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DIRECTIONS

Laboratory Work in Physiology

FOR THE use; op

MEDICAL STUDENTS

WARREN P. IvOMBARD, A. B., M. D.

PROFESSOR OF PHYSIOLOGY, UNIVERSITY OF MICHIGAN

SECOND EDITION

GEORGE WAHR, PaBLisHER

ANN ARBOR

Copyright, 1914

BY

GEORGE) WAHR

7YU:JL

arvi-

RBOR PRESS

PREFACE

Every one who has attempted to plan a short course
of physiological experiments for Medical students, has had
to face the fact that only a few of the many experiments
which would be desirable, can be satisfactorily performed
in the alloted time. The course here outlined contains
only such experiments as can actually be made and properly
studied by the student himself, working three and a half
hours a day for 35 days. An additional week is spent in
extra work and examinations. Since the students for whose
use this book has been especially prepared, have a special
course in physiological chemistry, and are taught the physi-
ology of the eye, etc., in connection with the demonstration
courses devoted to the specialties, to avoid duplication, ex-
periments dealing with these subjects have been omitted.

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
excitation. At the same time he becomes acquainted with
the genera! physiology of striated, non-striated, and heart
muscle and of the nerves of the frog. He then studies
the reaction of his own muscles and nerves to various
forms of electrical excitation. Throughout this work, spe-
cial attention is called to the errors which the apparatus it-
self may introduce into the graphic records : the need of ac-
curacy of measurements ; the value of expressing the figures
obtained in plotted curves ; the importance of promptly writ-
ing up the notes taken during the experiments ; and the fact
that the reports given, should state what was observed by the
student himself, rather than what is written in text books.
The latter half of the course deals with the problems of
respiration, the circulation, the central nervous system, etc.

Only two afternoons are given to experiments on warm
blooded animals, but the experiments with the artificial

iv PREFACE

circulation apparatus, a special quiz on the subjects to be
covered, and a "dress rehersal" with the apparatus, have
so prepared the way, that even in this short time, many
of the most important facts relating to the circulation,
respiration and peristalsis are observed.

It is believed that the medical student should as far
as is possible, study the physiology of man, and during
more than a third of the course, the student, himself, is
the subject of the experiment. It is needless to say that
the frogs are rapidly killed before being used, and that
the mammals employed are thoroughly anaesthetized by
the student, under the direction of an instructor.

As 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
of saving time. Nevertheless, the harm which comes from
machine-like 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 i^iake a re-
liable diagnosis and keep a trustworthy case-book.

The library of the laboratory contains many journals,
books, monographs and reprints, and the instrument room
holds many forms of apparatus especially designed for re-
search work. Every facility of the laboratory is placed at
the disposal of those who show that they are capable of
independent work.

This edition contains a number of experiments not found
in the first, while the directions for many of the other ex-,
periments have been practically rewritten. Ten new illus-
trations have been added.

It gives me great pleasure to acknowledge the aid
which I have received in developing the methods employed
in this course from the former instructors and assistants

PREPACK V

in this department, and especially, from Professor S. P
Budgett, Professor A. E. Guenther, Dr. G. G. Crosier,
Professor W. P. Bowen, Professor C. J. Wiggers, Dr. F.
M. Abbott, Dr. N. N. Wood, and Professor W. F. Koch.
I am particularly indebted to Dr. Otis M. Cope for his
help in the preparation of this edition.

WARREN PLIMPTON LOMBARD.
Physiological Laboratory
University of Michigan
July I, 1 9 14,

CONTENTS.

General directions. Instruments, etc., to be purchased
by students. List of apparatus to be supplied by
the laboratory. The bulletin board. Method of
work. . , XIX

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

Method of killing frog.
Muscle preparation.

a. Experiment.

b. Plotting of curves.

J^XPERTMENT in.

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 IY.

Relation of amount of load to height of Hft and quan-
tity of v.'ork done. .21

a. Experiment.

b. Plotting of curves.

"VIU CONTENTS.

EXPICRIMENT V.

Fatigue of Human Muscle. 25

a. Effect of slow rate.

b. Effect of quick rate.

c. Effect of rest.

d. Effect of massage.

Experiment VI.

'Time relations of myogram 29

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

b. Time relations of myogram.

c. Measurement of records and computation of

time intervals.

Experiment A^II.

•Genesis of tetanus 35

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 VIII.
Rate of tapping 43

Experiment IX.

Independent irritability of muscle. . . . • . 47

Method of pithing frog, and of injecting curara.

Experiment X.

Isolated conduction in muscle. 53

Method of unipolar excitation.

CONTENTS. ix:

Experiment XI.

Contractions of non-striated muscle 57"

a. Time relations of the myogram,
h. Rate required to tetanize.
c. Spontaneous contractions.-

Experiment XTT.

The frog's heart ; its structure ; the relative time of ac-
tion of the different parts. . . . . 6r

a. Gross anatomy of frog's heart.

b. Origin and course of the wave of contraction.

1. Inspection.

2. The myocardiogram.

Experiment XIII.

Effect of Temperature on Heart Rate 67

a. Effect of air.

b. Effect of solutions.

Experiment XIV.
Refractory period and compensatory pause. . . • 7r

Experiment XV.

Response of resting heart to stimulation by induction

shocks y^.

a. Myogram of heart muscle.

b. Bowditch's staircase.

c. All contractions maximal.

d. Effect of frequent stimuli.

Experiment XVI.

Location of a few motor points on the human arm. . 79
The more efficient pole of an induction coil.

x contents.

Experiment XVIT.
Response of human muscle to separate induction shocks

and to a tetanizing current. .... 85

• a. Making and breaking induction shocks of vari-
ous' strengths,
b. Tetanizing current.

Experiment XVIIT.
Galvani's experiment. 91

Experiment XIX.

Polarization of electrodes. 95

a. Polarizable electrodes.

b. .N'on-polarizable electrodes.
Pfliiger's Law.

Experiment XX.

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

Experiment XXT.
Stimulation of human nerves b_y the direct current. . 105

Experiment XXII.

Currents of rest and action iii

a. Current of rest detected by a rheoscopic frog

preparation.

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

Experiment XXIII.

The reflex frog 115

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.

CONTlvNTS. XI

Experiment XXIV.
Reaction time for sound 119

Experiment XXV.

Cutaneous sensations and muscle sense. . . . 123

a. Cold and warmth spots.

b. Tickle and pressure spots.

c. Pain spots.

d. Muscle sense.

Experiment XXVT.

The knee-jerk as modified by reenforcing and inhibiting

influences. 129

a. Record of normal knee-jerk.

b. Motor reenforcements.

c. Reenforcement by sensory stimuli.

d. Psychic reenforcements.

Experiment XXVII.

Co'nditions determining the blood pressure and the ve-
locity of flow. 137

Artificial circulation apparatus.

part I.

Arterial and venous pressure.

a. Effect of inertia of mercury.

b. Effect of rate.

c. Effect of increased output.

d. Eftect of resistance.

e. Effect of resistance in two systems of arteries on

distribution.

f. Some clinical applications :

I. Effect of vagus inhibition.

Action of depressor nerve.
Traube-Hering waves.
Nitrite of Amyl.
Hardening of wall of artery.

xn CONTENTS.

PART II.

Intra-ventricular pressure and arterial pulse.

a. Effect of rate.

b. Effect of volume output.

c. Effect of peripheral resistance.

PART III.

Lesions of Heart VaWes.

a. Mitral stenosis.

b. Aortic stenosis.

c. Mitral insufficiency.

d. Aortic insufficiency.

ExPERIMIvNT XXVTII.

Circulation and respiration of the mammal. . . .151
Schedule of work. List of apparatus. Directions
to student caring for apparatus. Directions to
Assistant. Anaesthesia. Directions to anses-
thetizer. Directions to operator.

a. Measure of blood pressure in the carotid.

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

c. Excitation of central end of right vagus.

d. Excitation of peripheral end of left vagus.

e. Excitation of sciatic nerve.

f. Blood pressure during asphyxia.

g. Elasticity of lung tissue.

Experiment XXIX. ,

Circulation and respiration of the mammal continued. 167

a. Excitation of right depressor nerve.

b. Excitation of left depressor nerve.

c. Tracheotomy and artificial respiration.

d. Current of action of the heart.

e. Observation of exposed heart during vagus ex-

citation.

f. Tension of ventricle during systole and diastole.

CONTENTS. • xiii

g. Observation of the changes in heart during

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

Expkrim£;nt XXX.

Carotid pulse in man. 173

Form of the pulse curve, and effect of arterial pres-
sure.

a. The pulse rate.

b. Duration of systole and diastole.

c. Effect of exercise.

Experiment XXXI.

The radial pulse studied by the tambour method. . . 181

a. Form of radial pulse.

b. Postponement of the radial pulse.

Experiment XXXII.

The radial pulse as recorded by the Jacquet Sphygmo-

graph. 185

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. Miiller's experiment.

Experiment XXXIII.

Capillary circulation in the web of the foot of a frog. 191

I. In small artery.

II. In small vein.

III. In capillaries.

IV. Vaso-motor action.

V. Diapedesis.

VI. Capillaries of human skin.

XIV CONTENTS.

Experiment XXXIV.

Cilia 195

a. Work of cilia.

h. Effect of temperature.

c. Microscopic examination.

Experiment XXXV.

Measurement of systolic and diastolic pressure in hu-
man arteries. 199

Systolic pressure.

a. Tactile criterion.

b. Auscultatory criterion.

c. Criterion of sudden rise of pulse record.

d. Criterion of pulse form.
Diastolic pressure.

a. Auscultatory criterion.

b. Largest pulsation criterion.
Experiment.

I. Systolic pressure ; — tactile criterion.

a. Subject seated.

b. Subject standing.

c. Effect of exercise.

II. Systolic and diastolic pressures; — auscultatory

method.

a. Systolic pressure.

b. Diastolic pressure.

III. Systolic and diastolic pressures; — tambour

method.

a. Systolic pressure.

b. Diastolic pressure.

Experiment XXXVI.

Conditions changing the volume of hand. . . ,211

a. Tickling.

b. Pain.

c. Psychic excitation.

d. Cold.

CONTENTS. XV

Experiment XXXVII.
Venous pressure in man 215

Experiment XXXVIII.
Pulse in large veins of man 219

Experiment XXXIX.

The normal sounds of the heart 223

a. Auscultation over the lower part of the chest.

b. Auscultation over the base of the heart.

c. Time relations of heart sounds, cardiogram,

pulse curve.

Experiment XL.

Thoracic and abdominal movements in respiration. . 231

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.

Experiment XLI.

Measurement of expired air 235

a. Tidal air.

b. Supplemental air.

c. Vital capacity.

d. Complemental air.

Experiment XLII.

Regulation of body temperature. . . . . . 241

a. Loss of heat from skin.

b. Loss of heat from air passages.

Experiment XLIII.

Artificial respiration 245

a. Schaefer's method.

b. Effect of apnoea.

c. Sylvester's method.

ILLUSTRATIONS.

I. 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 8

3. Apparatus for recording contractions of a frog's

muscle, excited by induction shocks. ... 13

4. Curve of lift and of work. . . . . .21

5. Apparatus for automatically exciting muscle, by

letting the drum open the key 29

6. Method of preparing myogram for determination

of latent period 32

7. Apparatus for studying summation of contractions. 35

8. Scheme of electrical connections of primary coil

in two forms of induction apparatus. . . 37

9. Relation of brain to skull of frog 47

10. Dissection of right leg of frog 48

11. Diagram of experiment on the action of curara . 49

12. Apparatus recording beats of a frog's heart. . 61

13. The gross anatomy of a frog's heart. ... 63

14. Apparatus to detect direction of flow of current in

a simple circuit 79

15. ■ Apparatus to detect direction of flow of current

in secondary coil of an induction apparatus. . 80

16. Apparatus for unipolar excitation of human

nerves, with an induced current. . . .81

17. Diagram of location of motor points on flexor side

of arm, (after Erb.) 81

18. Arm rest for support of hand and electrodes. . 85

19. Apparatus for recording movements of thumb. 86

20. Apparatus for Galvani's experiment. . . -9^

21. Method of arranging non-polarizable boot elec-

trodes in moist chamber 97

22. Diagram to illustrate Pfliiger's law. ... 98
27,. Method of using rheocord. . 10 1

XVlil ir.UJSTRATlONS.

24. Ap'paratus for stimulating human nerves by the

direct current. 105

25. Diagram of the course, and of the effects of the

direct current, applied through the skin tO' the
nerves of man. 107

26. Apparatus for recording reaction time to sound. 119

27. Diagram of nervous paths followed by the nerve

impulses causing the knee-jerk and its reen-
forcements 129

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

cording the swing of the lower leg, in the knee-
jerk experiment 131

29. Artificial circulation apparatus. . . . .137

30. Recording tambour 145

31. Scheme of apparatus for studying the blood pres-

sure of a mammal. 153

32. Dissection of nerves of left side of neck of rabbit. 159

33. Method of inserting cannula into' carotid artery. 160

34. vSphygmogram of a normal and of a dicrotic pulse. 173

35. Diagram of a high and of a low pressure pulse. 175

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

man carotid pulse. 176

37. Method of applying tambour to wrist, to obtain

sphygmogram from the radial artery. . . 181

38. Scheme of Jacquet's sphygmograph. . . . 185

39. Laborator}^ form of sphygmomanometer. . . 201

40. Diagram of changes in brachial artery during

measurement of systolic and diastolic pressures. 203

41. Diagram of heart cycle, shoAving changes of form

of the right heart, and their relation to the ven-
ous pulse, carotid pulse and heart sounds. . 221

42. 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 223

43. Diagram of heart cycle, indicating changes of

form of the right heart, versus the cardiogram,
the venous pulse, the carotid pulse, and heart
sounds. . 229

44. Apparatus for measuring the expired air. . . 237

GENERAL DIRECTlONvS.

genp:ral directions

The laboratory hours are from half past one to five
o'clock. Each student must have receipts from, the Treas-
urer, to show that the laboratory fee and the key deposit
have been paid, and each must have the following articles
before beginning the work :

Laboratory text book.

2 celuloid triangles (6-inch).

Dividers.

Flesh pencil.

Forceps with fine point.

Reading glass.

MM rule, lo cm. long.

Strong scissors with fine points.

2 towels.

Tube of office paste.

2 sheets of millimeter, cross section paper.

40 sheets of note paper, regulation size.

40 sheets of cardboard, regulation size.

Two students will work together, and students are
advised to choose their partners early. A list of the fol-
lowing apparatus will be supplied by an instructor, when
the two students who are to work together present the
Treasurer's receipts, and show the instruments, etc. which
are required in the course. The list is to be checked and
signed by both of the students who are to use the apparatus.
Larger, special pieces of apparatus will be supplied from
time to time when needed.

APPARATUS SUPPLIED BY LABORATORY

Division A.

Acetic acid, 10%. 2 Clamps, cabinet maker's.

Basin. Clamp, large muscle.

l-!attery jar. . 6 Clamps for rods.

Board for frog. Coil, aluminum.

Brush for salt solution. Cloth to cover apparatus.

Two cells, dry. Dropper.

Clamp, burette. Drum square.

XX

GENDRAI^ DIRKCTIONS.

Electrodes, boot form in dish.

Electrode, brass.

Electrode, heart.

Electrode, pin.

Electrode, platinum.

Electrode, sheet of copper.

Filter paper.

Finger piece, wooden.

Fork and yoke.

2. Glasses, drinking.

Glass dish for salt solution.

Glass slide on support.

Hook for frog.

Hooks, pin.

Induction coil.

Key, mercury.

Key opener.

Kymograph and drum.

Lever, heavy.

Lever, light.

Ligatures.

Moist chamber with two clamps.

2 pads, gauze.

Pins.

Plate.

Pulley.

Rod, glass, with clips for boots.

Rod, L, nickeled.

Rod, screw in end.

Rod, zinc.

Rubber band, large. .

2 Rubber bands, thin.

2 Signals, electric.

Spring, steel, with pointer.

Stand, long.

Stand, short.

Sodium chloride, 0.6%.

Sulphuric acid, o.i%.

Thread, silk.

20 Weights, 10 gram.

1 Wire, insulated, extra long.
4 Wires, insulated, medium.

2 Wires, insulated, short.
Zinc sulphate.

2 Zincs for electrodes.

Division B.

Board for frog.

Brush for salt solution.

Cell, dry.

5 clamps, for rod.

1 Clamp, cabinet maker's.
Cloth to cover appratus.
Coil, aluminum.

Drum square.
Electrodes, pin.
Filter paper.
F'ork, with yoke.

2 Glasses, drinking.

Glass dish for salt solution.

2 Hooks, pin.

Induction coil.

Key, mercury.

Key opener.

Kjanograph with drum, 4 fans.

Lever, light.

Lever, heavy.

Moist chamber with clamp.

Pins.

2 Pinch cocks.

Plate.

2 Pneumographs.

Rod, L, nickeled.

2 Rubber tubes, with glass Ts.

Signal, electric.

Sodium chloride, 0.6%.

Spring, steel, with pointer.

Stand, long.

Stand, short.

Tambour, carotid with spring.

Tambour, radial.

2 Tambours, recording.

Thread,- silk.

20 Weights, 10 gram.

5 Wires, insulated, long.

2 Wires, insulated, medium.

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.

GENERA!. DIRECTIONS. XXI

THE BUEEETIN BOARD

The bulletin board near the door of the main laboratory-
is arranged as follows : Horizontal lines give the work of
the successive days, each of these being marked with the
number of the day in the course, and the date on which
the work is to be done ; vertical lines enclose spaces headed
by the two desk numbers of the pair of students who work
together. The numbers of the experiments are marked on
colored cards in these spaces. Reference to the board will
show on what day each of the experiments is to be per-
formed. The colors of the cards correspond to the colors
of the cards placed at the top of the board, giving the
names of the instructors, and show to whom the notes and
records of the experiments are to be given.

METHOD OF WORK

Each student is expected to perform each experiment,
and to make out a full report of the results, accompanied
by graphic records which he himself has obtained, when
such were demanded by the experiment. He must be pre-
pared to be quizzed on the experiment at the time it is
made, and to pass an examination both on the methods em-
ployed and the result obtained, at the end of the course.
Before leaving the laboratory, the student must see that
his desk is clean and neat ; that all apparatus is dry ; that
the battery has been disconnected fit is not enough to leave
the key open) ; that all apparatus is covered. Care must
be taken not to injure stools or desks. Of course any
apparatus which is injured by a student must be replaced
or paid for.

Do not begin an experiment until \<ou hare read the
directions in the notes, and have clearly in mind the object
of the experiment.

EXPERIMENT 1.

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 imderstand 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 with pointer (E)
and heavier muscle lever (B) on
^_U_^^ the longer iron stand, with sup-

porting screw (C) down, as shown
in diagram. The stand holding
the recording instruments should
alwa3^s be placed to the right of
the kymograph, so that these in-
struments shall point in the direc-
tion that the drum revolves. The
clockwork turns the drum clock-
wise, and when it is turned by
hand it should be rotated always
in this direction. 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 appa-
ratus on the stand. Fasten two pieces of thread to the writ-
ing lever at the hole second from the axis, and attach one of

Fig. I. 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, F, clamps.

2 EXPERIMENT I.

the threads to the spring 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 kymograph, fasten a
sheet of glazed "curve paper" smoothly around 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
iever writes an arc on a curved surface. If barely touching
when horizontal, it will leave the surface and fail to write
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 (A)
is indicated in the diagram.

Experiment. — Turn the drum by hand in a clockwise
direction to draw a base line 8-10 cm. long. Turn it back
(taking care not to injure writing points) to the starting
point and mark the place by touching the lever lightly. Now
turn drum clockwise Yi 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 J^ cm. once more.
The writing point has now recorded the curve of extensi-
bility of the spring. To obtain curve of elasticity, turn
drum Yz cm. in same direction and remove one weight, and
continue in this manner until .all the weights are off, then
turn Y^ cm. once more, and mark point by touching lever.

The vertical distances recorded on the drum should be of
equal length. If they are not, try to account for the error.
Since steel is perfectly elastic, the writing point should
return to the base line. If it does not, try to account for the
difference.

KLASTICITY OV STEEf, SPRING.

MOUNTING OF CUUVKS.

Using the two triangles and a needle, or other instrument
with a sharp point, draw a rectangle about each record
worth preservation. It is desirable to leave a generous mar-
gin about the curve. Cut out piece thus outlined, and mount
on the cardboard by gluing 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 Avhich
the notes concerning the experiment have been written.
Let the right hand end of the sheet overlap the cardboard
slightly, and fasten it to the back of the cardboard with
paste. Do not write on cover paper when it is over a curve.

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 desk
number, and the number of each of the experiments mount-
ed 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 which 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 v^^hich you know to be usually obtained in
similar cases, try to explain why the difference 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.

lil.ASTlClTY OF STEEI, SPRING.

KXPERIMENT I.

ELASTICITY 01- FROG'S MUSCI.E- 7

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.

METHOD OF KILTING FROG.

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. The cut should fall at the back
of the tympanic membranes, (See E, Fig. 9). In making
the cut, hold frog, head down, over a plate. Cut off hind
legs close to body. As there is a possibility 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.

muscle preparation.

Remove the skin from the leg, and put leg on piece of
filter paper moistened with physiological salt solution. Clean
ofif the thigh muscles from femur without injuring tendon of
the gastrocnemius muscle. Cut tendo-Achillis below ankle
and separate gastrocnemius from tibia. Remember that you

i\;xpe;riment II.

are not in the dissecting- room, and that you are deahng- 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. ExPF,RiMi:N'r. — 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 lo seconds, in order that any delayed efifect
of the change in load may be recorded in the proper place.

After removing last weight and
waiting lo seconds, if the writing
point has not returned to the
base line, turn drum again and
wait one minute, repeat until lev-
er ceases to rise or base line is
reached. Plot the curves of ex-
tensibility and elasticity of mus-
cle. If several curves are taken
with the same muscle, keep them
all and label i, 2, 3, etc. Explain
in your notes the differences ob-
served.

b. Plotting 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 section 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, writing grams
at end of line. Place along the vertical axis (the ordinate)
at equal distances the numbers 0-5-10-20, etc., to represent
the number of millimeters through which the writing point
moved, writine mm, at the head of the column. As the

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

ELASTICITY OF FROG S MUSCLEJ. 9

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,
and the millimeter rule the exact height of each movement
recorded. It is usually best to make the measurements all
from the base line. The amount of the individual move-
ments can be obtained by subtraction. Give these measure-
ments 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 • corresponding to the weight, and the horizontal line
corresponding to the height of lift. Now surround each dot
by a little circle and connect the circles by straight lines.
Mount the plotted cun^e at the side of the original. How
does extensibility differ from elasticity? How do the curves
obtained from muscle difi'er from those obtained from a
steel spring? How do the successive curves of elasticity
obtained from the same muscle differ? Explain.

