m

W..V.

A COMPARATIVE STUDY OF

TEMPERATURE FLUCTUATIONS IN DIFFERENT

PARTS OF THE HUMAN BODY

BY

FRANCIS G. BENEDICT AND EDGAR P. SLACK

{From the Nutrition Laboratory of the Carnegie Institution of Washington)

WASHINGTON, D. C.
Published by the Carnegie Institution of Washington

I9U

vf>

CARNEGIE INSTITUTION OF WASHINGTON
Publication No. 155

3^7

PRESS OF GIBSON BROTHERS
WASHINGTON, D. C.

CONTENTS.

Part I.

Page.

Introduction 1

Heat production 1

Direct and indirect calorimetry 3

Purpose of the research 3

Localities for temperature measurement 4

Natural cavities 4

Artificial cavities 6

Surface temperature 6

Base line in measuring body-temperature 6

Errors in rectal-temperature measurement 6

Constancy of rectal-temperature 7

Factors affecting body-temperature 7

Part II.

Methods and apparatus 9

Comparison of methods 9

Theory of method of measurement used 11

Adaptation of method for use 12

Apparatus used in the research 12

Constants of the apparatus 12

Construction of the apparatus 14

Measuring instruments 14

Thermal-junction system 17

Constant temperature oven 20

Calibration of mercury thermometers 22

Method of operating apparatus 23

Calibration of thermal junctions 24

Computations for the calibration 25

A sample body- temperature experiment 27

Computations for the experiment 27

Precision of measurement 28

Later modification of the apparatus 30

Part III.

Discussion of results 35

Thermal gradient of the body 35

Method of studying the thermal gradient 35

Experimental results 36

General conclusions with regard to the thermal gradient 39

The selection of localities for simultaneous measurement of fluctuations in body-
temperature 40

Natural cavities 40

Temperature measurements in the mouth 40

Artificial cavities 43

Simultaneous observations of body-temperature in different localities 44

Experimental results 45

Conclusions 72

m

ILLUSTRATIONS.

Page.

Fig. 1 . Elementary wiring diagram of apparatus 11

2. Complete wiring diagram of apparatus 15

3. Types of thermal-junction thermometers used IS

4. Details of constant-temperature bath 19

5. Constant-temperature oven 21

6. Elementary wiring diagram of modified apparatus 31

7. Complete wiring diagram of modified apparatus 32

8. Detachable thermometer for use inside the calorimeter, with connections. 33
9-13. Observations on thermal gradient 3G-39

14. Observations showing rise of temperature in the mouth 41

15-38'. Temperature curves for experiments 46-71

V

A COMPARATIVE STUDY OF TEMPERATURE FLUCTUATIONS IN
DIFFERENT PARTS OF THE HUMAN BODY.

Part I. — Introduction.

The normal body-temperature is a resultant of two factors, thermogenesis,
or the development of heat inside the body; and thermolysis, the loss of heat
from the body. Usually these two factors are so delicately adjusted as to be
nearly equal in value and hence the resulting temperature of the body does
not alter materially. When there are marked disturbances in either factor,
we have changes in body-temperature. Innumerable experiments1 have been
made to investigate the factors influencing both thermogenesis and thermolysis,
and it has been proved that the most important factor affecting thermogenesis
is muscular work, either voluntary or involuntary, while the most important
factor affecting thermolysis is the temperature environment; this latter is
particularly true of small animals.

A knowledge of the fluctuations in body-temperature is of inestimable value
to the physician as an index of the body condition; in health the normal limits
are rarely exceeded, and consequently increased temperature indicates that
radical measures must be taken. To the physiologist, also, a knowledge of the
course of the normal body-temperature is important, and when experiments
on calorimetry are attempted this factor has especial significance.

HEAT PRODUCTION.

By means of modern apparatus, an accurate measurement may now be made
of the total heat given off from the body of a man during an experimental
period by the three paths of conduction, radiation, and the latent heat of
water vaporized. This of itself is an important contribution to physiology,
but of still greater importance is the measurement of the total heat production.
The heat production may or may not be the same as the heat elimination,
since any discrepancy between thermogenesis and thermolysis causes a change
in body-temperature resulting in the loss of a certain amount of heat previously
stored, or the storage of heat to be subsequently eliminated. This may be
shown by a simple calculation:

From the results of a large number of experiments, a standard value for
heat production has been computed for a man weighing G6.6 kilograms, while
at rest and asleep.2 Owing to its large content of water, the body has the

■A historical development, of the study of body-temperature, including methods, is given
in the excellent article by Pembrey in Schaefer's Textbook of Physiology, vol. 1, 1898, p.
785. This article also includes an extensive statement of literature up to the date of
publication.

-Benedict and Carpenter, Pub. No. 126, Carnegie Institution of Washington, 1910, p. 253.

1

2 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

somewhat high specific heat of approximately 0.83 j1 the body of a man weighing
66.6 kilograms would consequently have a hydrothermal equivalent of about
55 kilograms of water, so that a change in its temperature of 0.1° C. would pro-
duce either a storage or a loss of 5.5 calories of heat. According to the standard
value which has been computed, the heat production of a man of this weight
and under these conditions would be 71 calories; consequently the amount of
heat absorbed or given up by the body as a result of the change in temperature
of 0.1° C, i. e., 5.5 calories per hour, would be approximately 7.7 per cent of
the total. This discrepancy is too great to permit the measurement of the
heat elimination to be taken as an index of the heat production.

Practical experience has shown that a change in temperature amounting to
0.1° C. is very likely to occur, even with enforced body quiet and rest; as a
matter of fact, a normal variation in temperature amounting to 1.5° C. is
easily possible in a period of 24 hours. If, as is wholly unlikely, such a large
variation as 1.5° C. should take place in a shorter experimental period as, for
instance, 1 hour, there would be, under the conditions previously cited, a
liberation or storage of heat of 82.5 calories. If this heat were stored instead
of being eliminated, it is quite conceivable that during the 1-hour period
the body would produce heat at such a rate as to raise its temperature 1.5° C,
with the elimination of absolutely no heat. While such conditions are physio-
logically impossible in so short a period, yet when physiologists are attempt-
ing to measure the heat production for periods of 1 hour or less a knowledge
of even slight variations in body-temperature is of great importance.

The determination of the fluctuations in body-temperature in 24-hour
respiration calorimeter experiments is not of particular importance, since one
would expect to find approximately the same body-temperature at approxi-
mately the same hour of the day; thus, all of the earlier experiments published
by Atwater and Benedict2 were planned on the assumption that at 7 o'clock
in the morning, (the end of the 24-hour period) the body composition of a
subject existing on a uniform diet was constant from day to day, and the
body-temperature returned to essentially the same level at this time. When
the attempt is made, however, to shorten the experimental periods to 8 hours,
6 hours, 2 hours, or even less, an exact knowledge of the body-temperature
at the beginning and end of each period becomes of more and more importance.
By means of respiration calorimeters,3 it is now perfectly feasible to measure
the chemical factors of metabolism, namely, the carbon dioxide excretion,
oxygen consumption, and water vaporization, in periods of 1 hour; indeed, in
the past few months, experimental periods of three-quarters of an hour have
been successfully carried out and made a part of the regular routine of this
laboratory. The heat eliminated can be likewise measured, and it remains
only to make an accurate measurement of the body-temperature to secure the
data for computing with considerable exactness the heat production during
these periods.

'Pembrey, loc. cit., p. 839.

*Atwater and Benedict, U. S. Dept. Agri., Office Exper. Sta., Bull. 136, 1903.

'Benedict, Riche and Emmes, Am. Journ. Physiol., 1910, 26, p. 1.

INTRODUCTION.

DIRECT AND INDIRECT CALORIMETRY.

The data regarding the heat production in short periods are especially
valuable in demonstrating the accuracy of so-called indirect calorimetry as
compared with direct calorimetry — a demonstration which is of great theo-
retical as well as practical importance. Such a comparison has been repeatedly
made for periods of 24 hours1 by Atwater and associates, and while the methods
of these investigators differ somewhat from those used by Zuntz, it has been
shown conclusively that indirect calorimetry for periods of this length is
extremely accurate. This demonstration, however, is of little practical value.
In the first place, in relatively few instances is the total carbon dioxide excre-
tion for 24 hours determined from which the heat production can be calculated.
Secondly, it is extremely rare that the total oxygen consumption for this period
is determined. Practically all of the computations made by the Zuntz school
have been based upon experiments of 15 to 40 minutes' duration. It becomes,
therefore, of fundamental importance to demonstrate the relationship between
the gaseous exchange and the heat production not only in periods of 24 hours
but in short periods, also.

