GIFT OF

TO THE

LIBRARY OF THE
MEDICAL DEPARTMENT

OF THE
UNIVERSITY OF CALIFORNIA

MEDICAL *SCH<Q>0L
LUBTRABSY

LABORATORY

IN

PHYSIOLOGY

WINFIELD S. HALL, PH. D., M. D.,

PROFESSOR OF PHYSIOLOGY, NORTHWESTERN UNIVERSITY MEDICAL SCHOOL

CHICAGO.

H/7
17

APPENDICES ON
TION AND

TWO

SIXTY ILLUSTRATIONS.

R

CHICAGO MEDICAL BOOK Co.

35-37 Randolph Street,

1897

COPYRIGHT, 1897,
BY WINFIELD S. HALL.

/
8.97

PREFACE.

American laboratories of physiology have usually been
established in medical schools after these institutions have
already associated histology with pathology, and physio-
logical chemistry with general chemistry. The problems
presented in those American laboratories of physiology,
which are departments of medical schools, are, therefore,
essentially the physical problems of physiology. And
such are the problems which occupy the major part of this
manual. The student who has but four years to devote to
the study of medicine cannot consistently be assigned
more than 100 hours to 120 hours of laboratory work in
physical physiology. How to most profitably spend this
brief period is a question which has engaged the attention
of the writer for a number of years.

In the choice of the work to be assigned to the student
it has been taken for granted that he has entered upon
his study of medicine with a working knowledge of physics
and of Algebra, and that laboratory work in physiology is
not begun until the student has made considerable prog-
ress in gross and minute anatomy. (Bourses in anatomy
and physiology should be so coordinated as to enable the
student to gain a thorough knowledge of the morphology
of an organ before he experiments upon its function.

The method of presentation is purely inductive. The
student is given the technique and, through a series of
questions, he is guided in his observations. He is not,
however, told what he is expected to observe, nor is he told

190

LABORATORY GUIDE IN PHYSIOLOGY.

what his conclusions are expected to be. On these points
he is left on his own resources. Repeated trial of this
method with different classes proves it to be most satisfac-
tory both to the instructor and to the student. It gives to
both free play for originality and individuality.

The manual as here presented is far from complete.
Should a second edition be justified, it will contain in addi-
tion to the present matter, chapters on Metabolism and
Animal Heat; Excretion; The Voice and Hearing; The Cen-
tral Nervous System; and, An Introduction to Physiological
Psychology.

The Author acknowledges his indebtedness to the
Chicago Laboratory Supply Co. and to Richards & Co. for
the cuts used in Appendix C. He takes this opportunity
to express his thanks to Dr. W. K. Jaques for preparing
the chapter on Physiological Haematology, and to Mrs.
Jaques for illustrating the same; to Dr. H. M. Richter for
the chapter on Pharmacology; to Dr. A. M. Hall for the
lessons on Normal Ophthalmoscopy and Skiascopy; and to
Miss N. S. Hall for the illustrations of the first six chapters.

THE AUTHOR.
CHICAGO, Sept. 30, 1897.

,, 190

mi

TABLE OF CONTENTS.

INTRODUCTION.

PART I. GENERAL PHYSIOLOGY.

A. The physiology of ciliary motion.

I. a. Normal Ciliary Motion 16

b. Ciliary Motion Modified by the Influ-
ence of Narcotics and Stimulants.
II. To Determine the Amount of Work done

by Cilia 23

B. The general physiology of muscle and nerve tissue.

III. a. Elements and Conductors.

b. Keys.

c. Commutator.

d. Work done by the Cell or Element.

e. Electrical Units of Measurement 26

IV. Batteries; Cells in Multiple Arc or in

Series; Relation of the Current to the
Method of Joining the Cells 30

V. Methods of Varying the Strength of Cur-

rent 40

a. The Rheostat.

b. The Du Bois-Reymond Rheocord.

VI. To Vary the Strength of Current through
the Use of (a) the Simple Rheocord, or
of (//) the Ludwig Compensator 43

LA BORA TOR Y G VIDE IN PH YSIOL OGY

VII. To vary the strength of an Electric. Current

Gradually. Fleischl's Rheonom 48

VIII. To Determine the Influence of the Kathode

and Anode Poles 51

IX. a. The Muscle-Nerve Preparation.

b. Indirect Mechanical, Thermal and
Chemical. Stimulation of the Gastroc-
nemius 56

X. Variations in the Method of Applying
Mechanical, Thermal and Chemical

Stimuli 61

a. Direct and Indirect Stimulation.
I). Qualitative Variation of Stimuli.

c. Quantitative Variation of Stimuli.

d. Variation of Length of Time of Ap-
plying the Stimulus.

XL Electricity as a Stimulus. The Galvanic

Current 75

XII. Stimulation with the Constant Current.

The Simple Rheocord 68

XIII. The Effect of Induced Current. Tetanus. 70
XIV. To Determine the Amount of Work Done

by a Muscle 73

a. The Work Done by a Single Contrac-
tion.

b. The Total Amount of Work Done by a
Muscle.

c. Reaction Changes in Fatigued Muscle.
XV. To Determine the Effect of a Constant

Current upon the Irritability of a Nerve.

Electrotonus 75

XVI. Pfliiger's Law of Contraction . . . . 80

PART II. SPECIAL PHYSIOLOGY.

C. The Circulation.

XVII. The Circulation and its Ultimate Cause. .. 85

a. The Capillary Circulation.

b. To Observe the Action of the Frog's
Heart.

XVIII. The Graphic Record of the Frog's Heart

Beat 89

XIX. The Apex Beat. The Heart Sounds. The

Cardiograph 91

XX. The Flow of Liquids through Tubes. Lat-
eral Pressure 93

XXL The Flow of Liquids through Tubes under
the Influence of Intermittent Pressure.
The Impulse Wave; Graphic Tests .... 98
XXII. The Laws of Blood Pressure Determined
from an Artificial Circulatory System.
Pulse Tracing from the Artificial System. 102

XXIII. The Human Pulse. The Sphygmograph.

The Sphygmogram 106

XXIV. To Determine the General Influence of the

Vagus Nerve upon the Circulation 109

D. Respiration.
XXV. a. External Respiratory movements 113

b. Intra-thoracic Pressure.

c. Intra-abdominal Pressure.

XXVI. Respiratory movements in Man 117

a. The Stethograph.

b. The Thoracometer.

c. The Belt-Spirograph.

d. The Stethogoniometer.

LABOR A TOR \ G U1DE IN PHYSIO LOG Y.

XXVII. Respiration in Man 124

a. Lung Capacity.

b. Strength of Inspiration and Expiration.

c. Chest Measurements.

d. Preservation of Data.

XXVIII. The Evaluation of Anthropometric Data.. . 127
XXIX. The Action of the Diaphragm 132

a. Stimulation of the Phrenic Nerve.

b. The Phrenograph and the Phrenogram.
XXX Respiratory Pressure 136

a. The Pneumatogram.

b. Stimulation of Pulmonary Vagus.

c. The Elasticity of the Lungs.

d. The Cardio pneumatogram.

XXXI. Quantitative Determination of the CO2
and H2O Eliminated from an Animal in

a Given Time 140

XXXII. Respiration under Abnormal Conditions. . 144

a. Respiration in a small closed space.

b. Respiration in a larger closed Space.

c. Respiration in an Atmosphere of CO2.

d. Post-mortem Examinations.

XXXIII. Respiration in Abnormal Media 147

a. Respiration in an AUnosphere ot Nitro-
gen.

b. Respiration in an Atmosphere of Hydro-
gen.

c. Respiration in an Atmosphere of one-
third Illuminating Gas.

d. Post-mortem Examinations.
E. Digestion and Absorption.

XXXIV. The Carbohydrates 153

XXXV. Salivary Digestion. , 157

CONTENTS. 5

XXXVI. The Proteids 161

XXXVII. a. The diffusibility of Proteids 166

b. Milk.

XXXVIII. Gastric Digestion 171

XXXIX. Gastric Digestion, Continued 177

XL. Gastric Digestion, Continued 180

XLI. The Properties of Fats 182

XLII. Intestinal Digestion 186

XLIII. Absorption 189

F. Vision.

XLIV. Dissection of the Appendages of the Eye. . 191

XLV. Dissection of the Eyeball 195

XLVI. Physiological Optics 198

a. Determination of the Indices of Refrac-
tion of Water and of Glass.

b. Determination of the Focal Distance of
Lenses.

c. Verification of the formula: 7— hp^f-

d. Problems.

XLVI I. Physiological Optics, Applied 210

a. The Application of the Laws of Refrac-
tion to the Normal Eye. "The Re-
duced Eye."

b. To Locate, Experimentally, in the Mam-
malian Eye the Cardinal Points of the
Simple Dioptric System.

XLVIII. a. Accommodation 216

b. Convergence.
XLIX. Miscellaneous Experiments 222

a. Scheiner's Experiment.

b. Purkinje Sansom's Images.

c. The Blind Spot.

LABORATORY GUIDE IN PHYSIOLOGY.

d. The Macula Lutea — Maxwell's Experi-
ment.

e. Shadows of the Fovea Centralis and
Retinal Blood Vessels.

L. Perimetry: The Light- perimeter, the Form-
perimeter and the Color-perimeter 226

LI. Determination of Normal Vision 232

a. The Acuteness of Direct Vision.

b. The Range of Accommodation.

c. The Amplitude of Convergence.

LIT. Normal Ophthalmoscopy — Direct Method. 247

a. The Emmetropic Eye.

b. The Hypermetropic Eye.

c. The Myopic Eye.

LIII. Normal Ophthalmoscopy — Indirect
Method. The Emmetropic, the Hyper-
metropic and the Myopic Eye 250

LIV. Skiascopy 252

The Emmetropic, the Myopic and the
Hyperopic Eye.
G. Physiological Haematology.

LV. Examination of Fresh Blood 259

LVI. Counting Red Blood Corpuscles — Thoma-

Zeiss Counter 262

LVI I. Counting White Corpuscles. Decoloriz-
ing the Red Cells 265

LVIII. Counting Red and White Corpuscles.

Staining the White Cells 268

LIX. To Determine the Relative Volume of Red

Corpuscles and Plasma. The Haematocrit. 270
LX. Estimation of Haemoglobin, v. FleischPs

Haemometer 273

LXI. The Microscopic Technique of Haematol-

ogy 276

CONTENTS. 7

a. Spreading Blood.

b. Fixing and Staining.

LXII. Differential Counting of White Cells and

of Red Cells 280

LXIII. Study of Bone Marrow 281

H. An Introduction to Pharmacology.

LXI V. Curare 285

LXV. Atropin 290

LXVI. Pilocarpin 293

LXVII. Strychnin 295

LXVI 1 1. Veratrin .--... 298

LXIX. Digitalis 300

LXX. Aconite 303

Appendix A.

Description of General Laboratory Appliances and

New Apparatus 307

Appendix B.

On the Organization and Equipment of the Depart-
ment of Physiology 321

Appendix C.

Figures and Brief Descriptions of Instruments 333

INTRODUCTION.

THE METHOD OF PRESENTING THE SUBJECT.

REGARDING ILLUSTRATIONS.

The profuse illustration of a text-book is in perfect ac-
cord with the principles of pedagogy; that the profuse
illustration of a laboratory manual is the reverse is evident
from the following considerations :

The laboratory student receives from the demonstrator
the material with which he is to work. If he receives
a piece of apparatus which is new to him, a few questions
or hints in his laboratory manual will lead him to discover,
from an examination of the apparatus itself, the physical
and mechanical principles involved and utilized in it.
Most students will spontaneously make drawings showing
the essential parts of the instruments; all students will
willingly do so if required. This is a most valuable exer-
cise for the pupil, which is likely to be omitted if the
manual contains cuts of the apparatus.

Nearly every exercise requires the preparation of some
simple appliance — e. g., a frog board or a recording lever
— whose construction will be much facilitated if the stu-
dent is guided by a figure in his manual, but a model
which the demonstrator has made will be a better guide.

I have often seen students read their text descriptive
of some organ — e. g., a frog-heart — and verify its state-
ments from the accompanying figures, leaving almost un-
noticed the object itself, which lay before them. A few
brief questions or hints would have led them to discover

10 LAB OR A TOR Y G UIDE IN PH YSIOL OGY.

from the object all of its essential features. Diagrammatic
anatomical figures are sometimes useful in a laboratory
manual, but true anatomical figures are worse than use-
less— they bar the student's independent progress. If his
laboratory manual contains illustrations of all apparatus
and tissues, and of such experiments as admit of graphic
records, the student makes similar drawings in his notes,
either unwillingly or dependently — frequently both. The
laboratory work is thus robbed of much of the benefit it is
intended to give the student. Independence and origi-
nality are completely defeated or aborted, except in the
case of the rare student.

If the laboratory manual contains graphic records of
experiments, much of the time of the demonstrator will be
consumed in explaining to the students individually why
the same physiological functions observed with slightly
different apparatus and under slightly different circum-
stances, may yield tracings which differ in minor detail
from those in the book. The energies of both demonstra-
tor and students will thus be partially diverted from their
legitimate channel.

If there are no tracings in the text, students will natur-
ally, by comparison of their tracings, discover the essential
and the nonessential features and will seek the cause of
the essential features of their tracings. After the student
has made these independent discoveries he is in a position
to gain the maximum profit from the comparison of his
own tracings with those which others have taken, and
from any explanations which the demonstrator may choose
to add.

It is evident then, that, from a pedagogical stand-
point, the laboratory guide should be sparsely illustrated.
On the other hand, the student's notes should be profusely
illustrated.

1NTR OD UCTWN. 11

REGARDING EXPLANATIONS.

What has been said regarding the illustrations of
apparatus and of results applies, in principle, to the ex
planation of physiological observations. As wheat is more
valuable than chaff, so is the independent discovery of a
principle by the student more valuable to him than its ex-
planation by a book or instructor. If the facts to be
observed and the principle involved be detailed and ex-
plained in advance, the student's power of independent
observation and investigation remains undeveloped.

THE FUNCTION OF THE DEMONSTRATOR.

It may be well to introduce this topic by a statement
of what the function of the demonstrator is not. It cer-
tainly is not to rob the student of the pleasure, exhilaration
and benefit of the independent investigation of a problem
by introducing each laboratory period with an enumeration
of the facts and principles which the work of the day is
expected to establish. Such an introduction is worse than
useless. The desirability of even asking the attention of
the entire class to introductory remarks on the general
bearing of the problem in hand is to be questioned. If
the problem is well chosen and the work in the physiolog-
ical laboratory properly coodinated with that in the
recitation room and lecture room and that in other de-
partments, its significance will at once be evident to the
intelligent pupil. If the introductory talk is omitted the
prompt student may begin at once, upon entering the
laboratory, the problem of the day, and will have a clear
gain of ten to twenty minutes. Any supplementary in-
struction or' hint may most profitably and ecomically be
written upon the blackboard.

Most of the experiments given in this book cannot con-
veniently be performed by one individual working alone.

12 LA B OR A TORY G UIDE IN PH YSIOL O G Y.

After some experimentation it has been found most advan-
tageous to divide the class into sections not exceeding
thirty students, and to subdivide these sections into divi-
sions of three students each. Each division is assigned a
table. The assistant demonstrator places the material
needed for any day's work either upon the table or where
it is readily accessible.

Nothing should be done for the student which he can
profitably do for himself. A small class with less limited
time may easily construct much apparatus in the work-
shop. No class is so large as to debar the members from
the privilege of constructing frog boards, tracing levers,
etc., (which may be done at the tables) and of setting up,
adjusting and readjusting all apparatus.

Nothing should be told a student which he can readily
find out for himself. The function of the demonstrator
is to guide the student by questions and by hints to dis-
cover facts and to formulate principles. Extended expla-
nations on the part of the demonstrator may instruct the
student, but they do not educate him.

HINTS TO THE STUDENTS.

It is a general principle that a student gets out of a
course what he puts into it, and with interest. If he in-
vests (1) intellectual capacity, (2) the spirit of inquiry
and investigation, (3) the power of logical reasoning, and
(4) the power to formulate conclusions; he will promptly
receive interest upon the investment. Further, the greater
the investment the greater the rate of interest. This may
seem inequitable, but it is inevitable.

The value of taking full notes of laboratory experiments
is unquestionable. The following hints regarding note
taking may be advantageous:

1. Make a careful description of each new instrument
with which you work.

INTRODUCTION. 13

2. Formulate each problem definitely.

3. Describe the means used in the solution of the problem.

4. Enumerate the facts observed through the help of the

means employed.

5. Seek for and note causes and inter relations or the facts

as far as possible.

6. Differentiate the essential from the incidental.

7. Formulate conclusions from the collected data.

3. Make generalizations as far as they are justifiable.

Agood note book should possess thefollowing qualities:

a. It should be complete, containing an account of every

problem studied.

b. It should be full, containing a sufficient amount to

guide another in performing the same experiments
and in verifying the facts and conclusions noted.

c. It should be logically arranged.

d. It should be as neat and artistic as the student can

make it in the time which he can devote to it.

PART I.

GENERAL PHYSIOLOGY OF CONTRACT.
ILE AND IRRITABLE TISSUES.

15

A. THE GENERAL PHYSIOLOGY OF CILIARY MOTION.

1. a. Normal ciliary motion, b. Ciliary motion modified

by the influence of narcotics and stimulants.

a. Normal ciliary motion.

/. Appliances. — Microscope, cell slide and cover glass;
normal saline solution (NaCl 0.6 %, Appendix
A, 1); physiological operating case (App. A, 3);
filter paper; frog or fresh water clam or mussel.

2. Preparation. — If a lamellibranch be used one need only

snip off, with the small scissors, a bit of the margin of a
gill and mount it in a drop of normal saline solution
on a cover slip, invert the cover over the cell of the
cell slide and focus under low power. If a frog be
used it will be necessary to pith it as a preliminary
step.
j. Operations. — To pith a frog.

(1). Grasp it with the left hand, holding the legs ex-
tended, one on either side of the little finger in such
a way as to bring the dorsum of the frog toward the
palm of the hand.
(2). With the thumb and index finger fix the frog's

nose and press it ventrally.

(3). Place the point of a narrow bladed scalpel in the
median-dorsal line over the space between the occi-
put and atlas, i. e., over the occipito-atlantal mem-
brane. This point is most readily located by using
the eyes as a landmark. The occipito-atlantal mem-
brane lies at the apex of an equilateral triangle whose
base has its extremities in the center of the cornece.
Having located the point for incision, press the
16

GENERAL PHYSIOLOGY. 17

knife through the skin, the intervening connective
tissue and the occipito-atlantal membrane, and^cut
the spinal cord transverely. Withdraw the knife.
(4) Insert the apex of a slender probe or of a blunt
needle into the incision, turning it sharply forward
so as to enter the cranial cavity. By sweeping the
distal end of the probe from side to side the con-
tents of the cranial cavity may be functionally de-
stroyed. When it is required simply to pith a frog
it is understood that the operation is complete as
described above. It may, however, frequently be
necessary to destroy the spinal cord as well as the
brain. To accomplish this insert the needle as de-
scribed under (4) ; but turn the point of the probe
so that it shall enter the neural canal of the verte-
brae. Pass it along this canal to a point nearly op-
posite the anterior end of the ilia. Withdraw the
probe.

A pithed frog can surfer no pain, but will respond
reflexly to certain stimuli. A pithed frog whose
spinal cord is destroyed cannot with the skeletal
muscles respond reflexly to any stimuli. Having
pithed the frog and destroyed its spinal cord, pin it
to a frog board with dorsum down, and legs ex-
tended.
To remove the (Esophagus of a frog.

(1) Place the head of the frog nearer to the operator.
With forceps lift the mandible and with the stronger
scissors sever the whole floor of the mouth trans-
versely and as far posteriorly as possible. Divide
the skin in the median line afi far posteriorly as the
pubes.

(2) Separate the two lateral halves of the sternum by
dividing the median sternal cartilage and carry the

18 LABORATORY GUIDE IN PHYSIOLOGY.

incision through the xiphoid appendix and abdomi-
nal walls. Withdraw the pins which fix the anterior
extremities; separate the lateral halves of the ster-
num by lateral traction upon the legs.

(3) With the forceps grasp a fold of the mucous
membrane which surrounds the puckered anterior
end of the oesophagus. While making gentle trac-
tion with the forceps, make, with the fine scissors,
a circular incision through the mucous membrane
surrounding the opening of the oesophagus.

(4) Grasp the pyloric end of the stomach; sever the
duodenum; lift the stomach up vertically above the
sternum; make moderate traction. The delicate and
elastic submucosa about the end of the oesophagus
will yield to the traction and the whole oesophagus
will be readily separated from the surrounding tis-
sues and w"holly removed from the frog.

(5) Open stomach and oesophagus by means of a
longitudinal incision through their walls; stretch
them upon a cork board, fixing with pins, and wash
off mucus with normal saline solution and camel's
hair brush. Remove the excess of liquid with the
help of filter paper.

4. Observations.

(1) Place a small piece of cork upon the anterior end
of the oesophagus. Does the cork move? li so, in
what direction and at what rate ?

(2) Will the cork pass over the boundary line between
oesophagus and stomach, and will it move over the
surface of the stomach?

(3) To determine the cause for the movement of the
cork, cut a minute portion of mucous membrane
from the crest of one of the folds, place it in a drop
of saline solution as directed under 2 {Preparation}

GENERAL PHYSIOLOGY. 19

and examine with a microscope. If the preparation
has been properly made the margin of the tissue
should, at certain points, show the cause for the
phenomena above observed. Study the character
of the ciliary movements. Describe.
(4) Study ciliary movement with higher power. It is
probable that the first preparation is not suited to
observation with a high power. If the cilia cannot
be readily brought into focus, prepare a second one
as follows: From the ciliated surface — clam-gill
or frog oesophagus — scrape a few epithelial cells,
with the point of a scalpel, place the minute bit of
tissue upon a cover glass; add a small drop of saline
solution; gently tease the tissue with needles, in-
vert the cover upon a slide, allowing one edge to
rest upon a hair, to avoid undue pressure upon the
tissue.

Focus under high power (300-600 diam.). If the
preparation is successful groups of ciliated cells
may be seen and the character of the ciliary move-
ment studied.

b. Ciliary motion modified by the influence of nar=
cotics and stimulants.

1. Appliances. — In addition to the appliances enumerated

above under a, one needs : A gas flask and siphon as
shown in Fig. 1. Also a cell slide with conducting
tube. (Fig. IB.) A gas generator will be necessary
unless there is a large generator for general use by
the class. HC1 25%, marble, chloroform, ether, ab-
solute alcohol, sealing wax, thread, small glass tube,
soft parafin.

2. Preparation. — To prepare a cell slide with conductor.

(1) From a hard rubber ring, having an inside dia-
meter of about 1 cm, and a thickness of about

LABORATORY GUIDE IN PHYSIOLOGY.

2 mm., cut a radial segment about 2 mm. wide.

(2) Clean the ring and slide with absolute alcohol.

(3) Fix the ring to the slide with sealing wax, placing
the opening in the ring toward one end of the slide.

(4) Heat the glass tube and draw it to one-half of its
orginal diameter as shown in Fig. 1. B.

(5) Fix the glass tube to the slide, using sealing wax.
The tube may be further supported by a few turns
of heavy linen thread drawn tightly, tied and fixed
in position with drops of melted wax.

(6) In order not to give too free vent from the cell for

FIG. 1. Apparatus for forcing a stream of gas or vapor through a cell.
For description, see I=b 2 and j>.

the gas which enters by the tube a bit of soft para-
fin may be warmed in the hand and worked, with
the point of a scalpel, into the space around the
end of the glass tube leaving only a little furrow in
the parafin above the tube.

3. Operation. — Fill the gas flask full of water and dis-
place it with CO2 gas. Fill the siphon and adjust
apparatus as shown in the figure. During any read-
justments of the apparatus the siphon may be kept

GRNEKAL PHYSIOLOGY. 21

filled and ready for action by putting on a screw-
clamp at s. Through varying the height ' of the
receptacle into which the siphon dips or through ad-
justment of the screw clamp or of the spring clamp at
d, the pressure and the rate of flow of gas are under
perfect control. Prepare a specimen of cilia for ob-
servation with a low power microscope. Bring a good
specimen into the field, focus the microscope and ob-
serve the rate and character of ciliary movement.
Remove screw clamp at s.
4. Observations. — a. The effect of CO2 upon ciliary activity.

(1) While observing closely the normal action of the
cilia, press the spring clamp gently for a few mo-
ments. If after a half minute or more no noticeable
change takes place in the rate of movement of the
cilia repeat the dose of gas.

What is the effect of CO2 gas upon the activity
of cilia ?

(2) After the effect of the gas has become apparent,
clamp the tube at//; disjoin at glass tube beyond and
gently draw air through the cell, thus ventilating it
and restoring practically the normal condition. Do
the cilia resume the normal movement ?

(3) How many times may the cilia be narcotized to
the point of complete cessation of activity and then
by ventilation be revived again ?

b. The effect of chloroform gas upon ciliary activity.

(4) Clamp tube at s ; remove flask from apparatus, fill
flask with water to expel CO2 ; empty ; drop into
the flask a pledget of cotton saturated with chloro-
form, replace flask as in Fig. 1. Make a new
preparation of cilia and observe normal movement.

Allow the chloroform gas to flow fcr a moment

22 LABORATORY GUIDE IN PHYSIOLOGY.

into the cell. Note the effect of chloroform upon

ciliary activity.
(5) How many times may the cilia be narcotized with

chloroform and revived again through ventilation ?
(^6) Repeat (4) with ether in place of chloroform.
(7) Repeat (5) with ether in place of chloroform.
c* Determine the action of alcohol vapor upon cilia.

If. To determine the amount of work done by cilia.

/. Appliances. — Physiological operating case ; frog board ;
cork board 10 cm. long by 5 wide; a centimeter rule;
a block of wood 4 or 5 cm. in height ; a bit of sheet
lead 1 mm. thick; scales correct to a milligram should
be accessible to the student.

2. Preparation. — Pith a frog and destroy cord. Dissect

out oesophagus and stomach as directed in lesson I.
Fix to cork board so that the long axis of the cesoph
agus shall be parallel with the long axis of the board.
Cut a piece of sheet lead just 5 mm. square and
another 3 mm. square. Weigh each of them.

3. Operation. — Wash off ciliated surface, remove the sur-

plus moisture with filter paper, and place the lead
gently upon the anterior end of the oesophagus.

The incline of the ciliated surface may be changed
by resting it, at different angles, against the block of
wood as shown in Fig. 2.

4. Observations.

(1) If the preparation is successful the piece of metal
will be slowly carried up the incline. Should it fail
a thinner piece of lead or a new preparation may
succeed. With a given incline, is the small piece of
lead carried more rapidly than the large piece?

(2) If W = work done, g = weight in milligrams and
li = height in millimeters, then W = g X h
would give the work in milligram-millimeters.

(3) Determine the distance through which the weight
is carried in a unit of time [one minute is a con-

23

LAB OR A TOR Y G VIDE IN PHYSIOLOGY.

venient unit of time to use], when the incline is
placed as shown in the figure.

(4) With the apparatus so adjusted what is the value
of h when the distance which the weight moves is 1
cm. ?

Does the thickness of the cork board need to be con-
sidered ?

(5) What is the work per minute, expressed in milli-
gramm-millimeters ?

FIG. 2.

FIG. 2. Appliances for changing the angle of inclination of the
ciliated tissue.

(6) What is the work done expressed in ergs?
[1 erg = 1 dyne X 1 centimeter; 1 dyne = 1 gramme
-*- 981]

(V) Using the same incline compare the result in
work done per minute with the two different weights?
Account for the results ?

(8) Using the weight which gave the larger values in
the foregoing experiments, find the degree of in-
cline which will yield the greatest amount of work ?

GENERAL PHYSIOLOGY. 25

(9) What significance has the variation of the thick-
ness of the lead weight? Determine the upper
limit of thickness?

(10) Would it be possible to determine the amount
of work accomplished by each cilium ? By each
stroke of a cilium ?

B. THE GENERAL PHYSIOLOGY OF MUSCLE AND
NERVE TISSUE.

HI. Demonstration : a, Elements and conductors; b, Keys;

c, The commutator; d, Work done; e, Elec=

trical units.

The function of muscle tissue is to contract. Skeletal
muscles contract only in response to stimuli. Stimuli may
act upon the muscle tissue — direct stimulation — or upon
the motor nerve which supplies the muscle — indirect stimu-
lation. To study the functions of muscle and nerve tissue
one requires to have at command various methods of stim-
ulation. It is usual to apply mechanical, thermal,
chemical and electrical stimulation. Experience has
shown that of all these means electricity is the most valu-
able, because it is subject to the greatest number of varia-
tions in strength and in method of application. Before
entering upon a study of the responses of irritable tissues
to electrical stimuli it is essential to make a short study
of the appliances used. As many of these appliances
have been used by the student in the physical laboratory
it will be taken for granted that he is familiar with the
principles involved in their use.

I. Appliances. — 2 Daniell elements or cells; wires; contact
key; Du Bois Reymond key; mercury key; commuta-

GENERAL PHYSIOLOGY. 27

tor; sulphuric acid, 10%; copper sulphate, saturated
solution; mercury.
2. Experiments and Observations.

a. The Daniell cell. — Present the four parts of the
cell. Half fill the outer receptable of the cell with the
saturated copper sulphate solution. Put the copper
plate into the cell; half fill the porous cup with the
dilute sulphuric acid, lower the zinc plate carefully
into the cup. The plate is of commercial zinc with
its various impurities.

(1) Observe the vigorous chemical action in porous
cup. Write the reaction. It is evident that the
zinc will be quickly consumed if allowed to re-
main in the acid and this will be the case whether
or not the cup and zinc plate be made a part of
an electric cell, and whether the cell be acting or
resting.

(2) The amalgamation of the zinc. [See also App.
A. -4.] Lift the zinc plate out of the acid, dip it
into the mercury. The mercury adheres to the
zinc, mingles with the surface layer of zinc, form-
ing an alloy, with a brush or an old cloth one
may rub the mercury over the whole surface of
the zinc plate — the zinc is amalgamated. The
impurities of the zinc do not enter into the alloy.
In this way only the Rure zinc which forms a part
of the alloy is presented to the acid. Chemically
pure zinc is acted upon very slowly by 10%
sulphuric acid; join a wire to the exposed end of
each plate. Touch the tongue with the freed end
of each wire separately; touch the tongue with
both wires simultaneously. Record results.

(3) Place the porous cup with the zinc plate in the
receptacle holding the CuSO4 with the copper

LABORATORY GUIDK IN PHYSIOLOGY.

plate. Touch the tongue with one wire, then with
the other. Touch the tongue with both at once.
Bring the two free ends of the wires into contact
with the binding posts of a detector; note results.
Touch the ends of the wires together, if the condi-
tions are favorable a minute spark may be seen
on touching and on separating the two poles. What
conclusions are to be drawn?

(4) Define element or cell as used in this connection .
Define plate, pole, electrode. The zinc is arbitra-
rily taken as the positive plate and the copper as
the negative plate. The pole which is attached
to the negative plate is the positive pole, and that
which is attached to the positive plate is the nega
tive pole. The positive pole or electrode of a gal-
vanic cell or of a battery is called the anode, while
the negative pole or electrode of a cell or of a bat-
tery is called the kathode.

b. Keys. — (1) Show and describe the simple contact
key (Fig. 7-k), the mercury key (Fig. 3), and the Du
Bois-Reymond key (Fig. 4).

(2) Two ways of using the D.u Bois Reymond key.
1st. As a simple contact key (PI. I Fig 1.)
2d. As a short circuiting key (PI. I Fig. 2.)

c. The commutator. — Most convenient for the physio-
logical laboratory is Pohl's commutator (Fig. 5).
This instrument may be used for the following pur-
poses:

(1) To change the direction of the current. Set
• up apparatus with cross bars in place as
shown in PL I Fig. 3. Which is the anode
when the bridge is turned toward a b? Which
is the anode when the bridge is turned toward
c d?

GENERAL PHYSIOLOGY.

(2) To change the course of the current. Set up
apparatus with cross bars removed, as shown
in PI. I Fig. 4. What course will the current
take when the bridge is turned toward a, b?
What course when the bridge is turned toward

c, d?

(3) Pohl's commutator may be used as a simple
mercury key (PI. I Fig. 5V Is the current open

FIG. 3.

FIG.
The mercury key.

FIG. 4.

FIG. 4. The DuBois-
Reymond key.

or closed when the commutator bridge is turned
toward a? How may the current be opened or
broken?

d. Work done by the cell. — The experiments performed
show that the galvanic cell may under proper con-
ditions, liberate energy. This energy is called elec
tricity. But the immediate source of the particular

80 LABOR A TOR Y G UID E IN PH YSIOL OGY.

electric energy liberated in the foregoing experi-
ments is the latent chemical energy represented in
the plates and liquids of the cell.

Under the conditions produced in the working
galvanic cell the latent chemical energy is trans-
formed, and at the same time liberated as electric
energy. This liberated electric energy may make
itself manifest in the contact spark, in moving the
detector needle or in lifting the armature of a mag-
net. In the last case mentioned it would not be
difficult to determine the amount of work done,
though it might be somewhat difficult to determine
the amount of work which a cell is capable of per-

FIG 5.
FIG. 5. Pohl's commutator. For description and uses see III=c.

forming in a given time. If one were to weigh the
copper plate before and after using the cell, one
would find that it had increased in weight. This
increase in weight is an index of the amount of
chemical action in the cell — of the latent chemical
energy which has been transformed into electric
energy. It must be, then, at least an approximate
index of the electric energy liberated. An exact
index of the amount of current is afforded by the
amount of electrolysis. For example, if the nega
tive pole of a cell be attached to a silver or platinum

GENERAL PHYSIOLOGY. 31

Cup containing pure nitrate of silver, and the posi-
tive pole be attached to a piece of pure silver which
is immersed in the silver nitrate solution, it will be
found that one ampere of current will uniformly de-
posit 0.001118 gm. of silver upon the cup in one
second of time. This brings us to the question of
the units of electrical measurements.
e. Electrical units. — The electrical energy available at
any point in a circuit, 2. e. , the current, as it is called,
is, according to Ohm's law, equal to the liberated
energy — the electromotive force — divided by the
total resistance of the circuit. This is expressed in
Ohm's formula, C = ^^ C = | It is im-
possible for the physicist to make any progress in
the study of electrical energy without arbitrarily
assuming units of measurement for current, for
electromotive force and for resistance.
^1) Current is measured in amperes. A current of
one ampere deposits upon the negative electrode
of a galvanic cell or battery 0.001118 gm. of silver
per second, or 4.025 gm. per hour. [See above.]
A concrete idea of the ampere may be gained
from the fact that the small sized Daniell cell
produces a current of about ^ ampere when the
external resistance is reduced to a minimum.
(3) Resistance is measured in ohms. An ohm is
that amount of resistance, opposed to the trans-
mission of electrical energy, by a column of mer-
cury 1 sq. mm. in cross section and 106.3 cm.
in length. For general purposes an ohm re-
sistance is that of a pure silver wire 1 mm.
in diameter and 1 meter in length.
(3) Electromotive force is measured in volts.

A volt is that amount of electrical energy which

LABORATORY GUIDE IN PHYSIOLOGY.

will produce 1 ampere of current after overcom-

ing 1 ohm of resistance.

" The ohm, the ampere and the volt are thus closely
related, and if any two of them be known with ref-
erence to any particular electric circuit or portion
of a circuit the value of the third may be readily
inferred."— [Daniell]. For if C=| then E = CxR
and R=]y Tne same relations maybe expressed thus:

1 ampere current = 1 ,;. or 1 ampere=!™

Therefore (1) Volts = AmperesxOhms.

(2) Amperes = Volts-5-Ohms,

(3) Ohms = Volts-5-Amperes.

The small Daniell cell has about 1 volt E. M. F.
and 4 ohms resistance, the current from such a cell
is then equal to approximately % ampere.

There are numerous other units of measurement
used by physicists and electricians, but for our pur-
pose it is not necessary to review these more
specialized points.

GENERAL PHYSIOLOGY.

33

{^rr^^^
^^^-^

s

7

PLATE I.

IV. Demonstration : Batteries.

A battery is a group of two or more elements or cells
arranged to produce increased or multiple effect. If one
wishes to use a stronger current than that afforded by one
cell, his first thought is to increase the number of cells, or
to procure a larger cell. Experimentation will show him
that it is not a matter of indifference which of these courses
to pursue. In the first place if he attempts to satisfy the
conditions he will find that to increase the size of the cell
increases the current only when the external resistance is
relatively small, and furthermore, there are practical limi-
tations to the size of a cell and these may be much within
the requirement which the cells must satisfy. It be-
comes apparent, then, that he who would use electrical
energy beyond the most limited field must resort to a bat-
tery composed of a number of cells. The problem which
first confronts him is, how shall these cells be arranged
/. Appliances. — 6 Daniel cells; wires; detector, (Fig. 6)
composed of simple magnetic needle mounted over
circle divided into degrees; rheostat or resistance box,
representing at least 100 ohms.
2. Experiments and Observations.

(1) (a.) Join up apparatus as shown in Pi. I., Fig. 6.
With the plugs all fixed in the rheostat, i. e.,
with no resistance except that of the wires and
battery, and the indicator needle at 0°, open
the key and then observe the angle at which
the needle comes to rest.

(b.) Remove from the rheostat the plug which will
throw into the circuit an extra resistance of 10

34

GENERAL PHYSIOLOGY. 35

ohms, Allow the needle to come to rest and
note angle ?

(V.) Remove from the rheostat plugs which will
represent in the aggregate 100 ohms of extra
resistance. Note angle of indicator as before.
(2) Join up two cells in multiple arc as shown in PL I.,
Fig, 7. That is, join both copper plates to one
copper wire and both zinc plates to another.
These wires are to be carried to key, rheostat and
detector as shown in PI. I., Fig. 6.
(#.) Note angle of needle with no extra resistance.
(£.) Note angle with 10 ohms extra resistance.
(V.) Note angle with 100 ohms extra resistance.

FIG. 6. .

FIG. 6. Detector, composed of simple magnetic needle mounted
over a graduated circle. The two heavy, copper wires which encircle
the compass offer slight resistance to the electric current.

(3) Join up four cells in multiple arc or " abreast'' and

repeat the observations of angle at the three re-
sistances as above.

(4) Join up six cells in multiple arc and repeat observa-

tions with 0/2, 10.Q, and 100/2 resistance.

(5) Join up two cells in series as shown in PI. I., Fig.

8. That is, join the copper of the first cell to the
zinc of the second. The first cell will have a zinc
uncoupled and the second will have a copper

36 LABORATORY GUIDE IN PHYSIOLOGY.

plate uncoupled. These two uncoupled terminal
plates of the battery are the ones from which to
lead off the wires to the other apparatus, which
should be arranged as shown in PI. I., Fig. 6.
Repeat the observations on the angle of deviation
of the needle, using the QO, 10.Q and 100.Q
resistance as above.

(6) Join up four cells tandem or in series, and repeat

the three observations.

(7) Join up six cells in series and repeat observations.

(8) Tabulate results and draw conclusions.

1. There is a marked difference in the results of the
two methods.

2. With low external or circuit resistance the current
as indicated by the angle at which the detector needle stood
increased with an increase in the number of cells joined in
multiple arc or abreast.

3. With high external resistance the strength of the
current does not seem to be essentially increased by in-
creasing the number of cells joined up abreast.

4. With low external resistance the strength of the
current is not increased by adding cells in series.

5. With high external resistance the strength of current
increases with an increase in the number of cells joined
up in series or tandem.

The following theoretical points are worthy of note :
The general formula C=g does not differentiate le
tween that part of the resistance furnished by the battery
and that part furnished by the external circuit. The
former is called internal resistance (ri) and the latter is
called external resistance (re). So we may write

GENERAL PHYSIOLOGY. 37

CASE I.

Suppose that the external resistance is so great in
comparison with the internal resistance that the latter may
be made equal to zero (ri = 0) C/=-^jt- = ~~ for one cell.

Suppose that we arrange a battery of sixteen cells in
multiple arc. Experiment has shown that when a battery
is so arranged the internal resistance of the battery de-
creases in proportion to the number of cells and that join-
ing up cells in multiple arc is equivalent to simply increas-
ing the size of the plates.

Our formula then becomes :

C' = H^- : but_£L=0;C' = _E_; C=C'.
^+re' 16

Therefore no advantage is gained by joining up cells
in multiple arc when the external resistance is incompara-
bly greater than the internal resistance.

CASE II.

Let the internal resistance be incomparably greater
than the external.

Then for one cell: C =-r?-; but re = 0, therefore C = -?-

-- n

Join up 16 cells in multiple arc. The internal resist-
ance is thus decreased by the factor 16.

C'= TJ^— ; re = 0; therefore C'=JL = ^0=160.

l6+re IT

Therefore when the internal resistance is incomparably
greater than the external resistance the current increases
proportional with the number of cells joined in multiple
arc.

CASE III.

Let the internal resistance be so small relatively as to
be discarded. For one cell C =

38 LABORATORY GUIDE IN PHYSIOLOGY.

Join up 16 cells in series. Experiment has shown
that when cells are joined in series the internal resistance
increases in proportion to the number of cells, for the
current must pass through all of the cells ; further, the
electromotive force is reinforced as it passes through each
cell so that it also increases in proportion to the number of
cells. Our formula then would be :

C' = ifai+re > but ri = 0' therefore, C'=^; C=16C.

Therefore the current will increase in proportion to the
number of cells joined in series, when the external resist-
ance is incomparably greater than the internal resistance.

CASE IV.

Let the internal resistance be incomparably greater
than the external and join 16 cells in series, then :

C'~ is^i+re > but re = °; therefore C'= ~~ = ~.
In this case, however, Cr=^; therefore there is no ad-
vantage gained by increasing the number of cells in series
when the external resistance is very small.

CASE V.

Practically, however, one deals with cases where
neither the external nor the internal resistance is so
small as to be ignored. Let us suppose that we have a
battery of a cells, that the internal resistance of each cell
is r and that the total external resistance is R. It
has been shown experimentally that the current is great-
est when the external resistance is equal to the internal
resistance; i. e., when -^j- = R; s being the number of
cells in series and m the number in multiple arc.

GENERAL PHYSIOLOGY. 30

We have, then, two equations.

(!) TT = R-

(2) s m = a

Find s and m.

(«>••-*•

(5) -£-== ^iorar, = m °R.

(6) m = VITJ or, in a similar way,

Let us take a concrete case, using our 16 cells, each of
which has an internal resistance of 4 ohms, how shall we
arrange them to get the best results with 16 ohms external

resistance.

/ a r /16X4 0

m = V-r = --

s = =

We shall therefore arrange the battery in a series of 8
pairs, each pair being joined abreast.

How must they be arranged when there are 64 ohms or
more of external resistance?

How must they be arranged when there are only 4
ohms of external resistance?

What arrangement would you adopt if there is only 1
ohm external resistance?

V. Demonstration: Methods of varying the strength

of current, a. The rheostat, b. The

Du Bois=Reymond rheocord.

It has already been shown that the strength of current
may be varied by increasing the number of cells or by
changing their arrangement in the battery. This method
is indispensable, but it has its limitations. If one has a
small cell and wishes to decrease the current, he must
have recourse to another method. From the formula C =
-|- it is evident that one may decrease the current by in-
creasing the resistance.
a. The rheostat.
/. Appliances. — Resistance box or rheostat; 1 cell; 5 wires;

detector.
2. Experiments and Observations.

(I) Set up the apparatus as shown in PL I., Fig. 6.

(1) With plugs all fixed in rheostat, needle of detec-
tor at 0°, close key and note angle of deviation.

(2) Remove the plug which will throw into the circuit
the lowest resistance contained in the rheostat.
Note the angle.

(3) Add to the above resistance the smallest possible
increment and note angle.

(4) Proceed in this way tabulating results.

(5) Conclusions.

(II) Another method of using the rheostat. The rhe-
ostat may be used in short circuit as shown in PI. I., Fig.
9. From this arrangement of the apparatus it is appar-
ent that when all of the plugs are in place the current
will be short circuited by the rheostat. If the resist-
ance of that part of the circuit leading to the detector
— the long circuit — be considerable the long circuit

40

GENERAL PHYSIOLOGY. 41

current will probably not be sufficient to cause any
deviation of the detector needle; for the current varies
inversely as the resistance (C x -jjr), and if the re-
sistance of the long circuit (R) be incomparably
greater than the resistance of the short circuit (R')>
then the current of the long circuit (C) will be incom-
parably less than the current of the short circuit (C'),
i. e., C : C' :: -± '- -~} or C : C' :: R' : R; therefore if
R' = 0, C must equal 0.

Suppose that the resistance of the detector circuit
be only 10 ohms, and suppose we remove from the
rheostat plug that represents 0.1 ohm resistance, then
one-hundredth of the current will pass through the
detector. If we make the resistance in the short cir-
cuit 0.2 ohms then one-fiftieth of the current will flow
through the long circuit.

In this way we may increase the detector current
step by step until the maximum is reached. What
is the maximum current to be derived when the
resistance in the long circuit equals 10 ohms, the maxi-
mum resistance of the rheostat 100 ohms, external re-
sistance in circuit between cell and rheostat 1 ohm,
E. M. F. = 1 volt, internal resistance of cell four
ohms ?
b. The Du Bois=Reymond Rheocord.

In the use of the rheostat the variation of the cur-
rent is step by step and not gradual. Experience has
shown that tor certain physiological experiments it is
necssary to cause a gradual variation of the current,
i. e., an increase by infinitessimal increments. The
Du Bois-Reymond rheocord is an instrument which
fulfills this condition by adding to the short circuit
millimeter by millimeter the resistance of a platinum
wire. The principle and use of the Du Bois-Reymond

42 LAB OR A TOR Y G UWE IN PHYSIOLOG Y.

rheocord is the same as that of the rheostat with the
exception that one ohm resistance is furnished by two
platinum wires which are stretched along the top
of the long resistance box. A mercury bridge
makes electric connection between these wires. When
the bridge or " slider " stands at 0 the conditions are
the same as one has in the use of the rheostat with all
of the plugs in. As the bridge is moved gradually
from 0 to 100, one ohm of resistance is as gradually
thrown into the short circuit. At that point a plug
representing one ohm resistance may be removed and
the bridge brought back to 0, and another ohm of re
sistance gradually introduced into the short circuit.
In this way any desired amount of resistance may be
introduced by infinitely small steps — by infmitessimal
increments — and the current of the long circuit will
be increased correspondingly.

/. Appliances. — 1 cell; Du B-R. Rheocord; detector; 5
wires; key.

2. Experiments and observations.

(1) Set up apparatus as shown in PI. II, Fig. 1.
With bridge at 0, close key and note angle.

(2) Leaving the key closed gradually slide the bridge
to 1, then slowly and with an even rate of motion
on to 100, noting the behavior of the detector needle.

(3) Open the key, remove the plug which represents
1 ohm, and slide the bridge back to the zero position,
close the key and note the angle at which the needle
comes to rest. If the resistance of the platinum
wires is 1 ohrn then the needle will come to rest at
the same point noted above when the bridge stood
at 100.

(4) From this point the needle may be caused, by
sliding the bridge from 0 to 100, to gradually in-
increase its angle.

VI. Demonstration: To vary the current through

the use of (a.) the simple rheocord, or (b.)

the Ludwig compensator.

Besides the methods already used for varying the
strength of the current one may use the derived current.

The simple rheocord (Fig. 7) may be used for this
purpose.

a. The simple rheocord.

/. Appliances,— One or more cells; simple rheocord; 5 wires;
detector.

FIG. 7.
FIG. 7. The simple rheocord. See also PI. II, Fig. 2.

2. Experiments and observations.

(1) set up the apparatus as shown in Fig. 2, Plate II.
From the figure we see that from the cell to post
A, thence through the German silver wire to postB
and back to the cell makes a complete circuit. Hav-
ing reached the metallic slider (S) the circuit has
two paths presented. 1st, from S direct to B; 2d,

43

44 LABORATORY GUIDE IN PHYSIOLOGY.

from S through D and back to B. The total cur-
rent is divided into two parts, C which passes
along the wire from S to B, and C' the derived cur-
rent which passes through the detector. Sup-
pose the resistance to the last named current is R'
and that to the direct current is R, the relative
strength of these two currents is expressed in the
following proportion: C' : C : : R : R'.

But the resistance of the German silver wire may
be conveniently divided into 100 equal parts (100 r).

If the slider be placed at any position along the
wire, say at x centimeters from the end, then the
formula would be C' : C : : lOOr— xr : R'.
r, Cr (100 -x)

~R '
Suppose that R = 1 ohm (r = 0.01 ohm); R' =

2 ohms and x = 0; i. e., suppose the slider to be
hard up to A, then C' = Cr(^00~x) = -f- ; or the
current which passes to the detector is one-half as
strong as the current through the rheocord.

(2) What is the relative strength of the two currents
when x = 10?

(3) What is the relative strength of the two currents
when x = 50?

(4) What is the relation of C' to C when x = 99?

(5) What is the relation of C' to C when x = 100?
From this course of reasoning it is evident that

in the simple rheocord we have an instrument with
which we can vary a derived current from zero to a
maximum. Just what the value of this derived cur-
rsnt will be will depend upon the voltage of the cell
or battery and the total resistance to be overcome,
as well as upon the distribution of that resistance.