IC EXPERIMENT II.

ELASTICITY OF FROG's MUSCLK. II

J 2 KXPERIMKNT II.

KHSPONSE OF MUSCLE TO INDUCTION SHOCKS.

EXPERIMENT Til.

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

T^i^

Fig. 3. Apparatus for recording contractions of frog's rnuscle, excited by in-
duction shocks. A, pin electrode ; B, primary coil ; C, C, posts i and 2 ; D, dry
cell ; F, 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. Xow suspend ten grams from the lever. To obtain

14 DXPERIMUNT III.

good results it is necessary to observe the following direc-
tions :

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 closure of primary circuit.

Some Facts Regarding Induction 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 \vire of the secondary coil, and consecjuently the battery
current does not enter the secondary coil. The current
which is used to excite the muscles 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-

RESPONSE OF MUSCLE TO INDUCTION SHOCKS. 1 5

duced currents as the primary coil is approached ; a move-
ment of a milHmeter when the secondary is close to the pri-
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
two coils approaches a right angle.

I'Vhy is the making, -weaker than the breaking induction
shock f 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 oppo-
site 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. AV'hen 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). 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 contraction. The stimulus is sub-mini-
mal. Gradually turn the coil to strengthen the induced cur-
rent, 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 it towards the primary, at

l6 KXPEKIMENT III.

which a small contraction will result. Notice that the con-
traction occurs on breaking the circuit and that no cor-
responding making contraction is seen. Now give muscle
a rest of Yz 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 contraction 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 contraction, and then, y^ cm. apart, a series of
breaking contractions obtained by stimulating with gradu-
ally increasing stimuli. In stimulating, make the circuit,
wait 5 seconds, then break, and wait lo seconds. If the
stimuli are given too rapidly the irritability of the muscle
will be raised. Soon a contraction will appear when the
circuit is made, but smaller than the breaking contraction
that goes with it. If the secondar}^ coil has not been moved
too rapidly this first making contraction will be nearly mini-
mal. After a minimal making contraction has been obtained,
continue stimulating and recording as before. After a time
the breaking and making 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 con-
tractions may be seen, and supra-maximal contractions
be recorded. Mark on the record to indicate which con-
traction is a minimal break, a minimal make, a maximal
break and a maximal make.

h. Use of Short Circuit Key.

Move drum a few centimeters, then slide secondary coil
to a position which excites making contractions about half
as high as the corresponding breaks, and record four mak-
ing and four breaking contractions, stimulating with same
time intervals as in part a, but with the strength of current
unchanged. Move drum a short distance, close the short cir-
cuit key and stimulate : no contraction. Two paths are now
open to the current, and the current is divided between them
in inverse proportion to the resistances. The muscle, hav-

RESPONSE OE* MUSCLE TO INDUCTION SHOCKS. 1 7

ing much greater resistance than the metal of the short
circuit key, gets so little current that the stimulus is sub-
minimal. This method of dividing the current is technically
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.

EXPERIMENT III.

RESPONSE OF MUSCJ^F, TO INDUCTION SHOCKS. 19

20

IJlXPERIMENT III.

CURVE OF WORK.

EXPERIMEXT 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 supporting screw
must be carefully adjusted so that the whole height of each
contraction shall be recorded. Make note of the amount of
magnification. Have 20 ten-gram v/eights readv for use.

a. Experiment. — Place muscle in moist chamber, and
make electrical connections as in Experiment 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
maxim.al breaks at intervals of
15 seconds, and cut out the
makes with short-circuiting
key. Record on the drum at
distances of j^ cm., the con-
tractions obtained with o, 10,
20, 30, etc. grams, and contin-
ue the addition of weights un-

Fig. 4. Curve of lift and of ., , , ,

work. A, curve of lift; B, curve tli the mUSClC Cau UO lougcr

°^ ^°^^- lift the load. The muscle

should be able to life 70 grammes. If more than one ex-
periment is made with the same muscle, state the fact, since
fatigue will modify the results. The "absolute power" of
the muscle is measured by the weight which the muscle
just fails to lift and which cannot stretch it when contract-
ing.

30

\

so
10
0

^'\

A.

\^

\" '•

/gems

200

too

\

\

./
/

6(IQ

B

22 . EXPERIMENT IV.

b. Plotting of Curves.

State in tabular f omi on the cardboard, by the side of
the original curve, the recorded height of lift, and the ap-
parent work done by each of the contractions, (the work
being the product of the height times the weight lifted),
and the actual work, which is obtained by dividing the
figures of the apparent work by the magnification of the
lever.

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 the curve of
lift, showing the heights of the contractions, — the ordinates
representing the distances through which the weight was
moved and the abscissas the weights. Plot below the ab-
scissa line the curvT 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 ex-
ample. 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, as shown
in Fig. 4.

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

cuRvn; OF work.

23

24 EXPERIMENT IV.

FATIGUE OF HUMAN MUSCLE. 25

EXPERIMENT V.

Fatigue of Human Muscle.

Apparatus. — Many interesting facts concerning the
fatigue of human muscle and the conditions on which it
depends have been ascertained by the use of the ergograph.
The effects of fatigue have been studied by i, letting the
muscle bend a stiff spring, the movement of which is greatly
magnified, i. e., by the isometric method; 2, by letting the
muscle raise a weight, i. e., the isotonic method. Several
forms of apparatus are in use in the laboratory, and each
is accompanied by directions. In the following experiments
the isotonic method will be used. Apparatus for the iso-
metric method will be provided if desired.

Experiment. — Connect a time signal with the clock
circuit and adjust it to write below the writing point of the
ergograph. Be careful that the hand is securely fixed, so
that the work shall be done only with the group of muscles
which are supposed to be used, and that it is comfortable,
so that painful sensations shall not interfere with the work.
Throughout the work, watch the metronome, and raise the
weight and lower the weight rhythmically, taking care to
maintain the rhythm. Always try to raise the weight as
much as possible. Unless a maximum effort is made each
time, the experiment is worthless. If the abductor of the
index finger is to be used, a weight of 500 to 1,000 grams
may be employed, the amount varying with the strength of
the individual and the apparatus. In case the flexors of the
second finger (the sublimis, profundus, and lumbricales)
are to be used, two to four kilos can be employed.

a. Effect of Sloiv Rate.

The muscles are to contract at the rate of once in
two seconds. Adjust the metronome for the required
rhythm, and see that it is wound up. Arrange the

26 EXPERIMEJNT V.

drum to run at the rate of 2 mm. per second. Start
metronome ; raise weight while the metronome pointer
swings in one direction, and lower it quickly when it swings
back. Make a few contractions to catch the rhythm ; rest
a minute ; then, being careful to maintain the rhythm
throughout, and ahvays raising the weight as high as pos-
sible, record the contractions for two minutes.

b. Bifect of Quick Rate.

Rest 3 minutes. Adjust metronome to beat seconds,
then repeat the work, raising the weight during one-half
second and lowering it quickly. Work until the weight can
not be raised.

c. Effect of Rest.

Rest 3 minutes and repeat work.

d. Effect of Massage.

Rest 3 minutes, and during the rest, massage the muscles
vigorously. Repeat the work.

In your notes state the length of time during which the
weight could be raised and the character of the fatigue
curve,- — i. e., the way in which the height of contractions
altered. The amount of work could be estimated if desired
by adding the height of the separate contractions and multi-
plying by the weight lifted. Explain results.

IfATIGUr; OF HUMAN MUSCLl];. 27

EXPERIMENT V.

TIME RFXATIONS OF MYOGRAM. 29

expf:riment vl

Time Relations of Myogram.

The record of a sing'le 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 detennined with a tuning fork.

a. Influence of Rate of Drum on Form of Myogram.

There are today a great variety of methods for obtain-
ing graphic records of physiological processes and the
changes which they undergo under normal and pathological
conditions. In many cases these records are taken on mov-
ing 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, in-
stead of being opened by
hand, is to be opened auto-
matically by the drum when it
is revolved. That this may
be done, fasten a frog board

Fig. s. Apparatus for automatically ^y its irOU rod tO clamp On

exciting muscle by letting the drum cf,ot-t stanri Plarf- tpv in

open the key. A, frog board ; B, cabi- ^ " ^ SiaUQ. ± laCC Key m

net maker's clamp; C, mercury key; primarv cirCUit OU the board,
U, handle of key; E, key opener; , ' . .

F, wires to primary circuit ; G, tuning SO that it prOJCCtS for tWO-

""^ ' ' ^° ^" thirds of its length beyond it.

and clamp key to board by a cabinetmaker's clamp. Adjust

G

30 EXPERIMENT VI.

board so that top of key is just above the level of the top
oi the drum. Clamp the key opener to the top of the drum,
so that it projects a couple of cm. beyond it. Now move
the key just near enough to enable the key opener to open it.

Experiment. — Blacken a drum ; bring key into position
to be opened w^hen 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
be after-loaded zvhen thread is tense and the lever is hor-
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 wall point away from it. Now place stand
so that the lever will write well upon the drum. Close key
in primar}' circuit and then open short-circuiting key. Now
open key in primary circuit by rotating drum by hand very
slo7i'ly. A breaking contraction 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 myograms obtained differ. Save the
muscle to test the apparatus in part h.

h. 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,
using a drum-square for this purpose. Mark the position on
the drum by moving each point. To be sure that these
marks shall be recognized make a little cross over each of
them. Save the part of the curve showing the relative po-
sition of the points.

This method should be employed in all experiments in
which time relations are important.

TIMU RELATIONS OP MYOGRAM. 3I

ExPERrMENT. — The latent period, the duration of the
period of rise and of the period of fall, are all longer for
a fatigued than for a fresh muscle; it is therefore best to
test apparatus with muscle used in part o. 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 too often and call out as few con-
tractions as possible. 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 hori-
zontal when resting on its support with thread tense. Then
move long stand so that fork and muscle lever will write
lightly on drum. If now the drum is revolved, the mer-
cury key will be opened when the muscle lever is at a cer-
tain point on the drum surface. To find what this point is,
with short circuit key closed, close mercury key ; then open
short circuit key, and open mercury key by revolving the
dnmi very slozvly. The recorded myogram should be almost
a single line. The contraction of the muscle v/ill mark the
point of drum which was opposite 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 off of fork and immedi-
ately open mercury key by revolving drum rapidly. Stop
drum at the close of one revolution. Tf 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 Computation of Time
Intervals.

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 recorded contraction
the line MM, perpendicular to the base line. To fix the point

32

EXPERIMKNT VI.

at which the second contraction began, draw on the curve
two fine parallel lines, one just aboA^e 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 thousandths of a second. One double
vibration of the fork, measured from the crest of one vibra-
tion to that of the next, is one hundredth 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 bv the number of millimeters in the

Fig. 6. Method of preparins
termination of latent period.

myogram for de-

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

To determine the period of contraction, draw TO 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 to Q to the base line at S, draw the perpendicular
UV through S, and estimate the number of thousandths
of a second between 0 U. To do this count the complete
waves, and estimate in tenths the fractions of waves. The
line UV must not be drawn through 0, 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 A^.

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

TIMF. RELATIONS OF MYOGRAM, 33;

04 EXPCRIMKNT VI,

GENESIS 01" TETANUS.

35

KXPERIMENT VII.

Genesis of Tetanus.

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 ;
D, dry cell ; E, bare end of insulated
wire turned back on itself.

Apr.ARATus. — 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 folloAvs :

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. NoAV 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 primaiy circuit will he made,
and if the wire is drawn across the coils, a series of making
and breaking shocks will be given.

a. Sinnmation of Two Contractions.

If two stimuli reach a muscle at a sufficiently short inter-
val the second contraction process may begin before the
first one is complete. 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 III ; place drum so that lever

_36 EXPERIMIJNT VII.

will record well. Open short circuit key ; with the drum
still, excite the muscle by drawing free end of wire con-
nected with battery across the last turn of aluminum wire
on block (Fig. 7, 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 rate as to cause two separate
contractions ; repeat several times, and more quickly each
time, until the two contractions look like one. 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. Tn 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 approxi-
mately the numher of excitations per second required to
tetanise. Do not forget that an arc must be drawn. A
complete tetanus is an apparently continuous contraction
produced by a series of excitations. All voluntary contrac-
tions are tetani.

■ c. Complete Tetanus Obtained zvith AutomMtic Interrupter.

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

GENESIS OF TETANUS.

37

Electrical Connections m Primary Circuit of Induction

Apparatus.

Two kinds of coils are in use. 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 primary circuit
are connected with the primary' coil and the automatic in-
terrupter is different in these two forms of apparatus.

MODEL B.

Fig. S. Scheme of electrical connections of primary coil in two forms of in-
duction apparatus. A, soft iron wires in primary coil; C, 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
I and 3.

Model B — I'o 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 directly
attached. If a long series of rapidly following shocks are
needed, as for tetanus, the batterv 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,

38 EXPERIMENT VII.

passes to contact screw, down the spring, through the coil,
and away by post 2.

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-screAv is screwed up until it barely
touches the spring when at rest.

HxPEKiMENT. — 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
clockv/ork (quick speed) ; open short-circuit key for a few
seconds; the 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 with the
same muscle and 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.

e. Fatigue of C 011 tinned Voluntary Contractions.

In the case of voluntary muscular contractions of the
arm, as the final step of the brain processes which result in
the effort, the cells in the motor arm area, anterior to the
fissure of Rolando, become active and send stimuli to the
anterior horn cells in the gray matter of the spinal cord,
and they discharge nerve impulses at a rapid rhythm, which

GENESIS OF TETANUS. 39

cause the muscles to be tetanized. By continued voluntary
contraction fatigue shows itself in much the same manner
as in the above experiment.

Test this by raising the left arm to the horizontal po-
sition, and trying to hold it there. Gradually the arm tends
to fall and stronger efforts must be m.ade to bring it back
to, or hold it in the horizontal position. As fatigue comes
on. painful sensations, not at first noticed, come from the
muscle sense organs. It is not necessary to carry the ex-
periment to complete fatigue. Describe the result of your
experiment. State where the fatigue probably occurred,
and vour reasons.

40 EXPERIMENT VII.

GENUSIS OI^ TETANUS. 4 1

42

1<,XP!'.!^TMF,NT VII.

RATE OF TAPPING. 43

EXPERIMENT VIII.

Rate of Tapping.

The apparatus permits a determination of the greatest
speed with which it is possible to make a series of brief
voluntary contractions (tetani) of a muscle.

Apparatus. — Adjust a drum to the pointer of a time
signal and the recorder of the apparatus, which is held in
contact with the surface by a delicate weighted thread. Con-
nect the time signal to the clock, so as to record seconds.
Carefully pull the cross-needle down as far as possible. Place
the arm on the board and practice tapping the Morse key,
being careful to use a wrist movement only, and saving time
by moving the hand through very short distances. Each tap
causes the cross-needle, operated by the clockwork, to rise a
definite amount.

ExPKRiMENT. — With cross-needle down, start the drum
at a rate of 2 mm per second and begin tapping; keeping
this up at a steady rate till the cross-needle reaches the
upper stop. Try this for the right and left hand. Now
figure the number of seconds required to tap 234 times (the
number necessary to make a complete rise of the cross-
needle). Determine the number of taps per second for
•each hand. Notice in the record the failure to tap when the
rate became too rapid. What was the cause? Discuss the
physiological value of the experiment.

44

expi;rime:.nt viii.

RATE OP TAPPING. 4^

46 EXPERIMENT VIII.

INDEPENDENT IRRITABILITY OE MUSCLE. 47

EXPERIMENT IX.

Independent Irritability of Muscle.

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

Experiment. — Kill a frog by pithing the brain in
the presence of an instructor. (Method will be demon-
strated.) Have a pointed match ready, and as soon as pith-
ing needle is withdrawn plug the skull cavity through the

foramen magnum, to prevent

/^'^X > loss of blood and to insure de-

// V X ,.-■'* struction of the brain. If the

/(7 Z/^'' V)A'''^ brain has been destroyed, the

ly JCJpU-'l^.-A- '' frog will not raise its nose

[J Vp^r .VJ... p from the plate, and will not

y_y ^VA— ^^^^X^ P make spontaneous movements,

I'l— -- _g although it will make reflex

Fig. g. Relation of brain to movcments if it be cxcited.

skull of frog. A, cerebral hemi- g^t the skin OU the back of

spheres; B, eyes; C, thalamen- i • i i • i- n

cephaion; D, optic lobes; E, left thigh longitudmally, separ-
benum'':'''G!^^rredX'obTongau^^ atc the Semimembranosus from
H, spinal cord. l-j^g ileofibularis muscle, and ex-

pose the sciatic nerve, (see Eig. lo. Dorsal View). Care-
fully separate a portion of the nerve from the surrounding
tissues without injury 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 including all
the structures of the limb except the ner\'e, (See Fig. ii).
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

HXPKRIMKNT TX. -

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,
and that a stronger stimulus causes a contraction of the
muscles of both legs. Do not excite more strongly than is
required to produce the effect.

As the drug takes effect, the ability of the right leg to re-
spond to such irritation gradually becomes less, and after
20 or 30 mintes it ceases altogether, although the left leg
will respond as before. Notice especially whether a crossed
reflex movement occurs in the left leg after the right leg is
paralyzed.

VENTRAL, VIEW DORSAE VIEW ;

Eig. 10. Dissection of right leg of frog. A, sciatic plexus; B, cruralis
sartorius ; D, gracilis magnus ; E, gastrocnemius ; F, glutaeus magnus ;
sciatic nerve ; H, llio-fibularis ; I, semimembranosus.

G,

When all the body but the left leg has become com-
pletelv paralyzed, open the abdominal cavity and remove
the vicera, care being taken not to injure the nerves behind
them, (see Fig. 10. Ventral View\ Cut the body in two,
leaving the last two vertebrae connected with the legs. Split
these vertebrae lengthwise, and holding the fragments with

INDEPENDENT IRRITABILITY OF MUSCLE.

49

forceps, dissect out the sciatic plexus supplying" the hind
legs. Do not take hold of nerves with forceps, and avoid
stretching- them. Stimulate the plexuses in turn with the
tetanizing current. What is the result? Now apply the
stimulus directly to the muscles of the legs. What is the
result ?

Keep the preparation, to use in
Experiment lo, which should immedi-
atety follow this one.

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

How did the drug reach the leg?
Does curara poison nerve fibers?
Does it poison muscles ?
What does it poison?
Can curara paralyze before it pro-
duces anaesthesia, that is, when the
sensory nerve endings, fibers and cen--
tral nervous mechanisms are capable
of functioning?

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

i^/ihj

Fig. II. Diagram to
illustrate effect of curara.
The shaded portion shows
the parts affected by the
drug. Iv, ligature sur-
rounding the whole of
leg, except the sciatic
nerve ; R, P, right sci-
atic plexus ; L, P, left
plexus.

50 IJXPKRIMENT IX.

INDEPENDENT IRRITABILITY OF MUSCLE. 5 1

^2 EXPERIMENT IX.

ISOLATED CONDUCTION IN MUSCU:.' 53

EXPERIMENT X.

Isolated Conduction in Muscle.

Although the separate fibers of a striated muscle are in
close contact, they are like the nerve fibres in a nerve trunk,
independent mechanisms. If a fiber is excited, the condition
of activity which is aroused runs the length of the fiber
in either direction from the point of excitation, but does
not spread to neighboring fibers. This fact can be demon-
strated most readily on a curarized muscle, and by employ-
ing unipolar excitations.

Apparatus for Unipoi,.ar 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 second-
ary coil may be left free, or, if a strong current is needed,
be connected with a gas pipe and so with the earth.

Experiment. — Remove the sartorius muscle (see Ven-
tral View, Fig. lo), from the curarized leg of the frog
used in the Experiment IX. Lay the muscle on the copper
plate. Start the automatic interrupter and lightly touch one
edge of the muscle for a moment with the point of a needle
or other metalic instrument with sharp point. The muscle
will be seen to contract along the edge that is touched and
to curl toward that side. If the other edge is touched, the
muscle fibers 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. By this method of unipolar
•excitation the current does not flow in a circuit. The cur-
rent enters the muscle wherever it is in contact with the
copper plate (the indifferent pole), but being diffuse fails
to excite it ; 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 excitation at

54 KXPERIMENT X.

that point. The strict hmitatioii 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 IN MUSCLE. 55

56 EJXPEJRIMENT X.

CONTRACTIONS OF NON-STREATED MUSCLE. 57

EXPERIMENT XL

Contractions of Non-Striated Muscle.

Apparatus. — Set up apparatus like that used in Experi-
ment ITI, and in addition mount two electric signals so as
to write in the same vertical line as the lever. Connect one
signal in the primary circuit, to mark the time of stimulation,
and the other in the clock circuit to record seconds. Because
of the resistance of the time signal, and the fact that smooth
muscle reacts poorly to currents of such brief duration as
induced currents, it will be necessary to use two dry cells
in the primary circuit. No weight should be used on the
lever.

Experiments. — Kill a frog, remove the stomach, cut
off from stomach a ring 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. Suspend the
light muscle lever from the ring by means of a pin hook.
Stick the pin of the pin electrode through the lower border
of the ring. 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. — 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 oi the rise of the
curve. Remember that non-striated muscle is very readily
excited by mechanical stimuli and that its power to keep in
tonic contraction is much greater than that of striated
muscle. If the ring is drawn together, wait for the muscle
to relax before exciting it. Watch tO' see if relaxation is
taking place.

58 b;xpe;rime:;nt xi.

b. Rate Required to Tetamse. — Set the drum turning
slowly and find by experimient slowest rate of stimulation
which will tetanize non-striated muscle. In order to tetanize,
a second contraction should be called out a short time be-
fore 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 exci-
tation.

c. Spontaneous Contractions. — Set the drum to run
at the rate of i mm. per second or slower, and record a
series of spontaneous contractions. Let 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? For comparison state in the notes the values ob-
tained in experiments VI and VII. What was the rate of
the spontaneous contractions?

CONTRACTIONS OP NON-STRIATED MaSCI,E. 59

6o E^XPERIMENT XI.

WAVK OF CONTRACTION IN FROC/s HKj\RT.

6i

EXPERIMENT XIT.

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

Apparatus. — Set up as shown in Figure 12, except for
electric signal which wall be used only in Experiments XIV
and XV. Clamp horizontally on short stand, the nickled
rod with hole for wire and binding screws 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) earning the lighter
muscle lever. 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

Fig. 12. Apparatus for recording the beat of a frog's heart. A, horizontal
rod carrying binding screw for wire ; B, vertical rod carrying lever ; C, yoke
supporting axis of lever ; D, time signal ; IJ, wire, connecting lever with button
to rest on the heart ; F, piece of flexible insulated wire, connecting short piece
of wire, passing through button, with binding post on frog board; G, frog
board.