The calculation of the total metabolism from the data regarding the nitro-
gen excretion, the carbon-dioxide excretion, and the oxygen consumption
assumes that the nitrogen and the carbon dioxide excreted and the oxygen
consumed during a given period represent direct molecular transformations
which resulted in an energy transformation during that period; that is, that
there was no material delay in the oxidative processes; that there was no
accumulation of either oxygen or carbon dioxide in the system; and that the
nitrogen corresponded to the protein broken down during the period under
investigation. Considerable criticism has been made of this method of calcu-
lation, but in all probability, if proper precautions are taken to secure constant
conditions of diet for a sufficiently long period beforehand, there will be a gen-
eral uniformity in metabolism; and while the metabolism actually measured
in any hour period, as for instance, between 8 and 9 a. m., may not represent
the exact transformation during the period, nevertheless it does represent a
certain definite average transformation which is approximately accurate.
Until, however, it has been clearly demonstrated that indirect and direct
calorimetry agree even for short periods, we can place no absolute dependence
upon observations and calculations based upon indirect calorimetry.

PURPOSE OF THE RESEARCH.

To sum up, then, it is possible for us to measure with great accuracy the
carbon-dioxide excretion, oxygen consumption, water vaporization, and nitro-
gen excretion during any given experimental period. We can likewise measure
with considerable accuracy the heat eliminated by radiation, by conduction
and in the latent heat of water vaporized. On the other hand, we find great

•Atwater and Benedict, loc. cit.; also Benedict and Milner, U. S. Dept. Agri., Office of
Exper. Sta., Bull. 175, 1907.

4 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

difficulty in computing exactly the heat production, since this is dependent
upon an accurate measure of the body-temperature. In any method of meas-
urement thus far devised, the important assumption must be made that the
human body as a whole undergoes an average change in temperature corre-
sponding to the fluctuations found by measuring the temperature of any one
portion of the body. This last assumption has been based on such uncertain
evidence up to the present, that it has seemed desirable to investigate more
carefully the fluctuations in temperature of the different parts of the body.

In taking up this problem, we were at once confronted with two rather
important questions: First, where is the best place to take the temperature of
the body; and second, are the fluctuations in temperature uniform throughout
the body? Certain reasoning might here be brought forward to prove that
the blood, being a great distributor of heat, equalizes the temperature through-
out the whole body, so that we should expect the temperature changes in the
different parts to follow a parallel course. If all parts of the body were of
essentially the same temperature, this might be easily assumed without ques-
tion; as a matter of fact, the temperature is not uniform, there being, as one
would naturally expect, a sharp thermal gradient. The accurate measurement
of the surface temperature presents many difficulties, but as a result of num-
erous observations made by different methods, 32° C. has been commonly
accepted as a standard, and is probably not far from the true value. The tem-
perature inside the body, on the other hand, is known to be not far from 37° C. ;
we have here, therefore, a gradient of 5° C. This gradient should be very
carefully studied before assuming that the temperature in different parts of
the body remains constant throughout the whole series of experiments. If the
source of heat is constant, as evidenced by the interior temperature of the
body, and the temperature of the environment does not change, there is every
reason for believing it probable that the gradient will be constant.

Accordingly, in this particular research we have made a simultaneous study
of body-temperature, with reference to determining: (1) the best place for an
accurate and constant measurement of body-temperature; (2) the tempera-
ture gradient of the body; and especially (3) whether or not the temperature
fluctuations occurring in the different parts of the body are uniform.

LOCALITIES FOR TEMPERATURE MEASUREMENT.
NATURAL CAVITIES.

A physical examination of the body shows that there are a number of natural
cavities which provide favorable opportunity for measuring the body-tem-
perature, since thejr are surrounded by living tissue and not subjected to the
immediate effects of the external environmental temperatures. Of these
cavities, by common consent of practically all physiologists, the rectum is
considered to be the most favorable and to indicate the truest temperature of
the interior of the body. Its use, however, is practicable only in experiments
with patients who are bed-ridden and in physiological tests. With female

INTRODUCTION. 5

subjects under similar conditions, the vagina is also an admirable place for
making temperature observations.

Rectum. — In taking the temperature in the rectum, it is of prime importance
first to note that the thermometer should not be imbedded in fecal matter, as
otherwise there may be a sluggishness in the records. This is particularly
necessary with glass clinical thermometers, which are sufficiently rigid to
become easily imbedded in a mass of fecal matter. Again, the thermometer
must be inserted deep enough in the rectum to make sure that the record is
not affected by the temperature of the outside air. This latter point will
receive special consideration later.

Mouth. — In the private practice of a physician, the rectum and the vagina
are practically precluded in the majority of instances and recourse is had to
taking the temperature in the mouth. While it is true that the cavity in the
mouth underneath the tongue is surrounded by living tissue and protected,
at least in part, from the external environmental temperature, nevertheless
the cold air from the nasal passages, the freo.uent breathing through the mouth,
and the rapid vaporization of water by the relatively dry air entering the mouth
usually produce a supercooling of this cavity. This supercooling may be very
noticeable, particularly after severe exercise.1

Stomach. — The stomach has been rarely used in measuring body-tempera-
ture, since it is somewhat difficult for subjects to swallow a stomach tube with
any degree of comfort. While there are relatively few instances in which a
fistula has been employed for such measurements, a most interesting series of
observations has been made on the temperature in the stomach during diges-
tion, beginning with the early experiments of William Beaumont2 on Alexis
St. Martin, and continuing with the more recent experiments of Rancken and
Tigerstedt.3 Under ordinary conditions, however, it is practically impossible
to measure the temperature in this way.

Bladder. — So far as we know, no records of the body-temperature have been
taken in the bladder by means of a thermometer inserted through a catheter;
nevertheless, mention should be made of the extremely ingenious method first
suggested by Stephen Hales4 of measuring the temperature of freshly voided
urine which represents very nearly the temperature of the interior of the body.
In such observations it is evident that the time during which the temperature
can be taken is relatively short, depending upon the volume of urine passed.
Furthermore, the thermometers used should be very sensitive and should first
be warmed by the hand or in the mouth to nearly the temperature of the body
before placing the bulb in the stream of urine.

■Williams and Arnold: Phila. Med. Journ., 3, p. 1233.

2Beaumont, Experiments and observations on the gastric juice and the physiology of
digestion, Plattsburgh, 1833.

3Rancken and Tigerstedt, Biochem. Zeitsch., 190S, 11, p. 3G.
'Hales, Statical Essays, London, 1731, 2d ed., 1, p. 59.

0 TEMPERATURE FLUCTUATIONS IN THE HUMAN RODY.

ARTIFICIAL CAVITIES.

Axilla. — In addition to the natural cavities of the body, there are certain
artificial cavities which can be formed by a movement of the limbs, or the
folds of the skin, the most important being the axilla. In the normal position
of the arm, the axilla provides a natural cavity which needs only to be care-
fully closed in order to approximate an interior cavity of the body. The
axilla is, however, for a good part of the time exposed to a temperature envi-
ronment not far from 32° C.,i. e., the surface temperature of the body, instead
of 37° C, that of the interior of the body. The presence of moisture, sweat
glands, and hair all combine to make this cavity somewhat difficult to use.

Groin. — Another locality which has been found of great value is the groin.
Particularly is this useful in taking the temperature of small infants when
clinical thermometers can not be used in either the mouth or the rectum for
fear of breakage. Unless subjects are emaciated, it may also be used very
satisfactorily with adults after the cavity has become warmed to the tempera-
ture of the body.

Other cavities. — Other artificially prepared cavities may be secured by
crossing the legs, the temperature being taken inside of the thighs; and by
holding the thermometer between the two hands, and obtaining the tem-
perature of the palms. These cavities, however, are not generally used for
measuring the body-temperature in either medical practice or physiological
experimenting.

SURFACE TEMPERATURE.

