARIZATION OF ELECTRODES.

83

glass rod ; and fix the rod in a clamp on the support which
holds the muscle clamp, in the moist chamber. Dry the
wires just used as electrodes, and connect them to the
zincs ; with a dropper put about
half a cubic centimeter of zinc sul-
phate into the boots, being careful
not to spill any of it on the outside
of the electrodes. Then insert the
zincs into the tops of the boots.

Experiment. — Lay the nerve
across the tips of the boots and re-
peat the experiment made before.
If the electrodes are not polariza-
ble, closing and opening the bat-
tery circuit should give the same
effect as before, but there should
be no response to the movements
of the key which follows.

On completing the day's work,
the non-polarizable electrodes must
be thoroughlv washed and soaked

Eig. 21. Method of arrang-
ing non-polarizable boot elec-
trodes in moist chamber. A,
zinc; B, porcelain boot; C,
nerve; D, wires to short-
circuiting key.

over night in normal salt solution.

Pfliiger's Law.

The polarization current which is set up, is strongest at
first and gradually fades away ; consequently in the course
of an experiment, the student often sees the effects of the
opening and closing of strong, medium, and weak currents.
These effects, which differ with the direction in which the
current flows through the nerve, have been classed under
what is known as Pfliiger's law. To recall this law one
has only to remember the following facts, viz.: i, that the
closing excitation develops in the region of the kathode, and
the opening excitation near the anode ; 2, that the closing
excitation is the stronger; 3, that by strong currents the
conductivity of the nerve is lessened at the anode during
the flow of the current, and at the kathode at the instant
that the current ceases ; 4, with an ascending current the

84

EXPERIMENT XVI.

anode is nearer the muscle, and with a descending current
the kathode is nearer the muscle. The law was tabulated
as follows :

Ascending

Descending

Close Open

Close Open

Weak.......

Medium. . . .

Strong

+ -

-\- —
+ +
+ -

i>OT<ARrzA'riON OF electrode;s. 85

EXPERIMENT XVI.

KI'SPONSE OF NERVE TO DIRECT CURRENT.

EXPERIMENT XVII.

Response of Nerve upon Closing and Opening the

Direct Battery Circuit with Currents of

Various Strengths.

Apparatus. — Use the ordinary apparatus for recording
muscle contractions. Introduce a rheocord into the circuit

used in the last ex-
periment, making
connections as in-
dicated in Fig. 22.
Mount a pair of
n o n - p o larizable
electrodes, in the
moist chamber,
connecting the
wires so that the
current will ascend
the nerve. Observe
that the current
passes down the
fine German silver
wire of the rheo-
cord to the slider
and there divides,
part going to the
nerve and part go-
ing through the
lower part of wire.
At the double post
at bottom of wire
the two streams of the current imite again and pass togeth-
er to the battery. Observe that the current traversing the
nerve must increase as the slider is moved upward, because
the resistance in the wire beyond the point where the circuit
divides is increased.

Fig. 22. Method of using rheocord. A, german
silver wire; B, slider; C, double binding post at
lower end of german silver wire; D, battery; E,
key; E, nerve bridging the boot electrodes, the
current being ascending.

88 EXPERIMENT XVII.

Experiment. — Since the direct current rapidly changes
the irritabiHty of a nerve, the following Cautions must be
observed :

I. — Do not apply the current at all except when you
wish a record.

2. — Do not let the current flow longer than is absolutely
necessary.

3. — Obtain the record by comparatively few stimulations.

4. — Do not excite oftener than once in 15 seconds.

Move the slider to the bottom, then close and open the
key. There should be no response. Move slider up 2 or
3 cm. and repeat. Continue in this manner, and mark on
the curve the positions of the slider at which minimal and
maximal, closing and opening contractions were obtained.
Record as in Experiment III. Did the closing or opening
contraction appear first? Did Wundt's closing or Ritter's
opening tetanus show? If your preparation reacts well,
and if you like, you may observe the facts tabulated as
Pfliiger's law (see Exper. XVI) ; this is not required,
however.

RKSPONSlv or' NERVK TO DIRECT CURRENT.

go EXPERIMENT xvrr.

ricsponse; of human nerves to direct current. 91

EXPERIMENT XYlll.

Stimulation of Human Nerves by Direct Current.

Apparatus. — The electric current of the University is
used. (Study diagram). It flows through 4 lamps, (which
let 1.2 amps, pass) and then is shunted round 4 more
lamps, and has at the terminals A and F, a voltage of 220/2
^iio volts. It then passes through 2 lamps A and B,
(which let 0.35 amps, pass) and is shunted round 3 lamps,
C, D, and £, and has a voltage at the terminals N and P,
of 3 X 1 10/5 = 66 volts.

Fig. 23. Apparatus for stimulation of human nerves by a direct current. A,
B, C, D, E, F, binding posts in second bank of electric lamps used to cut down
the voltage; G, key; P, post where current enters, and N, where it leaves rheo-
stadt; PP, post connected with slider, from which current goes to milamme-
ter; H, slider; I, milammeter; J, commutator for reversing current; K, elec-
trodes; NN, pole on rheostadt connected with N ind receiving current
returning from commutator.

In the rheostadt it is again shunted, the current passing
through the resistance from P to A^ and a portion of it
heing led off through the metal slider (H) to the arm cir-
cuit. The resistance is equivalent to the German silver wire
of the rheocord used in Experiment XVII. The slider is con-
nected with the post PP. which gives the branch of current
to the arm circuit, and the current returns from this circuit

92 EXPERIMENT XVIII.

to post A'A', which is connected with post A'. The amount
which goes to the electrodes varies with the position of the
metal slider. Note that as the slider is moved clockunse the
resistance betzveen the slider and post N increases and hence
more current zvill go to the arm. A key (G) controls the flow
of the current to the rheostadt. From terminal PP of the
rheostadt the current flows through a milammeter (/), com-
mutator (/) with cross wires, vvhich permits the current to
be reversed, to the positive electrode, the Anode ; it then
flows through the arm to the negative electrode, the
Kathode, and back by way of commutator to the pole A' A''
of the rheostadt, and thence to pole A' and away.

Experiment. — When ready for this experiment report
to instructor. Two stimulating electrodes are used in this
experiment, one being applied to each arm. Either the
median or the ulnar nerve may be stimulated, and either
the motor point near the elbow or the one near the wrist
be used. Choosing the one which in the preceding ex-
periments gave best results, wet the places on the two arms
thoroughly, bind a wet pad on each, and while the skin
is becoming saturated, study the apparatus on the main
table. See that hands are dry zvhen apparatus is handled.
Using your own induction coil, ascertain again the exact
points giving the best motor response. Mark these, and
then proceed to table where experiment is to be made.
Bring slider against -flat side of checking-post, and see that
key is open. Then place the arms in the arm supports (see
Fig. ly) and pressing the electrodes firmly over the motor
points, make the electrodes fast.

In making the experiment the subject sits quietly,
watches for first appearance of sensation or contraction re-
sulting from the stimuli, and reports at which pole it occurs.
The other student, who is the experimenter, handles the key
and rheostadt, reads the milammeter. and records the re-
sults in a table of the following form, stating the number
of milliamperes required to produce the eff^ect sought.

RESPONSE OF HUMAN NERVES TO DIRECT CURRENT. 93

TADLE OF STRENGTHS OF CURRENT REQUIRED TO PRODUCE
EFFECT.

Kathode on hand.

SENSATION. CONTRACTION.

Kathode closing' ,

Anode closing

Anode opening , ,

Kathode opening

When all is ready the experimenter closes and opens
key. There should be no movement of milammeter needle
and no effect at electrodes. He then advances the slider
a short distance, closes the key, saying "close," then as
soon as the milammeter reading can be made, opens
the key and says "open." Experimenter must watch mil-
ammeter, leaving subject to report effects. If the current
is allowed to flow too long there are changes in irritability
which destroy the value of the results. Advance slider
again and stimulate again. Continue in this way, trying
to find the least current that will give the effects mentioned
in the table. Of course the experiment must stop when the
stimulus causes too much discomfort. KOC is usually not
obtained for this reason. No graphic record is taken.
When table is completed, return slider to place of starting,
rock the commutator, to reverse the current, then stimulate
with various strengths of current as before. Observe that
the order of appearance of KCC, ACC, AOC, KOC, are
the same as before, but that they appear at the opposite
hand. Do not take time to read milammeter in the second
test. Table is to be made out for each student, and each
reports results obtained by the experiment on himself.

94 KXl'F.RIMENT XVni.

RESPONSE OF HUMAN NERV'ISS TO DIRECT CURRENT. 95

gS ■ EXPERIMENT VIII.

EI^P'ECT OF CURRENT ON IRRITABILITY OF NERVES. 97

EXPERIMENT XIX.

The Influence of the Direct Current on the IrritabiHty
of Human Nerves.

The plan of this experiment is to stimulate the nerves
with induction shocks, and then, while the excitation con-
tinues, to introduce the direct current at the same electrodes
and observe the effect of the latter upon the sensory and
motor effects of the excitation.

Fig. 24. Apparatus for testing tlie effect of a direct current on the irritability
of human nerves. G, key; F, post where current enters, and N, where it leaves
the rheostadt; PP, post connected with the slider, from which current goes to
mllammeter; H, slider; I, milammeter; J, commutator; K, electrodes; NN,pole
on rheostadt connected with N, and receiving current returning from commu-
tator; X,, secondary coil of induction apparatus; M, primarj' coil; O, key; Q,
dr5' cell.

Apparatus. — Use the apparatus employed in Experi-
ment XVIII, and in addition connect battery and key with
the automatic interrupter of the induction coil, and connect
the secondary coil with commutator and one of the elec-
trodes as shown in Fig. 24. X^otice that the induced cur-
rent will pass through commutator, milammeter, and rheo-
stadt and that the direct current will pass through the
secondary coil. In other words, the direct and induced
currents will flow at the same time through rheostadt, mil-
ammeter, commutator, secondary coil and electrodes.

98 EXPERIMENT XIX.

Students are apt to become confused in this experiment
because two electric currents are used, getting the impres-
sion that the two currents in some way neutralize each other
in traversing the same path. This is not the case. The
changes observed in the response of the nerves and muscles
to the induction shocks when the direct current is passing
are due to changes in irritability of the nerves caused by
the direct current, the anode of the direct current lessening
and the kathode increasing the irritability of the nerve.
The tetanizing induced current is used simply as a means of
exciting the nerve a definite amount. Like results arc-
obtained if the nerve be excited by a mechanical stimulus,
as a blow from a light hammer.

Experiment. — Wet arms and electrodes; place the lat-
ter over nerves, using the same motor points as in the last
experiment, and fasten ; see that slider touches flat side of
checking post ; then close key G and see that no current
passes the milammeter. Now proceed as in Experiment
XVIII until a position of the slider is found giving a direct
current sufficient to cause a kathodic closing sensation but
no contraction. With slider in this position and key G
open, find position of secondary coil such that a tetanizing
current will provoke a small contraction. Observe which
is the more active pole, and rock the commutator so
that anode of the direct current will be brought to that
pole. With the apparatus as now placed, the influence
of the direct current can be observed in two places, where
anode is applied at more active pole, and where kathode is
applied at less actii'e pole.