62 EXPKRTMENT .XII.

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 v^^hen 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. Connect
the steel wire (B) of the heart electrode with the lever.
The hole into which it must be inserted will depend on the
size of the movements of the heart. The record of the
movements should be not less than a centimeter in height.
Fasten the piece of flexible insulated wire (F) to the bind-
ing po'St 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.

Opj^ration. — Choose an active frog; pith brain as de-
scribed in Experiment IX; cut off the projecting end of
the 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 a centimeter above pubis to
one-half centimeter below jaw. Raise ensiform cartilage
with forceps, and with sharp scissors remove sternum, al-
ways keeping point of scissors well away from the pericar-
dium and aortae. In cutting through the abdominal wall
avoid the large vein. Now slide the heart lever up
out of the way, and place the frog on the frog board so
that its ventricle lies directly beneath the 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.

a. Gross 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 (//) and the two aortic arches
(A) ; the relation of the two auricles (B, C) to each other

WAVD OF CONTRACTION IN FROG's HF,ART.

63

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

Ventral View

Fig. 13. The gross anatomy of frog's heart. (Ventral view after Cyon, dorsal
-view after Howes.) A, aortae ; B, right auricle; C, left auricle; D, pulmonary
vein ; F, ' ventricle ; F, sinus venosus ; G, sino-auricular valves ; H, bulbus
.arteriosus.

b. Origin and Course of the Wave of Contraction.

T. — Inspfction. — 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.
The change of color begins somewhat later than the process
causing it. Answer in your notes the following questions:
What is the action of the auricles during the ventricular
diastole, and during the ventricular systole ? What changes
are observed in the ventricle during auricular diastole, and
during auricular systole?

2. — Thf Myocakdiogram. — Adjust the button 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 button are in contact with

64 EXrHRIMENT XII.

the ventricle, and that the button does not touch the auricle
so as to be moved direct!}- 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. ]\Iark on the
record the part of the cardiac cycle which is responsible for
each wave of the curve. Xotice that the lever records at
the same time changes in the position, form and volume of
the ventricle. How and why does the beat of the auricle
show in the curve? AMiich part of the curve was made by
the ventricular systole? Does the lever fall or rise in the
ventricular diastole? Explain.

WAVK OF COXTRACTIOX IX PROG S HEART.

65

66 liXPERIMUNT XII.

Et'FECT 01^ TEMPERATURE ON HEART RATE. 67

EXPERIMENT XIII.
Effect of Temperature on Heart Rate.

a. Effect of Air.

Pith a frog, and expose the pericardium. Count the
heart rate. Role up a tube of paper round a pencil, and using
the tube, warm the heart by slowly breathing upon it, and
observe the change in rate. After the new rate has become
established, place the end of the tube close to the heart, but
without touching it, and suck air over the heart. Note the
rate of beat.

h. Effect of Solutions.

Let the heart take on the temperature of the room,
and then after counting the rate, place the frog on his back
in a shallow tray, and cover the heart Avith salt solution
heated to 30° C. Note the rate. Replace the warm solu-
tion, by cold salt solution, 10° C, and when it has had
time to cool the heart, again record the rate.

Put the figures which you obtained in your notes, and
explain the effects observed. If the heart is beating well
at the close of the experiment, dry it off and use it in
the next experiment. The tray must be cleaned and dried
before it is returned.

«8

EXrERi:MEXT XIII.

EfFECT OF TEMPERATURE OX HEART RATE. 69

70

i;xrKRiMKNT XI I r.

REFRACTORY PERIOD. 7 I

EXPERIMENT XTV.
Refractory Period and Compensatory Pause.

ApparaTus.^ — ^The same apparatus for recording the
contractions of the heart may be used as in Experiment
XII. In addition arrange an induction coil to give single
shocks, and connect a time signal in the primary circuit.
Adjust the signal 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, usually gives sufficient
strength of current. Avoid using a current stronger than is
required to call out an extra contraction, otherwise the cur-
rent will spread to the muscles of the trunk. One of the
w4res of the secondary coil is to be fastened to the binding-
post on the frog board, and to be brought into communica-
tion with the ventricle by means of the fine insulated wire
passing to one of the pins in the button which is to rest on
the ventricle (see Fig. 12) ; the other wire is to be fastened
in the horizontal rod supporting the heart lever, through
which it communicates with the heart.

In order that the curve may be read with accuracy,
three things are essential, viz : — the length of the lever
must he knozmt, the relative position of the writing points
must he marked on the drum, and a hase line must he
drawn with the lever horizontal. If the mark which shows
the position of the leA^^er is a long arc, it can be used to
determine whether the base line was properly drawn, and
if it was not, to establish a correct base line. The relative
position of the writing points must be recorded on each
curve at the beginning or end of the experiment. A cross
can be written over each of the marks to identify them,.

Experiment. — ^Adjust lever to heart and place drum
so that contractions will be recorded. Leaving drum in
this position, turn yoke at axis so that it will support lever
horizontally. Rotate drum to give base line, and at beginning

72 E^XPBRIMKNT XIV.

of curve mark a large arc by raising" lever, and mark position
of time signal. Lower yoke and make experiment., Let
the drum run at the rate of 20 mm. per second ; and 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 ven-
tricle, and early and late in the diastole of the ventricle.

State in notes in which case the stimulus produces no
effect (the "Refractory Period") ; and when an extra con-
traction. State relative size of the contractions obtained
in different parts of diastole. Notice that an extra con-
traction is followed by a pause, (the "Compensatory
Pause"). Is the pause long enough to compensate for the
extra contraction, so that the rhythm of the beat is not
changed afterward? Explain these phenomena. Was the
auricle excited by spread of current?

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
first to make sure that the lever was horizontal when the
base line was drawn. If the line drawn was not correct,
draw one at the proper height. Draw a vertical line through
the point of excitation, as given by the time signal, to the
base line which corresponds to the position of the heart
lever when horizontal, and then having allowed for the
relative position of the writing points, 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.

RrifRACTORY PERIOD.

73

74 EXPE^RIMENT XIV.

EXCITATION OF RESTING HR.ajRT. 75

EXPERIMENT XV.

iiesponse o£ the Resting Heart to Stimulation by Induc-
tion Shocks.

Apparatus. — Use apparatus the same as in Experiment
XIV and in addition mount a tuning foirk on large stand
above the electric signal. 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 adjust
the lever to the heart. Establish the position of the writing
points and draw a base line as described in Experiment XIV.
Move coil far away, and find smallest stimulus that will
cause a contraction, taking care that the current does not
excite the muscles of the trunk. Record the curve of con-
traction and beneath it the tuning fork curve, and the mo-
ment of make and break of the primary circuit, as shown
by the signal. Short circuit the make. Turn the drum by
hand at rate of about lo cms. per second, and excite by
the break. Assume that the signal records the exact mo-
ment of excitation, and calculate from the record the time
relations of the myogram, as in Experiment VI. Save a
part of the record which shows that the writing points are

76 t;xpe;rimij:nt xv.

in the same vertical line, and state in notes length of lever
in millimeters. In what respect does the myogram obtained
from the heart differ from that of striated muscle?

b. Bozv'ditch's Staircase.

Stimulate about 15 times with a medium strength of
current at intervals of 2 to 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-
frecjuent repetition of the stimulus.

c. All Contractions Maximal.

As soon as a sufficient number of myograms have been
recorded, remove the fork, and stimulate about ten times
with gradually increasing current at intervals of 30 seconds,
recording contractions on drum about i cm. apart. There
should be no increase in height of contraction due to in-
creased stimulus. Any stimulus sufficient to cause heart
muscle to contract, causes a maximal contraction. This is
often spoken of as the law of "y\ll or none." See that the
muscles of the trunk do not contract.

d. Effect of Frequent Stimidi.

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. See
that the muscles of the trunk do not contract. 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.

KXCITA'J'ION 01' RESTING IIKAJJT. 77

78 Expe;rime;nt xv.

MOTOR POINTS ON THE ARM. 79

EXPERIMENT XVI.
Location of a Few Motor Points on the Human Arm.

The few motor points surrounded by a circle in the dia-
gram (Fig. 17), 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; Ei^j?icient 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 14. Lay a small piece of

^-^^~— „^^ filter paper on a clean plate,

•* (O' '~^^__^^^7!^^ "^^ ^^^ slightly moisten it

B with only a few drops of

Fig. 14. Apparatus to detect direction ^ solution of Starch and pO-
of flow of current in a simple circuit. ...

A, dry cell; B, mercury key; C, elec- tassium iO'didc. Draw the

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 cathode. 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 with post i and cathode with post 2.

8o EXPERIMENT XVI.

Connect the platinum electrodes to the posts of the second-
ary coil. Place the ends of the electrodes on the moistened
paper and make the primary circuit, then slide the electrodes
to a fresh place and break. A dark dot will be given at one
pole on making and at the other on breaking, 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 cathode 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. Apparatus to detect direction of flow of current in secondary coil
o; an induction apparatvis. A, dry cell; B, mercury key; C, primary coil;
D, secondary coil ; E, electrode.

more eificicnt pole of the secondary circuit is the one that
is the cathode ivhen 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 key is attached or the
opposite one. Of course it must be remembered that this
will be true only when the anode of the cell is connected
with post one, as in the above test.

Preparation of vSkin. — Since the epidermis when dry
offers great resistance to the current, it is necessary to
moisten it thoroughly. For this purpose use a warm solu-
tion of common 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 for at least five minutes ; or
a pad soaked in the solution may be bound on. Unless
the skin is thoroughly moistened, the stimuli are apt to be
painful and inefficient. Do not spill the solution on tables
or apparatus.

MOTOR POINTS ON THE ARM.

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 less effi-
cient pole of the secondary coil, and a small brass electrode
(the active electrode), to the more efficient pole.

Fig. i6. Apparatus for unipolar excitation of liuman nerves. A, battery; B,
mercury key ; C, primary coil ; D, secondary coil ; E, copper plate iised as
indifferent electrode ; F, exciting electrode.

Experiment. — Locate the motor points on the left arm
first. By the motor point is meant the spot at which the
motor nerve enters the muscle, or where a nerve is most
accessible to the current. P'asten the copper plate by an
elastic band on the back of the left hand, putting a wet

Fig. 17. Diagram of location of motor points on flexor side of arm. (After
Frb.) A, median nerve in upper arm; B, flexor longus policis ; C, median
nerve at wrist ; D, ulnar nerve in upper arm ; E, tilnar nerve in groove between
the internal condyle of the humerus and the olecranon process ; F, flexor
profundus digitorum ; G, fl.exor sublimis digitorum ; H, tilnar nerve at wrist ;
I, abductor minimi digiti.

gauze pad between to prevent the metal from touching the
skin. Let your companion press the active electrode firmly
upon the skin at the point to be stimulated, and 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 breaking con-

S2 liXPERIMENT XVI.

traction. As soon as a suitable stimulus is found, try to
establish the motor points corresponding to- those marked
with a circle in the diagram. Find for 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 with-
out the sensation being painful, it indicates either that the
epidermis is not sufficiently moistened or that the right
position for stimulation has not been found.

Consult an anatomy and locate the motor points on
the left arm of each student. Mark the points on the skin.
Demonstrate to instructor, and make a diagram showing
the position of the points which you found.

MOTOR rOINTS ON THK ARM. 83

84

IXXPrCRIMKNT XVI.

ELECTRICAL EXCITATION OF HUMAX MLTSCLrE-.

85

EXPERIMENT XVII.

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

Fig. 18. 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 a 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 (C) 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 (see Fig. 19) to a muscle lever, which is con-
nected 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 thumb is fastened to the second, and that

86

EXPERIMENT XVIT.

[nj5

from the rubber band to the third hole in the lever. When
the flexor longus poUicis 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 so as to record makes and
breaks, and an indifferent and a stimulating electode con-
nected'with the posts of the secondary coil. The copper
plate (Fig. i8, D), which is to act
as the indifferent pole, is to He 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 contact with the
vertical rod on the arm rest and that
the hand does not touch the bare
copper of the plate. The active
pole (E) instead of being held
in the hand, is to be fastened
above the arm in a clamp on a hor-
izontal rod, which in turn is
clamped to a vertical rod (F),
which is supported by a clamp fast-
ened to the horizontal rod at the
side of the arm rest. This arrange-
ment permits the exciting electrode
to be fastened at any desired point on the arm.

a. Making and Breaking Induction Shocks of Various
Strengths.

ExPERiivEKN'T. — 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 re-
spect to the pulley, and the elastic band be slightly stretched.
Place drum in position. The lever should point slightly up-

Fig. 19. Apparatus for re-
cording movement of thumb.
G, rubber band supported by
L, rod ; H, recording lever ;
I, time signal ; J, puUy ; K,
thread to thumb.

KI,1^CTRICAI, EXCITATION OF HUMAN MUSCI^. 87

ward, so that when drawn down it will keep in contact with
the drum. The subject handles the key and coil while his
associate has charge of the kymograph, and turns the
drum by hand. To stimulate, close to the key, wait 2 or 3
seconds, then open and wait 10 seconds. The student attend-
ing to the kymograph should keep track of the time with
his watch and tell the subject when to stimulate. Begin
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 stimulation, 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 relaxed. Volun-
tary movements should be avoided as far as possible, and
should be noted when they occur.

b. Tetanising Current.

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

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

88 ■ EJXPERIMENT XVII.

Er^ECTRICAI, EXCITATION OF HUMAN MUSCI,!;.

90

KXPKRIMKNT XVII.

^

GAI^VANI S EIXPBRIMENT. 9 1

EXPERIMENT XVIII.
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 posterioir
part, taking care not tO' injure the
^ ^ ^ nerves. Cut the body in two trans-

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
the back between the nerve plexuses
and the urostyle, and hang the prepar-
ation by this slit upon the brass hook.
Adjust the zinc rod so that upon giv-
Fig. 20. Apparatus iug the preparation a slight swing the
n°:nt.^l'1rassTook: outside of the thigh near the knee will
zrni'rod'^ °" ^ ™'^' ^' Strike it. Set the preparation swing-
ing. Upon 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-

oD

92 EXPERIMENT XVIII.

rent, is able to excite. In the next few experiments the
effects of the direct battery current upon nerve and muscle
will be observed. Save the preparation for the next experi-
ment if made the same day.
No notes required.

GALVANl's DiXPERIMJJNT. 93

94 EXPERIMENT XVIII.

POLARIZATION 01^ ELECTRODES. 95

EXPERIMENT XIX.

Polarization of Electrodes.

a. Polai'kable Electrodes.

Apparatus. — Fasten two short wires tO' the posts inside
a rnoist 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 polarizable electrodes. Connect the binding posts
on the bottom of the moist chamber with two dry cells and
a key. Make the connections so that the current shall flow
from the carbon (-f- pole) to the electrode which will be
nearer the muscle. This will then be the anode, and the
current an ascending current, one which will pass up the
nerve, and leave it by the negative pole, the cathode, and so
flow back to the battery.

Experiment. — Make a nerve-muscle preparation from
the frog used in the preceding experiment. The method oi
making preparation will be demonstrated. Never take hold
of the nerve with the forceps, and avoid stretching it. Place
the preparation in the moist chamber, and let the nerve rest
across the two copper wires. Avoid stretching the nerve
and protect it from drying, or its irritability will be altered.
P)ring 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. Close the key and let the current
flow throngh the nerve for sixty seconds. Mark on the
dnmi the point at which the key is closed, C, and the point
at which it is opened, 0, whether a contraction occurs or not.

96 EXPERIMENT XIX.

Then disconnect the wires from the battery, and connect
both of the wires from the binding posts on the moist
chamber with the key. Immediately begin closing and
opening the key regularly, once a second. If contractions
result, continue until they cease. Notice whether the con-
tractions arc 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 character of the contraction following closing and
opening the circuit. 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 current. This current results from electrolysis
which has taken place at the points of contact of the nerve
with the wires. The condition set up at these points by the
passage of the battery current is analagous to that taking
place in a storage battery, when it is charged, and the wires
are said to be polarized. In order to avoid such disturbing
currents it is necessar)'. whenever the direct current is used
as a stimulus, to employ non-polarizable electrodes.

b. A'on-I'olaricable Electrodes.

Apparatus. — The non-polarizable electrodes used in
this course, consist of two boot-like pieces of porous baked
clay, 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
time 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
glass rod ; and fix the rod in a clamp on the support which
holds the muscle clamp, in the moist chamber. (See Fig. 21.)

rOLARIZATlON OF EI,KCTRODTiS.

97

Dry the wires just used as electrodes, and connect them
to the zincs ; with a dropper put
about half a cubic centimeter of
zinc sulphate into the boots, being
careful not to spill any of it on the
outside of the electrodes. Then in-
sert 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 non-polariz-
able, closing- and opening the bat-
ter}- circuit should give the same
effect as before, but there should
be no response to the movements
of the key after the battery has
been removed from the circuit.
On completing the day's work,

the non-polarizable electrodes must be thoroughly washed

and returned to the normal salt solution.

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

Pfluger's Law.

The polarization current which is set up, is strongest at
first and gradually fades away ; consec[uently 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 :

I. The closing excitation develops in the nerve in the
region of the cathode, and the opening excitation near the

9° £;XPERIMKNT XIX.

anode, the irritability rising- at the cathode when the current
is closed, and at the anode when the current is opened (See
Fig. 22).

2. The closing- excitation is the stronger, the rise of
irritability at the cathode when the current is closed, being
greater than the rise at the anode when the current is opened.

K

/p Q) — .V-^

TT
Open

Close
Wea/c X.

X JyTedium

SJron

^

Open A

Fig. 22. Pfliiger's lyaw. The two upper diagrams show the effect
of ascending, and descending, weak, medium, and strong direct battery
currents on the excitability and conductivity of a nerve. A, positive
pole, the anode ; C, negative pole, the cathode ; K, key ; X, stimulus
eft'ective ; O, stimulus ineffective. The two lower diagrams indicate
the irritability at the anode and cathode, when the key is closed and
the current is flowing through the nerve, and the after effect following
the opening of the key.

3. By strong currents the conductivity like the irrita-
bility of the nen.^e is lessened at the anode during the flow
of the current, and at the cathode at the instant that the
current ceases.

4. With an ascending current the anode is nearer the
muscle, and with a descending current the cathode is nearer
the muscle.

POLARIZATION OF I;r,KCTROD!'.S. 99

lOO KXPF.RIMENT XIX.

RESrONSE OE NERVE TO DIRECT CURRENT.

lOI

EXPERIMENT XX.

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
of a battery of two cells, making connections as indicated
in Fig. 23. Mount a pair of non-polarizable electrodes, in
the moist chamber, connecting the wires so that the current

— E

Fig. 23. Method of using rheocord. A, German silver
wire; B, sHder ; C, double binding post at lower end of
German silver wire; D, battery; E, key; F, nerve bridg-
ing the boot electrodes, the current being ascending.

will ascend the nerve. Observe that the current passes
down the fine German silver wire of the rheocord to the
slider (B) and there divides, part going to the nerve and
part going through the lower part of wire. At the double

I02 EXPERIMENT XX.

post (C) at bottom of the wire, the two streams of the cur-
rent unite again and pass together to the battery. Observe
that the current traversing the nerve must increase as the
sHder is moved upward, because the resistance in the wire
below the point (B) where the circuit divides is increased.
Experiment. — Since the direct current rapidly changes
the irritability 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 thfe
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 mav observe the facts tabulated as
Pfliiger's law (see Exper. XIX) ; this is not required, how-
ever.

RKSPONSr, 01' NF.RVK TO DIRF.CT CURRliNT. IO3

I04 EXPERIMENT XX.

RESPONSE OF HUMAN NKRVKS TO DIRRCT CURRENT. 105

EXPERIMENT XXI.

Stimulation of Human Nerves by a Direct Current.

Apparatus. — The electric current, which is to be used,
is supplied from a dynamo giving 60 volts.

Key G, Fig. 24, controls the flow of the current to the
rheostat. In the rheostat it is shunted, the current passing
through the resistance from P to N, and a portion of it being
led off through the metal slider H to the post PP, which
gives the branch of current to^ the arm circuit. The resistance
in the rheostat is equivalent to the German silver wire of
the rheocord used in Experiment XX.

Note that as the slider is moved clockwise^ the resist-
ance between the slider and post A^ increases and hence
more current mill so to the arm.

Fig. 24. Apparatus for stimulation of human nerves by a direct current.
G, key; P, post where current enters, and N, where it leaves rheostat; PP,
post connected with slider, from which current goes to milammeter ; H, slider ;
I, milammeter ; J, commutator for reversing current ; K, L,, electrodes ; NN,
pole on rheostat connected with N and receiving current returning from
commutator.

In flowing to the arm, the current passes through the
milammeter I, and then to the commutator J, through
which it is carried to one or the other of the arm electrodes,
according to the direction in which the bridge is rocked. If
the bridge is rocked towards the electrodes, K becomes the
positive electrode, the anode, and L the cathode ; if it be
rocked away from the electrodes, the current goes through
the crossed wires, and I^ becomes the anode and K the
cathode. In both cases the current returns from the cathode

Io6 EXPERIMENT XXI.

In' way of the commutator to the pole NN of the rheostat,
and thence to the pole N and so away.

Experiment. — When ready for this experiment report
to instructor. Two stimulating electrodes are used, one
being applied to each arm, over either the median or the
ulnar nerve near the wrist. Choosing the nerve which in
the preceding experiment gave the best results, and using
your own induction coil, ascertain again the exact points
on the two arms giving the best motor response. Mark
these. Wet the places on the two^ arms again thoroughly
by binding a wet pad, moistened with warm salt solution,
on each, and while the skin is becoming saturated, study the
apparatus. See that hands are dry zvhen apparatus is
handled. Bring slider against flat side of checking post,
and see that the key is open. Then place the arms on the
arm supports (see Fig. i8) and pressing the electrodes
firmly over the motor points, make the electrodes fast.

In making the experiment the subject sits quietly,
watches for the first appearance of sensation or contraction
resulting from the stimuli, and reports at which pole it
occurs. The other student, who is the experimenter, handles
the key and rheostat, reads the milammeter, and records the
results in a table of the following form, stating the number
of milliamperes required to produce the effect sought. The
red scale of the milammeter is the one to be observed.

table oe strengths oe current required to produce

eeeect.

Physical Anode on hand

SENSATION. CONTRACTION.

Cathode closing ,
Anode closing . ,
Anode opening ,
Cathode opening

When all is ready the experimenter closes and opens
key. There should be no movement of milammeter needle
and no eft'ect 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

RESPONSE OF HUMAN NERVES TO DIRECT CURRENT. 107

key and says "open." Experimenter must watch milam-
meter, 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 COC (cathode opening
<:ontraction), 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

Current dense
CCC I

Current diffuse

COC rar

Fig. 25. Diagram of paths taken by direct current applied to human skin
over nerve, and of place where current takes effect. _|_, positive electrode, the
physical anode, on left arm ; . — , negative electrode, the physical cathode, on
right arm; a, a, a, physiological anodes; c, c, c, physiological cathodes; I,
CCC, closing excitation where current is dense ; II, ACC, closing excitation
where current is diffuse ; III, AOC, opening excitation where current is
dense; IV, COC, opening excitation where current is diffuse.

as before. Observe that the order of appearance of CCC,
ACC, AOC, COC, 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.