The temperature of the exposed surface of the body can be taken at any
point, but, as has already been stated, such observations present many diffi-
culties. Any form of thermometer that may be used is not only subject to the
temperature of the body, but also to that of the cooler outside environment;
and while this discrepancy may be somewhat lessened by artificial warming,
such measures are at best unsatisfactory and inaccurate. Again, if the ther-
mometer is firmly fastened to the body, there is liable to be a local conges-
tion, especially if the area of the thermometer is large, and the functions
of the sweat glands, both underneath the thermometer and in its immediate
vicinity, may be somewhat disturbed.

BASE-LINE IN MEASURING BODY-TEMPERATURE.

An examination of these different possibilities or localities for taking the
temperature of the body shows immediately that those least affected by
environmental changes are the natural cavities in the body, i. e., the rectum,
the vagina, and the mouth, the records obtained in the rectum being commonly
considered the best suited as a base-line for all observations.

ERRORS IN RECTAL-TEMPERATURE MEASUREMENT.

In thus using the rectal-temperature as the base-line, it is necessary to take
into consideration the possible errors affecting the measurements made in the

INTRODUCTION. 7

rectum. First, as has already been pointed out, the thermometer should not
be inserted in the fecal mass. If there is any danger of this, the fecal matter
should be removed by a water enema; also, sufficient time should elapse
between the taking of the enema and the beginning of the temperature obser-
vations to make sure that the change in the local temperature produced by the
water is not affecting the temperature of the rectum. Second, the thermometer
must be inserted sufficiently deep to give the maximum temperature, the depth
required being readily found by testing, and noting the point at which the
maximum temperature occurs. If the thermometer is constructed of non-
irritating material, there is very little liability of any local congestion. The
experience of observers with glass mercurial thermometers has led to some
difficulty in securing long-needed observations of body-temperature, owing
to the rigid construction of the thermometers, but with the flexible thermome-
ter employed by Benedict and Snell1 continuous observations can be readily
made in periods of several days, the thermometer being removed only for
defecation. It seems well established, therefore, that with a proper construc-
tion of the thermometer the fear of local congestion may be entirely eliminated.

CONSTANCY OF RECTAL-TEMPERATURE.

If the rectal-temperature is to be used as the base-line, it is natural to assume
that there should also be a more or less constant temperature which should be
taken as the base-line, and we can properly question whether or not the rectal-
temperature is sufficiently constant for this purpose. Obviously the tempera-
tures which are markedly above the average of a large number of observations
may be taken as indicating fever and should not be used as a base-line. On the
other hand, there may be a fluctuation in the normal temperature amounting
to 1.5° C, and any fluctuations within this limit may be reasonably taken as
normal for the individual under experimentation. Before assuming that the
observations of the rectal-temperature represent a normal value for the indi-
vidual, however, we should examine carefully to find what factors affect the
body-temperature.

FACTORS AFFECTING BODY-TEMPERATURE.

Exposure to severe cold lowers the temperature, provided there is no shiver-
ing incidental to an attempt on the part of the body to compensate for the
excessive heat lost. The ingestion of hot or cold food and drink, likewise
muscular work, produces an almost immediate effect. In connection with
muscular work, it is important to note that there may be not only internal,
but also external muscular work; consequently, for the strictest comparison,
the temperature of the subject should be measured under constant condi-
tions of muscular activity, ingestion of food, etc.

Furthermore, it has long been known among physiologists that there is a
rhythm or periodicity in the temperature of the body. By experiment, it has

Benedict and Snell, Archiv f. d. ges. Physiol., 1901, 88, p. 492.

8 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

been found that this rhythm is somewhat as follows : The minimum tempera-
ture occurs during the early morning hours, usually between 2 and 5 o'clock;
there is then a marked early morning rise which becomes less pronounced as
the day progresses, but reaches its maximum in the afternoon about 5 o'clock;
this is followed by a slight fall, which becomes very noticeable after retiring
and gradually continues until the minimum point is again reached in the
early morning.

A number of attempts have been made to explain this rhythm, which as yet
have been only partially successful, although the rhythm appears to be more
or less coincident with the muscular activity incidental to the day's work.
This explanation is not scientifically complete, however, for it does not explain
why a night watchman,1 who for seven years had been working during the
night and sleeping in the daytime, should still have the highest body-tempera-
ture at 4 or 5 o'clock in the afternoon when he was sound asleep, and the
lowest value at 4 or 5 o'clock in the morning when he was awake and on his
rounds. Daylight and cosmic influences have also been thought to have an
effect upon this rhythm. It is not the object of this report, however, to enter
into a discussion of the cause of the normal periodicity or rhythm, but in
any study of body-temperature this factor should be taken into consideration
when endeavoring to establish a base-line. For the particular reason for which
this investigation was undertaken, namely, to study simultaneously the tem-
perature fluctuations in different parts of the body in order to find whether or
not they paralleled each other, the absolute temperature values at any given
point are not of such great importance as are the variations. Consequently
we may assume that previous experiments have demonstrated clearly the
existence of a rhythm and have likewise demonstrated the difficulty of giving
a satisfactory explanation which covers all observations thus far made.

Johansson's belief2 that the body-temperature is influenced in large part by
the metabolism is strongly substantiated by his observations, and yet it is
difficult to conceive that the night watchman previously referred to had a
higher metabolism during the periods when he was sound asleep than when he
was sitting up in a chair engaged in conversation. From the well-known
relationship between the pulse-rate and the metabolism, it is clear that all
future experiments on body-temperature should be accompanied by a simul-
taneous observation of the pulse-rate and, so far as possible, of the metabolism
and its changes. In the majority of experiments, observations of the metab-
olism will be impossible, but records of the pulse-rate may be easily obtained
by practically all observers. If to these observations can be added others with
regard to the blood pressure and pulse pressure, the results will be still more
valuable, especially in throwing light upon the contention of Johansson that
the body-temperature is a function of the total metabolism.

'Benedict, Am. Journ. Physiol., 1904, 11, p. 145.

2 Johansson, Skand. Archiv f. Physiol., 1896, 7, p. 123.

METHODS AND APPARATUS. 9

Part II. — Methods and Apparatus.

An analysis of the measurements to be made as outlined in the preceding
section shows that the method of measurement must comply with the following
requirements :

Several temperatures must be observed at practically the same time, and
this process repeated at intervals of a few minutes for protracted periods.

The precision of the measurement must approximate 0.01° C.

The thermometers must be capable of being read without being disturbed;
they must also be small and flexible, so as not to cause undue discomfort even
if in position for a considerable length of time.

Only two methods were considered as being able to meet these conditions,
namely, those employing (1) electrical resistance thermometers,1 and (2)
electrical thermal-junction thermometers.2

COMPARISON OF METHODS.

The many advantages of the resistance method have led to its extended
application. In the first place, it has inherently a greater sensitiveness than
can be obtained by the thermal-junction method. The reason for this might
be suggested by the fact that in the resistance method the amount of energy
expended in the thermometer is left entirely to the discretion of the designer,
while in the thermal-junction method the source of energy is in the thermome-
ter itself and therefore is limited by the physical properties of the junction.
This implies, also, that the electromotive forces involved in the resistance
method will, in general, be far greater than those used in measurement with
the thermal junction, so that with the resistance method comparatively little
trouble will be experienced from extraneous electromotive forces, which are so
common a source of annoyance in thermo-electric measurements. Another
advantage of the resistance method is that the measurement is completed by
performing a single operation, usually that of balancing a bridge; there is no
second temperature to be read, no potentiometer current to be adjusted, and
no routine observations necessary to correct for the effect of extraneous
electromotive forces. Also, the apparatus for measuring the temperature of
the resistance thermometer is simpler than that required for the thermal
junction, as in the former case no constant temperature need be maintained,
also no standard cell is necessary.

In spite of these manifest advantages, there are certain qualities inherent
in the resistance method which make it less fitted than the thermal-junction
method for meeting the requirements previously outlined. For example, the
measuring current flowing through the resistance thermometer produces an
appreciable heating of the wire, the resistance of which is being measured.
In measurements with the thermal junction, however, the current taken from

'Benedict and Snell, Archiv f. d. ges. Physiol., 1901, 88, p. 492; and 1902, 90, p. 33.
-Gamgee, Phil. Trans. Royal Soc. of London, Ser. B., 1908, 200, p. 219.