(6) Verify the theory just developed, making out a
table of detector readings.

GENERAL PHYSIOLOGY.

45

PLATE II

LABORATORY GUIDE IN PHYSIOLOGY.

b. The Ludwig compensator.

This instrument, though used in a. class of experi-
ments quite different from those in which the rheocord
is used, involves the same principle as that involved
in the simple rheocord, and is used to make minute
variation in the strength of a current. The general
construction of the instrument is shown in Fig. 8.

A

FIG. 8. The Ludwig
compensator, originally
devised by Ludwig to
compensate a muscle
current, may be used
in the same way as the
simple rheocord. Its
maximum current is,
however, limited. For
description, see VI=b.

FIG. 8.

The outer receptacle is of copper and serves as the
copper plate; within is a porous cup containing the
zinc plate. This is practically a Daniell cell. A
graduated upright of brass makes metallic contact
with the copper plate, and at A the circuit is com-
pleted by a platinum wire to B.

GENERAL PHYSIOLOGY. 47

A slider makes contact with the platinum wire, but
slides along the standard by an ebonite arm. The
derived current passing along the wires A and B, and
the direct current from S to B along the platinum wire
sustain a relation similar to that of currents C and C'
in the rheocord.

/. Appliances. — Ludwig compensator; 2 wires; detector.

2. Theory, experiments and observation.

(1) Join the two poles, a and b, to the detector; place
the slider at 0 cm., or hard up to the zinc plate, and
note the deviation of the needle.

(2) Gradually move the slider from 0 cm. to 50 cm.
(or 100) noting the effect upon the needle.

(3) Suppose the detector circuit, from S through the
detector and back to B, has a resistance of 10 ohms
(R' — 10). Let the resistance of the platinum wire
be 0.01 ohm per centimeter; for the instrument
figured, R = 0.5 ohm. Let C' be the detector
current, and C the direct current. Then C' : C : :
-JL : -jL., or C' : C : : R : R', or C' = ^ Let x be
the distance in centimeters from B to S, or the read-
ing of the position, of the slider; then the proportion
of R at any position of the slider would be .

C'= ~j; substituting the assumed values, C'=-^-.

(4) When x = 0 how much current will flow through
the detector?

(5) When the slider stands at 10 cm. what proportion
of the total current will flow through the detector ?

(6) When the slider stands at 25 cm., how much
larger is C than C'?

(7) When the value of x is 50 the ratio of the detector
current to the direct current?

(8) Verify all of these theoretical results as far as
possible, by experiment.

VII. Demonstration: To send an electric current into
a nerve gradually. FleischPs rheonom.

When one studies the effects of thermal, mechanical or
chemical stimuli, he may apply the mechanical stimulus so
slowly that the nerve may be severed without calling forth
a response; he may apply heat to the fresh nerve so grad-
ually that the nerve may be actually cooked without caus-
ing a contraction of the muscle which it supplies.

The problem which we have next to solve is to apply
an electrical stimulus gradually.

/. Appliances. — Fleischl's Rheonom; 1 Daniell cell; Du
Bois-Reymond's "Muscle Telegraph;" contact key;
detector; saturated solution of zinc sulphate; 5 wires;
frog; operating case.

The rheonom is constructed as shown in PI. II.
Fig. 3 — R. Its essential features are: g, the non-
conducting base with circular groove; s, the non-
conducting rotatable, central standard; P, the battery
binding postF, having zinc connection with the groove;
p, the rotating, binding posts, having zinc limbs con-
necting with the groove.

2. Experiments and Observations. — Set up apparatus as
shown in PL II. Fig. 3, after amalgamating the zinc
tips which dip into the zinc sulphate. Fill the groove
with zinc sulphate.

(1) Find and mark the zero position for the rotating
limbs of the rheonom; i. e., find the position which
will give no deviation of the detector needle when
the contact key is closed.

48

GENERAL PHYSIOLOGY. 49

(2) Find and mark the position which the rotating
limbs occupy when the detector needle indicates 10°.

(3) Find and mark in succession each higher incre
ment of 10° until the maximum is reached.

(4) Rotate the limbs so gradually as to cause the de-
tector needle to rotate with slow and regular motion
from the zero position to the maximum position and
back.

(5) Make a gastrocnemius muscle nerve preparation;
mount it in the muscle telegraph; change the wires
from the detector to the electrodes of the muscle
telegraph; place the limbs of the rheonom in the
maximum position, close the key. With the closing
of the key the maximum current is instantly thrown
into the nerve and serves as a strong stimulus in
response to which the muscle contracts.

(6) Place the limbs of the rheonom in the minimum
position. Close the key. Inasmuch as the muscie
nerve preparation is much more sensitive to elec-
tricity than is the low resistance detector the muscle
will probably respond when the conditio-ns are as
above indicated. Theoretically a zero point exists.
Practically it is difficult to find it for a muscle-
nerve preparation. The finding of a position where
there is no response on closing the key is however not
essential in this experiment.

(7) Keeping the key closed, slowly rotate the limbs
of the rheonom from the minimum position to the
maximum position. If the conditions are favorable
this can be done without calling forth a response.

(8) Without opening the key, slowly rotate the limbs
backward from the maximum to the minimum posi-
tion. One may thus send through a nerve a strong
current and may withdraw the same without caus-

30 LAB OR A TOR Y G VIDE IN PH YSIOL OGY.

ing a contraction of the muscle. Keep the key
closed.

(9) Quickly rotate the limbs from minimum to maxi
mum; the muscle responds. Quickly rotate from
maximum to minimum; the muscle responds.

From the preceding observations one may con-
clude that response to electrical stimulation is elic-
ited not by the simple flow of an electric current
through the irritable tissues, but by a more or less
sudden change in the strength of the current. The
opening and closing of a galvanic current, also its
sudden increase or decrease, serves as an efficient
stimulus, while the gradual increase or decrease in the
strength of the current causes no response.

of(

> .••""'»/,

3

VIII. Demonstration : To determine the influence of
the kathode and anode poles.

Many of the phenomena of muscle-nerve physiology
were inexplicable until a difference was noted (Von Bezold
1860), in the influence of the anode and kathode. This
difference in the influence of the two poles may be best
observed by use of the sartorius muscle of a frog.

1. Appliances. — A double myograph and support; record-

ing drum; Daniell cell; Pohl commutator; Du Bois-
Reymond Key; nonpolarizable electrodes; 5 wires;
electrode clamp and support.

2. Preparation.

(a) Nonpolarizable electrodes. — The Du Bois-Reymond
nonpolarizable [N P] electrode is made as follows:
(Fig. 9). T. Glass tube of about 4 mm. lumen. Z.
Zinc rod with a binding screw (B). The zinc
rod must be amalgamated before use in an electrode.
R. Rubber tube clasping both glass tube and zinc
rod. S. Saturated solution of sulphate of zinc, in-
troduced with a narrow pointed pipette. C. Kaolin
plug, made by working china clay powder into a stiff
paste with normal salt solution.

The electrodes should be filled at each time of using,
and the parts may be "assembled " in the order and man-
ner enumerated in the description.

(b~] The Fleischl brush electrode differs from the fore-
going in substituting the brush of a camel's hair
pencil for the kaolin plug. This variation of the
N P electrode is somewhat more difficult to pre-
pare, but is more convenient for certain uses.
61

52 LABORATORY GUIDE IN PHYSIOLOGY.

(r) If one has not the zinc rods at hand he may readily
prepare an efficient N-P electrode as follows: 1st.
Take 5 cm. of No. 16 copper wire, make one end
perfectly clean and bright. 2d. Dip the bright end
into molten c. p. zinc. The zinc adheres to the
wire, and if the dipping be repeated two or three
times the lower 1 centimeter of wire will have a

FIG. 9.

FIG. 9. Nonparizable electrodes, hand electrode.

The Du Bois-Reymond N-P electrodes, shown in the two middle
cuts, are described in the text V11I-2 (a), (c).

The Fleischl brush electrode, mentioned in the text [2 (b)], may be
prepared by setting the brush in stiff k?olin paste, or if a more perma-
nent electrode is desired, in plaster of Paris.

A plaster of Paris pencil, as shown in the lower left hand cut, may
be used for ordinary work with the constant current.

The hand electrode shown at the right, is used with an induced
current.

thick coating of zinc. 3d. Take a glass tube 10 cm.
long, and with a 4 mm. lumen, draw it in the

GENERAL PHYSIOLOGY. 53

middle to about two-thirds its original diameter,
cut it into two such as shown in the figure. Before
assembling the parts, that part of the copper wire
not covered by zinc, excepting the tip (t) must
be painted with brunswick black or any varnish, and
the zinc must be amalgamated. With this electrode,
as with the preceding, zinc sulphate, kaolin and
NaCl 0.6 per cent are used. The part C in these
electrodes may be held in a clamp.
d. A double myograph.

A most efficient, as well as convenient and economical
double myograph may be arranged for this experiment as
indicated in Fig. 10.

It will be noticed that two common muscle levers such
as are shown in Fig. 13, are used, that these are held in
position by common clamps and heavy support, that the
upper myograph is reversed and its lever counterpoised
by the weight (w), that between the two myographs a small
wooden block — with a longitudinal hole for the loop of
thread which holds the muscle — is held by a clamp,
j. The experiment.

(1) Curarize a frog. (See Appendix A-5.)

(2) After the lapse of three hours or more, the sartorius
muscle may be prepared as described in Lesson X.

(3) Mount the preparation by passing a loop of coarse
thread through the hole in the block (b), lift the
muscle by its tendon of insertion, pass it through the
loop, draw the loop gently around the middle of the
muscle and fix by making a single knot around the
screw (s) of the clamp. The fine hooks which join
the muscle to the levers may now be passed through
the tendons, and the proper position of the levers
effected by an adjustment of the clamps. The non-
polarizable electrodes may be clamped between two

54

LABORATORY GUIDE IN PHYSIOLOGY.

pieces of cork and held by an extra support. A
"universal" clamp holder is a most desirable acces-
sory to this apparatus.
The electrical apparatus should be set up as shown in

PL II., Fig. 4.

With this arrangement either electrode e or electrode
e' may be made the anode, the experimenter needing only
to reverse the commutator bridge to reverse the position
of anode and kathode.

FIG. 10.

FIG. 10. Double myograph. Described in the text
under VIII=3.

The recording drum or kymograph should rotate
rapidly. The recording points of the myograph levers
should be adjusted so that the point of the upper one
touches the drum vertically over the point of the lower
one. Adjust the time marker so that it will indicate the
time of making and breaking the circuit, i. e., so that it

GENERAL PHYSIOLOGY. 55

will record on the drum the time of making stimulus and
the time of breaking stimulus. The recording point of
the time marker should, of course, be in the same vertical
line with the myograph points. The moist tips of the
N-P electrodes should be so adjusted as to just touch the
muscle above and below the loops of thread.

(1) Close the key. If the preparation has been sue
cessful, the half of the muscle in contact with the
kathode pole will respond before the other one.

(2) Break the current. The anode should respond first.

(3) Reverse direction of current and repeat (1) and (2).

(4) Vary the strength of current through use of simple
rheocord and determine whether the results are the
same for currents of different strength.

Law I. The make-contraction starts at the kathode and the
break-contraction starts at the anode, or
When irritable tissue, muscle, or nerve, is subjected to a
galvanic current the response to the stimulation begins in
the region of the kathode on making the current and in
the region of the anode on breaking the current.

Would the foregoing observations justify the following
statements: (1) Kathcdic contractions, or make contrac-
tions, may be caused by a galvanic current which is too
weak to cause anodic contractions or break contraction.
(2) Kathodic or make contractions are stronger than
anodic or break contractions.

IX. a. The muscle = nerve preparation, b. Indirect
mechanical, thermal and chemical stimu-
lation of the gastrocnemius.

a. The muscle=nerve preparation.

/ Appliances. — Frog board and pins ; operating case ;
glass nerve-hooks, like Fig. 11, A, made as follows: Take
a 10 cm. piece of glass rod, heat and draw in center to
about \l/2 mm. diameter; cool, cut in two, heat the
points to smooth them and bend the end over to form
the hook.

FIG. 11.

FIG. 11. A. Glass nerve-hook; for description see IX=a=/. B. Gastro-
cnemius muscle-nerve preparation. For description, see text IX=a=j>.

Simple myograph or muscle lever (See Fig. 13).
Watch glass with salt crystals. 20 cm. of thick coppei
wire.

2. Preparation. — Pith a frog and fix to frog board, with
dorsum up.

It will be taken for granted that the student is familiar
with the anatomy of the frog's leg and thigh. The ac-

56

GENERAL PHYSIOLOGY. 57

companying cuts may serve to refresh the memory.

(Fig 12)
j. Operation. — To make a gastrocnemius "muscle nerve prep

aration."

(1) Make, with scissors, a circular cutaneous incision
around the tarsus, corresponding with the lower end
of cut B. Make a longitudinal cutaneous incision,
beginning at the margin of the circular incision where
it crosses the external aspect of the tarsus, carry it
along the tibia, along the course of the biceps femo
ris muscle, over the pyriformis to the posterior end

FIG. 12.
FIG. 12. Showing the muscles of the frog's thigh and leg.

of the urostyle, along the whole extent of the uros-
-tyle. From the posterior end of the urostyle make
an incision posteriorly and ventrally, for 1 or 2 cm.
Grasp the free margin of the skin at the point of
the circular incision and with a quick traction
toward the head of the frog the skin will be re-
moved from the whole field of operation.
(2) Pass a point of the fine scissors under the glisten-
ing tendon of the biceps femoris where it is inserted

58 LABOR A TOR Y G UIDE JN PHYS1OLOG Y.

into the tibia, taking care not to injure any of the
neighboring tissues. Sever the tendon. Grasp its
free end, lift the biceps up, carefully cutting the
delicate connective tissue which joins it to neigh-
boring structures; sever its heads. The removal of
the biceps and a separation of the cleft which the
biceps occupied reveals three blood vessels and the
large trunk of the sciatic nerve. Which of the blood
vessels is the sciatic artery? Which the sciatic
vein? Which the femoral vein?

Grasp and lift up the posterior end of the urostyle,
sever the ilio-coccygeal muscles, remove the urostyle.

The sciatic plexuses formed by the 7th, 8th and
9th pairs of spinal nerves will be revealed.

(4) Pass a glass nerve hook under the sciatic nerve,
gently lift it up, severing, with the scissors, the con-
nective tissue. The pyriformis muscle must also
be divided. The whole length of the sciatic nerve
may thus be readily dissected out. Care should be
taken not to stretch, pinch or cut the nerve during
this process. Lay the nerve upon the gastrocne-
mius muscle.

(5) Grasp the triceps femoris muscle, pass a blade of
the scissors under its tendon; sever, and remove
the whole mass of muscles anterior to the femur.
In a similar manner remove the muscles posterior
to the femur.

(6) Grasp the tendo achillis, sever low down at X;
lift up the gastrocnemius, sever the tibia and its
associated muscles as near to the knee joint as
possible.

(7) Sever the femur at the juncture of its middle and
upper thirds. The finished preparation has the
characteristics shown in Fig. 11 — B. A segment of
the vertebral column may or may not be left on.

GENERAL PHYSIOLOGY. 59

The indirect stimulation of the gastrocnemius.

Observations. — To mount the muscle- nerve preparation in
the myograph. Fix the femur in the clamp (Fig. 13-c);
place a piece of filter paper, wet with normal saline solu-
tion, upon the glass nerve support (s); lay the nerve upon
the support; make a longitudinal slit in the tendo
achillis, pass the hook of the muscle lever through the
slit and so adjust the height of the clamp as to bring the
lever into a horizontal position.

FIG. 13.

FIG. 13.

Simple myograph, with a femur-clamp (c), and a glass
plate (s) for a nerve rest.

a. Mechanical Stimulation.— (1) Snip off with scissors the
central end of the sciatic nerve. If the muscle in-
stantly contracts, thereby lifting the lever, the ob-
server will know that his preparation is successful.
If it does not respond to the first stimulation it may
to a second or subsequent one. If it responds to

60 LAB OR A TOR Y G VIDE IN PH YSIOLOG Y.

later stimuli but not to the first ones, one may con-
clude that in making the preparation a portion of
the central end of the nerve was killed.
(2) What may one conclude if the muscle responds
to stimuli applied to the central end of the sciatic
nerve, but later fails to respond to stimuli applied
farther along the course of the nerve, i. e., nearer the
muscle?

b. Thermal Stimulation.

(3) Make and mount a fresh preparation. Heat the
copper wire in a gas flame and touch the end of the
nerve with the hot wire. If the preparation has
been successful the muscle will respond by a contrac-
tion. If the preparation is a good one save at least
^i of the nerve for the subsequent experiment.

c. Chemical Stimulation.

(4) Cut off the part of the nerve which is dead and
lay the central end of the still functional nerve in a
saturated solution of common salt. Await resultst
Record all results.

X. Variation in the method of applying mechanical,
thermal and chemical stimuli.

/. Appliances. — Operating case; kymograph; myograph;
3 frogs.

2. Preparation. — Much interest will be added to these
experiments if a permanent record be made of the move-
ments of the lever when the muscle responds to a stim-
ulus. The most practical method of recording these
movements is to cause the lever point to trace them upon
a moving surface. It is customary to use a rotating cyl-
inder, upon which is fixed a glazed paper which may be
smoked in a gas flame. The kymograph — wave writer—
an instrument much used for this purpose, consists of a
metallic cylinder and a clock work for its propulsion,
(See Fig. 14.)

Describe the structure of the kymograph giving fig-
ures.

To prepare the kymograph for work. (See Appendix
A-6.)

To curarize a frog. (See Appendix A-5.)

j. Operation. — To make a sartor ius preparation. After the
frog has come under the influence of the curare, pass a
blade of the fine scissors under the tendon of insertion
of the sartorius; cut it as close to the tibia as possible;
grasp the tendon with forceps and carefully lift it up,
cutting, with the scissors, the connective tissue which
holds the muscle in place; follow it as far as possible and
get as much of the tendon of origin as possible. Mount
this preparation by tying a thread to each terminal tendon,
and fixing one thread to the myograph clamp and the

61

62 LABOR A TOR Y G VIDE IN PHYSIOLOG Y.

other to the tracing lever. This muscle should not be
made to lift as heavy a weight as is used for the gastroc
nemius.
4. u&sgrvations.

(#) Direct versus indirect stimulation.

(1) Put saturated salt solution upon the sartorius — di-
rect stimulation. If it responds take a tracing of the
response.

FIG. 14.
FIG. 14. The Kymograph. For description see Appendix C.

(2) Mount the second sartorius and try mechanical
and thermal stimuli, tracing and recording results.

(3) Prepare and mount a gastrocnemius preparation,
from a frog that was not curarized. Apply various
stimuli to the nerve — indirect stimulation — as in the
previous lesson and record results.

GENERAL PHYSIOLOGY. 63

(b) Qualitative variation of stimuli. — Make and mount a
gastrocnemius preparation for indirect stimulation.

(5) Study the response to the following variations of
mechanical stimuli : cutting, pinching, tapping,
pricking.

(6) Study the responses to the following variation of
thermal stimuli : ice, hot wire.

(7) How does the muscle respond to indirect stimula-
tion with glycerine, alcohol ?

(V) Quantitative variation of stimuli. Use gastroc-
nemius preparation.

(8) Mechanical stimuli : light tapping, heavy tapping.

(9) Thermal stimuli : Touch the nerve with the wire
which has been held in boiling water, i.e., 100° C.

Touch the nerve with a wire which has been
heated to redness in a gas flame.

(10) Chemical stimuli : Put the end of the nerve into
0.6 % solution of common salt. Follow this with y^
saturated solution of common salt. Compare the
results with those obtained when a saturated solu-
tion was used.

((T) Variation in the length of time of applying stimulus.
Use gastrocnemius preparation.

(11) Cut off, or pinch off the nerve very slowly. This
may be done so slowly and with such a gradual in-
crease of pressure as to cause no contraction of the
muscle.

(12) Put the central end of the sciatic into tepid
0.6 % NaCl solution, and . gradually bring to a
boil, protecting the muscle and that part of nerve
not in the solution, with absorbent cotton moistened
in normal saline solution.

The nerve may be functionally destroyed without
causing a contraction of the muscle.

64 LAB OR A TORY G UIDE IN PH YSIOL OGY,

(13) Put the central end of the nerve into NaCl 0.6 %
and gradually add salt to saturation. Take another
preparation, put the nerve into a few drops of
NaCl 0.6 %. Add alcohol drop by drop until the
mixture is about 90 °/0 alcohol. Record results.

XI. Electricity as a stimulus. The galvanic current.

/. Appliances. — Operating case; 3, 10 cm. pieces of uncov-
ered copper wire; a piece of zinc; beaker; a Daniell
cell; kymograph; myograph; simple contact key; 4 cov-
ered battery wires; 2 frogs.

2. Preparation.

(1) Curarize a frog.

(2) To prepare a " water element ," take a small bright
piece of zinc, wind one end of a 10 cm. piece of cop-
per wire around it, remove the glass plate from the
middle clamp of the myograph, clamp two copper
wires so that one or two centimeters of wire will ex-
tend out horizontally on one side of the clamp, while
the other longer ends extend out on the other side;
one of these is wound around the piece of zinc. Bend
these long ends down to the perpendicular. Do not
allow these wires to touch each other in any part of
their course.

(3) Charge the Daniell cell (See Appendix A-4), insur-
ing the proper amalgamation of the zinc. Do not put
the zinc into the cup until the cell is to be used.

j. Experiments and Observations.

(1) Take two coins of different metals, preferring cop-
per and silver. With a knife or file brighten on the
circumference of each two small surfaces removed
from each other by \ to \ the circumference. Touch
each coin separately to the tongue. Now bring the
two coins into close contact at bright points, leaving
the other two fresh surfaces in such a position that
the tongue may touch both at the same time. Touch

65

66 LABOR A TOR Y G VIDE IN PH YSIOLOG Y.

the coins with the tongue as indicated. Is there any
difference in the sensation which the tongue receives
in these two experiments ? Record results, account-
ing for phenomena.

(2) While in the operation of making a gastrocnemius
preparation, after the sciatic nerve has been freed from
the other structures in the thigh, slip the glass nerve-
hook under it so that the handle of the nerve hook
will hold the nerve away from the other tissues. Press
the end of a copper wire against the muscles of the
thigh, touch the silver probe to the sciatic nerve, then
to the copper wire, first separately, then simultane-
ously.

Vary the experiment by using other combinations:
Silver and steel, copper and steel, etc. Note briefly the
original observations of Galvini. Are the observations
just made different in any essential respect from the
observation which led to the discovery of what we call
galvanic electricity?

(3) Complete the gastrocnemius preparation, mount the
muscle in the myograph, place the nerve across the
horizontal ends of the two wires, lift the beaker of
water and immerse the two pendant plates — the cop
per wire and the piece of zinc.

If the experiment is successful the muscle responds
vigorously. Is there any chemical action in this water
element? If so, describe it. Would oxidized or tar-
nished plates answer as well as bright ones?

(4) Mount another gastrocnemius preparation, adjust
the Daniell cell for action, set up the electric apparatus
as shown in Plate II, Fig. 5, clamp the two exposed
poles (p.) in the middle clamp so that the ends are
exposed for about two centimeters. Place the nerve
across the poles. Adjust the kymograph for tracing
a myogram.

GENERAL PHYSIOLOGY. 67

(0) Close the key, i. e. "make" the current, and hold
the key down for several seconds. Note results
and take tracing.

(£.) Open the key, i. e. "Break the current."
Note results and take tracing.

(V.) Make and break the current during one rotation
of the drum. If there is a response on both make
and break, so time the closing and opening of the
key that these will come in pairs with a consider-
able pause between. Before fixing the tracing,
(see Appendix A-7. ) mark each wave which was
the effect of making the current m., and each wave
which was caused by breaking the current, b.

(5) Prepare and mount a sartorius from the curarized
frog. Bring the two poles into contact with the
muscle, and repeat the experiments suggested under

(*•)

(6) In experiments (4) and (5) the observer has applied
electric stimulation of medium strength both directly
and indirectly to the sartorius and gastrocnemius
muscles. He is justified in formulating certain con-
clusions— subject to subsequent modification.

Formulate conclusions.

(7) Describe minutely the chemical and physical proc
esses going on in the active Daniell cell.

XII. Stimulation with the constant current. The
simple rheocord.

/. Appliances. — Operating case, kymograph and myograph;
3 or 4 Daniell cells; simple rheocord; materials for mak
ing nonpolarizable electrodes, (see demonstration
VIII); Pohl's commutator with cross-bars; Du Bois
Reymond key; 9 wires; 3 frogs.

2. Preparation.

(1.) Make a pair of N P electrodes.

(2.) Set up apparatus as shown in PI. II, Fig. 6.

j. Operation. — Make and mount a gastrocnemius prepc'.
ration and so adjust the nerve to the electrodes that the:
current will be a "descending" one, i. e. so that the
kathode will be nearer to the muscle than is the anode

4.. Observations.

(1) (a) Open the short-circuiting Du Bois-Reymond
key — i. e. make the long circuit.

(b) Close the key, thus breaking the long circuit, or
muscle-circuit.

(c) Take a tracing of a series of alternating make and
break shocks with descending current.

(d) Take a tracing with ascending current. How may
one change the direction of the current along the
nerve without changing the adjustment of nerve
and electrodes?

(2) (a) Give the preparation a stronger stimulus by
joining two cells. Should one join the cells in series
or multiple arc ? Why ?

(b) Take a tracing as before using the descending
current.

GENERAL PHYSIOLOGY.

69

(c) Vary the experiment by the use of the ascending
current.

(3) (a) Increase further the strength of the stimulus by
the use of a battery of three or four cells.

Record effect of descending current,
(b) Record effect of ascending current.

(4) Set up electrical apparatus with simple rheocord as
shown in PI. II. Fig. 7. Instead of making a tracing
tabulate the results.

(a) Adjust for stimulation with the minimum descend-
ing current. Make the muscle circuit and record
whether the muscle contracted, or remained at rest.

(b) Stimulate with minimum ascending current and
record.

(c) Gradually strengthen the current, recording at
each position of the slider the results for both de-
scending and ascending currents, make and break.

The following form of table should be used:

STRENGTH
OF
CURRENT.

DESCEl

Make.

VDING.

Break.

ASCENDING.

Make. Break.

Weak.

Medium.
Strong

Contract.

Rest.

1

(5) Sum up the day's work in a series of conclusions.

XIII. The effect of the induced current.

/. Appliances. — Operating case; inductorium with Neei
hammer; contact key; DuBois Reymond key; 7 wires;
1 Daniell cell; materials for making hand electrodes [2
No. 24 or 28 wires ^ meter long, 2 pieces of capillary
rubber tubing 4 or 5 cm. long, thread]; 2 frogs.
2. Preparation. — (a) To make hand electrodes for use with
induced currents. Push a thin wire through a piece of
capillary rubber tubing (capillary glass tubing may be
used instead of the rubber), bring two such side by side
and wrap thread around them. If glass tubing be used
the wire will need to be fixed in the tubes with a drop of
sealing wax.

Such a pair of hand electrodes are shown in Figure 9>
page 52.

(£) Set up electric apparatus with contact key in
primary circuit and short-circuiting key in secondary
circuit.

j. Operation. — Make and mount gastrocnemius prepara-
tion.
4. Observations.

(1) Take tracings of the contractions produced by a
series of " make, induction shocks " applied indirectly.
The " make, induction shock" is obtained as follows:
(a) With primary circuit not interrupted by the
Neef hammer, but closed and opened only by the
contact key; open the short-circuiting key of the in-
duced circuit.

(£) Close the contact key of the primary circuit, a
make induction shock — i. e., a shock in the in-
70

GENERAL PHYSIOLOGY. 71

duced circuit caused by a closure of the battery-
circuit — will stimulate the preparation.

(/) Close the short-circuiting key in the secondary
circuit.

(d) Open or break the primary circuit. An induced
break shock occurs in the secondary circuit but it
is short-circuited by the closed Du Bois Reymond
key. If while the drum rotates one makes, in
close succession, the changes above indicated —
a-b-c-d-a-b-c-d etc. — there will be produced a
series of contractions, all the result of stimulation
by make induction shocks.

(2) Take a tracing of the contractions resulting from
a series of indirectly applied break induction shocks.

(3) By leaving the short-circuiting key open, one may
get a series of contractions due to alternating make
and break induction shocks. Let these be re-
corded in pairs upon the kymograph.

(4) Determine the distance which the secondary coil
may be removed from the primary coil and get any
response to the make or break. Which is more
effective make or break ? Can one find a position
of the secondary coil where there are only make or
break shocks? What are the limits of this position ?
Within the limits of that position where both make
and break contractions occur are there differences
in the height of the make or break waves? Is there
a position of maximum height for both waves ? If
not, is there a position of maximum height for each
wave ?

Make a tracing on a slowly rotating drum, while
gradually moving the secondary coil from the great-
est distance which gives a contraction up to the
zero point. Record at intervals upon the tracing

72 LABOR A TOR Y G VIDE IN PHYSIOL OGY.

the positions of the secondary coil at that point in
the tracing.

(5) Still leaving the short-circuiting key open make
and break the primary current as rapidly as it is pos-
sible to close and open the key in the primary circuit.
Take tracing.

(6) So adjust the apparatus that the Neef hammer is
brought into the primary circuit, thereby making
and breaking that circuit with each vibration of the
hammer. Mount a fresh gastrocnemius, adjust the
kymograph for slow or medium rotation.

Close the short circuiting key; close the key in
the primary circuit. The Neef hammer should start
to vibrating and continue to do so as long as the
primary circuit is closed. Start the kymograph.
After an abscissa a few centimeters in length has
been traced upon the drum, open the short-cir-
cuiting key. If the experiment is successful the
muscle will be tetanized. Allow the tetanizing cur-
rent to operate until a tetanus tracing several centi-
meters in length has been traced. Close the short-
circuiting key.

After a few moments the muscle may be again
tetanized, and repeatedly so until exhausted.

XIV. The work done by a muscle, a. To determine the

amount of work done by a single contraction.

b. To determine the total amount of work

done by a muscle, c. Reaction

changes in fatigued muscle.

/. Appliances. — Same as in lesson XIII.; also 50-gramme
weight and 20 or 30 gramme weight.

2. Preparation. — Arrange electrical apparatus for a series,
of break induction shocks.

f. Operation, — Make and mount a gastrocnemius prepara-
tion for indirect stimulation.

4.. Observations. — Upon a slow drum record in close order a
series of break contractions.

a. To determine the amount of work done by a single

contraction.

(1) What weight is lifted?

(2) How high is it raised?

(3) What is the ratio between the height of the curve
traced by the lever and the height through which
the weight was raised?

(4) Let W = work done.

g = weight lifted.

h = height of curve traced by lever.

K— constant of the apparatus, in this case

the ratio between the lever arms. Then

W=A,'. g. h.

(5) Express the amount o^f work in ergs.

b. To determine total work done.

(5) How many times was the weight lifted before the
muscle was fatigued?
73

74 LAB OR A TOR Y G UJDE IN PH YSIOLOG Y.

(6) Through what average height was the weight
lifted ?

(7) Has the value of k or g changed?

(8) Give a formula for total height (H = ).

(9) Give a formula for total work done (W=).

(10) Express in ergs, the total work done by the muscle.

(11) In the fatigue tracing did the lever continue
throughout the observation to fall back to the orig-
inalabscissa ? If not, describe any general changes
in the abscissa.

c. Reaction changes.

(12) Apply a piece of neutral litmus paper toj the
fresh muscle tissue of the frog from which your
specimen was taken. Record result.

(13) Apply a piece of litmus paper to a fresh cut sur-
face of the fatigued muscle. Record results.

(14) What is the reaction of the muscle of a frog
alter rigor mortis has been established?

(15) What is *he reaction of fresh urine?

XV. Demonstration: Electrotonus; to determine the effect
of a constant current upon the irritability of a nerve.

At the beginning of this century Ritter discovered that
the vital properties of irritable and contractile tissues
were modified when subjected to a constant battery cur-
rent. This modified condition was called galvanismus.
During the first half of this century the subject was in-
vestigated by Nobili, Mattencci, Valentin and Du Bois-
Reymond ; the last named substituted the word electro-
tonus for galvanismus and further modified the terminology.
It remained for Pfluger (Untersuchungen iiber die Physio-
logie des Electrotonus, Berlin, 1859) to rework the whole
field, to correct, to elaborate, and finally to formulate laws.
a. Preliminary experiment.

1. Appliances. — Muscle-signal; 2 Du Bois-Reymond keys;
2 Daniell cells ; commutator ; 8 wires ; salt.

2. Preparation. — Set up electrical apparatus as shown in
PI. II. Fig. 8.

j. Operation. — Make and mount in the muscle signal a

gastrocnemius preparation.
4.. Observations.

(1) In which position must the bridge of the commuta-
tor stand to give a descending current? Mark that
side of the commutator D. Mark the opposite side A.

(2) With a descending current, which pole is the
kathode, a or b?

(3) PI. II. Fig. 8-p represents the glass plate of the
muscle signal. So arrange the triangular platinum
electrodes that there shall be a distance of about 1
cm. between the electrodes, and both electrodes near

75

76 LABORATORY GUIDE IN PHYSIOLOGY.

that end of the plate farthest from the muscle. Lay
the nerve over the electrodes and along the glass
plate. The segment of nerve which lies upon the
glass plate between the electrodes and the muscle
may be subjected to various stimuli, mechanical and
chemical. Sterling (Prac. Phys., p. 244) uses salt.
At a point about 1 cm. from the electrodes, marked x
in the figure, place upon the nerve trunk as many fine
crystals of common salt as would be taken up on the
point of a penknife. Moisten these salt crystals with
a drop of water. While the salt solution is per-
meating the sheath of the nerve trunk, adjust the com-
mutator for a descending current. When the muscle
begins to twitch, note the effect upon the signal. The
contractions become more and more tetanic in
character.

(4) Close the commutator circuit, open the short-cir-
cuiting key, i. e., make the "polarizing" current. If
the experiment is successful the tetanus is more
marked. Which pole is nearer the point stimulated?

(5) Close the short circuiting key, i. e., break the
"polarizing" current. Reverse the commutator;
make the current. The muscle is put completely or
almost completely at rest. Which pole is nearer the
stimulus?

(6) Repeat (4) and (5) several times. It is evident
that the irritability of the nerve to the salt stimulus is
increased in the region of the kathode, and decreased
in the region of the anode pole. This changed con-
dition of the nerve due to the passage of a constant
current is called electrotonus. The state of increased
irritability in the region of the kathode is called
katelectrotonus. The decreased irritability in the region
ol the anode is called anelec trot onus.

GENERAL PHYSIOLOGY. 77

b. Myograpkic record of anelectrotonus and of katelectrotonus.

1. Appliances. — 3 or 4 Daniell cells; 3 Du Bois-
Reymond keys; contact key; 2 commutators; induc-
tcrium; 2 N-P electrodes; 18 wires; kymograph;
myograph with moist chamber; 2 pairs of platinum
wire electrodes to use with induction currrent.

2. Preparation. — Arrange apparatus according to plan
shown in PI. II., Fig. 9. Note that the cross bars
are absent from the commutator in the induction cir-
cuit. This enables one to stimulate the nerve at the
central end (c) or at the segment between the polar-
izing electrodes and the muscle (m), by simply revers-
ing the bridge of the commutator (B).

j. Operation. — Make and mount a gastrocnemius prepa
ration in moist chamber myograph; adjust drum for
tracing myogram. Adjust electrodes as shown in
diagram.

Test apparatus and preparation by sending single
make (or break) induction shocks through nerve at c
or at m. Let there be a typical response at both
places. The secondary coil should be removed to a
distance that gives a little more than the minimum
stimulus required to cause a contraction of the muscle.

To close the constant current "polarizes" the nerve
or, better, induces electrotonus.

That segment of the nerve between the anode and
kathode is called the intra-polar region.

Those segments centrally and distally located are
called extra- polar.

The induced current is called the stimulating cur
rent.
4. Observations .

(1) Adjust for descending, polarizing current. Stimulate
at c, i. e. in the region of anode. Note — trace — ex-

78 LAB OR A TOR Y G VIDE IN PH YS1OL O G V.

tent of muscle contraction. Induce electrotonus,
stimulate again in region of anode. If the experiment
is successful the contraction will be found to be de-
creased or absent.

The nerve is, at the point c, in a condition or anelec-
trotonus [descending extra polar anelectrotonus].

(2) Stimulate at m, or in the region of the kathode.
Withdraw polarizing current. After a few minutes
stimulate again at m. If the experiment is successful
the wave is higher in the former than in the latter
case.

The stimulation was made in the region of the
kathode and the nerve in a condition of kathelectrotonus.
[Descending extrapolar kathelectrotonus.]

(3) Adjust for ascending, polarizing current.
Stimulate at m, i. e., in the region of the anode. The

contraction is weaker than in the normal nerve, or it
may be quite absent. This region is now in a condi-
tion of anelectrotonus. [Ascending extrapolar anelec
trotonus.]

(4) Stimulate in the region of the kathode. The re-
sponse is probably weak. Withdraw the polarizing
current. Stimulate again in the region of the kathode.
The response is normal, i. e., it is greater than during
theelectrotonic condition.

But in descending extrapolar kathelectrotonus the re-
sponse was greater than normal. In the experiment
just performed we stimulated in the region of ascend-
ing extrapjlar kathelectrotonus. Note that the polariz-
ing current is relatively strong.

(5) Remove one cell from the battery and repeat (4.)
If the response to stimulation is still weaker with than
without the polarizing current, reduce the strength of
the polarizing current still farther by use of the simple

GENERAL PHYSIOLOGY. 79

rheocord. Finally with a weak polarizing current, the
stimulus in the region of ascending extrapolar kathe-
lectrotonus causes a stronger response than normal.

The response which the muscle makes must be
accepted as a measure of the excitation which
it receives from the nerve. But the excitation
delivered by the nerve depends upon two factors, its
irritability and its conductivity. When the nerve is
stimulated in the region of ascending extra or intra-
polar kathelectrotonus, its increased irritability is of
no avail if there is interposed between that region
and the muscle a region of decreased conductivity.
With strong polarizing currents the region of the
anode is not only decreased in irritability but also in
conductivity.
Laws of electrotonus.

I. The passage of a constant current through a nerve in-
duces a condition of electrotonus marked by an increased
irritability in the region of the kathode (kathelectrotonus^)
and a decreased irritability in the region of the anode
(anelec trot onus} .

II. During electrotonus induced by a strong current the con-
ductivity is decreased in the region of the anode. Further
— though not derived from the foregoing experiment — "at
the instant that the polarizing current is withdrawn the
conducting power is suddenly restored in the region of
the anode and greatly lessened or lost in the region of
the kathode."" — Lombard, in American text-book of
Physiology.

XVI. Demonstration : Pfltiger's law of contraction.

/. Appliances. — Du Bois-Reymond rheocord, or simple
rheocord; 3 Daniel cells; muscle signal or myograph
with moist chamber; 2 Du Bois-Reymond keys; com-
mutator; 2 N. P. electrodes.

2. Preparation. — Set up the apparatus with three cells in
series, Du B.-R. key as closing key. Commutator with
cross-bars, Du B. R. rheocord in short circuit, short-cir
cuiting key, the two N P. electrodes clamped in cham
ber of myograph.

_? Operation. — Make and mount a gastrocnemius prepara-
tion.

4. Observations.

(1) Stimulate with make and break of the weakest pos-
sible descending current.

Record results in such a table as that suggested in
laboratory lesson XII.

This table shows what response (contraction or
rest) the muscle gives on the making and breaking of
the descending current and on the making and break-
ing of the ascending current.

It also shows in a marginal column the gradual in-
crease of the strength of the current through gradual
increase of resistance in the short-circuiting rheocord.

(2) Make and break with weak ascending current. If
the conditions are typical the muscle will contract on
making both ascending and descending current.

(3) Increase gradually the strength of the electrode cir-
cuit, recording results. After a longer or shorter
transitional period in which the result will be varied

80

GENERAL PHYSIOLOGY.

81

by a contraction on both the make and break of the
ascending current, one comes to a strength of current
which causes a contraction on both make and break
of both descending and ascending current. This is
the medium strength for the preparation and the con-
dition in question.

(4) Let the current be increased still further and by
larger increments. After passing another transitional
stage one finally reaches a strength of current which
causes a contraction on make of descending current
and break of ascending current. This is the strong
current for the preparation under observation.

It not infrequently happens that through overstim-
ulation and fatigue of muscle the whole experiment
cannot be completed upon one preparation except by
increasing the current by larger increments.

(5) Pfliiger's law of contraction may be expressed in the
following table:

STRENGTH
OF
CURRENT.

DESCENDING.

ASCENDING.

Make.

Break.

Make.

Break.

Weak.

c

R

C

R

Medium.

C

C

C

C

Strong.

C

R

R

C

(6) But how shall we account for these results?

Let us recall some of the laws which have been dem-
onstrated.

Law I. The influence of make and break stimulation.
The make contraction starts at the kathode and the break
contraction starts at the anode. Further, kathodic or make
contractions may be caused by a current which is too weak to
cause anodic or break contractions.

82 LABORATORY GUIDE IN PHYSIOLOGY.

Law II. A law of Electrotonus.

The passage of a constant current through a nerve induces a
condition of electrotonus, marked by an increased irritability
in the region of the kathode, and a decreased irritability in
the region of the anode.

Law III. A law of Electrotonus.

During electrotonus induced by a strong current the con-
ductivity is decreased in the region of the anode.

With the- help of these laws account for all the typical
phenomena observed above.

PART II.

SPECIAL PHYSIOLOGY,

C. CIRCULATION.

XVII. The circulation and its ultimate cause, a. To

observe the capillary circulation, b. To observe

the action of the frog's heart.

a. To observe the capillary circulation.

1. Appliances. — Cork board 3 cm. wide by 20 cm. long and
about y?, cm. thick; cover glasses, 18 mm. in diameter
and 10 mm. in diameter; normal salt solution; camel's
hair brush ; pins ; compound microscope; sealing wax ;
thread ; filter paper ; 2 per cent croton oil in olive oil.

2. Preparation.

Pith two frogs the day before the observation is to be
made. At the beginning of the laboratory period when
the observation is to be made curarize the frog lightly by
the hypodermic injection of one drop of a 1 per cent
solution of curare. Make a frog-board by cutting a hole
1.5 cm. in diameter near one corner of the cork board
and fasten a large cover glass over the hole with sealing
wax.

j. Operation. — After the frog becomes curarized, pin it out
ventral surface downward in such a way as to bring one
of the hind feet over the hole in the board. Tie thread,
not too tightly, to the third and fourth digits, loop the
threads over pins and gently separate the digits until the
web is quite flat and closely approximated to the surface

85

LABOR A TOR Y G UJDE JN PH YSIOLOG Y.

of the fixed glass which covers the hole. Run a film of
normal salt solution under the web; place a drop of the
same liquid upon the upper surface of the web ; place a
small cover glass over it ; fix the board upon the micro-
scope stage so as to admit of illumination by transmit-
ted light; illuminate; focus under low power.
?. Observations.

(1) Observe the movement of corpuscles within blood
vessels of varying size and irregular course. Make a
drawing of the field of observation showing the rela-
tive size, the course and anastomoses of the blood
vessels.

(2) Observe whether the motion is equally rapid in all
vessels ; if not, observe whether the slower currents
are in the larger or the smaller channels. Determine
which of the vessels are arterioles, which capillaries,
and which venules.

(3) Have you seen evidence of intermittent force acting
upon the corpuscles? If so, desciibe its influence.
Determine whether this intermittent force makes
itself evident in all of the vessels ; if not, in which
class of vessels is it present?

(4) Do the corpuscles change shape? If so, under
what circumstances?

(5) Remove the cover glass, dry the web with filter
paper, touch a point with a pin that has been dipped
into dilute croton oil. Without replacing the cover
above the web observe whether the presence of the
croton oil effects any change in the diameter of the
vessels, or in the rate of the blood flow. If there is a
change in both, has one a causative relation to the
other ?

(6) Note and describe minutely all changes which take
place at and near jthe place touched with the croton

CIRCULA TION. 87

oil. If no marked change is produced by the croton
oil, touch the point with a needle which has been
dipped into strong nitric acid.

(7) Observe with a high power. Have you noted di-
apedesis of white or of red corpuscles. If so, describe
the process minutely.

b. To observe the action of the frog's heart.

/. Appliances. — Dissecting board; fine scissors; heavy
scissors; pins; forceps; watch glass; camel's hair brush;
normal salt solution; fine silk thread; ice, in a beaker.

2. Preparation. — Pith a frog, lay it with its dorsal surface
upon the dissecting boaid; stretch out its legs and pin
the feet to the board.

j. Operation — Make a median incision through the skin
from the pelvis to the mandible; make transverse inci-
sions and pin out the flaps. Raise the tip of the epi-
sternum; insert a blade of the fine scissors under it and
divide it transversely, about ^ cm. anterior to the tip.
Raise the anterior segment of the sternum at the point
of the transverse incision; insert the blade of the strong
scissors under it and divide it longitudinally in the
median line. Withdraw from the board the pins which
fix the anterior extremities, make gentle, lateral traction
upon the fore feet until the split sternum is sufficiently
separated to afford a convenient working distance and
to plainly expose the whole heart.

4? Observations.

(1) Note rate of systole.

(2) Note sequence of contraction of auricles, ventricle
and bulbus.

(3) Note change in shape of different parts.

(4) Note change in color and the position of the same
in the heart-cycle.

88 LABOR A TOR Y G UIDE IN PHYSIOLOG Y.

(5) Carefully excise the heart including the sinus veno-
sus and the bases of the posterior and two anterior
venae cavae, also the bases of the two aortic trunks.
Place the excised heart in a watch glass. Obseive
whether the pulsation continues. If so, what is your
conclusion regarding the relation of the heart move-
ments to the central nervous system?

(6) If the pulsation continues, note whether the rate
of pulsation has been noticeably changed by the ex-
cision.

(7) Bathe the heart with a few drops of normal solution.
Hold the watch glass in the palm of the hand and note
whether the rate changes.

(8) Float the watch glass upon ice water and note the
results.

(9) If the heart seems vigorous (otherwise procure a
fresh one), carefully sever the sinus venosus with the
fine scissors. Does the sinus continue to beat ? Does
the heart continue to beat ? Interpretation.

(10) If the heart beats, sever the auricle from the ven-
tricle through the auriculo-ventricular groove. Note
results.

(11) If the auricles beat, divide them. If they con-
tinue to beat, do they follow the same rhythm?

(12) If the ventricle becomes quiescent, stimulate it
either mechanically or with a single induction shock.
How does it respond to a single stimulus? Continue
to subdivide the heart until the parts refuse to respond
to stimuli.

(13) Repeat the experiment and see if the same results
are reached on subsequent trials. Note results and
give your interpretation.

XVIII. The graphic record of the frog's heart=beat.

/. Appliances. — Frog board; a straw or strip of bamboo 20
cm. long; a cork about 2 cm. in diameter and height;
pins; needles; sealing wax; parchment paper; a kymo-
graph, stand and lamp; a chronograph. (See Appendix
A- 15.)

2. Preparation. — Use a pithed or a curarized frog. Make a
heart lever after the model shown by the demonstrator.

3. Operation. — Open the abdomen of the frog as described
under XVII-b 3 and expose the heart. Open the peri-
cardium, place some resistant object — a cover slip for
instance — under the ventricle. So adjust the heart
lever that the cork foot of the long arm of the lever will
rest upon the juncture of the auricles and ventricle. If
the weight of the lever seems to be too great for the heart to
move easily, the long arm may be made relatively lighter
by placing a counterpoise upon the short arm. If the
tracing point of the long arm has a sufficient excursion
to make a good tracing, bring the kymograph to a posi-
tion where the point will lightly touch the carboned
surface of the drum. The lever should be nearly tan-
gent to the surface of the drum, and so arranged that
the rotating surface of the drum turns away from the
tracing point of the lever rather than toward it.

4. Observations.

(1) Note whether the curve is a simple one or com-
posed of a major wave, with crests superimposed
upon it.

(2) In either case closely observe the phases of the
heart-cycle and determine the relation of each part

90 LA BORA TOR Y GUIDE IN PHYSIOLOG Y.

of the cycle with each part of the tracing. If the
tracing has a single crest, more delicately counterpoise
the lever and more carefully adjust the narrow foot of
the lever to the auriculo-ventricular groove and repeat
the experiment.

(3) Take tracings of the auricle alone. Compare these
with those of the auriculo-ventricular groove and deter-
mine the causes of the variation.

(4) Without altering the counterpoise take a tracing of
the ventricle and compare it with the two preceding
curves and account for all the differences.

(5) Try to take a double tracing with one lever foot
resting upon the auricle and the foot of the second
lever resting upon the ventricle. The tracing points
must touch the drum in a vertical line. Are the
crests synchronous? If not, why?

(6) If a time tracing be added by means of the chrono
graph one may determine the time relations of the
different phases of the heart cycle.