To understand the results it is necessary to recall the
following facts, as illustrated in Fig. 25 :

The first letter of the ACC and AOC, refers to the
positive electrode, the physical anode (see large A), and the
first letter of CCC and COC, refers to the negative electrode,
the physical cathode, (see large C).

The second letter, C or O, refers to the closing or the
opening of the circuit. On closing the circuit, the stimulus

io8 }i;xPERiM£;N'r xxi.

is developed at the point that the current leaves the nerve,
that is at the physiological cathode, (see small c, c. c) and
on opening the circuit, the stimulus develops where the cur-
rent enters the nerve, at the physiological anode (see small

In experiment XX, you saw that the closing contractions
came with weaker currents than the opening, and the same
should be seen in this experiment, CCC and ACC should be
obtained with weaker currents than COC and AOC. There
are two places where closing stimuli might develop, at the
physiological cathodes (c, c, c), under the physical anode
(A) and at the physiological cathodes (c, c, c), under the
physical cathode (C). Since the current would be denser
where it left the nerve under C than where it left it under A,
CCC should come with a weaker current than ACC. For
a similar reason AOC should come with a weaker current
than COC.

K1':SP0NSe; 01? human N^RVIiS TO DIRECT CURRENT. I09

no EXPERIMEJNT XXI.

CURRlvNTS Olf RF^ST AND ACTION. Ill

EXPERIMENT XXIT.
Currents of Rest and Currents of Action,

a. Current of Rest detected by Rheoscopic Frog Prepar-
ation.

Apparatus. — Mount on short stand a brass L rod, and
fasten a muscle damp, 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 electrodes with the secondary coil.

Experiment. — Prepare (A) a nerve-muscle preparation,
( B) a nerve-leg preparation (a "rheoscopic frog" prepar-
ation, which consists of a leg intact from knee down, and
the sciatic nerve), and (C) a piece of thigh muscle having
one uninjured surface and one surface cut squarely across
the fibres. 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
way that the nerve of B shall fall suddenly across cut sur-
face 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 stimu-
lated by the so-called "Current of rest," the "Demarcation
current."

b. Current of Action detected by Rheoscopic Frog Prepar-
ation.

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.

112 e;xpf,rimt;nt xxit.

Stimulate nerve oi A with tetanizing current of medium,
strength. Both muscles should be tetanized.

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. No contraction of A or B occurs. A moist ligature
would not block an electric current, but by breaking the
continuity of the nerve fibers, it effectually 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 cataboHc change than others, and
hence are electrically negative as compared with the less
active parts. The nerve completes the circuit and is stimu-
lated.

cuKRn;N'rs or* rf.st and action. 113

114

EXPKRIMKNT XX [1.

re;i^i,ex frog. 115

EXPEIMMENT XXIII.
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 studying 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 betv/een the posterior and anterior
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, (see Exper. IX). Note the time
at which this is done. Place the frog on a plate, back up-
wards, 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. Now 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 zvith 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 Vv^ill move legs but not
jump; the power to perform the most highly coordinated
movements is absent.

b. 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
order in which the dift'erent parts of the leg and of the body
respond to the excitation.

ii6 expe;rim£;nt xxiii.

c. Are Reflexes Piirposefiil?

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 two
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 re-
port average for each. Immerse to the same mark each
time, as the distance affected influences the result. Wash
off the acid after each test. Where is the time probably lost?
Does the experiment favor the "neuron theory," or the
theory of a continuous nervous network?

e. Spasm of Muscles versus Cooodinated Movements.
Apparatus. — Arrange induction coil to give tetanizing

excitations. Connect a pair of electrodes with the secondary
coil.

Expi;RiMENT. — Remove frog from hook. Open abdo-
men by cutting away whole of anterior wall ; remove vicera
without injuring the sciatic plexuses behind them. 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 hook. Apply electrodes first to the
peripheral, and after, to the central cut ends of the nerves
of the plexus, taking care to use the zveakest effective tetan-
ising current and to avoid touching the electrodes to any-
thing except the nerves. Explain how the resulting move-
ments differ.

REfr.EX FROG. iry

Il8 I'XPI\R1MENT XXIir.

REACTION TIM]i TO SOUND.

119

EXPERIMENT XXIV.

Reaction Time to Sound.

Apparatus. — Blacken drum and fasten it at highest
point on kA^mograph. 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 T rod on stand above lever; put
elastic band on rod ; and connect band with lever by 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 tying 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
drum. 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 so that the lever
is pulled down and the wood
rests on table ; ( see that the
thread is vertical). He is to
remove finger as soon as he can
after hearing sound of fork. He
must not react to sound 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 sometimes about a

>=

Si,

IL^

Fig. 26. Apparatus for record-
ing reaction time for sound. A,
rubber band; B, lever; C, tun-
ing fork ; D, strip of wood,
which is to be pressed by finger
against table.

I20 . EXPERIMENT XXIV.

second later, at other times 2 or 3 seconds later, whirl the
drum ; then pull yoke off fork and stop drum as soon as
subject is seen to respond. Be sure the drum is well under
way before pulling off the yoke.

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. This
is to be done before each test. Take 10 reaction times with
each student as subject.

Reading of Curves. — Using two triangles draw a per-
pendicular from point where lever began to move, through
the corresponding tuning-fork curve. Allowing for po-
sition of the writing points, 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 10 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 second;
to a touch on the skin, 0.145 second; and to an electric
flash 0.195 second.

REACTION time; to sound. 121

122

IvXr'I'RIMF.NT XXIV.

SENSATIONS. 123

EXPERIMENT XXV.
Cutaneous Sensations and Muscle Sense.

Five types of sensation can be obtained from the sense
organs which lie close to- the surface of the human skin,
viz. : cold, warmth, pressure, tickle, and pain. Each of
these is caused by the excitation of special spots on the
skin, and presumably special types of nerve endings. The
pressure and tickle spots appear to be excited only by me-
chanical stimuli ; the spots for cold and warmth are not so
excited, the warmth spots responding to heat, and not to
cold, and the cold spots to cold, and not to heat. The pain
spots are excited apparently most readily by some form of
pressure, but also respond tO' intense heat and cold.

It is strange that the same form of mechanical excita-
tion, that caused by the pressure of the point of a small in-
strument, can awaken three different types of sensation.
The quality of these sensations, if they are at all strong is
so different, however, that they are unmistakable. The
irritability of the tickle points is very variable. When it
is slight and the stimulus is weak, the sensation is to be dis-
tinguished from pressure, in that it is mbre vivid, fixes the
attention more readily, and lasts longer; when the irri-
tability is greater, the tickle sensation is very diflferent from
the dull, short lived, pressure sensation. The peculiar burn-
ing, or tingling quality, lasting for a long time and often
increasing in intensity after the irritant has been removed,
is suggestive of pain rather than pressure. It excites an
almost irresistable desire to rub or scratch the place, and
is inhibited by strong deep pressure on the skin. The inhi-
bition is probably due to fatigue. When the surface of the
skin is at all dry, even slight pressures cause depression of a
considerable amount of surface, and frequently excite both
pressure and tickle spots at the same time, giving mixed
effects. Touch is probably a mixture of faint tickle and
pressure sensations. Apparently the sense organs for tickle

124 EIXPKRIMENT XXV.

lie slightly more superficial than those for pressure, and
the organs for pain deeper, so tickle can be awakened
by the most delicate pressures, a sensation of pressure by
slightly stronger pressures, and pain by still stronger pres-
sures. Pressure spots are closely related to the hair follicles,
lying to the windward side of the hairs, and are easily ex-
cited by movements of the hairs. Tickle, too, can often be
produced by very delicate movements of hairs, but if the
hairs be repeatedly moved, the tickle sensation often gives
place to pressure, because when the irritability of the tickle
sense organs is slight, they fatigue more rapidly than the
pressure organs. Both sensations can be obtained from
parts of the skin where there are no hairs. Pain spots are
by far the most numerous, the tickle spots come, perhaps,
next in order, then follow pressure, cold and warmth spots.
The number of the different spots to be found in a given
area of skin differs greatly in different parts of the body.
The tickle sense organs are probably our chief defense
against insects, the bites of which have been found to in-
noculate animals with many forms of disease.

Experiment.
a. Cold and Warmth Spots.

Mark with red ink on some part of the skin, free from
hairs, and convenient for study, as the volar surface of the
forearm, or the radial side of the back of the hand, a square.
2x2 cm. and divide this into four, and then into i6 squares,
by drawing fine lines. Determine on yourself the cold and
warmth spots in the large square, by gently sliding the
rounded point of a metal rod forward and back across the
surface, in such a way as to cover it completely. In seeking
the cold spots, use a cold dry rod ; and in trying to find the
warmth spots, use a dry rod that has been heated in water
that feels hot to the hand. As the rods cool quite quickly,
let one be heating while the other is being used. Mark the
position of the spots foimd, by fine blue and red crosses,
the ink being applied by a fine pointed stick. See if the cold
spots respond to heat, and the warmth spots to cold. Do
they react to pressure?

SENSATIONS. 1 25

b. Tickle and Pressure Spots.

Examine: the skin for tickle spots in an area
[ cm. square, by sliding- across it the little glass ball
on the point of a fine needle carried in the frame which
will be provided. AVhen a tickle spot has been approxi-
mately located, determine its position more exactly
by reversing the frame and lightly touching the skin with
the head of the needle. The pressure spots can be similarly
located by using a slightly heavier needle. If the skin be dry
at the time, exact localization is impossible because too large
an area will be depressed. Softening the skin with warm
water and then with vaseline is of assistance. The irri-
tability of the tickle spots varies greatly, not only with
different individuals but by the same person at different
times. Mark the points found with fine red and blue dots.
Is tickle obtained from the pressure spots, and vice versa ?

c. Pain Spots.

The pain spots are so numerous that their positions
cannot be marked except by very fine points, and by
working under a magnifying glass. I,ocate a number of
them near together, and see whether there are places on the
skin between them where pain is not felt. Use the point
of a fine needle; lightly press on the skin without punctur-
ing it.

Before writing up your notes, check up a number of
your results, to see whether the spots can be found a second
time, at the place where they were first located. A map is
to be drawn showing the position of the spots which were
located.

d. Muscle Sense.

Under this term are grouped the sensations supplied
by the dififerent nerves from the muscles, tendons and joint
surfaces. Although these sensations are ordinarily un-
noticed they are the indispensable guides for all coordi-
nated acts, being assisted by sensations from the skin.

ExP£;RiMr;NT. — i. Close the eyes; slightly separate one
upper arm from the body; flex the elbow to slightly more

126 e:XPSRIMENT XXV.

than a right angle ; partly separate the fingers. Now, with-
out looking, place the other arm and hand in the same po-
sition. See how nearly the positions correspond. Repeat,
and closely observe the sensations which you experience.

2. Close the eyes ; raise both arms at the same time,
and try to touch corresponding points on the twO' sides of
the nose at the same time, with the fore fingers.

3. Place the left hand on the right; press down hard
on the right hand, at the same time that the right hand re-
sists the pressure. Notice all the points where you experi-
ence sensations.

Report the results of the above experiments in your
notes.

SENSATIONS. 1 27

128

F.xpr.RiMRNT :xxv.

TI-IE KNJiE-JERK.

129

EXPERIMENT XXVI.

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

Fig. 27. Diagram of nervous paths followed by the nerve impulses causing
tlie knee-jerk and its reenforcements. A, hammer placed to strike ligamentum
patellae ; 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, commisural cell; H, descending path from leg
area in cerebral cortex; I, descending path from arm area in cerebral cortex;
J, motor nerve to arm.

130 EXPERIMENT XXVI.

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

Two explanations of the contraction of the quadriceps
are offered; viz: (i) The knee-jerk is a reflex act (See
Fig. 2']').. The twitch acts as a mechanical stimulus to the
sensory nerve ends in the muscle and its tendon ; the result-
ing impulse passes to the spinal cord through the posterior
spinal nerve roots, and excites anterior horn cells in the
leg areas of the third and fourth lumbar segments of the
cord ; and these cells discharge motor impulses to the quad-
riceps muscle and cause it to give a sudden, brief contrac-
tion. The response of these cells to the sensory stimulus
may be either reenforced or inhibited by other impulses
reaching them a short time before the impulses from the leg.
(2) The knee-jerk is the result of the direct mechanical
stimulation of the muscle, itself. The greater the tension
the better the muscle responds to the blow on the tendon.
The anterior horn cells are always, during waking hours,
sending tonus impulses to the muscles which keep them
under more or less tension, and these impulses are increased
by reenforcing and decreased by inhibiting influences. It
will be here assumed that the first explanation is correct.

Apparatus 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 (see Fig. 28). The
position must be perfectly comfortable, so that he could
go to sleep. Adjust the support (A) under the thigh so
that the lower leg will siving freely. The subject must be
in such a position 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 do otherwise. Connect the back of the swing by a
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.
The rubber band must be given a few twists, so that by its
torsion it will keep the writing point against the drum. Ad-
just the hammer (E) so that when it hangs vertically, the

THU KNKE-JF.RK.

131

middle 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 right angles to the ligament. Ordiiiarv clothing
will not interfere with results. Make this adjustment with
great care, then clamp the rod supporting the hammer.

Fig. 28. 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 shaped writing needle ; D, rubber band, twisted so as to keep point of
needle against drum; 'E,, knee-jerk 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 ot 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 cjuiet and annoy or excite
the subject, except when a special effect is desired, the
whole experiment fails.

132 EXPERIMENT XXVr.

a. Record of Normal Knee-Jerk.

Find the position of the hammer that will give a knee-
jerk, the record of which is about 2 cm. high. Make note of
position of arm holding 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 the subject is relax-ed and the room quiet, the knee-
jerks vary in height, in other words, that the irritability of
the reflex mechanism is changing".

It not infrequently happens, at first, with an irritable
subject, that the writing point does not return to the base-
line, because of increased tonus of the extensors of the
thigh. As he becomes accustomed to the experiment and
quiets down, the tonus generally decreases and the knee-
jerk lessens.

h. Motor Reenforcement.

When the jerks become about the same height, zvhile
continuing to strike the knee rythmically, tell the subject
to clench his hand at the instant the command is given.
Note whether speaking to him causes larger knee-jerks, i. e.,
a psychic reenforcement; then give order to clench the
hand, and release the hammer just after the order is given,
i. e., allow for reaction time of subject, and cause hammer
to strike knee about o.i sec. after his hand is clenched. Bow-
ditch and Warren found that if the blow on the knee occurs
at the instant the hand is clenched or within 0.4 sees,
after the clench, the knee-jerk is greater than normal, i. e.
reenforced; if the blow is struck between 0.4 and 1.7 sees,
after the clench, the knee-jerk is lessened, i. e. inhibited.
If the blow comes still later, the clench has no effect. The
explanation of the effect of the clench, is that when the
motor-cells of the arm area of the cerebral cortex are
called into action, the motor cells of the leg area of the
cerebral cortex are excited through association fibers, and
impulses from the cells of the leg area of the cortex spread
to the anterior horn cells of the leg area of the cord, and
increase their irritability for a short time. If, however, the

THE KNEE-JERK. 133

nerve impulse from the leg reaches the anterior horn cells
as late as from o.z]. — 1.7 sees, after the clench, it finds them
in a condition of decreased irritability, an after fatigue
effect, and the knee-jerk is inhibited instead of reenforced.
Record another series of normal knee-jerks, and see if the
time of the blow with respect to the clench alters the result.
Sudden discharge of voluntary impulses to any other mus-
cles, e. g. clenching the jaw, or even winking, will also cause
a reenforcement or inhibition.

c. Reeforcemeiit by Sensory Stimuli.

Pulling hair, tickling face with a camel's hair brush, an
unexpected sound or odor, an excitation of the mucous mem-
brane of the throat, of a type to cause unintentional, as well
as intentional swallowing, in short, any sensory impulse of
a type to cause reflex contraction of voluntary muscles, will
cause a reenforcement. In such cases the secondary im-
pulse acts to alter the irritability of the anterior horn cells
(see Fig. 2y) , and so effect the way they will react to the
sensory impulses caused by the blow.

To show this, record ten or more normal knee-jerks by
a series of rythmical strokes, and when the jerks are of
about equal height, test several sensory effects, marking on
drum the times that each of the stimuli is given.

d. Psychic Reenforcement.

With subject as quiet as possible, eyes closed, room per-
fectly still, record a series of 10 or more normal jerks, and
then, while continuing to strike the blows rhythmically,
test the effect (i) of speaking to subject; (2) of ask-
ing him to multiply two^ numbers given him; (3) of
asking him to think of some stirring poem, etc. The
clerk should note all these occurrences with care, and also
the effect of sounds produced in neighboring rooms or
out of doors, the entrance of anv 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.

134 EXPERIMENT XXVI.

THE KNEK-JERK.

135

136 EXPERIMEJNT XXVI.

CONDITIONS DETERMINING BI.OOD PRESSURli.

137

EXPERIMENT XXVII.

Conditions Governing Blood Pressure and Velocity of
Flow. Use of the Artificial Circulation Apparatus.

In this apparatus the auricle is not contractile, and the
ventricle is filled in part by gravity and in part by suction
from the bulb, which has a much greater suction power than
a true ventricle. The pulmonary circulation does not appear.

Fig. 29. Floor plan of artificial circulation apparatus. A, bottle representing
left auricle, with two tubes, representing veins, entering top, and tube com-
municating with valve at bottom ; M, mitral valve, consisting of an aluminum
tube, closed at the end, and having a hole in the side, which is covered by a
tube of rubber dam, which has at one side an opening for escape of fluid,
(when the valve is competent the rubber tube is adjusted so that it covers the
hole in the aluminum tube, and when it is made incompetent the rubber tube is
turned round so that it only partly covers the hole in the aluminum tube). V,
hinged board actuated by cam, not shown in diagram, and compressing the
rubber bulb which represents the left ventricle ; S, aortic semilunar valve ;
Art, large artery connecting by Y tube with two small arteries; i, screw
clamp, representing muscles in walls of renal artery ; 2, clamp, representing
muscles in walls of arteries of skin ; C, tube containing glass wool, represent-
ing resistance in renal capillaries ; RV, renal vein ; SV, skin veins ; 3, clamp
controlling mercury manometer recording pressure in renal artery ; 4, clamp,
controlling mercury manometer recording pressure in renal vein; 5, clamp
controlling tube leading to membrane-manometer, recording pressure in
ventricle ; 6, clamp by which tube leading to mitral or aortic valve can be
partly closed off to produce the resistance of stenosis ; R, support for vertical
rod, to which is to be clamped the receiving tambour, which is to be applied
to the large artery, so that its pulsations may be recorded ; T, stiff walled
tube which is to connect valve chamber S, with Y tube, when the effect of a
stiff walled artery is to be studied.

Become thoroughly familiar with the apparatus before
proceeding with the experiment. Adjust the machine as
follows :

See that the clamps 3, 4 and 5, controlling the connections
with the manometers, are closed, and the clamps i and 2,

138 EXPlvRlMENT XXVII.

controlling the small arteries, are open ; then fill the tubes
with water by pumping rhythmically. If there is not suffi-
cient water in the reservoir, have the assistant replenish it
with distilled water. When fi,lling the tubes, hold the right
hand end of the apparatus up at an angle of 45°, until the
air is out of the tubes nearest the bulb, and then tip up the
other end, and expel the air from the rest of the tubes.

Compress the bulb only by means of the board placed
above it. The rod supporting the cam can be moved up
or down. When a small amount of compression is desired,
let the end of the rod rest on the little block of wood be-
neath ; when more compression is needed, swing the block
to one side and lower the rod.

The folloiving cautions must he observed.

The air should be driven out of the apparatus.

The arterial manometer should be watched, to- see that
the mercury is not driven down round the bottom of the U.

The clamps controlling at least one of the arteries should
be kept partly open ; see that during the pumping water
flows into the reservoir.

Be careful not to bend the rods carrying the pointers of
the mercury manometer.

Mercury should not be allowed to collect above the mano-
meter floats.

Dry the apparatus and table before leaving, and raise the
rod so that the board shall not rest on the bulb.

Whenever the stopper is to be taken out of a valve
chamber, clamp the tube between the bottle and the mitral
valve.

ADJUSTMENT 01' APPARATUS.

Connect the arterial and venous system of the apparatus
with the larger and smaller manometers, respectively, and
open the clamps wide. Mount a time signal to write at
the bottom of the curve, about half a centimeter below the
venous manometer. Adjust the pointers on the floats so
that the venous manometer will write about a centimeter
below the arterial ; the three writing points should be in the

CONDITIONS DEJTe:EMINING BLOOD PRESSURE. 1 39

same vertical line. Be very careful not to bend the delicate
rods carrying the pointers.

Adjust the apparatus to what may be called "normal"
conditions.

a. By sliding the piece of wood under the rod on which
the cam operates, thus limiting the compression of the
bulb, and the amount of fluid pumped.

b. By screwing down clamp 2 on the tube not connected
with the capillaries.

c. By gradually tightening the other arterial clamp i,
until • the flow into the bottle is constant and the venous
manometer barely oscillates, and the arterial manometer
records a diastolic pressure of about 25 mm. (i. e., the pointer
keeps about 12^ mm. above the base line at the close of
diastole) when the rate of pumping is once in two seconds.

Pump rhythmically at the rate of once in two seconds,
and obser\'e : —

1. The ventricle is filled mainly by the suction created
during diastole, and partly by the force of gravity. (In the
body suction plays only a small part, the ventricle being
filled by the returning blood and by the contraction of the
auricle.)

2. The force of the ventricular contraction is converted
partly into energy of flow, i. e., kinetic energy, as seen by
the entrance of the fluid into the bottle; and partly into en-
ergy of pressure, i. e., potential energy, as seen by the
stretching of the wall of the large artery, and the rise of the
mercury in the manometer.

3. The pressure falls during diastole, because the po-
tential, or pressure, energy is converted into energy of
flow, as shown by the venous flow, the narrowing of the
large artery, and the fall of the mercur}^ in the arterial man-
ometer.

4. The pressure in the veins is low, because of the
small resistance ahead, and the fact that a large part of the
energy is expended in overcoming the resistance in the
small arteries.