Close key 0 and start the vibrator. When the con-
traction produced has continued about 5 seconds, close
ke}' G and thus introduce a weak direct current. Observe
lhe effect at each pole, as regards the sensation and the
contraction due to the induction shocks. The effect of the
anode of the direct current to lessen irritability should be
more marked than the effect of the kathode to increase it.
Leave the direct current flowing for 5 seconds, then open
key G and notice the after eft'ects, especially at the pole
at which the anode has been acting. As soon as the after

EFFECT OF CURRENT ON IRRITABILITY OF NERVES. 99

effects have been observed, open key 0 to stop the excita-
tion, and wait 5 minutes for the effects to pass oft".

Rock the commutator, reversing the direct current, and
study in the same manner the other case : kathode applied
at more actirc pole and anode at less aetk'e pole.

The experiment is to be performed upon each student,
each writing in his notes the effects observed on himself.

lOO.

EXPKRIMF.NT XIX.

KFFECT OF CURRENT ON IRRITACIEITY OE NERVES. I CI

EXPERIMENT XIX.

CURRENTS OF REST AND ACTION. IO3

EXPERBIEXT XX.

Currents of Rest and Currents of Action.

a. Cur rent of Rest defected by Rlicosco[^ic Frog Prep-

aration.

Apparatus. — ]\Iount on short stand a brass L rod, and
fasten a muscle clamp, with the jaws horizontal, to the
short arm of the rod. Connect a dry cell and a key with
an induction apparatus so as -to give tetanizing excitations,
and connect a pair of copper electrodes with the secondary
coil.

Experiment. — Prepare (A) a nerve-muscle preparation,
(B) a nerve-leg preparation (a rheoscopic frog prepar-
ation), and (C) a piece of thigh muscle having one unin-
jured surface and one surface cut squarely across the
fibers. To prevent drying, put between layers of filter paper
moistened with physiological salt solution. Place knee
joint of B in clamp with leg pointing upward and nerve
hanging; below. Avoid clamping the nerve. Place C on
a glass slide ; make a fresh cross section on C ; then hold-
ing glass slide in hand, bring C up beneath B in such
a wav that the nerve of B shall fall suddenly across cut
surface and normal surface of C. B should contract,
because the injured part of the muscle C is undergoing
katabolic change and is consequently negative as compared
with the normal surface. The nerve closes the circuit and
is stimulated by the so-called "Current of rest," the "De-
marcation current."

b. Current of Action detected by Rheoscopic Frog Prep-

aration.

Mount the glass side in holder on L rod, and the rod
on a stand. Place A upon the slide, and clamp the L rod
so that the nerve of B lies lengthwise upon the muscle of A.
Stimulate nerve of A with tetanizing current of medium
streno-th. Both muscles should be tetanized.

I04 EXPERIMENT XX.

To find if currents spreading' from electrodes have
caused B to contract, ligature nerve of A tightly at its
middle, with a moist ligature, and then stimulate above
ligature. Xo contraction of A or B occurs. The ligature
would not block an electric current, but by breaking the
continuity of the nerve fibers, it efifectually blocks a nerve
impulse. It follows that B must have been stimulated by
the "Current of action" the "Negative variation Current,"
of the muscle A. When A contracts, a wave of con-
traction passes over it, and at a given instant, some parts
are undergoing greater katabolic change than others,
and hence are electrically negative as compared with the
less active parts. The nerve completes the circuit and is
stimulated. Put preparation A and B in moist filter paper,
to be used in demonstration to follow, in which the currents
of rest and action of muscle, nerve and heart are detected
with the aid of a galvanometer and a capillary electrometer.

CURRENTS or" REST AND ACTION. 105

Io6 EXPERIMENT XX.

THE REFLEX FROG. I07

EXPERIMENT XXL

The Reflex Frog.

The value of this experiment is great if it be properly
interpreted. Through it we have the best physiological
evidence of the method of spread of reflex processes in the
spinal cord. When stud}'ing the movements which result
from excitation, one should try to recall the finer anatomy
of the spinal cord, the longitudinal paths of conduction, the
method of communication between the posterior and anter-
ior roots, and the way impulses pass from side to side of
the cord.

a. Time of Recovery from Shock.

Pith a frog's brain and plug cavity of skull with as little
loss of blood as possible. N^ote the time at which this is
done. Place the frog on a plate, back upwards, and with
the legs stretched out at full length, note the time required
for recovery from the shock, as shown by the drawing
up of the legs. Xow cover with moist paper and leave
for half an hour. At the end of this time observe the
frog's position. If cerebrum and cerebellum have been
completely destroyed, it will lie with nose against plate ; if
turned on back it will not turn over ; if thrown in water it
will not try to swim ; if stimulated it will move legs but not
jump; the power to perform highly coordinated movements
is absent.

h. Spread of Reflexes.

Clamp nickled L rod on stand, and put frog-hook on
short arm of L. Suspend the frog from hook passed
through nose. Gently irritate flank with a needle and ob-
serve local twitching of muscles : excite more strongly and
notice spread of reflexes to limbs. Pinch a toe gently and
then more strongly (do not crush) and observe and note the

I08 EXPERIMENT XXI.

order in which the different parts of the leg and of the body
respond to the excitation.

c. Are Reflexes Purposeful?

Place beneath frog a battery jar two-thirds full of water,
so that by lifting the jar the body can be washed. Caution.
— In this and the following tests requiring the use of acid,
be sure to wash it off after each test. Put a bit of
paper i mm. square, wet in io% acetic acid on right flank,
left flank, median line of lower back, and on various parts
of leg, and state in your notes the results. Hold right foot
lightly and put paper on the right flank. Reflex should
appear in right leg, and later in the left leg. The word
purposeful in the question heading this section is not used
in the sense of well adapted to the needs of the animal, but
directed by volition to accomplish a definite object. In
short, do the movements of the frog justify the view that
the spinal cord is the seat of intelligence?

d. Reflex Time.

Immerse tip of longest toe in o.i% H^SO^ up to a
definite mark, noting number of seconds between immersion
and withdrawal. Repeat five times with each foot and
report average for each. Immerse to the same mark each
time, as the distance affected influences the result. Wash
off acid after each test. Where is the time yrobably lost?
Does the experiment favor the "neurone theory," or the
theory of a continuous nervous network ?

e. Spasm of Muscles -t'crsus Coordinated Mo-vements.

Ai'TARATus. — Arrange induction coil to give tetanizing
excitations. Connect a pair of copper electrodes with the
secondary coil.

ExPEKiMENT.— Remove frog from hook. Open abdo-
men by cutting away whole of anterior wall ; remove vicera
without injuring the sciatic plexuses behind them. When
the flow of blood has ceased, cut through the middle of
the sciatic plexus on one side, and free the nerves so that
they can be laid across a pair of electrodes. Put frog on

THE REFLEX FROG. 109

hook. Appl}^ electrodes first to the peripheral, and after,
to the central cut ends of the nerves of the plexus, taking
care to use the weakest effective tetanizing current and to
avoid touching the electrodes to anything except the nerves.
Explain how the resulting movements differ?

no

F,XPERIM(;NT XXI.

THK RKFtEX FROG. m

EXPERIMENT XXI.

RCACTIOX TIME TO SOUND.

113

EXPERIMENT XXII.

Reaction Time to Sound.

Apparatus. — Blacken drum and fasten it at highest
point on kymograph. Arrange to turn it by hand. Fasten
the heavier muscle lever, with supporting screw down, on
long stand at such height that it will write 2 cm. from
bottom of drum. Put L rod on stand above lever ; put
elastic band on rod ; and connect band with lever l^y a
thread put through second hole, so that band will be slightly
stretched. Fasten one end of a thread to the strip of wood
provided, by passing thread through hole nearest the end
and back through other hole, and tieing it so that thread
will not slip. Fasten other end of thread to third hole in
lever, leaving thread of such length that the end of the
piece of wood to which thread is fastened will be so near
the table that when it is pressed on by finger the lever
will move about 4 mm. Bring writing point of lever to
dirum. Mount fork on short stand, and place this stand
so that fork will write the time one centimeter below lever

and in same vertical line.

Experiment. — The subject
is to put finger on strip of wood
and depress it bo that the lever
is pulled down and the wood
rests on table ; ( see that the
thread is veriical). He is to
remove finger as soon as he can
after hearing sound of fork. He
nmst not react to soimd of the
moving drum, and to give quick
response must have in mind the
sound of fork. The experi-
menter must put yoke on fork ;
tell subject to close eyes: say
"ready," and about a second
later whirl the drum ; then pull yoke off fork and stop drum
as soon as subject is seen to respond.

•v:

s^

Kig. 25. Apparatus for record-
ing reaction time for sound. A.
rubber baud; B, lever; C, tuning
fork; D, strip of wood, which is
to be pressed by finger against
table.

114 EXPERIMENT XXII.

Rehearse the experiment two or three times without
the pointers touching the drum. Then move drum up to
pointers and see that they write well. Mark the relative
position of the pointers on the drum by moving them. If
the kymograph or either stand is moved at any time, the
relative position of the writing points must be again marked.
Do not fail to mount part of curve showing the position of
writing points along with the rest. Take lo reaction times
with each student as subject, moving drum down after each
experiment.

Reading of Curves. — Draw perpendicular with., triangle
from point where lever began to move, through the cor-
responding tuning-fork curve. Count the number of waves,
starting with the crest of the first and estimating in tenths
the value of any fraction of a wave at the end. State time
in hundredths of a second. Give in notes result of the
separate observations and the average of lo observations.
Throw out only such observations as were known to be
faulty at the time they were made. Account for variations.

Ordinary reaction time to sound is 0.15 — 0.20 second;
to a tovich on the skin, 0.145 second; and to an electric
flash 0.195 second.

RKACTION TiMIi; TO SOUND.

115

ii5

j:;XPr;Ri.Mi:NT xxti.

Tilt; KXICK-JERK.

117

EXPERIMENT XXIII.

The Knee-jerk as Modified by Reenforcing and Inhibit-
ing Influences.

If a blow be struck on the ligamentum patellae when the
lower leg" is in a position that puts the ligament under slight

Kig. 26. Diagram of nervous patlis followed by the nerve impulses causing
the knee-jerk and its reenforcemeuts. A, hammer placed to strike ligamentum
patellse; B, quadriceps muscle; C, posterior spinal nerve root; D, motor cell in
anterior horn of gray matter of lumbar cord; E, anterior spinal nerve root ;F,
sensory nerve from other leg; G, comniisural cell; H, descending path from leg
area in cerebral cautex; I, descemling path from arm area in cerebral cautcx;
J, motor nerve to arm.

ii8

EXPEKIMENT XXIII.

tension, a sudden twitch is transmitted to the vastus internus
and crureus divisions of the quadriceps extensor muscle.
The result is a sudden contraction of these muscles and a
sudden forward swing of the leg.

Two explanations of the sudden contraction of the
muscle are offered; viz: (i) The knee-jerk is a reflex
act. The twitch acts as a mechanical stimulus to the sen-
sory nerve ends in the muscle and its tendon, and causes
a reflex contraction of the muscle, which causes the foot

Kig. 27. Method of supporting thigh and foot and of recording the swing of
the lower leg in the knee-jerk experiment. A, support under thigh; B, pulley;
C, cross shape<l writing needle; D, rubber band, twisted so as to keep point of

ipe<l writing
needle against drum; E, knee-jerk hammer

to swing if it is free to move. The anterior horn cells taking
part in this act are in the leg areas of the third and fourth
lumbar segments of the cord. The response of these cells
to the sensory stimulus from the extensor muscles, is either
reen forced or inhibited by other impulses reaching the
anterior horn cells a short time before the impulses from
the leg. (2) The knee-ierk is the result of the direct
mechanical stimulation of the muscle. The greater the
tension the better the muscle responds to the blow on the
tendon. The anterior horn cells are always during waking

THE KNEE-JERK. I 1 9

hours sending tonus impulses to the muscles which keep
them under more or less tension, and these impulses are
increased bv reenforcing and decreased by inhibiting in-
fluences. It will be here assumed that the former explana-
^tion is correct.