XIX. The apex-beat. The heart-sounds.

/. Appliances. — A cardiograph and a transmitting tambour
(Marey) or materials for constructing them. A stetho-
scope; a stand and support; clamps; a kymograph; two
tambour pans Nos. 1 and 2; thin sheets of rubber; thread;
corks; sealing wax; tambour holder; straws; needles;
parchment paper; chronograph.

2. Preparation. — With the materials furnished by the dem-
onstrator construct a cardiograph and a recording tam-
bour, [Appendix A., Nos. 8-9.]. Join the tube of the
cardiograph to the tube of the recording tambour with
a rather thick-walled rubber tube 50 centimeters in
length. Fix the recording tambour with clamp and
support, and bring it into adjustment for tracing the
cardiogram upon the kymograph. Adjust chronograph,
j. Operation. — Let a student remove the clothing from the
region of the apex beat of the heart and take, upon the
table, a recumbent dorso-sinistral position. In some
cases, however, better results are obtained if the sub-
ject sits beside the table. Place the button of the
receiving tambour upon that point of the thorax most
affected by the apex beat of the heart. The move-
ments of the chest wall will be faithfully transmitted
and magnified by the two tambours.
4.. Observations.

(1) Note the exact point upon the chest where the apex-
beat is most distinctly marked. Is it the same for
different members of the class?

In recording the location of the apex- beat use the
bony landmarks of the chest rather than the nipple.

! LA BORA TOR Y G UWE IN PH YS1OL OGY.

In what intercostal space is it located ? How far to
the left of the median line of the sternum?

(2) Take several cardiograms from the same individual,
being careful so to adjust the apparatus as to gain the
maximum excursion of the lever. What features have
all of these tracings in common ? What features seem
to be accidental and nonessential? What are the causes
of the essential features? What are the sources of the
nonessential features?

(3) Take cardiograms of several individuals. Do all of
them possess the features *which seemed essential in
the first series, taken from one individual ? If not, how
would you account for the difference?

(4) With a stethoscope, whose construction you have
carefully described in your notes, listen to the heart-
sounds while the cardiograph is tracing the record of
the heart-movements. Note that two sounds are audi-
bh: and that there is a noticeable pause following the
shorter, sharper sound; let us call the sound which
succeeds the pause the first sound.

(5) With what part of the cardiogram does the first
sound seem to correspond? With what part of the
cardiogram does the second sound seem to correspond?
Give reasons for this correspondence.

(6) As far as the data will admit, enumerate causes for
the first sound; for the second sound; for the essen-
tial features of the cardiogram.

XX. The flow of liquids through tubes. Lateral
pressure.

1. Appliances. — Reservoir with short discharge nozzle
whose lumen is 6 mm. in diameter; 5 pieces of glass
tubing whose lumen is about 6 mm. in diameter and
whose length is 60 cm.; two lengths of glass tubing
whose lumen is about 3 mm. in diameter and whose
length is 60 cm ; rubber tubing for joining up the ap-
paratus; 3 T tubes of 6 mm. tubing; short tube with
capillary point from each size of tubing; 2 one liter
flasks; 2 supports; a light pine stick about 6 feet long;
compressors (Mohr's).

2, Preparation. — A resourceful demonstrator will have no
difficulty iu contriving reservoirs. It is sometimes not
easy to provide a large class with suitable and conven-

ient reservoirs. The following form

has proven very satisfactory: A glass
tube about 3 cm. in diameter may be
readily furnished with a glass nozzle of
the required size by any glass blower.
The nozzle should be about 3 cm. from
one end of the tube. That end may
be closed with plaster of Paris and
filled with hard paraffin to the lower
margin of the nozzle opening. This
reservoir may be held upright by a
4cm support. When complete it presents
the appearance indicated in the accom-
Fig. 15 panying figure.

04 cm

36 C/n

is cm

94 L AB OR A 7 'OR Y G UIDE IN PH YS/OLOGY.

3. Operation. — Mark upon the side of the reservoir a point
36 cm. above the center of the nozzle, also a point 64
cm. above the nozzle. While the reservoir is filled from
one flask the water may be caught in the other. As-
sume some convenient unit of time, as 10 or 15 seconds.
4.. Observations. — (a) Fill the reservoir to the height of 64

cm.

Allow the water to flow from the nozzle freely into the
flasks. Observe the force with which the jet issues
from the nozzle when the water begins to flow. Note
the difference when the water in the reservoir reaches
the 36 cm. mark; the 16 cm. mark. What are your
conclusions?

(<£) Velocity. — How does the velocity of the discharge
vary with the varying height of the column of water ?
Why does it so vary? Does it verify the law of
Torricelli? The rate at which a fluid is discharged
through an orifice [better a nozzle] in a reservoir is
equal to the velocity which would be acquired by a body
falling freely through a height equal to the distance be-
tween the orifice and the surface of the fluid.

Recall the law of falling bodies. How far will a
body fall in vacuo,\}\e first, second and third seconds
respectively? What is the constant acceleration
per second, due to gravitation ? What is the
velocity at the end of the first, second and third
seconds respectively? What is the total distance
traversed at the end of the first, second and third
seconds respectively? Let g equal the constant
acceleration (approximately 32 ft. or 981 cm). Let
h equal the total distance in centimeters, v the
velocity and t the time in seconds. Derive from
the facts the following equations:
(1) v = gt.

CO h = g

CIRCULATION. 95

From these equations derive:

(3) v=^/2gh; (approximately^ 4.3^h).
Expressed as a variation the constant may be dis-
carded and the variable would read :

(4) vooVh, or V : v :: VH : ^h.

Verify the truth of this mathematically derived law.

(V) Discharge. — The discharge of liquid flowing
through an orifice must equal the product of the
area of the orifice and the velocity with which the
liquid flows. Let D equal the quantity of liquid
discharged from the nozzle in a unit of time, and r
equal the radius of the lumen of the discharging
tube or orifice. Derive the formulae:

(5) D = 4 4.37rrVh.

(6) D xrVh.

Where one has to deal with two variables he may
make one of them constant and verify for the other.
When r is constant:

(7) D xVh, or D : d :: VH : ^h.
When the height is constant:

(8) D xr3, or D : d :: R2 : r2

Verify by experiment formula (7) as follows:

During a unit of time allow the water to flow from the

6 mm. nozzle, meantime maintaining a fixed level —

e. g., at 64 cm. — by pouring water into the reservoir

from a flask. Note the amount of discharge (D).

Make the observation also for the 36 cm. height.

Verify formula (8) by determining D when the

height is kept constant (64 cm.) and the radius of

the discharge tube alone is varied. Use, for example.

a 3 mm. nozzle. But there is another variable not

considered above, namely, the resistance.

(^/) The relation of discharge to resistance. — Attach to

the nozzle one length of 6 mm. tubing. Note the

LABORATORY GUIDE IN PHYSIOLOGY.

discharge in the unit of time. Attach a second
length of the 6 mm. tubing, taking care that the
tubing is approximately horizontal. Note the dis-
charge in a unit of time. What is your conclusion?
Why does the discharge decrease when the length
is increased?

If R equals resistance and L length of tubing,
does the following expression represent the facts:

(9) R ooL ?

Is the relation of discharge to resistance direct or
reciprocal ?

Verify the following formula:

(10) Dx-L.

We have already found the formula I) ooryh.
Verify the formula:

(11) Doo^

) Pressure. — Disjoin all tubes from the reservoir.
Join a T-tube to the nozzle in this position 1; join
a segment of large glass tubing to the perpendic-
ular arm of the T-tube and support it in an upright
position.

(1) Fill the reservoir to the 36 cm. mark, allow
the water to escape from the distal end of the
T-tube during a unit of time, meantime main-
taining the height of the water in the reservoir.
Carefully note the height at which the water
stands in the upright tube — the piezometer.

(2) Repeat with water maintained at 64 cm.
height in the reservoir.

(3) Join a length of large tubing to the distal
end of the T-tube; repeat the experiment using
only the 64 cm. height.

(4) Join a T-tube with piezometer No. 2, to the
distal end of the segment of tubing just added

CIRCULA TION. 97

and repeat the experiment. (Note: The
piezometers may be held in position by using
the two supports and the pine stick.) Does
the addition of the last T tube make any essen-
tial change in the height at which the water
stands in piezometer No. 1? Does the reading
of piezometer No. 2 agree with the reading of
piezometer No. 1 in experiment (2).

(5) Add a second segment of large tubing. Re-
peat the experiment. Does reading of pie-
zometer No. 2 correspond with reading of pie-
zometer No. 1 in experiment (3)?

(6) Add piezometer Np. 3. Repeat the experi-.
ment. Does reading of piezometer No. 3 cor-
respond with that of No. 2 in experiment (4)
and with No. 1 in experiment (2)? Does read-
ing of piezometer No. 2 correspond with that
of No. 1 in experiment (4).

(7) Attach a large capillary, repeat observations.

(8) Attach a fine capillary and repeat observa-
tions. What is the relation of pressure to
height of column? Does pressure vary as
height or as the square root of height?

(9) (a) What is the relation of pressure to the
central resistance (Re)?/, e., the resistance be-
tween the point of observation and the reservoir,

(£) What is the relation of pressure to distal resist-
ance (Rd)? /. e., the resistance between the
point of observation and the point of discharge.

(<:) Which if either of the following formulae repre-
sents the facts:
(11 ) PxRc.
(11') PxRd.

XXI. a. The flow of liquids through tubes, under the

influence of intermittent pressure.

b. The impulse wave.

a. The influence of intermittent pressure.

7. Appliances. — Two glass tubes of about 6 mm. lumen and
about 75 mm. long; a thin elastic tube — thin walled
black rubber — of about the same lumen as the glass tube
and about 150 cm. long; a double valved strong rubber
bulb (about 7.5 cm. long); elastic tubing, large size;
very thick walled rubber tubing for joining up the appa-
ratus; Y tube; two flasks, or water receptacles; heavy
linen thread; a wide capillary and a -fine capillary or
a piece of glass tubing 10 cm. long for constructing the
same; 500 c. c. graduated cylinder.

2. Preparation. — Join the large elastic tube to the entrance
valve of the bulb. Couple the two glass tubes closely
and join one end to the exit valve of the bulb. Make
all joints as close as possible and tie tightly with thread.
Draw a coarse and a fine capillary tube from the 10 cm.
piece of glass tubing.

j. Operation. — Clasp the bulb in the hand and make rhyth
matical contractions at the rate of about fifteen in ten
seconds. The process will, of course, pump the water
from one flask into the other.

4. Observations.

a. Intermittent force and inelastic tubes.

(1) Does the stream of water which is ejected from
the exit tube flow in a constant or in an intermit-
tent jet?

CIRCULATION. 99

(2) Attach a wide capillary and repeat. What is the
character of the stream?

(3) Attach a fine capillary and repeat. Note the
results.

/;. Intermittent force and elastic tubes.

(4) Disjoin the glass tubing from the bulb and join
the elastic tube. Work the bulb as directed above,
and observe the character of the flow.

(5) Join on the coarse capillary and repeat, noting
the change.

(6) Replace the coarse capillary with the fine capil-
lary and repeat. Sum up the results and formulate
conclusions.

c. Quantitative tests.

(7) How much water will be ejected through a fine
capillary tube in ten seconds in experiment (3) ?

(8) How much through a fine capillary in the same
time in experiment (6).

NOTE: In performing experiments (7) and (8) great
care should be used to exert exactly the same force
upon the bulb. The same capillary should be used in
the two experiments.

What is the significance of these two experiments?
b. The impulse wave. The graphic record.
/. Appliances. — Support; cork board (about 8 by 10cm.);
small glass rod about 20 cm. long; corks; needles;
kymograph; piece of sheet lead 1 cm. wide and 5 cm.
long; copper wire No. 16.

2. Preparation. — Make a tracing lever from the glass
rod by drawing out one end to a rather fine point
and drawing the other to about one-half its original
diameter and bending it to make an angle of 135°.
Bend up 1.5 cm. of each end of the sheet lead so that it
will stand at right; angles to the rnicHle 2 centimeters;

100

LABORATORY GUIDE IN PPIYSIOLOGY.

bore the cork and pass the larger end of the tracing lever
through it. Fix the cork board to a ring of the support
with copper wire; fix the sheet lead to one end of upper
surface of the cork board with copper wire and pass a
needle through the limbs of the lead bearings and the
lever-cork in such a way as to bring the lever over the
middle of the board. The completed apparatus will
have the relations indicated in the accompanying cut.
Observations.

(1) If the finger be held upon this elastic tube while
the bulb is being rhythmatically squeezed, a series
of impulses or pulsations will be frit by the finger

FIG. 16.

Place one finger upon the elastic tube near the
bulb, and another three or four feet from the bulb.
Let the bulb be pumped with sudden, but infre-
quent contractions. May one note a difference in
the time of pulsation felt by the two fingers ? If so,
which is felt first ? Why? What is the cause of
the pulsation ?

(2) To get a tracing of this pulse, pass the rubber
_tube across the cork board under the tracing lever
; adjust to kymograph and take trac-
ing. "''VW^the character of the bulb contractions

CIRCULATION. 101

as follows, taking one complete rotation of the

drum for each variation:

(#) Slow initial contraction of bulb and slow re-
laxation

(^) Slow initial contraction of bulb and quick re-
laxation.

(V) Quick initial contraction of bulb and slow re-
laxation.

(</) Quick initial contraction of bulb and quick
relaxation.

(e) Same as d with slow rhythm.

(/) Same as d with rapid rhythm.

(3) Make a careful study of these tracings and deter-
mine :

(#) The characteristic and essential features.

(/£) The accidental and nonessential features.

(V) The cause of the essential ?

(</ The cause of the nonessential features?

XXII. The laws of blood pressure determined from
an artificial circulatory system.

/. Appliances. — Two large Y tubes of about 6 mm. lumen ;
four medium Y tubes, lumen about 4 mm ; eight small
Y tubes, lumen about 2 mm. ; six thick walled capillary
tubes, about 3 mm. outside measurement, and lumen not
to exceed 1 mm. These capillary tubes should be about
15 cm. long. Two T-tubes of medium lumen; two

FIG. 17.

medium sized glass tubes about 75 cm. long. All
rubber tubing should be thin walled and very elastic,
and should be in three sizes, corresponding to the glass
tubes. Two pieces of large size, 75 cm. long, and two
pieces about half that length ; four pieces of medium
size, about 40 cm. long ; ten pieces of small size ; bulb;
heavy linen thread; mercury; large glass receptacle for
water, two medium sized rubber couplings.

102

CIRCULA T1ON. 103

2. Preparation. — First, make two manometers whose dis-
tal limb shall be 40 cm. long, and proximal limb 30 cm.
with a horizontal shoulder 5 cm long. Second,
draw out the two limbs of the medium Y tube
until they are about the same in size as the
small tubing (Fig. 18). Third, construct the
FIG. 18. artificial circulatory system according to Fig. 17.
3- Operation. — First, supply the manometers with mercury
so that there will be 12 to 15 cm. in each limb of the
arterial manometer, and 5 to 10 cm. in each limb of the
venous manometer. If the class is not familiar with the
use and interpretation of the manometer, the demonstra-
tor should lead them to discover all of its essential
features. Second, the whole system should be filled
with water and freed from air before the observations
begin. Third, care should be taken that no stoppage in
the system occurs; otherwise the mercury may be
thrown out of the manometers and lost.
4. Observations.

a. The manometer (mercurial).

(1) Find the actual pressure when the mercury in
the distal column stands 6 cm. higher than that in
the proximal column. Derive the following for-
mula: Actual pressure=13.6 TT r2(2 m — ^), when
r=radius of column of mercury, and m the rise of
mercury in the distal limb of the manometer.

(2) Find the pressure per square cm. where the ob-
servation is the same. Derive the following formula:
Pressure per unit area = 26.2 m.

(3) Which of these data (actual pressure or pressure
per unit area) would be the more valuable to record ?

(4) After the arterial circulatory system has been
freed from air and is at rest, do the proximal and
distal columns of mercury stand at the same level?

104 LABOR A TOR Y G VIDE IN PH YSIOLOG Y.

If not, why? What allowance, if any, should be
made for this?

b. Arterial pressure.

(5) With capillaries 1 to 6 open and tubes 7 and 8
closed, let one member of the division make strong
rhythmical contractions of the bulb at the rate of
about 2 per second. Note effect on manometer.
Account for all the phenomena.

c. Venous pressure.

(6) Note the effect of the contraction upon the venous
manometer. If there is any change in the manome-
ter, compare in rhythm and in extent with the
changes in the arterial manometer.

d. Relations of arterial to venous pressure.

(7) Make very slow contractions. Note results.

(8) Make rapid, strong contractions. Note results.

(9) Make rapid, weak contractions. Note results.

(10) Remove the clamps from vessels 7 and 8 (local
dilatation of arterioks) and repeat experiments 7, 8
and 9, noting and interpreting results. What effect
does a dilatation of arterioles have upon venous
pressure? What effect does it have upon arterial
pressure?

e. Pressure formula.
Let: P ^pressure.

Pa ^arterial pressure.
Pv =venous pressure.
H ^strength of contractions.

Rd = distal resistance beyond point of observation.
v =velocity at point of observation,
r ^radius of vessel at point of observation.
How many of the following formulae will your observa-
tions justify?

CIRCULA TION . 105

1. PaDoH. 6. PaxHxRd.

2. PvDcH. 7. Pa^or2.

3. PaxRd. 8. Pa DoH X RdXr2.

4. Pv xRd. 9. Pa »v.

5. Pa xPv. 10. P o>HxRdXr2Xv.

/. Grafic record of pulse tracing from the artificial circula-
tory system.

With the recording apparatus used in Chapter XXI or
with a sphygmograph, or better, with both pieces of
apparatus, make tracings of the pulsations of the
arterial tubes "a" and «b." (Fig. 17.) Com-
pare all tracings carefully and interpret all the
features of the record, differentiating the essential
from the nonessential, as before.

XXIII. The pulse, sphygmographs and sphygmograms.

1. Appliances. — A sphygmograph; tracing slips; a fish-tail
gas jet, or kerosene lamp.

2, Preparation. — Smoke about two dozen tracing slips.

j. Operation. — That the sphygmograph is so little used by
the general practitioner may be attributed to the fact
that hurry of business, or some other cause, has hin-
dered him from making himself thoroughly conversant
with the adjustment and use of the instrument, with its
limitations and with the interpretation of the tracings.
To adjust the sphygmograph.

First. Let the observer stand with his right foot on a
chair. This brings his thigh into a horizontal position.

Second. Let the subject stand at the right of the ob-
server, resting the dorsal surface of the left forearm upon
the observer's knee.

Third. Let the observer with pencil or pen mark the
location of the radial artery.

Fourth. Let the observer wind the clockwork which
drives the tracing paper; adjust the latter in readiness
for tracing; rest the instrument upon the subject's arm
with its foot upon the radial artery and adjust the posi-
tion, tension and pressure, in such a manner as to obtain
the maximum amplitude of swing of the tracing needle.
Take the tracing. Fix.
^. Observations.

a. The location, etc., of the radial artery.

(1) What are the relations of the radial artery at the
distal end of the radius?

(2) How may the relations vary?

106

CIRCULATION. 107

(3) Is there any variation, among the member of the
division, in the location of the radial artery?

(4) May excessive muscular development affect the
ease with which the artery may be located and its
pulsations studied ?

(5) May excessive deposit of adipose tissue hinder
the observations of the pulse?

(6) May faulty position of subject or of his clothing
affect the pulse ?

The digital observation of the radial pulse.

(7) Feel the pulse with the side or back of the finger;
then with volar surface and tip of each finger of each
hand and note the finger or fingers with which the
feeling is most acute. It will be wise to always use
these fingers in all tactile examinations. Their
acuteness of feeling will increase with practice.
One may thus acquire the educated touch — TACTUS
ERUDITUS.

(8) How much may be learned of the pulse by means
of the touch alone ? Observe and note (a) fre-
quency; (£) rhythm; (V) volume; (//) strength; (e)
compressibility. (/) May anything else be deter-
mined by this method ?

The Sphygmogram.

(9) Take at least three pulse tracings of each indi-
vidual in the division, (a) Compare the tracings
taken from one individual; if they differ, determine
the cause of the difference. (£) Compare tracings
of different members of the division. Determine, if
possible, the causes of the differences.

(10) Do variations of the relations of the artery affect
the sphygmogram? Does the adjustment of the
instrument affect the sphygmogram? Does the

108 LABORATORY GUIDE IN PHYSIOLOGY.

elasticity of the artery affect the tracing ? How
does strength or rate of heart-beat affect it?
Make a list of the facts regarding the condition of the
circulatory system which maybe determined with the help
of the sphygmograph. Make a list of the precautions
necessary to observe in the use of the sphygmograph.

XXIV. To determine the general influence of the vagus
nerve upon the circulation.*

/. Appliances. — Operating case, (Appendix, A-3); a pair
of curved, blunt-pointed shears, or better, a pair of
barber's clippers; a rabbit board; large sheet of heavy
paper; sealing wax; cotton; ether; thread; 1 Daniell
cell; inductorium; vagus electrodes; 2 Du Bois keys; 7
wires; stethoscope; a strong, adult rabbit.
2. Preparations. — Let the six students be subdivided into
three groups of two students each.

Let group "0" be responsible for the anaesthesia.
Use the sheet of heavy paper to make a conical hood,
whose spiral turns may be held in place with sealing
wax. Place a wad of cotton loosely in the mouth of
the cone.

Let group "£" perform the operation. Fix the rab-
bit, back downward, upon the holder; fix the nose in
special holder (see Fig. 19); with the barber's clippers
remove the hair from ventral side of thorax and neck ;
make hands and instruments clean, place instruments
in a shallow basin of warm, 1 per cent carbolic acid
solution; cut two or three ligatures of thread and
place them in the instrument basin.

Let group " c " arrange the electrical apparatus for
stimulation of the nerves. Fill the cell; join up with
contact-key in the primary circuit, and a short-circuit-
ing key in the secondary circuit. Test the apparatus to
see if everything is in order,
j. Operation.

Group "a." (1) Pour 2 cc. or 3 cc. of sulphuric

*Let six students work together.

109

110 LABORATORY GUIDE IN PHYSIOLOGY.

ether upon the cotton in the cone; place the cone over
the rabbit's nose; observe, and note carefully every step
in the anaesthesia.

(2) Carefully note the rate of the heart before begin-
ning anaesthesia.

(3) Keep the cotton moist with ether; watch the
respiration and pulse, and be careful not to give the
animal too much and interrupt the experiment.

Group " £." Wash the clipped surface of the throat.

After the rabbit is completely anesthetized, make
with scissors a median incision through the skin, be-
ginning at the apex of the sternum and cutting anteriorly

FIG. 19.

for about 5 or 6 cm., divide the subcutaneous connec
tive tissue over the middle of the trachea. Carefully
separate from the median line on either side laterally
the subcutaneous connective tissue with the associated
adipose tissue.

How many pairs of muscles come into view? What
two muscles approach the median line to form the apex
of a triangle at the anterior end of the sternum ? Ob-
serve a pair of thin muscles lying dorsal to the muscles
just mentioned and joining in the median line to form a
thin muscle sheet covering the trachea on its ventral
side ? What muscles are these ?

Carefully lift up the median edge of the sterno mas-
toid muscle and separate with the handle of a scalpel

CIRCULATION. Ill

or a seeker the delicate intermuscular connective tissue.
A blood vessel and several nerves come into view.

Is the blood vessel an artery or a vein ? How many
large nerves accompany the blood vessel ?

Take hold of the sheath of the vessel, lift it up and
note in the connective tissue accompanying the blood
vessels two nerves, one large and one small. When the
artery is in its normal position, what relation do these
two nerves sustain to it? Which of the two nerves is
external and which is dorsal to the bloodvessel? Which
is in close relation to the artery? What is the name of
each of the nerves?

In preparing the nerve for stimulation one should
neither grasp it with the forceps nor with the fingers.
It may be separated from the delicate connective tissue
in which it lies by use of a blunt seeker. Far better
than any metallic instrument is a small glass rod drawn
to a point, curved and rounded in the Bunsen lamp
(see Fig. 11-A). Prevent the tissues drying up by
occasionally pressing them lightly with pledgets of
cotton moistened with normal salt solution.

Adjust the electrode carefully upon the vagus and see
that no unnecessary tension is allowed to be exerted
upon the nerve. It is usually necessary to hold the
electrode in place during the observations.

Observations,
a. Anesthesia. (Observations by Group "0.")

(1) Are you able to make out different stages in anaes-
thesia?

(2) How many stages did your animal manifest?

(3) Give the characteristics of each stage.

(4) What effect did the ether have upon the rate of
heart beat?

(5) What effect did the ether have upon the respira-
tion?

1 1 2 LABOR A TOR Y GUIDE IN PHYSIO LOG Y.

b. The stimulation of the vagus. (Observations by
Group " <:.")

(6) Stimulate moderately one vagus. Note with a
stethoscope whether the rate of the heart is in-
creased.

(7) Cut both vagi high up in the neck. Note the
rate of heart beat at intervals of five minutes for
twenty minutes, allowing the rabbit to partially
recover from the anaesthesia.

(8) Stimulate one vagus. Compare the result with
that obtained under experiment (6).

(9) Will very strong stimulation bring the heart to a
standstill ?

(10) If the heart was brought to a complete stand-
still by the stimulation, will it start up again spon-
taneously when the stimulus is removed? Will the
rate reach the degree of acceleration observed in
experiment (*?)?

(11) Sum up the observations into a concise state-
ment as to the influence of the vagus upon the
heart.

NOTE: Dispatch the rabbit with chloroform.

D. RESPIRATION.

IX. a. External respiratory movements, b. Intra=thor»
acic pressure, c. lntra=abdominal pressure.

/. Appliances. — Operating case; clippers; rabbit board;
rabbit; cone for anaesthesia; ether; kymograph; cardio-
graph, which may, in this case, be called a rabbit stetho-
graph; three recording tambours; 10 cm. of glass tubing,
3 mm. lumen; rubber tubing to match; chronograph.

2. Preparation.

(1) Fix and anaesthetize rabbit.

(2) Clip ventral aspect of rabbit's thorax and abdomen.

(3) Prepare thoracic and abdominal cannulae by drawing
the glass tube slightly in the center, cutting diagonally
at the middle, smoothing diagonally on an emery stone.

(4) Join a 30cm. piece of rubber tubing to each cannula
at the larger end, and clamp it near the cannula.

3. Operation.

a. External respiratory movements.

Place the button of the rabbit stethograph upon the
ventral surface of the rabbit as near as possible over the
junction of the diaphragm with the body wall, and a lit-
tle to the right or left of the median line. So adjust the
stethograph as to obtain the maximum excursion of the
recording lever. The stethograph may be held in posi-

113

1 14 LABOR A TOR Y G UIDE IN PHYSIOLOG Y.

tion through the agency of a clamp and support; some-
times, however, better results may be secured by holding
the stethograph in the hands, supporting the wrists on
the edge of the rabbit board.

b. Intra=thoracic pressure.

Locate an intercostal space to the right of the ster-
num and opposite its middle point. Make an incision
0. 5 cm. long, parallel with the intercostal space and 1 cm.
from the sternum. Dissect through the intercostal mus-
cles, taking care not to cut the pleura. Insert the point
of the glass cannula into the wound, press it carefully
through the pleura into the right pleural cavity.

Join the rubber tube to a recording tambour and un-
clamp. Slowly and gently manipulate the cannula until
there is evident communication through the lumen of the
cannula and tube from the pleural cavity to the tambour.

So adjust the cannula that the recording lever makes
the maximum excursion. Bring the levers into such a
relation to the kymograph that the tracing point of the
stethograph lever shall be vertically over that of the
lever which is to record intra-thoracic pressure, and about
two centimeters from it.

c. Intra=abdominal pressure.

Make, in the median line of the abdomen, a one-cen-
timenter incision, limited anteriorly by the xiphoid ap-
pendix. After partially dissecting through the abdom-
inal wall insert the cannula into the incision and care-
fully press it through the peritoneum. If one push
the cannula between the diaphragm and liver he will
usually be successful in getting the free end of the can-
nula into an open space. Care should be taken not to
wound the liver. Take tracing as in b.
<£. Observations.

a. External respiratory movements.

RESPIRATION. 115

(1) During one revolution of the drum — 5 minutes —
note the rate and rhythm of the respiratory move-
ments as recorded by the stethograph, and chrono-
graph.

(2) Does the stethogram show anything more than
rate and rhythm ?

(3) What phase of a respiratory cycle does a rise of
the lever indicate ?

(4) What is the relative duration of inspiration and
expiration as indicated by the stethogram?

(5) Does the stethogram indicate any variation indif-
ferent parts of the inspiratory act ? Of the expira-
tory act?

(6) Differentiate the essential from the nonessential
in the stethogram and determine as far as may be,
the cause of each.

Intra-thoracic pressure.

Trace upon the drum a stethogram and chronogram
as well as an intra-thoracic pressure record, taking
care that the tracing points of the recording tam-
bours are in a vertical line.

(7) Does the rhythm of varying pressure correspond
to the rhythm of the respiratory movements ?

(8) If so, does that necessarily establish between them
the relation of cause and effect?

(9) What change of pressure is indicated by the rise
of the pressure lever?

(10) What movement of the pressure lever corre-
sponds to a rise of the stethograph lever?

(11) What is the condition of intra-thoracic pressure
during inspiration ? During expiration ?

(12) Stop the entrance of air into the respiratory pas-
sages by closing the rabbit's nostrils. What effect
does this have upon the respiratory movements?

1 16 LAB OR A TOR Y G UIDE IN PHYSIO L OGY.

(13) Is the intra-thoracic pressure affected by the ex-
periment ? If so, explain the effect.

(14) If two phenomena correspond perfectly in their
cycles, and if a variation of one is always accom-
panied by a variation in the other, can there be any
reasonable doubt that they sustain to each other the
relation of cause and effect ?

(15) Is one of the phenomena in question the cause
of the other? If so, state which is the cause and
establish your position.

To measure intra thoracic pressure.

(16) Clamp the rubber tube of the pressure appa-
ratus. Replace the recording tambour \\ ith a water
manometer. Unclamp.

Is the pressure during inspiration positive or negative,
and how much ?

(17) Is the pressure during expiration positive or
negative, and how much ?

(18) If the whole apparatus were filled with water
instead of air and water, would it make any essen-
tial difference in the result? What effect do the
variations of the intra-thoracic pressure have upon
the circulation ? Upon the respiration ?

c. Intra-abdominal pressure.

Trace upon the drum a stethogram and chronogram as
well as a record of the intra abdominal pressure.

(19) Does the rhythm of varying intra abdominal
pressure correspond with the rhythm of the respira-
tory movements ?

(20) With what phases, respectively, of the respira-
tion do rise and fall of the intra-abdominal pressure
correspond ?

('21) What influence upon the circulation would rise
of the intra-abdominal pressure exert?

RESPIRATION. 117

(22) Make a quadruple tracing: stethogram, chrono
gram, intra-thoracic pressure and intra-abdominal
pressure.

(23) Sum up the work of the day in a series of con
elusions.

(24) Dispatch the rabbit with chloroform, noting the
respiratory changes induced by the lethal dose of
chloroform gas.

XXVI. Respiratory movements in man. a. The stetho-

graph, b. The thoracometer. c. The belt=

spirograph. d. The stethogoniometer.

/. Instruments. — Besides a kymograph and a chronograph,

the following:

Stethograph. — An instrument for recording graphically
the movements of the chest-walls [Gould].

Thoracometer. — An instrument for measuring (and
recording) the movements of the chest-walls [Gould].

Belt-spirograph. — An appliance for recording respira-
tory changes in thoracic or abdominal girth.

Stethogoniometer. — An instrument for measuring the
curvature of the chest [Gould].

2. Appliances needed in the adjustment and use of these
instruments. — Heavy base support; three large clamp
holders; iron rod, 8 or 10 mm. in diameter and 50 cm.
long; two wooden or iron rods, 1 cm. in diameter and
40 c. m. long ; a receiving tambour ; a recording tambour,
with support; two medium clamp holders; two uni-
versal clamp holders; simple myograph ; 1^ meter
fine fish cord; two pulleys.

3. Preparation. — For construction of apparatus see Appen-
dix A, 10-13.

Adjustment of the apparatus.
a. The Stethograph.

Clamp the center of the iron rod to the heavy base
support. Clamp the wooden rods to the iron
rods so that they will extend out to one side of the
iron rod in a horizontal plane. Figure 20 shows the
Stethograph ready for use.

118

R ESP IRA TWN.

119

Let a member of the division remove all clothing
above the waist and be the subject of observation for
the other members. In making observations with the
stethograph the subject should sit with his back or
side to the table. The observer may readily adjust
the stethograph to record the changes of any lateral
or dorso-ventral diameter of the thorax. For all
observations upon the respiratory changes in the
thorax, the subject should keep the parts of the body
symmetrically disposed.

FIG. 20.

Observations.

(1) How much may be learned of man's respiratory
movements by simple inspection? Make a careful
enumeration and record.

(2) Adjust the stethograph and make a record — a
stethogram — of the changes of the lateral diameter
of the thorax at the ninth rib.

Does the stethograph show more than could be
learned from inspection? If so, what?

(3) Take a stethogram of the lateral diameter at the
sixth rib. How does it differ from the ninth rib
stethogram ? Account for the difference.

120 LABORATORY GUIDE IN PHYSIOLOGY.

(4) Take a stethogram of the dorso ventral diameter
of the thorax over the lower end of the gladiolus.
Compare.

(5) Take a lateral ninth rib stethogram while the
subject reads a paragraph; sighs; coughs; and
laughs. Account for the peculiarities.

(6) Take a lateral ninth rib stethogram after the sub-
ject has taken vigorous exercise. What changes
are to be noted ?

(7) After a similar series of stethograms have been
taken for others, compare; determine the essential
features; give causes of these.

(8) Seek the causes of the difference which exist be-
tween stethograms of different individuals. May
they be accounted for by stature, condition, occupa-
tion or habit?

b. The thoracometer.— Remove from the stethograph
the wooden rod which bears the receiving tambour,
and slip the iron rod of the apparatus described in
Appendix A- 11 into the same place with the button
inward. The accuracy of the apparatus is increased
if the heavy support which bears the spiral spring,
just fixed in position, bear also the recording lever.
Use a simple myograph lever which may be clamped
to the support. The cord which runs over the pulley
beneath the spring must change direction at least
twice after leaving the first pulley. One will need
two more pulleys such as the one described in the ap-
pendix. They may be held in position by clamp
holders. If one use a horizontal drum, however, the
cord may pass from the first pulley direct to the lever.
In either case one would need to pass an elastic band
around the short arm of the myograph lever in such a
way as to draw the lever in a direction opposite to that

RESPIRA T1ON. 121

given it by the spiral spring. In every case the elas-
ticity of the elastic band must be less than that of the
spiral spring, otherwise the rubber button would not
follow the movements of the thoracic wall. So adjust
the apparatus that every movement, however slight,
of the button will be instantly responded to by the
lever.
.'} Observations.

(9) Carefully measure the arms of the lever to deter-
mine how much the tracing point of the lever will
move for every millimeter that the button moves.

(10) When the button is pressed outward in inspira-
tion what direction does the lever move?

(11) Take tracings of the changes in the dorso ven-
tral diameter at the level of the nipples. Deter-
mine by measuring the tracing how much the
dorso ventral expansion is. What is the average
expansion during normal, quiet breathing ? What
is the expansion during forced respiration ?

(12) Make a similar series of observations on the
lateral diameter in the plane of the nipples.

(13) Repeat observations on the lateral ninth rib
diameter.

c. The belt=spirograph.— Substitute for the rod of the
thoracometer which bears the button and spring, a
plain wooden or iron rod. Place the belt-spirograph
around the subject at any level of the body, whose
varying girth is to be observed. The fish cord used
in the previous experiment may be transferred to this
instrument. Tie one end into the eye in pulley No. 1,
pass it over the other pulleys and to the lever; the
horizontal bars may be, raised to the axillae and will
serve to steady the subject. The expansion in girth of
thorax is so great that it may be found necessary to

122 LABOR A TOR Y GUJDE IN PHYSIOLOG Y.

change the relative lengths of the lever- arms to avoid
too great an excursion of the writing point of the
lever.
(4") Observations.

(14) How many millimeters will the point of the
lever rise or fall for every centimeter that the girth
increases?

(15) What is the average expansion of the thorax
during normal quiet breathing?

(16) During five minutes — 75 or 80 respirations — are
all of the respirations practically the same or are
there occasionally deeper breaths? If the latter is
observed is there any regularity in the occurrence
of deeper respirations ? How may occasional deep
respirations be accounted for?

(17) Let the subject make a series of forced respira-
tions. What is the maximum expansion ? What is
the average expansion of the series?

d. The stethogoniometer.

This instrument is described in Appendix A 13. Its
purpose is to record the outline of any horizontal
section of the thorax, though it could be used as well for
tracing the periphera of the abdomen, of the head, or of a
limb. To use the stethogoniometer for the purpose here
intended let the subject sit beside a table upon a
stool adjustable for height. So adjust the stool as to
bring the circumference of the thorax to be observed
even with the upper surface of the table. Fix the
point c, of the instrument, to the table. Let the ob-
server locate, with pen or pencil, upon the side of the
subject distal from the table, a point which shall serve
as a starting point. %

When the point b, of the instrument, rests upon
this point of the subject's thorax the instrument

RESPIRATION. 123

should be well extended, somewhat more than repre-
sented in the figure. Fix a sheet of paper to the table
under the recording pencil at a. To take a graphic
record of the contour of the thorax, proceed as follows:

(18) (#) Let the observer place the tracing point b
upon the "starting point" in the distal side of
the thoracic perimeter.

(£) Sweep the tracing point quickly around one-
half the perimeter to a point approximately oppo-
site to the starting point.

(V) Rotate the curved arm of the instrument upon
its axis bx, through 180°.

(d?) Sweep the tracing point around the other one-
half of the perimeter to the starting point.

(>) The movements of the tracing point, b, in the
horizontal plane have been faithfully recorded
upon the sheet of paper by the recording pencil
at a. It is hardly necessary to remind the student
that the subject must remain motionless during
the observation.

(19) Take a thoracic perimeter with the chest in re-
pose. Measure different diameters of the tracing
and multiply by five to reduce to actual measure-
ments.

(20) Take a tracing at end of forced expiration; at
end of forced inspiration. Compare diameters.

(21) Make a series of these tracings for different in-
dividuals. Compare.

(22) Formulate conclusions.

XXVII. Respiration in man; lung capacity and strength

of inspiration and expiration; chest measure^

merits; the preservation of the data.

/. Instruments. — Spirometer; pneo-manometer; meter tape;
steel calipers; standard, with horizontal arm for meas-
uring height; scales for taking weight.

2. Observations,

(1) Test with the spirometer the lung capacity of each
member of the division. May differences in lung ca-
pacity be accounted for by difference in stature, condi-
tion, occupation or habit?

(2) Take with the tape the girth of chest over the nipples
in a plane at right angles with the axis of the thorax.
(0) With chest in normal repose.

(£) At the end of forced expiration.
(Y) At the end of forced inspiration.

(3) Take the girth of chest over the juncture of the
ninth rib with its cartilage, holding the tape in a plane
at right angles with the axis of the thorax.

(a) With the chest in repose.

(£) At the end of forced expiration.

(Y) At the end of forced inspiration.

(4) With the calipers measure the dorso-ventral diameter
at the level of the nipple, holding the calipers in a
plane perpendicular to the axis of the thorax.

(0) Normal, (£) after expiration, (Y) after inspiration.

(5) Take the lateral diameter in the nipple-plane.

(<*) Normal, (£) after expiration, (Y) after inspiration.

(6) Take the lateral diameter at the ninth rib.

(a) Normal, (£) after expiration, (Y) after inspiration.

124

RESPIRA TION. 125

(7) Test with the pneo manometer the force of inspira-
tion and expiration. (Appendix, A 14). Let each
member of the division test with the pneo-manometer
the maximum positive pressure which he is able to
produce in the respiratory passages during expiration.

(8) Test with the same instrument the maximum nega-
tive pressure which each individual can produce
during inspiration.

(9) Does the face become red in either of these tests?
If such is uniformly observed, account for it.

(10) The preservation of data. Experience has shown
that when data are to be preserved for subsequent use
in the comparison of one class of individuals or cases
with another, it is very much more economical in time
to record the data upon cards.

For the above data one may use such a card as is
appended to this chapter.

In addition to the measurements above given record
upon the cards the weight, the height, the bodily condi-
tion of the individual, and especially whether the indi-
vidual has lived in a hilly or in a flat country, and
whether he has been active or inactive.

Name

Age Weight

Condition: Fat, medium or lean.

Muscular development

Previous occupation

Home Flat or hilly region.

Habit: Inactive, active, (tennis, bicycle. . . .' )

Lung capacity Height

Girth of chest in repose ,

Girth of chest at end of forced inspiration

Girth of chest at end of forced expiration

Girth of chest at ninth rib, repose

126 LABORATORY GUIDE IN PHYSIOLOGY.

Girth of chest after forced inspiration

Girth of chest after forced expiration

Diameter of chest dorso-ventral, in repose

full empty

Diameter of chest, lateral, in repose full

empty

Observer

Date..

XXVIII. The evaluation of anthropometric data.

A large proportion of the problems that the medical
man has to solve involves the finding of averages of a
large number of observations. This is sure to be true of
all anthropometric problems. In the course of the pre-
ceding lesson valuable anthropometric data were collected
and recorded upon cards. The value of this material is
purely potential. Before the data will furnish a basis for
drawing conclusions it is necessary to subject it to a pro-
cess of evaluation. This process consists, first, in group-
ing; second, in getting the average or the median value
for each measurement; and, third, in graphically repre-
senting the averages. In the previous lesson the observer
noted upon each card whether the subject had lived in a
hilly or in a flat country; further, whether he had led a
physically active or inactive life. This gives one an op-
portunity for four groups when the cards from the whole
class are collected.

Group I. Active men from a hilly country.
" II. " " " flat "

" III. Inactive " " hilly "
" IV. " " " flat "

Until recently it has been customary to simply write
the data for any group in columns and "strike an average"
of each column. If there are only 10 to 20 or 30 individ-
uals in each group this method does not entail the unnec-
essary expenditure of much energy, but it is not reliable;
for one " giant " or " dwarf " in any group would vitiate

127

128

LABORATORY GUIDE IN PHYSIOLOGY.

the whole result. If there aie 100 or 1000 individ-
uals in a group, then the use of the old method of finding
the arithmetrical average is exceedingly wasteful of both
time and energy. It must be added, however, that when
the number of observations is large the chances are that
there will be as many dwarfs as giants, thus making the
average approximate closely the median value. It is the
latter that we are seeking, viz. : the median value; this
may be defined as that value which is so located in
the whole series of observations, in a single measurement
of any group, that there are as many below it as above it,
i. e., that fhe numbers of values which it exceeds is equal
to the number of values which exceed it.

Let us take a concrete case. In a group of 316 seven-
teen-year old boys certain physical measurements were
recorded upon individual cards. Let us take for an ex-
ample thegirihof head recorded in centimeters and tenths.
Instead of writing in a column the 316 head girths, each
expressed in three figures, adding and averaging, let us
adopt the new method first suggested by the Belgian as-
tronomer and anthropologist, Quitelet, and later elabo-
rated by Galton, the London anthropologist.* Arrange
the cards in piles, placing in one pile all of the cards
having girth of head 51+ centimeters, in another pile all
having 52-[- centimeters, and so on. In the case in ques-
tion it was found that the 316 cards were quickly distrib-
uted, falling into the following groups:

GIRTH OF HEAD.

51+

52+

53+

54+

55+

56+

57+

58+

59+

60+

NO. OF OBSERVATIONS

(No. of Cards.)

1

7

17

41

70

74

60

29

10

7

*For a more extended explanation and development of this method
than given in this chapter see also " Changes in the Proportions of the
Human Body" — Hall. Journal of the Anthi opological Institute of Great
Britain and Ireland. London, AugUbt, 1895.

RESPIRA TION. 129

The problem is to find the value of the median measure-
ment or the median value. There are 158 values below
the median and as many above.

First. To locate the median observation : This is equiv-
alent to saying — find in the lower series of numbers
(1-7 17, etc.) the 158th observation from either end. It
must be located in the pile of cards which numbers 74.
This group may be called the median group. But where in
this group is the median observation located? In order to
determine this, add the groups at the left of the median
group, these may be called the minus groups, the values
which they represent being less than that of the median
group. l-f-7-fl7-|-4 1 + 70= 136. To this sum one must
add 22 observations from the median group to make 158.
The median observation is then located in the median
group, 22 points from the left.

Second. To evaluate the median observation we must
take it for granted that the 74 observations of the median
group are evenly distributed over the distance between 56
cm. and 57 cm. That being the case the median value
would be 56ff cm.

Let us put a general proposition in the form of an al-
gebraic formula.

Let M = the number of observations in the median
group.

Let n = the total number of observations.

2p = the sum of the plus groups.

2m = the sum of the minus groups.

a = the minimum value of the median group.

d = the arithmetric difference in the minimum values
of the groups.

fj. = the median value to be determined.

d(-£— 2m) df-4

Then * = a +.- Or ,* = a + d- V 2

130 LABOR A TOR Y G UIDE IN PH YSIOL OGY.

Apply this formula to the case taken for example :

I (-¥-'•- i*)

— = — = 56.3.

74
or

1 (-?£- - 106)

P. = 57 — =^— —f- = 57 — 0.703 = 56.3.

After one has found the median value for each
measurement in each group, these may be tabulated and
the values compared. When the table of median values
is large it is almost necessary to carry the work of reduc-
tion a step farther and represent these values graphically
in a chart. Another opportunity will be used for giving
the methods used in the graphic representation of statis-
tical tables.

The table which results from the data collected in
connection with the previous lesson is not so large but that
the observer can practically comprehend the whole at a
glance.

Our grouping enables us to answer the following ques
tions :

First. Has general physical activity any essential in-
fluence in the development of the respiratory organs and
function ?

Second. Is the climbing of hills during early life a
factor in the development of the respiratory organs and
function ?

If both of these questions may be answered affirma-
tively then one would expect to find that the median values
of group I, (active individuals from a hilly country) uni-
formly exceed the values of group II; and that those of
group III uniformly exceed those of group IV, but that
the median values of group II may or may not exceed
those of group III.

The following conclusions are quoted from a student's
note book :

RESPIRATION. 131

(1) " Every measurement of the ' median ' active man
is greater than the corresponding measurement of the
* median' inactive man."

(2) "Every measurement of the median active man
from a hilly country is greater than the corresponding
measurement of the median active man from a flat coun-
try."

(3) "But the active flat country men exceed in their
median measurements the inactive hill country men,
therefore, physical activity isa stronger factor in the devel
opment of respiratory organs than is the topography of
the habitat."

XXIX. The action of the diaphragm.

1. Appliances. — Operating case; clippers ; rabbit board, or
dog board ; rabbit or dog ; ether ; ether cone ; absorbent
cotton ; kymograph ; chronograph ; recording tambour;
beaker with warm water; medicine dropper or bulb. (If
a dog be used, the medicine dropper will not be large
enough, its place may be taken by a soft spherical rub-
ber bulb about 2 cm. in diameter.) Inductorium, 1 cell,
2 keys, vagus electrode, 5 common wires and 2 fine
wires. Sometimes the bulbs mentioned above, and usu-
ually used for this purpose, are not satisfactory. Very
good results may be gotten by using a piece of glass rod,
which has been rounded at one end and sharpened at
the other, as a lever. (Fig. 21.) The rounded end is
passed through the abdominal wall and rests against the
diaphragm, (</). The point is inserted into the cork
button of a tambour. Any contraction of the dia-
phragm presses the round end down, the body wall
serves as a fulcrum (/), the point is pressed up and the
lever of the recording tambour rises.

2. Preparation. — Fix the animal to the board; anaesthetize;
clip anterior median region of abdomen. Put the bulb
into the warm water, join the glass tube of the bulb to the
recording tambour through a rubber tube. This appa-
ratus thus joined may be called a phrenograph and its
record a phrenogram.

Set up electrical apparatus with short-circuiting key
in secondary coil.

j. Operation. — From the posterior extremity of the
xyphoid appendix make a median incision through the

132

RESPIRA TION. 1 33

abdominal walls. If the lever be used the incision
should be just large enough to admit the lever, and
should be located in the angle between the xyphoid and
the costal cartilages on the right side.

Clamp with the serre-fines any small vessels which may
be oozing. After having clamped the rubber tube, which
connects the bulb to the tambour, carefully insert the
warm, wet bulb between the diaphragm and the liver.
The liver will usually afford sufficient resistance to cause
alternate compression and relaxation of the bulb and a
consequent rise and fall of the recording lever; if such
be not the case, the liver may be held in place by two

FIG. 21.

FIG. 21. Glass lever for transmitting movements of the diaphragm (d)

to the receiving tambour. The abdominal wall forms the

fulcrum (/) of the lever.

fingers inserted through the incision. In the meantime
let another member of the division dissect out the left
phrenic nerve. Fig. 22 shows the relation of the phrenic
at the base of the neck, in the rabbit.
4.. Observations.

a. Tactile observation of the diaphragm.

(1) In what condition is the diaphragm during inspi-
ration ? Expiration ?

134

LABORATORY GUIDE IN PHYSIOLOGY.