140 EXPERIMENT XXVII.

5. The pressure in the veins is quite constant, because
it is kept up during systole by the contraction of the ven-
tricle, and during diastole by the elastic recoil of the arterial
walls acting against the resistance in the small arteries and
capillaries. Notice that if the resistance is lessened by
opening clamp i on the artery connected with the capillaries
(causing vaso-dilation), the flow becomes rhythmic, and that
as this clamp is screwed down (vaso-constriction produced),
the venous flow becomes constant again, and the venous
manometer ceases to oscillate. Adjust the arterial clamp so
that the venous manometer bearly oscillates, and make the
following experiments:

EXPERIMENTS. PART I.

a. Effect of Inertia of Mercury.

Adjust the drum to the pointers, and revolve it to draw
base lines. Pump for twenty seconds at a regular rate of
once in two seconds, watching the venous flow and the
arterial manometer, and when the rhythm has been acquired,
and the mercury has reached the new level, continuing at the
same rate, start the drum and take a record. The venous
pressure remains almost constant and low ; the arterial
pressure rises in systole, and during diastole gives several
oscillations, due to the inertia of the mercury.

Now gradually screw down the clamp 3 on the tube
communicating with the arterial manometer until these sec-
ondary oscillations disappear. Leave the machine adjusted
in this wav in the following experiments. This method is.
used to minimize the changes due to inertia, and gives a
record approaching more nearly the mean pressure.

h. Effect of Rate.

Pump at the rate of once in two seconds and when the
arterial pressure has reached the new level, start the drum
and record five or six pressure waves and stop drum. Re-
peat at the rate of once a second, and again, at a rate of once
in two seconds. Next decrease rate to once in three seconds,
and record five waves.

CONDITIONS DF,Ti;RMINING BLOOD PRESSURE. I4I

c. Effect of Increased Output. .

Pump at a rate of once in two seconds, and when the
pressure has reached the new level, start the drum and
record five waves. Now increase the output by lowering the
rod on which the cam works, and repeat, recording five
waves.

d. Effect of Resistance.

Pump with ^'normal output," at the rate of once in two
seconds ; when the pressure level is reached, record five
waves and stop the drum ; keep on pumping, but loosen the
screw of clamp i, representing the peripheral arterioles, and
when the new pressure level is reached, start the drum and
record five waves; stop the drum, but keep on pumping;
now screw down the clamp until the venous flow is almost
obliterated, and when the new pressure level is reached,
start the drum and record five waves.

e.- Effect of Resistance in Tivo Systems of Arteries on
Distribution.

The main artery divides into two branches; the one
having the capillaries and controlled by clamp i, can be con-
sidered the renal artery, and the other controlled by clamp
2, the arteries of the skin. Dilation of the skin vessels will
lower the general arterial pressure, and the pressure in the
renal artery Avill fall, and the flow through the kidney will
lessen. Increasing the vaso-constriction in the skin will
produce the opposite efi^ect.

Test this out on the model, by pumping at the rate of
once in two seconds, when clamp i is adjusted to "normal
conditions, and clamp 2 is closed ; then while continuing to
pump, and while watching the flow from the renal vein, grad-
ually open clamp 2, (produce vaso-dilation in the skin ves-
sels) ; then screw dowm clamp 2, (cause vaso-contriction in
the skin). Repeat the experiment with the drum running,
and record the changes in pressure in the renal arten'.

142 i:xpt]:rime;nt xxvii.

/. Some Clinical Applications.

By varying the rate of pumping-, the volume pumped,
and the peripheral resistance, one can imitate a number of
interesting phenomena.

1. Hffect of Vagus Inhibition. By vagus inhibition the
heart is stopped, then occasional beats are seen, then, when
the inhibition ceases, the heart beats gradually faster until
a rate somewhat higher than normal is reached (to compen-
sate for the low pressure), and then returns to its normal
rate. To test these effects, adjust machine to normal con-
ditions, pump at rate of once in two seconds, let drum run,
and after about ten seconds produce the inhibition effects
by altering the rate of pumping

2. Action of Depressor Nerve. This nerve starts at the
root of the aorta, where it is excited by a pressure higher
than normal. It acts to inhibit the vaso- constrictor center
in the medulla and possibly to excite the vaso-dilator center,
and so causes vaso-dilation. The action can be readily imi-
tated by pumping at a regular rate, and after the normal
pressure is obtained, lessening the peripheral resistance in
the small . arteries gradually, (clamp 2 can be used to ad-
vantage), and then restoring the pressure by gradually
tightening the clamp.

3. Tranbe-Hering Wairs. These waves are caused by
rythmic action of the vaso-constrictor center.

4. Nitrite of Amy I. This drug acts on the muscles of
the walls of the arteries, causing them to dilate. As the
dilation occurs the heart beat quickens to compensate for the
fall of blood pressure. During the pumping produce a
gradual fall of pressure, and then attempt to restore the
pressure by cjuickening the rate of the heart.

5. Hardening of Wall of Artery (arterial sclerosis).
Obtain a "normal" record of five or six pressure waves.
Stop the drum, substitute for the elastic, an inelastic, stiff
walled rubber tube (T) supplied in the basin. Leaving the
other adjustments as before, pumping at the same rate,
again record five or six waves. Observe the character of the

CONDITIONS DE;Tli:RMINING BLOOD PRESSURE.

143

flow into the bottle. Caution. There will be a big fling of
the mercun^ and the manometer must be watched to see that
the mercury is not thrown out.

Notes. State in the notes the eft'ect of increased heart
rate, increased output, increased peripheral resistance, and a
hardening of the arterial wall, on the mean, systolic, diastolic
and pulse pressures recorded by the arterial manometer. State
effect of these factors on the venous pressure, on the size
of the venous pressure oscillations, and the venous flow.
State how the blood flow through an organ is influenced by
vaso-motor changes in a distant organ. The results may
be given to advantage in tabular form, an increase being
noted by -f- and a decrease by — .

Heart has Increased

Vaso-constriction

Artery

Rate

Output

I^ocal

Distant

Harden-
ed

Arterial pressure

Mean

Systolic

Diastolic

Pulse
Venous pressure
Venous oscillations
Venous flow

144 e:xpi<:rime;nt xxvii.

CONDITIONS DETERMINING BLOOD PRESSURE. 145

EXPERIMENT XXVI I—SECOND DAY.

PART II.

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 rub-
ber membrane are connected together by tubing. A plate of
metal resting on the membrane of one of the drums, (the
recording tambour), is connected with a light lever, and
wdien air enters or is driven out of the other drum (the
receiving tambour), by movements imparted to the mem-
brane 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 con-
trolled hv a pinch-cock. The level of the lever can be ad-
justed by placing the support of its axis at a suitable angle.

Caution. Do not ap-
ply the pinch-cock, ex-
cepting when the tam-
bours are to be used.
See that the lever of

iMg. 30. Recording tambour. A, tambour; ,. ^

B, alumimim plate, with ball-and-socket joint the reCOrdUlg tamOOUr

for pin acting on lever; C, lever with celluloid • Ur^rivr^-nt^] incf ht^-

writing point ; D, support of lever. ^S IJOriZOniai JUSt DC

fore a record is to be
taken, and never let the membrane of the recording tambour
be greatly stretched.

Adjustment of Apparatus to Record the Pidse and
Ivtrai'entricular Pressure.

Adjust a receiving tambour to the wall of the arter}^
and connect it with the large recording tambour. Connect
the tube from the ventricle with the small recording tam-
bour. Arrange the writing points, to write in the same
vertical line with the float of the arterial manometer. Adjust

146 EXPIJRIMENT XXVII.

the rod limiting the pressure of the cam on the bulb so as
to give a small output from the ventricle, then pump in the
manner directed, at the rate of once in two seconds.
Only a very small pulse is given with clamp i, represent-
ing small arteries, wide open. Gradually increase the peri-
pheral resistance, and observe the resulting distention of
large arterv and pulsation of tambour. Several beats may
be required to fill the artery before the tambour will record,
and then the record should be 8-10 mm. high. Record on
the drum, simultaneously, the pulse, the intra-ventricular
pressure, the arterial and venous pressures, and the time.
The pulse given by the apparatus does not give a true picture
of the human pulse ; for example the dicrotic and the predi-
crotic and postdicrotic waves are not shown. One can use the
machine, however, to study the effect of a number of con-
ditions on the height of the pulse oscillations, and on the
rate of fall of the pulse wave.

a. Effect of Rate.

With the machine adjusted for normal conditions, pump
for thirty seconds, at the rate of once in two seconds ; start
the drum, adjusted to run four mm. per second, and record
five or six waves. Stop drum. T'ump at the rate of once
a second ; once in two seconds ; once in three seconds, con-
secutively, getting records in each case, stopping the drum
between records.

b. Effect of Vohime Output.

Record five normal waves. Stop drum. Increase output
by lowering rod and keeping the same rate, record five more
waves.

c. Effect of Peripheral Resistance.

Open the clamp (i) representing the peripheral resist-
ance in the arterioles. Pump at the rate of once in two
seconds, and record five waves. (Low resistance pulse).
Stop drum, continue pumping, and gradually increase the

CONDITIONS DETERMINING BLOOD PRESSURE. 147

peripheral resistance by tightening the clamp until a stream
barely flows into the bottle. Record five waves. Caution —
Watch arterial manometer.

Azotes. — B.vplain effect of rate and volume output on
shape and she of pulse. Why docs increasing peripheral
resistance^ for example, cause pulse waves to first grow
larger and then svialler? Explain the effect on the rate of
fall of the pulse wave. Explain difference in ventricular and
aortic pressure curves.

PART III.

Effect of Lesions of Heart Valves.

Failure of a valve to close its orifice perfectly is called
insuificiency. Abnormal narrowing of its aperture is called
stenosis. These defects in heart-valves are usually accom-
panied by dilation of the cavities, which discharge through
the valves, and hypertrophy of the heart muscle, which is
known as compensation. These three conditions can be
imitated in a way in this machine as follows : Insuificiency,
by rendering a valve incompetent, by adjusting the rubber
tube so that it only partially covers the opening in the alum-
inum tube ; stenosis, by applying clamp 6 to the tube leading
to a valve chamber ; and compensation, b}' increasing the
compression of the bulb, thus permitting a greater outflow
at a stroke.

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
are here separated from complications usually present. In
the model compensatory changes can occur only in the left
ventricle, and the compensator}- effects produced by changes
in the auricle and in the right side of the heart cannot be
studied.

With the apparatus adjusted for normal conditions, be-
ing sure that there is a slight venous pulse, and pumping
at the rate of once in two seconds, record, first, five or six

148

EXPERIMENT XXVII.

normal beats ; stop the drum, create the lesion desired,
and after pumping a number of times, start the drum^ and
record five or six lesion curves. Again stop the drum,
cause the compensation, and after pumping a short time,
again record five or six waves. This comjpares in a row,
normal curves, effect of cardiac lesions, and effect of com-
pensation.

Repeat for each valvular lesion in the following order:

a. Mitral Stenosis.

b. Aortic Stenosis.

c. Mitral Insufficiency.

d. Aortic Insufficiency.

Notes. — B.vplain the results in each case, and state in
which cases the compensation tnade the curve more nearly
normal, and zvhy. Also state changes in form of pidse.

Use the follozmng form in reporting the effects of the
valvular lesions studied.

LESION

PREvSSURE
Increased or Decreased

COMPENSATION
Effective or Ineffective

Mitral
Stenosis

vSystolic.

Diastolic

Pulse

Intraventricular

Venous

CONDITIONS DEITIJRMINING BLOOD PRESSURE). 1 49

I50 EXPIvRIMENT XXVIl.

CIRCUT,ATI0N AND RESPIRATION 01^ MAM MAI,.

151

EXPERIMENT XXVIII.

Circulation and Respiration of the Mammal,

Experiments on these subjects will fill two afternoons,
the apparatus and general methods being the same for both
days. The students will work in groups of four, and the
part of the work to be done by each student is shown in
the following schedule. The number of the student as
given in the schedule will be assigned by lot.

SCHEDULE OF WORK.

Experiment 28

Student i

Student 2

Student 3

Student 4

Right carotid
and vagus

Operate

Assist

Etherize

Apparatus

Left carotid
and vagus

Apparatus

Operate

Assist

Etherize

Sciatic

Etherize

Apparatus

Operate

Assist

Tracheotomy
and open chest

Assist

Etherize

Apparatus

Operate

Second Day
Experiment 20

Right carotid
and depressor

Assist

Etherize

Apparatus

Operate

Left carotid
and depressor

Etherize

Apparatus

Operate

Assist

Tracheotomy
and open chest

Apparatus

Operate

Assist

Etherije

Phrenic and
peristalis

Operate

Assist

Make nerve
leg prepart'n

Apparatus

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

152

experime;nt XXVIII.

Apparatus. — The arrangement of the apparatus is to
be seen in Fig. 31. The following list of apparatus and
instruments will be required, and everything must be at
hand before the work is begun. The cannulae are to be kept
in parafine oil, and will be issued by the Instructor.

APPARATUS TO Bt FURNISHED BY LABORATORY.

Animal-board with head-holder.
Manometer outlit.
Artificial respiration outfit.
Basin for sodium chloride.
Battery jar.
Bottle of ether.
Bulb and cannulae for artery.
Cabinet-makers' clamp.
Two Cannulae for trachea.
Burette clamp.
Three clamps for stand.
Screw clamp for trachea.
Three screw clamps.
Etherizing cone.
Four cords for animal board.
Two cords with hooks.
Two cloth covers.
Director.

Dish for sodium sulphate.
Dropper.

Electrodes.

Bulldog forceps.

Kymograph for long paper

Lig'atures, fine.

Ligatures, coarse.

Water manometer.

Two pinch cocks.

Plate.

Pneumograph.

Rod, nickled.

Rubber tube with glass T.

Scalpel.

Shears.

Sponge.

Small stand.

vSupport for kymograph.

Recording tambour.

Two towels.

Silk thread and weight.

Time signal.

APPARATUS TO BE F'Ui^NISIIED BY THE FOUR STUDENTS AS-
SIGNED TO THE WORK.

One dry cell.
Induction coil.
Drum square.

Fine and strong forceps.

Mercury key.

Wires.

CIRCULATION AND RF.SPURATION OF MAMMAL.

153

DIRECTIONS TO STUDENTS CARING EOR APPARATUS.

First close cock i and all clamps, then raise pressure to
no mm. (55 on scale), in bottle (I) containing anticoagu-
lation fluid, by using pump. Pump very carefully, or the
mercury will be forced out of the manometer. Next raise
bulb K until it and its tube are vertical ; open clamp 4, then
gradually open clamp 3, and let fluid rise in tube and fill
bulb ; finally close clamps 3 and 4. Put bulb in dish so that
any drip will be caught. Open cock i, and then gradually

Fig. 31. 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-
circuit key; E, mercury float; F, electrodes; H, bicycle pump; I, anticoagula-
tion tluid pressure bottle ; J, manometer communicating with pressure bottle ;
K, bulb and cannula; i, cock; 2, 3, 4, clamps.

open clamp 3 and fill the tubes connected with the mano-
meter. When the fluid has risen as far as clamp 2, close
clamp 3 and then clamp 2 and cock i. It may be necessary
to introduce a vvdre into the right side of the manometer
after taking off clamp 2, in order to remove the air from that
portion of the manometer. If in the process of filling, air
bubbles are seen in the tubes, they may be removed by rais-
ing the manometer end of the system and tapping on the
tubes. Clamp 3 should be closed or only slightly open

154 EXPERIMENT XXVIII.

while this is being- done. 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. Now place bulb K slightly above level of mercury
in manometer ; open cock i and clamp 4, and lower bulb
until the mercury of the recording manometer has the same
level in the two arms ; close clock i and clamp 4. 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.

Connect the clock circuit with the binding posts at the
back of the board connected with the time signal. Place the
induction apparatus behind the manometer outfit, and put a
dr}' cell and a key in the primar)^ circuit, connecting them
so as to give a tetanizing current. Connect secondary coil
with the binding posts at the back of the board connected
with the short-circuit key (D) on top of manometer board.
Fasten a pair of electrodes (P") to the binding posts on the
front of the board. Start vibrator, open short-circuit key,
and test current with the tongue. A current of medium
strength will suffice. Using drum square, see that writing
points of recording tambour (A), manometer (B), and key
(D) write in the same vertical line.

By means of pump, raise the pressure in the bottle con- ■
taining anticoagulation fluid until the mercury in the mano-
meter connected with the bottle stands at 100 mm., pumping
with care. Open cock i, and then gradually open clamp 3,
until the mercury in the recording manometer rises to 50
mm. Close i and 3. 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 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. See that three loops of paper for
kymograph have been blackened, and place one on the
drums. Mark the position of the writing points on the
paper.

CIRCULATION AND RESPIRATION OF MAMMAL- 155

During the taking of the records you must start and
stop the drum ; must mark the position of the writing points
on the dnnii before each test ; must give the stimulations by
depressing the short circuit key ; see that the drum runs for
at least 15 seconds before and 15 seconds after each test;
put a letter a, b, c, etc., indicating the experiment, just over
the record of the short circuit key, for each test ; and must
label each loop of paper with your name, before giving it to
the assistant to fix. At the close of the experiment, you must
clean all stimulating and recording apparatus, and account
for each piece to the Instructor.

DIRECTIONS TO ASSISTANT.

It is the business of the assistant to see that the instru-
ments and ligatures are in order, and are at the hand of the
operator throughout the operation and the experiment. Can-
nulae will be supplied by the Instructor when required.
While the animal is being etherized, fill the animal board
with water at 45° C; heat some salt solution in a basin pro-
vided for the purpose, put a sponge in it, and place it on
the operating table. During the operation, be ready to
sponge the wound, to pass needed instruments to the oper-
ator, and to tie the ligatures when required. Do not be
officious. Remember that you are the assistant of the oper-
ator. At the close of the experiment you must return all in-
struments, cannulae, etc., in good order to the Instructor,
and see that the animal board, head holder, and artificial
respiration apparatus are clean.

Anesthesia.

Anesthesia may be divided into three stages : I, Incom-
plete ; II, Complete : and III, Danger period. These stages
show the following peculiarities, which must be kept in
mind when administering ether. (For anesthesia in man,
see Cushney's Pharmacology^)

Stage I. a. Straggling because of dislike of the drug,
and later because of excitation of Nervous Systems ; respira-
tion irregular from irritation of mucous membrane, often

156

EXPERIMF.NT XXVIII.

with pauses and gasps ; salivation for the same reason ; pupil
dilated, b. Consciousness beginning to he lost, and toward
end, lessening of reflexes.

Stage II. Quiet; respiration regular and deep, ("snor-
ing respiration") ; pupil contracted; reflexes lost; complete
unconsciousness.

Stage III. The. danger period. Respiration slow and
shallow, often long pauses; pulse slow and feeble; pupil
dilating quickly ; absence of all reflexes.

Rabbits difl^er from men, dogs, and cats, in that convul-
sive respirations immediately precede death in the third
stage.

These effects may be tabulated as follows :

STAGES ANESTHESIA.

Incompleti;

Complete;

Danger Point

Respiration
Depth

Medium

Deep

Shallow

Rate

Rapid

Slow

Slow

Regularit}^

Irregular
often long
pauses

Regular

Gasps or long
pauses, or
convulsive

Reflexes

Present

Absent

Absent

Pupil

Dilated

Contracted

Dilating

The Behavior of the Pupil may be explained as follows :
The size of pupil is controlled by twO' muscles, the sphincter
pupillae and the dilator muscle. Each of these antagonists
is during waking hours in more or less tonus. Contrac-
tion of the pupil might be caused by excitation of the
sphincter or inhibition of the dilator muscle ; dilation might

CIRCULATION AND RESPIRATION OE MAMMAL. 157

be caused by excitation of the dilator muscle or inhibition of
the sphincter ; or both of these processes might occur simul-
taneously ("reciprocal innervation").

During- waking periods, the tone of the sphincter tends
to be inhibited by sensory stimuli, and the pupil tends to
dilate.

Light falling- on the retina causes reflex excitation of the
sphincter, and perhaps inhibition of the dilator, and the
pupil tends to contract.

Emotional excitement tends to cause marked dilation of
the pupil; by excitation of the dilator, as well as inhibition of
the sphincter, and this is to be seen zvhen the ether is first
applied.

In sleep the eyes are rolled upward and outward, and
the pupils constrict because of lessening tone of the dilator
and greater tone of the sphincter, and this is to be seen in
complete anesthesia.

In the danger stage, the centers controlling- the sphincter
cease to act and the pupil dilates.

Directions to Anesthetizer.

vSee 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 ,anesthetizer puts some ether on the gauze of the
cone, and places the cone over the animal's mouth and nose.
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 must think of nothing else.
If the animal dies through his fault, he must pay for an-

158 EXPURIMF.NT XXVIII.

Other, ( 50 cer.ts). Watch especially the respiration, and when
in doubt, pinch toot, 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
present, the animal is "coining out" and needs more ether.
If the respiration stops, or becomes convulsive, immediately
test the reflexes, and if the reflexes are absent stop the
ether; start artificial respiration, by rhythmically compress-
ing the chest laterally ; 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 collection of
mucus are heard, swab out the throat with absorbent cotton
on large forceps.

DIRECTIONS TO OPERATOR.

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

. A rolled towel placed beneath the neck may help oper-
ator by putting parts under tension. 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

CIRCULATION AND RESPIRATION OF MAMMAI..

159

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 better to tear away the fascia longitudinally
Avith the blunt end of a director or similar instrument,

..--' M. stylohyoideus major.
•• N. hypoglossal.
" Superior laryngeal.
Descendens noni.
2 roots of depressor nerve.

Vagus.

Depressor.

Sympathetic.

Carotid artery.

Trachea.

M. sterno-mastoid.

Fig. 32. Dissection of nerves of left side of neck of rabbit. The trachea has
been pulled to the right and the nerves to the left.

rather than use a knife. The descendens noni lies super-
ficially ; 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.

l6o e:XPKRIMKNT XXVIII.

Prepare the upper 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
c// two ligatures under it, and tie

^ // /N3 one of them tightly at the

V:^ f I'y^^x upper end of the exposed part

— ^j — i>"^^\; — ^ of the artery ; place the other
"^ /, ^ so that it can be used at short

Fig. 33. Method of inserting can- HOticC tO tie the Caunula in

tlT^S^^-ot^^^ place. Apply a pair of bull-

where the cannula IS to be inserted ; dog forCCpS tO loWCr part of

B, cannula ; C, forceps ; D, loop of , , i , /v i i i atvi

ligature placed around artery, to the artcn,^ tO Shut Off blOOd. ihere

proximal side of point where can- / mptKnrIc nf inQPr+ino-

nula is to be inserted; E, bull-dog ^^^ ^^^ *-l mCinoaS 01 inserting

^°'''=^P^- a cannula, viz: i. Grasp with

fine pointed forceps as sina.ll a part of the arterial Avail as
3'ou 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,
insert the cannula supplied by the Instructor, and let the as-
sistant tie it in firmly with the ligature which has been placed
there for the purpose. 2. Place the index finger of the
left hand beneath the artery ; with sharp, fine pointed scis-
sors make a cut in the wall of the artery ; and without with-
drawing 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. Apply the
pneumograph and connect with tambour.