Appakatus and Position oe Subject. — The subject is
to lie on his left side with his head on a pillow, his thigh
on a support, and his foot in a swing. The position must
be perfectly comfortable, so that he could go to sleep.
Adjust the support (A) tmder the thigh so that the lower
leg will swing freely. The subject must be in such a posi-
tion that the cord suspending the swing is vertical when
the leg is at rest ; and throughout the work he must lie
quietly and relaxed with eyes closed except when told to
do otherwise. Connect the back of the swing by thread
passing round pulley (B) to a cross shaped writing needle
(C), so that the rubber band (D) supporting the latter is
under a slight tension and the needle free to move. Adjust
the hammer (£) so that when it hangs vertically, the mid-
dle of the striking face will just touch the skin over the
middle of the ligamentum patellae, and so that the blow
will be struck at riglit angles to the ligament. Make this
adjiistiiieiit with great care, then clamp the rod supporting
the hammer.

Experiment. — Four students work together, each taking
his turn as subject, experimenter, assistant, and clerk. The
experimenter uses the hammer ; the assistant sits near the
head of the subject and applies the sensory or psychic
stimuli when signaled by the experimenter ; the clerk looks
after the drum, and keeps record of any reenforcing or
inhibiting stimuli, marking on the drum, i, 2, 3, etc., to cor-
respond to his notes. During the entire experiment the
subject must be completely relaxed and the room perfectly
quiet. Success depends entirely on the contrast between
repose and action of the central nervous system. If those
who make the experiment are not quiet and annoy or excite
the subject, except when a special efifect is desired, the
whole experiment fails.

I20 EXPERIMENT XXIII.

a. Minimal Blow Xcccssary to Excite.

Adjust arm supporting catch for hammer so that index
points at io° ; put hammer on catch, release hammer and let
it strike the tendon, catching it as it rebounds, so that a
second blow shall not be struck. Turn drum 5 mm. and
continue, raising and lowering arm supporting hammer
until the least blow is found which will cause a knee-jerk.
Make note of the position of hammer for this minimal blow.

b. Record of Normal Knee-jerk.

Find position of hammer that will give a knee-jerk
whose record on drum is about 2 cm. high. Make note of
position of hammer. Start drum at 2 or 3 mm. per second
and record a series of 20 normal knee-jerks, giving the
blows rythmically at such a rate that the foot has time to
come to rest after each jerk. Observe that even when sub-
ject is relaxed and the room quiet, the knee-jerks vary in
height, in other words, that the irritability of the reflex
mechanisms is changing.

c. Motor Recnforcement.

Let the subject clench his hand at the instant a com-
mand is given him, the hammer being released at varying
intervals. If the blow on the knee occurs at the exact
instant the command to clench is given, or within 0.4 second
after the command, the knee-jerk is gi"eater than normal,
i. e., reenforced, if the blow is struck between 0.4 and 1.7
seconds after the command, the response is lessened, i. e.,
inhibited. If the blow comes still later, the clench has no
effect. Record 10 or more normal responses, and when
they are of about the same height, try the effect of clench-
ing, the clerk making a mark on drum to indicate the jerks
with which a clench was given, then record another series
of normal jerks. The explanation of the effect of the
clench is that when the motor cells of the arm area of the
cerebral cortex act, the motor cells of the leg area of the
cerebral cortex are excited through association fibers, and
im]5ulses from the cells of the leg area of the cortex spread
to the anterior horn cells of the leg area of the cord. If the

THE KNEE-JERK. 121

impulses coming from the brain reach the lumbar region
of the cord before the sensory impulses from the leg, they
so alter the condition of the anterior horn cells that the
reflex response to the blow is altered. Sudden discharge
of voluntary impulses to any other muscles, e. g., clenching
the jaw, or even winking, will also cause a reenforcement
or inhibition.

d. — Reenforcement by Sensory Stimuli.

Pulling a hair, tickling face with a camel's hair brush,
an unexpected sound or odor, will cause a reenforcement.
To show this, record lo or more normal jerks by a series of
rhythmical strokes, and when the jerks are of about equal
height, test several sensory effects, marking on drum the
time such stimuli are given.

e. Psyehic Recnforeemcnt.

With subject as quiet as possible, eyes closed, room per-
fectly still, record a series of lo or more normal jerks, and
while the record is being taken, test the effect ( i ) of speak-
ing to subject. (2) of asking him to multiply two numbers
given him, (3) let him think of some stirring poem, etc.
The clerk should note all these occurrences with care, and
also the eft'ect of sounds produced in neighboring rooms or
out of doors, the entrance of any one into the room, -and all
external influences that are able to excite the subject in
the least degree. The susceptibility to such influences
varies greatly with the subject. The student who was the
subject of the experiment, is to have the record.

122 EXPERIMENT XXIII.

THE KNEK-JERK. 1 23

124

EXPERIMENT XXni.

CONDITIONS DETERMINING BLOOD PRESSURE.

EXPERIMENT XXIV.

Conditions Determining the Blood Pressure, and the
Output of the Ventricle.

porter's artificial CIRCULATION APPARATUS.

The basin supplying and receiving the water represents
the left auricle. The bulb which pumps the water represents
the left ventricle. The valves at the inlet and outlet of the
bulb represent the mitral and aortic valves. The piece of
ratan and the side tube controlled by clamp represent the
capillaries and the variable resistance of the small arteries.
The tubes between the aortic valve and the resistance repre-
sent the arteries. The tubes between the resistance and
the basin represent the veins. Two manometers connected
with arteries and veins permit a study of pressures under
varying conditions. A tube connects the ventricle with a
tambour, b}' means of which changes in pressure in the
ventricle can be observed. A tambour can be placed over
the artery and enables the pulse to be recorded.

Make a diagram showing these various parts of the
apparatus. After making the diagram, see that the clamp
on the side tube is open and then fill the tubes with water,
b\- pumping while holding the right hand end of the appar-
atus up at an angle of 45'. Always pump b}' compressing
the bulb quickly and instantly removing the pressure, re-
peating rhythmically every tivo seconds. Compress the
bulb only by means of the lever placed above it, and see
that the rod limiting the movement of the lever is in its
clamp, with the longer end upward. Using the apparatus
in this way, prepare to demonstrate to the instructor the
points enumerated below before proceeding to the second
])art of the experiment.

126 EXPERIMENT XXIV.

PART I.

I. — The fluid takes path of least resistance, nearly all
of it going- through the open side tube and but little through
the ratan.

2. — Only a part of the fluid pumped escapes into the
basin during systole.

3. — The part held back dilates the arteries and escapes
during diastole.

4. — The part of the artery nearest the heart expands first.

5. — Finger placed on ventricle tambour feels a sudden
rise of pressure followed by a sudden fall of pressure.

6. — Arterial manometer shows rise of pressure later
than ventricle tamborrr.

7. — The meixui'v oscillates after each beat. l:)ecause of
its own inertia.

(7. Effect of Chauii^ini!:^ Peripheral Resistance.

^^'ithout changing the rate or manner of pumping, grad-
ually increase the peripheral resistance by slowly screwing
up the pressirre clamp on side tube; observe, i. — Increase
of arterial pi"essure, indicated by arterial manometer, and
visible changes in size of arteries ; also decrease of venous
pressure indicated by venous manometer. 2. — Decrease of
outflow, indicated by the size and character of the stream
flowing into the basin from veins. 3. — Increased work for
heart as felt by the hand and ventricle tambour.

Caution. — Keep watch of the manometer as the clamp
is closed, and avoid forcing the mercury out of the tube.

b. Effect of Chaiii:;i)ig Rate of Heart Beat.

With clamp on side tube open wide, ( small peripheral
resistance) observe the following: i. — Slow rate, (once
in 3 sec). The fluid escapes into the basin completely dur-
ing the diastole. (The flow is intermittent.) 2. — Medium
rate, (once in i sec). The fluid pum])ed does not all
escape into the basin during diastole. (The flow is remit-
tant. 3. — Fast rate, (three times per sec). Marked

CONDITIONS DETERMINING BLOOD PRESSURE. I 27

accumulation of fluid in the arteries causing distension
of walls, and continuous outflow approaching- constancy.
The energy stored in the walls of the elastic arteries during
systole drives the fluid on during diastole. The pressure,
as shown by manometers, is never high when side tube is
open, no matter how rapid the beat.

c. Effect of Changing flic J^ohnuc Pumped per Beat.

Remove the rod limiting the pressure of lever on bulb,
and replace it with its shorter end upward, and observe the
efifect on the pressure and the outflow, pumping at rate of
once in two seconds. Demonstrate above points to instruc-
tor, before proceeding further.

PART II.

d. Record of Pulse from the Artificial Circulation Appar-

atus.

The method of air transmission devised by Marey, is
employed to record a great variety of physiological move-
ments. By this method, two little drums covered with
rubber membrane are connected together b)^ tubing. A
plate of metal resting on the membrane of one of the drums
(the recording tambour. Fig. 28), is connected with a light
lever, and when air is driven out of or enters the other
drum (the receiving tambour), by movements imparted to
the membrane covering it, the lever rises or falls. There
is a T tube at one part of the tubing connecting the drums,
and this supplies a side opening by which air can enter
or escape when the tambours are not in use. This opening
is controlled by a pinch-cock. The level of the lever can
be adjusted by placing the support of its axis at a suitable
angle.

Caution. ^Do not apply pinch-cock, excepting when
the tambours are to be used. See that the lever of the
recording tambour is horizontal just before a record is to
be taken, and never let the membrane of the recording tam-
bour be greatly stretched.

Adjust a receiving tambour to wall of artery, and con-

10

I2J

EXPERIAIENT XXIV.

nect it to a recording tambour. Clamp the tube leading to
arterial manometer. Replace rod limiting pressure of lever

on bulb, with its longer
c . end upward ; then

pump in the manner
directed at the rate of
once in two seconds.

i'lg. 28. Recording tambour. A, tambour; ...

B, aluminum plate, with bell-and-socket joint No pulsC IS glVCll With

for pin acting on lever; C, lever with celluloid . , ,

writing point; D, support of lever. Side tubC, representing

small arteries, wide
open. Gradually increase the peripheral resistance, and
observe the resulting distension of large artery and pulsa-
tion of tambour. Several beats will be required to fill the
artery before the tambour will respond. Record on drum.
By careful adjustment of peripheral resistance and regular
and uniform pumping, a pulse can be recorded that is a
fair imitation of a normal pulse curve from man. Record
curves as follows :

I. — Imitate a normal pulse, and dicrotic pulse, i. e., the
pulse which comes with a low arterial pressure.

2. — Effect of slight
A B c changes in peripheral

resistance. Record ten

or more normal beats ;

then make a slight in-

Fig. 29. Sphygmogram of a normal pulse CrcaSC HI the rCSlStaUCC
and a dicrotic pulse. A, crest of primary ^^^^ j^^rk OU drUm the
wave; B, dicrotic notch; C, dicrotic wave.

time of the change ;
after ten or more beats with this resistance, return to the
normal, again marking on drum.