(2) In what position is the diaphragm during these
two phases of respiration ?

(3) What parts of the diaphragm make the greatest
change of position during inspiration ?

(4) What causes the diaphragm to arch anteriorly
during normal expiration? Are the conditions
changed during the present observations?

kldlPlfX..

FIG. 22.

(5) Are the diaphragmatic movements synchronous
with the costal movements?

b. The normal phrenogram.

(6) Take a phrenogram. What may be learned
from it?

(7) Without varying the adjustment of the phreno-
graph bulb, take a tracing while repeatedly inter*

RESP1RA T10N. 135

rupting the respiration by holding the nostrils.
What does the phrenogram show? What is the
interpretation?

What effect upon intra thoracic pressure would
the holding of the nostrils have?
c. The phrenic nerve and its Junction.

(8) Describe minutely the relations of the nervus
phrenicus in the neck.

(9) Cut the nerve while tracing a phrenogram from
the left side of the diaphragm. Note the result.

(10) Take a phrenogram from the right side of the
diaphragm. Does it differ essentially from the
normal?

(11) While taking a left phrenogram stimulate the
distal end of the left phrenic nerve. Interpret the
result.

(12) While taking a right phrenogram stimulate the
distal end of the left phrenic nerve. Interpret the
result.

(13) Dissect out and cut the right phrenic nerve.
Does the diaphragm cease to move? If it moves, is
its movement active or passive? Account for the
phenomena.

Kill the animal with chloroform.

XXX. Respiratory pressure.

/. Appliances. — Operating case; clippers; rabbit board;
ether; ether cone; absorbent cotton; rabbit stethograph;
kymograph; a small mercury manometer, to the prox-
imal limb of which is attached a thick walled rubber
tube, a piece of glass tubing for a mouthpiece; a screw
clamp; chronograph; two recording tambours; rabbit.

2. Preparation. — Fix and anaesthetize the rabbit, and clip
the ventral surface of the neck. Join up the manometer
as shown in Fig. 23.

j>. Operation. — Make a longitudinal incision over the
trachea. Carefully pass a strong linen ligature under
the trachea. Make a median ventral slit in the trachea
anterior to the ligature. Pass through the slit the limb
of the Y-tube marked 1. (Fig. 23.) Ligate.

4.. Observations.

a. Respiratory pressure. The pneumatogram.

(1) After the ligature is tied how does the rabbit
breathe? Are the thoracic and abdominal move-
ments of respiration accompanied by other respira-
tory movements?

(2) With tube n (Fig. 23) open is there any variation
of the mercury during respiration?

(3) With a screw clamp slowly close tube n. As
the resistance to the flow of air increases what
change is noted in the manometer?

(4) Quickly clamp tube n at end of expiration and
carefully note the manometer reading. Is it posi-
tive or negative?

136

RESP/RA TION.

137

(5) Clamp tube n at the end of inspiration. Is the
pressure positive or negative?

(6) You have been determining certain facts regard-
ing RESPIRATORY PRESSURE. Are the causes of the
changes of respiratory pressure the same as the
causes of the changes of intra-thoracic pressure ?

(7) In what way does respiratory pressure differ from
intra-thoracic pressure?

(8) Disjoin the manometer and join its tube to a re-
cording tambour and trace a pneumatogram, with
stethogram and chronogram.

(9) Compare the pneumstogram with the tracing of
intra-thoracic pressure. Account for all differences.

i Centimete
Scale

FIG. 23.

) Stimulation of the pulmonary vagus.

(10) Count the pulse. Adjust the stethograph, re-
place the manometer, and during the tracing of a
stethogram place the mouth over the glass mouth-
piece; quickly blow into the tube (n) until the
manometer indicates two centimeters of intra
pulmonary pressure; clamp, count the pulse. After
a few seconds release the clamp and let the rabbit
breathe normally for a few minutes.

Repeat the experiment. Vary by producing in turn
3 cm., then 4 cm. and finally 6 cm. of intra-pul-
monary pressure. Fix the stethogram and com-
pare.

138 LABOR A TOR Y G VIDE IN PH YS1 OL OG Y.

(11) Compare your results with those obtained from
other rabbits. What are the essential features of
the modified stethogram ? Formulate conclusions.

(12) What effect has a sudden increase of intra-
• pulmonary pressure upon the rate of the heart's

action.

(13) What nerve is distributed to both lungs and
heart? Admitting that it is possible for the ob-
served effects to be produced through the agency
of the nerves just named, state how this action may
be accomplished.

(14) Could the effects be produced in any other way
than in that which you have given ?

(15) Is the demonstration unassailable; if not, what
experiments would lead to results conclusive for or
against the theory ?

(16) Is the minimum intra-pulmonary pressure,
which typically modified the stethogram, greater or
less than the respiratory pressure of forced ex-
piration ?

(17) What effect upon intra thoracic pressure would
the induction of high intra-pulmonary pressure
have?

(18) What effect upon blood flow would high intra-
pulmonary pressure accompanied by repeated acts
of forced expiration have? What incident effect
upon the rate of heart beat?

(19) Dispatch the rabbit with chloroform after first
arranging the apparatus for a pneumatogram.
While holding the mouthpiece over or in a chloro-
form bottle or sponge, take a characteristic pneu-
matogram of chloroform poisoning.

c. The elasticity of the rabbifs lungs.

(20) After the death of the rabbit open the thorax

RESPrRA TION. 1 39

freely, taking care not to wound the visceral pleura.
The lungs will collapse. Why?

(21) Replace the manometer, gently blow into the
mouthpiece until the lungs have been inflated
to their normal size. Measure carefully the rise of
mercury in the distal column.

What degree of positive respiratory pressure will
the elasticity of the lungs alone cause.

(22) What is the significance of the elasticity of the
lungs in respiration?

d. The cardio-pneumatogram. — Remove the tube n from
the Y-tube, join it to a recording tambour.

(23) Let a member of the division sit in perfect
repose, and while the drum of the kymograph
rotates very slowly, hold the mouthpiece between
the lips. Hold the nose and suspend all respiratory
movements for a period. Let some member of the
division count the pulse of the experimenter.

Trace the cardio-pneumatogram.

(24) Is there a relation between the rhythm of the
pulse and the waves of the tracing ? If so, account
for this relation.

(25) Account for the essential features of the cardio-
pneumatogram.

XXXI. Demonstration: Quantitative determination of

the CO 2 and H2O eliminated from an animal

in a given time.

/. Appliances. — A four-ounce Woulff bottle with three
necks, and with delivery tubes and stopper ground in
the necks [Fig. 24 a], three five-inch calcium chloride
tubes, with side tubes and perforated glass stoppers,
opening and closing the flow of gas [Fig. 24, c, e, f] ;

FIG. 24.

FIG. 24. Apparatus for quantitative determination of the carbon

dioxide gas and water eliminated from an animal in

a given time.

Geissler's potash bulbs with CaCl2 tube ground on (g);
two small flasks (b, h) with rubber stoppers, double-bored,
with delivery tubes fitted as shown in the figure; a one
or two liter bottle with very wide mouth to use as an an-

140

RESPIRA T10N. 141

imal cage, fitted with delivery tubes, and with a cork
impregnated with paraffin; siphon apparatus, as figured,
consisting of two 8 liter bottles with paraffined corks
and tubes; analytical balances; laboratory balances
(correct to 0.01 gm.); drying oven; chemicals, KOH,
Ba(OH)2, CaCl2; any small animal whose weight in
grammes does not exceed \ the volume of the animal
cage expressed in cubic centimeters.
2. Preparation.

(1) Fill the calcium chloride tubes; put them into the
drying oven, where they are to be kept at a tempera-
ture of 100° to 120° C. for several hours; cool in a des-
iccator and weigh upon the analytical balances the
tubes e and f, recording the weight in milligrammes.

(2) Fill the Woulff bottle and the Geissler's bulbs with
a strong solution (50% or more) of KOH. Fix into
position upon the Geissler bulb, its filled and desic
cated CaCl2 attachment, and fit to each end a rubber
juncture; clamp with strong serre-fine forceps and weigh
upon the analytical balances.

(3) Fill the flasks b and h with a strong solution of
Ba(OH)2. These flasks serve simply to show
whether or not the CO2 gas has all been absorbed by
the KOH through which it has just passed.

(4) Pieces e, f and g should be fixed to a light wooden
rack, by which they may be moved; if this is not con-
venient clamp them to supports.

(5) Join up apparatus a, b and c.

(6) Fill siphon apparatus.

(7) Weigh the animal cage.
j. Operation.

(1) Put the animal into the jar; fix the cover so that it
will not leak air.

(2) Join animal cage with c and with siphon appa-

142 LABORATORY GUIDE IN PHYSIOLOGY.

ratus. Start the siphon and note the rate of flow
per minute. The level of the water in the lower hot
tie should be probably 1 meter below that in the upper
bottle. Notice whether the animal seems to be respir-
ing normally; if so, it may be taken for granted, after
ten minutes, that the ventilation is sufficient. If it
seems insufficient one has only to increase the differ-
ence of level in the two siphon bottles.

(3) Disjoin the animal cage and weigh the cage with
the contained animal upon the laboratory bal-
ances. Note the time; join the animal cage in circuit
again, attaching it to e, and attaching z to h. Start
the siphon. The greater resistance to be overcome
will necessitate a greater difference in the level of the
two bottles in order to ventilate at the same rate as
before. To test joints put the finger over the distal
tube of the Woulff bottle (a); if the joints are all right
the siphon stream will stop after a few moments. When
the water in the upper bottle is lowered nearly to the
end of the siphon, clamp the tube joining h to i, set
the empty bottle upon the floor and the full bottle
upon the higher level, join the tube on at k and un-
clamp. This whole change need only occupy a few
seconds. In the meantime CO2 has been collecting,
but it has not been lost.

(4) It is evident that in the afferent apparatus (a, b and
c) one has a means of robbing the air of CO2 and
H2O, thus furnishing the animal with pure, dry air.
It is further evident that in the efferent apparatus one
has a means of collecting absolutely all of the CO2
and H2O given off by the animal during the experi-
ment. Further the weights before and after will show
just how much of these excreta have been passed into
the collecting apparatus.

RESPIRA TION. 1 43

(5) Note the time (one hour or more); clamp siphon
tube; turn the stoppers of e and f, clamp x and y;
disjoin d and weigh it.

(6) Weigh e; weigh f; weigh g.
Observations.

1) How much has the animal lost in weight during the
period of observation?

(2) How much water left the animal cage during the
period of observation?

(3) What was the source of this water?

(4) Did the animal micturate or defecate during the
time of the experiment? If so, is this to be looked
upon as a source of error in the experiment? Would
such an occurrence tend to increase or to decrease the
amount of water caught in the CaCl2 tubes e and f?
Would it cause a discrepancy between the loss in
weight of the animal, as determined, and the com-
bined weight of collected H2O and CO2?

(5) How much CO2 left the animal cage during the
observation ?

(6) What is the total amount of H2O and CO2 collected?

(7) Does the amount of these excreta collected equal
the loss in weight in the animal? What should the
relation of these two quantities be? Explain in full.

(8) What is the respiratory quotient?

(9) Formulate several problems which may be solved
with this method?

XXXII. Respiration under abnormal conditions.

1. Appliances. — Three small animals, e. g., mice, rats,
guinea pigs or squirrels. Three wide mouthed bottles
or jars which may be sealed; scales or large balances;
CO2 generator; water bath; operating case; dissecting
boards.

2. Preparation. — Determine the weight of each animal.
Choose a receptacle whose cubic contents is about two to
three times as many cubic centimentersas the weight of
animal "a" in grams. Choose second and third recep-
tacles whose contents represent about 12 to 15 c. c. to
one gram of animals "b" and "c," respectively.

j. Operation.

I. Preliminary.

a. Put animal "a" into the small jar "a"; count res-
pirations; close the jar.

b. Put animal "b" into jar "b." Before closing count
respirations; close air-tight.

c. Fill jar "c" one-third full of water and displace the
water with CO2. Put animal "c" into the jar, tak-
ing care to allow as little loss of CO2 as possible;
close; count respirations.

II. Post-mortem examination.

After an animal dies fix it to the dissecting board and

open the abdominal and thoracic cavities; take great

care not to cut a large blood vessel; pin the flaps out

so that all of the organs will be exposed and in place.

4. Observations.

a. Respiration in small closed space.

(1) Make careful record of number of respirations

144

RESPIRATION. 145

and general condition of animal "a" in the normal
state, and at the end of every five minutes after the
closure of the jar.

What changes in rate or depth of respiration
have been noted?

(2) Note all abnormal signs and symptoms.

(3) On post-mortem examination record the condi-
tion of heart, large blood vessels, lungs, liver, kid-
neys and the general appearance of the tissues.

(4) Compare the conditions with those found in a
normal animal, prepared by the demonstrator.

Respiration in a larger closed space.

(5) Note all symptoms of animal " b " every five min-
utes after confinement in the jar.

(6) Make a post-mortem examination; record in de-
tail the condition of the organs as in the case of
animal " a."

(7) Compare animal "b" with the normal animal.

(8) Compare animal " b " with animal " a."
Respiration in an atmosphere of one- third CO2

(9) Note all symptoms at intervals of five minutes.

(10) Compare these observations with corresponding
ones from animal " a " and animal "b." What are
your conclusions ?

(11) Make a post-mortem examination; make a record
as before.

(12) Compare appearances in animal "c" with those
in the normal animal; with those of animal "a;"
with those of animal "b."

(13) Make a generalized statement of the facts dis-
covered in the experiments.

(14) What is the cause of death when an animal is
inclosed in a small space?

146 LABORA FOR Y G UIDE IN PHYSIO LOG Y.

(15) What is the cause of death when an animal is
inclosed in a large space ?

(16) Have the relations which you have discovered
any bearing upon the future development of animal
life upon the earth?

XXXHI. Respiration in abnormal media.

/. Appliances. — Three small animals; three jars or wide-
mouthed bottles; hydrogen generator; nitrogen genera-
tor; water bath; potassium nitrite; ammonium chloride;
operating case; dissecting boards.

2. Preparation. — Dissolve 66 grammes of ammonium chlor-
ide in 500 cubic centimeters of water. Dissolve 100
grammes of potassium nitrite in 500 cubic centimeters of
water. Prepare a nitrogen generator as shown in the
figure, using a liter flask. (Fig. 25.)

3. Operation.

a. Pour the two solutions into the generator; adjust con-
ducting tube; heat the mixture in the generator; in a
few minutes nitrogen gas will be given off from the
mixture as the result of the following reaction:

If the jars used by the different divisions are not too
large the above suggested quantities of the solutions
will probably supply enough gas for several divisions.
Put an animal into the jar of nitrogen and close the
jar.

b. Fill a jar full of water, displace it with hydrogen
gas. Put an animal into the jar and close it.

c. Put an animal into a third jar, confining it with a
cloth or a sheet of rubber. Join a rubber tube to an
illuminating gas jet, introduce the end of the tube in-
to the mouth of the jar; turn the gas on for an instant
only. After five minutes allow another momentary
puff of illuminating gas to enter the jar.

147

148

LABORATORY GUIDE IN PHYSIOLOGY.

Observations.

a. Respiration in an atmosphere of nitrogen.

(1) Note all symptoms.

(2) How do these compare with those of death by-
oxygen starvation ?

(3) Record post-mortem appearances.

(4) Compare with previous cases.

b. Respiration in an atmosphere of hydrogen.

(5) Note carefully every abnormal appearance and
symptom.

(6) Make a record of the post-mortem appearances.

FIG. 25.
FIG. 25. Nitrogen generator.

(7) Compare these with the appearances after death
by oxygen starvation; by CO2 narcosis.

c. Respiration in an atmosphere of one- third illuminating
gas (C6>+).

(8) Record all symptoms.

(9) Record post-mortem appearances.

RESPIRATION. 149

(10) How does death in an atmosphere of CO com-
pare, as to symptoms, with death in an atmosphere
of nitrogen ?

(11) Compare it in turn with other forms of death as
induced in this and the previous chapter.

(12) Compare the post-mortem appearances in this
case with those in preceding cases.

E. DIGESTION AND ABSORPTION.

As intimated in the introduction it is taken for granted
that by the time a medical school has found the conditions
propitious for the establishment of a laboratory of experi-
mental physiology, the whole province of chemical physiol-
ogy will have been occupied by the department of
chemistry as a legitimate growth of that department.

The American laboratory of experimental physiology
will present, almost exclusively, the physical problems of
physiology. But even where such are the conditions it
may seem advisable to introduce into a course of lectures
or recitations on the physiology of digestion a series of
demonstrations.

The following exercises in the chemistry of digestion
and the physics of absorption may be given either as dem-
onstrations or as laboratory exercises.

This chapter is not intended as a substitute for any of
the excellent treatises now used in medical schools, but
rather as a supplement to them.

It will be taken for granted that the student has had at
least one year of chemistry before he enters upon this
course.

To give the course which is outlined one will need the
following appliances, apparatus and reagents.

150

DIGESTION AND ABSORPTION. 151

Appliances :

a. Glass ware utensils, &c. ;

10 evaporating dishes, assorted sizes;
10 filters assorted sizes — 5 cm. to 20 cm ;
100 test tubes 15 cm ;
10 beakers 30 c.c. ;
10 beakers assorted — 50 c.c. to 2 L. ;
10 50 c.c. graduated cylinders;

4 graduated cylinders — 100 c.c., 200 c.c., 500 c.c.,
1000 c.c.

3 wedgewood mortars (2^, 4 and 7 in. in diameter) ;
Filter paper;
Labels ;
Pig bladders ;
Thread ;
Rubber tubing;
Glass stirring rods ;

b. Apparatus,

3 Bunsen burners — with rubber tubing;
Filter stand ;

2 supports with rings and gauze ;
8 dialyzers

1 incubator;
Drying oven ;
Meat hasher
Desiccator ;

3 Water baths ;

Platinum dish — 15 c.c. to 100 c.c.
r. Reagents.

Diluted iodine ;

Fehling's solution ;

Sodium hydrate and potassium hydrate;

Copper sulphate;

Distilled water;

1 52 LAB OR A TOR Y G UIDE IN PH YSIOL OGY.

Neutral litmus ;
Concentrated nitric acid ;
Strong ammonia ;
Acetic acid;
Osmic acid 1 % ;
Pure standard pepsin ;

Muriatic acid C. P. (Sp. gr. 1.16 = 31.9 % abs. HC1 ;)
Absolute alcohol ;
Ether;
Chloroform ;
Calcium chloride ;
25 % solution NaOH ;
25 % solution KOH ;
T/2, saturated solution Na2CO3 ;

Nonmedicated absorbent cotton for rapid filtering of
mucilaginous or albuminous liquids.

XXXIV. The carbohydrates.

1. Materials. — Potato starch; dextrin; dextrose; maltose;
lactose; saccharose; cellulose represented by absorbent
cotton and ashless filter paper.

2. Preparation.

(1) To prepare Fehling's solution:

a. Into a half-liter, glass-stoppered bottle put 34.64
gm. CuSO4 c.p., and enough H2O dist. to make
500 c. c. Label the solution: Fehling's solution (a).

b. Into a similar receptacle put 173 gms. of potassic-
sodic tartrate — KNaC4H4O6-f 4H2O [Rochelle
salt] and 50 gm. of NaOH, weighed in sticks; add
enough water to make 500 c c. Label: Fehling's
solution (£). For use mix these two solutions in
equal parts. A convenient quantity for the follow-
ing experiments is 50 c. c. of each in 100 c. c. bottle.

(2) Prepare a starch paste by rubbing 1 gm. of starch to a
creamy consistence with water, add 100 c. c. of distilled
water and boil,

(3) Prepare a dilute solution of iodine by direct solu-
tion in water or by diluting an alcoholic solution.

j. Experiments and Observations.

(1) Put a little dry starch into an evaporating dish; add
some dilute iodine. The starch turns blue. Pour a
few drops of starch paste into a test tube; add a few
drops of iodine. Iodine may be used to detect the
presence of raw or of cooked starch.

(2) Put some raw starch into a test tube or beaker; add
water; stir. The starch does not seem to be at all

153

154 LABOR A TOR Y G VIDE IN PHYSIOLOG Y.

soluble in water. Stir or shake the mixture to bring
the starch into suspension in the water; pour upon a
filter. A clear filtrate passes readily through. Test
the filtrate for starch; result, negative; pour a few
drops of iodine upon the filter, starch present. Con-
clusions:

(#) Potato starch is insoluble in cold water.

(£) The granules of potato starch will not pass
through common filter paper.

(3) Dilute a few cubic centimeters of starch paste; pour
it upon a filter; to the filtrate add iodine. The blue
color indicates that in the cooking of starch the grains
are broken up into particles sufficiently small to readily
pass through the meshes of common filter paper.

(4) In order to determine whether dilute starch paste
will in response to the laws of osmosis pass through
an animal membrane, fill a dialyzer with dilute starch
paste. Set aside to be tested one or two days later.

(5) Put a bit of absorbent cotton into a beaker or test
tube; add water, boil; add iodine. Cellulose, as repre-
sented by cotton fibers, is insoluble in water and does
not respond to the iodine test.

(6) Put a few bits of ash-free filter paper into a test
tube; add water; boil; add iodine. Cellulose, as repre-
sented by the fibers of ash free filter paper, is insol-
uble in water and responds to the iodine test. One
must remember in this connection that in the prepa-
ration of ash-free filter paper mineral acids are used
to dissolve out the salts; and mineral acids, especially
sulphuric acid, so modify cellulose that it responds to
the iodine test with a blue color.

(7) Add water to dextrin in a beaker; stir with a rod.
Dextrin is readily soluble in cold water. To a small
portion add iodine. The solution will probably as-

DIGESTION AND ABSORPTION. 155

sume a wine color; the typical reaction of erythro dex-
trin.

(8) Fill a dialyzer with diluted dextrin solution and
leave for subsequent examination.

(9) Add water to dextrose; it is readily soluble. Add
iodine to a portion of the solution; result, negative.

(10) Fehling's test for a reducing sugar: To a few drops
of the solution add several cubic centimeters of Feh-
ling's solution and boil. A yellowish precipitate of
cuprous oxide (CuO) appears. If the boiling is con-
tinued the color changes to a brick dust red.

(11) To a solution of maltose, add Fehling's solution
and boil; the copper solution is reduced and CuO is pre-
cipitated.

(12) To a solution of lactose, add Fehling's solution and
boil; reduction takes place.

(13) Subject a solution of saccharose to the Fehling
test. No reduction occurs.

(14) Tromer's test for a reducing sugar: To any liquid
suspected of containing a reducing sugar, add a few
drops of very dilute CuSO4 solution; to this mixture,
add an excess of NaOH (or KOH); boil; if the sus-
pected liquid contain a reducing sugar, the CuSO4 will
be reduced with precipitation of CuO. Subject all
of the solutions of sugar in turn to the Tromer test.
Note that the appearance is practically the same as
with the Fehling test. Any differences are due, not to
a difference in the essential reaction but to a difference
in the proportions of the two reagents. The Fehling
test is more satisfactory.

(15) Fill a dialyzer with a dilute solution of dextrose for
subsequent examination.

156 LABORATORY GUIDE IN PHYSIOLOGY.

(16) Fill a dialyzer with a dilute solution of maltose or
lactose for subsequent examination.

(17) Fill a dialyzer with a dilute solution of saccharose
for subsequent examination.

Questions and Problems.

(a) How may carbohydrates be classified ? [Make three
classes.]

(b) Which class has the lowest grade of hydration?

(c) How many of this class are soluble in cold water?

(d) How many are diffusible ?

(e) Which class has the highest grade of hydration?

(f) Are all of those which belong to the third class
soluble in water?

(g) Are they all diffusible ?

(h) How may dextrin be classified ?

(j) How many of the carbohydrates reduce CuSO4 in
presence of an excess of NaOH or KOH ?

(k) How many of the carbohydrates are diffusible ?

(1) How may one determine whether or not cane sugar
passed through the animal membrane ?

XXXV. Salivary digestion.

/. Materials. — Bread; fibrin; pig-fat; olive oil; starch

paste; cane sugar.
2. Preparation.

Remove the parotid and submaxillary glands of several
rabbits or rats, hash them; rinse quickly with water to
remove blood; cover with water. After a few hours
(12-24) filter or strain off the opalescent aqueous ex-
tract. It should contain an aqueous solution of ptya-
lin. Label: Salivary Extract.

(2) Chew a piece of rubber or paraffin. The flow of
saliva is stimulated; catch the secretion in a beaker;
dilute and filter. Label: Salivary Secretion.

(3) Fibrin for use in experiments on digestion may be
procured in any quantity at a slaughter house. Rid it
of all red coloring matter and of accidental contamina-
tion by repeatedly soaking and washing in water. The
white, elastic shreds of fibrin may be kept indefinitely
in pure glycerin. For use one needs only to wash
out the glycerin thoroughly.

j. Experiments and Observations.

(1) Subject saliva (a) and (^) to the Fehling test.
It will be found that neither the extract nor the secre-
tion will reduce the CuSO4.

(2) Subject starch paste to the same test. The result
is negative.

(3) Mix equal volumes of starch paste and salivary
extract in a beaker. Place the mixture in the incu-
bator, which is kept at a temperature of 35° to 40° C.

157

158 LA B OR A TOR Y G VIDE IN PH YSIOL OCY.

After ten or fifteen minutes subject the mixture to a test
with Fehling's solution. If the conditions are normal a
copious precipitate of CuO indicates that a change has
been wrought in the mixture. The starch has been
changed to a reducing sugar by the ptyalin of the
salivary extract.

(4) Mix equal volumes of starch paste and salivary
secretion in a beaker, place the mixture in the incu-
bator for ten or fifteen minutes; test with Fehling's
solution. The presence of a reducing sugar shows
that the secretion of the human salivary glands has
the power to change starch to sugar; to change an in-
soluble, indiffusible foodstuff to a soluble, diffusible
one.

(5) Put a few crumbs of bread into a test tube; add
dilute iodine. Starch is an important constituent of
bread.

(6) Put a few crumbs of bread into a beaker; add
salivary extract; place in the incubator twenty minutes.
Disintegration of the pieces and a marked increase of
the amount of reducing sugar indicates the digestive
action of saliva upon bread.

(7) Put a bit of fibrin into salivary extract; place in
the incubator. An hour or a day will show no appar-
ent change in the fibrin. Had one used any other
proteid the result would have been the same. We are
justified in the conclusion that saliva contains no
ferment capable of changing proteids.

(8) Put a bit of fat or a drop of oil into a few cubic cen-
timeters of salivary extract, shake vigorously; place in
incubator. After an hour or day one sees no change in
the fat or oil, and is justified in the conclusion that
saliva contains no ferment which acts upon fats.

(9) To a small amount of raw starch add salivary ex-

DIGESTION AND ABSORPTION. 159

tract, place the mixture in the incubator; shake fre-
quently; after fifteen minutes test for reducing sugar.
There will probably be a relatively small amount of
reducing sugar. If one watches the progress of the
digestion for several hours he will be convinced that
the cooking of starch very greatly facilitates its diges-
tion by saliva.

(10) Boil a few cubic centimeters of saliva; add starch
paste; place in the incubator for ten minutes; test for
reducing sugar. What is the verdict?

(11) Test the salivary secretion with neutral litmus.
Determine whether its faint, alkaline reaction is essen-
tial to its action as a digestive fluid.

(«) To one portion of saliva add an equal volume
of 0.3% hydrochloric acid and the same amount
of starch paste. The mixture represents 0.1%
hydrochloric acid. Place the mixture in the
incubator for fifteen minutes; test with Fehling's
solution. Verdict ?

(£) Repeat the experiment substituting, for the
hydrochloric acid, lactic acid of the same strength;
place in the incubator for fifteen minutes; test with
Fehling's solution.

What is the conclusion ?

(12) To determine the course of salivary digestion. Mix
50 c. c. of salivary extract with an equal amount of
starch paste. Test a portion with iodine at once.
Test another portion at once with Fehling's solution.
Keep the beaker in a water bath at blood tempera-
ture. Test a portion of the mixture every minute
with iodine and another portion every minute with
Fehling's solution.

(a) What is the first change noted in the digestion
of the starch ?

160 LABORATORY GUIDE IN PHYSIOLOGY.

(£) How many steps may be made out with the
means used and under the conditions existing in
the experiment ?

(V) In what order do the changes occur?

(13) Place some starch paste in a beaker which may be
floated in ice water; similarly float a beaker with
saliva. After both liquids have been cooled down to
near the temperature of the surrounding water, mix
them in one of the beakers; keep the mixture at the
low temperature while subjecting portions of it every
two minutes to the tests suggested above.

(a) May the same changes be made out in this ex-
periment as in the previous one?

(^) Are the changes in the same order?

(<r) State any differences in salivary digestion at
blood temperature and at the low temperature
(0°C) used in this experiment.

(14) (a) Sum up the day's work in a series of conclu-
sions.

(/;) What is the chemical formula of starch ? Of
erythro-dextrin ? Of maltose? Of dextrose?

(<:) Write a chemical reaction or a series of reac-
tions which will be in harmony with the observa-
tions and show as nearly as possible the course of
salivary digestion.

(</) What change has the ferment wrought in the
starch molecule to render the resulting carbohy-
drate capable of diffusion through animal mem-
brane ?

XXXVI. The proteids.

1. Materials. — An egg; fibrin; gelatine; myosin; syntonin;
acid albumin; commercial peptone (mixed albumoses,
proteoses and peptones); Griibler's pure peptone.

2. Preparation.

(0) To prepare myosin:

(1) Take one pound of lean meat, grind it in the meat
hasher; soak and wash repeatedly until the tissue is
nearly white and quite free from haemoglobin.

(2) Put the washed muscle tissue into a flask with an
equal bulk of a 20% solution of ammonium chloride;
shake from time to time for 24 hours.

(3) Strain off the liquor and add to it 20 volumes of dis-
tilled water. Myosin is precipitated. Wash the pre-
cipitate. Redissolve one- fourth of the precipitate in
10% NaCl, and label: Saline Solution of Myosin.

b. To prepare syntonin. — To the remaining three-fourths
of the washed myosin add several volumes of 0.1% hy-
drochloric acid. In a very short time the myosin will
be dissolved and changed to syntonin.

c. -To prepare dilute egg albumin. — Make an opening in
one end of the shell of an egg; drain off the white of the
egg, catching it upon a coarse linen cloth — a towel serves
the purpose well; press the albumin through the meshes
of the linen into a beaker; add 400 or 500 cubic centi-
meters of distilled water; transfer the mixture to a 1 L.
cylinder and shake vigorously; after a short time filter
through pure absorbent cotton or strain through fine
linen.

161

162 LABOR A TOR Y G UIDE IN PHYS1OLOG Y.

d. To prepare acid albumin, — To 100 c.c. of dilute egg
albumin add an equal quantity of 0.2% hydrochlo-
ric acid; place the mixture in the incubator for two
or three hours. Though the change begins at once it
will probably not be complete before the time suggested.
If one wishes to isolate the acid albumin from the mix-
ture he has only to carefully neutralize with sodic hy-
droxide precipitating the acid albumin, and to wash the
precipitate with distilled water. For the purposes for
which it is to be used in the following demonstration it
may be left in the acid solution which represents 0.1%
HC1.

Label: Acid Albumin Solution in 0.1% HC1.
e. — Make an aqueous solution of the commercial "pep-
tone," and though peptone is present in small propor-
tion, label it: Proteoses.

f. Make an aqueous solution of a few grammes of Grii-
bler's pure peptone, and label: Peptone.

g. Dissolve a few grammes of gelatin in distilled water.
h. To prepare Millorfs reagent: 1st. To 100 grammes of

pure mercury add an equal weight of concentrated
nitric acid c. p. The reaction proceeds at room
temperature, though gentle heat may be applied to
complete the solution of the mercury. 2d. Cool the
mixture; add two volumes of water; after 12 hours
decant the supernatant liquid — Millon's Reagent.
3. Experiments and Observations.

(1) Pour into test tubes a few cubic centimeters of
each of the following proteid solutions and subject
each in turn to a temperature of 57°C, then to a tem-
perature of 63°C, and finally a temperature of 100°C,
by dipping the tubes into waterbaths of the tempera-
tures named:

(a) Dilute egg albumin.

DIGESTION AND ABSORPTION. 163

(£) Saline solution of myosin.
(<r) Syntonin in acid solution.
(X) Acid albumin in acid solution.
(e) Gelatin in aqueous solution.
(/) Proteoses.
(£•) Peptone.

Record the results in a table and formulate con-
clusions.

(2) Subject the same series of proteids to the cold nitric
acid test by first pouring one or two cubic centimeters of
strong nitric acid into a test tube, then with pipette care-
fully floating the proteid liquid upon it. In the case oi
dilute egg albumin a characteristic white ring forms
between the acid and the albumin. Note in each case
whether or not a typical ring is formed.

(#) Dilute egg albumin.

(£) Saline solution of myosin.

(*T) Syntonin.

(</) Acid albumin.

(<?) Gelatin.

(/) Proteoses.

(£•) Peptone.

Tabulate results and formulate same in a concise
statement.

(3) The Xanthoproteic test.

Use the tubes and materials already prepared in the
cold nitric acid test. Shake the tubes to mix the acid
with the proteid. In some cases a coagulum will be
formed and this coagulum turns yellow on boiling if
the tube is held in a Bunsen flame. After the coagu-
ium has been boiled in the acid, cool under the hydrant
or in a pail of ice water and add strong ammonia to
alkaline reaction. The light yellow coagulum which
forms in the case of egg albumin turns to an orangecolor.

164 LAB OR A TOR Y G UWE IN PHYSIOLOG Y.

This test is usually given as a universal proteid test.
Tabulate results on the above suggested series (a)-(g)
noting any variations of the reaction in the different
proteids. Besides variations in the reaction with dif-
ferent proteids there are marked variations with differ-
ent strengths of sol-ution of the same proteid.

(4) A general test for proteids is to heat a proteid-con-
taining liquid with half its volume of Millorts reagent.
A precipitate appears which is yellowish at first but
turns red under the influence of heat. Test each of
the above list of proteids (a-g), with Millon's reagent.
Record results.

(5) The Biuret test.

To a suspected liquid add an excess of sodic hydrate;
shake well and to the mixture add one or two drops
of a very dilute solution of cupric sulphate. A violet
color appears which on heating becomes deeper in
shade.

A most convenient reagent for this reaction is a
mixture of the solutions (a) and (b) of the Fehling's
test not in equal quantities as in the typical Fehling's
solution, but in the proportion of nine parts of the
sodic hydroxide solution (b) to one part of the cupric
sulphate solution (a) and add an equal volume of dis-
tilled water to the mixture.

Tabulate results on the proteid series (a) to (g).

(6) Subject each of the series of proteids (a) to (g) to
each of the following reagents tabulating results:

(I) Picric acid, saturated solution.

(II) Absolute alcohol.

(III) Mercuric chloride, saturated solution.

(IV) Tannic acid, saturated solution.

(V) Silver nitrate, 10% solution.

(VI) Ammonium sulphate, saturated solution.

DIGESTION AND ABSORPTION. 165

On which of the proteid solutions would one get

a precipitate with silver nitrate independent of the

presence of proteid?

(7) To separate peptone from other proteids. — It will have
been noted that ammonium sulphate precipitates all
proteids except pure peptone. If one has peptone
mixed with proteoses and unchanged proteids one may
demonstrate its presence by precipitating out the other
proteids and then demonstrating by such a test as the
Biuret test the presence of a proteid in the clear fil-
trate; that could be nothing else than peptone.

Test commercial peptone in this way and determine
whether any appreciable proportion of it is peptone.
(£) The diffusibility of proteids. — Fill seven dialyzers
with the proteids above studied.

On the following day test the diffusates for proteids.

XXXVII. a. Diffusibility of proteids.
b. Milk.

a. Diffusibility of proteids.

/. Materials. — The seven dialyzers filled at the end of

the previous demonstration.
2. Experiments and Observations.

( 1 ) What reagent may best be used to determine whether
or not any of the egg albumin has diffused through the
animal membrane?

(2) How may one determine whether or not any of the
salts of the egg albumin have diffused through the
membrane?

(3) In the case of the saline solution of myosin (b), of
syntonin (c) and of acid albumin (d), is there any con-
traindication against silver nitrate as a reagent to
determine whether proteid has diffused?

What would silver nitrate indicate in this case ?
(4") What tests would be most reliable in these cases to
detect the presence of proteid in the diffusate ?

(5) Would a trace of proteid in the diffusate necessarily
demonstrate the diffusibility of these proteids through
the walls of the alimentary tract ? If not; why not ?

(6) What tests may be used to determine the presence
of gelatin in the diffusate ? Is gelatki diffusible?

(7) The term proteoses is a general one and is used to
designate the mid-products of proteid digestion. The
mid-product of albumin digestion is albumose; of
globulin digestion, globulose; of myosin, myosinose;
of vitellin, vitellinose; of casein, caseinose; or in gen-
eral of a proteid, proteose.

166

DIGESTION AND ABSORPTION. 167

Dialyzer (f) contains products of peptic digestion
of proteids — principally albumin. The progress of
digestion was suspended at a stage when there were
present not only peptone but mid-products — albu-
moses; or, to use the general term, proteoses

The problem which confronts us is — to determine
whether or not proteoses are diffusible.

(a) If peptone is diffusible the diffusate will cer-
tainly contain peptone. Do peptone and the pro-
teoses respond alike to all the general tests for
proteids?

(b.) How may peptone be separated from the pro-
teoses ?

What single reagent is indicated in the case?
(8) Demonstrate the diffusibility of peptone.
b. Milk.

1. Materials. — One liter of fresh whole milk; one liter of
milk for the preparatory steps of the demonstration.

2. Preparation.

(1) On the day before the demonstration fill a 500 c. c.
open mouthed cylinder with milk and put it in a cool
place.

(2) Two days before the demonstration weigh out 10
gm. to 50 gm. of whole milk in a platinum dish or in
a thin porcelain dish. Place it in a drying oven at
90°-95°C, and dry to constant weight. Record the dry
weight.

(3) Before the hour of the demonstration burn the resi-
due by bringing the dish which contains the dry solids
to a red glow in a Bunsen flame, allowing ample access
of oxygen. After the dish and the white ashes have
cooled in a desiccator take the weight. All of these
weights should, of course, be taken upon an analytical
balance.

168 LABOR A TOR Y GUIDE IN PHYSIO LOG Y.

(4) Fill a dialyzer with diluted milk one day before the

demonstration.
J. Experiments and Observations.

(1) What proportion of milk evaporates at the tempera-
ture above suggested ? It may be taken for granted
that this proportion represents practically the water
of the milk.

(2) Of the solids of milk what proportion is organic and
what proportion is inorganic?

(3) What bases predominate in the ashes? [Let a
student be assigned this problem for solution.]

(4) What is the character of the organic constituents of
milk?

(a) Note that the milk that has been standing has
separated into two layers, an upper yellowish layer
and a lower bluish white layer.

(b) Draw off with pipette a few cubic centimeters of
the cream and in a test tube add an equal volume of
osmic acid. To a few drops of olive oil in another tube
add osmic acid. Shake both tubes vigorously. Osmic
acid has the same effect upon the cream as upon the
olive oil. The cream is, in fact, fat in physiological
emulsion. Quantitative examination shows that
about 4% of milk or 4 13 of the solids of milk con-
sists of fats in which olein predominates.

(5) Fill a siphon with water and introduce it through
the cream to the bottom of the 500 c. c. cylinder; draw
off 300 c. c. of the milk; add to it four volumes of
water; slowly add 1% acetic acid while stirring with a
rod, until the casein separates as a copious flocculent
precipitate. After the casein has partially settled de-
cant off a few cubic centimeters of the supernatant
liquid and subject it to the Fehling test. The abun-
dant precipitate indicates the presence of a reducing

DIGESTION AND ABSORPTION. 169

sugar. It is milk sugar — lactose. About 4.4% of
milk or y$ of the solid matter of milk is lactose.
(fi) Wash the casein by the repeated addition of water,
followed by decantation; pour it into a linen sack
or a towel and press out the water; further extract
the water with absolute alcohol; extract the remnant
of fat with ether; dry in the air. The white granular
material that remains is nearly pure casein, the most
important proteid of milk, and represents nearly 4%
of milk.

(7) Heat 100 c. c. of the fresh milk in a beaker. Before
the boiling point is reached a membrane gathers upon
the surface of the milk. This membrane represents
the lact-albumin of the milk, which has been coagu-
lated by the heat and has collected in the membranous
coagulum at the surface. The lact-albumin repre-
sents only a small proportion of the milk proteid.

(8) To 30 c. c. of fresh milk in a beaker add common
salt to saturation. Record results.

(9) To 30 c.c. of fresh milk in a beaker add magnesium
sulphate to saturation. Record results.

(10) Dilute fresh milk to one-fifth normal and subject it
to the following tests, recording results:

(#) The iodine test.

(^) Tromer's test.

(V) The xanthoproteic test.

(//) The Biuret test.

(>) The picric acid test.

(/) The absolue alcohol test.

(£•) The osmic acid test.

(11) Fill a dialyzer with the diluted milk. One day
later examine the diffusate:

{a) For any of the inorganic constituents of milk.
(/>) For the carbohydrate constituents of milk.

170 LABORATORY GUIDE /AT PHYSIOLOGY.

(c) For the proteid constituents of milk.

(d) For the fatty constituents of milk.

(12) Formulate in a series of concise statements the
facts demonstrated regarding milk:
(a) Its chemical constituents.
(£) Its physical properties.

Why should milk be discussed in connection with the
proteids rather than with the carbohydrates; considering
that the proportion of carbohydrate in milk is greater than
that of proteid?

XXX VII I. Gastric digestion.

/. Materials. — -Two fresh pig-stomach's; ^ Ko. clean sea
sand; 4 eggs; fibrin; bread; milk; jellied gelatin; casein;
rennin.

2. Preparation.

( 1 ) To prepare artificial gastric juice.

(a) Stretch a fresh stomach of a pig upon a board
with mucous surface up; fix with nails.

(£) Rinse off the mucous membrane gently with cold
water.

(V) Scrape thoroughly with a dull edged table knife,
or an equivalent; collect the scrapings in a large
mortar.

(dT) Grind the scrapings in clean, fine sand.

(/) Add an equal volume of 0.2% HC1 and leave for
24-48 hours, stirring occasionally.

(/) Strain through linen; filter, and preserve in a glass
stoppered bottle. Label: Acidulated aqueous extract
of pepsin.

(£•) For use dilute this extract with three or four vol-
umes of 0.1% HC1 (App. A-17). Label: Artificial
gastric juice (1).

(2) To prepare a glycerin extract of pepsin.

(a) Rinse off the mucous membrane of a fresh pig-
stomach with cold water and remove the mucous
membrane from the muscular walls of the stomach.

(£) Grind the mucous membrane in the meat hasher.

(/) Put the hashed tissue into a beaker and cover
with two volumes of pure glycerin. Stir the mix-

171

172 LABORATORY GUIDE JN PHYSIOLOGY.

ture occasionally for several days. The glycerin

extracts the pepsin ferment.
(rtT) Strain the glycerin extract through fine linen;

preserve in a glass stoppered bottle for future use.

It will keep indefinitely.
(*) For use add to 1 volume of the extract 30 to 50

volumes of 0.2% HC1. Label: Artif. gast. juice (2).
j. Experiments and Observations.

(1) To a bit of starch paste of the consistency of jelly
add artificial gastric juice (1); place in the incubator;
in ten minutes or one day note results. Results?

(2) To a few drops of olive oil or to a bit of pure
tallow add several cubic centimeters of gastric juice
and keep at incubator temperature for a day. What
effect has gastric digestion upon fat or oil ?

(3) To a bit of pig fat add gastric juice and keep at
incubator temperature for several hours. What
effect has gastric digestion on adipose tissue ?

(4) To a bit of fibrin in a test tube add gastric juice.
The warmth of the hand will be sufficient. If the
preparation of artificial gastric juice has been suc-
cessful, the fibrin will dissolve in one or two min-
utes. One may be certain that digestion is pro-
gressing rapidly, though complete solution of the
fibrin does not necessarily indicate complete diges-
tion of it; for complete digestion of a proteid im-
plies that the food stuff in question is both dissolved
and diffusible. The fibrin is dissolved, it may or
may not be diffusible. But this will be determined
later.

(5) To determine the active factors of gastric digestion,
(a) To a few shreds of fibrin in a test tube add a

few cubic centimeters of 0.2% HC1. Carefully note
results. Will dilute HC1 dissolve fibrin? Is it

DIGESTION AND ABSORPTION. 173

possible to digest a proteid without dissolving it?
(£) To fibrin add dilute neutral glycerin extract of

pepsin. Is solution affected ?

(r) To tube (a) add a few drops of the glycerin extract
of pepsin.

To tube (b) add 2 volumes of 0.2% HC1.
Note results.

(X) Formulate conclusions.

) To determine whether the acid factor of gastric diges-
tion need necessarily be hydrochloric acid.

Prepare a 0.4% solution of each of the following
acids:

(I) Lactic acid.

(II) Sulphuric acid.

(III) Nitric acid.

(IV) Phosphoric acid.

(V) Citric acid.

(VI) Acetic acid.

For each acid prepare four test tubes as follows:
(I) Lactic acid.

(#) Fibrin -f- 1 c. c. glyc. ext. of pepsin -{- 10 c. c.

0.4% acid.
(£) Fibrin -j- 1 c. c. pepsin ext. -|- 10 c. c. 0.2%

acid.
(c) Fibrin -f- 1 c. c. pepsin ext. -j- 10 c. c. 01%

acid.
(^/) Fibrin -f- 1 c. c. pepsin ext. -f- 10 c. c. 0.05%

acid.

Proceed in a similar manner with each acid.
Tabulate results. May any other acid or acids
take the place of HC1 as a factor in digestion ?
If so, in what minimum strength? Which one of
the above acids may be normally present in the

174 LAB OR A TOR Y G U1DE IN PHYSIOL OGY.

stomach? May any of the above acids serve as
digestives and as foods?

As digestives and as tonics?
As digestives, foods and tonics?
Cite authorities.

(7) To determine the optimum strength of the hydro-
chloric acid.

Prepare with care the following three dilutions of
hydrochloric acid: 10%, 1%, 0.1%. [See Appendix
A, 17.]

Into twelve test tubes put as many small masses
of fibrin; into each tube put 1 c. c. of neutral 10%
dilution of glycerin extract of pepsin. Label and fill
tubes as follows:
Tube (a) 5%: Add to the fibrin 5 c. c. of 10% HC1

and of distilled water a quantity sufficient to make

10 c. c.
Tube (b) 2%: Add 2 c. c. of 10% HC1 and aqua dist.

q. s. ad 10 c. c.
Tube (c) 1%: Add 1 c. c. of 10% HC1 and aqua dist.

q. s. ad 10 c. c.
Tube (d) 0.5%: Add 5 c. c. of 1% HC1 and aq. dist.

q. s. ad 10 c. c.
Tube (e) 0.4%: Add 4 c. c. of 1% HC1 and aq. dist.

q. s. ad 10 c. c.
Tube (H 0.3%: Add 3 c. c. of 1% HC1 and aq. dist.

q. s. ad 10 c. c.
Tube (g) 0.2%: Add 2 c. c. of 1% HC1 and aq. dist.

q. s. ad 10 c. c.
Tube (h) 0.1%: Add 1 c. c. of 1% HC1 and aq. dist.

q. s. ad 10 c. c.
Tube (j) 0.05%: Add 5 c. c. of 0.1% HC1 and aq. dist.

q. s. ad 10 c. c.

DIGESTION AND ABSORPTION. 175

Tube (k) 0.025%: Add 2.5 c. c. of 0.1% HC1 and aq.

dist. q. s. ad 10 c. c.
Tube (1) 0.01%: Add 1 c. c. of 0.1% HC1 and aq. dist.

q. s. ad 10 c. c.
Tube (m) 0.005%: Add ^ c. c. of 0.1% HC1 and aq.

dist. q. s. ad 10 c. c.

Place these twelve tubes in the incubator and note
conditions every 10 minutes for the first hour, every
hour for the first six hours and then at the end of one
or two days make the final observations.

Tabulate results. Formulate conclusions. What
range of strength may, from the experiments with
artificial gastric juice under artificial conditions, be
considered the optimum strength for the acid? Is
there any reason to doubt that the optimum strength
as determined above is essentially different from the
optimum strength in normal digestion ?
(8) To determine how dilute the pepsin may be and still
be efficient in digestion.

This experiment requires a standard solution of
pepsin to use as a basis. The U. S. Pharmacopoeia
(p. 295 of the 7th Decennial Revision) gives the fol-
lowing formula for a standard solution of pepsin:
Hydrochloric acid (absolute), 0.21 gm.
Pepsin (pure), 0.00335 gm.
Water (distilled), q. s. ad 100 c. c.

The following suggestions are made as to method
of preparation: To 294 c. c. of water add 6 c. c. of
dilute hydrochloric acid: — SOL. A.*

In 100 c. c. of Sol. A. dissolve 0.067 gm. of standard
pepsin:— SOL. B. To 95 c. c. of Sol. Aat 40°C. add 5 c. c.

*HC1. DIL. contains 10$ of Abs. HC1. The C. P. muriatic acid of
standard Sp. Gr. contains 31.9$ Abs. HC1.