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-

CIRCULATION AND RESPIRATION 01' MAMMAL. l6l

tween the cannula and the artery. The blood should be
seen to enter the cannula and diffuse into the fluid, in the
bulb. Tf all is right, gradually open stop-cock i. The
manometer float should rise, and the height of arterial pres-
sure be recorded. Start the drum and take four records,
stopping the drum and marking the position of the writing
points between them. 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 effect of cor-
responding pressure changes in the artery, on the mercury in
the manometer.

b. B.rcitation of the Peripheral End of the Right Vagus.

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.
Remember to mark position of writing points before each
test. Place peripheral end of vagus on the electrodes, taking
care that they touch nothing else. Closekey of primary cir-
cuit ; see that vibrator works well. Record a curve of normal
pressure for 15 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 necessar}'. Excite for only 10 seconds, then close short
circuit and watch recovery 15 seconds. Repeat the experi-
ment 4 times, to provide a record for each student, and give
an interval of half a minute between the succeeding tests.

c. Excitation of Central End of the Vagus.

Now while taking record of blood pressure and respir-
ation, excite central end of vagus with weak current. Affer-
ent fibers are excited, (sensory of the air passages and
"respiratory pressor and depressor" of the lung), resulting
in the following :—

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

2. — Excitation of vaso-motor center, tending to produce
a rise, but occassionally a fall of blood pressure.

J 62 e;xpkrimi-nt xxvin.

3. — Excitation of vagus center, which frequently slows
the heart through a crossed reflex, and causes a fall of pres-
sure in spite of vaso-constriction which may occur.

4. — If current is too strong, and the anesthesia 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 operator tie off the right carotid below can-
nula, and remove canula from artery. L,et assistant hold a
dish under the cannula and then disconnect bulb from
manometer tube ; wash bulb and cannula out thoroughly ;
connect bulb again with manometer tube ; return cannula to
the instructor. ITandle bulb and cannula with care, as they
are fragile and hard to replace. Sponge up all fluid spilled
and put apparatus in order for next experiment. Discon-
nect and remove pneumograph.

d. 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 blood pressure, when the left vagus is
excited.

e. 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 ivell under the ether before the nerve is handled, and
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-
ilex vaso-constriction, or, as not infrequently occurs, a fall
due to reflex vaso-dilation. If current is too strong or ani-
mal not well under, convulsive movements will be produced
which will mask the effect desired.

CIRCULA'i'ION AND RESPmATlON OF MAMMAL. 1 63

/. Blood Pressure during Asphyxia.

Expose the trachea and place loiv dozLu 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.- — Dyspnea. 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. — AVeakening and slowing of heart beats : respirations
feebler and fewer ; finally both heart beats and respirations
stop.

g. Elasticity of Lung Tissue.

Make incision .in trachea; insert cannula: and connect
with a water manometer, noting the level of the fluid. Open
the chest and note the new level to which the water in the
tube rises when air enters the chest and the lungs collapse.
The air which leaves the lung when the chest is opened is
the "residual" air. (see diagram, ICxperiment XLI). To
open chest, first make an incision with the knife over the
entire length of the sternum : grasp ensiform cartilage with
strong forceps ; push point of strong shears through chest
wall at end of ensiform cartilage and cut sternum length-
wise, in the median line, to within 2 cm. 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. Remove the lungs ; put them
in water, and notice that they float. This is because of the-
''mimimal air" which is imprisoned by the collapsed bronchi.
The fact that the lungs float, provided that there are no
gases due to decomposition, is considered a proof that the
animal has breathed.

164 expi3rime;nt XXVIII.

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 15 seconds before, and 15 seconds
after the period of stimulation. Draw three pairs of long
vertical lines from the time curve through the pressure and
respiration curves, so as to enclose periods of 6 seconds be-
fore, during, and just after cessation of stimulation.

To find the blood pressure, measure from the base line,
.given by the time signal, to the blood pressure curve, using
the middle of the pulse beats for the mean pressure, and
multiply by two. For heart rate, count the pulse beats in
the 6 seconds between the 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 obser-
vations.

Give brief statements of the results obtained under each
of the subheadings of the experiment, stating the cause of
the changes in arterial pressure, pulse, and respiration pro-
duced bv the excitations.

CIRCULATION AND RKSPIRATION OF MAMMAL. 165

l6.6 EXPERIMENT xxviri.

CIRCULA1I0X AND RESPIRATION OP MAMMAL. 167

EXPERIMENT XXIX
Circulation and Respiration of the Mammal, Continued.

a. Excitation of Right Depressor Nerve.

The depressor is an afferent nerve from the root of the
aorta, and hence excitation of the peripheral end has no
effect. Excitation of central end has little effect on the
cardiac centers, but causes dilation of peripheral vessels by
inhibition of the vaso-constrictor center.

Expose the carotid as in Experiment XXVIII. To find
the depressor, remember that vagus lies behind the artery
and the depressor and the sympathetic to the inner side. High
up the vagtis gives off a transverse branch, the superior
laryngeal, (see diagram, Experiment XXVIII) 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 2 cm. or more, tie a thread about it and cut peripherally
to thread. Handle nerve with utmost care and see that it
does not drv^

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. 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. Is the rate of heart changed?

b. Excitation of Left Depressor Nerve.

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 2 cm. of ether in the bottom, and replace the cork.
Make an incision in the trachea, insert the cannula, and tie

;i68 EXPICRIMENT XXIX.

it firmdy in place with a strong- ligature. Now give the
ether by holding the cone above the tracheal cannula.
While this is being done, the apparatus man should pre-
pare 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.

To open the chest, first make an incision with knife over
entire length of sternum, grasp ensiform cartilage with
strong forceps ; push point of shears through chest wall at
end of cartilage and cut sternum lengthwise, in the median
line to within . 2 cm. of its upper end. Keep point of
shears close to sternum to avoid cutting lungs or other or-
gans. Special care is necessary at the upper part, or blood
vessels will be cut.

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. Does your curve cor-
roborate this statement? If not, why?

d. The Current of Action of the Heart.

Draw chest walls apart with the hooks provided. Open
the pericardium widely, faking 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.

e. Observation of Bxposed Heart during Vagus B.vcitar-

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.

CIRCUr.ATION AND RESPIRATION OF MAMMAI,. 1 69

/. 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 widely 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
w^hich 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.

i. 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.

lyo

i!;xpr;RiMEN'r xxix.

CIRCUIvATlON AND RESPIRATION OF MAMMAL. 171

1^2 r;xrr;RikE:N'r xxix.

CAROTID rULSlJ IN MAN.

173

EXPERIMENT XXX.

The Carotid Pulse in Man.

The Form of the Pulse Wave, and Bifect of Arterial Pres-
sure.

The pulse is a wave of pressure which is transmitted
along- the arterial system when the heart drives blood into
the aorta. Each systole raises the pressure suddenly, giving
what is called the systolic pressure, and during the follow-
ing diastole the pressure falls, until, just before the next
systole, the diastolic pressure is reached. The amount that
the pressure changes, that is the difference between the
systolic and diastolic pressures is known as the pulse pres-
sure, while the pressure midway between the systolic and
diastolic is for ordinary purposes spoken of as the mean
pressure, although on account of the distribution of the pres-
sure values from systole to systole, it is not the true mean.

A B

Fig. 34. Sphygmograms of two pulse beats,
one taken when the pressure was quite high
and the other when it was quite low. A,
crest of primary wave ; B, dicrotic notch ; C,
dicrotic wave.

Under ordinary conditions the caliber of an artery can-
not be seen to change when the pulse wave travels through
it ; nevertheless, if the vessel be slightly compressed by the
finger, the pressure change can be felt, and if the finger
has been trained, not only the extent but character of the
pulse wave, and the amount of the systolic and the diastolic
pressure can be more or less accurately estimated. If a

174 . EXPERIMENT XXX.

suitable instrument, a sphymograph, be applied to the skin
over the artery a record of the pulse pressure changes may
be obtained. The instrument will not measure the pressure,
and the record fails to give an absolutely correct picture of
the course of the pressure oscillations, because they are
modified by the intervening tissues and by the incapacity
of an instrument to follow with exactness all the rapidly
alternating phases of the pressure changes. Nevertheless,
the most marked changes in the pressure are well pictured
both with respect to time and extent, and the records give
information which in certain conditions are not only of
scientific interest but of decided clinical value.

The form of the pulse curves varies greatly with the in-
strument used and the artery from which the pulse is re-
corded. A typical pulse curve is usually described as con-
sisting of a rapid primary up-stroke, the anacrotic limb, and
a prolonged fall, the catacrotic limb, on which a number of
oscillations are to be seen, (see Fig. 34). One of these oscil-
lations, which shows one-third the way along the curve, is
always to be seen. It consists of a more or less deep notch,
the dicrotic notch, and is followed by a definite wave, the
dicrotic wave. The dicrotic notch is of especial importance
because the descending limb of the notch marks the closure
of the aortic valve. The notch therefore divides the curve
into a systolic portion, during which the left ventricle is in
communication with the aorta, and a diastolic portion, dur-
ing which the arteries are shvit off from the heart. The
systolic portion gives indication, therefore, of the way the
ventricle imparts pressure to the blood in the artery and the
resistance which it encounters, and the diastolic, of the con-
ditions in the arteries, themselves, which determine the rate
of fall and oscillations of the pressure. Occasionally a wave
or shoulder is observed on the ascending limb, an anacrotic
wave, which usually implies that there is some unusual re-
sistance offered to the flow of the blood from the ventricle.
Almost always a wave is to be seen on the descending limb
preceeding the dicrotic notch, and called the predicrotic

CAROTID PULSP; IN MAN. 1 75

wave. This in many cases at least is an instrumental error,
due to the fact that the recording- lever has been thrown
too far, and has made a depression on the curve when it
recoiled. Waves may also be seen following- the dicrotic
notch, post dicrotic waves, which are generally supposed to
be reflected waves from various points along the walls of
the arteries. Not infrequently there is a slight wave to be
seen just at the close of the diastolic period ; this wave,
coming at the time that the auricle is completing the filling-
of the ventricle, suggests that the sudden swelling of the
ventricle may have imparted a slight push to the root of
the aorta.

The dicrotic notch is of additional importance, because

the height of the notch above the base-

p-~S^ line gives an indication of the rate of fall

" -'- -^^^ of diastolic pressure. When the pressure

is maintained during diastole, the post-

V c dicrotic portion of the tracing falls in

\\/'"i I nearly a straight line and the dicrotic

L i-A-V-^^S^^J- notch is high ; when the pressure falls off

rapidly during diastole, the post-dicrotic

Fig. 35. Diagram ^- r 11 • u" u • 1

of a high pressure portion lalls m a curvc which IS mark-
foV^ pressurT p°uisl cdly couvcx toward the abscissa, and, es-
iotch; \ dicrouc pecially if the mean pressure is low, the
wave. dicrotic notch is deep.

In Fig. 35 the unbroken lines give the "skeleton" oi the
pulse, that is, show the general course of the wave of pres-
sure, and the broken lines indicate how secondary waves
may be superposed on this. When the pressure is high, the
waves are generally few and small, and when it is low, they
are often many and large.

Apparatus. — 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 lever of the tambour is
horizontal. 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

176 EXPKRIMBINT XXX.

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,
Fig. 36. Tambour and ^"h^n bring Writing point very lightly

neck spring used to study agaiust drum. Start drum at 5 mm.

the human carotid pulse. , , . , , , . ,

A, spring; B, baii-and- per sccoud, close Side branch with

socket joint, on back of • ^• j j j.l_ r it,

open tambour; c, block, spmig clip and rccord 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. Usually
the lever is thrown too high, and as it falls depresses the
rubber membrane and records a notch which might be
mistaken for the dicrotic notch. The second notch is gen-
erally the dicrotic, and is followed by a wave larger than
that which would be given by the recoil of the membrane.
This is the dicrotic wave. 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.

a. 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-
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 per minute.

b. Duration of Systole and Diastole.

Mount a fork in place of the time signal ; see that lever
is horizontal z^'heii the side tube is open; 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

CAROTID PULSE IN MAN. 177

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 Hne, 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 curvx. If one triangle is
placed horizontally beneath the fork curve and held firmly
in place, the other can be slid along it, and the verticals be
drawn rapidly and exactly. Count up the fork waves be-
tween the perpendiculars, and thus determine the duration
of systole and diastole. In counting the vibrations of the
fork, it is best to make a little mark over every fifth vibra-
tion. This can be done rapidly if one learns to see four
vibrations at a glance and marks the fifth. Make this deter-
mination for five consecutive pulse beats and state the aver-
age in your notes.

c. Effect of Exercise.

Go through the form of taking a normal record^ as in^ A-"
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 run
down stairs and back, connect up the tambour as soon as
possible, and record the accelerated pulse. Determine dur-
ation of systole and diastole, and calculate the heart rate.

Which changes more 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.

lyS EXPERIMENT XXX.

CAROTID VVlSn JN MAN.

179

l8o ■ EXPERIMENT XXX.

FORM AND POSTPONEMIiNT OF RADIAL TULSli.

EXPERIMENT XXXI.

The Radial Pulse Studied by the Tambour Method.

Fig. 37. Method of applying tam-
"bour to wrist, to obtain sphygmo-
gram from the radial artery. A,
cross section of wrist; B, back
toard 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.

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-
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
pressure 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.

a. Form of Radial Pulse.

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

1 82 I^XPURTMF,NT XXXI.

points, then record the three curves with fastest speed given
by kymograph. Without disturbing apparatus, remove
clips 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 of five consecutive beats.

r'ORM AND POSTPONKMENT OI- RADTvM, PULSK. 183

EXPERIMUNT XXXI.

INFLUENCES AFFECTING RADIAI, PULSE.

185

EXPERIMENT XXXII.

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
toward the hand. The instrument slips into groove C of

Fig. 38. Scheme of Jacquet's sphygmograph.

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. Cam wheel P, turned
by thumb-nut Q, varies the tension of the spring, by which
button A'' is pressed on the artery. Movements of A^ are

1 86 EXPERIMTJNT XXXII.

transmitted through rod R, to lever S, turning on axis T,
thence to lever U, turning on axis V , and finally to marker
W. Position o f writing point on the paper and the pressure
of button on the artery, are regulated by thumb-screw D.

To obtain the proper pressure on the artery it is neces-
sary, therefore, to use both thumb-nut Q and thumb-
screw D.

CAUl'IONS.

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

(2) A_void 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.

a. Normal Curves and Effect of Position of Body.

Place several strips of paper around a 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 2 cm.

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 per minute as
recorded for six seconds.

b. Effect of Compressing Brachial Artery.

While the tracing is being taken, compress the brachial
artery with hand. , ' 1 1 j

c. Effect of Deglutition.

Start the paper at the slow speed record a few beats, then,,
while record continues, take several swallows of water in
quick succession, marking on the record the exact time whert

INFLUENCES AFFECTING RADIAL PULSE. 187

the swallowing- begins and ends. Determine the rate be-
fore, during, and after swallowing. The change in rate is
explained as due to alteration of vagus influence. The swal-
lowing center is in the medulla oblongata not far from the
vagus inhibitory center, and nervous impulses overflowing
from the former affect the latter.

d. Effect of Inhalation of Amyl Nitrite.

Take the record on two strips of paper pasted together,
and use the slow speed. Record normal pulse for 20 beats,
then begin to inhale amyl nitrite that will be supplied by the
instructor. Associate should mark on record the exact time
of inhalation. Continue record to end of paper. This drug
acts chiefly, when taken in small 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 heart tends to compensate for the fall of pressure by
increasing its rate. The change in the level of the writing,
frequently seen, cannot be taken as evidence of the dimin-
ished arterial pressure, because it may be due to a move-
ment of the wrist. The writing point must be placed high
before the inhalation occurs, or it will run off the lower edge
of the paper. Do not repeat. Mark on curve the place where
the effect was the greatest, remembering that a deep dicrotic
notch is an indication of low blood pressure. State in the
notes what change took place in the heart rate.

e. Valsalva's Experiment.

Record 20 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.

l8» EXPERIMENT XXXTI.

/. MilUcr's Bxperiment.

Record 20 beats, then exhale as completely as possible,
and with mouth and nostrils closed make a strong inspiratory
effort for five 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
by way of the veins.

INFLUENCES AEEECTING RADIAL PULSE.

igo EXPERIMENT XXXII,

CAPIlvIvARY CIRCULATION. 19I

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

Choose a frog having little pigment in the skin of the
foot. Destroy the brain 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.
Inject I cc. of curara into the dorsal lymph space. When
the reflexes have begun to weaken, wrap the frog in moist
cloth, place on special stage, face down, and spread the web
over the opening, keeping in place by ligatures tied to the
three longest toes, and fastened by binding posts on the
stage. Avoid stretching web too tightly, and keep it moist,
not wet. Place stage on microscope stage.

Examine first with a low power. If the blood is not seen
to circulate through the smaller vessels, the web has prob-
ably been stretched too tightly, or has been allowed to dry.
Decide which of the vessels are arteries, capillaries and veins,
■observing where the blood flows from large to small and
from small to large vessels, where the blood stream is most
rapid and where it pulsates. Do not let preconceived notions
cause you to think that you see what you do not really see.
As far as possible demonstrate the following phenomena
to an instructor:

I. Examine a small artery, and observe: —
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.

192 EXPERIMENT XXXIII.

III. Examine capillaries, and observe :

a. Frequent anastomoses.

b. Condition and behavior of corpuscles.

A. Red corpuscles (erythrocytes).

1. Shape, transparency, color. .

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

lar)^

3. Position of long ajKis 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.

IV. Vaso-motor Action.

Expose sciatic nerve, using the utmost care not to injure
the Hood 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. If the frog is well under the curara, 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 through 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 causes 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
oi the part. Then choosing a capillary whose walls can be
seen distinctly, watch carefully a leucocyte resting against

CAPILLARY CTRCULATION. I93

the wall, and obsen^e 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.

VI. The Capillaries of the Human Skin Will Be Demon-
strated.

194

EXPERIMENT XXXI II.

CILIA. 195

EXPERIMENT XXXIV.

Cilia.

Cilia play an important role, by supplying the motor
power to many forms of separate cells, and in moving sub-
stances along over the surfaces of mucous membranes lining
many of the passages and tubes of the body. The character
of the movement of the cilia is different in the case of differ-
ent cells ; in general four different kinds of movement are
described, viz., hook form, pendular, wave-like, funnel form.
The movement of the little protoplasmic process is generally
regarded to be a result of contractility, the contraction being
rapid and the recovery being somewhat slower; opinions
differ, however, as in the case of muscles, with regard to
the internal forces and method of action of the cell. The
contractions follow each other too rapidly to be followed by
the eye; Engelmann estimated the rate of vibration of the
cilia of the mucous membrane of the esophagus of the frog
to be twelve per second. As the cell begins to die, however,
the movements slow and the phenomenon can be studied.
Like all forms of protoplasm, the cilia-bearing cells have con-
ductivity, and this may persist after contraction has ceased.
The waves of activity take a definite course across a ciliated
mucous membrane, and when watched under a microscope,
call to mind the effect of wind blowing across a field of
grain. The harmonious action of the cells of a membrane
to move substances over the surface, suggests the passage
of a peristaltic wave along the intestine. In spite of their
microscopic size, the combined action of the cilia enables
them to accomplish considerable work, and it has been esti-
mated that one square cm. can move a load of 330 grams.
The rate of action is influenced by temperature ; weak acids
at first excite, and later slow and destroy action ; slight
alkalinity favors activity.

ExPilRiMRNT. Pith the brain and the spinal cord of a
frog; cut through the middle of the lower jaw, and extend

196 EXPERIMENT XXXIV.

the incision down the esophagus to the stomach; divide
this, and carefully dissect off the esophagus, pharynx, and
part of the mucous membrane of the mouth ; pin the edges
to a sheet of cork, so as to obtain a level field with the
inner surface uppermost. Rinse with normal salt solution.

a. Work of Cilia.

By means of pins fasten two threads across the mem-
brane, one cm. apart, and a short distance above it. Put
a small piece of cork on the membrane and see in which
direction it will be carried along, toward or away from
mouth end. Cut some small flat pieces of lead, and find
what is the greatest weight which can be moved by a given
surface of membrane. Tilt the cork plate and see if the
weights will be carried up hill.

b. Effect of Temperature.

Test the rate at which the small piece of cork will be
moved when the membrane is at room temperature, when it
is cooled and when it is warmed. (The temperature can be
<:hanged by placing sheet of cork with the membrane, in the
dish which will be provided, and by flowing over the mem-
brane normal salt solutions which are ice-cold, warmed to
25° C, and to 50° C.)

€. Microscopic Examination of Cilia.

Remove a few cells from the membrane by gently scrap-
ing it; put them in a drop of salt solution on a slide, and
study the movements of the cilia under a microscope. Re-
port the results of the above experiments in your notes.

crrjA.

197

igS KXPKRIMENT XXXIV.

ARTERIAI, PRESSURE IX MAN. I99

HXPERHJEXT XXXV.

Measurement of Systolic and Diastolic Pressure in Hu-
man Arteries.

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. The arterial pres-
sure at a given point depends on the amount of blood being
pumped by the heart, the condition of the arterial walls, and
the resistance to the passage of the blood through the small
arteries, capillaries, and veins of the body as a whole, and
of the artery where the pressure is to be measured. Since a
high pressure means excessive work for the heart, and since
a low pressure means too little blood is being pumped, or
that the vessels are abnormally dilated, it is evident that a
measure of the blood pressure is of great clinical importance.
In practice, it is assumed that the pressure of the blood in
the brachial can be taken as a measure of the condition of
the general blood pressure.

It is necessary to consider three forms of blood pressure.
During every systole, the heart drives blood into the arteries,
and at some time during the systole the maximal pressure
for that beat is reached, and this would be the systolic pres-
sure for that cycle. During the diastole of the ventricle, the
blood flows out of the peripheral end of the arteries into
the capillaries, and just at the close of the diastole the
minimal pressure for that beat is reached, and this would be
called the diastolic pressure for that cycle. The pulse pres-
sure for a gii'en cycle is that which is added to the diastolic
pressure, by the systolic injection of blood into the arteries.
The systolic pressure for an}"- beat is, therefore, the sum of
the diastolic and pulse pressures for that beat.