In a similar manner make a curve showing effect of
decrease of pressure.

3. — Effect of changing rate of beat. Record curves
with the following rates of beat : I in 2 seconds, i in 3 sec-
onds, I in I second. 2 in i second, 3 in i second. In each
instance the curve should show the effect of changing the
rate.

4. — Effect of changing the volume pumped per beat.
Show effect of increasing and of decreasing the volume per

CONDITIONS DETERMINING BLOOD PRESSURE. 1 29

beat, always marking on drum the time the change is made.
Notes. — Describe the form of the normal pulse wave
which you obtained, and state in what respects the form
of the wave is changed by vaso-constriction, vaso-dilation.
increased heart rate, and increased pulse volume.

c. Coinparisoii of Arterial and J'enfriciilar Pulse Curves.

Mount a special tambour on rod so that the button will
rest against ventricle tambour. Record ventricular and
arterial pulses together. Note difference of form and delay
of the arterial pulse.

part III.

f. Effect of Lesions of Heart I'^alves.

Failure of a valve to close its orifice perfectly is called
insufficiency. Abnormal narrowing of its aperture is called
stenosis. These defects in the heart valves are usuallv
accompanied by dilation of the cavities and hypertrophy of
the heart muscle, which is known as compensation. These
three conditons can be imitated in a way in the artificial
circulation apparatus ; insufficiency and stenosis by the use
of suitable valves, which will be provided, and compensation
by reversing the rod which limits compression of the bulb,
thus permitting greater outflow at a stroke.

Arrange to record ventricular and arterial pulse curves,
and then, with the same peripheral resistan^^e as used for
imitation of a normal pulse, and pumping at the rate of
once in two seconds, record curves to show effects of the
following lesions, alone and with compensations :

I. — Aortic Insutficleney. The ventricular pulse is about
normal, but the arterial pulse shows a sudden upstroke and
a sudden fall.

2. — Aortic stenosis. The ventricular pressure is ab-
normally high and the arterial pressure is low. even with
compensation.

3. — Mitral Insufficiency. Pressure low in both curves.

4. — Mitral stenosis. Pressure very low in both curves.

Explain the results in each case, and state in which

130 EXPERIMENT XXIV.

cases the compensation made the curve more nearly normal,
and why.

It must be borne in mind that these lesions in the living
subject are accompanied by other changes, so that the
results are of value only as indicating fundamental relations,
which here are separated from complications usually present.

Leave apparatus in order for normal action.

CONDITIONS DETERMINING BLOOD PRESSURE. I^I

132 i;xpi;rime;nt xxiv.

CIKCULATIOX AND RESPIRATION OF MAMMAL.

'33

EXPERIMENT XXV.

Circulation and Respiration of the Mammal.

Ex])erin-ients on these subjects will fill two afternoons,
the apparatus and general methods beiiig the same for both
da^•s. The students will work in groups of four, and the
parts of the work to be done by each student is shown in
the follo\\ing schedule. The number of the student as
given in the schedule will be assigned by lot.

Schedule of Work.

First Day
Experiment 25

Student i

Student 2

Student 3

Student 4

Right carotid
and vagus

Operate

Assist

Etherize

Apparatus

I^eft carotid
and vagns

Apparatus

Operate

Assist

Etherize
Assist

Sciatic

Etherize

Apparatus

Operate

Tracheotomy
and open chest

Assist

Etherize

Apparatus

Operate

Account for
apparatus

Account for
apparatus

Second Day
Experiment 26

Right carotid
and depressor

Assist

Etherize

Apparatus

Operate

Left carotid
and depressor

Etherize

Apparatus ' Operate

Assist

Tracheotomy
and open chest

Apparatus

Operate Assist

Etherize

Phrenic and
peristalsis

Operate

Assist ' Make nerve
leg pre part' n

Apparatus

Account for
apparatus

Account for

apparatus

Success in the experiments, recjuires that the apparatus
shall be thoroughly understood before the work is begun.

134 EXPERIMENT XXV.

Students assigned to this work will be given an opportunity
to study the apparatus, and be quizzed on these notes, the
latter part of the preceding afternoon.

Apparatus. — The arrangement of the apparatus is to
be seen in Fig. 30. The following list of apparatus and
instruments will be required, and everything must be at
hand before the work is begun.

Apparatus to be Pnrnished by Laboratory.

Animal-board with head-holder.

Manometer outfit.

Artificial respiration outfit.

Bottle of ether.

Bulb and cannulae for artery.

Cannula for trachea.

Two burette clamps.

Three clamps for stand.

Screw clamp for trachea.

Four screw clamps for rubber tubing.

Four cords for animal board.

Two cords with hooks.

Etherizing cone.

Two cloth covers.

Dish for sodium chloride solution.

Dropper.

Small bulldog forceps.

Large bulldog forceps.

Jar for sodium sulphate.

Battery jar.

Ligatures, fine.

Ligatures, coarse.

Water manometer.

Aneurism needle.

Pinch cock.

Rod, nickled.

Rubber tube with glass T.

Scalpel.

Sponge.

Two small stands.

CIRCULATION AND RESPIRATION OF MAMMAL.

U5

Receiving" tambour.
Recording" tambour.
Two towels.
Silk thread and weight.
Stimulating electrodes.
Time signal.

■rlpporafiis to be Fiiniislied by tJic Four Students assigned
to the zvork.

One dry cell.

Induction coil.

Kymograph and two drums.

Mercury key.

Two plates.

Brush for salt solution.

Fine and strong scissors.

Fine and strong forceps.

Five wires.

Cabinet maker's clamp.

Fig. 30. Scheme of apparatus for studying the blood pressure of a mammal.
A, tambour lever; B, pointer of a manometer float; C, time signal; D, short cir-
cuit key; E, mercury float; F, electrodes; H, bicycle pump; I, anticoagulation
fluid pressure bottle; J, manometer communicating with pressure bottle, K,
bulb and cannula; Iv, minimum valve; M, maximum %'alve; i, 2, 3, cocks; 4, 5,
6, clamps.

136 EXPERIMENT XXV.

DIRECTIONS TO STUDENT CARING FOR APPARATUS.

Connect time signal (C) and an electric light switch in
the clock circuit. Place the induction apparatus behind the
manometer outfit, and put a dry cell and a key in the
primary circuit, connecting them so as to give a tetan-
izing current. Connect secondary coil with shorli-circuit
key (D) on top of manometer board. Fasten a pair of
electrodes (F) to key (D), with wires leading off in
front of manometer. Start vibrator, open short circuit key,
and test current with tongue. A current of medium strength
will suffice. See that writing points of manometer (B) and
key (D) write in same vertical line.

Now with cock i and clamp 5 closed, raise pressure to
90 mm. in bottle (7) containing anticoagulation fluid, by
using bicycle pump. Pump very carefully, or the mercury
will be forced out of manometer. Next raise bulb K, until
it and its tube are vertical ; open clamp 6 ; then gradually
open clamp 5. and let fluid rise in tube and fill bulb; finallv
close clamp 5. Now lower bulb until on a level with the
mercury of the recording manometer. Open cock i, and
as soon as the float has taken its new position, close cock i,
and put bulb in such a position that any drip will be caught
in dish provided for the purpose. Place point of time
signal (C) just behind and on a level with the pointer of
the manometer float (B). The time record will in this
position give a base line from which all pressures are to be
read. Notice that the mercury in the two arms of the
manometer is not at the same level. This is due to the
weight of the anticoagulation fluid on one side of the U.

I)y means of pump, raise the pressure in the bottle of
anticoagulation fluid until the mercury in the manometer
connected with the bottle stands at 90 mm. Pump with
care. Pinch ofif rubber tube at opening of bulb ; open clamp
5; and then graditally open cock i, until the mercury in the
recording manometer rises to 50 mm. Close i and 5. The
true pressure is twice the amount recorded, for the mercury
falls on one side of the tube as it rises on the other. The
object of raising the pressure, is to limit the amount of

CIRCULATION AND RESPIRATION OP MAMMAL. 137

blood which will leave the artery when it is connected with
the manometer.

The apparatus must be ready to use the instant that the
operation is completed. Have two drums blackened, and
mark the position of the writing points on the drum which
is to be used first.

During the taking of the records the man in charge of
the apparatus must s'art and stop the drum ; must mark the
position of the writing points on the drum before each
curve ; must give the stimulations by depressing the short
circuit key, and see that the drum runs for at least 10
seconds before and 15 seconds after each test; and must
label each record with his name and the number of the
curve before giving it to the assistant to fix.

Directions to Assistant.

It is the business of the assistant to see that the instru-
ments, ligatures, and cannulae are in order, and are at the
hand of the operator throughout the operation and the
experiment. While the animal is being etherized, fill the
animal board with water at 45° C. ; heat some salt solution
in a dish provided for the purpose, put a sponge in it, and
place it on the operating table ; also put two cannulae of
dififerent sizes in a dish of anticoagulation fluid. During
the operation be ready to sponge the wound, to pass needed
instruments to the operator, and to tie the ligatures when
required. During the experiment, when the records are
being taken, blacken the drums. There should always be
a drum ready for use.

Anaesthesia.

Anaesthesia comes on in three stages : ( i ) imperfect
consciousness, (2) excitement, (3) complete anaesthesia or
narcosis. These stages show the following peculiarities,
which must be kept in mind in administering ether. (See
Cushny 's Pharmacology. )

Stack I. — Loss of consciousness begins toward close.
Struggling because of dislike of drug ; respiration irregular

138 EXPERIMENT XXV.

from irritation of mucous membrane, salivation for same
reason ; pupil dilated.

Stage II. — Lessening of reflexes toward end ; struggling
due to nervous excitement caused by drug ; respiration
heavy with pauses and gasps ; pupil dilated.

Stage III. — The danger period. Unconsciousness ;
respiration slow and shallow, often snoring ; pulse slow and
feeble ; pupil small until danger point is reached, when it
dilates ; corneal and other reflexes are lost.

Rabbits differ from men, dogs, and cats, in that con-
vulsive respirations immediately precede death in the third
stage.

Directions to Anaesthetizer.

See that there is no gas flame in the same part of the
room. Ether vapor travels far and is exceedingly inflam-
mable.

Let the student who is to operate, hold the four legs of
the rabbit between the fingers of the left hand, and hold
the ears between the second and third fingers, and the nose
between the thumb and index finger of the right hand. He
should take care not to use unnecessary force, there is no
need of hurting the animal.

The anaesthetizer puts some ether on the gauze of the
cone, and places the cone over the animal's mouth and
nose. The ether bottle is to be kept corked when not in
use. It is well to place a towel beneath the head, and bring
it up to the sides of the cone. Ether vapor is heavy and
falls, hence the towel prevents waste and facilitates use.
Do not "force the ether," i. e., let the animal have plenty of
air to breathe. Remember that etherization is not asphyxia-
tion. The man giving the ether niiisf think of nothing else.
If the animal dies through his fault, he must pay for another,
( 50 cents ) . Watch especially the respiration, and when in
floubt, pinch foot, to see if leg reflex is present ; also note
the corneal reflex, which consists in a closing of the lid
when the cornea is lightly touched. When well under, the
animal should breathe regularly and quietly. If the respir-
ation becomes irregular, with pauses, and the reflexes are

CIRCULATION A-\D RICSriRATlON OF MAMMAL.