176 LABORATORV GUIDE IN PHYSIOLOGY.

Sol. B. The resulting mixture is a standard artificial
gastric juice of the formula given above, and has the
power of completely digesting at 38°-40°C one-fifth its
weight of coagulated egg albumin in six hours.*

From a standard gastric juice prepare the following
dilutions using 0.1% HC1 as a diluent. It is scarcely
necessary to say that the greatest care should be
taken, (1) to make all measurements with preci-
sion; and (2) to thoroughly shake each dilution before
drawing off the material for the next lower dilution.
(#) Standard artificial gastric juice 10 c. c. + 1 c. c.

moist fibrin.
(£) ^ standard artificial gastric juice 10 c. c.-(-l c. c.

moist fibrin.
(0 liu standard artificial gastric juice 10 c. c.-(-l

c. c. moist fibrin.

(d) Tojo7 standard artificial gastric juice 10 c. c.-f-l
c. c. moist fibrin.

(e) -fo,Vi>T) standard artificial gastric juice 10 c. c.-f-l
c. c. moist fibrin.

(/) T^O!OOO standard artificial gastric juice 10 c. c.-j-

1 c. c. moist fibrin.
C?0 T.inFo.innF standard artificial gastric juice 10 c. c.-f-

1 c. c. moist fibrin.

Keep tubes in incubator or water bath at 38°-40°C.
Note (1) time required to dissolve fibrin completely,
(2) time required to change all acid albumin to pro-
teose or peptone. Will one millionth standard gastric
juice digest fibrin at all? Will a lower dilution (one
ten-millionth) digest it; if so, how dilute, and how
long a time is required?

*For details of testing standard gastric juice see Pharmacopoeia.

XXXIX. Gastric digestion, continued.

j. Experiments and observations, continued.

(9) To determine the influence of the hydrochloric acid of the
gastric juice upon putrefaction in the stomach. — It has been
determined that the hydrochloric acid in the stomach
destroys, under favorable conditions, at least the non-
pathogenic forms of bacteria. Let us determine the
strength of acid necessary to destroy the common bac-
teria of putrefaction. To each tube used in experiment
(7) add a minute drop of any putrefying fluid. If the
contents of a tube serve as a good culture field any drop
of the fluid may be found to be swarming with bacteria
within a few hours. Within a few hours after infect-
ing the tubes examine under high power — 700 to 1000
diameters — a drop of the contents of each tube.
While making the observations take care not to
contaminate one tube with the contents of another.
That the tubes containing 5% or 2% or 1 % hydro-
chloric acid will be found to be free from bacteria goes
without saying. Just how weak may the acid be and
destroy the bacteria ? How weak may the acid be and
retard their development? Could one readily drink
enough liquid at a meal to change the stomach from a
sterilizing field to a culture field for the bacteria of
putrefaction ?

(10) To determine the influence of neutral salts upon diges-
tion.— Make a saturated aqueous solution of common
salt; also \ sat. sol, and fa sat. sol.

(» To 8 c.c. of NaCl sat. sol. add 1 c.c. of a 1%
177

178 LABORATORY GUIDE IN PHYSIOLOGY.

HC1, and 1 c.c. glyc. ext. of pepsin; put the mix-
ture into a test tube; label: NaCl sub. saturated.
Drop in a bit of fibrin and put into the incubator.
Take six test tubes, provide each with a bit of
fibrin; label and fill each as follows:

(£) | Sat. NaCl : — 5 c.c. artif. gast. juice + 5 c.c.
NaCl sat.

(c) J Sat. NaCl : — 6 c.c. artif. gast. juice -f 2 c.c.
NaCl sat.

(dT) | Sat. NaCl : — 5 c.c. artif. gast. juice -(- 5 c.c.
NaCl i sat.

O) TV Sat. NaCl : — 6 c.c. artif. gast. juice + 2 c.c.
NaCl i sat.

(/) sV Sat- NaC1 : — 5 c-c- artif- Sast- Juice + 5 c-c-
NaCl T\ sat.

(£•) ^V ^a*- NaCl : — ti c.c. artif. gast. juice -{-2 c.c.
NaCl TV sat.

What fraction of saturation with table salt stops
proteid digestion ? Explain its action. How
much NaCl per litre would that represent? Has
this any hygienic bearing?

(11) The effect of mechanically confining the fibrin to pre-
vent its swelling. — Tie a small mass ot fibrin rather
tightly with several turns of white thread; drop it into
a test tube containing artificial gastric juice; put the
tube into the incubator and watch results.

How long a time is required to digest the fibrin?
Has this any hygienic significance ?

(12) The influence of division upon the time required to
digest proteids. — Boil an egg five to ten minutes; cool
quickly; separate the hard coagulated white from yolk
and envelopes.

DIGESTION AND ABSORPTION, 179

(a) Cut out a one centimeter cube and put it into a

beaker with 40 c c. artificial gastric juice.
(£) Put into a second beaker of 40 c.c. gastric juice
a centimeter cube which has been divided into
eight half-centimeter cubes.

(c) Prepare another beaker in which are 16 quarter
centimeter cubes in 10 c.c. of artificial gastric juice.
(</) Into another beaker with 10 c. c. artificial gastric
juice put J of a cubic centimeter of the egg albu-
min which has been finely divided by pressing
through a fine sieve.

Note time required in each case to completely
digest the albumen.

Has this any hygienic bearing ?

(13) The influence of temperature upon the time required to
digest proteids. — Prepare five tubes by first providing
each with 5 c.c. of artificial gastric juice; treat the
several tubes as follows:

(a) Bring to 60°C. in water bath; add fibrin; note

time.
(/) Bring to 50°C. in water bath; add fibrin; note

time.
(/) Bring to 30°C. in incubator; add fibrin; note

time.

(//) Leave at room temperature (20°C.); note time.
(e} Bring to 0°C. in ice water; add fibrin; note time.
What is the optimum temperature?
Is the progress of digestion materially retarded
by a reduction of the temperature ?

Would the temperature of the stomach contents
be essentially lowered by the occasional sipping
of an iced beverage during a meal?

What is the hygienic significance of the experi-
ment ?

XL. Gastric digestion, continued.

Experiments and Observations, continued.

(14) The steps of gastric digestion.

Boil an egg 5 to 10 min.; cool quickly; separate out the
white; press it through a fine sieve; put into a beaker
with 100 c. c. artif. gastric juice, and place the beaker
in a water bath at 40°C. At intervals of 2 minutes for
the first 10 minutes; then at intervals of 5 minutes for
the next 20 minutes; then at intervals of 10 minutes
forthe second half hour and after that at intervals of one
hour, subject the liquid to tests for egg albumin; for
acid albumin; for albumose; for peptone. In what order
and after what length of time do the several products
appear? Is the one that is first to appear also first to
disappear ?

(15) The artificial digestion of various proteids.

(a) To a small mass of jellied gelatin add 10 to 15
volumes of artif. gast. juice, and note effect.

(^) Subject bread to the xanthoproteic test. The
presence of proteid material is demonstrated. Put
a small piece of dry bread into a beaker with gastric
juice, and note effect.

(<:) Note the course of casein digestion,

(</) Triturate in a mortar well cooked lean meat; di-
gest with gastric juice.

(e) Try the xanthoproteic test upon cooked beans or
peas; proteid is present. Triturate in a mortar; di-
gest.

(/) In each case, demonstrate the ultimate appear-
ance of peptone.

180

DIGESTION AND ABSORPTION. 181

(16) The artificial digestion of milk.

Of fresh milk take three portions of 5 c. c. each.

(a) To one portion add 10 volumes of artif. gast.
juice; and place it in the incubator at 38° — 40°C.

(£) Prepare another beaker in the same way but
place it in a water bath at 38° — 40°C. and keep the
mixture well stirred, dividing the casein coagulum
as fine as possible.

(/) Place the third portion of milk in the water
bath. When it has become warm add a few centi-
grams of rennin. Fifteen minutes later add artif.
gast. juice. Stir as in (b.) In which of the first
two does digestion seem to progress the more rap-
idly? Does the progress or process of the digestion
seem to be materially different in the last two ex-
periments, (b) and (c) ? Have any of the obser-
vations made on milk digestion any hygienic sig-
nificance ?

(17) The di fusibility of the products of the artificial
digestion of proteids.

From the products of digestion in experiments
(16-b) digested milk, (15-a) digested gelatin, (15-b)
digested bread, and (12 d) digested egg albumun, fill
four dialyzers — first neutralizing the acid with sodic
carbonate. After 12 24 hours, test the diffusate for
peptone. Why neutralize the liquid before filling the
dialyzer ?

Have all of these indiffusible proteids been wholly
or in part changed to diffusible peptones by the action
of the artif. gast. juice?

XLI. The properties of fats.

/. Materials. — Olive oil; cream; butter; beef tallow; lard;

adipose tissue; cotton seed oil.
2. Experiments and Observations.

(1) The osmic acid test. — Place in test tubes a small
amount of each of the above food stuffs; add to each a
few cubic centimeters of osmic acid. A characteristic
reaction takes place, the result of which is a deep
brown coloration of the fat. If the conditions are
favorable the stain deepens into a sepia black. The
cream and the adipose tissue have proteid admixtures;
note the variation of the reaction.

(2) The solubility of fats and oils. — Prepare three tubes
each of olive oil, of cream, and of tallow; treat each
material with absolute alcohol, with ether and with
chloroform. It will be found that all of these re-
agents are solvents of fats and oils. The alcohol,
however, dissolves very much more of the oil or fat
when warm than when cold, as may be demonstrated
by making the alcoholic solution with the tube im-
mersed in boiling water; after the alcohol seems to
have reached the limit of solution at that temperature,
immerse the tube in cold water. A large part of the
dissolved oil instantly separates out, but will readily
redissolve on again immersing the tube in the boiling
water.

(3) The saponification of fats and oils.

(a} To about 2 c. c. of olive oil in a test tube add 1-2

* volumes of a 25% solution of sodic hydrate. Shake

the mixture vigorously; it is evident that a chemical

reaction is in progress. The fat is undergoing the

182

DIGESTION AND ABSORPTION. 183

process of saponification. A complete and typical
saponification requires a more careful apportion-
ment of the amount of oil and of alkali used and an
application of heat.

(£) Repeat the experiment substituting a 25% solu-
tion of potassic hydrate. The result is similar.

(c) What is the chemical formula of palmitin? Of
stearin? Of olein ?

(d) What is the chemical formula of palmitic acid? Of
stearic acid ? Of oleic acid ?

(e) Write generalized formulae for each of these acids.

(3) Write the reaction which takes place in saponifica-
tion of palmitin; of olein. Note the ready solubil-
ity of the products of this reaction in water.

(4) To a solution of soap add any aqueous solution of a
calcium salt soluble in water, e. g., calcium chloride —
a curdy white precipitate separates out. Write the
formula of the reaction.

May the reaction have any relation to hygiene or
therapeutics ?

(5) The emulsification of oils. — Gould defines an emulsion
as "water or other liquid in which oil in minute sub-
division of its particles is suspended." One may add,
more or less permanently suspended. For, if one shake
together vigorously 2 c. c. of oil with an equal amount
of water in a test tube he is able to bring about a
minute subdivision and temporary suspension of the
oil in the water. While the oil is in this temporary
physical condition it has the white color typical of
emulsions in general. In a few minutes, however,
the particles, as they rise to the top of the liquid
coalesce into minute globules; then into larger and
larger globules and finally into a homogeneous, super-
natant oil-layer.

184 LABOR A TOR Y G U1DE IN PHYSIO LOG Y.

(a) Add to the mixture above described 2 or 3 c. c. of
strained egg albumin; shake vigorously. One ob-
serves the same minute subdivision of the particles,
but they show no tendency to coalesce on standing;
the suspension is "more or less permanent."

Why do not the particles coalesce? In what
respects is this emulsion unlike milk ?

(b) To 2 c. c. of olive oil add 2 c. c. of sirupy solution
of any gum, e. £-., gum acacia; shake the mixture
thoroughly. An emulsion will be formed. What
characteristics has this emulsion in common with
emulsion (a) ?

{c") To 5 c. c. of cotton seed oil containing a little free
fatty acid add 10 drops of strong sodium carbonate
solution and shake. A good stable emulsion is
made in this way. [Long's Chemical Physiology,
p. 63.]

In what way is this emulsion different from those

which precede ? Which one of the emulsions given

above is most like the emulsions formed in the small

intestine ?

(*/) What matters present in the small intestine tend

to promote emulsification of fats ?

(G) The di fusibility of I at s or their derivatives or modifica-
tions.

Fill five dialyzers as follows:
(a) Milk.

(£) Solution of soap.
(e} 10% glycerine.
(</) Emulsion (5-a).
(e~] Emulsion (5-c).

Complete the observations on the following day, deter
mining what derivations or modifications of fat or oil are
diffusible. How may the presence of soap in the dif-
fusate be determined ?

XLI1. Intestinal digestion.

/. Materials. — 2 pig pancreases; 200 c. c. of pig or ox

bile.
2. Preparation.

(1) Aqueous pancreatic extract (a).
(a) Free a pig pancreas of fat.
,(<£) Grind it in a meat hasher.

(V) Extract with water kept at a temperature of 25°
to 28° C.

(d) After two hours strain through linen and filter
through absorbent cotton.

( 2 ) Glycerin extract of the pancreatic ferments,
(a) After freeing the gland of fat, grind it.
(/£) Place it in two volumes of absolute alcohol for two

days.
(V) Drain off the alcohol and transfer to 2 volumes of

pure glycerin.
(</) After one week press out the glycerin, which has

extracted the ferments.

This glycerin extract will keep indefinitely. To

make artificial pancreatic juice proceed as follows:

(e) To 1 volume of the glycerin extract add 5 or 6
volumes of water and sufficient sodium carbonate
solution to give the mixture a distinctly alkaline
reaction.

(3.) Preliminary experiments on bile. — This secretion may

be easily procured from the slaughter house at almost

any time in the year, whereas the gastric juice and

pancreatic juice may only be obtained by resort to

186

186 LABORATORY GUIDE IN PHYSIOLOGY.

operative procedures not properly in the field of this

chapter.*

O) To diluted bile add dilute acetic acid. The
copious yellow precipitate is mucin.

(£) To diluted bile add absolute alcohol; mucin is
precipitated; filter. To one portion of filtrate add
HC1. The yellow precipitate is glycocholic acid.

"To the other portion of the filtrate add lead
acetate, which throws down lead glycocholate.
Remove this by filtration, and to the filtrate add
solution of basic lead acetate, which gives a further
precipitation of lead taurocholate." — [Chemical
Physiology, Long, p. 119.]

(/) Gmeliri1 s test for bile pigments. — To a few cubic
centimeters of strong nitric acid in a test tube care-
fully add dilute bile. At the junction of the liquids
a play of colors, green, blue, violet, red and yellow,
will be noted; the green being next to the bile and
the yellow next to the acid. This delicate and most
reliable test may be applied to any liquid suspected
of containing bile.

(d) The reaction of bile is found to be distinctly

alkaline.
j. Experiments and Observations.

a. The action of pancre^iti.: juice upon foods.

(1) To raw or cooked starch add in one beaker
aqueous extract of pancreas (a); in another add
artificial pancreatic juice (b); place the mixtures in
the incubator; after a short time test for reducing
sugar.

*For description of operationsfor the establishment of gastric fistulas,
bilary fistulas and pancreatic fistulas, see Hand-book for Physiological
Laboratory, Sanderson, pp. 475-517.

•D-IGESTION AND ABSORPTION. 187

Pancreatic juice contains an amylolytic ferment.

(2) Subject fibrin to the action of both of the pancre-
atic preparations.

Pancreatic juice contains a proteolytic ferment.

(3) Boil fresh milk and mix it with an equal bulk of
the aqueous extract of pancreas and put the mixture
into the incubator. Put also into the incubator
boiled milk diluted with an equal volume of distilled
water. The milk which is mixed with pancreatic
juice will curdle much sooner than the other.

Pancreatic juice contains a milk curdling ferment.

(4) Mix 5 or 6 c. c. of neutral olive oil with an equal
volume of aqueous extract of pancreas; shake the
mixture vigorously.

No emulsion is formed. Place one-half of the
mixture in the incubator. After a few hours any
undigested oil may be emulsionized on shaking, or
fresh oil may be emulsified. Explain.

(5) To the second part of the mixture add 3 c. c. bile;
shake the mixture vigorously. A good emulsion is
formed. How is this emulsion formed? What
factor of an emulsion does the bile add ? What is
the relation of experiment (5) to experiment (4)?

Pancreatic juice contains a fat-splitting ferment
whose action liberates fatty acids.

(6) To starch paste add several volumes of dilute
bile. Result?

^7) To fibrin add dilute bile. Result?

(8) To oil which contains free fatty acid add bile;
shake the mixture vigorously; Result?

(9) To neutral oil add bile; shake the mixture vigor-
ously. What is the result? Allow the mixture to
stand in the incubator. After several hours shake
the mixture.

188 LABORATORY GUIDE IN PHYSIOLOGY.

Is an emulsion formed?

(10) Summarize the results of the foregoing experi-
ments, formulating a series of conclusions regarding
the action of pancreatic juice; the action of bile and
their combined action on each class of food.

XLIII. Absorption.

Physiologists have entertained the hope that all the
phenomena of absorption of diffusible substances could
be eventually explained by the laws of physics. That
hope has practically given place to the conviction that
however important it may be to the animal economy to
produce, in its digestive processes, diffusible products,
these products do not pass through the epithelial lining
of the alimentary tract at the rate or in the propoitions
that would be observed in the dialyzer. This need oc-
casion no surprise; in one case we have to deal with
living, active cells, in the other with dead tissue.

Living ceils of muscle-tissue or of gland-tissue have the
power of selecting from the tissue plasma such materials as
are needed for the replenishment of their substance. Not
only does the animal select what shall be taken into the
alimentary tract but the epithelial lining of that tract
seems to select what shall be absorbed and to absorb it ac-
cording to laws which conform only in a most general way
or which may not conform at all to the laws of osmosis.
In order, however, to understand the current literature on
the subject of absorption it is necessary to be familiar with
the terminology and laws of osmosis and dialysis. To
that end the student may profitably perform for himself a
few simple experiments preliminary to more complex ones
which the demonstrator may suggest or may perform for
the class.

/. Appliances and Materials. — Six dialyzers complete, in-
cluding outer receptacles and supports; 2 or 3, 100 c. c.,

189

190 LABORATORY GUIDE IN PHYSIOLOGY.

evaporating dishes; distilled water; sodium chloride;

alcohol; egg; mercury manometer.
2. Preparation.

(1.) Fit four of the dialyzers with membrane of pig-
bladder. The bladders should be carefully selected as
to uniformity in thickness, and should be soaked for
an hour or more in water before being stretched upon
the dialyzers. The membrane should be stretched as
nearly uniform as possible upon the four dialyzers.
Fit one dialyzer with parchment paper such as is fre-
quently used for this purpose. Furnish one dialyzer
with some other animal membrane e. g., a cow's blad-
der or a rabbit's caecum.

(2) Prepare dilute egg-albumin by adding to strained
undiluted albumin about 9 volumes of distilled water.

j. Experiments and Observations.

(1) Salt, in saturated aqueous solution may be put
into a dialyzer. So adjust the apparatus that the
water in the outer receptacle shall be on a level
with the solution in the vertical tube of the dialyzer.
How much does the water rise in the tube ? What
degree of positive pressure within the dialyzer does
that represent? How much pressure per unit area,
measured with a mercury manometer will it be nec-
essary to produce within the dialyzer to stop the in-
crease of the volume of its contents? {Endosmotic
pressure.'} Will that amount of pressure prohibit
diffusion between the liquids?

(2) After osmosis has been allowed to take its unim-
peded course for, say, one hour, starting with a 20 per
cent, solution of NaCl within and distilled water with-
out the dialyzer, note the height of the water in the
tube and compute the number of grammes of water
which have entered the dialyzer. Determine how

DIGESTION AND ABSORPTION. 191

much NaCl has passed out of the dialyzer. An easy
and sufficiently accurate method is to evaporate to
dryness all, or a known proportion of the liquid in
the outer receptacle, and weigh the dry salt remain-
ing. How many grammes of water enterthe dial-
yzer for each gramme of salt that leaves ? (Endos-
motic equivalent.^

(3) Is the endosmotic equivalent constant for salt and
water? (a) Is it the same for different strengths
of the salt solution, i. e., for 10% or 1% as for 20%?
(£) Is it the same for two hours or four hours as
for one hour ?

(4) Fill with 10% glucose three dialyzers provided with
three different kinds of membrane. Does osmosis
take place at the same rate in all three dialyzers ?
What is the endosmotic equivalent for glucose?

(5) What is the endosmotic equivalent for dilute egg
albumin? When albumin is injected into the colon
it is readily absorbed as albumin, there being no
digestive changes in it.

(6) Fill a dialyzer with equal parts of 10% glucose
and 10% NaCl. At the end of a convenient period,
2-6 hours, determine whether these substances have
diffused according to their own endosmotic equiva-
lents, i. e., independent of each other, or have they
been influenced the one by the other?

(7) Fill a dialyzer with alcohol. Which way does the
osmotic current flow?

(8) In the above experiments water has uniformly
passed into the dialyzer.* If pure water be taken
into an empty stomach would one expect it to be
readily absorbed ?|

*If alcohol be taken into the stomach it is not diluted with water
drawn from the tissue, but it is rapidly absorbed.

fWater is absorbed slightly, if at all, through the walls of the
stomach.

F. VISION.

XLIV. Dissection of the appendages of the eye.

1. Appliances. — Fresh ox-eyes, including as much of the
appendages as possible; physiological operating case;
dissecting boards and pins, such as used for frogs; dog,
cat or rabbit; bone forceps; injection mass; syringe.

2. Dissection. •- Follow Gray; or Quain, Vol. III., Part III.
(1) Before fixing the eye to the board make a careful

examination of the organ.

(0) Trace the conjunctiva, describing its ocular and its
palpebral portions. Describe the plica semilunaris
and the caruncula. Do these two tissues have the
same relative size in man and the ox? Find and
describe \hepuncta lachrymalia. Find arid describe
the openings of the lachrymal ducts. How many are
there? Enumerate the conjunctival landmarks
which determine the inner from the outer side of the
eye. Enumerate the conjunctival landmarks which
determine the superior aspect of the eye. Is the
eye which you have a right or a left one ?

(<£) Observe the appendages of the eye. Do you find

a remnant of the levator palpebrcz muscle ? Find

the tarsal cartilages and the remnant of the orbicularis

palpebrarium muscle. Find openings of the meibomian

192

VISION, 193

and of sebaceous glands. Find and describe the
lachrymal gland as to location and size.

Find the cut-off ends of the recti and oblique mus-
cles of the eye.

Describe the location of the optic nerve with
respect to the cornea.

What traces have you found of the capsule of
Tenon ?

Enumerate the new landmarks which determine
the superior aspect of the eye; the internal aspect.
Are these extra landmarks sufficient to determine
whether the eye which you have is a right or a
left one?

(2) Fix the eye to the board with corneal surface down,
pinning down flaps of the conjunctiva for support.

(a) Dissect oat the four recti and the two oblique mus-
cles. One will find in the ox a rather heavy retractor
muscle in close relation to the optic nerve. This
should be left undissected until the other muscles
are demonstrated.

(b} Trace further the intricate loculi of the capsule of
Tenon.

(c~) Carefully separate from the eyeball all connective
and adipose tissue.

(3) Remove the retractor muscle of the ox eye in
process of dissection, taking care not to sever any im-
portant blood vessels or nerves.

(0) Locate and describe the vena vorticostz. How

many are there?
(£) Find the anterior ciliary arteries. How many can

be found ?

Describe their relation to the tendons of insertion

of the recti muscles. What tissues do they supply?
(c) Find the two long ciliary arteries.

194 LABOR A TOR Y G UIDE IN PHYSIOLOG Y.

(dT) Locate and enumerate the short posterior ciliary

arteries,
(e) Dissect out the ciliary nerves. What tissue do

they supply?

(4) Let one number of the division dissect, for demon-
stration, the orbital muscles of a dog, cat or rabbit.
To facilitate the dissection fix the animal with dorsum
up, and remove with bone forceps the upper and
outer walls of the orbit.

(5) Let one member of the division inject, with carmine
or vermilion mass, the internal carotid of a dog, cat
or rabbit, and dissect out for demonstration the ocular
branches of the ophthalmic artery.

XLV. Dissection of the eyeball.

/. Appliances. — The eyes, already partly dissected, which
have been kept in an ice chest; physiological operat-
ing case.

2. Dissection. — a. Anterior dissection: Fix the eye to the
board, cornea upward, using the dissected muscles as
guys.

(1) Describe the cornea as seen from the front. Does
the radius of curvature of the lateral meridian seem
to be the same as the radius of curvature of the ver-
tical meridian? With heavy scissors remove the cor-
nea, leaving a margin of one-eighth inch anterior to
its junction with the iris.

Examine the cut surface of the cornea with a lens.

(2) Through the elliptical opening thus made examine
the iris as to texture, etc.

(3) Holding the margin of the cornea with strong for-
ceps, carefully dissect the sclerotic coat from the
choroid for about one eighth of an inch posterior to
the angle of the anterior chamber. Locate four points
in the margin from which incisions may be made
antero-posteriorly between the insertions of the recti
muscles. From the points located make the incisions
posteriorly as far as the equator of the eyeball. Dis-
sect each flap from the underlying choroid; remove
the pins which fix the recti muscles, and through
traction draw the flaps back; fix.

(0) Make a drawing of the choroid with its irideal
and ciliary portions thus exposed.
195

196 LAB OKA TOR Y G UWE LV PHYSIOL OGY.

(<£) Locate, if possible, the course and distribution of
nerves and blood vessels.

(4) With fine forceps grasp the margin of the iris and
with fine scissors cut out a sector limited posteriorly
by the ciliary body.

(0) Study the boundaries of the posterior chamber.
(£) Find fibers of the suspensory ligament,
(c) Describe the anterior surface or the ciliary proc-
esses.

(5) Make a circular incision with small scissors severing
the choroid and retina at about the line of the ora
serrata. Lift off from the dense vitreous humor the
whole ciliary apparatus and lens, place them, anterior
surface downward, upon a plate.

(a) Describe the posterior aspect of the ciliary proc-
esses.

(£) Describe the lens minutely, as viewed externally.
(<r) Make a section of the lens, describe its appearance.
Is the capsule discernible ?

(6) Describe the retina as seen through the vitreous
humor.

(#) Locate the entrance of the optic nerve.

(b) Can the fovea centralis be located ?

(V) Can the course of the retinal vessels be followed ?
2. b. Posterior dissection.

(7) Let one member of the division remove the poste-
rior half of the sclerotic coat, after first fixing the eye
with cornea downward, using the recti muscles, in
this case also, for guys.

(#) Note the vena vorticosa.

(b'} Follow the ciliary nerves from their entrance into

the eyeball, along their course between the sclerotic

and choroid coats.

VISION. 197

(V) Do you find the long ciliary arteries, or the poste-
rior ciliary arteries ?

(8) Remove the choroid carefully.

(a) Note the character of its tissue, its vascularity

and its rich pigmentation.
(<£) Describe the retina as seen from this direction. Its

pigmented layer has probably come away with the

choroid.

(9) Remove the posterior half of the vitreous body
together with the retina.

(#) Make a drawing of the posterior surface of the lens,
suspensory ligaments and ciliary processes as shown
posteriorly.

(10) Remove the remnant of the vitreous body; sever
the fibers of the suspensory light; lift out the lens.
(0) Describe the ciliary body and the iris thus held in

their normal relations by the supporting sclera.

XLVI. Physiological optics, a. Determination of indices

of refraction of water and of glass, b. Determin=

at ion of focal distance of lenses, c. Verifi=

cation of formula : -j- -f ,v = p. d. A

simple dioptric system.

a. Determination of the indices of refraction of water
and of glass.

1. Appliances. — Apparatus for determining the index of re-
fraction; a deep flat-bottomed water pan; a cube ot
glass 4-6 cm. in linear dimensions and polished on at
least two opposite sides. The two polished sides must
be absolutely parallel, whether the other sides are par-
allel makes no difference; centimeter rule and dividers.

2. Preparation. — A very convenient and sufficiently exact
apparatus for making the required determination may
be readily made as follows:

(1) Take a carpenter's tri-square, constructed wholly of
iron; from the angle x (Fig. 26), where the gradu-
ated limb joins the body, measure off centimeters upon
the inner surface of the body and cut them in with a
file.

(2) Locate on the inner edge of the graduated limb any
point, as y, 6 to 9 centimeters from the point x.
With files remove about ^ centimeter of the edge as
indicated in the figure, cutting deeply at z, so as to
leave a slender point at y as indicated.

(3) Drill a hole in the inner surface of the body at o;
fit and drive a heavy brass or iron wire into this;
sharpen the upper end of the wire. The length of the
wire above the body must be two or three centimeters

198

VISION.

199

greater than the distance x y. Bend the point over so
that the distance o p shall equal x y.

Experiments and Observations. — Place the instrument in
the water pan; fill the pan, so adjusting it that both
points p and y will just touch the water, or rather almost
touch the water, for the surface of the water at y must
be absolutely plane. If the point touch it the surface
will not be plane.

FIG. 26.

FIG. 26.

A contrivance for use in determining the refractive indices of
water and of glass.

(1) O) Bring a small rule (r) into position and clamp
it to the limb of the instrument by means of heavy
serre-fine forceps. So adjust the rule that as one
sights along its upper edge the points a, y and 3 seem
to lie in one and the same straight line. Lift the ap-

200 LAB OR A TOR Y G U2DE IN PHYSIOLOG Y.

paratus out of the water and lay it upon the table,

taking care not to disturb the adjustment.

(£) With dividers measure the distance from the point
y to line 3. This is the radius. Determine the point
where the circumference would cut the upper surface
of the rule, say point b.

(Y) From this point determine the perpendicular dis-
tance to the edge of the limb at c.

(d) The line c y x is a normal to the surface of the water
at the point y. The angle i is the angle of incidence;
the angle r is the angle of refraction. Imagine a circle
whose center is at y and whose circumference passes
through b and 3. The line b c is the sine of the angle
of incidence. The line x 3 is the sine of the angle
of refraction.

(<?) What is the ratio of sin i to sin r, or —^ = ?

(2) In the same manner determine the ratio of the sines
of these angles when the rule is so adjusted as to
bring a'y 6 in apparently one straight line. What is
the ratio of sin i' to sin r'? or —-£ = ?

(3) If the instrument has been carefully constructed
and if the determination has been made with suffi-
cient care, the ratios will be found to be practically

equal, i. e., ?lLJ— 5lD_L . What is the constant ratio in
•*• sin r sin r

the case of water? This constant ratio is called the
index of refraction, and is conventionally represented
by fi.
For water,/* = |^ = i= 1.333.

(4) To determine the index of refraction of glass pro-
ceed as in the case of water. Set the instrument upon
the table; the block of glass may be placed upon the
body of the instrument, the polished surfaces be-
ing placed above and below. If the distance be-

VISION. 201

tween the polished surfaces is not equal to x y, a point
y' may be located on the upper surface near the edge
of the glass block by making a dot with ink where the
line y x cuts the upper surface of the block. This line
is the normal.

What is the index of refraction of the glass block
furnished by the demonstrator?
b. The determination of the focal distance of lenses.

By means of a spherometer the radius of curvature (r)
of a lens may be determined.*

If one knows the radius of curvature of a lens and the
index of refraction of the material of which the lens is
made he may compute the focal distance by using the
formula (1) F = — for piano convex lenses, or (2) F=^7 — TT
for bi-convex lenses. But there is an easier and more
direct method of determining the focal distance of a lens;
namely, by direct experiment.

/. Appliances. — An instrument such as is used in physical
laboratories for the same purpose or such a one as is
described under 2; several lenses ranging from 5 cm. to
50 cm. in focal distance.

2. Preparation. — A most satisfactory apparatus for this
purpose may be made by any student or demonstrator in
three or four hours. From thin pine boards construct a
simple box about 10 cm. square in cross section by 50
cm. in length. One end of the box should be closed
with a tightly stretched oiled paper for a screen, while
the other end may be closed with the same material of
which the rest of the box consists, the center of the end
having a circular aperture one or two centimeters in

12 R

*[r=a!ir~r~a • when a=spherometer reading, and l=the length of
one side of the equilateral triangle determined by<*ffe7 legs ,o|- |bf</'?^
spherometer.] X/\^ \\\\\U// ' 0

202

LAB OR A TOR Y G UIDE IN PH YSIOL O G V.

diameter. The bottom of the box is constructed as fol-
lows: (See Fig. 27.) Cut through the middle of the bot
torn a slot about 0.5 cm. wide and 45 cm. long. Make a
lens carrier of wood as indicated in the figure (Fig. 27,
C. & C'.). Tho saw groove in the top of the carrier
serves to hold the lens. If, however, the lenses to be
used in the apparatus be not provided with rims and

FIG. 27.

FIG. 27. Showing parts of apparatus for determining the focal distance
of lenses. For construction of the apparatus, see XLVI=b=2.

rings the demonstrator can readily contrive a means of
holding them in place. In any case they should be so
held that the plane of the lens is perpendicular to the
axis of the box, and that the center of the lens (o)
is virtually over a fixed line (o') drawn transverse to the

VISION. 203

axis of the lens carrier. The screws S and S' serve the
double purpose of protecting the projection (p) from
splitting off and of affording handles by which the car-
rier may be slipped along the groove. Along one edge
of the groove on the outer surface of the bottom make a
centimeter scale carefully with a sharp hard lead pencil.
The scale should have its zero point in the plane of the
screen. At the point D fix a shaft (such a one as shown in
Fig. 27, D'), which shall extend several centimeters below
the bottom and set perpendicular to it. The shaft may
be fixed in a universal clamp-holder and the whole sup-
ported upon a heavy support. By adjusting the clamp-
holder the apparatus may be directed toward any desired
object. Make a cover to the box, and blacken the whole
inside.

3. Observations. — Fix a lens in place; close the box; direct
its axis toward some well illuminated distant object;
grasp the handles of the lens carrier and move it to a
position which gives upon the screen a sharply defined
image of the object in the field. One has only to read
the position of the transverse line of the carrier on the
centimeter scale to have the focal distance of the lens;
i. e., the distance at which parallel rays are focused,
c. Verification of the formula 1 -f 1 = i.

A second method of determining the focal distance of a
lens depends upon the relation of the distances of the conju-
gate foci to the general focal distance: This relation may be
expressed thus: The sum of the reciprocals of the conjugate
foci is equal to the reciprocal of the focal distance. \-\~\ — \>
Now when a lens throws upon a screen the image of an
object it is evident that the distance of the object (o)
represents one and the distance of the image (i) represents
the other of these conjugate focal distances; so one may

204

LABORATORY GUIDE IN PHYSIOLOGY.

say: The reciprocal of the distance of the object from the lens
(— ) plus the reciprocal of the distance of the image (1)
equals the reciprocal of the general focal distance ^ : thus

(-i--[~-f — -p )• This formula enables one to compute
the focal distance after first determining by experiment the
values o and i. Inasmuch as the student has already deter-
mined the focal distance (F) and may not have made the
rather extended computation incident to the derivation of
the above most valuable formula it is considered that the
most profitable course to pursue at this point is the verifi-
cation of the formula.

rprrT

FIG. 28.

FIG. 28. An apparatus for determining the conjugate focal distance
For description, see c=l.

/. Apparatus. — To that end one may construct a simple
apparatus (Fig. 28). For the determination of the focal
distance it is usual to have both object and lens mova-
ble. For our purpose this may be dispensed with as it
lends little to the reliability of the result and detracts
much from the simplicity of the apparatus. Upon a
thin board as a base fix an upright piece near one end
of the base, whose inner surface may be painted white
and serve as a screen (S). Near the other end fix a

VISION. 205

second upright piece having in its center a large hole.
Over this hole, on the inner surface of the upright, fix a
sheet of lead or of copper in which some figure has been
cut (o). Construct a lens carrier (c), whose pointer (p)
will indicate upon the scale (s') the position of the center
of the lens. The use of the instrument will be some-
what facilitated if the distance between the surface of
the screen and the surface of the lead or copper be pur-
posely made exactly 100 cm. In addition to the above
apparatus one needs the lenses whose focal distance he
has determined. He needs also a lamp or candle to
place behind the metallic screen at e.

2. Experiments and Observations, — Place a light behind the
metallic screen; it shines through the figure cut through
the screen. This figure is the object.

(1) (a} Place a lens in the carrier and so adjust it that
the plane which it represents is perpendicular to the
axis of the instrument and its center is in the same
perpendicular plane with the index (p) of the carrier.
(£) Slide the carrier along the base until the object is

sharply focused upon the screen.

(c) Read from the scale the distance of the lens from
the image (i). If the instrument is made just 100 cm.
between screen and object, then the difference be-
tween 100 and the reading will be the distance of the
lens from the object. Is the image erect or inverted?
Explain the phenomenon, drawing geometric figure.

(2) Study the general formula:

(•) S+?4

(£) F=^pj; but o+i=rlOO; therefore
(^ 100 F = 0 i.
From this form of the statement it is evident that the

206 LAB OR A TOR Y G UIDE IN PHYSIO LOG Y.

lens will throw a distinct image in either one of two
positions. Demonstrate it experimentally.
(3) Determine o and i for each lens and substituting
their values and that of F previously determined,
verify the equation. A moderate deviation may be
expected, due to errors in the apparatus and in the
observations,
(j) Problems.

The value of the formula -^H-y = ^ is so great and
its application so frequent that the student should
thoroughly familiarize himself with the properties
of lenses as revealed in this formula.
Solve the following problems:

(1) When the object is twice the focal distance,
what is the distance of the image ?

(2) When the distance of the object is greater
than 2F, how does the distance of the image com-
pare with 2F ?

(3) When the object is at a very great distance
(o= oo) at what distance will the image be formed?

(4) What is the maximum focal distance that
may be determined or verified with the above de-
scribed apparatus ? Discuss methodically.

d. A simple dioptric system.

The simplest dioptric system is one in which the ray
passes from one medium into a second medium of
different refractive index, the surface of separation
of the two media being a spherical surface. In the
accompanying figure (Fig. 29 A) the spherical sur-
face s'sps" separates the medium M, whose re-
fractive index is 1.000, from the medium M', whose
refractive index is 1.500.

Note the following cardinal points of a simple
dioptric system.

VISION.

207

The center of curvature of the spherical surface
(n) in the nodal point.

That radius which is the center of symmetry of
the dioptric system (e. g., n— p.) is called the princi-
pal axis of the system. In this axis lie the first and
second principal foci, f and f respectively. The point
where the optical axis cuts the spherical surface
(p) is called the principal point. The plane tangent
to the spherical surface at this point is the principal

FIG. 29.

FIG. 29. A. Showing the cardinal points of a simple dioptric sys-
tem, n, nodal point; R p n, principal axis; p, principal point; f, f ,
principal foci.

FIG. 29. B. Showing the relation of the visual angle, v and the
size of object and image to values p and n.

plane. Planes perpendicular to the optical axis at
f and f are called the first and second principal focal
planes respectively.

Problem. Given the radius of curvature and the
index of refraction to locate upon the principal axis
the principal foci.

Neumann has given the following construction:

208 LABOR A TOR Y G UIDE IN PHYSIOL OGY.

(1) Erect at n and p perpendiculars to the principal
axis.

(2) Lay off, upon each, the two indices of refrac-
tion of the two media, measured from the origin
of each perpendicular, in the same linear units
used in measuring the radius. In the figure let
n c and p d represent the index of refraction of
the medium M, and n a and p b the index of re-
fraction of medium M'. The continuation of line
a d cuts the principal axis in the point f, the first
principal focus, while the line b c cuts it in the
point f, the second principal focus. The geo-
metrical figure shows the following important
properties of the dioptric system:

I. The distance from the first principal focus to
the principal point equals the distance from the
second principal focus to the nodal point.

(1) Mathematically expressed: pf=nf'.

II. The ratio of the second focal distance (pf) to
the first (pf) is equal to the ratio of the index
of refraction of the second medium (M') to that
of the first (M).*

(2) Mathematically expressed: — pf: p{'=/j.'. //.
But p£ = nf; substitute this value in the second
equation, —

(3) .... nf: pi'—p.: //; assume medium M to have
an index of refraction /*=!.

(4) nf':pf'=l:/,'.

(5) pf' = nf'X/j-'; or more concisely

(5') p =//'n. (See p and n in Fig. 29. A.)
This derived property of the construction merits
a separate formulation.

*Ref faction and Accommodation of the Eye. — Landolt, p. 85.

VISION. 209

III. The distance from the second principal focus
to the principal point equals the product of the
distance from that focus to nodal point multi-
plied by the index of refraction of the second
medium (p = #'n).

Note in addition the following facts regarding
the effect of such a dioptric system upon light.

1st. The ray rs, meeting the spherical surface
perpendicularly, will not be refracted at s, but
will pass on through the nodal point.

2d. The ray r's', parallel to the principal axis in
the first medium is refracted at the spherical sur-
face and cuts the principal axis at P, — it passes
through the second principal focus.

3d. The ray r"s", cutting the principal axis at f
in the first medium (M), is refracted at s" and
traverses the second medium parallel to the prin-
cipal axis.

XLVII. Physiological optics, applied, a. The application

of the laws of refraction to the mammalian eye.

b. To locate in the mammalian eye

the cardinal points of the sim=

pie dioptric system.

The dissection of the ox eye revealed several refractive
media (cornea, aqueous humor, lens, and vitreous humor)
and several curved surfaces bounding these media. In
determining the focal distance of a lens one must know the
radius of curvature and the refractive index. In determin-
ing the focal distance of a system of refractive media and
surfaces one must know (1) the radius of curvature of each
surface, (2) the refractive index of each medium, and (3)
the location of their cardinal points upon the principal
axis of the system.

The mammalian eye receives its light through media
and surfaces, as indicated in the following table:

MEDIA.

INDEX OF
REFRACTION.

SURFACE.

RADIUS.

Air.

1.000

Tear Film.
Cornea.
Aq Humor.
Lens.

1.3365
13367
1 3365
1 4371

Over Ant. Surf. Cornea.
Ant. Corneal Surface.
Post. Corueal Surface
Ant. Surface.

7. 839+ cm.
7. 8^9+ cm.
7.829— cm.
100cm.

Vit. Humor.

1.3365

Post. Surface.

6.0 cm

This array of media and surfaces would seem to make
a problem too intricate to solve with the means at our dis-
posal. Notice, first that the tear film and the ant. and
post, corneal surfaces have the same radius of curvature;

210

VISION. 211

i.e., though curved surfaces they are parallel and form a
case under the following theorem: "If a ray pass from
any medium through a denser medium which is bounded
by two parallel planes it emerges from the denser medium
in a line parallel to its course before entering that
medium." It is customary at this point to take the ante-
rior surface of the cornea as the first refractive surface
and IL— 1.3365.

Notice that the index of refraction of the aqueous humor
and vitreous humor are the same. It is now evident that
we have to deal with three media [air, aqueous or vitreous
humor, and lens], with three surfaces [ant. corneal surface,
ant. and post, lens surface], whose radii are 7.829, 6 and
10 respectively. But even this great step toward simpli-
fying the problem leaves us with a long road before us un-
less we can find a short cut. " It has been shown mathe-
matically that a complex optical system consisting of sev-
eral surfaces and media, centered on a common optical axis,
may be treated as if it consisted of two surfaces only."
[Text-book of Physiology — Foster, 1891 — vol. IV., pg. 9.]
The location of these surfaces and the cardinal points are
given as follows by Landolt :

A. The normal eye.

The point r (Fig. 30.) where the principal axis cuts the
cornea is 22.8237 mm. from the second principal focus f
(the retina) ; c, the center of curvature of the cornea; s, the
point where the optical axis cuts the anterior surface of
the lens, is 3.6 mm. from r, the point where the optical
axis cuts the posterior surface of the lens 7.2 mm. from
r; 1, the center of curvature of ant. surface of lens; 1',
the center of curvature of posterior surface of lens.

B. The accurate mathematical reduction.

The reduction referred to in the text above is represented
by the two refractive surfaces with nodal points n and n'

212

LABORATORY GUIDE IN PHYSIOLOGY.

radii of 5.215 mm. each and cutting the optical axis at p
and p', located 1.7532 mm. and 2. 11 mm. respectively
from r.
C. The final approximate reduction.

Note that p is less than 0.36 mm. from p'. One may as-
sume one nodal point N, and one refracting surface between
the computed ones, cutting the principal axis at P, and
introduce an error too slight to consider. But this brings

FIG. 30.

FIG. 30. Showing the mathematical features of the reduced eye.
For detailed explanation of the figure see text A, B and C. The figure
is multiplied by five in its linear dimensions. [Errata : For 6 cm read
3cm.]

us back to the simplest possible dioptric system, already
described on pg. 206 et. seq.

All of the properties of that simple dioptric system
are possessed by the normal mammalian eye.
b. To locate, experimentally in the mammalian eye, the

cardinal points of the simple dioptric system.
I. Appliances and Materials. — A white rabbit; support with
universal clamp-holder and small cork-lined burette

VISION. 213

clamps; meter stick or tape; steel or ivory rule, with
millimeters subdivided if possible, hand lens, fine divid-
ers with needle points; bone forceps; NaCl 0.6%; camel's
hair pencil; absorbent cotton.

2. Preparation. — (1) Mathematical. (See Fig. 29 B.)
We wish first to locate the nodal point in a rabbit's eye.
Represent the distance from the retina to the nodal
point by n, the distance from the object to the image by
d, the vertical dimension of the object by o, the same
dimension of the image by i. From the similar right
triangles of the figure one may write:

(1) o: i = d — n: n;

(2) on = id — in;

«*=&

Jnder the conditions of the experiment i is so small
compared with o that it may be ignored in the denomi-
nator, and we may use the equation:

(2) Arrangement of Apparatus.

(a) A convenient object to observe is a well-illumi-
nated window, or one sash of a window; measure
the vertical distance between the horizontal strips
of the sash.

(£) Arrange three or four tables end to end in a line
perpendicular to the plane of a window. On the
table lay off from the plane of the window the dis-
tances 4, 4.5, 5, 5.5 and 6 meters.
. Operation.

(1) Remove an eye from the rabbit which had been
chloroformed some time before and suspended by the
anterior limbs.

(2) Dissect from the eye, especially from the posterior

214 LAB OR A TORY G UIDE IN PH YSIOL OGY.

aspect of it, all of the areolar connective tissue, muscle
tissue, etc., down to the glistening smooth sclera.

(3) Wrap around its equator a band of absorbent cot-
ton wet with normal solution.

(4) Fix the eye in the clamp with its axis transverse to
the axis of the clamp, t?king care to exert just enough
pressure to prevent the eye from falling on being
touched, but not enough to distort it.

(5) Fix to the clamp a thread with a bit of lead to serve
as a plumb line.

4. Observations.

(1) Adjust the support so that the eye is directed toward
the object and the image is located approximately
symmetrically about the fovea centralis, and the plumb
line over the mark 4 meters. With the fine dividers
measure in the image the distance between those
points which were chosen as the limits of the object.
The value of this measurement may be read to tenths
of millimeters by laying the divider points upon the
steel rule and reading with the hand lens.

(2) Make similar observations at 4.5 m., 5 m., 5.5 m.,
and 6 m. Each observation should be made three or
four times and the average taken.

(o) Record these averages in a table ruled with columns
for the values d, o, i, n and /.

(4) Calculate for column n the values obtained by sub-
stituting, in the formula n = ^, the values observed in
(1) and (2). What is the value of n ?

(5) Measure the antero-posterior diameter of the eye.
How far anterior to the posterior surface of the sclera
is n located? How far from the surface of the cornea?
How does the ratio of these two quantities differ from
that given above for the human eye?

(6) Locate the position of the principal point or the

VISION. 215

point where the ideal refracting surface of the eye
cuts the optical axis, by applying the formula:

p=/m.

Assuming for /JL the value which it has been calculated
to have in the human eye (1.3365 Landolt, p. 86),
how far is this point posterior to the anterior surface
of the cornea ? How does your result compare with
that for the " reduced human eye? "

(7) Is the image erect or inverted? Explain the phe-
nomenon ?

(8) Move the eye to within one meter of the object.
Note that a fairly clear image may be thrown upon a
posterior segment of the sphere, which is many hun-
dred times the area of the fovea centralis.

(9) If a fine sharp needle be thrust through the eyeball,
following a course perpendicular to the optical axis
and cutting it at n, what relation would this needle
have with the lens ? Would it be tangent to the lens;
would it enter the lens or would it pass free of its pos-
terior surface?

(10) If a similar experiment were performed with refer-
ence to the point p, what relation would the needle
have to the anterior surface of the lens ?

For these experiments the eye may be frozen after
the introduction of the needle and a vertical longi-
tudinal section made.

XLVIII. Accommodation and convergence.

In the above experiment with the excised rabbit's eye
one notices a marked blurring of the image when the eye
is brought near the object. Though the definition of the
image is sharp at 5-6 meters or beyond, at 2 or 3 meters
the outlines are, hazy. The normal living eye is, however,
able to give one the sensation of a clear image at any distance
from several inches to several miles. That there is actually
a sharply defined image upon the retina when the normal
mind has the sensation of such an image there is no doubt.
One knows from his experience with optical instruments
that they must be readjusted for each distance if they are
to yield a sharp image for each distance.