10 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

he j unction for the purpose of deflecting a galvanometer would be very slight,
so that the heating — which depends on the square of the current — would be
very small indeed. Furthermore, a method may be used which does not
involve drawing current from the junction, and thus the error may be entirely
avoided.

Again, the resistance thermometer, as usually constructed for body-tem-
perature measurement, consists of a coil of fine wire, inclosed in a metal shell.
This construction is necessarily bulky, owing to the fact that a considerable
quantity of wire must be used. Moreover, the mass of the thermometer is
large, giving more or less lag, and its construction is relatively very difficult.
The thermal-junction thermometer, on the other hand, in its simplest but
thoroughly practical form, consists merely of a twisted and soldered joint
between two fine wires, one of which is insulated, both wires being protected
from moisture and mechanical injury by an outside case of thin-walled rubber
tubing. It will thus be seen that the thermometer is small and flexible, which
not only permits its ready introduction into the deep natural cavities of the
body, but also allows it to be covered easily by flesh when used in the shallow
artificial cavities; furthermore, its small mass precludes any appreciable lag.

A third disadvantage of the resistance method is that, in the type of ther-
mometer commonly used for body-temperature measurement, the resistance
itself is not in very good thermal contact with the body whose temperature is
being taken, whereas the thermal connection between the thermal-junction
thermometer and the body may be made absolutely ideal. Since no theo-
retical demands will be violated if one of the metals of the junction actually
touches the body being measured, the junction may be made in the form of a
wire of one of the metals soldered to the back of a thin plate or cap of the
other and the face of this latter applied directly to the body; in this way the
active material of the thermometer may touch the body without even the
thinnest layer of isolating material.

A careful comparison of the advantages and disadvantages of these two
methods, considered only in the light of the requirements of these special
experiments and not at all with regard to temperature measurements in general,
led to the adoption of the thermal-junction method, and this in spite of our
previous extended use of the resistance thermometer for body-temperature
measurements. The sensitiveness was considered ample, and the disadvan-
tages of the occasional observations necessary in reading a second temperature,
balancing current, and correcting for stray voltage were regarded as being
more than offset by the freedom from heating and the ability to use ther-
mometers which were at once small, simple, flexible, and strong. The thermal-
junction method has the still further advantage that the thermometers are
practically interchangeable without adjustment.

METHODS AND APPARATUS.

11

THEORY OF METHOD OF MEASUREMENT USED.

The thermal-junction method is based upon the well-known principle that
if a junction of two dissimilar metals be heated, a difference of potential
between the two will result; and if the circuit be closed through a galvanom-
eter, a current will be produced and the galvanometer deflected. In order
that small temperature fluctuations may be measured with precision, use is
made of a second junction in series with and opposed to the first, this second
junction being kept at a constant known temperature somewhere in the region
of the temperature to be measured. By this means the net electromotive force
is made very small, so that slight changes due to fluctuations of the unknown
temperature form a large percentage of the whole. The use of deflections in
this way, although convenient and simple, has one disadvantage, in that the
resistance of the galvanometer and conducting wires must be taken into
account, since a change in the circuit resistance would cause an inversely pro-
portional change in the deflection. With the appa-
ratus used in these body-temperature experiments,
a fluctuation of more than 1.2° C. in the galvan-
ometer temperature would not have been allowable.
Moreover, the effective voltage at the galvanometer
terminals, being the voltage of the thermal-junction
system minus the fall in potential along the wires,
would have been reduced to about 75 per cent of
its total value.

These conditions, although not prohibitive, were
nevertheless regarded as undesirable, so that a
"null" method, by means of which they were en-
tirely -avoided, was finally decided upon. This
"null" or "zero" method is a modification of the
ordinary potentiometer method for the measure-
ment of electromotive forces, and consists in balanc-
ing the electromotive force of the thermal-junction
system against the fall in potential across a section

of a standardized slide wire in which a known current is maintained. An
elementary diagram of connections is shown in fig. 1. The battery B sends
a current through the circuit B-D-C-A-B, the value of the current being
measured by the ammeter A. CD is a uniform slide wire of known resistance,
to one end of which, as at C, is attached one end of the thermal-junction sys-
tem TT. The other end of the thermal-junction system is connected through
the galvanometer G to a movable contact which may be touched at various
points along the slide wire until a point P is found at which no galvanometer
deflection results. The voltage of the thermal-junction system can then be
calculated, if desired, this being the product of the current expressed in
amperes and the resistance CP expressed in ohms. The voltage of the system
is, however, usually of secondary importance; what is desired is the tempera-

Fig. 1. Elementary wiring dia-
gram of apparatus. Current
from the battery B flows
through the slide wire DC
and returns to the battery
through the ammeter A.
The thermal-junction system
TT, with the galvanometer
G, is connected at one end to
C, and at the other to a
movable contact which may
be touched at any point along
the slide wire.

12 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

ture difference between the two junctions. This might be assumed to be
approximately proportional to the voltage, but can be obtained directly by
keeping both junctions at known temperatures; in this way the apparatus
can be calibrated so that different settings of the contact correspond to
definite values of the temperature difference being measured. In order to
make the apparatus direct reading, an additional resistance in series with
the battery is almost universally used and the current is so adjusted as to
accommodate itself to the particular slide-wire available. By bringing the
current to such a value that the fall in potential across one division of C-D
is equal to the voltage of the thermal-junction system for a temperature
difference of 0.01° C, the apparatus becomes practically direct reading in
hundredths of a degree.

ADAPTATION OF METHOD FOR USE.

The actual arrangement, as shown in fig. 2 (p. 15), does not differ in principle
from this. The storage battery B, which has been partly discharged in order
to obtain a more nearly constant voltage, sends current continuously through
the circuit B-R-Vi-V2-V3-V4-S in parallel with P-M-B. The resistance R is
fixed, and is placed in the circuit for the purpose of bringing the current to such
a value that the apparatus is practically direct reading; Vi, V2, V3, and V4 are
variable resistances by means of which the current can be maintained constant
in spite of slight changes in the electromotive force of the storage cell, such as
might be caused by a gradual discharging of the cell, temperature changes, etc.
The shunt S is placed across the potentiometer P on account of the extremely
low voltages to be measured. The resistance M is so arranged that the stand-
ard cell N and galvanometer G can be closed across it, this arrangement forming
the equivalent of a very accurate ammeter, so precise that a high resistance
O is introduced into its circuit to reduce the sensitiveness. Since the galva-
nometer must be used in connection with both the standard cell and the
thermal-junction circuits, the switches Gi and G2 are provided for transferring
it from one to the other. By means of the test switch T, the apparatus may
be tested for stray electromotive forces. The control switch K is used for
convenience in bringing the galvanometer to rest. The switches 1, 2, 3, 4, etc.,
are also provided so that the electromotive force of any one of a number of
thermal-junction systems may be measured. To each of these switches are
connected two copper wires, one of which runs to the body and the other to a
constant-temperature bath, these latter terminals being connected by a con-
stantan wire, which furnishes the second metal for the thermal junctions.

APPARATUS USED IN THE RESEARCH.
CONSTANTS OF THE APPARATUS.

While considering the measurement from a purely theoretical standpoint,
and before proceeding to a description of the actual construction, it may be
well to bring together the constants of such parts of the apparatus as were
available for the work, and to include the computations by means of which

METHODS AND APPARATUS. 13

the remaining constants were derived and the suitability of the apparatus
for the work assured.

The potentiometer has a resistance of 15,000 ohms, which can be included
between the potential terminals in steps of 0.1 ohm. The galvanometer
resistance is about 50 ohms, and the sensitiveness such that a deflection of 0.5
millimeteris produced by a current of 15 X 10~10 amperes. The resistance of the
constantan wire as selected is about 14 ohms for each circuit; that of the
copper is negligible. The electromotive force of the copper-constantan couple
is taken as 40 X 10-6 volts per degree centigrade. The voltage of the storage
cell is 2.0 volts, that of the standard cell 1.0197 volts. Most of the tempera-
tures to be measured are assumed to lie within the limits of 36° to 38° C, and
are desired to an accuracy of about 0.01° C. The apparatus, however, should
not be restricted to these limits but should be capable of measuring lower
temperatures, although with a somewhat decreased precision.