139

present, the animal is "coming out" and needs more ether.
If the respiration stops, or becomes convulsive, immediately
test the reflexes, and if the reflexes are absent and the pupil
is dilated, stop the ether, start artificial respiration, and call
instructor. The amount of ether should be lessened when
the third stage is reached, and only a little given at intervals,
to keep the animal asleep. In case coarse rales caused by

Operation for Isolation of Carotid and Vagus.

M. stylohyoideus major.
N. liypoglossal.

Superior laryngeal.

Descendens noni.

2 roots of depressor nerve.

Vagus.

Depressor.

Sympathetic.

Carotid artery.

Trachea.

M. sterno-mastoid

Fig. 31. Dissection of nerves of left side of neck of rabbit. The trachea has
been pulled to the right and the nerves to the left.

collection of mucus are heard, swab out the throat with
absorbent cotton on large forceps.

When the animal is sufficiently under to have stopped
struggling, fasten it on animal-board, by placing a noose
about each leg above the hock, and tying the cords to the
cleats on the sides of the animal-board. Put head in head-
holder. The instructor will show the method of application.

As soon as the animal's head has been placed in the
head-holder, remove the hair from front of throat for a

140 EXPERIMENT XXV.

space 1.5 in. wide, and from top of thyroid cartilage to
sternum. Put the hair in a battery jar.

Sponge ofif the loose hairs, and as soon as the reflexes
have ceased make a median incision with scalpel through
skin, from top of thyroid cartilage to near top of sternum.
Avoid veins at lower part of incision. Cut through the
platysma muscle in the median line. Tie off any large
vessels that have been cut, and have assistant sponge off
blood with warm salt solution. Separate sterno-mastoid
from sterno-hyoid ; this brings the sheath of carotid artery
into view. Close to the artery are the veins and nerves.
From this time on it will probably be bettei to tear away the
fascia longitudinally with the blunt end of an aneurism nee-
dle or similar instrument, rather than to use a knife. The
descendens noni lies superficially ; the vagus lies behind the
carotid ; to the inside of the vagus are the sympathetic and
depressor nerves. Isolate the vagus, the largest of these,
for a distance of an inch or more and pass a thread under
it, tying the ends together so that the nerve can be lifted
by the loop. Avoid pinching, stretching, or otherwise
injuring the nerve.

Prepare the dipper part of carotid for insertion of can-
nula, by carefully separating it from its sheath for a dis-
tance of at least an inch. Pass
two ligatures under it, and tie
one of them tightly at the
upper end of the exposed part
of the artery ; place the other
so that it can be used at short
Fig. 32. MeUnod of inserting cann- noticc to tie the Cannula in

ula into carotid artery. A, ligatnre .-.Ippp A nnh^ a nair nf hull

tied to the distal side of the place Pi'iCe. ^ppi} a pair OI DUU-

where the cannula is to be inserted; rlno- frirrpnc 'tn, In-nrAr i-.at-f r\i

B. cannula; C, forceps; D, loop of ^^^^ lOrCCps tO lOWCr part Ot

ligature placed around artery, to the artcrv tO shut off blood. There
proximal side of point where can- -

nuia is to be inserted; E, bull-dog are two mcthods of inserting

forceps. . _ ^

a cannula, viz: t. Grasp with
fine pointed forceps as small a part of the arterial wall as
you can hold securely, and with fine pointed scissors make
a diagonal slit in the direction of the heart and through
about half the width of the artery. Still holding the flap.

CIRCULATION AND RESPIRATION OF MAMMAL. ,141

insert the cannula which the assistant has just taken from
the dish of Na^SO^, and let him tie it firmly with the liga-
ture which has been placed there for the purpose. 2. Place
the index finger of the left hand beneath the artery ; with
sharp, fine pointed scissors make a cut in the wall of the ar-
tery ; and without withdrawing the finger insert the cannula.
It is of advantage to put the cannula into the upper part of
the artery, so that the lower part can be used in case the
cannula has to be put in a second time. Fill cannula with
anticoagulation fluid, by means of a fine pipette, the instant
the cannula is tied in. Now without losing time, place the
animal-board so that the cannula can be readily connected
with the bulb on the manometer outfit. Make sure that
the cannula, bulb and connecting tube, are full of anti-
coagulation fluid, and then connect them. Fasten the tube
of the bulb in a burette clamp, in the position which will
bring the least possible strain on the artery.

a. Measure of the Blood Pressure in the Carotid.

As soon as the cannula has been fastened to bulb, remove
bull-dog forceps, and make sure that there is no leak be-
tween the cannula and the artery. The blood should be
seen to enter the cannula and dififuse into the fluid in the
bulb. If all is right, gradually open stop-cock i. Then
start drum at rate of 5 mm. per second. The manometer
float should rise, and the height of arterial pressure be
recorded. Let the drum run until 25-30 cm. have been
recorded. This record is to be divided later among the
students, the operator taking the first part of the curve.
Notice that curve shows larger waves of pressure due to
respiration, and upon these, smaller waves caused by heart
beats. The small waves do not show the amount of blood
expelled by heart, but the efl^ect of corresponding pressure
changes in the artery, on the mercury in the manometer.

b. Maximal and Minima! Blood Pressures.

Observe that the valve L. controlled by cock 2. per-
mits fluid to pass only from the manometer, and that the
valve M, controlled by cock 3, permits it to pass only

142 EXPERIMENT XXV.

toward the manometer. These valves permit us to measure
the minimal and maximal pressures. Tlic mercury man-
ometer records only the mean pressure, for the inertia of
mercury is too great to permit it to follow accuratelv the
changes in blood pressure. To find the maximal pressure,
first start the drum and take a short normal record, then
stop drum and close stop-cock i and open cock 3. The
float should rise and record the maximal pressure. Let
drum turn a short distance, then stop drum, close cock 3
and open cock i. To Hud the minimal pressure repeat the
procedure, this time opening cock 2. The float should fall
until it indicates the minimal pressure.

c. Escitation of the Peripheral Bud of the Right l^igus.

The operator now ties two ligatures around the vagus
near each other and close to the center of the isolated por-
tion of the nerve, and then cuts the nerve between them.
Place peripheral end of vagus on the electrodes, taking care
that they touch nothing else. Close key of primary circuit ;
see that vibrator works well. Record a curve of normal
pressure for about 10 seconds and then let the apparatus
man open short-circuit key. If weak, the current should
slow the heart, and if strong, should stop it. Strengthen
current if necessary. Excite for only about 10 seconds,
then close short circuit and watch recovery about 15 sec-
onds. Repeat the experiment 4 times, to provide a record
for each student, and give an interval of half a minute be-
tween the succeeding tests.

d. Record of Respiration ivitJi Pneumograph.

Place a receiving tambour on a stand, so that cork at-
tached to the membrane rests against the base of the thorax
of the animal in the position to give the greatest movement.
Connect with recording tambour, shown at A in Fig. 30.
Take record of respiration with each of the experiments
of part d.

c. Excitation of Central End of the J'agus.

Now while taking record of blood pressure and respira-

CIRCULATION AXD RESPIRATION OF MAMMAL. I43

tion, excite central end of vagus with weak current. Affer-
ent (sensory) fibers are excited, resulting in the following:

I. — Excitation of respiratory center, causing change in
amount and frequency of respiration.

2. — Excitation of vaso-motor center, causing usually a
rise, but occasionally a fall of blood pressure.

3.— Excitation of vagus center, causing slowing of heart
and usually a fall of pressure, in spite of vaso-constriction
which may occur.

4. — If current is too strong, and the anaesthesia incom-
plete, there may be reflex excitation of motor centers, caus-
ing convulsive movements which may mask the other effects
and cause a rise of blood pressure.

Now let the student tie off the right carotid below can-
nula ; remove cannula from artery ; hold a dish under the
cannula and then disconnect bulb from manometer tube ;
wash bulb and cannula out thoroughly ; connect bulb again
with manometer ; put cannula in dish of Na^So^. Handle
bulb and cannula with care, as they are fragilt and hard
to replace. Sponge up all fluid spilled and put apparatus in
order for next experiment. Disconnect and remove pneu-
mograph.

/. Excitation of Peripheral End of Left Vagus.

The student who is to operate, takes the animal-board
to the operating table and proceeds to prepare the artery
and nerve of the left side, the other students doing the work
assigned in the schedule. When the operation is finished,
test and record normal blood pressure as before. Any ex-
]:)eriments not successful on right side may be repeated. In
any case the operation is to be done and a normal record
taken.

g. Excitation of Sciatic Nerve.

The sciatic nerve lies beneath the vastus externus on the
middle of the external surface of the thigh. Remove hair
over region : cut skin longitudinally for 2 inches ; cut
through vastus externus and expose the nerve. Animal
must he well under the ether before nerve is handled, and
II

144 EXPERIMENT XXV.

especially on stimulating. Pass a ligature under nerve and
tie ends together. When ready to excite, ligate peripheral
end of part exposed and cut peripherally to ligature ; place
nerve across electrodes, which must not touch anything else,
then apply current. See rise of blood pressure due to re-
flex vaso-constriction, or, as not infrequently occurs a fall
due to reflex vaso-dilation (see Howell, p. 541). If cur-
rent is too strong or animal not well under, convulsive move-
ments will be produced which will mask the effect desired.

/;. Blood Pressure during Asphyxia.

Expose the trachea and place lozv dozmi upon it a clamp
used for rubber tubing, so that the trachea can be closed
off quickly. Start drum at rate of one or two mm. per
second, then clamp off trachea, marking the instant this is
done by means of short circuit key. Observe the following
stages :

I. — Dyspnoea. Blood pressure rises gradually. Deep
and prolonged respirations, with short expirations, soon
affect the blood pressure in a marked manner.

2. — Convulsions. Each convulsion is accompanied by
a rise of blood pressure.

3. — Weakening and slowing of heart beats ; respirations
feebler and fewer ; finally both heart beats and respirations
stop.

/. Elasticity of Lniig Tissue.

Make incision in trachea ; insert cannula ; and connect
with a water manometer, noting the level of the fluid. Open
the chest and observe the rise of water in tube when air
enters chest and lungs collapse. To open chest, first make
an incision with knife over the entire length of the sternum ;
grasp ensiform cartilage with strong forceps ; push point
of shears or bone forceps through chest wall at end of
ensiform cartilage and cut sternum lengthwise, in the
median line, to within an inch of its upper end. Keep point
of shears close to sternum, to avoid cutting lungs or other
organs. Pull the cut edges of the sternum apart and see
the collapsed lungs. Note the amount of elastic contraction

CIRCULATION AND RESPIRATION OF MAMMAL. 1 45

of the lungs, as measured by height of rise of water in man-
ometer.

NOTES.

In mounting the curves, be careful to preserve the part
of each record which shows the relation of writing points,
and the portion showing lo seconds before, and 15 seconds
after the period of stimulation. Draw long vertical lines
across the curve, to the top of the paper, at points 4 seconds
before stimulation, at the end of stimulation, and 10 seconds
after stimulation ; also draw shorter verticals at a distance
of 3 seconds on each side of the long verticals and cutting
the respiration and blood pressure curves.

To find the blood pressure, measure from the base line
given by the time signal to the middle of the highest pulse
beat near a long vertical, and multiply by two. For heart
rate, count the pulse beats in the 6 seconds between the short
verticals and multiply by 10. In a similar manner determine
the number of respirations per minute. Write the figures
obtained, on the cardboard above the mounted curve, at
points corresponding to the observations.