The same thing is true in the case of the organic optical
instruments with which one perceives the form, color and
space relations of the objects of his environment. The
functional adaptation of the visual organs to distance is called
accommodation .
a. Accommodation.
Experiments and Observations.

(1) Take a sharp pointed pencil or similar object in each
hand; hold the upturned points in the line of direct
vision before the eye, one point being about 25 centi-
meters distant from the eye and the other at arm's
length; make the observations with one eye, the other
being closed or screened,
(0) Focus upon the near point. Is the image of the

distant point clear?

(£) Focus upon the distant point. Is the image of
the near point clear?

216

VISION. 217

(V) While the eye is focused steadily upon the near
point bring the distant point slowly up to a position
beside the near point. One of the images is trans
formed from an ill defined one to a clearly defined
one. Which image is it ? Does one note a similar
change in the definition of the image when he
moves the near point out to position beside the dis-
tant point while focusing steadily at the latter?

(d} Sum up the results of the experiment into a con-
cisely formulated statement.
(2) Holding the two points side by side at a distance of

30 centimeters note that the points appear equally

well defined.

(a) Direct the eye steadily at one of the points while
moving the other one nearer to the eye. Note the
number of centimeters which it advances toward the
eye before the outlines become ill-defined. Reverse
the act, moving the point back to its original posi-
tion beside the stationary point, noting that the
image of the receding point remains clear.

(£) Continue to carry it farther from the eye, noting
that after it has been carried beyond the unmoved
focused point a certain distance the outline be-
comes again ill-defined. Note the number of centi-
meters between the two points in this position.

(V) Make a similar experiment, using 50 cm. for
the distance of the stationary point, and note the
centimeters between the points at the limits of
clear definition. In this way one may observe and
measure the depth of focus of the eye.

(//) Is the depth of focus greater at 30 cm. or at
50 cm. ?

(e) Is the depth of focus greater at 1QO meters than at
one meter ? Demonstrate and explain.

LABORATORY GUIDE L\ PHYSIOLOGY.

Determination of the near point or "punctum prox-
imum." Determine the distance from the eye of the
nearest point at which a pencil point or needle may
be perfectly clearly seen. The exact location of the
near point may be more satisfactorily determined if
one look at the object through two holes, 2 mm. apart,
in a card. At this point thepunctum proximum act
of accommodation is brought most actively into play.
Determination of the punctum remotum.

Direct the eye toward some object not less than
six meters away and describe to other members of
the division the minute details of the object, such as
slight irregularities of surface lines or other details.
If an individual is able to convince his comrades that
he can perceive, at this distance the minute details
of objects he must be credited with normal vision.
Inasmuch as he can also see with the usual distinc-
tions more distant objects the punctum remotum is
said to be located at infinity; or, to state it in another
way, the eye is able, with suspended accommodation,
to bring parallel rays to a focus upon the retina.*
(b) It frequently happens that the individual under
observation fails to make out more than the merest
outline of an object 6 meters away. Decrease the
distance until he is able to perceive details seen by
the majority of his comrades. If this distance has
to be decreased to two or three meters the determi-
nation may be made more exact by resorting again
to the needle and punctured card mentioned in (a),
and carrying the needle away until it appears double.

*It must be stated here that this experiment does not make it cer-
tain that the punctum remotum is not beyond infinity! In a subsequent
lesson that point will-foe carried farther. We must be temporarily con-
tent with having it so far.

;0.\- >..'.*

In recording the punctum remotum, write infinity (o» )
for six meters or more and for any distance within
that, record in meters and decimals thereof.

(5) How many meters from the punctum remotum to the
punctum proximum in those cases where the punctum
remotum is less than six meters ?

(6) Observe the pupil closely while the subject directs
the eye from a distant object to a near one. It con-
tracts slightly. On a priori grounds this act of the
iris is advantageous. Showfrom the standpoint of the-
oretical optics why it is advantageous.

(7) Observe from the side that when the act of accom-
modation takes place the iris at the edge of the pupil
not only moves toward the center but advances notice-
ably toward the cornea. What could produce t

(a) If the edge of the iris rests upon the lens capsule
would it not be pushed farther toward the cornea
incident to its contraction toward the center?

If the pupil contracted from a 3 mm. diameter to
a 2 mm. diameter, how much would it be advanced
incident to the normal curvature of the lens. Could
this be detected by the method of observation which
has been employed?

(b) Account for the forward movement of the pupillary
edge of the iris during accommodation.

b. Adaptation of the eye for direction. Convergence.

Just as the eye possesses a mechanism by which it
changes its refractive power for different distances, so it
possesses a mechanism by which it may change the direc
tion of its visual axis from one object to another or may
follow the movements of objects within the range of vision.
I. Monocular fixation. — Let two individuals work together,
one as subject and the other as observer. Let them sit

220 LABORATORY GUIDE IN PHYSIOLOGY.

on opposite sides of the table. Let the subject close or
screen one eye.

(1) Hold any object directly in front of the subject; let
the subject keep his gaze continually fixed upon the
object. Move the object quickly toward the subject's
left, and note the fixation anew of the object in its new
position. What muscle or muscles accomplished this
act of monocular fixation?

(2) Move the object quickly in the opposite direction,
then upward, downward and diagonally, noting the
instantaneous adaption of the eye to the new
direction, recording also the muscle or muscles involved
in each act. Are all the movements apparently equally
ready and exact ?

(3) Bringing the object to a point directly in front, 1 m.
distant, note through how great a lateral movement it
may be carried without inducing any discernible change
in the visual axis of the eye.

(4) Bring the object to the central position and move it
very slowly outward in any direction, noting whether
the changes in the direction of the visual axis are
equally slow and regular.

2. Binocular fixation, convergence.

In the above experiments it was probably noted by both
subject and observer that the closed or screened eye
responded to every movement of the other eye.

(5) With both eyes open and fixed upon an object held
directly in front at a distance of about 1 m., let the
observer move the object quickly, then slowly, right,
left, up, down, and around, and observe the continuous
perfect fixation of the object with both eyes.

(0) "What muscles are involved in following an object
from one's right side to his left ? In each other di-
rection in turn?

VISION. 221

(^) Do all of these muscles seem to act perfectly in

all of the subjects examined ? If not; describe any

variation.

(0) Convergence, (a) Let the subject direct his gaze at
the tip of the observer's ear, and without warning
change his point of binocular fixation to some distant
object in the same line of vision. What change in
the eyes of the subject is noticeable by the observer ?
What muscles were involved in producing the change ?
(/) Hold an object in front of the subject and 1 m.

distant. Move it directly toward the subject's eyes

and note the convergence of the lines of vision of

the two eyes. What muscles perform the act ?
(/) Through how short a distance may the object be

moved in the direct line of vision without causing a

discernible change of the angle of convergence of

the two eyes.
(</) From the central, 1 m. position, carry the object

to a point about ^ m. to the right, and ^ m.

above the eyes of the subject. What muscles are

involved in the act of convergence ?
(>) Is the power of convergence apparently normal in

all members of the class ? If not, describe minutely

any variations.

XLIX. Miscellaneous experiments.*

a. Schemer' s experiment.

(1) Prick two smooth holes in a card at a distance from
each other less than the diameter of the pupil. Fix
two long, fine needles or straws in two pieces of wood
or cork. Fix the cardboard in a piece of wood with a
groove made in it with a fine saw, and see that the
holes are horizontal. Place the needles in line with
the holes, the one about eight inches, the other about
eighteen inches from the card.

(2) Close one eye, and with the other look through the
holes at the near needle, which will be seen distinctly,
while the far needle will be double, both images
being somewhat dim.

(3) With another card, while accommodating for the
near needle, close the right-hand hole, the right-hand
image disappears; and if the left hand hole be closed,
the left-hand image disappears.

(4) Accommodate for the far needle, the near needle
appears double. Now close the right-hand hole, and
the left hand image disappears; and on closing the
left-hand hole, the right-hand image disappears.
[Practical Physiology — Stirling.]

(5) Explain the phenomena, drawing figures which show
just what must take place in the eye.

*The miscellaneous experiments of Lesson XLIX have been taken
from Stirling's Practical Physiology. The author takes this place and
opportunity to acknowledge his indebtedness to Prof. Stirling.

222

VISION. 223

) Pur kinje- Sans orfs images.

(6) In a dark room, light a candle and hold it to one
side of the observed eye and on a level with it. Ask
the person to accommodate for a distant object, and
look into his eye from the side opposite to the candle,
and three reflected images will be seen. At the
margin of the pupil, and superficially, one sees a small
bright erect image of the candle flame reflected from
the anterior surface of the cornea. In the middle of
the pupil there is a second less brilliant and not
sharply defined erect image, which, of all the three
images, appears to lie most posteriorly. It is reflected
from the anterior surface of the lens. The third image
lies toward the opposite margin of the pupil, is the
smallest of the three, and is a sharp inverted image,
from the posterior surface of the lens. Ask the person
to accommodate for a near object, and observe that
the pupil contracts, and the middle image — that from
the anterior surface of the lens — becomes smaller and
comes nearer to the corneal image. This shows that
the anterior surface of the lens undergoes a change in
its curvature during accommodation.

(7) Place in a convenient position on a table a large
convex lens, supported on a stand. Standing in front
of it, hold a watch glass in the left hand in front of
the lens and a few inches from it. Move a lighted
candle at the side of this arrangement, and observe
the three images described above. Substitute a con-
vex lens of shorter focus, and observe how the images
reflected from the lens become smaller. [Practical
Physiology — Stirling.]

(8) Explain the phenomena, using drawings.
The blind spot.

(9) Marriotte's experiment. — On a white card make a black

224 LABOR A TOR Y G UIDE IN PHYSIOL OGY.

cross and a circle about three inches apart. Closing
the left eye hold the card vertically about ten inches
from the right eye and so as to bring the cross to the
right side of the circle. Look steadilyat the cross with
the right eye, when both the cross and the circle will
be seen. Gradually bring the card toward the eye,
keeping the axis of vision fixed on the cross. At
a certain distance the circle will disappear, /. e., when
its image falls on the entrance of the optic nerve. On
bringing the card nearer, the circle reappears, the
cross of course being visible all the time.

(10) Map out the blind spot.

Make a cross on the center of a sheet of white paper
and place.it on a table about ten or twelve inches from
you. Close the left eye and look steadily at the cross
with the right eye. Wrap a penholder in white paper,
leaving only the tip of the pen point projecting, dip
the latter in ink, or dip the point of a white feather in
ink, and keeping the head steady and the axis of vision
fixed, place the pen point near the cross and gradu-
ally move it to the right until the black becomes in-
visible. Mark this spot. Carry the blackened point
still further outward until it becomes visible again.
Mark this outer limit. These two points give the
outer and inner limits of the blind spot. Begin again
moving the pencil first in an upward and then in a
downward direction, in each case marking where the
pencil becomes invisible. If this be done in several
diameters an outline of the blind spot is obtained,
even little prominences showing the retinal vessels
being indicated.

(11) To calculate the size of the blind spot.
Helmholtz gives the following formula for this purpose:
When f is the distance of the eye from the paper, F

VISION. 225

the distance of the second nodal point from the retina —
usually 15 mm. — d the diameter of the sketch of the
blind spot drawn on the paper, and D the correspond-
ing size of the blind spot: -p = ~|| or D = Fj*.

d. The macula lutea or yellow spot. Maxwell's experiment,

(12) Make a strong solution of chrome alum — filter it,
and place it in a clear glass bottle with flat sides..
Close the eyes for a minute or so, open them, and
while holding the chrome alum solution between one
eye and a white cloud, look through the solution. An
oval or round rose spot will be seen in the otherwise
green field of vision. The pigment in the yellow spot
absorbs the blue-green rays, hence the remaining
rays which pass through the chrome alum give a rose
color.

(13) Is it possible to calculate the size of the macula
lutea?

e. Shadows of the fovea centralis and retinal blood vessels.

Move, with a circular motion, a blackened card with
a pinhole in its center, in front of one eye looking
through the pinhole at a white cloud. Soon a punc-
tated field appears with the outlines of the capillaries
of the retina. The oval shape of the yellow spot is
also seen, and it will be noticed that the blood vessels
do not enter the fovea centralis. Move the card ver-
tically, when the horizontal vessels are most distinct.
On moving it horizontally, the vertical ones are most
distinct. Some observers recommend that a slip of
blue glass be held behind the hole in the opaque card,
but this is unnecessary.

L. Perimetry.

In the foregoing experiments we have dealt exclusively
with what is called direct vision, i. e., with phenomena in-
volving the formation of a clearly defined image upon the
macula lutea. Every one has noticed that outside the range
of direct vision one may still get a pretty definite idea not
only of form but of color as well. It is the purpose here
to ascertain just how far this field of indirect vision extends
in every direction from the visual axis; or, to locate the peri
meter of the field of indirect vision. Various instruments
have been devised — called perimeters to aid one in peri-
me try.

All of these appliances have for their object the map-
ping of the field. In all exact methods the map takes the
form of a polar map, the pole corresponding to the point
where the line of vision would pierce perpendicularly the
plane of the map.

1. Appliances. — A perimeter, or ruled blackboard, Fig. 32;
perimeter charts, such as shown in Fig. 33.

2. Preparation. — A very economical and exact perimeter
may be constructed in the following manner :

Take a blackboard whose dimensions are abont 1 m. by
1.5 m. Locate a point 40 cm. from one end and 50 cm. from
either side. Let this be the point of fixation or the
point where the line of direct vision falls upon the sur-
face of the board.

We propose now to draw upon the board a series of
circles whose distance from one another shall represent
an angular distance of 10°. Reference to Fig. 31 makes

226

VISION.

227

it evident that if the line A B represent the plane sur-
face of the blackboard and if the eye be placed at O the
equal increments of 10° on the quadrant become a series
of increasing increments upon the surface of the
board. The numbers at the right (Fig. 31) show just
how many centimeters the radius of each successive
circle should be provided the distance of the eye from
the board be taken at 20 centimeters.

13 J •

7.3 -

11.1 ••

It,.!-

FIG. 31.

FIG. 31. For de-
scription see

FIG. 32. Showing method of ruling a black-
board for use in perimetry. The radii of the cir-
cles are given at the line A B in Fig. 31.

After drawing the circles, draw meridians which divide
each quadrant into three to nine subdivisions. The
completed blackboard chart will have the appearance
and proportions shown in Fig. 32. The circles and

228 LABORATORY GUIDE IN PHYSIOLOGY.

meridians should be traced permanently in slate-colored
enamel upon the surface of the blackboard. Any marks
made upon the board with chalk may then be erased
without disturbing the perimeter circles.

Make test objects in this manner. To a soft pine disc
3 or 4 cm. in diameter and 1 cm. thick fix a 20 cm.
handle of hard wood. The whole should be given a dead
black surface, India ink is good for this purpose. Upon
the disc one may fix with a pin the test object : a circle
or a square or other form in white, yellow, green, blue
or red.

Each blackboard chart must be provided with a rest
or contrivance to insure that the subject's eye is 20 cm.
from the surface of the board. Whether this takes the
form of a rod of wood extending out from the board and
so adjusted that when the subject rests the most promi-
nent infra-orbital region upon its end, the cornea will be
20 cm. from the center of the chart; or whether it takes
some other form that insures the same result is of little
consequence.
3. Experiments and Observations.

In all the observations which are subsequently indi-
cated, it is taken for granted that the visual axis is per-
pendicular to the surface of the chart, that the center of
the chart is the point of fixation, and that the accommo-
dation is kept uniform, i. e., the eye is either uniformly
focused on the pole of the blackboard perimeter or uni-
formly relaxed; further that the eye not under observation
be closed or closely shaded.

(1) Examine the upper median quadrant by sweeping a
white circle or square around arc. 60°, keeping the test
object as near the surface of the chart as possible. If
the subject does not see it at all, try latitude 50°. Hav-
ing located the circle which seems to be near the boun-

VISION. 229

dary, locate upon each meridian a point which indi
cates the limit of indirect vision in that direction. Join
with a continuous line the points located, thus inclos
ing an area of indirect vision.

(2) Test the lower median quadrant in the same way.
Is the total area covered by indirect vision in this
quadrant greater or less in extent than that in the
upper quadrant?

(3) Test the upper-lateral quadrant and then the
lower-lateral quadrant. Are these two quadrants
practically equal ?

Is there any ready explanation why the outer two
quadrants should contain such an excess of area over
the inner two quadrants ?

(4) To record the perimeter outline.

For this purpose one should have printed charts like
the one given in Fig. 33. Note that here the circles
are equidistant. They represent concentric arcs of a
quadrant with 10° of the circle between each two,
while the circle upon the blackboard-chart represent
a radial projection of these arcs upon a plane tan-
gent to the sphere at the point of fixation.

In transcribing the perimeter upon the record chart
one has only to locate the twelve or more points lo-
cated upon the observation chart and join these points
into a continuous perimeter.

Point x, Fig. 30 for example, would naturally fall at
x' Fig. 31; pointy corresponds to y'; Z to Z' whose
reading is : " Upper-lateral quadrant arc 64°, 70°
from vertical.

(5) In the above experiment we have determined the
perimeter for light sensation only; the subject be-
ing conscious simply of a light or white spot on a dark
ground but not certain whether the spot is circular or

LABORATORY GUIDE IN PHYSIOLOGY.

square. Determine now the form perimeter, i. e., the
limits of the field within which a circle can be defi-
nitely differentiated from a square or triangle.

Chart the form-perimeter, i. e., transcribe the peri-
meter upon the record chart. Is it similar in general

FIG. 33. Perimeter chart for recording the limits of indirect vision for
light, for color, and for form.

form to the light perimeter ? Is it much smaller in area ?
Determine and chart various color-perimeters : (a)
yellow; (b) red; (c) green and (d) blue.

VISION. 231

Have the color-perimeters the same general form
as the light-perimeter? If not, describe any noticea-
ble variations. Which of the color-perimeters incloses
the greatest area? Enumerate them in order of area.
Is this the order which one would expect? Give
grounds for position.

(7) Take corresponding perimeter for the other eye. To
use the same blackboard it will be necessary to turn it
the other edge up. In what general respect do the
perimeters of the right eye differ from those of the
left?

(8) With the help of the light or form-perimeters of
the right and left eyes, determine the field of binocular
vision. Is this the field of binocular direct vision or
binocular indirect vision ?

LI. Determination of normal vision, a. The acuteness of

direct vision, b. The range of accommodation.

c. The amplitude of convergence.

a. The acuteness of direct vision.

/. Appliances — Charts printed with Snellen's test type;
astigmatic chart; test lenses of following strength:
+.50 D., +.75 D., + 1.00 D., +2.00 D., + 3.00 D.,
— .50 D., — .75 D., — 1.00 D., — 2 00 D., —3.00 D.,
+ 1.00 D. cyl., + 2.00 D. cyl., — 1.00 D. cyl. — 2. D.
cyl.; simple test frames, and shade; a photometer; Holm-
gren's worsteds.

2. Preparation. — Preparatory to testing normal vision it is
necessary to make a few general statements regarding:
(1) The numeration of lenses.

The refractive power of a lens is the reciprocal of its focal
distance. The refractive power of a lens whose focal
distance is 1 m. is, for example, only one-half as great
as that of a lens whose focal distance is 0.5 m. Mon-
oyer introduced the term dioptre as a unit in measur-
ing lenses. One dioptre — (1 D.) — represents the
refractive power of a lens whose focal distance is 1
m.; 2 D. corresponds to ^ m.; 3 D. to ^ m.; 4 D. to
^ m., etc. 0.5 D. represents the refractive power of
a lens of 2 m. focal distance; 0.25 D. of 4 m. focal
distance, and 0.125 D. of 8 m. focal distance. If the
lenses are convex (bi-convex) a plus sign is prefixed
to the number, i. e., + 5 D., means a bi-convex lens of
5 dioptres refractive power, or \ m. focal distance.
While — 5 D. means a hi concave lens of \ m. negative
focal distance.

232

VISION. 233

The use of cylindrical lenses is frequently necessary.
A cylindrical lens is a section of a cylinder parallel to
its axis. Cylindrical lenses may be convex or concave.
A convex cylindrical lens capable of bringing rays to a
linear focus at a distance of one half meter would be
designated as follows: -f- 2 D. cyl.
(2) Test types and visual angle.

The visual angle is that included between lines joining
the extremities of an object and the nodal point, or the
angle subtended by an object, at the nodal point. In
Fig. 29 the object at d subtends the angle v, while
the object at D though much larger subtends the same
angle v. Now it has been determined by Snellen that
the normal eye distinguishes letters subtended by an
angle of 5 minutes. If we let d^distance of object
from nodal point, n = distance of image from nodal
point, i length of image and o of object, then:

(1) i :o: :n:d;

(2) o = 1Ld;

= tan. v

(4) . •. o =d tan. v*

The tangent of 5' = 0. 001454; assume d = l m (1000
mm.); what is the height of the smallest letter dis-
cernible to the average normal eye at that distance?

At 1 m. height of letter, o = 0.001454X 1000 = 1.45
mm.

Determine the height of the letters for each of the
following distances respectively: 60 m., 30 m., 20 m.,
15 m., 12 m., 9 m., 6 m., 4.5 m., 3 m., 2.5 m.,2 m., 1.5
m., 1 m., 0.75 m., 0.50 m.

What is the size of the image in all these cases?
A cultivation of the visual power of the eye may
readilv in the emmetropic eye bring up its definition

234 LABORATORY G UWE IN PH YSIOL OGY.

to 3^ above the average or so that the minimum visual
angle for acute vision equals 4'. What is the size of
the image when it subtends an angle of 4'? The test
letters are made with the width of the strokes \ the
height of the letter. What is the width of the retinal
image of one of the strokes?*
^. Experiments and Observations.

(I) To test the form sense, — In all of the tests here de-
scribed it is understood unless otherwise stated that
the subject sit directly facing the chart which should
be six meters distant, and well illuminated.

(1) Let the subject put on the test frames with the
left eye shaded, and direct the right eye to the let-
ters of the line marked 6 m. These letters in their
vertical dimension subtend an angle of 5'. The
average normal eye will be able to recognize
easily every letter in the line. Should there be any
hesitation in the differentiation of C from G, of P
from D or F, of Kfrom X, etc., make a note of it; its
significance will be apparent later.

Now in recording the acuteness of vision one com-
pares the minimum angle of distinct vision in the
subject under observation with the normal. If the
subject reads readily at 6 m. the type that is normal
for 6 m., he is credited with normal vision or with a
minimum visual angle normal or unity. This is ex-
pressed in the following manner: Let V equal visual
acuteness; d, the distance from chart; D, the dis-
tance at which the type should be read: V = -~ . In
the above case V=g- or 1, i. e., normal vision.

(2) Suppose that the subject cannot read the 6 m-

* The size of the cones of the macular region varies from 0.0033
to 0.0036 mm. in diameter.

VISION. 235

line readily, let him try the line above. If he
reads that readily his visual acuteness would be:
V = g=:-; two-thirds normal. It is usual, however,
not to reduce the fraction but to use 6 for the nume-
rator always.

(3) How shall one express visual acuteness for an in-
dividual who reads at 6 m. what he should read at
21m.? At 24 m ? At 30 m.? At 4.5 m.? At 3 m.?

(4) How many members of the class have a visual
acuteness greater than unity? May a visual acute-
ness above the normal be attributed in any degree
to cultivation of the vision, or is it to be interpreted
solely as a natural endowment?

(5) Make upon a white card with india ink a series of
vertical lines 1 cm. apart, beginning with a line of
1 mm. breadth, and decreasing gradually to a hair
line; place the card upon a blackboard 6 m. di-stant;
let a subject with high visual acuteness say how
many of these lines he can see.

With dividers and rule measure the breadth of
the finest of the lines seen. What is the visual
angle of that breadth? What is the breadth of the
retinal image of the line? Can the subject see the
same number of lines when they are horizontal? If
not, how may the fact be accounted for?

(6) If it be found that the subject cannot see clearly
the largest letters upon the test chart let him move
to a shorter distance.

Suppose that he sees clearly the 30 m. type at 2
meters, what is the value of V? How far would he
be able to read the 6 m. type? At what distance
would he probably have to hold a book whose type
has a height of 1.8 mm.?

(7) (a) Let a subject take the seat, 6 m. distant

236 LAB OR A TOR Y G UJDE IN PH YSIOL OGY.

from the chart. Hold before his eye a -f-0.75 D.
lens, it will probably make indistinct and blurred
distant objects which were, without the lens, clear.
If such be the case it is likely that refraction of the
eye is normal and for our purpose it may be re-
corded as an emmetropic eye.

(<£) If, however, the vision remains perfectly clear
for distant objects, with the +0.75 D. or the +1 D.
lens before the eye it is evident that the refraction
of the eye is not normal.

(<:) Suppose, on the other hand, that distant objects
cannot be clearly seen with the unaided eye; but,
with the help of concave lenses, clearly seen, it is
evident again that the refraction of the eye is ab-
normal.

(8) In case (7 c), where were the parallel rays
focused when the concave lens was used ? Where
were the parallel rays focused in the unaided eye ?
Would it be possible for the condition to be cor-
rected by an exercise of the accommodation? If
the punctum remotum is 2m., and if the refractive
indices and curvatures of the refracting surfaces are
all normal, in what way must the eye differ from the
normal eye ? This condition is called nearsighted-
ness or myopia.

(0) In case (7 £), if a subject can read all of the letters
expected of the normal eye one credits him with
V=-|; but, the eye may have accomplished the re-
sult at the expense of more or less effort.

If the eye have a punctum remotum beyond infin-
ity; /. e. , if the rays of light from a distant object
are not yet converged to a focus by the time they
reach the retina in the resting eye it will require a
certain effort of accommodation to produce a clear

VISION. 237

image. Such is the condition in the farsighted per-
son, the condition is called hyperopia. The term
farsightedness does not mean that the subject can
see farther than the average individual but that he
can see far more easily than near. If a subject with
V=| can see as clearly or more clearly when the
4-0.75 D. lens is in front of the eye there is no
reasonable doubt that hyperopia in some form is
present.

(10) Let the subject direct the line of vision toward
the center of the chart for testing astigmatism. It is
probable that not all of the radiating lines will appear
equally clear cut and black, for most persons have a
small degree of astigmatism. If the lines are unequal-
ly clear, where are the clearest ones located? Do they
describe a diameter across the circle ? If so,
describe the location of the clear diameter, 0° — 180°
being the horizontal diameter, and 90° — 90° the verti-
cal one.

(11) («) If the subject has normal vision with no
astigmatism or normal vision despite a slight as-
tigmatism, he may be given a better conception
of just what a moderate degree of astigmatism is
by putting a+ 1 D. cyl. lens before his eye; or a
rather high degree of simple astigmatism by try-
ing a + 2 D- CY1- or + 3 D. cy1-

(<£) How may the subject be made artificially hy-

peropic?

(<:) How, artificially myopic ?
II. To test the light sense.

With the photometer test the subject's power to deter-
mine the difference in the illumination of the two discs
of the instrument.

238 LAB OR A TOR Y G UIDE IN PHYSIOLOG Y.

III. To test the color sense.

Let the subject take the three test colors: light

green, purple and red, and choose from the mass of

worsteds the colors which he considers similar ones,

placing the chosen color in the class to which it be-

longs. It is not difficult to determine whether or not

the subject has a normal color sense. If, for example,

he is red blind he will not see the red in the purple,

or related colors, but will classify these with the blues,

while the reds will be confused with the greens.

b. The range of accommodation __ The amount of

refractive change induced by the eye in adjusting for its

punctumproximum after it has been at rest, i. e., after it

has been adjusted for its punctum remotum, is termed

the range of accommodation. In a previous chapter

the punctum proximum and punctum remotum were deter-

mined. It was reserved for this place to express the

position of these limits of accommodation in terms of

dioptres, and thus most readily determine and definitely

express the range in simple dioptres. The relation of

this to what has just preceded will be evident.

Let R represent the distance of the punctum remotum
from the eye, then the refraction at rest or the static re-
fraction r equals the reciprocal of the distance:

Let P be the distance of the punctum proximum from
the eye, then the maximum refraction of the eye, p
equals the reciprocal of the distance:

(2) p = |.

When R = oo, •- = 0, i. e., static refraction equal zero.
When P =/s meter, -~ — 8.

VISION. 239

Let A equal the range of accommodation; Donders
expressed the range of accommodation thus:

Take an example: Let the punctum remotum be 50
cm. (I/? m.) from the eye, the punctum proximum
10 cm. (y1^ m.); substitute the distances expressed in
meters in formula (4) and one obtains A = \ m. The
range of accommodation, i.e., the accommodative power
of the eye is equal to a lens of \ m. focal distance. But
a lens of | m. focal distance is an 8 dioptre lens. A much
simpler way of arriving at this result is to use:

r (= 1) and p ( =-p). If we let a = -i, then we may
write:

(5) a = p — r.

To apply this formula to the above example we have
a — 10 D. — 2 D. = 8 D.
7. Experiments and Observations.

(1) Determine the range of accommodation for each
member of the class.

(0) Determine punctum remotum and punctum proxi-
mum.

(b) Record these quantities in meters.

(V) Substitute these values in formula (5) expressing
the distances in the corresponding dioptres, i. e.,
using the reciprocals of the distances.

(2) Range of accommodation in myopia.

(a} Is r positive or negative in myopia ?

(£) Is a always less than p, or may it sometimes be

greater ?
(<:*) What is the average range of accommodation of

the myopes of the class ?

240 LABORATORY GUIDE IN PHYSIOLOGY.

(3) Range of accommodation for emmetropia.
(ci) What is the value of R in emmetropia ?
(J)} What is the value of r in emmetropia?

(c} What is the relative value of a and p in this class

of cases ?

(d} What proportion of emmetropes in the class?
(e} Have they all the same range of accommodation ?
(/) Can any probable cause be assigned for any varia-

tions which may be found ?
(g) How does the average range for emmetropes com-

pare with the average range for myopes ?

(4) Range of accommodation for hyperopia.

(a) If the punctum remotum is " beyond infinity" (!)
that is equivalent to saying that the eye at rest does
not focus parallel lines (from infinity) upon the
retina, but the lines must be more than parallel, i. e.,
from beyond infinity; or, better, convergent; but if
they are convergent they would meet behind the
cornea. The p. r. for hyperopes is then nega-
tive in direction and is equal to the distance,
behind the cornea, at which the convergent lines
would meet if prolonged. It follows that -^- is in

It

the case of hyperopes negative. Our formula (3)
would then take the form:

Therefore, formula (5) becomes (5') a = p -f- r.
Now, in determining r one may use a convex lens
of such a strength as to give the rays the requisite
convergence. The value of the lens in dioptres is,
of course, the value of r. In the hyperope a is
always greater than p. As the determination of the
punctum remotum of the hyperopic eye is a matter

VISION. 241

for the clinician to deal with, we will omit its deter-
mination here.

(£) If a member of the class wears glasses having the
following formula for the right eye, -|-2D, and if his
punctum proximum is 12.5 cm. distant from the
cornea, what is his range of accommodation ?
(c) What is the range of accommodation of those
hyperopes in the class whose punctum remotum
may be determined from the lenses which they use?
(</) May variations in range be accounted for?
(e) Is the average range greater or less than that for

myopes? For emmetropes ?

(5) Tabulate the values of p and of r for the class, first,
with respect to age, arranging in the first column all
of the cases which range between eighteen and twenty
years, in the second column twent)-one to twenty-
three, and so on. Determine the average for p and
for r from each age column.
(0) Does age within the limits of your table affect

the punctum proximum ? If so, how ?
(^) Does age affect the punctum remotum as shown

by your table ?

(V) If the volume of data justifies it, make a chart
showing the effect of age upon the range of accom-
modation. Use the age units for divisions of the
axis of abscissas, and dioptre units of p and r for
the divisions of the axis of ordinates.

c. The amplitude of convergence.— The fact of the con-
vergence of the visual axes of the two eyes in binocular
vision has been demonstrated in a previous lesson. We
come now to the measurement of this function.

To measure convergence. — To get a clear conception of
the situation, let us call the line which joins the centers
of rotation of the eyes the base line. A plane perpen-

242 LAB OR A TOR Y GUIDE IN PH YSIOLOG V.

dicular to the middle of the base line may be called the
median plane. Any point in this plane which is fixed by
the two eyes in binocular vision may be called \he point
of binocular fixation. The line joining this point to the
middle of the base line would lie in the median plane,
and would be called the median line.

If the point of fixation be at a great distance (infinity)
the lines of fixation of the two eyes would be parallel to
the median line. In this case there would be no con-
vergence. If, however, the point of fixation be near there
will be a convergence of the two lines of fixation toward
that point. The amount of convergence is greater the
nearer the point, and is called the angle of convergence.
The angle of convergence is then the angle between the
line of fixation at infinity and the line of fixation at the
given distance less than infinity, the given distance be-
ing measured on the median line, beginning at the base
line.

The geometric situation is indicated in the accom-
panying figure (Fig. 34). Let C represent the center
of rotation of the left eye, M the middle of the base line
and the origin of the median line; CP the line of fixa-
tion of an object at infinity; MM' the median line; the
line CM is one-half the base line; represent the distance
CM by b. The angle D'CP is the angle of convergence
when D' is the point of binocular fixation. As
to the exact measure of the angle, it is evident from
the figure that the line MD', which we may represent by
d, is the cotangent of the angle of convergence (ang. c).

The unit of measurement for the angle of convergence
is the meter angle (Ma) of Nagel. The meter angle is
the angle of convergence when the point of binocular
fixation is 1 m. distant (d = l,000 mm). Ma equals the
angle whose cotangent is g (cot Ma=!j). The aver-

VISION.

age base line being 64 mm., the average Ma may be
thus expressed: Cot Ma=^9; Ma=l° 50'. It is not
customary to use in practice the absolute values for the
angles, but a convenient series of approximate values
suggested by Nagel.

If d = 500mm. (^m.), ang. c = 2 Ma; if d — ^ m.,

FIG. 34.

FIG. 34. For description
see LI-C.

FIG. 35.

FIG. 35. For description
see Ll-C-(5).

ang. c = 3 Ma. If d — ^ m., the accommodation = 4 D
and angle of convergence = 4 Ma.

Besides the convenience of this system, it indicates
at once the direct relation between accommodation and
convergence.

The amplitude of convergence is the total number of

244 LABORATORY GUIDE JN PHYSIOLOGY. '

meter-angles of convergence which the individual can
call into play. It is the difference between the punctum
proximum of convergence [pc] and the punctum re-
motum of convergence [rc] expressed in meter angles;
which are really the reciprocals of the distances. This
may be thus expressed:

CO rc = Fc— ifc in distances, or;
(2) ac=;pc — rc in meter angles.

Experiments and Observations. — Let each member of the
class be in turn the subject of examination.

(1) Determine the pupillary distance, i. e., the distance
from the center of one pupil to the center of the other
when the eyes are fixed on a distant object. One-half
of this is approximately equal to b, and in the experi-
ments which follow may be used as such.

(2) Take a board 1 m. in length and 10 cm. in width.
Along the middle of one side draw a line which may
represent the median line; graduate the line in
decimeters; the proximal ^ m. may be graduated in
centimeters. At each centimeter or decimeter bore a
small hole into which a post may be set. Make two
posts about 5 cm. or 10 cm, in height; into the top of
one set a needle, split the top of the other so that it
will hold a card printed with fine type (not to exceed
1 mm. in height, finer if possible). Support the
board so that it shall be in a horizontal plane and
5 cm. or 10 cm. below the eyes.

(3) To determine the punctum proximum of convergence-.
(#) Let the subject sit so that the line on the board
shall be in the median plane and parallel to the
median line; let him look at the needle when the post
is set at 1 m. Supposing that his punctum remotum
is at infinity, what is the ang. c.?

VISION. . 245

(£) Let the subject look in turn at the needle when
the post is set at 50 cm.; at 40 cm.; at 30 cm.; at
25 cm.; at 20 cm.; what is the ang. c in each case,
expressed in meter angles ?

(<:) From this point if the needle appears perfectly
clearly defined move the post up toward the eyes
1 cm. at a time as long as the vision is binocular
and the image single.

As soon as the image is double one may be cer-
tain that the eyes are no longer able to converge
sufficiently to bring the images upon corresponding
points of the retina and that the punctum proxi-
mum of convergence (pc) has been passed. Find
the nearest point at which the image is single — the
nearest point at which the fine printing on the card
is perfectly clear; this is the punctum proximum of
convergence (pc).
(//) Determine the punctum proximum of conver

gence for each individual in the class.
(4) To determine the punctum remotum of convergence (rc).
If the eyes can be directed parallel but cannot
diverge, the punctum remotum may be expressed as
follows: tc = ~ = ~—0. Landoldt says, however,
that "the majority of normal eyes can diverge more
or less," i. e., there is a negative convergence ( — rc).

The formula — (2) . . . ac = pc — rc becomes

a' = pc_(— rc); or
(2'). . .ac = pc+rc

Let it be noted that in this case the value of r°
cannot be determined by carrying the object to a
greater distance, but recourse must be had to abduct-
ing prisms, i. e., prisms whose apices are turned away
from the median line. The negative convergence may

246 LABORATORY GUIDE IN PHYSIOLOGY.

be determined by finding " the strongest prisms which
a person can overcome"; while seeing a distant object,
without double vision. The deviation of a prism may
be taken as half the angle of the prism; a No. 6 prism,
produces a deviation of 3°. If only one prism be
used the 3° is divided equally between the two eyes.
Let it be understood that two prisms of equal angle be
used.

(5) To compute the ang. c in meter- angles for any prism and
any length of base-line.

Let n equal the angle of deviation, i. e., one-half the
number of the prism. Let b equal one-half the base-
line. Let d equal the distance of the punctum re-
motum, to be computed. Then,

(1) b : d : : sin n : cos n (see Fig. 35).

But the punctum remotum of convergence (rc) ex-
pressed in meter-angles, is found by dividing 1m. by
d, therefore

(Z\ rc- 100°
— bcotn

If a person whose base-line is 64 mm. is able by
divergence to overcome a pair of No. 6 prisms his
punctum remotum of convergence would be negative
and equal to 1.63 Ma. Determine the punctum re-
motum of convergence for each individual in the class.

(6) Determine the amplitude of convergence for each
member of the class using the formula; ac=pc — rc.
Tabulate the results.

(7) Compare this table with the one in which the range
of accommodation is recorded. Is there any parallel-
ism in the variations of accommodation and conver-
gence ? Does age seem to have any appreciable influ-
ence upon the amplitude of convergence ?

OPHTHALMOSCOPY AND SKIASCOPY.
By ALFRED M. HALL, A. M., M. D.

LII. Normal ophthalmoscopy, direct method.

Gould defines ophthalmoscopy as, "the examination
of the interior of the eye by means of the ophthalmoscope."
Normal ophthalmoscopy is the examination, by means of
the same instrument, of the normal eye or a model of
the normal eye.

1. Appliances. — An ophthalmoscope, with concave mirror;
dark room; lamp; and Thorington's skiascopic eye or an
equivalent.

2. Preparation. — Arrange the model and the lamp so that
they will be in the horizontal plane with the observer's
eye. Place the skiascopic eye directly in front of the
observer's eye, and the lamp a little to one side of the
model.

j. Operation. — Let the observer hold the ophthalmoscope
with the right hand, mirror forward, close to the eye,
directing the vision through the hole in the instrument.
Throw the light, reflected by the mirror, into the skia-
scopic eye. Find the red reflection of the fundus, then
gradually lessen the distance between the observer's eye

247

243 LABORATORY GUIDE IN PHYSIOLOGY.

and the model to about 2 or 3 cm. The skiascopic
eye will then be illuminated and the fundus with its
structures will be clearly defined.
^. Observations.

a. Adjust the model to represent the emmetropic eye.

(1) Determine, with the ophthalmoscope, the color of
the fundus. Enumerate the structures seen.

(2) Describe the papilla, or entrance of the optic
nerve. Is the papilla in the visual axis or to one
side of it? Describe its position with respect to
the visual axis of the eye and determine the most
advantageous position of observer, model and in-
strument to get a direct view of the papilla in the
right eye; in the left eye.

(3) Describe the location of the arteria and vena
centralis retina! with reference to the papilla.

(4) The ring formed by the border of the papilla is
sometimes called the scleral ring or the choroidal ring.
Can this ring be distinctly seen ?

(5) The macula lutea and the fovea centralis are the
most sensitive portions of the retina and are in a
direct line with the visual axis of the eye.

What is the most advantageous position of model,
observer and instrument in order to get a direct il
lumination of this part of the fundus? Describe
the appearance of the structures in question.

(6) Describe the retinal blood vessels minutely;
drawing a map of their distribution.

b. The observation of the retina in t'he hyperopic eye.

Adjust the model for three dioptrics of hyperopia.

(7) Are the retinal blood vessels distinct when the
above described method of observation is used?

(8) Place in the rack, before the model eye, the follow

VISION. 249

ing lenses, with each one testing for a distinct reti-
nal image :

*± 1' D., ± 2 D., + 3 D., and+ 4 D.
With which one of the lenses is the clearest
image obtained? Are all of the images of equal
size? Explain, giving a figure.*

(9) In hyperopia do the rays focus in front of, on,
or behind the retina? What direction do the rays
take after leaving the hyperopic eye from the illu-
minated retina? Are they parallel, divergent or
convergent ?

Observation of the retina in a myopic eye.
Adjust the model for myopia, e. g., three dioptrics.

(10) Are the retinal blood vessels distinct?

(11) What direction do the rays from the retina take
on emerging from the myopic eye, divergent, con-
vergent, or parallel?

(12) In which of these three cases would the normal
eye be able to get a clear image of the retinal struc-
tures ?

(13) In which case would a correcting lens be neces-
sary? Should one use a convex or a concave lens ;
and why ?

*In all work with the ophthalmoscope or retinoscope it is under-
stood that the observer's eye is emmetropic, either by nature or by cor-
rection, and that his accommodation is suspended. One may get a clear
view of the retina without fulfilling these conditions, but one cannot
draw reliable optical conclusions.

LIII. Normal ophthalmoscopy, indirect method.

/. Appliances. — The same as in exercise LII, with the addi-
tion of a lens of + 12 D. to -f 20 D.

2. Operation. — With the model or eye to be observed, the
light and the observer arranged as in exercise LII,
direct the light reflected by the mirror into the observed
eye and find the red reflection of the fundus of the eye.
Hold the lens between the thumb and index finger and
place it directly between the mirror and the eye under
examination, and at a distance from the latter of 6-8 cm.
Be careful that the center of the lens corresponds to the
center of the pupil and that the plane of the lens is per-
pendicular to the line of vision.
j. Observations.

a. Observation of the emmetropic eye.

(\) The rays of light emerging from the observed eye
are focused by the convex lens, which the observer
holds, and form an aerial image of the retina. If
a + 12 D. lens be used, and if its optical center be
held 8 cm. from the anterior surface of the cornea,
how far from the cornea will the aerial image be
formed ?

(2) Trace in the image all of the structures enumer-
ated in the direct method. Is the image erect or
inverted ? Is the field larger or smaller than one
sees in the direct method? Are the structures mag-
nified or the reverse? Account for all phenomena,
representing the optics of the case with a figure.

(3) Does a change in the distance between the cornea
of the model or eye and the lens which the observer

250

VISION. 251

holds alter the size of the image ? Account for
observation.

b. Observation of the hyperopic eye.
Adjust the model for 3 D. of hyperopia.

(4) Does an increase of the distance of the lens from
the cornea cause the image of the papilla to be
altered in size? Account for all phenomena.

c. Observation of the myopic eye.

Adjust the model to represent 3 D. of myopia.

(5) Does the increase of the distance of the lens from
the eye cause the image of the papilla to become
altered in size or reversed in position ? Account for
all phenomena.

(6) If the position of the + 12 D. lens which the ob-
server holds remain the same — 8 cm. from cornea —
will there be any variation in the distance from the
cornea of the retinal image for the hyperopic eye
and myopic eye ?

Will the distance for the hyperopic eye be
greater or less than for the emmetropic eye ? Why ?
Will the distance for the myopic eye be greater or
less than for the emmetropic eye ? Why ?

d. Observation of the human eye.

At this point in the student's work, let him practice
the direct and indirect method of ophthalmoscopy
upon his comrades, after two or three days of practice
he may pass to the following exercise.

LIV. Skiascopy,

Gould defines skiascopy as " a method of estimating
the refraction of the eye by observation, through the
ophthalmoscopic mirror, of the movements of the retinal
images and shadows" Synonyms: Fundus reflex test;
umbrascopy; pupiloscopy; koroscopy; keratoscopy; ret-
inoscopy, etc.

1. Appliances. — A simple retinoscope or an ophthalmos-
cope with a plane mirror; Thorington's skiascopic eye
or an equivalent; dark room; lamp; etc.

2. Operation. — The observed eye and lamp are to have
the same relative position as in ophthalmoscopy. Let
the observer sit directly in front with the eye in the
same horizontal plane with the lamp and observed eye,
and somewhat more than 1 m. distant from the observed
eye. Throw the light reflected by the mirror into the
observed eye; rotate the mirror slowly and a shadow will
be seen in the pupil of the observed eye.

j. Observations.

a. Observation of the emmetropic eye. Adjust the model
to represent emmetropia.

( 1 ) Does the shadow move in the same direction as the
mirror rotates or in the opposite direction, i. e., does
the shadow move "with the mirror" or "opposite?""

(2) Is the movement of the shadow quick or slow.

b. Observation of the myopic eye.

(I) Adjust the model to represent less than 1 D. of
myopia.
(3) Note that the shadow movement is with the

252

VISION. 253

direction of the mirror rotation and that it is rela-
tively quick.

(II) Adjust the model to represent a myopia of more
than 1 D.

(4) Note that the shadow movement is opposite the
direction of the mirror rotation and that it is quick
when the myopia is of low degree, slow when of
high degree.

(5) Observe alternately the three conditions indi-
cated above until their differences are so familiar
that any one of the conditions may be readily and
unerringly detected by the observer when they are
arranged for him by the instructor.

c. Observation of the hyperopic eye.

Adjust the model to represent any degree of hyper-
opia.

(6) Note that for a low degree of hyperopia the
shadow movement is with the mirror rotation and
quick.

(7) Note that for higher degrees of the condition the
shadow movement is with the mirror and slow.

(8) How may one differentiate a high degree of
myopia from a high degree of hyperopia ?

(9) Is there any difference in the size, shape, dis-
tance or position of the shadows in these two condi-
tions ?

d. Observation of the human eye.

Let the student practice upon his comrades.

NOTE : Observation of the astigmatic eye is inten-
tionally omitted here. It belongs more espcially to the
clinical phase of the subject.

PHYSIOLOGICAL H^EMATOLOQY.

Q. PHYSIOLOGICAL H^EMATOLOGY.
By W. K. Jaques, Ph. M., M. D.

INTRODUCTORY.

The scientific world is constantly giving her discoveries
to the medical profession to be utilized in diagnosing dis-
ease and in providing means to relieve suffering. Each fact
thus obtained is a step nearer to the goal of positive medi-
cine and removes us farther from the past with its unsatis-
factory theories and dogmas.

Blood, the most difficult tissue to study, has at last
begun to give up its secrets to the patient workers in phys-
iological and pathological laboratories. Although the facts
are few compared with the great labor it has taken to obtain
them, they are of such practical value that no practitioner
can afford to be without them.

The discovery that toxins and antitoxins were con-
tained in the blood serum made possible the production of
diphtheritic antitoxin and gives us the serum diagnosis of
typhoid fever, beside opening a wide field of possibilities
for the future.

The finding of the plasmodia.of malaria is often of the
greatest value in clearing up an obscure diagnosis. When
methods shall have been devised which will make their
detection less difficult, the discovery of the presence of
bacteria in the blood and the identification of the same will
be of great clinical importance.

257

258 LAB OK A TOR Y G U1DE IN PHYSIO LOG Y.

To understand the appearance of pathological blood, a
knowledge of normal or physiological haematologyis essen-
tial. It is the object of the following pages to assist the
student in obtaining this knowledge and in laying the
foundation for the study of pathological haematology.

A knowledge of the microscope and its technique is
essential and the work of the student should be so arranged
as to include considerable practice with that instrument
before entering upon a study of that subject.

If the practitioner has a fair knowledge of pathology,
histology and bacteriology, with the help of the following
suggestions he may take up with profit the subject of
haematology.

In class work the blood may be obtained from students.
The pain is minimized if the blood is properly obtained,
and practice on themselves will impress this fact upon the
students. The general practitioner can get material from
his patients.

The technique of haematology can only be acquired by
practice. The student will secure this more readily than
the practitioner because his attention will not be dis-
tracted by diagnostic possibilities. It is well for the prac-
titioner to go over the whole ground several times for the
sole purpose of mastering every detail. Unless the tech-
nical part of the work is correctly and easily done, the
specimens will be unsatisfactory, the results will be untrust-
worthy and the knowledge of the subject imperfect.

The methods here employed are those of the best
students of haematology with modifications from the ex-
perience of the author. Although the best to-day, to mor-
row they may be remembered only as the stepping stones
to more perfect work. Many truths are yet undiscovered
in this wonderful river of life — the blood — and the grati-
tude of a race will be due him who reveals them.