In as much as the general arterial pressure is changing
from moment to moment, showing respiratory and Traube-
Hering waves, the individual pulse beats must be thought of
as superposed on these waves. The general systolic pres-

200 EXP1?;RIMKNT XXXV.

sure would be the highest pressure reached during any beat
on the crest (jf the highest blood pressure wave, and the
general diastolic pressure, the lowest pressure reached dur-
ing any beat in the trough of the lowest blood pressure wave.
The general pulse pressure would have to be considered as
the average of the pulse pressures of the separate beats
occurring during the time that the pressure was being
studied, and should be called the "average pulse pressure/'

The lateral expansion of the wall of an artery by the
blood pressure is resisted by the elastic forces of the wall.
If the diastolic pressure is low, the wall is lax, and can be
distended by the pressure added by each systole, and will
contract during the next diastole. In this case, slight oscil-
lations of the wall may occur. If the diastolic pressure is
high, or even normal, the wall will be kept so much stretched
all the time, that the added pressure of a systole will not
distend it much, and the pulse oscillations of the wall will
not 'be large enough to be detected by the eye. Nevertheless,
there will be oscillations of pressure which can be felt by the
finger pressing on the artery, or by a suitable apparatus.

Apparatus. — A sphygmomanometer is an instrument de-
vised to measure more accurately than the finger, the systolic
and diastolic pressures. Quite a variety of forms of this
apparatus are now used in practice. The one employed in
the laboratory, is a modification of the Erlanger apparatus,
(see Fig. 39). It consists of a wide rubber bag which is
placed on the inside of the upper arm over the site of the
brachial artery, and is held in place by an inelastic leather
cuff ; a tube from the bag communicates with an air-pump,
to blow it up, and raise the pressure which is to compress
the artery : a manometer to register the amount of pressure ;
a fine leak, to let the pressure fall gradually ; a larger leak to
let. the air out quickly. The air system is also connected
with a distensible rubber bulb, enclosed in a flask, and the
air in this flask communicates with a delicate, magnifying
tambour ; the arrangement is such that the pulsations of the
air in the bag over the artery are imparted to the bulb in
the flask, and through this to the surrounding air, and by
means of this to the tambour.

ARTEIiTAL PRESSURE: IN MAN.

20I

Method of Measuring the Systolic and Diastolic Pres-
sure.— The usual method is to compress the artery, by forcing
air into the bag until the manometer registers a pressure of
140 mm., or more, of mercury, one sufficient to stop the

Fig. 39. A laboratory form of sphygmomanometer. C, arm bag; P,
pump; M, mercury manometer; L, small leak; I, cock to shut off
pump ; 2, cock to shut off adjustable leak ; 4, clamp at large outlet ;
B, bulb expanding and contracting as pressure changes ; T, magni-
fying tambour recording pulse oscillations of bulb ; 3, clamp controll-
ing outlet of tambour

flow of blood through the artery, and then to let the air
escape from the system through a fine leak ; at the same time
the pressures shown by the manometer are watched, and the
pulse movements of the tambour are recorded. Several
different criteria have been adopted as indicating when the
systolic and diastolic pressures have been reached.

202 EXPERIMENT XXXV.

I. Systolic Pressure. The pressure at which the blood
breaks through beneath the bag, is considered the systoHc
pressure. But ail the criteria indicating that the blood has
forced its way beneath the bag, give inconstant results at
the critical point, because the pressure of the blood is under-
going respiratory variations, and with every rise of blood
pressure, the pulse wave breaks through, and during the
succeeding fall, fails to pass. The Traube-Hering waves of
blood pressure exert a similar influence, and add to the diffi-
culty of determining the systolic pressure with exactness.
Nevertheless the pressure can be usually measured with,
sufficient accuracy for practical needs.

a. Tactile Criterion. Shortly after the pulse breaks
through, it may be felt by the finger at the wrist.

b. ^-Auscultatory Criterion. Soon after the pulse begins to
pass the bag, one can hear with a stethoscope placed on the
skin over the artery just distal to the bag, a series of low
tones caused by the pulse wave acting on the collapsed ar-
tery. At first, faint, clear tones, or even clicks, are heard;
these are followed by faint murmurs, or a roughening of the
sound ; then a louder, clear sound may be heard again ; and
finally softer sounds which fade away. Periodic variations
in the arterial pressure nia)^ cause the first of these sounds
to disappear and to reappear, also the rate at which the pres-
sure falls in the bag may influence the duration and quality
of the sounds. The systolic pressure should be read when
the first sound is heard, and diastolic pressure at the point
where all sounds suddenly become less.

c. Criterion of a Sudden Rise of Pulse Record. When the
air is forced into the bag, the pressure in the bag acts with
the elastic force of the arterial wall to overcome the pres-
sure of the blood in the artery. As the walls of the artery
are forced together, the elasticity of the wall of the artery
plays less and less part, and finally the pressure in the bag
alone opposes the pressure of the blood in the vessel. If
the pressure is raised sufficiently to overcome the highest
pressure in the artery, and prevents the blood from entering
the part of the vessel under the bag, the bag pressure would
be greater than systolic, (see I, Fig. 40) and in this case

ARTEEIAI, PRl-SSURE IN MAN.

20'

?..(TH

SDP

iin

N\^^.^K^^

J 15

iz

there would be no pulse oscillations of pressure in the air in
the bag, except very small pulsations, caused by the end
of the compressed artery beating against the side of the bag.

If now the pressure is
lowered very gradually, the
blood will begin to w^ork
into the artery beneath the
bag, (see II, Fig. 40). Von
Recklinghausen pointed out
that if the pressure in the
bag falls moderately rapid-
ly, there usually comes quite
a sudden rise in the height
of the recorded pulse beats,
at the instant that the blood
forces its way into the part
of the artery under the bag,
and when this occurs it
would seem to be a good in-
dication of the systolic
pressure.

d. . . Criterion of Separation
of the Ascending and De-
scending Limbs of the
Pulse Curvc.^ Another piece
of evidence is to be found
in the shape of the pulse
obtained with the tambour.
Erlanger states that if the
record be taken on a drum
moving not too slowly, at
the moment that the pulse beats begin to work under the
bag, the up and down strokes are to be seen to separate, and
that this separation is to be taken as the criterion for the
systolic pressure.

II. Diastolic Presure.

a. The Auscnlatory Criterion. The sudden lessening of
the sounds heard over the artery, distal to compression of
the bag. as the pressure in the bag falls.

°, A iyviv4v,LQ':-^^>~j;^-sf ststKf?

"i

Fig. 40. Diagram showing how
varying pressures in the bag, by act-
ing against the systoHc, diastolic, and
pulse pressures, alter the tension of
the wall of the artery, and consequent-
ly the pulse oscillations of the air in
the bag and the tambour record. A,
artery; B, bag; D, diastolic pressure;
S, systolic pressure ; _P, pulse pressure ;
I, pressure in bag is more than sys-
tolic ; II, pressure in bag is less than
systolic, and more than diastolic ; III,
pressure in bag is diastolic ; IV, pres-
sure in bag is less than diastolic.

204 f:xpe;rimf,nt xxxv.

b. The Largest Pulsation Criterion. As the pressure
in the bag is lessened, the recorded pulsations of the air in
the bag grow in height, till a certain maximum is reached,
and then begin to decrease. How is this to be explained?
After the blood has worked into the artery beneath the bag,
the amount that the wall of the artery is stretched by the
pressure of the blood during S3^stole and diastole, depends
on the amount of the pressure in the bag plus the elastic
resistance of the wall of the artery, on the one hand, and
on the amount of pressure in the blood during systole and
during diastole, on the other. As the pressure in the bag
falls, the arterial wall gradually losing this support, is
stretched more and more, and has to sustain more of the
blood pressure. As the pressure in the bag continues to
lessen, a point is reached when the pulsations recorded by
the tambour are greatest, (See I, II, III, Fig. 40.) At this
point the pressure in the bag is just able to overcome the
pressure in the artery at the time the pressure is diastolic,
but not able to overcome the systolic pressure, therefore,
the air pressure in the bag oscillates between the diastolic
pressure and the pressure caused by the distension of the
artery during systole. TJte pressure, at which the greatest
pulsations are seen, is considered the diastolic pressure.

As the pressure in the bag falls further, the elasticity of
the wall of the artery is called on more and more to resist
the diastolic pressure, and the air in the bag is subjected
less and less to the systolic presure. (See IV, Fig. 40.)
For a considerable time, however, the pressure in the bag
aided by the elasticity of the wall of the artery can equal
the diastolic pressure, and the pulsations of the tambour
can show the diastolic part of the curve, although the wall
of the artery resisting the systolic pressure more and more,
the air in the bag is affected less by this, and the tambour
tracing shows less and less of the s3'stolic part of the curve.

As the pressure in the bag falls still lower, the elastic
wall has to support the blood pressure still more, and the
pressure in the bag and the movements of the tambour fail

AKTKKIAL PRESSURE IN MAN. 205

more and more to follow the diastolic part of the curve,
and finalty the arterial wall alone acting against the pres-
sure in the artery during diastole, no movement of the tam-
bour will be seen.

EXPERIMENT.

I. Systolic Pressure, as Determined by a Pulse at the
Wrist (Tactile Criterion).

First become familiar with the apparatus, (see Fig. 39),
and its method of operation. The leak tube L has been ad-
justed so that the mercury in the manometer will fall at
such a rate that the pressures can be easily read for every
5 mm on the scale, i. e., for every 10 mm fall of pressure.

a. Subject seated. Open clamp 3, (this is to be always
open except when records from the tambour are required).
The subject should be seated and quiet, the left arm being
flexed at a right-angle, and the forearm being supported by
a sling. Strap the bag over the site of the left brachial ar-
tery and see that it is wholly covered by the leather cuff.
Examine the pulse in the wrist, so as to be sure of the point
where it is felt most strongly. Open the cock I (on the
tube connecting with the pump) and close cock 2, (on leak
tube) and close clamp 4, (on outlet tube). Raise pressure
in bag by pumping until mercury in manometer stands at
140 mm., i. e., 70 mm. on the scale. Then close cock i, and
open cock 2. With nnger on wrist, watch the fall of the
mercury and note the exact point at which the first pulse
beat is detected. Five good readings are required.

b. Subject standing.

Determine the systolic pressure with the arm in same
position as in a. Be ready to take the reading as soon as
the subject gets up, and continue to take readings at regu-
lar, short intervals. Five good readings required.

c. B,ifect of Exercise.

The subject is to run rapidly down and up stairs. The
cuff is to be detached from the instrument, and is to be worn

2o6 EXPERIMENT XXXV.

during the run. The readmgs are to> be taken as soon after
the run as is compatible with accuracy. Five readings
should be taken at regular short intervals.

Notes.

The figures obtained in the three cases and their aver-
ages are to be recorded in the notes, together with explana-
tions of the differences observed.

II. Systolic and Diastolic Pressures by the Auscultatory

' Method.
The experiment is to be made when the subject is in the
sitting position, and in the same way as in a of the preced-
ing section, except that, instead of the pulse at the wrist
being taken, the sound given out by the artery below the
cuff as the pulse beats enter it, is to be listened for. A
stethoscope is to be used to hear the sounds (use your own
if possible; if forced to use another, see that the ear pieces
are well cleaned.) The first sound heard, is a clear sound,
often a distinct click ; later, the sounds are roughened, or are
more like murmurs, with perhaps some clear sounds inter-
spersed; and finally clear sounds are again heard and these
gradually fade away. Five tests are to be made. Let sev-
eral minutes elapse between the tests, to permit the effects
of congestion to pass off.

a. Systolic Pressure.

The manometer is to read at the instant that the first
pulse beat is heard. This marks the systolic pressure.

b. Diastolic Pressure.

A second reading is to be taken at the moment the
sounds are fading away. This marks the diastolic pressure.

III. Systolic and Diastolic Pressures by the Tambour

'Method.

Arrange a time signal to write in the same vertical line

and beneath the lever of the tambour, and connect the signal

in the circuit with a Morse key and a dry cell. The subject

is to sit quietly. The apparatus is to be used as before,

ARTliRIAI, PRKSSURE IN MAN. 207

except that the outlet from the tambour, cock 3, (see Fig.
39) is to be closed, so that the pulsations of the air about
the bulb in the bottle will be communicated to the tambour.
Record on a drum, running about 5 mm per second, a curve
of the movements of the tambour.- Start with a pressure
about 20 mm above the systolic pressure found in the tests
of the preceding sections. While the record is being taken,
and the pressure is falling, tap on the key, so as to mark
every 5 mm fall of the mercury in the manometer, and give
a double tap at the 100 and at the 50 mm points.

a. Systolic Pressure.

Mark on the curve after it is shellaced the point when
the pulsations suddenly begin to increase in height, (von
Recklinghausen's criterion). Also mark the point when the
up and down strokes begin to separate (Erlanger's crite-
rion).

b. Diastolic Pressure.

Mark the place where the pulsations are greatest, or
rather where they first begin to lessen in height.

208

IsXPr^R I M I'.NT XXXV.

ARTERIAI, PRKSSURi; IN MAN, 209

IvXPERIMKNT XXXV.

PLETHYSMOGRAPH. 211

EXPERIAIEXT XXXVI.
Conditions Changing the Volume of Hand.

The size of the arm or the finger, Hke that of most of
the organs of the body, is continually changing. It is in-
fluenced bv all conditions altering the general arterial pres-
sure, and by local changes in the blood-vessels, and lymph-
atics of the part itself. If the arm or a finger be enclosed
in an air-tight chamber, and the chamber be connected with
a sufficiently delicate recording apparatus, the changes in
volume can be Avritten on a kymograph drum. The record
will show pulse waves superposed on respiration waves,
and these often will be seen to be superposed on Traube-
Hering waves.

Changes in the blood pressure, caused by vaso-constric-
tion or dilation in other parts of the body, especially in the
abdominal organs, or vaso-constriction or dilation of the
part itself, will also change the height of the curve. Thus
psychic activity of an emotional tA^pe, will cause constriction
of the vessels of the arm and a fall of the curve ; cold ap-
plied to other hand, through the eitect of a crossed reflex
on the vessels of the part, will cause vaso-constriction and a
lessened volume.

Apparatus. — This consists of a glass receptacle in which
the arm or finger is placed, the space between the end of
the tube and the member being closed off by a rubber
sleeve. In the case of the finger the best results are to be
obtained by connecting the chamber' with a delicate piston
recorder. In the case of the arm, a recorder capable of
accommodating larger volumes of air has to be employed.
Directions for the use of the apparatus will accompan}- it.

Caution.

The tube leading to the recorder sJwiiId be kept closed,
and the tube which communicates with the outside air should
be kept open, except when the experiment is to be made.

212 EXPERIMENT XXXVI.

The syringe, which connects with a side branch of the
main tube can be used for fine adjustments of the air vol-
ume in the chamber.

Since the chamber is filled with air, it is very sensitive
to temperature changes, and when the part is first intro-
duced, the outlet tube must be left open until the system has
/^adjusted to write below the recorder, and be connected with
( a dry cell and a key, so that the time of changes of condi-
^{taken on the new temperature. A time signal should be
tions likely to influence the subject may be registered. The
pain caused by a tetanizing current applied to the skin by
a dry wire brush will be employed, and the brush should be
connected with the secondary coil, ready for use.

Experiment. — Good results are to be obtained only
when the hand is 7uarm, for if the vessels are constricted,
only very slight or no changes in the volume will be ob-
served. The subject is to sit at ease and the left arm or
the second finger of the left hand is to be used. See that the
side tube is open and that the clamp protecting the recorder
is closed. A sleeve having been chosen, which will make
the opening between arm or the finger and the chamber air-
tight, but without constricting the vessels, place the part in
the chamber. Let the subject sit quietly while the air is
taking on the new temperature. After five minutes, open
the clamp to the recorder, and then provisionally close the
outlet by pinching the tube. The record should show pulse
beats and respiration effects. To obtain the best results,
the friction of the pointer on the drum must be reduced to
a minimum. In case the record is rising rapidly again open
the escape tube, and wait for the temperature to become
adjusted. The drum should move at about the rate of 2 mm
per second. When a normal quiet record has been taken,
the efl:"ect of the following influences may be tried:

a. Tickling.

Brush the face lightly with the corner of a strip of paper,
and record the time, by pressing on the key during the peri-
od of stimulation. The corners of the mouth are especially
ticklish. The subject must avoid movements.

PLKTHYSMOGRAPII. 213

b. Pain.

Connect the primary coil of the induction apparatus in
the circuit with the electric signal, dry cell, and key. Let
the experimenter test the strength of the current to be em-
ployed by applying the brush to the skin of the back of his
own hand, and increasing the strength of current until it
is decidedly unpleasant. Now the secondary coil should be
pushed back a short distance, the brush applied to the back
of the hand of the subject, and a strength of current found
which is as much as he wishes to stand. Wait about three
minutes : then try the effect when the drum is running and
a good normal record is being taken. The subject must try
to avoid making any movements at the time. Remove coil
from signal circuit and restore signal key.

c. Psychic Excitation.

When "quiet" records are being taken, the effect of
psychic activity may be studied by letting the subject try to
multiply 47 by 82, for example, and give the answer as
quickly as possible. Record on the drum the instant that the
problem is stated, by pressing on the signal key and keep
it down until the instant that the answer is given.

d. Cold : —

Half fill a glass jar with ice cold water. Place jar on
floor below suspended right hand of subject. After the
hand has been in this position for two or three minutes ex-
amine the veins and make note of the color of the hand.
When a "quiet" record is being taken, let a third student
raise the jar, so that the hand of the subject will be im-
mersed. The subject himself should make no movement.
Record on the drum the instant that the jar is raised, and
continue to press on the recording key until the jar is low-
ered. The muscles of the walls of the vessels are non-stri-
ated and slow to act. Three or more seconds are necessary
for the first change to appear. Examine the hand again,
making note of the color of the hand and amount of con-
striction of the veins.

214

KXrERIMTjNT XXXVI.

VENOUS TRKSSUR];. 215

EXPERIMENT XXXVU.
Venous Pressure in Man.

Under normal conditions, the pressure of the blood in
the veins at the level of the upper border of the heart is
very low. According to v. Recklinghausen, when a person
is in the recumbent position, the level of the large veins at
the point of entrance intO' the heart can be considered to be
7-1 1 cm dorsal to the sternum. If a normal man is lying
down and places one hand on the bed and the other on the
thigh, it will be found, after the few minutes required for
adjustment, that the veins of the hand on the bed are some-
what distended, and those of the hand on the thigh are
empty. If this is observed, the pressure can be regarded
as normal. In case the veins of the hand on the thigh are
distended, the pressure is above the normal.

Gaertner's method of measuring the venous pressure re-
quires no apparatus and is sufficiently accurate. In order
that the blood may flow to the right heart, the pressure must,
at least, be equal to that of the blood in the veins at the
level of the upper border of the heart. This point, in the
upright position, can be considered to be at the height of
the second intercostal space, (See Fig. 42).

The pressure of the blood in the veins of the hand at a
given point would depend on the amount of energy left in
the blood after it had passed the capillaries, and the resist-
ance which it would encounter on its way to the heart. This
latter factor would be composed of the resistance of the
blood pressure in the veins at the heart, (which it is pro-
posed to measure), plus the weight of the column of blood
which would have to be lifted, plus the resistance offered by
the walls of the veins. N^eglecting this last factor, which we
can not measure, the pressure of the veins in the hand,
minus the weight of the column of blood from the hand up
to the heart level, if the hand was lower, or plus this weight.

2l6 EXPERIMENT XXXVII.

if it was higher than the level of the heart, would give the
venous blood pressure at the heart.

Experiment. — Let the subject sit erect in a comfortable
position, and with his left arm on the lowered arm rest.
Determine the height of the upper border of the heart, by-
adjusting the lower border of the horizontal meter stick to
the level of the second intercostal space. Raise the arm
rest to about lo cm below this level, and wait two minutes ;
then, moving short distances and waiting two minutes be-
tween each test ascertain the height at which the largest
veins collapse. Measure this height, and state in the notes
the difiference between this and the heart height, and report
the figures obtained and the pressure of the venous blood
at the heart in mm Hg. Blood is 5% heavier than water.
Mercury has 13.6 times the weight of water. Note the tem-
perature of the room, the time of day, and any other condi-
tions that might influence the result.

VENOUS prrssurf;. 217

21!

F,Xrr,RlMF,NT .XXXV'II.

Vl'NOUS I'UJ.SK 219

EXPERIMENT XXXVIII.
The Pulse in the Large Veins of Man.

The pulse detected in the large veins of the neck is of
great clinical interest because it gives information with re-
spect to the action of the right auricle and ventricle, just as
the arterial pulse gives information concerning the left ven-
tricle. Before trying to obtain a record of the pulse, study
the diagram in Fig. 41, so as tO' know the form of the curve
to be sought, and its relation to the carotid pulse, and to the
systole and diastole of the right auricle and ventricle.

• Apparatus. — The venous pulse is recorded by an open
tambour, or one closed by a thin, loose, rubber membrane,
connected with a delicate, magnifying, recording tambour;
the carotid pulse is recorded as in Experiment XXX. From
the start, both of the recording tambours must be adjusted
so that their levers are horizontal, i. e., with the writing
points on a level with the axes. The length of each lever
is to be measured, after it has been applied to the drum in
the position in which it is to write. Place a fork so as to
write below the two levers.

Experiment. — Let the subject lie on his back, and seek
the A^enous pulse by applying the receiving tambour to vari-
ous points over the veins of the neck, avoiding only the re-
gion over the carotids. Try first over the external jugular.
Occasionally a good pulse is got by deep pressure in the
supra-sternal notch. The position of the head is important,
and often various positions must be tried before one suita-
ble to the subject will be found. The muscles of the neck
should be relaxed, and conditions favorable to a large flow
of venous blood, such as a warm room, are desirable. The
best result is usually obtained by a low heart rate. When
a pulse, at least 5 mm high, and evidently different from
that to be expected from a carotid, has been obtained, ap-
ply a tambour over the opposite carotid and record simultan-
eously the venous and arterial tracings, and the vibrations of

220 F.XPI;RIMKNT XXXVIII.

DESCRIPTION OP PIGURK 4I.

Diagram showing relations of changes in size of the
right auricle and ventricle, to the venous pulse, carotid pulse,
time of heart sounds, and time of closure of valves. I, ven-
ous pulse curve; TI, carotid pulse curve; III, changes in
size of auricle and venticle ; x — x, resting position of floor
of auricle; IV, duration of systole of auricle and ventricle;
A.S., auricular systole; V.S., ventricular systole; A.D., auri-
cular diastole ; V.D., ventricular diastole ; V, time of heart
sounds, first, second, and third ; VI, time of opening and
closing of valves; tc and mc, tricuspid and mitral close; ao
and pOj aortic and pulmonary open ; ac and pc, aortic and
pulmonary close; to and mo, tricuspid and mitral open; A,
pos, first positive wave of venous pulse, caused by auricular
systole ; A, neg, first negative wave, caused by auricular
diastole; S, pos, second positive wave, caused b}^ protrusion
of tricuspid valve into auricle, at beginning of ventricular
systole ; S, neg, second negative wave, caused by descent of
floor of auricle : O, first onflow wave, caused by accumula-
tion of blood in the veins ; V, pos, third positive wave,
caused by return of floor of auricle at beginning of ventri-
cular diastole; V, neg, third negative wave, caused by fill-
ing of ventricle ; h, second onflow wave, caused by accumu-
lation of blood in the veins.