In the notes accompanying the curves, state the cause
of the changes in arterial pressure, pulse, and respiration
caused by the excitations. Give brief statements of the
results obtained under each of the subheadings of the
experiment.

146

F,Xr'KK IMF/NT XXV.

CIRCULATION AND RESPIRATION OF MAMAIAL.

147

148

KXPERIMENT XXV.

CIRCULATION AND RESP1RATI(3N OF MAMMAL. I49

EXPERIMENT XX\ I.

Circulation and Respiration of the Mammal, Continued.

a. Exciiatioii of Rii:;lit Depressor Xerze.

Tlie depressor is an afferent nerve from the root of the
aorta, and hence excitation of the peripheral end has no
cft'ec . Excitation of central end has little effect on the
cardiac centers, but causes dilation of peripheral vessels.

Expose the carotid as in Experiment XXV. To find
the depressor, remember that vagus lies behind artery and
the depressor and the sympathetic to the inner side. High
up tlie vagus gives off a transverse branch, the superior
laryngeal, (see diagram, Experiment XX\") to the larynx.
The depressor arises as a very slender nerve by two branches
from this, or one from this and one from the vagus. Find
the place of division, then trace the nerve down for an inch
or more, tie a thread about it and cut peripherally to thread.
Handle nerve with utmost care and see that it does not dry.

Now isolate carotid and insert cannula, connect with
manometer ; apply pneumograph ; record normal curves of
blood pressure and respiration. Excite central end of de-
pressor while drum is running. The latent period is long.
Excite only long enough to produce an evident effect, and
let drum run till recovery is well under way. Take four
records, waiting in each case until recovery is complete.
Notice that rate of heart is practically unchanged.

b. Bxcitation of Left Depressor Xerve.

Prepare depressor and carotid of other side and repeat
above experiment.

c. Tracheotomy and Artificial Respiration.

Remove cork of bottle in outfit for artificial respiration,
put about an inch of ether in the bottom, replace the cork.
Make an incision in the trachea, insert the cannula, and tie
it firmly in place with a strong ligature. Now give the

150 EXPERIMENT XXVI.

ether by holding the cone above the tracheal cannula. To
open the chest, first make an incision with knife over entire
length of sternum, grasp ensiform cartilage with strong for-
ceps ; push point of shears or bone forceps through chest
wall at end of cartilage and cut sternum lengthwise, in the
median line to within one inch of its upper end. Keep point
of shears close to sternum to avoid cutting lungs or other
organs. Special care is necessary at the upper part, or blood
vessels will be cut. While this is being done, the apparatus
man should prepare artificial respiration apparatus and test
the amount of ether it gives. Regulate supply of ether by
means of clamps on tubes connecting with ether bottle.

As soon as the chest is opened, with clamp on side tube
open, connect tracheal cannula with ether bottle, and start
bellows, pumping at rate of once a second. Screw up
clamp on side tube until the lungs are seen to expand and
relax well.

Observe the effect of artificial respiration on the curve
of blood pressure. The respiratory waves of the curve are
now reversed, the curve falling soon after the air begins to
enter the lungs, and rising soon after beginning of expir-
ation, due to elastic recoil of lung.

d. The Current of Action of the Heart.

Draw chest walls apart with the hooks provided. Open
the pericardium widely, taking care not to cut the heart in
doing so. Now hold the bone of a nerve-leg preparation in
forceps, with nerve hanging down ; let the nerve lie upon the
beating ventricle lengthwise ; the muscle should contract
with each beat. If it does not, lift it and try again. The
warm blood quickly injures the nerve, and hence the latter
should not be left long in contact, until the desired effect
is seen.

c. Ohservation of Exposed Heart during Vagus Excita-
tion.

Observe the effect of excitation of the peripheral end of
a vagus nerve on the rate and strength of beat of the ex-
posed heart. Test with weak, medium, and strong currents

CIRCULATION AND RESPIRATION OF MAMMAL. 151

/. Tension of Ventricle during Systole and Diastole.

Take the ventricle gently between the thumb and fingers,
and feel it harden with each systole.

g. Observation of the Changes in Heart during Death
from Asphyxia.

Open chest wadely so as to obtain a good view. Stop
artificial respiration and observe the effects of asphyxia on
the rhythm of auricles and ventricles as the heart dies. Make
notes of the order in which the strength of beat of auricles
and ventricles changes. Notice any irregularities, and
which auricle or ventricle gives out first. What part of
heart is most distended at death?

h. Innervation of Diaphragm by the Phrenic Nerves.

These nerves are easily found, running down lateral
and posterior sides of pericardium. Excite one, then the
other, observing contraction of diaphragm from upper side.
Open the abdominal cavity by one incision in median line ;
observe relations of organs ; push viscera down and excite
phrenic while looking at under side of diaphragm. Notice
that contraction of diaphragm depresses the floor of the
chest ; thus increasing chest cavity and lessening abdominal
cavity.

/. Peristalsis of Intestines.

Observe any peristaltic movements that may occur be-
cause of exposure to air and loss of blood. See direction
of waves. Watch for anti-peristalsis. Try effect of mechan-
ical and electrical stimulation of stomach and intestines.
Excite bladder electrically.

NOTES.

Write up the notes as directed in the preceding experi-
ment.

152 EXPERIMIvNT XXVI.

CIKCUI.ATION AND RESPIRATION Of MAMMAL. 1 53

154 EXPERIMENT XXVI.

CAROTID PULSE OF MAN. 155

EXPERIMENT XXVIL

The Carotid Pulse in Man.

a. The Ponii of the Pulse.

Mount a recording tambour on a stand and connect it
with an open tambour designed for carotid artery, leaving
side tube open. See that the lezxr of the tambour is hor-
kontal. Apply the open tambour to the skin of the neck
over the artery, and fasten it in place with the U-shaped
spring, placing the ball of the spring in the socket on the
back of the tambour and placing the block against the
opposite side of the neck. Then test
the working of the outfit by pinching
the side tube. With each heart beat
there should be an excursion of the
lever of at least 5 mm. Adjust posi-
tion of tambour on neck, and pressure
of spring to give the largest pulsation,
then bring writing point very lightly

I^'ig- 33- Tambour and . /- <->, , i

neck spring used to study agauist drum. btart drum at 5 mm.
A ^ sprhig*^ '^B'°ban-and- per secoud, closc side branch with
open'ti±ur?c!'l'iock' Spring dip and record the curve of the
pulse.
Unless the friction of writing point upon drum is made
as slight as possible, small waves of the pulse curve will be
obscured. Mark on the curves to indicate the primary
wave and the dicrotic notch. The former results from the
systole of the ventricle, and the latter from relaxation of
the ventricle and closure of the semilunar valve. The
dicrotic notch therefore divides the pulse into its systoHc
and diastolic portions, and is to be looked for at about the
end of the first third of the curve. Do pre-dicrotic or post-
dicrotic waves occur in the record? Take records with four
widely different speeds of drum, and observe the effect on
the form of the curve.

h. The Pulse Rate.

Mount a time signal to write below the pulse curve, con-
nect it with the clock circuit, start drum at 5 mm. per sec-

156 EXPERIMENT XXVII.

ond, and record the curves of time and pulse. Draw per-
pendiculars at intervals of ten seconds cutting the pulse
curve, and determine the rate of the pulse for three cc«i-
secutive periods of ten seconds.

c. Dnrafioji of Systole and Diastole.

Mount a fork in place of the time signal and record
curves .of pulse and fork with the fastest speed of drum
given by clockwork. Then, without moving drum, remove
clip from side tube, and record a base line for the pulse
curve. When the curves have been fixed, draw arcs with
dividers from beginning of primary wave and from bottom
of dicrotic notch to the base line, using a radius equal to
the length of the writing lever and centers on the base line.
Draw perpendiculars from the points where the arcs cut
the base line, through the fork curve. Count up the fork
waves between the perpendiculars, and thus determine the
duration of systole and diastole. Make this determination
for five consecutive pulse beats and state the average in
your notes. Results should be changed to looths of a
second by using number found in calibrating fork.

d. Effect of Exercise. '

Go through the form of taking a normal record, as in c,
to make sure that the neck tambour is properly adjusted,
and that the recording tambour is writing well. Then,
without moving the drum or either tambour, detach the
rubber tube where it joins the glass T. Take a quick rim
down stairs and back, connect up the tambour as soon as
possible, and record the accelerated pulse. Determine dur-
ation of systole and diastole as before.

Which changes most in the quickening of the pulse due
to work, the systolic or the diastolic portion? Are any other
changes in the pulse curve to be observed? If so, describe
them.

CAROTID PULSE OF MAN. 1 57

158

F.XrF.RlMICNT XXVII.

I^ORM AND POSTPONEMENT OE RADIAL PULSE.

^59

EXPERIMENT XXVIII.
The Radial Pulse Studied by the Tambour Method.

a. Form of Radial Pulse.

Connect a recording tambour with a tambour designed

for radial artery, leaving side branch of tube open. Arrange

arm rest and tambour as
shown in the diagram. Mark
the point on left wrist where
strongest pulse is felt. Sub-

Fig. 34. Method of applying tani"
bour to wrist, to obtain sphygmo-
gram from the radial artery. A,
cross section of wrist; B, back board
of arm support; C, cabinet maker's
clamp; D, clamp fastening L rod to
the horizontal rod of arm rest; E,
clamp fastening tube of tambour to
short arm of L rod; F, tambour with
disk, and prop to rest on artery.

ject seats himself comfortably
in chair, holding one end of
arm rest in lap, while other
end is placed on table or stool
so as to tilt it at a suitable
angle for the arm to rest eas-
ily. Place arm on rest with
marked point toward tam-
bour ; fasten thumb with loop
of cloth, using holes in back
board : apply button of tambour to marked spot, and adjust
tambour so that rod bearing button is in line with tube of
tambour and perpendicular to surface of wrist. Vary the
])ressure on artery by sliding tube of tambour in clamp
until largest pulsation is given. An excursion of 3-5 mm.
with each heart beat should be secured, but a smaller move-
ment will suffice where this cannot be obtained. The arm
must be relaxed and perfectly quiet. Record the radial
pulse on a drum and observe whether the same waves
appear as in the carotid pulse.

b. Postponement of the Radial Pulse.

Arrange to write carotid and radial pulse and fork
curve in same vertical line. Make sure that the levers of
the tambours are horizontal. Mark relative position of
points, then record the three curves with fastest speed given

l6o EXPERIMENT XXVIII.

by kymograph. Without disturbing apparatus, remove
cHps from side tubes and, with the levers horizontal, record
base lines for the two pulse curves.

Fix the tracing, and then, with centers on the base
lines and the lengths of the levers as radii, draw arcs from
beginnings of corresponding primary waves to their respec-
tive base lines ; then correcting for positions of points, draw
perpendiculars through fork curve and find duration of
postponement of radial pulse as compared with carotid
pulse. Take average for three consecutive beats.

FORM AND POSTPONEMKNT OF KADIAL PULSE. l6l

l62

kxi'f,r]mp:nt xxviii.

INFLUENCES AFFECTING RADIAL PULSE.

163

EXPERIMENT XXIX.

The Radial Pulse as Recorded by the Jacquet Sphygmo-

graph.