LV. Examination of fresh blood.

1. Appliances. — Microscope; one twelfth inch oil-immersion
lens; 22 mm. cover glasses; slides; saddler's needle and
holder; clean piece of old muslin one-half meter square;
paper and pencil.

2. Preparation. — Clean cover glasses and slides as follows:
Immerse in 60% acetic acid, then wash in soap and
water and place in dilute alcohol; just before using,
wipe dry and place under a bell-jar; the needle should
be so placed in the holder that it protrudes one-fourth
to one-third inch.

A convenient needle-holder, the exact size of which
is shown in Fig. 36, may be obtained from a dental sup-
ply house.

FIG. 36.

A medium saddler's needle may be obtained from a har-
ness shop. If too long, it can be broken and the point
used. These needles have three cutting edges so that
blood flows easily from a puncture made by one.
Operation. — Wipe the lobe of the ear with a damp
cloth; then briskly with a dry cloth; seize the lobe
with the left ringer and thumb quite tightly; thrust
the needle into the ear with a quick stroke. Wipe
away the first drop; then when the second drop has
become a little more than one eighth of an inch across
its base, bring the center of the cover glass under
the drop and touch the lower part without touch-

259

260 LABOR A TOR Y G UIDE IN PHYSIOL OGY.

ing the ear as shown in Fig. 46. Quickly place the
cover glass, blood-side down on a clean slide and exam-
ine.

4.. Precautions. — Cover glasses must be clean, dry and free
from dust. The blood must be collected quickly or it
will form rouleaux. A warm stage prolongs the normal
appearance of the blood. Placing the microscope in
the incubator at body temperature for half an hour before
using will keep the slide warm for some time. In adjust-
ing the needle for puncture the condition of the patient
should be considered. A full blooded patient will require
a smaller puncture than an anaemic one.

5. Observations. — Note that the red corpuscles are round
in shape. As the plasma dries, it causes currents; as
the corpuscles float in these they strike each other, dent,
elongate and act like bags of jelly, returning to their
round shape when free.

a. Red corpuscles.

(1) Note biconcavity; what causes it ?

(2) Are there variations in the size of the red cells?

(3) What is crenation? Note when it begins.

(4) Do you see two motions of red corpuscles ? De-
scribe any motion seen.

(5) Do you see small motile bodies in the plasma?

b. White corpuscles.

(6) How do white corpuscles differ from red ?

(7) Do they float as easily in the blood current?

(8) How do they compare in size with red corpuscles ?

(9) Why are white corpuscles smaller in fresh blood
than in dried specimens ?

(10) What movements do you see?

(11) Do you see any variation in size?

(12) In which kind do you see the amoeboid move-
ments?

PHYSIOLOGICAL U&MA TOLOG Y

261

(13) Do you see some white corpuscles with large
granules?

(14) What is the approximate ratio of the white cells
to the red ?

FIG. 38a. Thomr\-Zei?s blood-corpuscle counter.

LVI. Counting red corpuscles.

/. Appliances. — Microscope with one- seventh inch objec-
tive, and a mechanical stage; needle and holder; Thoma-
Zeiss counter.

2. Preparation. — (1) The counter and pipette should be care-
fully cleaned with water, followed by alcohol and thor-
oughly dried. (2) Prepare the following solution for
diluting blood :

Sod. sulph gm. 107

Aqua dist c c. 120

j. Operation. — Obtain the blood as described in Lesson LV,
allowing it to collect until almost ready to drop. Then
insert point of pipette into the drop and by sucking gently
draw the blood up to the mark 0.5. Wipe the end of
the pipette and insert it into the diluting solution, sucking
it up until the bulb is filled to the mark 101. Close
ends of pipette with fingers, rolling and shaking it about
for a minute. Blow out three drops of the diluted blood.
Then drop from the pipette on the round table of the coun-
ter just enough of the dilution to cover it when the cover is
placed upon it without causing any of the liquid to flow
over into the moat. (Fig. 38b). Place the counting
slide under the microscope and find the upper left hand
square; count all the corpuscles in it. Then count the
next square to the right and continue until all the upper
row has been counted; write down the number of cor-
puscles. Then move the counter so that the next lower row
can be counted from right to left continuing until all the
squares are counted. Clean the counter; agitate the

262

/'// YSIOLOGIL ',//, ILK MA TOLOG Y. 263

pipette, blow out a drop, place the diluted blood on the
counter and count as before. If the two countings are
nearly the same, this will be sufficient; if there is much
difference, a third field should be counted and an aver-
age taken of the two fields nearest alike. Divide the
number of corpuscles by the number of squares; multiply
this by 200 to make up for the dilution and then by 400,
because each square is equivalent to one four-hundredth
of a cubic millimeter. This will give the number of cor-
puscles per cubic millimeter. Count the corpuscles on

FIG. 38b.

FIG. 38b. Showing the right and the wrong way to fill a Zeiss count-
ing cell. a. Too little blood, b. Too much blood, c. The proper
amount of blood.

one half the boundary of each square but do not count
them on the other half.

4. Precautions. — See that the blood corpuscles are evenly
scattered over the field. (Fig. 39). If they are clus
tered, it shows faulty technique and the counting dilution
must be prepared again with more care. Clean counter
and pipette first with water and then with alcohol after
using, being careful to leave the tube perfectly dry. The
pipette is easily broken. Thefine lineson the counter are
injured by rubbing with a coarse cloth. The cover glass

264

LAB OR A TOR Y G VIDE IN PI I YSIOL OGY.

should be adjusted before the corpuscles have time to
settle.
Observations,

(1) Make counts of red blood corpuscles from several
apparently normal individuals.

(2) Is there any appreciable variation in the number
per cubic millimeter?

FIG. 39.

FIG. 39. a. Successful blood spread with corpuscles evenly distributed,
b. Poor spread with corpuscles clustered.

(3) Can the variation be attributed to faulty methods?

(4) What is the average count for normal individuals?

(5) What is the range between maximum and minimum
observations on the normal individuals observed ?

(6) Account, if possible, for the variations observed.

LVII. Counting white corpuscles.

1. Appliances. — Same as in Lesson LVI with the substitu-
tion of the large bore pipette.

2. Preparation. — Cut a square out of a circular piece of
cardboard which fits in the barrel of the microscope
with mechanical stage. The square should be just large
enough to bound the counting square of the counting
slide. (Fig. 40). Adjust the circular card with the square in

FIG. 40.

FIG. 40. Plan of cardboard
diaphragm for microscope tube.
For description see LVII-2.

FIG. 41.

FIG. 41. Showing the sequence of
the fields counted. For description
see LVII-3

it in the upper part of the microscope barrel just below the
eyepiece. By lengthening and shortening the micro-
scope the square can be adjusted to the square of the
counting slide.
(2) For a diluting solution, use the following :

Acidum acet c. c. 4

Aqua dist c. c. 100

265

266 LABORATORY GUIDE IN PHYSIOLOGY.

Operation. — Obtain blood as described in exercise LVI
and dilute with the above solution. Bring upper line of
ruled square to bottom of the square of the field; then the
field of the microscope will correspond to field one in the
figure. Count all the white cells in the field. Then fix
the eye on a cell in the upper margin and bring it to the
lower edge of the field; count this field and proceed in the
same way to field 3. Turn stage back to ruled space, usr
ing the border to indicate where to begin to count. Count
fields 4, 5 and 6; turn back to ruled square and proceed

FIG. 42.
FIG. 42. Position of solution tipped to receive pipette horizontally.

to 7, 8, 9; turn back to ruled square and count 10, U and
12. For a larger count, proceed in the same manner
from the central ruled space to count the additional
squares enclosed with dotted lines. The acetic acid in
the diluting solution renders the red corpuscles transpar-
ent or dissolves them entirely. If this does not so ap-
pear, the acid is too weak and more should be used to
obtain the desired results.

4. Precautions. — Make a good deep puncture. Have a large
drop of blood. Remember that the bore of this pipette
is larger than that of the pipette for red corpuscles and
the solution will run out if the pipette is held perpendic-
ularly. (Fig. 42.) The suction also must be more gentle

PHYSIOLOGICAL H&MATOLOGY. 267

than with the small bore pipette. Remember to thor-
oughly clean and dry the pipette after using. »
Observations.

(1) Estimate the number of white corpuscles per cubic
millimeter in several apparently normal individuals.

(2) What is the proportion of white to red corpuscles
in each individual ?

(3) Is there considerable variation in number of white
corpuscles in different individuals?

(4) Is there considerable variation in the proportion be-
tween white and red corpuscles in different individ-
uals?

(5) What may cause the variation ?

LVIII. Counting red and white corpuscles.

1. Appliances. — Microscope with one- seventh objective;
needle and holder; Thoma-Zeiss counter with small
lumened pipette.

2. Preparation. — Prepare the following solution for staining:

TOISSON'S SOLUTION.

Methyl violet, 5 b ' 025 gm.

Sod.chlor 1.000 gm.

Sod. sulph 8.000 gm.

Neutral glycerin 30.000 cm.

Aqua dist 160.000cm.

j. Operation. — Obtain blood as described above and dilute
1 to 200 with Toissorfs solution. Place the counting slide
under the microscope and find the upper left-hand square;
count the red corpuscles in each square from left to
right; then retrace the same field and count the white
corpuscles. Repeat this procedure with the next row of
squares, continuing the same way until all the squares
are counted. Write the number of red corpuscles on
one side of a line, the white on the other. Clean the
counter; agitate the pipette, blow out a drop, place the
solution on the counter and count as before. If there is
much variation between the number of first and second
field, count a third field and take the average of the
two fields nearest alike. Divide the total number of
corpuscles by total number of squares counted; multiply
by 200 (amount of dilution) and then by 400, which will
give number of corpuscles per cubic millimeter. The
use of this staining fluid enables the student to count

PHYSIOLOGICAL H&MATOLOGY. 269

both red and white corpuscles at the same time instead
of counting separately as in Lessons LVI and LVII. This
is important to determine the relative proportion of red
to white, or white to red corpuscles.

Precautions, — Extra care must be exercised in cleaning
pipette after the use of this staining solution.

Observations.

(1) Compare the results of this method with those
obtained in counting red and white corpuscles separ-
ately.

(2) Determine the proportion of white to red corpuscles
in a number of normal individuals.

(3) Has age any influence on the proportion?

(4) Has sex any influence on the proportion ?

(5) Has the general condition of the nutrition any in-
fluence ?

(6) Is the proportion always the same in one individual?
If not, is there any periodicity in the changes ?

(7) Determine, if possible, the causes of the variation.

LIX. Centrifugalizing the blood. To determine the rela-
tive volume of red corpuscles and plasma.

1. Appliances. — Daland's haematocrit (Fig. 43); small rub-
ber tubing to fit capillary tube; needle and holder; vase-
lin; white paper.

2. Preparation. — Adjust rubber to capillary tube. Put
empty tube in one arm of crosspiece to preserve bal-
ance.

j. Operation. — Obtain blood from the lobe of the ear as
heretofore described. Draw capillary tube full of blood.
Grease the finger with vaselin and hold over the free
end of the tube before drawing off the rubber. Place the
tube in the crosspiece of the instrument as quickly as
possible and revolve at least two minutes at the rate of
seventy turns per minute. Take out the tube and lay
on a piece of white paper to read the divisions. Each
degree of the scale is estimated to contain about 100,000
cells; hence, a tube in which the red column stands at
50 would indicate about 5,000,000 red corpuscles per
cubic millimeter. The use of this instrument is de-
signed chiefly to show the volume of red corpuscles rather
than the number^ as shown by the Thoma-Zeiss counter.

4 Precautions. — See that the instrument is securely at-
tached to the table and the crosspiece to the instru-
ment before setting it in motion.

5. Observations and Problems.

(1) Determine the volume per cent of red blood cor-
puscles in a number of normal individuals.

(2) Do apparently normal individuals have the same or

270

PHYSIOLOGICAL H&MAToLOGY. 271

approximately the same volume per cent of red blood
corpuscles. If not, seek for causes for the differences
in different individuals.

FIG. 43.
FIG. 43. Haematocrit.

(3) Does the same individual have the same volume
per cent of red blood corpuscles all the while ?

272 LABOR A TOR Y GUIDE IN PHYSJOLOG Y.

(a) If there is a variation is there any periodicity to

be observed ?
(/$) Seek for causes of any variations in the same

apparently normal individual.

(4) The volume per cent as recorded by the haematocrit
varies with the product of two factors ; the average
volume of the individual corpuscles multiplied by the
number of corpuscles per unit volume. (V x v X n)
(#) Is the average volume of the individual corpus-
cles (v) necessarily constant?

(£) If it is not constant, would one be justified in
drawing conclusions regarding the number of cor-
puscles per unit volume (n) after observing the
volume per cent (V) with the haematocrit?

(5) What variation of the observation as above made
would enable one to determine with reasonable accu-
racy the number of corpuscles per cubic millimeter ?

LX. Estimation of haemoglobin.

1. Appliances. — v. Fleischl's haemometer; medicine dropper;
distilled water; needle and holder; capillary tube; lamp.

2. Preparation. — See that the capillary tube is perfectly
clean and dry; if there is any doubt, draw a thread wet
with ether and alcohol through it. Fill one side of the
metallic cell about one-quarter full of distilled water.

FIG. 44.
FIG. 44. Fleischl's Haemometer.

j. Operation. — Puncture the ear and obtain blood drop.
Just touch outside of drop with capillary tube held in
a horizontal position; it should quickly fill by capillary
attraction. Carefully and quickly wipe away any blood

273

274 LA BORA TOR Y GUIDE JIV PHYSIO LOG Y.

that may be on the outside of the tube. Plunge it into
the well of water, shaking it back and forth to thor-
oughly mix the blood and water. With the medicine
dropper wash the tube with a few drops of distilled
water; then remove the tube and draw the solution in
and out of the dropper several times to be sure it is
well mixed. Then fill both compartments to the brim
with the dropper, taking care that the mixture of blood
and water shall not flow over into the pure water. Ex-
clude daylight, and by artificial light adjust the compart-
ment containing clear water, so that it comes over the
slip of colored glass. Adjust the reflector so that light
is thrown up through the well. Then adjust the slip of
colored glass until it corresponds with the color of the
diluted blood and read the amount indicated by the
scale. This will give the percentage of haemoglobin,
100 being the standard for normal blood.

Any approximate success with this instrument pre-
supposes a color sense. Even when this is present in
the student, the instrument itself is not entirely reliable
as there is sometimes a variation in the colored slips of
glass. It is also not reliable for percentages of haemo-
globin under 20.

4.. Precautions. — The capillary tube should be cleaned by
drawing through it a thread wet with alcohol and ether.
The tube must be filled and emptied quickly to prevent
coagulation. In reading the instrument, do not face
the light but let it come from the side. The instrument
should be so placed that the wedge will not move from
left to right but to and from the operator. Use as little
light as possible. Use first one eye and then the other.
Move the screw with quick turns rather than a gradual
motion, as the impression of a glance is better than a
prolonged look.

PHYSIOLOGICAL HMMATOLOGY. 275

Observations and problems.

(1) Determine in the cases of several normal individuals
whether the blood is normal when compared with
v. Fleischl's arbitrary scale. Let the same observer
make two or three consecutive tests of the blood of
each subject.*

Record for each subject the average of the two or
three tests made by one observer.

(2) Account, if possible, for any variations found.

(3) Do the individuals who show a low haemoglobin
reading show also a low volume per cent, and con
versely ? If so, would one be justified in the conclu-
sion that the hemoglobin varies as the volume per cent of
the red blood corpuscles ?

(4) Do the individuals who show a low haemoglobin,
reading, show also a smaller number of red blood cor-
puscles per unit volume, and conversely? If so, would
one be justified in the conclusion that the hcemoglobin
varies as the number of red blood corpuscles per unit vol-
ume?

(5) Are there any conditions in which both of these
conclusions may be consistent with the results of the
reasoning at the end of the previous exercise, LIX?

* If the same observer obtained aoproximately the same reading on
the second and third test of an individual's blood it may be taken for
granted that for comparison with each other this observer's readings
are sufficiently reliable.

LXI. "me microscopic technique of haematology. a.
Spreading blood, b. Fixing and staining.

a. "Making the spread.'*

1. Appliances. — Microscope with one-seventh objective;
needle and holder; square cover glass, J inch.

2. Preparation. — Clean six or more cover glasses with di-
lute acetic acid, soap and water, and alcohol.

3. Operation. — Puncture the ear and obtain blood as de-
scribed in Lesson LV. Hold a cover glass in each hand

FIG. 45.
FIG. 45. Showing the way to hold the cover glasses.

as shown in Fig. 45. With the one held in the left hand
just touch the center to the bottom of the drop, as in
Fig. 46, being careful not to touch the ear. Quickly
place upon it the cover glass held in the right hand as
in Fig. 47. If the blood is fresh and the glasses clean,
it will spread rapidly and evenly by capillary attraction.
The instant it stops spreading seize the upper cover
glass with the right hand as shown in Fig. 48, and pull
it quickly apart horizontally. lace the cover glasses,

276

PHYSIOLOGICAL HALMATOLOGY.

277

smeared side up, to dry. When dry, examine with a
one-seventh objective. It requires considerable practice
and skill to make a good spread, although the operation
seems simple enough. In a good spread, the red cells

FIG. 46.
FIG. 46. Touching the cover glass to the blood drop.

FIG. 47.

FIG. 47. Dropping cover

glass upon the drop

of blood.

FIG. 48.

FIG. 48. Showing manner of holding the
cover glass to jerk them apart.

are evenly distributed, as in Fig. 37. In a poor spread,
the cells are clustered, and new spreads should be made
until the desired result is obtained.

278

LABORATORY GUIDE IN PHYSIOLOGY.

4.. Precautions.- — Care must be taken to have just the
proper amount of blood; too little will not spread well
and too much makes the spread too thick to examine
well. The blood should not have time to coagulate. The
cover glass should not touch the ear in obtaining the
blood. The blood can be made to flow again after it has
stopped by rubbing the ear briskly with a cloth.

b. Fixing and staining.

/. Appliances.— Cover glasses; solution for staining; heater.

2. Preparation. — Clean cover glasses carefully with soap
and water, followed by alcohol. Instead of a copper
plate (Fig. 49) or oven over a Bunsen burner usually
used in laboratories, a heater as shown in Fig. 50 is rec-

FIG. 49.

FIG. 50.
FIG. 50. The water fixing plate.

FIG. 49. Common copper heat-
ing plate.

ommended. Cover glasses should be dried at boiling
point, which is constantly maintained in this heater, it
being filled with water and placed over a burner. There
is no danger of scorching, as there is on the strip of
copper over the Bunsen burner. With the pattern and
dimensions given in Fig. 51, any tinsmith can quickly
make the heater out of copper.

(2) Prepare the following solution for staining:

Ehrlich-Bondi powder (Griibler) 1 gm.

One-half per cent sol. acid fuchsin 5 c c.

Aqua dist 25 c.c.

Let this solution stand one week and filter.

PHYSIOLOGICAL H&MATOLOGY.

Operation.

(a) Obtain and spread blood as described in section a.

(<£) Place the cover glass, spread side down upon the
heater and maintain at 100°C. for fifteen minutes. This
process dries and fixes the preparation.

(V) Remove the fixed preparation; cover the film with
staining solution, allowing it to remain from six to ten
minutes. The time of staining depends upon the
length of time the film has been heated; a film fixed
quickly will stain more readily.

FIG. 51.
FIG. 51. Plan for constructing the water fixing plate.

(//) Rinse off the excess of stain in pure water and dry.
(<?) Mount in balsam.

4. Precautions. — Be sure that the water in the heater is
boiling before placing the films upon it. Do not let
the water boil too violently or it may boil over and
spoil the films. The films must be air dried before
they are placed upon the heater.

LXH. Differential counting of white cells and of red cells.

1. Appliances. — Microscope with one-twelfth oil immersion
lens; mechanical stage (not essential but convenient).

2. Preparation. — Stain as in Lesson LXI. Write the names
of varieties of cells, which may become familiar to the
eye by the study of the colored plate, and as each differ-
ent cell is discovered, record that fact by a check.

j. Operation. — Begin at the upper left corner of the speci
men and count toward the right the different cells as
they come into view. When the right border comes
into view move the specimen so that the adjoining lower
field is brought into range and count back again. Mark
the cells found under their proper heads. After the
observer has become familiar with the different cells he
can keep in mind the neutrophiles for the entire
trip across the field, but the others he had best mark as
soon as found.

Varieties of leucocytes. (Fig. 52 a.)
Polymorphonucltar neutrophiles. (Neutrophiles.)
Myelocytes,
Small lymphocytes,
Large lymphocytes,
Eosinophiles,
Eosinophilic myeiocytes.

Varieties of red cells. (Fig. 52 b.)
Normoblasts,
Megaloblasts,
Microblasts.
Macrocytes,
Microcytes,
Poikilocytes,
Polychromatiphilic cells.

280

-

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r r>§

111

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f& ft C

w « o
•-<;

-^ OH n

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CC O

E E

X Y.

LX1II. Study of bone marrow.

/. Appliances. — Strong vice; five-eighths inch cover glasses;
microscope; heater; Ehrlich's triple stain (See Lesson
LXI) ; section of bone containing red marrow ; saw.

2. Preparation. — Clean cover glasses as usual and have
water in heater or fixing-plate boiling.

j. Operation. — Saw a transverse section of bone one inch
thick. Place it in the vice and turn the handle until the
bone marrow begins to ooze out on the surface. Just
touch the surface of this with one of the cover glasses
and proceed exactly as in exercise LXI a, making as
good a blood spread as possible. Dry smeared side up.
Then fix and stain as described in LXI b. Place slide
under the microscope and make a differential count of
red and white cells as in LXII.

4.. Precaution. — Have the bone specimen as fresh as possi-
ble. Saw the piece to be used just before putting it in
the vice and then take the specimen from the freshest
side of the bone.

j". Observations.

(1) What cells do you find that are not found in normal
blood ?

(2) Can you trace these cells to the cells of normal
blood ?

PHARMACOLOGY.

H. AN INTRODUCTION TO PHARHACOLOGY.
By H. fl. Richter, M. D.

INTRODUCTORY.

While the following experiments will more forcibly im-
press the student's memory with the action of the drugs
under consideration than any didactic lecture possibly
could, this must be considered as of secondary importance.
The real object is to teach pharmacological technique — to
place the student in a position where he can at any time
in the future demonstrate experimentally to his own satis-
faction the activity or inactivity of any drug, and its modus
operandi.

With this object in view, experiments have been
chosen which can readily be performed by the student
himself. No attempt is made to show the various actions
of each drug used, but, instead, the most conspicuous and
easily demonstrated action of each is utilized. Considera-
ble time is expended on the reflex arc, because the action
of drugs on its different elements is most readily demon-
strated.

Little can be found concerning the doses to be used in
experiments. In order to save time and trouble, the dose
to be used in each of the following experiments is given.

286 LABOR A TOR Y G U2DE IN PHYSIOL OGY.

The student is presumed to have a fair working knowl-
edge of the technique of the physiological laboratory. The
use of the myograph, kymograph, etc., the setting up of
electrical apparatus, such as batteries, inductorium, commu-
tator keys, and the use and effects of same. As to the litera-
ture on the subject, the following are valuable, and have
been made free use of:

Smith's translation of L. Hermann's "Experimental
Pharmacology" is the only English work devoted to
technique; Brunton, " Pharmacology, Therapeutics and
Materia Medica," and "Pharmacology and Therapeutics;"
White, "Materia Medica and Therapeutics;" Stirling,
"Practical Physiology;" Landois and Stirling, "Text-
book of Human' Physiology." These comprise most of
what has been written on^the subject in English.

Each group of students^will need the following appar-
atus and material for the experiments :
One Daniell cell ; Dog and rabbit holder ;

Inductorium; Seeker; Pins;

Myograph; Pin-pointed pipette ;

Kymograph ; Fine and coarse thread ;

Contact key ; Normal saline solution ;

Two frog boards and stands; Gutta-percha tissue ;
Shielded electrodes ; Chloroform ;

Physiological operatingcase; Ether (common sulphuric);
Clippers ; Sulphate of morphin ;

Hypodermic syringe ; Sulphate of atropin ;

Commercial curare; Sulphate of strychnin;

Hydrochlorateof pilocarpin; Ticture of digitalis;
Sulphate of veratrin; Sodic carbonate;

Tincture of aconite ; Sodic sulphate.

LXIV. Curare.

1. Material. — One dog; 2 frogs; sodic chloride; curare.

2. Preparation.

Prepare following solution of sodic chloride, 0.06
grms. to 10 c. c. ; curare, 0.1 grm. to 10 c. c. Pith frogs.
Do not fasten the dog to the board, but simply restrain
him. Set up inductorium and myograph, the former so
as to obtain single induction shocks,
j. Experiments and observations.

(1) Give a hypodermic injection of 0.02 grm. curare to
the dog.

(a) Record the condition of the dog just before, and
every ten minutes after injections of curare with
special reference to:

(I) Muscular activity.

(II) Respiration — number and depth.

(III) Circulation — rate and rhythm of heart-beat.

(IV) Which stops sooner, respiration or circula-
tion ?

(3) Formulate the total effect of curare upon the
animal.

(2) Ligate the thigh of a frog, except the sciatic nerve,
near the knee-joint.

Inject into the dorsal lymph space 0.0012 grms.

curare.

(#) What elements enter into the formation of a "re-
flex arc?"

(£) What motor phenomena would result from in-
creased irritability of any part of the reflex arc ?

(<r) What motor phenomena would result from les-

287

8 LABORATORY GUIDE IN PHYSIOLOGY.

sened irritability or destruction of any element in
the reflex arc ?

(//) What effect has the ligature of the thigh on the
distribution of the curare ?

(>) How do the reflex arcs, of which the gastrocnemii
are the motor ends, differ with regard to the distri-
bution of the curare ? What part of the reflex arc
is protected from curare in the ligatured limb?

(/) Describe the relative reaction of the gastrocnemii
to stimuli (chemical, mechanical, electrical) applied
to various parts of the body and limbs.

(#) Is the sensorium intact? Is it reached by the
curare?

(Si) Is the cord intact? Is it reached by curare?

(3) Expose the sciatic nerves, near the body, in the frog
used in experiment (2); stimulate them.

(a) What elements in the reflex arc enter into consid-
eration in this experiment?

(<£) Which of these elements are exposed to, -which
protected from the poison ?

(c) Are both sciatics reached by curare?

(//) Is there a difference in the reaction of the gas-
trocnemii to the stimuli applied to the sciatic
nerves?

O) To what elements of the reflex arc have you lim-
ited the possible action of the curare ?

(/) Have you proven that curare does not affect the
nerve trunks?

(4) Expose gastrocnemii by cutaneous incision. Stim-
ulate the muscles directly.

(a) Is there a difference in reaction to stimuli ?

(£) If a muscle in a poisoned animal reacts to direct
stimuli, but not to indirect stimuli, though the nerve
fibers be proven to be intact, on what element in the
reflex arc must the poison act ?

PHA RMA COL OGY. 289

(<r) Why would you not use curare as an anaesthetic
if the poisoned animal does not react to painful
stimuli ?

(5) Make two muscle nerve preparations as described
on page 56. Dip the nerve of one, and the muscle ol
the other into curare solution. The parts of the
preparations not immersed should be kept moist with
normal saline solution. After several minutes mount
specimens in the myograph. Stimulate the nerves
and note :

(#) The relative reaction of gastrocnemii to indirect
stimulation.

(b*) Does this bear a resemblance to any previous ex-
periment ?

(V) How do results compare with those of previous
experiment?

(6) Stimulate the sayne muscles directly.
(#) Relative reaction?

(^) Taking this in connection with preceding experi-
ment, where have you proved that curare acts?
(V) How do experiments (5) and (6) compare with

experiments (3) and (4) ?

NOTE: — Failure in experiments (5) and (6) may result
from insufficient immersion of muscle in curare solution,
capillary attraction resulting in curare reaching muscle
supposed to be free from poison, and drying of parts not
immersed in solution. Of thesethe first is by far the most fre-
quent cause of failure, the sheath of the muscle rendering
the absorption of poison a slow process. It may be over-
come by making a few slight incisions in sheath, or inject-
ing a drop of the curare solution directly into the muscle.
Failure of experiment (2), and consequently (3) and
(4), may result from ligature around thigh being not tight
enough to prevent diffusion of curare into gastrocriemius.

LXV. Atropin.

1. Material. — 2 dogs; atropin sulphate; morphin sulph-
ate; chloroform (or ether); mask.

2. Preparation. — Make up following solutions; a strong so-
lution of atropin 0.4 grm. to 10 c. c.; a weak solution,
0.02 grams to 10 c. c.; morphin, 0.6 grams to 10 c. c.

Simply restrain dog " a." Fasten dog "b" to board.
Give hypodermically, 0.03 grm. morphin to dog " b,"
then anaesthetize him. Set up induction coil so as to
obtain interrupted current,
j. Experiments and Observations.

(1) Drop three drops of the stronger atropin solution
into one eye of dog "a," allowing them to drop in at
short intervals, and obstructing tear duct with pressure
of ringer.

(#) What is the nerve supply of the iris ?
(3) On what local elements may a drug act to produce

'alteration in size of pupil, and how ?
(V) Would a drug, acting centrally, though applied

to one eye, be likely to affect one, or both pupils ?
(//) Would a drug, acting locally, and applied to one

eye, be likely to affect one, or both pupils?
(e} Would a drug, acting locally on the pupils, but in-
jected into the circulation, and reaching the pupils
in this way, be likely to act on one, or both pupils ?
(/) Are either or both pupils affected by atropin, and

if so, what effect is produced ?

(^) Does atropin act locally or centrally to produce
its effect on the pupil ?

PHARMACOLOGY. 291

(-£) Can you devise an experiment that would positively
answer question " g." ?

(2) Expose the vagus of dog "b" (see pp. 110-111).
Stimulate it with weak induced current, using shielded
electrodes.

(0) What is the function of the cardiac fibers of the

vagus?
(^) How, therefore, would you expect stimulation of

the vagus to affect rate and rhythm of the heart

beats ?
(<r) How would you expect severing of the vagus to

affect the rate and rhythm of the heart beat ?
(//) How do you actually find the rate and rhythm of

the heart beats affected by stimulation of the vagus?

(3) Count the pulse, then give 5 mgrm. atropin hypo-
dermically.

(a} Count the pulse at short intervals after the injec-
tion of atropin for at least 30 minutes, or until its
rate is markedly affected.

(<£) What is the effect of atropin on the rate of the
pulse ?

(/) Could atropin produce this effect by acting on the
vagus center? On the vagus fibers ? On the vagus
terminations in the heart? On the heart muscle
direct ?

(4) After the pulse rate has been markedly affected by
atropin stimulate vagus as before, using shielded
electrodes.

(0) What is the effect on the rate of heart's action?

(£) Compare this result with that obtained in experi-
ment (2).

(<:} Had atropin acted solely by depressing the vagus
center would we have found a difference in results

2 LAB OR A TOR Y G U1DE IN PH YSIOLOG V.

in stimulating vagus nerve before and after its ex-
hibition ?
(*/) Had atropin acted on the accelerator apparatus

would there be a difference in such results ?
O) If now, on stimulating the heart muscle directly,

you obtained a normal physiological effect, to what

elements have you limited the possible action of

atropin ?
(/) Basing your opinion on the experiments you have

performed, to what elements have you limited the

possible action of atropin?
(5) Further general observations.
(0) Take temperature per rectum.
(£) Note condition of visible mucous membranes,

with regard to their secretions.
(V) If dog can be kept until next day, note size of

pupils.

LXVI. Pilocarpin.

/. Material.

1 rabbit; 1 dog; hydrochlorate of pilocarpin; sulphate of
morphin; sulphate of atropin; chloroform.

2. Preparation.

Make solution of pilocarpin, 50 mgrms. to 10 c.c.; atro-
pin, 0.02 grm. to 10 c.c. ; morphin 0.6 to 10 c.c.

Do not fasten the rabbit to the holder. Fasten the
dog to the dog board, after giving preliminary hypoder-
mic injection of 0.03 grms. morphin.

j. Experiments and Observations.

(1) Give, hypodermically, 0.02 grm. pilocarpin to
the rabbit.

(a) Record symptoms as they arise, especially as
regards:

(I) Secretions;

(II) Pulse rate;

(III) Size of pupil;

(IV) Temperature.

(£) Formulate the total effect of pilocarpin upon the
animal.

(2) After morphinizing the dog, fasten it firmly to the
dog-board and lightly anaesthetize; expose both vagi.

Count the pulse. Give a subcutaneous injection of
0.03 grms. pilocarpin. After salivation has become
profuse count the pulse again.

How does pilocarpin affect the pulse rate ?

(3) Now sever the vagi.

(a) How does the severing of the vagi affect the nor-
mal animal? (See page 109. )

294 LABOR A TOR Y G VIDE IN PH YSIOLOG Y.

(£) How does it affect an animal poisoned by pilocar-
pin?

(/) Could pilocarpin alter the effect produced by
severing the vagi if it acted on the proximal side of
the point at which the vagi were cut? On a point
beyond that at which they were cut?

(//) Could the pilocarpin alter the effect normally
produced by severing the vagi, by acting on the
cardiac sympathetic?

(<?) Enumerate the possible points at which pilocar-
pin may act to produce the effects observed.

(4) Give to the same dog 5 mgrms. atropin, hypoder-
mically.

(a) Is the rate of heart-beat altered ?

(£) Where does atropin act to produce alteration in

rate of heart-beat (see atropin.)
(c) Does atropin antagonize the action of pilocarpin

in this experiment?
(</) To what elements have you limited the probable

action of pilocarpin ?

(5) General observations.

(0) Compare the action of pilocarpin with that of
atropin, throughout the range of action observed.

(<£) Is atropin a physiological antagonist to pilo-
carpin ?

LXVII. Strychnin.

/. Material. — One dog; two frogs; sulphate of strychnin.

2. Preparation. — Make a solution of sulphate of strychnin
0.01 gm. to 10 c. c.; also concentrated solution, 0.2 gm.
to 10 c. c. Pith frogs. Do not fasten the dog to the
dog-board. Set up electrical apparatus to obtain tetaniz-
ing current.

3. Experiments and Observations.

(1) Hypodermic injection of 0.01 gm. strychnin to the
dog.

(a) Record the condition before, and symptoms as
they arise after exhibition of the drug, especially
with reference to :

(I) Muscular activity. Describe convulsions.

(II) Respiration. How affected by reflexes.

(III) Circulation. Rapidity and rhythm of heart.

(IV) If death occurs, which stops sooner, the
circulation or respiration ?

(<£) Formulate results.

(2) Ligate thigh of frog, except sciatic nerve, at junc-
tion with body. Sever all structures except nerve
and femur, just below ligature. Separate cut surfaces
with rubber tissue to prevent diffusion of the drug.
Turn the frog over and make a median abdominal
incision. Pressing viscera aside, pick up the sacral
plexus of nerves going to the uninjured leg. The
sacral plexus may be readily recognized, lying on each
side of the median line. Pass a thread loosely around
the nerves, so as to quickly find them when wanted.
Inject into dorsal lymph space, 0.0001 gm. strychnin.

295

296 LAB OR A TOR Y G UIDE IN PHYSJOL Of Y.

(a} What part of the frog is reached by the poison ?
What part protected from it? Illustrate by diagram.

(£) Were strychnin a convulsant through its action
on the sensorium, would the legs be equally con-
vulsed ? If it acted on the spinal cord ? If it acted on
the motor nerves? If it acted on the muscles directly?

(c) Are both legs convulsed ?

(d) To what parts in the reflex arc have you limited
the action of the strychnin ?

(3) Using as a guide the thread formerly passed around
it, pick up sacral plexus and sever it high up.

(#) Does the strychnin reach the motor nerve and
muscles of uninjured leg ?

(£) If strychnin were a convulsant through its action
on either the motor nerves or the muscles, or both,
would the uninjured leg still participate in the con-
vulsions ?

(c) Demonstrate that muscles, sciatic nerve and sacral
plexus below the point at which it was severed, are
still intact, by stimulating distal portion of latter.

(d) To what elements of the reflex arc have you lim-
' ited the possible action of strychnin ?

(4) Expose the heart of a frog and ligate the aortae at
the base. Operation as follows :

Freely expose sternum by -f- shaped incision and laying back of
flaps. Remove lower half of sternum with scissors, taking care not to
injure vessel in abdominal wall which comes just to tip of sternum.
Freely incise exposed pericardium, bringing heart into view. Grasp
apex of heart with forceps, taking care not to use force enough to cut
through ventricular wall, and draw heart down and forward. This gives
ready access to bulbus arteriosus and aortas. With an aneurism needle
pass fine thread around latter, taking care not to injure auricles, and
ligate.

With scalpel cut through occipito-atlantoid membrane, from side to
side, and bend head forward. Remove posterior wall of upper end of

P HARM A CO LOG Y. 297

spinal canal by inserting smaller blade of strong scissors into spinal canal
and cutting, taking care not to injure cord. Allow a drop of the concen-
trated solution of strychnin to fall directly upon cord; or with fine
hypodermic needle inserted 1.5 cm into the arachnoid space inject two
drops of the solution.

(a) What effect has ligation of the aortae on the cir-
culation ?

(£) Would stoppage of the circulation prevent the
drug from reaching the peripheral terminations or
trunks of the sensory nerves? Motor nerves? Muscles?

(/) Where then, must strychnin act to produce the
observed symptoms ?

(//) Would cessation of the circulation delay the ac-
tion of strychnin on the cord by slowing the rate of
its absorption by the latter ?

(5) After observing results in experiment (4), destroy
first the upper then the lower portion of the cord, by
passing a wire down the spinal canal.

(a) How does destruction of the upper part of the
cord affect the convulsions ?

(b) What is the result of the destruction of the en-
tire cord ?

(r) Do the results agree with those of previous ex-
periments ?

NOTE : — Destruction of the upper part of the cord
during the preparation of the animal may take
place; if so, the upper limbs will not take part in
the convulsions.

(6) Further observations and comparisons.

(a) Compare the general effects of strychnin and
curare in the dog.

(3) Compare results obtained in experiments consist-
ing of ligating the thigh of a frog except the sciatic
nerve, and injecting, in the ono case strychnin, in
the other curare.

LXVIII. Veratrin.

/. Material. — Sulphate of veratrin; 1 dog; 3 frogs.

2. Preparation.

Prepare a solution of veratrin, 50mgrms, to 10 c.c. Pith
frogs. Restrain dog, but do not fasten to board. Set
up myograph and induction coil, the latter arranged
for single induction shocks.

3. Experiments and Observations.

(1) Give a subcutaneous injection of 15 mgrm. veratrin
to the dog.

(a) Describe symptoms as they arise.
(£) Summarize.

(2) Place thread around the sacral plexus of the pithed
frog so as to easily find it, as described under
strychnin. Inject 0.003 gms. veratrin into dorsal lymph
space.

(#) Describe symptoms referable to rexflexes.

(£) Note particularly the difference between a forcible

contraction and a prolonged contraction.
(3)( Sever the sacral plexus around which the thread
has been passed.
(#) How do the contractions of the legs in response

to direct stimuli compare ?

(£) Has severing the sacral plexus altered the dura-
tion of the contraction of the muscles supplied ?
(V) If veratrin still produces its typical effects, to

what elements in the reflex arc have you limited its

action ?
(d) Compare the effect of severing the sacral plexus

in a frog poisoned with veratrin with that in a frog

poisoned with strychnin.

298

PHARMACOLOGY. 299

(4) Ligate the thigh of a pithed frog at the junction
with the body, not including in the ligature the sciatic
nerve. Sever all tissues just below the ligature ex-
cept the nerve and the femur. Carefully separate
the cut surfaces with rubber tissue so as to prevent
diffusion of the drug. Inject 0.003 gm. veratrin into
the dorsal lymph space.

(#) By means of a diagram show the distribution of
the poison.

(£) Compare the contractions of the legs, noting par-
ticularly the difference in the duration rather than
the difference in the force of the contraction.

(V) If the protected limb reacts normally to stimuli,
to what elements in the reflex arc have you limited
the possible action of veratrin?

(</) Compare results with similar experiment with
strychnin.

(5) From the frog used in experiment (4) make two
gastrocnemii preparations. Fasten in myograph by
means of femurs, and stimulate them directly, making
tracings of contractions.

(a) Compare tracings.

(/>) To what elements have we limited the action of

veratrin ?
(c) Suggest an experiment which would limit the

action to one element.

(6) Very cautiously sniff veratrin. Describe the sensa-
sation.

(7) General observations and comparisons.

(a) Review your notes on the action of curare, strych-
nin and veratrin upon the reflex arc.

(£) How would you prove that a drug paralyzed by
its action on the spinal cord?

(<:) How would you prove that a drug destroyed reflex
activity by its action on some part of the sensorium?

LXIX. Digitalis.

1. Material. — Tr. digitalis ; sulphate of morphin ; sodic
chloride; chloroform ; two dogs; one frog ; sodic sul-
phate (^2 sat. sol.).

2. Preparation. — Make solution of morphin, 0.6 gm. to
10 c. c. Sodic chloride, 0.06 gm. to 10 c. c. Pith
frog. Morphinize dogs, using 0.03 gm. and chloroform
them previous to operation. Set up induction coil so as
to obtain tetanizing current, having contact key in
primary circuit. Prepare kymograph for tracing.

3. Experiments and Observations.

(1) Fasten a dog firmly to the dog board and lightly an-
aesthetize. Expose the vagus. Count the pulse. Using
shielded electrodes and separating secondary from
primary coil, find a current just weak enough not to
affect heart when applied to vagus. Now inject O.G
c. c. tr. digitalis subcutaneously. After waiting at
least 20 minutes, in the meantime using no anaesthetic
except a repetition of the morphin if necessary, and
keeping the wound closed after moistening with saline
solution, stimulate the vagus with same current that
before the exhibition of digitalis was unable to affect
the heart.
(a) What is the function of the cardiac fibers of the

vagus?
(£) What result is produced by the stimulation of

these fibers in the normal animal?
(f) Does digitalis increase or decrease the excitably

of the vagus?
(</) With the stimulus applied to the vagus fibers and

PHA KM A CO LOG Y. 301

the cardiac fibers carrying impulses centrifugally,
could this altered excitability be due to central
action of the digitalis?

(2) After morphinizing dog, fasten firmly to dog board
and lightly anaesthetize; expose femoral artery.

Having placed mercury in the manometer, and
filled the cannula, connecting tube and short arm of the
manometer with ^ saturated sodic sulphate solu-
tion, to prevent clotting, insert the cannula into the
femoral artery, in a direction toward the heart. There
must be no air bubbles in the apparatus at any point.
Let the float, carrying the tracing point, rest on the
mercury in the long arm of the manometer and record
on the revolving drum.

The anaesthetic should be discontinued as soon as
the cannula is inserted into the femoral artery. Take
normal tracing. Now give the dog 0.6 c. c. tr. digitalis
hypodermically.

(0) Watch effect on elevation of float, making trac-
ings at short intervals.

(^) What elements enter into arterial tension ?
(c) How does a " high tension " tracing differ from

a "low tenison" tracing?
(</) How do changes in tension affect the elevation

of the tracing above the abscissa ?
(e) What effect has digitalis on arterial tension ?

(3) Having firmly fastened a pithed frog to frog board
with web stretched over a cover glass fastened into a
hole in the board by means of sealing wax, focus the
microscope upon a certain arteriole in the field, and
measure its diameter with an eyepiece micrometer.
Now inject into dorsal lymph spaces 0.3 c. c. tr. digi
talis and measure same arteriole

2 LAB OR A TORY G UIDE IN PH YSIOL OGY.

minutes. Keep the web moist with normal saline
solution.

(#) What change occurs in the diameter of the arteriole?
(£) What effect would you expect this to have on ar-
terial pressure ?
(V) Would its action on the arterioles help to account

for its effect on arterial pressure?

(4) Comparisons. — Compare digitalis and atropin with
regard to (a) their effect on the rate of the heartbeat,
(b) Their effect on the irritability of the vagus.

LXX. Aconite.

/. Material. — Tr. aconite; sulphate of atropin; 1 dog; 1
frog; sphygmograph.

2. Preparation.

Make solution of atropin, 0.02 grms. to 10 c.c. Pith
frog. Do not fasten the dog to the dog board.

3. Experiments and Observations.

(1) Give 1 c.c. tr. aconite hypodermically to the dog.
Record symptoms as they arise.

(2) Fasten the pithed frog on its back to the board.
Count the heart beats, exposing heart, if necessary.
Now give 0.2 c.c. tr. aconite subcutaneously. What
effect has aconite on the pulse rate ? (To obtain satis-
factory results observations must be made at short
intervals, for from 30 to 60 minutes.)

(3) After the pulse has been markedly affected, inject
into the dorsal lymph spaces 0.0002 grm. atropin.
Does atropin affect the pulse rate after administration
of aconite?

(4) Take a sphygmographic tracing, of the radial
pulse of a student. Note the pulse rate. Administer,
by mouth, 0.2 c.c. tr. aconite and 0.06 c.c. every 10
minutes until action on pulse is noticeable. Repeat
tracing and counting of pulse at short intervals.

(a) How does aconite affect blood pressure?

(^) How is the rate of the heart's action affected?

(<:} What subjective sensations are produced ?

(5) Comparisons. — Compare aconite and pilocarpin with
regard to their action on the gastro-intestinal system.

APPENDIX. A.

APPENDIX A.

i. Normal saline solution.

This solution, or as it is also called normal salt solu-
tion or physiological salt solution, is so much used in the
physiological laboratory that it should be made in consid-
erable quantity and always easily accessible.

Formula:

Common salt (C. P.) 30 gms.

Distilled water 5 L.

It is convenient to keep the solution in a siphon bottle.
It is thus protected from dust and evaporation, and is al-
ways easily accessible. See Fig. 53.

FIG. 53.
FIG. 53. Siphon-bottle for normal saline solution.

2. Frog boards.

There is probably no more satisfactory or economical
frog board than a piece of dressed soft pine 15 cm. by 30

307

308 LABORATORY GUIDK IN PHYSIOLOGY.

cm., and one or two centimeters in thickness. Some prefer
to use cork boards which come in pieces 10 cm. by 25
cm. and V^ cm. in thickness.

3. The physiological operating case.

A convenient case, and one which will be sufficient
in the simple experiments presented in this book, contains
the following instruments :

1 medium scalpel,

1 small scalpel with narrow blade,

1 medium scissors,

1 microscopic scissors,

1 medium dissecting forceps,

1 microscopic forceps, with curved, serrated jaws,

2 serre fine forceps, with stiff spring and serrated jaws,
1 groove director and aneurism needle,

1 silver probe,

1 blunt needle, for pithing frogs,

2 dissecting needles.

The case may be of leather or leatherette. Such a
case may be used nearly as much in the histological as in
the physiological laboratory.

4. Galvanic cells.

For general use in the physiological laboratory there
is probably no galvanic element superior to the Daniell
cell (named after Prof. J. F. Daniell, of King's College,
London). Much the most convenient and economical
size is the quart or liter cell whose porous cup measures
5-6 cm. in diameter and 10 to 12 cm. in height. If more
current is needed than is furnished by one of these cells it
is very easy to join two or more of them into a battery.

In large laboratories it will be found expedient to de-
vote an old table to the galvanic cells. This table should

APPENDIX A. 309

be provided with a supply of copper sulphate and of 10%
sulphuric acid in large siphon bottles similar to the one
suggested for normal salt solution (Fig. 53), except that
instead of the short tube for equalizing pressure one may
insert a filter through which at the end of the laboratory
period the student may return the liquids.

The accumulation of zinc sulphate in the acid makes
the renewal of the acid necessary from time to time. The
deposit of metallic copper upon the copper plate reduces
the copper sulphate solution in strength. It may be kept
replenished by an excess of crystals of that salt in the large
supply jar. A very practical method of amalgamating the
zinc plates is to have a jar containing 10% sulphuric acid
with mercury in the bottom; as the plate is immersed the
acid attacks it and cleans it so that the mercury readily
clings to it and may be rubbed over the surface with a
cloth. Another method, which is preferred by some, is as
follows: Dissolve 75 gms. of mercury in a mixture of 150
c. c. strong nitric acid and 300 c.c. strong hydrochloric
acid. Add to the solution 450 c.c. of strong hydrochloric
acid. Keep this amalgamating solution in a ground glass
stoppered jar. To amalgamate a zinc plate one need only
dip it for a few moments into the solution, remove it, rinse
under the spigot and rub with a cloth.

At the end of each laboratory period the cells should
be emptied, the zinc plates rinsed and drained, and the
porous cups left in a tray of running water, or at least in
a considerable excess of water.

5. To curarize a frog.

In experiments on the irritability of muscle tissue it is
necessary to, in some way, suspend the activity of the
irritable nerve fibers which are supplied to every muscle.
In certain other experiments it may be advisable to thus

310 LABOR A TOR Y G UIDE IN PHYSIOLOG Y.

remove the influence of the nervous system. Curara—
also spelled curare, curari, urari, and woorara, woorari,
wourali, etc., — an arrow poison used by the South Amer-
ican aborigines, is the means usually employed to accom-
plish the end desired. The way in which curare exerts its
influence, is made the subject of study in another place.
Make a 1% solution by pulverizing 1 gramme of commer-
cial curare, and dissolve it in 100 c. c. of distilled water.
It need not be filtered unless intended for use with a
hypodermic syringe. If kept in a ground glass stoppered
bottle, in a cool place, it will retain its efficiency for
months.