VENOUS PUI.SK

221

II

IIIX

IV

VI

Fig. 41. Diagram showing relations of changes in size of the right auricle
and ventricle^ to the venous pulse, carotid pulse, time of heart sounds, and
lime of closure of valves.

222 EXPERIMENT XXXVIII,

the fork. At the instant that the tracing is to he taken, let
the subject cease to breathe at the end of a quiet expiration.
He must merely avoid taking the next breath, and not strain.
Do not fail by each test, to mark on the drum the exact po-
sition of the writing points, by recording large arcs. Also
record base lines by revolving the drum when the side tubes
are open and the levers horizontal.

Analysis of Ciirves.

First make sure that each of the levers was horizontal
when the base lines were written, by applying dividers, ad-
justed to the length of the lever, to the base line, and seeing
whether it will describe the arc as written. Do not deface
the arc in the process. Then draw a vertical line, just tan-
gent to one of the arcs, to ascertain the relative position of
the writing points. Now draw an arc from the beginning
of each of the positive and negative waves of the venous
pulse curve, and from the beginning of the rise of the pri-
mary wave and from the bottom of the dicrotic notch of
the carotid pulse to the respective base lines. Perpendic-
ulars may now be drawn down tO' the fork curve, from the
points the time relations of which are to be compared.

For laboratory purposes, at least, it is best to use the
above method, but many physicians find it simpler, when
the relative position of two points on two curves is to be
studied, instead of drawing perpendiculars, to measure with
dividers the distance between the point where the arc from
one of them intersects its base line, and the starting point
arc, and then to la}^ off this distance on the other base line,
from the starting point arc drawn by the other lever. In
any case arcs must be drawn from the parts of the curves
to be considered, to the respective base lines.

Notes. — ^State whether in your record the S wave began
to rise at the same time as the primary carotid wave, and if
not, wh}^ What was the relation of the V wave to the de-
scending limb of the dicrotic notch? Explain. Determine
the time interval betv/een the beginning of the rise of the A
and the S waves. This is approximately the time taken for
the conduction of the impulse through the auricle to the
ventricle.

NORMA!, SOUNDS OP HEART.

223

EXPERIMENT XXXIX.
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 es

Fig. 42. Diagram showing position of heart in chest, 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.

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

224 EXPEJRIMKNT XXXIX.

avoided, are apt to arise from (i) rubbing of tubes against
each other or against clothing, (2) breathing by the Hstener
upon the metal spring holding the ear-tubes, (3) movement
of the receiving disk upon the skin, (4) movements or
breath sounds of the subject, and (5) talking by either sub-
ject 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 first time, to avoid possible infection.
The tubes are placed in the ears with the tips pointing in-
ward and upward. The receiving disk is held firmly against
the skin. Avoid kinks in the rubber tubes.

Figure 42 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, knov/n 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 com-
posite sounds heard at each area. It is the relative loudness
of particular sounds that give the areas the nam.es which
the}^ bear.

a. Auscultation over the Lower 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 heart sounds for
several minutes. Observe (i) the two distinct sounds with
a ver}- short interval between them, (2) the greater loudness
of the first sound, (3) the booming 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 sound, composed of the click caused

NORMAL SOUNDS OF HEART. 225

by the closure of the two aitricnlo-ventricular valves, the
sound made by the contraction of the muscular substance of
the two ventricles, and by the vibrations of the suddenly
tensed chorda; tendine?e. The muscular element which pro-
longs the sound into the period of systole, helps to give it
the booming character. Normally the two ventricles con-
tract together, and the mitral and tricuspid valves close at
the same instant, so that the action of the two sides of the
heart is represented 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 contract rhythmic-
ally. 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 tri-
cuspid 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 loud-
ness 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 gradually shade off into those of the
other.

h. Auscidtation. 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. Move the disk to the
four areas in turn, and let the listeners try to recognize the
area by the sounds heard. Use each student as subject.

In diagnosis it is often necessary to locate an abnormal
sound in relation to the pulse beat and thence to the heart
cycle. The first sound, produced by contraction of heart
muscle and closure of auriculo-ventricular valves, is evident-

226 EXPERIMENT XXXIX.

ly systolic. The second sound, made by closure of semi-
lunar valves, is evidently diastolic. Therefore, any sound
occurring between the beginning of the first and the begin-
ning of the second normal sounds must be systolic, and any
sound occurring between the beginning of the second sound
and the beginning of the first sound of the next cycle must
be diastolic.

c. Tiyne Relations of Heart Sounds, the Cardiogram and
Pulse Ciirve.

The Cardiogram.

The apex of the heart comes in contact with the wall of
the chest at a point a little inside of the mammary line in
the fifth intercostal space, and if a receiving tambour or a
cardiograph is applied over this region, where the apex beat
is best felt, and is connected with a recording tambour, a
curve can be obtained which is the combined result of
changes in the position, form and volume of that part of
the heart. The form of the curve depends, therefore, on
the condition of the chest wall, the relation of the heart to
the wall, and the changes which the heart undergoes during
its action.

The cardiogram, Fig. 43, can be divided into five parts,
a wave caused by distention of the ventricle when the auricle
completes the filling of the ventricle, the auriculo-ventricular
valve closing at the end of auricular systole, (see first dotted
line) ; a more or less sharp rise, marking the period of ris-
ing tension in the ventricle, between the beginning of the
contraction and the opening of the aortic valve (see second
dotted line) ; a period during which the ventricle is driving
the blood out, the aortic valve closing soon after the end of
this period. (See end of 0.4 sec.) ; a more or less abrupt fall
caused by the sudden relaxation of the ventricle, the auricu-
lo-ventricular valve opening at some point during the fall
(See third dotted fine) ; a period corresponding to the grad-
ual filling of the ventricle.

The rise of the carotid curve, allowing for the time of
transmission occurs a short time after the beginning of sys-
tole ; and the descending limb of the dicrotic notch, which

NORMAL SOUNDS OF HKART. 22/

marks the end of the systole, occurs in the course of the
descending limb of the heart curve. The record of the
radial pulse would of course come somewhat later. The
first sound of the heart should occur at the beginning of the
fall of the wave caused by the auricular contraction, and the
second sound should occur at the beginning of the fall of
the curve caused by the relaxation of the ventricle.

Experiment. — Record a cardiogram and a radial and
carotid pulse curve on a drum along with that of 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 sig-
nal 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 three other curves. The subject should cease to breathe
just when the record is to be taken, by holding the breath,
without straining, at the close of a quiet expiration. 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 listening a short time
and then tap at the instant that the heats are to he expected.

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 ob-
serve that the primary wave of the radial pulse begins about
half way between the two heart sounds. It is evident, there-
fore, 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.

228 r;xpr;RiMi;NT xxxix.

DESCRIPTION OF FIGURE 43.

The diagram assumes that a normal heart is beating at
the rate of 75 per minute, and that one complete cycle occu-
pies eight-tenths of a second. Each of the spaces enclosed
by the unbroken lines is o.i second. In the horizontal space?
we see the duration of the systoles of the auricles and ven-
tricles, and the period of diastasis ; the time of occurrence
of the heart sounds : the periods when the valves are open,
the upper blank space covering the interval when the semi-
lunar valves are open, and the lower blank spaces the inter-
val when the auriculo-ventricular valves are open ; changes
in the form of what may perhaps be regarded as a typical
cardiogram ; the waves of the venous pulse ; two serial views
of the form changes of the auricles and ventricles of the
right heart, the large arteries, and the position of the heart
calves, (the upper series illustrating the action of the heart
with respect to the associated waves of the venous pulse
curve, and the lower picturing the relation of the heart to
the pressure waves in the arteries) ; finally, at the bottom
■of the chart, a sphygmogram of the carotid pulse. The
horizontal lines just below each of the hearts represent the
chest wall.

The vertical broken lines enclose a space between the
0.1 and 0.2 second, when both semilunar and auriculo-ven-
tricular valves are closed, (see heart 2) ; and during the 0.5
second a similar space is enclosed marking the interval when
the ventricle is again shut off from both auricle and artery,
(see heart 6).

Of course the schemes of the heart action are purely
diagramatic; the ninth heart picture of the lower series
would be a truer representation of the heart. Although the
right heart is supposed to be represented, only two curtains
of the tricuspid valve are shown ; the pulmonary artery is
made to He in close contact with the right auricle, although
as it winds around the aorta, it is the aorta which is most
intimately related to the wall of the right auricle ; the right
ventricle is represented as forming the apex of the heart,
although in fact it is. the tip of the left ventricle that is the
apex.

NORMAL SOUNDS OF HEART.

22g

SYSTOLE
SOUNDS
VALVES OPEN

CARDIOGRAM

VENOUS PUL3:

RIGHT HEART

CAROTID PUI,SH

Fig. 43. Diagram of a heart cycle, showing form changes of right side of
heart in relation to the cardiogram, the venous and arterial pulse, and the
iieart sounds.

230

KXPTvRIlMKNT XXXIX.

INFLUENCES AFFECTING RESPIRATION. 23I

EXPERIMENT XL.
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 by special rubber tubes
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. Normal 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 minute. Natural,
unconscious breathing is what we wish to study, and hence
the subject should try to think of something else.

b. Effect of Using the Voice.

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. Always 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.

r. Inhibitory Effects of Sivallozving.

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

d. Effects of Effort.

In the same manner observe the effect of trying to hold
two pin points as close together as possible wnthout touching,

232 EXPERIMENT XL.

for 15 seconds; of clenching the fists as tightly as possible
for 15 seconds; of clenching the fists as rapidly as possible
for 15 seconds; of pressing the hands upon the knees strong-
ly for 15 seconds.

Note the efifect in the different 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 :

(i) Relative rates of heart and respiration under nor-
mal conditions, sitting quietly.

(2) Effect of mental excitement.

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 acctistomed 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 associate.

INFLUKNCKS AFl-'CCriNG RESPIRATION. 233

234

T';xi'J';rimi-;nt xr,.

MEASUREl\rENT OF EXPIRED ATR.

235

EXPERniENT XIJ.

Measurement of the Expired Air.

The air which is breathed by quiet respirations, the tidal
air, averages only about 500 cc., and of this amount, only
about 360 cc. reaches the alveoli of the lung, the rest re-
maining in the bronchi and upper air passages. By deeper
respirations much more air is taken in and given out, and
it is possible by forced inspirations to breathe in 1,600 cc.

Vital
Capacity

3700

Complemental 1600
Forced Inspiration

Dead Space

140

Entering alveolse - 360

Tidal
500

Supplemental 1600
Forced Expiration

Residual 1000
Escapes when thorax is opened

Minimal — Imprisoned Air

Reserve
2600 -|-

more, the complemental air, and to breathe out 1,600 cc.
more, the supplemental air. The sum of the tidal, supple-
mental, and complemental air, gives what is known as the
vital capacity, 3,700 cc. Ordinarily there remains in the
chest 2,600 cc, the reserve air, of which 1,000 cc, the resid-
ual air, cannot be expelled by a voluntary effort, but will
leave the lungs when they collapse on the opening of the

236 EXPERIMENT xLI.

thorax, and a. small quantity, the minimal air, which even
then does not leave the lungs, but will be imprisoned by the
collapse of the bronchi, (See i, Exper. XXVIII). These
figures are only rough averages, and the values found for
different individuals differ greatly.

By means of the air breathed we take in oxygen, and
give off carbon dioxide gas, water, and heat. The necessary
gaseous exchange would depend, not only on the amount of
active tissue, but on the activity of the tissue. Even when
no external work is being done, chemical compounds must
be broken down to supply the heat needed for the main-
tenance of the body temperature. The loss of heat is greater
for a child than for an adult, because the smaller the body,
the greater the surface in proportion to the mass. Vierordt
states that for a child one day old, the surface area is 812
sq. cm. for every kilo of body weight, and for an adult it is
301 sq. cm. The amount of katabolism and gaseous ex-
change should, therefore, be greater per kilo in the child
than the adult. The surface area is calculated from the

formula 12,312 x ^/g , G being the weight in grams. In

adults, the weight of inactive tissue, bones and fat, is so
variable, that the weight is not a good index of the amount
of active tissue and necessary gaseous exchange. The chest
measure may not give the story, because in many individuals,
respiration is largely diaphragmatic. Finally, the vital ca-
pacity depends not only on the present need, but on the way
the individual has lived. The length of the body is also a
doubtful standard of comparison ; never the less, the follow-
ing table from Vierordt is quoted, as giving an indication
of the way the vital capacity is influenced by size of body.
Experiment. — The apparatus will be understood by ex-
amining Fig. 44. Notice that the air enters the valve cham-
ber (F) through the lower valve, passes to the subject, and
is given off by him through the other valve to the outside,
if the stop-cock 5 is open, or to the spirometer, if the cock
is turned in that direction. On entering the apparatus it
collects above the water and raises the bell. Caution. — When
thf^ air is to be expelled aki'ays remove the rubber stopper
(C).

MEASUREME^NT OF EXPIRED AIR.

237

Vital Capacity and Size of Body

Height Vital

(cm.) Capacity (cu. cm.)

154.5- 157 2635

157 -159-5 2841

159.5 - 162 2982

162 - 164.5 3167

164.5 - 167 3287

167 - 169.5 3484

169.5 - 172 3560

172 - 174-5 3634

174-5 - 177 3842

177 - 179-5 3884

J 79 - 182 4034

182 4454

Differ-
ence

206

141

185

120

197

76

74

208

42

150

420

Average 3484

Average for every 2>^ cm. of length iii

a. Tidal Air.

It is difficult to determine the tidal air, because the char-
acter of the respiratory movements alters as soon as one

becomes conscious of them.
Take a fresh mouth-piece and
connect it with the apparatus,
and then adjust the rubber
between the teeth and lips, so
that an air-tight closure will
be obtained. Open the three-
way cock so that the air will
escape freely, and then hold-
ing the nose, breathe quietly
and as naturally as possible,
drawing in the air through
one valve and giving it out
through the other and the
open cock. When the breath-
ing seems to be normal, let your partner turn the valve at
the instant you have finished taking in an ordinary breath,
and then continue breathing as before but into the spiro-
meter. Count the breaths, note the amount that has been
expired, and calculate the average tidal air.

Fig. 44. Apparatus for measur-
ing the expired air. M, mouth
piece, consisting of a glass tube and
a piece of sheet rubber shaped to
fit the space between the teeth and
the lips ; V, valve chamber ; S,
three-way cock, permitting the air
to escape or to enter the spiromet-
er ; C, cork keeping air in spiro-
meter ; W, water in spirometer ,

238 EXPERIME^NT XU.

b. Snpple'inental Air.

Breathe quietly as before, holding the nose dosed, and
having the cock open, then at the end of a quiet expiration,
let your partner suddenly turn the cock toward the spirom-
eter, and empty your lungs as completely as you can. Make
at least three tests. Record in your notes the result of each
test and the average.

c. Vital Capacity.

Fill your lungs as completely as possible and then quietly
and steadily breathe all the air possible into the spirometer.
Make at least three tests, taking the largest volume expired
as the vital capacity.

d. Coniplemcntal Air.

This can be calculated by subtracting the sum. of the
average tidal and average supplemental air, from the vital
capacity.

Report the resu.lts of these experiments in your notes,
and try to find an explanation, in case your figures differ
widely from those given above.

MKASURKMKNT OP EXPIRED ATR. 239

240 EXPKRIMENT XT,I.

BODY TEMPERATURE. 24 1

EXPERIMENT XUT.

Regulation of Body Temperature.

Regulation of temperature depends on adjustment of
heat production to heat elimination, or vice versa. Heat
production results from the splitting up of chemical com-
ponds and oxidation processes in all active cells, but es-
pecially in the muscles, because of their greater mass. It
is well knov^m that the blood leaving an organ is warmer
than that entering it, that the rectal temperature is higher
after a meal, and that it may be increased a couple of de-
grees by active exercise. Heat is given off chiefly from the
skin and air passages, by conduction, radiation, and evap-
oration. It is believed by some observers that there are
special centers regulating heat production. The centers
which control the flow of blood to the skin, the activity of
the sweat glands, and the rate and depth of respiration reg-
ulate the elimination of heat.

Experiments.
a. The Loss of Heat from the Skin.

1. The loss by conduction, noticeable whenever one
touches a cold object, the cold points having their tempera-
ture suddenly lowered by the loss of heat in warming the
object.

2. The loss by radiation, can be readily observed by
bringing the palm of one hand close over the back of the
other, or close to the face, but without touching it, and feel-
ing the heat radiating from the warmer surface ; this warms
the air, and the heated air excites the warmth spots in the
skin.

3. The Joss by evaporation, can be recognized by moist-
ening the skin, putting the mouth close to it, and sucking air
in across the surface. Control this result by repeating the

242 EXPERIMENT XEII.

test at a place where the skin has not been moistened. The
evaporation is caused by the heat brought by the blcod to
the skin, and the heat is lost in evaporating the moisture.

b. The Loss of Heat from the Air Passages.

1. By conduction and radiation. This can be recog-
nized by simply breathing on the skin.

2. By Evaporation. This occurs in the same way, and
the moisture given up tO' the air in the process can be de-
tected in the moisture which will be deposited when one
breathes on a cold pane of glass.

The amount of heat lost by conduction and radiation
from the air passages and the skin, will depend on the
amount of blood flowing through the surface vessels, and
its temperature as compared with that of the object touched,
and that of the outside air ; and the heat lost by evaporation
will depend on the amount of moisture supplied to the sur-
faces b}^ the mucous membrane and the sweat glands, and
the degree of saturation of the air at the time. The body
temperature rises when the surrounding air is hot, and es-
pecially when it is moist and hot.

BODY TKMPKRATURE. 243

244 EXPERIMENT XUI.

ARTlFlCTAIv RESPIRATION. 245

EXPERIMENT XUII.

Artificial Respiration.

Nornjiilly air is sucked into the chest by enlargement of
the thorax in the antero-posterior and lateral directions,
and by the descent of the diaphragm, and is driven out by
the elastic recoil of the lungs, the walls of the chest and the
walls of the abdomen. The most usual form of artificial
respiration used for animals, is to force air rhythmically
through an opening in the trachea, into the lungs, by means
of a bellows or one of the many forms of air pumps, and
either to suck it out, or more commonly, let the elastic forces
of the soft parts drive it out through a valve or side open-
ing, (see Exper. XXIX, c.) One such form of apparatus, is
the pulmotor, which is intended to resuscitate men who are
partially drowned or asphyxiated, or are suffering from
extreme shock. The air or oxygen under suitable pressure
flows in through a mask, which covers the nose and mouth
and fits the face tightly, and then is sucked out.

Another method known as the insuflation method, which
is used on animals, forces a continuous stream of air, under
known pressure, through a tube which has been introduced
through the mouth into the trachea as far down as the
bronchi, the air escaping through the space between the tube
and the walls of the air passages. In this case, the air in the
lung is renewed by diffusion of the gases between the upper
bronchi and the alveoli. This method is especially of use in
experiments in which the chest must be opened and it is de-
sirable that the lungs should be quiet.

Another set of methods try to suck, instead of blow, the
air into the lungs. In this case, the negative pressure on the
outside of the lungs is rhythmically increased and decreased.
By one method, intended to make operations inside of the
chest possible, the subject is placed in a pneumatic cabinet,
in which the pressure of the air is varied by a pump, and

246 RXPKRIMENT XUII.

when the chest is opened, the changes in pressure in the cab-
inet cause contraction and expansion of the hmg, and the
^xpelHng and drawing in of the air.

Several methods which require no apparatus, have been
devised for artificial respiration of men. The best known
■of these carry the names of Marshal Hall, Howard, Syl-
vester, and Schaefer.

By the Sylvester method the subject lies on his back;
one operator cares for the mouth, keeping it free from mu-
cus; &c., and draws the tongue forAvard, by grasping it
wath a dry cloth or by forceps ; one or two other operators
expand the chest wall by raising the arms and swinging
them as far back, above the head as possible, and then com-
press the chest by bringing the elbows against the sides and
pushing down on them.

In the case of very young children, a modification of the
above method is quite effective. The hands of the operator
grasp the chest close under the arms, and then alternately
raise the chest wall by pushing the shoulders up and back-
ward by the ends of the thumbs, and compress it by pressing
on the lower part and sides of the chest with the base of
the thumbs. The head can be allowed to hang down, so the
tongue shall fall forwards.

The Schaefer method is eft"ective, and by far the simplest
for adults, (a similar method was proposed by Dr. Kedzie
of this state). Since by this method, the subject Hes in the
prone position with the face towards the side, fluids tend to
drain out of the mouth, and the tongue, falling forward,
does not interfere with the air passages. The operator
kneels at the side or across the subject, facing his head. He
places his hands on the small of the back, over the lower ribs,
■so that the thumbs nearly meet at the spine. Then keeping
the arms straight, he swings forward and brings the weight
of his body to bear on the back of the subject ; this compress-
es the chest, and by pushing the abdomen against the
ground, causes the vicera to force the diaphragm upward.
He then swings back and repeats these movements sloidy,
saying looi, 1002, 1003, by the forward swing, and 1004,

ARTlFlCrAI, RESPIRATION. 247

1005 by the backward swing. The rate should be 12 — 15 to
the minute. The forward swing produces an expiration,
and by the backward swing, the elastic forces of the chest
cause it to enlarge and produce an inspiration.

Experiment. — ^Each student is to act as subject and
operator, in order that he may gain a better knowledge of
where the pressure should be applied to be most efhoient.
Have the apparatus used to measure the tidal air
ready, and let the subject lie down on a sheet of cloth suffi-
ciently near the apparatus, so that the tube connecting with
the valve chamber, (F^ Fig. 44), easily reaches the mouth.

a. The Schaefcr Method.

Let the operator perform artificial respiration by the
Schaefer method, in the way that both he and the subject
recognize to be most effective. When the method has been
learned, let the subject breathe as near as possible normally
into the spirometer six or seven breaths. The amount re-
corded should be noted, and the amount of air that is given
out by a like number of artificial respirations should be
measured.

b. Effect of Apnoea.

Let the subject take 15 or 20 deep, rapid, forced respira-
tions, so as to thoroughly ventilate his lungs and blood, and
then immediately repeat the experiment of measuring the
amount of air given out by artificial respirations.

c. The Sylvester Method.

Repeat the work as described in a.

Notes.

State in the notes the figures obtained in the above tests
and explain any differences which may have occurred.

EXPERIMENT XIJII.

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