This is probably the most useful instrument for exam-
ination of the pulse that we have. It is fragile, and must be
handled with care and returned in good condition. The
strap A is buckled about the left wrist, with the end B

Fig-. 35. Scheme of Jacquet's sphygniog^raph.

toward the hand. The instrument slips into groove C of
base, and thumb-screw D is turned into socket E. The
paper, shown in cross section at F, runs between the roller
G and two small wheels above it. Clock for moving paper
is wound by means of large thumb-nut H, started and
stopped by lever at /, and lever / gives a change of speed.
Clockwork for time marker L, is wound by means of thumb-
nut K, and gives fifths of a second. M is a clasp for hold-
ing L up out of harm when not in use. Button iV is pressed
on artery by cam wheel P, turned by thumb-nut Q, to vary
the pressure. Movements of iV, are transmitted through
rod R, to lever S, turning on axis T, thence to lever U.

164 EXPERIMENT XXIX.

turning on axis V, and finally to marker W. Position of
writing point on paper is regulated by thumb-screw D.

CAUTIONS.

(i) Be careful not to injure the time marker. Raise
and lower it with the fine point of a knife or pencil. It
must ahcvays be lifted into clasp before reiroving the paper.

(2) Avoid bending the writing pointer when inserting
the paper.

(3) Do not wind the clockwork too tight.

(4) Instrument must be held level to record time accu-
rately.

( 5 ) Pressure on artery is regulated by sinall move-
ment of cam.

a. Normal Curies and Effect of Position of Body.

Place several strips of paper around a large drum, and
blacken as usual, cutting the strips loose as needed. Place
end of a strip between roller and wheels, start clockwork,
and run the paper in, to the extent of one inch.

Having adjusted instrument so as to give the largest
pulsation, proceed to make records while sitting and stand-
ing quietly, using slow speed of paper. In this and all sub-
sequent tests, take care not to move arm or hand when the
record is being written. Report the rate as recorded for
six seconds.

b. Effect of Compressing Brachial Artery.

While the tracing is being taken, compress the brachial
artery with hand or a tourniquet.

c. Effect of Deglutition.

Start the paper at the fast rate, record a few beats, then,
while record continues, take several swallows of water in
quick succession, marking on the record the e.vact time
when the swallowing begins and ends. Determine the rate
before, during, and after swallowing. The increase in rate
is explained as a lessening of vagus influence. The swal-
lowing center is in the medulla oblongata not far from the

INFLUENCES AFFECTING RADIAI. PUESE. 165

vagus inhibitory center, and nervous impulses overflowing
from the former inhibit the latter.

d. Effect of Inhalation of Aniyl Nitrite.

Slow speed of paper. Record normal pulse for 10 beats,
then begin to inhale a drop of amA-l nitrite that will be
placed upon a handkerchief by the instructor. Associate
should mark on record the exact time of inhalation. Con-
tinue record to end of paper. This drug acts chiefly, when
taken in sm.all amounts, on the muscles in the walls of the
small vessels, causing a dilation. Fall of blood pressure
and increased dicrotism of the pulse results. The change
in the level of the writing, frequently seen, cannot be taken
as evidence of the diminished arterial pressure. The writ-
ing point must be placed high before the inhalation occurs,
or it will run off the lower edge of the paper. Do not re-
peat.

e. l\ilsalz'a's Experiment.

This experiment and the following one are not without
danger, and should not be practiced to excess, nor by any-
one with an abnormal heart or arteries.

Record 10 normal beats, then take a deep breath, and,
with mouth and nostrils closed, make a strong expiratory
effort for eight or ten seconds, then breathe freely. Mark
time of each stage on record. Report effect on rate and
shape of pulse curve. The latter is especially interesting.
The expiratory effort drives the blood out of the chest into
the arteries, and prevents entrance of venous blood into the
chest by compressing veins and right heart.

/. Mailer's Experiment.

Record ten beats, then exhale as completely as possible,
and with mouth and nostrils closed make a strong inspiratory
effort for ten seconds, then breathe freely. Mark on record
and report as before. The forced inspiration tends to keep
the heart and large vessels dilated, tends to prevent blood
from leaving chest, and causes a rush of blood into the chest
bv way of the veins.

I 66 EXPERIMENT XXIX.

The sphyginograph cannot give a measure of blood
pressure. The changes to be observed in the level of the
curve are in part due to alteration of the amount of dis-
tension of the venae comites about the arterv.

INFLUENCES AFFECTING RADIAL PULSE. 167

1 68 EXPERIMENT XXIX.

CIRCULATION IN FOOT OF FROG. . 169

EXPERIMENT XXX.

Capillary Circulation in the Web of the Foot of a Frog.

Destroy the brain of a frog by a pithing needle, and
plug the skull cavity with a pointed match. Be sure to have
the match ready to insert at the instant the pithing needle
is withdrawn, so that the least possible blood shall be lost.
Wrap frog in moist cloth and place on special frog-board,
face down, and spread the web over the opening, keeping
in place by pins through outer toes. Avoid stretching web
too tightly, and keep it moist, not wet. Place board on
microscope stage.

Examine first with low power. If the blood is not seen
to circulate through the smaller vessels, the web has prob-
ably been stretched too tightly, or the frog has not recovered
from the shock caused by pithing. Decide which of the ves-
sels are arteries, capillaries and veins, observing where the
blood flows from large to small and from small to large ves-
sels, where the blood stream is most rapid and where it
pulsates.

I. Now choosing a small artery, observe with higher

power the following points :

a. Pulsating stream.

b. Rapid axial stream ; lighter, peripheral layer, — the

"inert layer."

c. Eddies of the stream at a bifurcation.

II. Examine a small vein and observe:

a. Constant stream (sometimes pulsating if the shock

from the pithing has not been recovered from,
and there is vaso-dilation).

b. Slower current, and less marked "inert layer" than

in artery.

III. Examine capillaries, and observe:

a. Frequent anastomoses.

b. Condition and behavior of corpuscles.
A. Red corpuscles (erythrocytes).

I. Shape, transparency, color.

lyo EXPERIMENT XXX.

2. The number that can pass abreast in a cap-

illary.

3. Position of long axis with respect to cur-

rent.

4. Elasticity, and change in shape when com-

pressed, or when turning a corner.

5. Passage through a capillary apparently

smaller than cell.
B. White corpuscles (leucocytes).

1. Shape and color.

2. Peripheral arrangement.

3. Slow progression, and rolling motion.

IV. Vaso-inotor Action.

Expose sciatic nerve, using the utmost care not to injure
the blood vessels. Cut high up, and dividing branches,
raise from wound and lay on a piece of moist filter paper
placed over the skin. (There is an acid secretion on the
skin which will injure the nerve.) Of course the nerve
must be handled as little as possible and never be com-
pressed. Now excite nerve with induction current "at the
same time that a suitable part of the web is being examined
with a low power. The vessels should be seen to grow
smaller and the circulation should be consequently slowed,
or stopped.

V. Diapedesis, i. e.. Migration throngh Wall of Capillary.
(This is optional.) This is not often seen to occur

under normal conditions, but the phenomenon is of frequent
occurrence when an irritant cavises local inflamation. This
can be best studied in the mesentery, a slight burn from a
hot glass rod being a suitable irritant.

Examine with low power the effect upon the circulation
of the part. Then choosing a capillary whose walls can be
seen distinctly, watch carefully a leucocyte resting against
the wall, and observe its change of shape as it passes
through the wall. Make drawing illustrating the method
of progression. Red corpuscles do not pass through, unless
the walls have been greatly injured, since they do not
possess amoeboid power.

CIRCULATION IN FOOT OF FROG. 171

172 EXPERIMENT XXX.

HUMAN BLOOD PRESSURE. 1 73

EXPERIMENT XXXI.

Measurement of Human Blood Pressure in Different
Positions.

The blood pressure is a measure of the potential energy
available for overcoming the resistance offered by the walls
of the vessels to the flow of the blood. Arterial blood
pressure is a measure of the status of the following factors
upon which it is dependent, viz : the amount of energy
imparted by the heart to the blood, (varying with rate and
strength of beat, and volume of output), and the amount
of resistance encountered by the blood, (varying with the
friction in the large vessels, determined largely by the
elasticity of the walls, and with the friction in the small
vessels, determined chiefly by the action of the vaso-motor
nerves). Since a high blood pressure means excessive
work for the heart, and since a very low blood pressure
means that too little blood is being pumped, (because of lack
of blood, imperfect heart action, or valvvilar lesions), or that
the vessels are abnormally dilated, it is evident that a meas-
ure of the arterial pressure is of diagnostic importance.

If one presses with the tip of a finger upon the skin
over an artery, at first very lightly, and then with more and
more strength, he feels first a slight thrill, then a stronger
pulse, and finally a lessening of the pulse, until it is alto-
gether lost, except at the side of the finger nearer the heart.
If the finger is gradually removed, these sensations are felt
in the reverse order. With practise a fairly accurate esti-
mate of the arterial pressure can be obtained in this way.

Apparatus. — A sphygmomanometer is an instrument
devised to measure more accurately than the finger, the
systolic, i. e. maximal arterial pressure, and in the case
of the Erlanger instrument, to also record the pulsations
as a means of estimating the diastolic pressure.

The Riva-Rocct Sphygmomanometer. — The instru-
ment (see Fig. ;^6) consists of a reservoir of mercury, to

174

EXPERIMENT XXXI.

the bottom of which a capillary manometer tube passes,
and which connects with a rubber cuff, which is strapped
over the internal surface of the upper arm at the seat of
the brachial artery, by a broad unyielding band of leather.
Air is pumped into this system by a bulb, and is let out
again, either rapidly through an outlet tube, or slowly
through a fine pin hole in the cap of a vertical tube, con-
trolled by the finger. A three-way cock permits communi-
cation to be made between the inflating bulb and the cuff,
and between latter and the outlet tube.

Gaertner's Tonometer. — This instrument permits one
to know what pressure applied to the second joint of the
finger, will prevent the blood from
entering the finger, as shown by the
sensation and change of color which
follow the return of the blood. Gaert-
ner considers this to be the mean
arterial pressure. The instrument
consists of a mercury manometer, con-
nected with a pneumatic ring, to be
placed over the second joint of the
finger, and an inflating bulb. The
same apparatus may be used as by the
Riva-Rocci method, with the substitu-
tion of the ring for the finger, in the
place of the bag for the arm.

Ereanger's Sphygmomanometer.
— (See Howell's Physiology, p. 456,,
Fig. 191 and 192.) This instrument
records systolic and diastolic pres-
sures. The mercury manometer, arm
piece and inflating bulb, are the same as for the Riva-Rocci.
In addition to this the arm piece is in communication with
a rubber bulb, which is enclosed in a glass bulb, which is
connected with a recording tambour. The tambour records
the fluctuations in pressure. Two forms of the apparatus
exist in the laboratory, differing essentially in the stop-
cocks used to govern the flow of the air. These are
described on cards accompanying the instruments.

J'igr- 36. Laboratory
form of Riva-Rocci in-
strument. A, reservoir of
niercurj'; B, capillary
manometer tube; C, tube
connecting with rubber
cufTonarm (or in the case
of the Gaertner experi-
ment, with the pneumatic
ring); D, rubber bulb; E,
outlet tube; F, vertical
tube, with pin hole in the
cap.