The most convenient method of curarizing a frog is to
inject with a narrow pointed pipette, 1-3 drops of the
solution, through a minute ventral cutaneous incision.

The drug will begin to take effect in a few minutes.
The maximum effect may be delayed some time.

6. To prepare the kymograph for work.

Remove the cylinder, stretch a sheet of the prepared
glazed paper tightly upon the surface, place it upon such
a stand as the one shown in Fig. 54; set the drum to

FIG. 54.
FIG. 54. Drum support for use in smoking the kymograph drums.

rotating and bring the triple gas flame under the drum. In
a few moments it will be evenly covered with a film of

APPENDIX A. 311

carbon which is as sensitive to touch as a photographer's
plate is to light.

7. A fixing fluid for carbon tracings.

Gum damar 160 gms.

Benzole q. s. ad 2000 c.c.

If this solution be kept in a large museum jar in the
laboratory, the removed sheet bearing the tracings may be
dipped in toto or it may be subdivided and dipped in sec-
tions. Let the tracing be lowered quickly into the solu
tion and after a few seconds taken out and drained. If it
be now laid upon a sheet of filter paper — or a newspaper —
it will be dry in a few minutes.

8. The cardiograph.

Any laboratory will have different forms of cardio-
graphs for demonstration purposes, but not every labora-
tory is able to afford numerous duplicates.
An expert tinsmith will make the tam-
bour pans at very moderate cost, and the
student can do all the rest. Pans may
be made of two sizes No. 1, diameter
5 cm., depth 4 mm., outside diameter of
tube 3 to 4 mm., length of tube 3 to 4 cm. No. 2, dia-
meter 4 cm., depth 3 mm., tube as in No. 1, see Fig. 55,
To make the cardiograph : — Take a tambour pan No. 1,
stretch thin sheet rubber — the dentists' "rubber dam," and
sold as such by dealers — across the pan and tie in place
with thread, A few drops of sealing wax will keep the
thread in place after it is tied. Mount the tambour as
follows : From any well seasoned, close-grained hard-
wood in boards, about 1 cm. thick, cut small triangular
pieces about 10 cm. on a side. In the center of each tri-
angle bore a hole to receive a medium sized cork (about

312 LABOR A TOR Y G UIDE IN PHYSIO LOG Y.

1.5 cm. in diameter) the upper edges of .the triangle
may be beveled and each corner may be furnished with a
leg by screwing into each corner from the lower surface,
a round headed screw, leaving about 1 cm. of the screw
out to serve as the leg. If the class is large, the demon-
strators should prepare these tambour boards in advance.
The tambour is mounted by fitting a cork to the hole
in the tambour board, boring the cork and pressing the
tambour tube through the
hole from below upward. Fix
a button of cork to the mem
brane with sealing wax. The

completed cardiograph will

, FIG. 5b.

present in section the rela-
tions shown in Fig. 56. As will be seen from the cut,
the position of the button may be varied by varying its
shape or by changing the adjustment of the tambour tube
in the cork. The cardiograph tambour is the receiving
tambour.

9. Tambours.

It is probable that no part of the laboratory equipment
is more in use than the various forms and adjustments of
the tambour. The possibilities of this device were first
brought out and developed by Marey, Director of the
Physiological Institute of the 6cole des Hautes Etudes
en Sorboune, Paris.

If the laboratory cannot afford to furnish at least one
pair of the Marey tambours to each table, recourse may
be had to such a device as that just described above under
the cardiograph. Such simple tambours when carefully
constructed prove most satisfactory.

To construct a recording tambour : Use a No. 2 tambour
pan, stretch the rubber less tightly than for the receiving

APPENDIX A. 313

tambour and mount similarly in a triangular tambour
board, omitting the screw legs. Make a recording needle
like the frog's heart lever, except that the foot, which rests
upon the middle of the tambour membrane, should pre-
sent a larger surface. The cork which forms the fulcrum
of the lever should be fixed to the tambour board in such
a position that the long arm of the lever is vertically above
a diameter of the tambour. Any change of pressure upon
the air in the tambour will cause the membrane to rise or
fall, thus producing in the tracing point of the lever a cor-
responding rise or fall, differing from that of the membrane
only in its greater extent. It is evident that if the tube of
the receiving tambour be joined to the tube of the record-
ing tambour through a thick rubber tube any movements
which affect the button of the first will be manifested by a
rise or fall of the lever which rests upon the second.

10. The stethograph.

In order to record graphically the movements of the
chest one may use various mechanical devices. The most
simple device, and a most effective apparatus, when only
the time relations and the character of the movements are
matters of concern, is the instrument which involves the use
of two tambours, a receiving and a recording tambour.
The latter is the one describedab ove, (9.)

A receiving tambour may be constructed especially for
this purpose as follows : Let a tinsmith construct, from
small brass wire, (^ — ^ mm. in diameter), spiral springs
which shall present the outline of truncated cones (See
Fig. 57 a), and fit inside the larger tambour pans.

If the student be supplied with tambour pans, spring,
"rubber dam," thread, sealing wax and cork, he may con-
struct his receiving tambour by placing the spring in the

314

LABORATORY GUIDE IN PHYSIOLOGY.

tambour pan, stretching the sheet rubber
over the spring, tying and sealing. The
now conical diaphragm of the receiving
tambour should be provided with a cork
button, and adjusted by passing its tube
through a horizontal hole near the end of
one of the wooden rods (see Fig. 18).
Connect the tambours by means of a small rubber tube.

FIG 57.

ii. The thoracometer.

If one wishes to measure the extent of the movements
of the thoracic walls the stethograph, for mechanical

FIG. 58.

FIG. 58. Receiving button for Thoracometer — an instrument for use in
quantitative determination of variations in thoracic diameters.

reasons too apparent to need enumeration here, affords, in
the height of the recorded waves, unreliable data. To
make a quantitative determination of the variation of any
diameter of the thorax requires the application of a differ-
ent principle. The following method has been success
fully used: Construct the apparatus shown in the accom-
panying cut, using for the spiral spring brass wire 1.5 to 2
mm. in diameter. The cone denned by the spring should
be 6 or 7 cm. across the base and should have an altitude
from the base to the contact surface of the hard rubber

APPENDIX A.

315

button of about 4 or 5 cm. It may be fixed to the hard
wood or fiber base with three staples and the base in turn
fixed, as indicated in the figure, to an iron rod about 1 cm.
thick by 30 cm. long. A hole is bored through the base in
the middle of the cone. A pulley whose plan and elevation
are given in Fig. 58 b and c, fastened to the under surface
of the base serves to change the direction of a cord which
is tied to a ring in the hard rubber button.

12. The belt=spirograph.

The apparatus here described was contrived to over-
come as far as possible the objections which may be raised

FIG. 59.

FIG. 59. The Belt-spirograph for quantitative determination of varia-
tions in chest girth.

to the previously used instruments for this purpose. Note
in the first place that the wide elastic belt will follow faith-
fully every movement of the chest wall, not sinking into
the soft tissues during inspirations; second, the almost in-
elastic fish cord will transmit the movement of the thorax
much more accurately than elastic air inclosed within
elastic conductors.

The 59 a, b and c figures show the construction of
the belt spirograph: (a) The 2-3 cm. wide, elastic belt

316 LABORATORY GUIDE LV PHYSIOLOGY.

showing location of pulleys, (b) A section of thorax
showing belt in position. The cord is tied to an eye in
pulley No. 1, passes around the circuit of pulleys to No. 1
again, thence over two or three pulleys which serve to
change the direction, bringing the cord finally to a record-
ing lever adjusted as described for the thoracometer.
(c) Showing an enlarged view of a pulley. The brass
base of each pulley is fixed to a piece of sole leather 4 or 5
cm. long by 3 or 4 cm. wide. Copper wire, riveted at the
points r and r', clasps the elastic belt and holds the pulley
in position.

13. The stethogoniometer.

Various methods have been employed for determining
the curvature of the chest wall. Even so simple a method

FIG. 60.

FIG. GO. The Stethogoniometer used in graphically recording any
perimeter of the thorax.

as the taking of several diameters will reveal approx-
imately the general conformation of the chest wall. A
graphic method has this to recommend it : that a glance at
an outline of any circumference of the thorax reveals more
than any amount of time expended in the study of numer-
ical data. Of all the graphic methods used by the writer
the one here described seems most simple and practical.
The accompanying figure (Fig. 60) shows the instrument,
which will be recognized as similar to a draftsman's pan-

APPENDIX A.

317

tograph. As used by the draftsman such an apparatus
enlarges figures by any multiple from 1 to 5 in linear di-
mensions, for that purpose the tracing stilus is placed at
a and the recording pen or pencil at b, while the point c is
fixed to the table. As used to trace the curvature of any
line in the body, the recording pencil is fixed at «, while
the point b is made to follow the curved surfaces under
observation. In this way records of one-fifth the linear
dimensions of the curve traced may be recorded. Such rec-
ords are compact and readily filed for subsequent reference.

\\

14. The pneo=manometer.

This instrument may be easily con-
structed in the laboratory. Take a piece
of heavy glass tubing of 7 to 9 mm. lumen
and at least 160 centimeters in length.
Bend it as shown in Fig. 61. A covered
filter may be attached as shown in the
figure if there is any tendency for the
mercury to be thrown out.

15. The chronograph.

For many experiments, especially upon
the circulation or respiration, it is neces-
sary to trace upon the rotating drum, along
with the record of the circulatory or respi-

\ratory movement, a record of time in
seconds or known fractions thereof. In-
struments for this purpose are to be had
from the instrument houses.

If the student or demonstrator is in-
clined to construct his own chronograph

the accompanying figure and description
The Pneo-mano- \ *

meter. For test- may be of assistance to him. (See Fig.
ing pressure in Q^.']
forced respiration.

FIG 61.

318

LABORATORY GUIDE IN PHYSIOLOGY.

Materials and Construction. — (1) A soft iron electro-
magnet (m) with soft iron armature (a), as shown in
A. A machinist or electrician can construct these from
strictly pure, soft Swedish iron.

(2) No. 24 double silk covered copper wire, to be wound
as indicated in A (x to y). The wire should be wound
in three layers and when the winding is complete it
should present the appearance shown in Fig. 62 B, m'.

(3) From fiber board or from wood one may construct
such a lever and magnet support, as shown in Fig. 00
B. The lever (1) is pivoted at f; the block a' bears
the armature; the counterpoise (w) may be adjusted

FIG. 62.
FIG. 62. The Chronograph.

so as to make the part of the lever at the right of f
slightly heavier than that at the left, so that when no
current is flowing through the electro-magnet the
armature is lifted from the magnet.

(4) A check (c) rests upon an adjustable screw (s) and
limits the excursion of the lever.

(5) A straw may be fixed with wax to the end of the
lever and a tracing point (p) of parchment paper
slipped into the straw.

(6) The wires from the clock or the chronograph sys-
tem are connected at x' and y'.

APPENDIX A. 310

(7) The base may be clamped to a support and the

tracing point adjusted to any height or direction.
This simple chronograph may be made sufficiently deli-
cate to record ^-seconds accurately, though seconds or
half seconds will usually answer the purposes of the gen-
eral experiment. For very small divisions of a second the
tuning fork should be used.

To set up a simple chronograph. — Join the chronograph
and the contact clock or a metronome in continuous circuit
with a common Daniell cell. The clock makes contact
every second or fraction, the armature is drawn down by
the electro-magnet and thus records the time upon the
drum of a kymograph.

16. The chronographic system.

If many students are working at the same time and at
the same experiment in a laboratory, it is unnecessarily
costly in both money and space for each student or group
of students to be supplied with separate chronographic
clocks and batteries. One clock and a battery of several
cells can be employed to run ten or twelve chronographs.
Such a chronographic system is too simple to require ex-
tended description.

(1) Bowditche's interruption clock or Petzold's simple
contact clock may be hung in any convenient place in
the laboratory and brought into circuit with

(2) A battery, in series, whose strength must depend
upon the amount of external resistance to be overcome,
i. e., the number of chronographs in the system.

(3) The chronographs must be all in one general circuit
rather than upon branches from a primary circuit.

(4) A loop of the general circuit may pass to each
table and the chronograph inserted in the loop. It is
hardly necessary to remind the demonstrator that if,

320 LABORATORY GUIDE IN PHYSIOLOGY.

for any purpose, a chronograph be removed from a
table when the system is in operation, the general
circuit must be instantly completed by use of a con-
nector.

17. To prepare 10% hydrochloric acid, the acidum hydro=
chloricum dilutum of the U. S. P.

The concentrated, c.p., hydrochloric acid of a sp. gr.
of 1.16 contains 31.9 per cent by weight of HC1 gas. To
prepare 10% HC1, take 31.4 c.c. of the concentrated acid
and dilute with distilled water to 100 c.c. From this di-
lute HC1. 0.2% HClorO.1% HC1 or any other desired
strength below 10% may be readily obtained.

APPENDIX B.

APPENDIX B.

On the general plan of a course in physiology and the
equipment of a laboratory.

The following pages are reprinted from a report of the
committee on syllabus, representing tJie Association of Ameri-
can Medical Colleges. The committee was in session Feb.
/j'-/<?, 1896, Chicago.

The course in physiology.

The course in physiology should be continued through
two years and should be, in a general way, coordinated
with the course in comparative anatomy and general
biology and histology. By coordination in this connection
is meant the arrangement of the courses in such a way
that the student shall learn first the more fundamental and
general and then the more special. To teach the student
the physiology of the liver one year and the gross and
minute anatomy of that organ thenext year must be recog-
nized by all as an inversion of the logical order. To
teach the anatomy of an organ one year and its physiology
the next year puts the teachers of both these branches
at considerable disadvantage, and the chances are great
that the student will have a less clear comprehension of
the subject presented in this way than he would if the
interval elapsing between the study of the more general
branch and the more special branch be a short one.

Every course in physiology should be accompanied
by laboratory exercises in which the student may fami-

334 LABORATORY GUIDE IN PHYSIOLOGY. ,

liarize himself with the technique of the subject and may
demonstrate for himself the more fundamental facts of this
science. The laboratory exercises should be coordinated
with the recitations and demonstrations as far as it is pos-
sible to do so.

The first half of the first semester (eight weeks) should
be spent in a study of the physiology of the cell as il-
lustrated in unicellular plants and animals. While the
student is studying the morphology of the protococcus,
the yeast cell, the amceba and the paramcecium in the
biological course he may profitably study the physiology of
these organisms from such a text as, " The Cell" (Hert-
wig), and should repeat in the laboratory the experiments
mentioned in Hertwig's book. " Allgemeine Physi-
ologic " (Max Verworn, Jena, 1895) is a valuable help to
the instructor who is conducting such a course.

The second half of the first semester may be spent on
muscle-nerve physiology. Having already studied the
reaction of amoeba and paramcecium to electricity, and hav-
ing studied, in general histology, the structure of muscle
fibers and cells, and nerve fibers and cells; further having
made careful dissections of frogs and other vertebrate ani-
mals the student is in a position to comprehend and appre-
ciate the reaction of muscle tissue in response to varicus
direct stimuli and to indirect stimuli applied to the nerve.
The frog-heart and the "muscle-nerve preparation" are
most used for such experiments.

Beginning with the second semester or second half of
the first year the general subject of nutrition should be be-
gun. Whether one introduces this field of physiology
with the study of the circulatory system or of the digestive
system is a matter of little consequence. The problems
of the circulation being, for the most part, physical prob-
lems, would seem to justify the consideration of that sub-

APPENDIX B. 325

ject first, followed by the respiratory system, which pre-
sents simple problems in mechanics, physics and chem-
istry. The student, having in the meantime made some
progress in physiological chemistry, is able to comprehend
the general features of the chemical problems involved in
digestion, and should now enter upon a systematic consid-
eration of nutrition : 1, food and foodstuffs; 2, prepara-
tion of foods; 3, mastication; 4, deglutition; 5, salivary di-
gestion; 6, gastric digestion; 7, intestinal digestion; 8, ab-
sorption; 9, distribution; 10, assimilation or anabolism; 11,
katabolism and animal heat, and 12, excretion. This course
will probably consume the second semester of the first year
and a part or all of the first semester of the second near.
The remaining time allotted to physiology should be de-
voted to the physiology of the nervous system, the phys-
iology of the special senses, and the physiology of repro-
duction. All of these courses should be accompanied by
laboratory work.

After the student has completed the above required
courses he should be given an opportunity to elect special
courses in physiology during the second semester of the
second year and during the third year. Profitable elective
courses would be, for example: 1. Physiology of intra-
uterine life, following Preyer's " Physiologic des Embryos;"
2. Special problems in the physiology of digestion, follow-
ing Brunton in "Handbook for the Physiological Labora-
tory; " 3. Physical examinations of the blood, using hema-
tokrit, hemometer, corpuscle counter, micrometer and
staining methods; 4. Experimental physiology of the cen-
tral nervous system, following Cyon; 5. Physiological
psychology, following Wundt or Ladd. The instructor
may get much help from such works as Cyon's " Methodik
der Physiol. Experimente; " Gscheidlen's " Physiologische
Methodik;" Foster and Langley's " Practical Physiol-

326 LABORATORY GUIDE IN PHYSIOLOGY.

ogy; " Schenck's " Physiologisches Practicum; " Brunton
and Burdon-Sanderson's " Handbook of the Physiolog-
ical Laboratory;" McGregor-Robertson's "Physiological
Physics;" Langendorf's " Physiologische Graphik," and
Stirling's "Practical Physiology."

The organization and equipment of the department of
physiology.

Inasmuch as many of the colleges of the Association
have not yet established physiological laboratories, it is
thought well to give a few general hints on the subject.
The imposing equipments which one sees in the physiolog-
ical institutes of Europe, equipments which, in the
aggregate, have cost many thousands of dollars, over-
awe one and make one hesitate to advise the undertaking
of so great a task, so we are letting the years slip by with-
out establishing physiological laboratories. We must not
forget that the equipment of European laboratories is a
growth which has covered many decades; and further,
that it is really advisable to allow a department to grow,
collecting, in the course of a few years, an equipment
which is perfectly adapted to the wants of the institution
and to the special methods of the head of the department.
The committee strongly advises the early establishment
of physiological laboratories, even if an institution cannot
appropriate for the purpose more than $1,000 to start
with. If an institution can devote to this department a
well-lighted general laboratory room 36 ft. to 40 ft. square,
with two or three small rooms for instrument room, work-
shop and library, and can appropriate $1,000 to $1,500 for
the first equipment, then a laboratory fee of $5 annually
from each student who works in the department will, in
the course of a, decade, produce a sufficiently full equip-
ment for all practical purposes.

APPENDIX B. 327

At this point it may be well to give a hint as to the
organization of the department, as this determines largely
the character of the equipment and the number of dupli-
cations of each instrument.

The amount of personal supervision required by the
student in practical physiology is so great that it is in-
expedient to attempt to conduct large classes. A demon-
strator and one assistant demonstrator cannot properly
supervise the work of more than thirty students at one
time, even though each student be provided with a labora-
tory manual. In the organization and equipment here
planned let it be understood that the laboratory class work
in sections of thirty students each, and that each section be
subdivibed into ten divisions of three students each. Now,
experience in many laboratories has shown that a student
will accomplish practically as much in one laboratory
period of three hours as in two laboratory periods of two
hours each. The three-hour laboratory period promotes
economy both for the student and for the department.
Following this arrangement, two instructors would be able
to supervise the work of 180 students, meeting one sec-
tion of thirty students each day. With this allotment of
time each student would have three hours of laboratory
work each week during the year, which would enable him
to demonstrate for himself all of the fundamental princi-
ples of physiology. In the question of the choice between
(1) the condensation of 180 hours of laboratory work in
physiology into a period of sixty days with three hours per
day, and (2) the distribution of the same number of hours
over sixty weeks (two years^) with three hours per week,
and its coordination with theoretical work in physiology
and with the courses in gross anatomy and histology, we
would, without a moment's hesitation, decide in favor of
the latter plan.

328 LA BORA TOR Y G UIDE IN PHYSIO LOG Y.

If this general plan of organization be adopted, and if
the department wishes to provide for sections of thirty
students, working in ten divisions of three students each,
then the apparatus should be duplicated in tens. The fol-
lowing list of apparatus is suggested as a practical one
with which to make a beginning : *

EQUIPMENT FOR GENERAL LABORATORY WORK.

10 strong tables, 6 feet by 3 feet, $5 CO $ 50.00

10 kymographs, $3~> 350.00

20 Daniell's cells, quart size, $1.75 37.50

4 pounds of copper wire, No. 18 double cotton cover, 50c. . . . 2.00

}/2 pound copper wire, No. 24 double silk cover, $2 00 1.00

10 simple compasses (for detectors), 30c 3.00

10 contact keys, $1.25 12.50

10 Du Bois keys, $3.25 32.50

10 simple rheocords, $2.50 25.00

10 Du Bois Reymond induction machines, $17.50 175.00

10 Pohl's commutators, with crossbars, $4.50 45.00

10 pairs of tambour pans, $2.00 20 00

20 heavy-base stands, $1.00 20.00

Fixtures for same —

2 right angle clamp-holders, extra heavy $0.50

1 universal clamp-holder 0.75

1 extension ring (4 inches) 0.25

1 Muscle forceps, cork insulation 1.00

1 simple myograph 2.50

10 of each $5.00 50.00

10 Bunsen burners, 35c 3.50

10 bell jars, 80c 8.00

10 double valve rubber bulbs, large size, 50c 5.00

5 hasmometers (Fleischl's), $12.50 62.50

5 sphygmographs. $20.00 100.00

5 blood corpuscle counters (Zeiss), $17.50 87.50

*ln reprinting the following list the author has taken the liberty to
revise his earlier list as published in the report of the committee. As
revised it provides for a higher class of apparatus at a proportionately
higher price, but brings the aggregate down to the former estimate by
reducing the number of incidentals.

APPENDIX B. 329

General surgical appliances, forceps, shears, etc 25.00

10 pounds assorted sizes of glass tubing, 35c 3.50

Assorted sizes of soft rubber tubing 3.00

Rubber stoppers, assorted sizes, perforated 2.00

Corks and sheet cork 2.00

Cork borers, Files, for cutting glass tubing 2.50

2 gas generators, Kipp's, $3.50 7.00

Graduated cylinders, pipettes, flasks, bottles, beakers, etc 25.00

$1,16000

INSTRUMENTS FOR SPECIAL USE AND FOR DEMONSTRATIONS.

Detector $ 2.50

Galvanometer 50.00

Rheostat or plug resistance box of 12 coils 10.00

Metronome, mounted to make and break circuit 12.00

Contact clock 25.00

Tuning fork, electrically maintained, mounted for tracing. .... 25.00

Chronograph 10.00

Hsematokrit 25. 00

Plethysmograph 6.50

Quantitative balances 30 00

1 pair dog scales .*. 15.00

Laboratory balances 10.00

Mercurial manometer for blood pressure 10.00

Ludwig rheometers 15.00

Moist chamber 20.00

Muscle forceps 3. 50

Capillary electromometer (Kuhne's) 5.00

Du Bois-Reymond rheocord 25.00

Hot air motor 40.00

Still for making distilled water 15.00

Drying oven, 10x12, double wall 13.00

Apparatus for determining focal distances 2.50

Steel-calipers 5 00

Spirometer 10 00

Stethogoniometer, belt spirograph and pneomanometer 15.00

$400 00

This list might easily be extended to amount to several
thousand dollars, but it is intended here to include only
those instruments which seem necessary to start with.

380 LAB OR A TOR Y G VIDE IN PHYSIO LOG Y.

THE WORK SHOP.

Demonstrators and students can easily construct in a
shop, many pieces of simple apparatus, which if pur-
chased of some instrument house, would amount to many
times the cost of the material and would deprive students
of some very valuable experience. Frog, rat, rabbit and
dog holders may be made, the tambour frames may be
furnished with membranes and mounted as receiving or
recording tambours, cardiographs, or stethographs. All
writing levers, electrodes, etc., should be made by the
students. A room with bench and vice and $25 for car-
penter's and machinsts' tools would be an ample start.

A FEW NECESSARY CHEMICALS.

20 pounds CuSO4 $ 140

10 pounds H2SO4 75

5 pounds mercury 3.30

2 pounds kaolin (for electrodes, etc.) 10

1 dram of curare 1.25

5 pounds gum damar 1.25

20 pounds benzol 4.00

10 pounds chloroform (imported duty free) 5 00

10 pounds sulphuric ether (imported duty free) 3 00

5 pounds unmedicated surgical cotton at 25 cts 1.25

2 pounds sealing wax in sticks 1 .00

5 pounds plaster of Paris 50

5 gallons alcohol (90$)

1 gallon abs. alcohol

2 pounds sodium hydrate

2 pounds magnesium sulphate

2 pounds sodium chlorid (pure)

2 pounds glycerin

1 pound hydrochloric acid ,

1 pound nitric acid

1 pound ammonium hydrate

Drugs as listed under Pharmacology

About $35.00

APPENDIX B. 331

A WORKING LIBRARY OF PHYSIOLOGY.

Beside the laboratory manuals enumerated under the
"Course in Physiology," we mention a few journals and
general works that should be in every laboratory of physi-
ology : Hermann's " Handbuch der Physiologic"; Journal
of Physiology, ed., Michael Foster, Cambridge, England;
Pfliiger's, Archive f. d. gesammte Physiologie, Bonn, Ger-
many; Archivfur AnatomU and Physiologic ^ [physiol. part]
ed., Du Bois-Reymond, Berlin, pub., Veit & Co., Leipsig;
Ccntralbldtt fur Physiologic^ pub., France Dduticke, Leipsic;
Journal of Experimental Medicine [physiological part edited
by Bowditch, Chittenden and Howell], D. Appleton &
Co.; "Animal Physiology," Mills, D. Appleton & Co.,
1889; "Text-book of Physiology," Michael Foster, Mac-
millan, 188893;" "Human Physiology," Landois and
Stirling, Blackiston, Philadelphia, last edition; " Refrac-
tion and Accommodation of the Eye," Landolt, Lippin-
cott, Philadelphia, 1886; "The Frog," Marshall, London,
1894; "Anatomy of the Frog," Ecker, Oxford, 1889;
"The Cat," Mivart, Scribner, 1881; "Dissection of the
Dog," Howell, Holt &Co., 1888; "Anatomic des Hundes,"
Ellenberger & Baum, Berlin, 1891 ; " Dictionary of Medi-
cine," (4to), Gould, Blackiston, Philadelphia, 1895.

Beside these there should be recent representative
manuals of histology, general biology, embryology, chem-
istry and physics.

PHYSIOLOGICAL CHEMISTRY.

It has been taken for granted that the chemical prob-
lems of physiology will be assigned to the department of
chemistry. The equipment of that department makes such
a division of the subject highly advantageous. For years
urine analysis has been taught, usually in the second year
of the course in the department of chemistry. Many of

332 LABOR A TOR Y G UlDE IN PIIYSIOLOG Y.

the stronger institutions have long since expanded the sec-
ond year course in chemistry into a very creditable course
of physiological chemistry, beginning with an investiga-
tion of foodstuffs, following this with qualitative and
quantitative work on the chemistry of digestion, and de-
voting the last semester of the second year to the analysis
of urine. The best laboratory manuals on the subject are :
Long's " Laboratory Manual of Chemical Physiology,"
Colegrove& Co., Chicago, 1895; Stirling's "Practical Phys-
iology" (first part); Halliburton's "Essentials of Chemical
Physiology"' Longmanns, Green & Co., 1893. The phy-
siological library should contain also : " Text-book of
Chemical Physiology and Pathology," Halliburton, Long-
manns, Green & Co., 1891 ; "Physiologische Chemie,"
Bunge, Vogel, Leipzig, 1894 ; " Lehrbuch d, physiologisch,
Chemie," Neumeister, Gustav Fischer, Jena, 1893; "Phy-
siological Chemistry," Hammarsten, Wiley & Sons, New
York, 1893 ; " Physiological Chemistry of the Animal
Body, "Gamger, Macrnillan, 1893; "Chemical Physiology
and Pathology," Hoppe-Seyler.

APPENDIX C.

APPENDIX C.

It is proposed at this point to devote a few pages to the
illustration and brief description of the more important
instruments and glassware which go to make up a prac-
tical equipment for a physiological laboratory.

i. Physical Apparatus.*

l.'TH$ KYMOGRAPH. — The basis of the instrumentarium of the
physiological laboratory is the kymograph. It is in almost con-

FIG. 1. Kymograph.

*For the plates in this section I am indebted to the Chicago Lab-
oratory Supply and Scale Co., 29 West Randolph St., Chicago.

335

336

LAB OR A TOR Y G UIDE IN PH YSIOL OGY.

stant use in muscle-nerve physiology, in circulation, in respiration,
and in pharmacology. It must be portable, durable, accurate, read-
ily adjustable as to speed and height of drum. All of these quali-
ties, together with reasonable cheapness, are possessed by the kym-
ograph illustrated in the accompanying figure. This instrument
was designed by Mr. C. H. Stoelting, of Chicago, for use in the
physiological laboratory of the University of Chicago. It is now
used in the University of Michigan, Northwestern University, Mas-
sachusetts Institute of Technology and the State Universities of
Illinois, Texas and Colorado, in Rush Medical College, and the
Detroit Medical College.

The height of the instrument is 55 cm.; weight 15 ko. The
drum is propelled by a clockwork, which is under perfect control
of the operator.

FIG. 1a.
FIG. a. Drum supporter with drum and burners.

2. THE MYOGRAPH. a. The spring myograph, modified from Du
Bois Reymond's. b. Simple myograph as used in the physiological
laboratory of the Northwestern University, and shown in Fig. 2.
c. The crank myograph.

APPENDIX C.

387

FIG. 2.

3. THE CHRONOGRAPH time-marker. Figure 4 shows Dr. Lingle's
modification of Pfief s single chronograph.

FIG. 3.

338 LABORATORY GUIDE JN PHYSIOLOGY.

4. THE MAREY TAMBOUR. -See Fig. 4.

FIG. 4.
5. THE POHL COMMUTATOR. See Fig. 5.

FIG. 5.

6. THE INTRODUCTION COIL OR INDUCTORIUM. Figure 6 shows
DuBois-Reymond's instrumen). Ludwig's instrument consisted in
changing the axia of the coils to the vertical position and counterpoising
the secondary coil. The DuB-R. instrument, or some modification of it,
is in more general use, and is satisfactory.

APPENDIX C.

339

FIG. 7.

FIG. 6.

7. THE MUSCLE FORCIPS. a. Figure 8 sfcows a fine brass instru-
ment with insulated jaws and a binding post. b. A simpler and cheaper
form, with cork insulation, and without the binding post, answers all
ordinary purposes.

8. THE DETECTOR, or low resistance galvanometer, is shown in
Figure 8.

8a. THE GALVANOMETER, a, Eblemann's universal; It. Rosenthal's
physiological.

340

LABORATORY GUIDE IN .PHYSIOLOGY.

FIG. 10.
10. THE COMPENSATOR. Ludwig's instrument is shown in figure 10.

FIG. 11. FIG. lla.

11. BATTERIES, a. The Daniell cell, or element, is shown in fig-
re 11. b. The Bichromate cell — see figure lla.

APPENDIX C.

341

FIG. 12.

12. THE RHEOCORD. h. Dubois-Raymond's Rheocord. b. The
simple rheocord as shown in figure 12. c. The Oxford rhecord.

FIG. 13.

13. ELECTRODES. Figure 13 shows: a. Hand-electrodes of insu-
lated copper or platium wires for use with induced currents, b. Non-
polarizable electrodes, variously constructed. For description see text.

342

LABORATORY GUIDE IN PHYSIOLOGY.

FIG. 14.

FIG. 14a. FIG. 14b.

FIG. 14c.

14. BINDING POSTS. Various forms are shown above.

15. BINDING CONNECTORS. Constructed of brass and in varying
forms.

FIG. 16.

16. KEYS. a. DuBois-Reymonds key
b. The mercury key, as shown in figure iCa.
(Fig. 12K). d. The Morse key.

FIG. 16a.

with knife-edge contact.
c. The spring contact key

APPENDIX C.

343

L -

FIG. 17.

FIG. 17a.

FIG. 17b.

17. ANTHROPOMETRIC INSTRUMENTS. These are various and consist
of scales, meter tape, calipers, dynamometers, spirometer, etc., etc.
Fig. 17 shows the belt-spirograph used to make a quantitative deter-
mination of variations of chest girth. Fig. 17a shows the pneo-manom-
eter for testing forced respiratory pressure. Fig. 17b shows the
stethogoniometer, for making a graphic record of the chest perimeter.

344

LABORATORY GUIDE IN PHYSIOLOGY.

FIG. 18.

FIG. 19.

18. STILL. For making distilled water.

19. SUPPORT. Special pattern for physiology, with extra heavy
base length 50-75 cm., weight 2% Ko.-4^ Ko.

FIG. 20.

20. DRYING OVEN, with double wall 10 in. by 12 in. May be used
for incubator in experiments in digestion.

APPENDIX C.

II. Chemical Apparatus.* *

345

27. Analytical Balance, Becker's short beam, for a charge up to
100 g. in each pan. Sensitive to ^ mg. with rider apparatus.

28. Analytical weight, Becker's, 100 g. down.

- *For the plates in this section I am indebted to Richard & Co., 108 Lake St.,
Chicago.

346 LABORATORY GUIDE IN PHYSIOLOGY.

FIG 29a.

FIG. 2(Jb.

29a. Balance for laboratory work. Capacity, 2 pounds. Sensitive
to 1-20 grain.

29b. Weights 500 g. down, in polished block.

APPENDIX C.

347

• O

FIG. 30. FIG. 31. FIG. 32.

FIG. 33.

FIG. 34. FIG. 35.

30. Gay Lussac's burette, on wooden base, 25 c. c. in 1-10.
31a. Mohr's burette, w. pinchcock, 50 c. c. in 1-5.
31b. Mohr's burette, w. pinchcock, 100 c. c. in 1-5.

32. Graduated cylinders with lip, double graduation, 10 c. c., 50
c. c., 100 c. c., 250 c. c , 500 c. c., 1,000 c. c. and 2,000 c. c.

33. Graduated cylinders, stoppered, 100 c. c., 500 c. c. and 1,000
c. c.

34. Volumetric flask, 1,000 c. c.

35. Bottle for mixing, glass stoppered, 250 c. c., 500 c. c., l.OOOc. c.

348

LABORATORY GUIDE IN PHYSIOLOGY.

FIG

FIG. 37.

FIG.

36. Evaporating dishes in nests of 9, from 2 oz, to 20 oz.

37. Evaporating dishes, best German porcelain, heavy rim, nests
of five, from % to 1 gal.

38. Flasks, vial mouth.

FIG. 39.

39. Beakers, plain1 3 oz. -50 oz.

40. Beakers/Griffin, lipped, 5 oz.-64 oz.

FIG. 40.

APPENDIX C.

349

FIG. 41.

FIG. 42.

41. Glass fupnels, best German, 2 in. to 8 in.

42. Glass funnels, ribbed, 3% in. to 8 in.

43. Liter Erlenmeyer flasks, Jena glass.

FIG. 44.

FIG. 45.

44. Calcium chloride tubes, Schwarz,4-4.

45. Potash bulbs, Geissler's, with drying tube.

46. Woulf-bottles, 1 pint size and 1 qt. size.

FIG. 43.

FIG. 46.

Of

. .. S ^K.. . . .

J~ ! B (-• < A R ' ,

-• • - --•

350

LABORATORY GUIDE IN PHYSIOLOGY.

FIG. 47.

FIG. 48.

47. Bell glasses, low form, with knob, 6 in. diam.

48. Bell glasses, tall form, with knob, iy2 in. diam.

49. Bell glasses, open top, 6 in. diam.

FIG. 49.

FIG. 50.

FIG. 51.

FIG. 52.

50. Bell glass, open top, with tubulure at side, l/2 gal.

51. Bottles, extra wide mouih, 4 oz. to 16 oz.

52a. Bottles, mushroom, glass stopper, narrow mouth, 4 oz. to
16 oz.

52b. Bottles, mushroom, giass stopper, narrow mouth, 16 oz.

APPEFDIX C.

351

I

FIG 53.

FIG 54.

53. T-tubes.

54. Y-tubes.

55. Kipp's gas generator, 1 qt.

56. Thermometers, 150 degrees C.

FIG. 55

FIG. 56.

INDEX.

Abreast, arrangement of cells. . 35

Absorption 189

Accommodation , . 216

range of 238

Acetic acid in gastric digestion. 173

Aconite 303

Acuteness of vision 232

Adaptation of eye for direction. 219

for distance 216

Adipose tissue, action of gastric

juice on 172

Age, effect on range of accom-
modation 211

Albumin, preparation of acid

albumin 162

preparation of egg alb 161

Alcohol, effect on ciliary motion 22

Amalgamation of zinc 27

Amperes, unit of current 31

Amplitude of convergence 241

Amylolytic ferment 187

Anaesthesia Ill

Anelectrotonus 76

Anode 28

Anode Pole, influence of 51

Anthropometric data 127

Appendix A 307

Apex beat 91

Apparatus for determining focal

distances 202

Arterial pressure 1 04

Astigmatism 237

Atropin 290

Average vs. median value 128

Batteries 308

grouping 34

Belt spirograph 315

spirograph 118-121

Bile pigments, Gmelins test for. 186
Bile, preliminary experiments

on 185

Biuret test 1(54

Binocular fixation 220, 242

Blind spot 223

calculate size of 223

map out 223

Blood pressure, influenced by

digitalis 301

laws of 102

Blood, examination of fresh... 259

Blood corpuscle counter 261

Bone marrow, study of 281

Break induction shock 71

Bread, action of saliva upon . . . 158

Brush electrodes 52

Calipers 124

Capacity of Lungs 124

Carbon-dioxide gas, effect on

ciliary motion 21

determination of 140

Carbohydrates 153-156

Cardiogram 92

Cardio-pneumatogram 139

Cardiograph 91

353

354

INDEX.

PAGE

Cardiograph 311

Cardinal points of simple di-
optric system 207

Cells, galvanic 308

Cell, work done by 29

Chemical stimulation 60

Chloroform, effect on ciliary

motion . . 21

Chronograph 317

system 319

Ciliary motion 16

Circulation, capillary 85

Circulatory system, artificial. . . 102

Circuit, short and long 40

primary and secondary 70

Citric acid in gastric digestion . 173

Conjugate focal distances 203

Color sense 238

perimeter . 230

Commutator, Pohl's (Fig. 5). . . 28
Compensator, Ludwig (Fig. 8).. 46
Constant current, stimulation

with 68

Convergence 216, 221

amplitude of 241

to measure 241

negative 245

Counting white corpuscles 265

red corpuscles 262

red and white corpuscles. . 268

Curare 287

Curarize a frog 309

Current, polarizing 76

how measured 31

change of course 29

change of direction 28

Curvature, radius of 201

Daniell cell 27

Data, anthropometric 127

evaluation of. . . 127

Data, grouping of 127

preservation of 125

Descending current 68

Detector (Fig. 6) 35

Dextrin, properties of 154 155

Diameters of chest 124

Diaphragm, action of 132

tactile observation of 133

Diffusibility of fat-derivatives. . Ib4

of proteids 166

Digestion and absorption, intro-
duction 150

salivary 157

gastric 171

Digitalis 300

influence on blood prts. ... 801

Dilute hydrochloric acid 320

Dioptric system (Fig 29, A)... 207

Direct vs. indirect stimulation. . 26
Discharge of liquids through

tubes 95

relation of to resistance. . . 95

Dissection of eye 192

Distance, pupillary 214

Dyne 24

Elastic tubes, flow of water in. 98

Elasticity of rabbit's lung 138

Electrical units 31

Electricity as a stimulus 65

Electrodes (Fig. 9) 52

Electrolysis, a measure of E.

M. F 30

Electromotive force, how meas-
ured 31

Electrodes, positive and nega-
tive 28

Electrotonus 75

laws of 79

Emmetropia 237

Emulsion . . 183

INDEX.

355

Endosmotic equivalent 191

Endosmotic pressure 190

Energy, electrical 30

Erg 24

Ergs of muscle work 74

Ether, effect on ciliary motion. 22

Evaluation of data 127

Eye, adaptation of for distance. 216
adaptation offer direction. 219
application of laws of re-
fraction to 210

dissection of 192

the reduced 211-212

to locate cardinal points in. 212

skiascopic 247

Extra polar region 76

Extract of pancreatic ferments. 185

Far point 218

Falling bodies, law of 94

Fats, emulsification of 183

Fats, saponification of 182

Fat-splitting ferment 187

Fehling'*s solution 153

Ferment 18G

amylolytic 187

fat-splitting 187

milk-curdling 187

proteolytic 187

Fixation binocular 220-242

monocular 219

Fixing fluid for tracings 311

Fixing the spread, haematology. 278
Flow of liquids through tubes. 93, 98

Focal distances, conjugate 203

apparatus for determining. 201

Focal distance of lenses 201

Form sense, to test 234

Fovea centralis, shadows of . . . 225
Frog-boards 307

Frog's heart-beat, graphic rec-
ord of 89

Frog's heart, the action of 87-89

Frog's thigh, anatomy of 57

Galvanic cells 308

Galvanismus 75

Gastric digestion, influence of

NaCl on... 177

influence of mechanical di-
vision on 178

influence of temperature on 179

steps of ISO

active factors of 172

acid factor of 173

Gastric juice, preparation of.. 171

Standard 175

Gastrocnemius preparation. ... 57

Girth of chest 124

Glass, to measure index of re-
fraction 200

Gmelin's test for bile pigments. 186

Hand electrodes 52

Haematology, microscopic tech-
nique 276

Haematocrit 271

Haematology 257

Haemogloblin, estimation of ... 273

Haemometer, Fleischl's ; 213

Heart-sounds 91

Height 1'25

Holder, for rabbit (Fig. 19) 110

Hydrochloric acid in gastric di-
gestion 173-174

influence of on putrefaction 177
Hydrochloric acid dil , to pre-
pare 320

Hydrogen, respiration in 145

Hyperopia 237

Illuminating gas, respiration in, 148

356

INDEX.

PAGE

Images, Purkinje-Sansom's. . . . 223

Impulse wave 99

Inelastic tubes, flow of water in, 98

Index of refraction of water. . . 199

of glass 200

instrument for determ.... 199

Induction shock, make 70

break 70

Intermittent pressure, influence

of 98

Intestinal digestion 185

Intra-abdominal pressure 114

Intra-polar region i6

Intra-thoracic pressure 114

to measure 116

Kaolin for electrodes 51

Katelectrotonus 76

Kathode 28

Kathode pole, influence of. ... 51

Key, Du Bois-Reymond (Fig.4) 29

simple contact, (Fig.-7-K ). 43

the mercury, (Fig. 3 ) 29

Kymograph 62

to smoke Drum 310

Lactic acid in gastric digestion. 173

Lactose, properties of 155, 156

Law of contraction, Pfluger's. . 80

of electrotonus 79

of falling bodies 94

of kathodic and anodic in-
fluence 55

of Torricelli 94

Lenses, focal distance of 201

Leucocytes, varieties of 280

Lever, for transmitting dia-
phragm movements 133

Lenses, numeration of 232

Light, perimeter 229

Light, sense 237

Liquids, flow of through tubes

93-98

Lung capacity 124

Macula lutea 225

Maltose, properties of 1 05, -156

Make induction shock 70

Manometer, mercurial 103

Marriotte's experiment 223

Maxwell's experiment 225

Mechanical stimulation 59

Median value 128-129

Mercurial manometer 103

Meter-angle of convergence. . . 244
Millon's reagent, preparation of 1(52
Milk, chemistry of 167-170

gastric digestion of 180

Milk-curdling ferment 187

Monocular fixation 219

Movements, respiratory 113

Multiple-arc, arrangement of

cells 3.)

Muscle-nerve preparation 56

Muscle-telegraph, Du Bois-Rey-
mond 48

Myograph, double (Fig. 10) 53

simple (Fig. 13) 59

Myopia 236

range of accommodation in 239

Myosin, preparation of 161

Narcotics, influence on ciliary

motion 16

Near point 218

Needle, saddler's for haematol-

ogy 259

Nitric acid test 163

Nitrogen, generation of . . . .147--148

respiration of 147

Nonpolarizable electrodes 52

Normal saline solution 307

INDEX.

357

PAGE

Numeration of Lenses 232

Ohms, unit of resistance 31

Olein 183

Operating case 308

Ophthalmoscope 247

Ophthalmoscopy 247

Optics, physiological 198

Osmosis 189-191

Palmitin 183

Pancreatic ferments, glycerin

extract of 185

Pancreatic juice, action of 186

artificial 185

Pepsin, glycerine extract of. . . . 171

possible dilution of 175

Peptone, to separate from other

proteids 165

diffusibility of 167

Perimeter, instrument 2'2Q

circles 228

chart 230

Perimetry 226

Pfliiger's law of contraction. ... 70

Pharmacology 285

Phosphoric acid in gastric di-
gestion 173

Photometer 237

Phrenic nerve, dissection of.... 134

Phrenogram 132-134

Phenograph 132

Physiological operating case. . . 308

Piezometer 96

Pilocarpin 293

Pith, to pith a frog 16

Plane, inclined, for computing

ciliary work 24

Plates, positive and negative. .. 28
Plasma and corpuscles, relative

volume 270

Pneomanometer. . . 125

PAGE

Pneomanometer 317

Pneumantogram 136

Pohl's commutator 28

Polarizing current 76

Poles, positive and negative-. . . 28

Preparation, gastrocnemius. ... 56

sartorius 61

Pressure, arterial 104

endosmotic 1 90

formula? 104-105

intermittent 98

intra-abdominal 1 14-116

intra-pulmonary 137

laws of blood pressure 102

of liquid in tubes 96

respiratory - 137

venous 104

Proteids, diffusibility of 166

coagulation of 162

properties of 161

tests for 163-164

Proteoses, diffusibility of 167

Proteolytic, ferment 167

Pulmonary vagus 137

Pulse 106

impulse wave 99

Punctum proximum 218

remotum 218

Pupillary distance 244

Purkinje-SansonTs images 22'.$

Rabbit board (Fig. 19) 110

Rabbit's lungs, elasticity of 138

Radial artery, location of 100

Radius of curvature 201

Range of accommodation 238

Reaction changes in fatigued

muscles 74

Red blood corpuscles, varieties

of 280

Red corpuscles, counting 262

358

INDEX.

PAGE

Red and white cells, differential

counting of 280

Reduced eye 211 212

Reducing sugars, tests for 155

Rennin 181

Reservoir 93

Resistance, central and distal. . 97

how measured 31

Resistance, relations of to dis-
charge 95

Respiration 113

in closed space U4

in CO2 gas 145

N-gas 148

H gas 148

under abnormal conditions 14t

in abnormal media 147

Respiratory movements 113

in man 118

pressure 133

quotient 143

Rheocord, DuBois-Reymond's. 40

simple (Fig. 7) 43

Rheonom, Fleischl's 48

Rheostat 40

Saccharose, properties of. . 155-15(5

Saline solution (0.6#) 307

Salivary digestion 157-101

Saponification 182

Sartorius preparation 01

Scheiner's experiment 222

Series, arrangement of cells in. 35
Siphon bottle for solut ons

(Fig. 53)

apparatus for forcing gas. .

Skiascopic eye

Skiascopy

Sodic chloride (0.6#)

Snellen's test type

Sphygmograms

307
20
247
252
307
233
106

Sphygmographs 100

Spirometer 124

Spreading blood, haematoh gy. . 278

Staining blood 278

Standard gastric juice 175

Starch, digestion of 158

properties of 153

Stearin ; 183

Stethograph 1 18 1 1 9. 313

Stethogoniometer 118, 12?, 316

Stethoscope 91

Stimulants, influence of on cil-
iary motion 16

Stimulation, chemical 60

direct 26

indirect . . 20

of vagus 112

mechanical 59

thermal 60

variations of 02 63

Strychnin 295

Syntonin, preparation of 161

Tandem, arrangement of cells. 36

Tambours, receiving 312

recording 312

Tape, meter 124

Test types, Snellen's 233

Thermal stimulation 00

Thoracometer 118, 120, 314

Thorax, contour of 123

Toisson's solution 208

Torricelli, law of 94

Tracings, fixing fluid for 311

Tromer's test 157

Tubes elastic, flow of liquids

through 97

flow of liquid through 93

inelastic, flow of water in. . 98

Units electrical 31

Vagus nerve, action of 109

INDEX.

359

Vagus nerve, pulmonary 137

stimulation of 112

Value, median 128-129

Velocity of flow of liquids 74

Venous pressure 104

Veratrin 298

Vision 192

acuteness of . 232

Visual angle 233

Volts, unit of electro-motive force 31

PAGE

Water element 65

to measure index of refrac-
tion of water 199

Wave, pulse or impulse 99

Weight 125

White corpuscles, counting. . 265

Work done by cilia 24

done by a muscle 73

Xanthroproteic test 164

Yellow spot 225

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