The constant-temperature junction is kept at a temperature of about 40° C,
and as the other junction never rises to so high a temperature as this, it follows
that the net voltage of the thermal-junction system always acts in one direc-
tion. The temperature difference between the junctions is usually not less
than 2° C. nor greater than 4° C, so that under these circumstances the
voltage limits would be 80 X 10~6 volts and 160 X 10~6 volts, between which
the voltage should be determined to approximately 0.4 X 10-6 volts.

The necessity for a potentiometer shunt may be very easily shown. If the
apparatus is to be direct reading — a change of 0.4 X 10-6 volts involving a
change of 0.1 ohm in the potentiometer setting — then a current of (0.4 X 10~ )
-f- 0.1, or 4 X 10~6 ampere is required, and this, if a regular series circuit is used,
demands the use of a circuit resistance of 2-t- (4 X 10~6) or 500,000 ohms.
Since this is hardly practicable, it has been decided to shunt the potentiometer,
leaving the current in the potentiometer itself 4 X 10-6 ampere, but taking
from the storage battery about 0.01 ampere, and causing the remainder to flow
through the shunt. For the main current a value of 0.0102 ampere has been
decided upon, as this permits the use at M of a 100-ohm coil. The value of S
is then (4 X 10~6 X 15000) 4- (0.0102) = 5.88 ohms. The total resistance of the
circuit is 2.0^-0.0102 or 196 ohms, 100 ohms being taken by M and about 6
ohms by S in parallel with P, leaving still 90 ohms necessary to be taken up in
R, Vi, V2, V3, and V4.

To determine the proper value for each step of the variable resistances, it
must be noted that while voltages as high as 160 X 10~6 volts are to be meas-
ured, yet a deviation of 0.2 X 10-6 volts will in itself produce an error in the
results sufficient to affect the nearest hundredth of a degree. From this it is
seen that the current must not vary by 2 parts in 1600, so that each step in the
variable resistances must not make more than this fractional change in the
resistance, or (2 -M600) X 196 = 0.25 ohm. This represents the maximum
allowable change; consequently the steps in the resistance as actually made
are smaller than this. The smallest steps are in the resistance V3, which is
composed of nine 0.1 ohm coils. Similarly V4 comprises nine 1.0 ohm coils, so

14 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

that the combination gives a resistance of about 10 ohms, variable in tenths
of ohms. Vi and V2 are provided should even more adjustment be necessary,
and have a resistance of 5 ohms each. This gives 20 ohms for the sum of the
variable resistances, about half of which should be in circuit under normal
conditions, so as to allow adjustment in either direction. The value for R
is accordingly 90 — (20^2) =80 ohms.

To determine whether the galvanometer is sufficiently sensitive, it will be
simplest to consider the case of a measurement being made in which the circuit
is not quite balanced, but owing to the insensitiveness of the galvanometer it
appears to be so. The largest current that can pass through the galvanometer
and still be undetected is 15 X 10~10 amperes. This current in flowing through
a resistance of 64 ohms, composed of the galvanometer and thermal -junction
system, causes a fall in potential of 15 X 10-10 X 64 or about 10-7 volts.
Since 0.01° C. corresponds to 0.4 X 10-6 volts, or 4 X 10~7 volts, it is seen
that the error due to insensitiveness of the galvanometer corresponds to about
0.0025° C. and is therefore entirely negligible.

CONSTRUCTION OF THE APPARATUS.

Having determined the constants, or electrical dimensions, of the various
pieces of apparatus considered in fig. 2, the actual method of construction and
installation will be given in some detail. This seems advisable, since in some
cases the peculiar experimental conditions to be met required a special form
of construction; while in other cases some of the more elaborate pieces of
apparatus available, which were not ideally adapted to the work, have been
made to conform more closely to the desired qualifications.

MEASURING INSTRUMENTS.

Storage cell. — The storage cell B is one of a battery of six cells, having a
normal rate of three-quarters of an ampere and provided with separate
terminals for each individual cell. A suitable resistance, not shown in fig. 2,
is arranged so that it can be connected across the battery when desired. The
separate terminals permit each cell to be used singly, and the resistance is
used partially to discharge the battery when freshly charged, thus causing its
voltage to be more nearly constant.

Both the storage cell and the standard cell are provided with reversing
switches, which are mounted on a single base and arranged so as to be operated
together by means of one handle. This is done for the following reason: The
electromotive force of the thermal-junction system, standard cell, and storage
cell must all act so as to have a tendency to send current through the main
circuit in the same direction. For the purpose of keeping the voltage set up
by the junction unidirectional, the temperature of the oven is always kept
higher than that of the body. In order to provide for a possible decrease in the
oven temperature, with a consequent reversal of this voltage, the storage cell
and standard cell are furnished with the reversing switches just mentioned.

The resistances R, Vi, V2, V3, V4, S, M, and O, as well as the coils in the
potentiometer, are of manganin. Vi and V2 are each arranged to be short-

METHODS AND APPARATUS.

15

circuited by knife switches, while V3 and V4 are made up from two dial switches.
The wires joining the main circuit to the shunted potentiometer are connected
to the terminals of the shunt rather than to the terminals of the potentiometer,
since the resistance of the latter is very large as compared with the former.

Potentiometer. — The potentiometer used is a combined potentiometer and
Wheatstone bridge, made by Wolff.1 In this type of instrument, the resist-

vwwwvwwv
R

./vwwwvw

AAA

KS ^7%

-^h ^S^ f¥S

ri^^ ~K£f K^

BODY

OVEN

Fig. 2. Complete wiring diagram of apparatus. Current from the battery B flows through the resist-
ances R, Vi, Vs, V3, and V4, and then divides, part flowing through the shunt S and part
through the potentiometer P, the total current finally returning to B through the resist-
ance M. The potentiometer, which is composed of 5 variable resistances is joined to the
switching arrangement, of which G2 connects the galvanometer G in circuit, T replaces
the thermal-junction system when testing, and 1, 2, 3, 4, etc., are connected to the thermal-
junctions at the body and the constant-temperature oven. The constantan wires are
indicated by the heavy lines. N is the standard cell, protected by the high resistance
O, and connected to the circuit through the double-contact key Gi. The switch K is for
convenience in bringing the galvanometer to rest.

'Wolff, Zeitsch. f. Instrumentenkunde, 1903, Oktober.

16 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

ance is kept constant regardless of the position of the contacts by the device
of two identical circuits, one of which is included between the sliding contacts
while the other is not; these circuits being so arranged mechanically that as
the resistance of one is decreased the resistance of the other is increased by
the same amount. This arrangement has the disadvantage that contact
resistance in the potentiometer circuit may affect not only the precision but
also the accuracy of the measurement. In choosing apparatus for similar
work, it should be noted that this is an unnecessary handicap, since the poten-
tiometer may be so designed as not to require any contact in this very import-
ant part of the circuit. Also for thermo-electrical work, the potentiometer
should have low resistance, so as to retain the full sensitiveness of the
apparatus.

The potentiometer shunt is embedded in a block of paraffin, together with
the brass binding posts of the potentiometer; also a similar block is used where
the copper wires join the binding posts which are connected to the moving
contacts. None of the knife switches G2, T, 1, 2, 3, 4, etc., contain any
junction of dissimilar metals, the circuit being copper throughout. Moreover,
these switches are mounted at a distance of about 1 meter from the observer
and are operated by means of long wooden rods. This construction is adopted
in view of the fact that in some parts of the circuit, namely, in the poten-
tiometer, the shunt, the switches just mentioned, the galvanometer, and the
thermal-junction systems, it is very important to reduce as much as possible
all stray electromotive forces.

The unavoidable junctions occur mostly in the form of reversed pairs; the
paraffin blocks, by surrounding both these junctions with a medium having an
appreciable mass, lessen the effect of transient fluctuations in the room temper-
ature; furthermore, as these blocks have a greater heat-carrying capacity than
air, they provide a better path for the transfer of heat between the two junc-
tions, thus tending to equalize the temperature of the two. The slender
wooden rods are used in connection with the switches as a further safeguard
at these points to prevent heating from the hand.