HUMAN BLOOD PRESSURE. I 75

Experiment. — Each student is to determine the systolic
pressure of his associate with the Riva-Rocci, Gaertner, and
Erlanger instruments, and the diastolic pressure with the
Erlanger apparatus, under the following conditions :

1. From the right arm in the sitting position.

2. From the left arm in the sitting position (the usual
method).

3. From the left arm, standing, with arm supported
on table.

4. From left arm, lying down.

In the sitting position, the subject's arm is to be placed,
extended, on the table, on a level with his heart. In order
to take the required number of observations, the student
must thoroughl}- understand the instruments and the method
of work, and have practiced taking the pulse in a number
of preliminary tests. The results should be systematically
tabulated, and a suitable table for entering them should
be prepared before making the observations.

a. The Systolic Pressure.

1. Gaertner's Tonometer. — Apply an Esmarch band-
age to the finger. Connect the tube from finger ring or bag
with the Riva-Rocci manometer. Using the bulb, carefully
raise the pressure to 130 mm. Now turn the stop-cock so
as to shut the inflating bulb ofif from the manometer.
Remove the bandage. The falling pressure as indicated
by the manometer can be controlled by placing the finger
over the leak in the top of the vertical tube (F). Read the
pressure when the formerly bloodless extremity of the
finger first begins to flush and become cyanotic with the
returning blood.

2. The Riva-Rocci Sphygmomanometer. — Connect
the arm bag with this instrument. While feeling the sub-
ject's pulse with the fingers of the right hand, with the left
raise the pressure in the manometer to about 150 mm.
Controlling the leak as before, read the pressure at the
instant the return of the pulse is felt. Caution. — Do not
.lustake the pulse in your own fingers for that of the subject

13

176 EXPERIMENT XXXI.

3. The Erlanger Sphygmomanometer. — Having
connected this instrument with the cuff on the arm, proceed
as before and read the pressure at the instant of the return
of the pulse. The danger of error from feeling the pulse
in one's own finger tips, is slight if one notes that the pulse
which is felt coincides with the pulsations of the tambour
attached to the glass bulb.

b. The Diastolic Pressure.

The Erlanger Sphygmomanometer. — See that tam-
bour lever writes lightly upon the drum. Raise pressure
to about 100 mm., then allow it to fall to 90 mm. Shut off
the leak and record on the drum a series of at least 15 pulse
beats at this pressure. Now start the drum, open leak "and
allow pressure to fall 10 mm., close off leak and record
another series of 15 pulse waves. Continue after this man-
ner until the height of the pulsations decreases markedly.
Be careful to mark on record the pressure at which each
series of pulsations was obtained.

"After a certain level (in normal pulses 25 to 40 mm.
below the systolic pressure) the extent of the oscillations
diminishes rapidly. The lowest point at which it remains
maximal is the diastolic lateral pressure." (Sahli.)

HUMAN BLOOD PRESSURE. . 177

178

F.XriiRrMJCNT XXXI.

NORMAL SOUNDS OF ilKAKT.

179

EXPERIMENT XXXII.

The Normal Sounds of the Heart.

The normal heart sounds may be heard with the unaided
ear, but the stethoscope is commonly used. It consists

Fig. 37. Diagram showing position of heart in cliest, position of valves as
projected on the wall of the chest, and the parts of the chest where the sounds
of the heart are heard best. M. position of apex beat, and sound from mitral
valve; T, sound from tricuspid valve; A, sound from aortic valve; P, sound from
pulmonary valve.

essentially of a receiving disk and a pair of ear-tubes, con-
nected with tubing. It aids by multiplication of the sound
and by excluding outside sounds. Distracting noises, to

l80 EXPERIMENT XXXII.

be avoided, are apt to ari^- f'-^'n (.1} rubbing of tubes
aa^rxi«ot ca.x,ii other or against clothing, (2) breathing by the
listener upon the metal spring holding the ear-tubes, (3)
movement of the receiving disk upon the skin, (4) move-
ments or breath sounds of the subject, and (5) talking
b\ either subject or listeners. The multiple instrument
enables several persons to hear the same sound at once, and
therefore is useful in teaching. The ear tubes should be
cleansed before inserting them for the fint time, to avoid
possible infection. The tubes are placed in the ears with
the tips pointing inward and upward. The receiving disk
is held firmly against the skin. Avoid kinks in the rubber
tubes.

The diagram shows the position of the heart in the
chest, and the letters. A, P, T, and M mark the areas
where the disk is placed in listening to the separate valve
sounds. Each letter is connected by a dotted line with a
dark spot showing the position of the corresponding valves.
These four areas, known as the aortic, pulmonary, tricuspid,
and mitral areas, are so named because the sounds made
by the closure of the valves named are heard best in those
places, but it must be remembered that no one of the valve
sounds can be isolated at any point, but that all enter into
the composite sounds heard at each area. Tt is the relative
loudness of particular sounds that give the areas the names
which they bear.

(T. Ausc\dtatio)i oi'cr the Loiiter Part of the Chest.

One student of the group is chosen as subject, and he
seats himself in a chair, the others seating themselves
closely around him. The receiving disk is first applied
over the mitral area, viz. at the point where the apex
beat is felt, in the 5th intercostal space, slightly within the
nipple line. With the- disk in this position, listen to the
licart sounds for several minutes. Observe ( i ) the two
distinct sounds with a very short interval between them,
(2) the greater loudness of the first sound, (3) the boom-
ing character of the first sound contrasted with the sharp
click of the second. The first sound, which marks the
beginning of the systole of the ventricle, is a compound

NORMAL SOUNDS OF HEART. l8l

sound, composed of the click caused by the closure of the
two auriculo-ventricular valves, the sound made by the
contraction of the muscular substance of the two ventricles,
and by the vibrations of the suddenly tensed chordae ten-
dineae. The muscular element which prolongs the sound
into the period of systole, helps to give it the booming
character. Normally the two ventricles contract together,
and the mitral and tricuspid valves close at the same
instant, so that the action of the two sides of the heart
is represen'.ed by a single sound. Compare it with
the sound heard by placing the disk of the stethoscope
on the muscle of the forearm and causing it to con-
tract rhythmically. The second sound is produced by
the closure of the aortic and pulmonary semi-lunar
valves, which normally close at the same time. Now
apply the disk over the tricuspid area and observe ( i ) the
greater prominence of the valve sound and lessened muscle
sound, (2) the clear and high pitched quality of the sound,
(3) the comparative loudness of the first sound as before,
and (4) the rhythm, which is also the same as in the
mitral area. Change the disk quickly from one of these
two areas to the other, so as to bring out distinctly the
differences in the sounds. Apply it at intermediate points
and observe how the characteristic sounds of one area grad-
ually shade off into those of the other.

b. Ausciiltafioii over the Base of the Heart.

Apply the disk over the aortic area and observe ( i ) the
greater loudness of the second sound as compared with
the first, (2) almost complete absence of booming muscle
sound, (3) the same rhythm as before. The sounds heard
here are mostly valvular, and the aortic sounds predominate.
Listen in same manner at pulmonary area, and compare
the sounds heard in aortic and pulmonary areas. Listen at
points intervening between mitral and aortic areas. Change
the disk quickly between the four areas, and let the listeners
try to recognize the area by the sounds heard. L"se each
student as subject in turn.

In diagnosis it is often necessary to locate an abnormal
sound in relation to the pulse beat and thence to the

102 EXPERIMENT XXXII.

heart cycle. The first sound, produced by contraction of
heart muscle and closure of auriculo-ventricular valves, is
evidently systolic. The second sound, made by closure of
semilunar valves, is evidently diastolic. Therefore, any
sound occurring between the beginning of the first and the
beginning of the second normal sounds must be systolic,
and any sound occurring between the beginning of the sec-
ond sound and the beginning of the first sound of the next
cycle must be diastolic.

c. Time Relations of Heart Sounds and Pulse.

Experiment.— Record the radial and carotid pulse on
a drum along with a signal connected with a cell and Morse
key. Listen to heart sounds and let one listener so work the
key that the click of the signal shall exactly coincide with
the heart sounds. When he is able to do this well, as tested
by all the listeners, run drum at fast speed and record the
time of the sounds in relation with the two pulse curves.
The reaction time to sound varies from 0.15-0.20 sec,
according to the observer, hence to have the sound of the
heart and the signal coincide, the experimenter will have
to anticipate the beat, i. e., determine the rhythm by listen-
ing a short time and then tap at the instant that the beats
are to be expected. Exact results cannot be obtained
because there will be slight errors of judgment on the part
of the experimenter, and because the rate of the heart varies
somewhat with the respiration. Nevertheless, if care be
used, a good picture of the relative time of the coming of
the sounds of the heart and of the carotid and radial pulse
can be obtained.

Notice that the first sound slightly precedes the primary
upstroke of the carotid pulse (about .01 sec), and that the
second sound slightly precedes the dicrotic wave. Also
observe that the primary wave of the radial pulse begins
about half way between the two heart sounds. It is evident,
therefore, that the place of any sound of doubtful nature
can be located rather definitely in the cycle by its relation
to the carotid pulse, but not so well by reference to the
radial.

NORMAIv SOUNDS OF HEART. I83

l84 EXPERIMENT XXXII.

INFLUENCES AFFKcriNG RESPIRATION. 185

EXPERIMENT XXXIII.

Thoracic and Abdominal Movements in Respiration.

Apparatus. — Mount two recording tambours and a
time signal to write in a vertical line ; connect the signal to
clock circuit ; connect the two tambours with special rubber
lubes to two pneumographs, leaving side tubes open.

Experiment. — The subject seats himself comfortably,
then the cord of one pneumograph is passed around his
chest and the cord of the other around his waist. Tie them
with a tension that will extend the pneumographs about
2 cm. Subject should sit so as not to see the curves and
should pay as little attention to breathing as possible.

a. Xonnal Record.

After subject has remained quietly seated for at least
two minutes, place clips on side tubes, start drum at 2 mm.
per second and record curves for one minvite. N^atural.
unconscious breathing is what we wish to study, and hence
the subject should try to think of something else.

b. Effect of Using the J^oicc.

Record normal curves for 10 seconds, then read aloud
for 30 seconds. In same manner try the effect of counting
aloud in unison with the ticking of the clock. Alwaj'^
mark on curve the time when each test begins and ends,
and what was done. Note the effects on rate and character
of the movements.

c. Inhibitory Effects of S-a'alloiciug.

Take normal record for 15 seconds, then let subject
drink a glass of water without stopping, taking record dur-
ing the drinking and for 15 seconds after.

(/. Effects of Effort.

In the same manner observe the effect of trying to hold
two pin points as close together as possible without touching.

l86 EXPERIMENM' xmxiu.

for 20 seconds ; of clenching; the fists as tightly as possible for
20 seconds ; of clenching the fists as rapidly as possible for
20 seconds ; of pressing the hands upon the knees strongly
for 20 seconds.

Note the effect in the dift'erent cases, and explain the
difference.

e. Relation of Rate of Respiration to Rate of Heart

Replace the abdominal pneumograph by a carotid tam-
bour ; then study the following cases :

( T ) Relative rates under normal conditions, sitting
quietly.

(2) Effect of adding a column of 20 or more figures
rapidly.

(3) Eff'ect of recalling exciting experiences.

It is of course evident that voluntary control of the
rate of breathing in all of the foregoing tests lessens their
value. Usually it is only in the later tests, after the subject
has become accustomed to wearing the apparatus, and
the work has ceased to be interesting, that the subject will
breathe naturally. It is best, for this reason for all the
tests to be made first on one student and later on his asso-
ciate.

JNl'I.UKNCES AFFivCTINC RESPIRATION. 187

l88 EXPERIMENT XXXll).

JU/V 22

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