Standard cell. — The resistance M is furnished in the usual way with both
current- and potential-terminals. The standard cell N is a Weston Standard
Cell, No. 1565, provided with the usual certificate stating its electromotive
force. The following caution is expressed in the certificate: "To preserve
the constancy of this cell,itshould not be exposed to temperatures below 4° C,
and no current greater than 0.0001 ampere should be passed through it."
The insertion of the resistance 0 of 10,000 ohms assures the fulfilment of this
latter requirement, and at the same time leaves an arrangement amply sensi-
tive. The switch Gi is in the form of a double-contact key, which remains
open unless pressed, thus preventing the standard cell circuit from remaining
closed accidentally.

Galvanometer. — The galvanometer is a reflecting instrument of the Deprez-
d'Arsonval type, manufactured by Siemens & Halske. Among the advantages
of this instrument might be mentioned first, that provision is made whereby

METHODS AND APPARATUS. 17

the whole moving system may easily be taken out and replaced by another,
perhaps of different resistance or sensitiveness; second, that small windows
are provided at the top and bottom of the suspension strip, by means of which
it may easily be inspected or removed. The chief disadvantage for general
work is, perhaps, that when the instrument is set up the moving coil is not
visible and, the clearance being small, leveling becomes comparatively difficult.
The resistance, 50 ohms, is rather too high for work of this character; prob-
ably a smaller resistance could have been used and still leave an instrument
of sufficient sensitiveness. The galvanometer is not entirely free from thermal
electromotive forces; indeed, this could hardly be the case where a number
of metals are in circuit. This disturbing effect has been found to be less,
however, in an instrument purchased in 1907 than in a later model purchased
in 1909. With a view toward reducing extraneous electromotive forces in
the galvanometer, it has been shielded as much as possible from temperature
changes by placing over it a cork-lined wooden box. This is provided with
a door at the side for inspection, leveling, etc., and with a transparent celluloid
window in front through which the rays of light can pass. Since the use of
a telescope for reading was regarded as too tiring for repeated observations,
a ground-glass scale at a distance of almost 4 meters has been used, upon
which the reflection of the filament of an incandescent lamp is focussed. If
too long a scale distance should be used, in the attempt to increase the sensi-
tiveness, a blurred image will result, caused by slight imperfections in the
surface of the mirror.

The galvanometer has been mounted in the following way: A location
was chosen near a structural steel upright on the street floor of the building
and a strong shelf built out from the wall at this point. Upon the shelf was
placed a square block of cork, 3 or 4 cm. thick, to which was fastened a 1.25
centimeter iron plate, and on this the galvanometer was mounted. The very
slight vibration of the shelf resulting from the jar of the building is damped
out by the cork, which acts as a spring.

The copper wires running to the thermal junctions have a diameter of
1.63 millimeters up to within 1 or 2 meters from the junction itself. At this
point they are joined to smaller copper wires (0.455 millimeter), thus making
the junctions smaller and more flexible. The wiring should be done in such a
way as to leave no avoidable loops in the circuit; this will eliminate the induc-
tive action of neighboring circuits, which otherwise might cause annoying
deflections of the galvanometer.

THERMAL-JUNCTION SYSTEM.

Thermometers for internal temperatures. — Most of the junctions used for
measuring temperature in the natural and artificial cavities of the body are
simply twisted and soldered joints between two wires— one of constantan
(0.455 millimeter) and the other of copper (0.455 millimeter). For taking
internal temperatures a construction like A (fig. 3) is employed, in which the
two wires run side by side, one of them being inclosed in a rubber tube for

18

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

insulation. The wires are then twisted and soldered together in the usual
way, tied with silk, and finally covered with thin pure gum tubing. Before
insulating the bare copper wire, however, the precaution is taken to protect
it from the corrosive action of the sulphur in the rubber by "tinning" it
or covering it with solder. It was found that the lag of the thermometer,
due to the rubber tubing, was about 2.5 minutes;1 this was regarded as being
not too great.

For taking temperatures in the axilla a thermometer of the type illustrated
under B, fig. 3, recommends itself. Here the joint is made by twisting and
soldering two wires which approach each other from opposite directions, the
inclosure in tubing being the same as before.

Another type of thermometer is shown in C, fig. 3. Here one of the metals
of the junction touches the body without the intervention of any isolating
material, so that the conditions for the taking up of the temperature by the
thermometer are ideal. The copper element is made in the form of a very

Fig. 3. Types of thermal-junction thermometers used. A, junction inclosed in rubber tube, used
principally for internal measurements; B, same, arranged for use in axilla; C, junction in
which one metal touches body, for taking internal temperatures; D, modification of this
type for surface measurements.

thin hollow thimble, to the inside of which, at the end, is soldered the con-
stantan wire, properly insulated. A copper wire soldered to the thimble
completes the circuit. The connecting wires and the open end of the cap are
covered by rubber tubing, and tied with silk, after which the copper is silver-
plated. This arrangement fulfils the theoretical condition that both elements
should not touch the skin, and at the same time provides an excellent thermal
relation between the thermometer and the body whose temperature is being
measured.

Thermometers for surface temperature. — The attempts made to obtain accu-
rate measurements of the surface temperature were not successful, but a brief
description of the thermometers used may be of interest. Several types of
skin thermometers were constructed. At first the ordinary rubber-covered

'The method of testing the thermal -junction thermometers for lag was as follows: The
thermometer being tested was connected to the measuring circuit and suddenly thrust
into a flask of water at about body temperature. This caused a galvanometer deflection
which at first changed rapidly but gradually became more nearly constant and finally
could not be observed to change at all, the change in deflection corresponding to the
change in temperature of the junction. The length of time noted above (2.5 minutes)
is the interval elapsing from the instant when the thermometer was immersed until the
deflection had become constant.

METHODS AND APPARATUS.

19

thermometers, A or B, fig. 3, were used, these being held in place by a bandage;
afterwards they were pressed somewhat into the flesh by placing them under
small pieces of wood which were strapped in position. A later type is shown
in D, fig. 3. Here the general shape of the thermometer is along the lines
finally used by Gamgee.1 The support consists of a cork disk, somewhat
rounded on the face. To this is shellacked a piece of thin sheet copper, shaped

- ig. 4. Details of constant-temperature bath. The tube A, mounted in the block B, and inserted
in a bath of warm water in the Dewar flask D, serves as a support for the thermal-junction
wires C. The mercury thermometer E is inserted to the depth of the thermal-junctions.
The water in the flask is stirred by compressed air entering through the tube F.

so as to bulge outward from the support. This copper plate furnishes one of
the metals of the thermo-couple, a constantan wire soldered to the center of
the back supplying the other, and a copper wire, also soldered to the plate,
completing the circuit. The base is made of cork in order to give the apparatus
a smaller mass, and the copper is shaped in the manner described so that it may

'Gamgee, loc. cit.

20 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

press into the flesh and take up the deeper temperature. The thermometer is
held in place by a cloth strap. The junction itself must be shielded so that it
may take up the body-temperature, and yet this must not interfere with the
natural liberation of heat. These two conditions are incompatible, but the
shape of thermometer chosen seems to fulfil both as well as possible.

Thermal junctions used in the constant-temperature bath. — The thermal
j unctions used in the constant-temperature bath are all made in the same way.
The two small wires are slipped into separate capillary rubber tubes and a
soldered joint made exactly as in type A (fig. 3) previously described. The
different junctions are then supported in the following manner: A piece of
glass tubing (A, fig. 4) is used, about 15 centimeters long and having a 16
millimeter bore. The upper end of this tube is passed through a block of
wood B and secured with silk and shellac. Along the outside walls of the
tube the thermal-junction wires C are laid, and firmly tied with silk in such a
way as to leave the junctions protruding 1 or 2 centimeters from the bottom
of the tube. The ends of the junctions are carefully separated, and the
whole arrangement dipped in paraffin. The paraffined junctions, together
with the glass tube, are then immersed in water contained in a large spherical
Dewar vacuum flask D with silvered-glass, double walls. This flask has an
outside diameter of about 15 centimeters, the distance between the walls being
8 millimeters, the length of the neck approximately 10 centimeters, and the
capacity 1100 cubic centimeters.

A mercury thermometer, E, which indicates the temperature of the bath,
passes through the tube A to such a depth that its bulb lies very near the
thermal junctions and at the same level. This construction allows the ther-
mometer to take up the temperature of the junctions very closely. The
mercury thermometer is of the Beckmann type, having a range of 5° C, is
graduated in hundredths of a degree, and calibrated by the Physikalisch-
Technische Reichsanstalt. The true temperature, as obtained from the read-
ing of such a thermometer, would be expressed by the formula T = A-\-KR,
where T is the temperature desired, A being the zero reading of the thermome-
ter, K a calibration constant which equals the true value of a scale division
for the particular conditions of use, and R the reading.

CONSTANT-TEMPERATURE OVEN.

The flask D is placed in an oven, F (see fig. 5), in which the air is maintained
at a constant temperature by the use of a mercury thermostat G which auto-
matically supplies the proper amount of gas to a small burner H located
beneath the oven. This oven, which is of sheet metal and about 33X40X50
centimeters, is inclosed in a slightly larger asbestos case with a sheet-metal
bottom, the air space between the oven and the outside case being about 25
millimeters. The fronts of both are hinged; in the top are three holes, one for
the insertion of the thermostat, one for the mercury thermometer E, and one
for the insertion of the wires of the thermal-junction system. Through the
last opening is also inserted a mercury thermometer for indicating roughly the

METHODS AND APPARATUS.

21

temperature of the air in the oven, and a tube for compressed air. By means
of this tube compressed air, which has previously been passed through an
indicator outside of the oven, is conducted into a bottle of water placed in the
oven, and finally passes in a succession of bubbles up through the water in the
Dewar flask itself.

By automatically keeping the air in the oven at the same temperature as the
water in the flask, any small heat loss from the flask is avoided. The outer
air-space and asbestos casing also aid in the temperature control of the oven,
while the metal bottom assists in the equalization of the heat from the burner.

It was at first thought that, with the flask surrounded by ideal conditions,

Fig. 5. Constant-temperature oven. Inside the oven F, in the center, is shown the constant-tempera-
ture flask D, with the mercury thermometer E. On the right is the thermostat G which

rure nasK u, wim uie mercury uieriiiuinetei rj. v >n tiie rignt is tne tiieriiiustat <j which
supples gas to the burner H below the oven; at the left is the arrangement 1 1 supplying com-
pressed air for stirring the water in the flask D.

sufficient stratification could hardly exist to produce a sensible error in the
reading. It was found, however, that appreciable temperature differences did
exist in the flask and, although the thermometer bulb and thermal junctions
were all at the same level, it was considered advisable to provide some method
of stirring. For this reason, compressed air was introduced, being selected as
a convenient method for stirring the bath, especially in view of the fact that
the space available was small. By passing the air first through a vessel of
water inside the oven it is brought to the temperature of the water in the flask
and, still more important, is saturated with moisture at the same tempera-
ture, so that no heat is lost either by absorption or by evaporation.

22

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

To prevent cooling by evaporation from the surface, the water in the flask
was at first covered by a thin film of oil; but this necessitated such an elabo-
rate arrangement to protect the rubber tubing that the oil is now omitted,
with equally satisfactory results. The performance of the constant-tempora-
ture oven has proved very satisfactory, the temperature within the flask
frequently not changing more than 0.01° C. in an hour.

CALIBRATION OF MERCURY THERMOMETERS.

The following is an abstract of the calibrations of the various thermometers
used in the work, as given by the Physikalisch-Technische Reichsanstalt.
In the case of the Beckmann thermometers, data are given showing how the
constant K, previously mentioned,1 is determined. The tables of corrections
for variations in caliber have been omitted in the Beckmann calibrations, but
a statement is made regarding the maximum value of the correction.

Beckmann Thermometer PTR 40724.

Range.

Average tem-
perature of
exposed stem.

Value of scale

division Jena

glass 16111.

Correction.

Corrected

value of scale

division.

°c.

30-35
40-45

°c.

22
24

1.013
1.017

-0.008
-0.008

1.005
1.009

Since the thermometer is to be used at temperatures of 37° to 42° C, an
interpolation has been made in the above table, giving as the corrected value
of a scale division,

1 .005 + [(37 - 30) -h (40 - 30) ] (1 .009 - 1 .005) = 1 .008
No caliber correction greater than 0.005° C. is given, so that for readings
only to 0.01° C, this correction is negligible.

Beckmann Thermometer PTR 40723.

Range.

Average tern- Value of scale
perature of division Jena
exposed stem. glass 16lu.

Correction.

Corrected

value of scale

division.

°c.

30-35

40-45

°c.

22
24

1.013
1.017

-0.006
-0.006

1.007
1.011

This thermometer is to be used in calibrating at temperatures of 34° to 39° C.

The corrected value of a scale division is therefore:

1.007+ [(34 — 30)^(40-30)] (1.011-1.007) = 1.009

No caliber correction greater than 0.005° C. is given.

Richtcr Thermometer PTR 32689.

Range 34°-44° C, graduated in 0.01° C. Without sensible error throughout,
i. e., no correction so great as 0.005° C.

In calibrating a Beckmann thermometer in this laboratory, its zero point

was determined roughly, and then the thermometer was set by trial until the

'Page 20.

METHODS AND APPARATUS.

23

desired value was approximately obtained. A careful determination was then
made by tying the Beckmann and Richter thermometers together and immers-
ing the pair in a Dewar flask similar to that used in the constant-temperature
oven. The flask was filled with warm water stirred by compressed air, and
immersed in a large body of hot water in an outside pail, the temperature of
this outside water being regulated by an electric-coil heater. This heater is
simply a resistance wire inclosed in a water-tight spiral tube, having in its
outside electrical circuit a variable resistance, so that the amount of heating
can be controlled. Several simultaneous readings of the thermometers were
taken, as shown by the data given in table 1 which represent the determina-
tion of the zero point of Beckmann thermometer 40724, used in the constant-
temperature oven. The Beckmann reading, corrected for caliber errors, must
be multiplied by 1.008 — the constant determined from the above calibra-
tion— and subtracted from the true temperature in order to give the zero
point of the thermometer.

Table 1. — Determination of zero point, Beckmann thermometer PTR 40724.

Beckmann

t her mom-

Richter
thermometer
32689 reading.

eter 40724.

Corrected
reading

multiplied
by 1.008.

Zero point of

Beckmann

thermometer.

Deviation
from av.

Reading.

Corrected
reading.

39.04

1.735

1.731

1.75

37.29

0.010

39.04

1.735

1.731

1.74

37 . 30

.000

39.04

1.732

1.728

1.74

37.30

.000

39.04

1.728

1.724

1.74

37.30

.000

39.04

1.726

1.722

1.74

37.30

.000

39.04

1.725

1.721

1.73

37.31

.010

39.02

1.712

1.708

1.72

37.30

.000

39.01

1.702

1.698

1.71

37.30

.000

A v. =37.300

0.003

Thus the correct temperature as determined from a reading of this ther-
mometer is given by the formula 37.300+1. 008 X reading. When working only
to hundredths, the formula 37.30+1.01 Xreacling gives closer results at the
lower part of the scale, but 37.29 + 1.01 Xreading is better on higher readings.

METHOD OF OPERATING APPARATUS.

In measuring temperatures with this apparatus the procedure is first to
connect the partly discharged cell to the measuring circuit for a few minutes
in order to let the current become constant, and then carefully to depress the
key Gi. In general, a galvanometer deflection results, indicating that the
current differs from its standard value. By regulating the variables V3 and
V4, and also, if necessary, Vi and V2, this deflection is brought as nearly as
possible to zero, thus indicating that the current has closely enough its proper
value. The current having been adjusted, the next step is to close G2 and
one of the switches 1, 2, 3, 4, etc., according to which thermal junction is to be
used. In general a deflection results, which can be almost balanced by
properly moving the potentiometer contacts. The attempt is not made to

24 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

balance exactly, as this requires some time, but after the balance has been
obtained within perhaps 0.1° C, the potentiometer setting and the deflection
are observed and noted. From time to time the current is checked as at the
beginning, also the temperature of the constant-temperature bath is occasion-
ally taken and the correction for extraneous electromotive force determined.
For the purpose of making this last test the test switch T is provided. The
connections are such that if this switch is closed, instead of one of the switches
1, 2, 3, 4, etc., the apparatus is in the condition usual for a temperature
measurement, except that the thermal -junction system is replaced by a direct
copper connection. The electromotive force in this circuit should then be zero,
and if the potentiometer is set at zero, a balance should be obtained. If this
is not the case, a galvanometer deflection will result, indicating the presence
of an extraneous electromotive force. This error may be determined either
by changing the potentiometer setting until a balance is obtained, or else —
having a knowledge of the sensitiveness of the galvanometer — by interpreting
it directly from the deflection. The latter method, being quicker, is perhaps
preferable; it also frequently saves reversing the storage cell and standard
cell, which would be necessary in balancing if the stray electromotive force
happens to oppose the main voltage of the thermal-junction system.

CALIBRATION OF THERMAL JUNCTIONS.

In calibrating the thermal junctions, a Dewar flask was used, similar to that
in the constant-temperature oven. This was filled with water at about
body-temperature and immersed in a considerable mass of warm water in a
pail, the temperature of the outside water being controlled by an electric-coil
heater. The Beckmann thermometer (40723), already described, and all
the junctions to be calibrated were placed side by side and bound together
with rubber bands in such a way as to bring the junctions at about the middle
of the bulb, but without pressure on the bulb itself. The thermometer and
junctions were then inserted in the calibrating flask, the surrounding water
being stirred by compressed air from the supply in the constant-temperature
oven. After the temperature in the calibrating flask had become constant the
Beckmann thermometer was read, the necessary potentiometer readings were
made for each thermal junction, and the reading of the Beckmann thermometer
in the constant-temperature oven was taken. Usually four complete series
of readings were made as quickly as possible; their average furnished data
which showed the relation between temperature difference and potentiometer
balance for this point. After this another temperature was used in the cali-
brating flask and similar data obtained. In this way the junctions were
calibrated throughout the range of temperature difference likely to occur in
an actual experiment.1

'These conditions are also suitable fortesting the constantan wireforinhomogeneity. The
most important part of the circuit, namely, that where the temperature gradient is usually
steepest and most variable, occurs near the junction for use on the body. This region may be
explored by keeping the junction at a fixed temperature in the bath, meantime immersing
the wires to varying depths. A number of tests made in this way showed no change in the
galvanometer deflection, indicating that the wire was sufficiently homogeneous for this work.

Methods and apparatus.

25

Part of an actual calibration will serve to show the nature of the results
obtained. After the preliminary adjustment of the current the following
data were taken: First, the temperature in the flask, then as quickly as
possible the potentiometer readings for the junctions A, B, C, D, E, F, and G.
It might be remarked that the potentiometer setting was kept fixed throughout
and the deflections noted; this saved a great deal of time. These were
quickly followed by a second reading of the temperature in the flask, and also
a reading of the temperature in the constant oven. Finally the stray electro-
motive force was measured and the current balanced as before. Then the
series of observations was immediately repeated. The mercury thermometers
were read to 0.002° C, and the deflections to the nearest half millimeter.
The data are given in table 2.

Table 2. — Calibration of thermal junctions, February 1, 1911.

Initial temper-
ature in flask . .

Potentiometer

readings:
Junction A. . .
Junction B. . .
Junction C. . .
Junction D. . .
Junction E. . .
Junction F. . .
Junction G. . .

Final tempera-
ture in flask.

Temperature
in oven

Stray deflec-
tion

A verages

3.774

3.770

3 . 775

3.745

3.761

Setting.

Defl.

Setting.

Defl.

Setting.

Defl.

Setting.

Defl.

Setting

Defl.

ohms
18.00
18.00
18.00
18.00
18.00
18.00
18.00

mm.
±0.0
+5.0

+7.5
+5.0
+2.5
+7.0
+7.0

ohms
18.00
18.00
18.00
18.00
18.00
18.00
18.00

mm.
-1.5
+4.0
+6.0
+4.0
+1.0
+6.0
+6.0

ohms
18.00
18.00
18.00
18.00
18.00
18.00
18.00

mm.
-4.0
+ 1.5
+3.5
+2.0
-0.5
+4.0
+4.0

ohms
18.00
18.00
18.00
18.00
18.00
18.00
18.00

mm.
-5.5
±0.0
+2.5
±0.0
-2.5
+2.5
+2.0

ohms
18.00
18.00
18.00
18.00
18.00
18.00
18.00

mm.
-2.7
+2.6
+4.9
+2.7
+0.1
+4.9
+4.8

3.774

2.458
-)-3 0 mm.

3.770
2.458

+ 2.5 mm

3.775
2.459

+ 3 0 mm

3.740
2.459

-1-4 0 mm

3.760
2.459

-|-3 1 mm

Current bal-
ance1

6.8

ohms

0.7

ohms

6.6

ohms

6.(3

ohms

'Not used in computations. The figure given is the reading of the variable resistance when the current is balanced.
COMPUTATIONS FOR THE CALIBRATION.

The corrected potentiometer balance differs from the setting in two respects :
(1) correction for stray electromotive force must be made, and (2) since the
balance consists partly of a setting and partly of a deflection, the effect of
this deflection must be included.

The correction for stray electromotive force is obtained in direction and
amount by consideration of the following facts: The galvanometer connec-
tions are such that a positive deflection requires a decrease in the potentiom-
eter setting to bring it to 0; therefore, a positive stray deflection, such as is
seen in table 2, by demanding a further decrease in the potentiometer setting,
which is already 0, indicates a stray electromotive force opposite in direction
to the net electromotive force of the thermal-junction system. Hence, the

26 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

potentiometer setting would have been greater had it not been for the presence
of this extraneous electromotive force, and so the correction must be added.
The actual magnitude of the stray correction is determined from the galvan-
ometer sensitiveness and the average stray deflection. The sensitiveness
of the galvanometer has been found by trial to be such that when taking the
stray correction — which necessitates setting the potentiometer at 0 — a
deflection of 25 millimeters corresponds to a change in the potentiometer
setting of 1 ohm, so that a deflection of 1 millimeter corresponds to a change
in setting of 1 -f- 25 or 0.040 ohm. The average stray deflection in the calibra-
tion just given is 3.1 millimeters. This, it is seen, is equivalent to a change in
setting of 0.040X3.1 or 0.12 ohm, which is therefore the correction that must
be added to the setting on account of the stray electromotive force.

When taking the readings of the thermal junctions, the potentiometer
setting is no longer 0, but is increased in the present instance to 18 ohms.
This change increases the resistance of the galvanometer circuit and thus
reduces its sensitiveness, so that under the new conditions a deflection of
1 millimeter has been found by trial to correspond to a change in setting of
0.063 ohm. As before, a positive deflection is equivalent to a decreased
balance. Thus, the final corrected balances for the different junctions are:

A, 1S.00+0.12+2.7X0.063 = 1S.29

B, 18.00+0.12-2.6X0.063 = 17.96

C, 18.00+0.12-4.9X0.063 = 17.81

D, 18.00+0.12-2.7X0.063 = 17.95

E, 18.00+0.12-0.1X0.063 = 18.11

F, 18.00+0.12-4.9X0.063 = 17.81

G, 18.00+0.12-4.8X0.063 = 17.82

The temperature difference is determined from the average readings of the

two Beckmann thermometers, one in the constant-temperature oven, the other

in the calibrating flask. The temperature in the constant-temperature oven

is given by the formula previously deduced:1

Temperature in oven = 37 . 300 + 1 . 008 X reading

= 37. 300 + 1. 00SX2. 459=39. 779° C.

Similarly the temperature in the calibrating flask is given by the formula:

Temperature in flask = 34 . 365 + 1 . 009 X reading

= 34.365 + 1.009X3.761=38.160° C.

The temperature difference is then :

39.779-38.160 = 1.619° C.

The potentiometer balance corresponding to a certain temperature difference
has now been obtained for each of the several thermal junctions, and this
temperature difference accurately determined by means of the two mercury
thermometers. A knowledge of the relation between these two quantities
(1) potentiometer balance and (2) temperature difference, is the sole object
of calibrating. This relation was determined for a number of temperature
differences and the results expressed in a number of curves, one for each
junction. These curves are very nearly straight lines for the range and pre-

'See p. 23.

METHODS AND APPARATUS.

27

cision used. Slight differences will be noted among the several junctions in
the calibrations given. These are not due to experimental error, as the
figures reproduce themselves very well; the cause is probably to be found in
a slight inhomogeneity of the constantan wire at the different junctions. In
actual experimenting the potentiometer balance is obtained, and by means
of the calibration curves just described the corresponding value of the tem-
perature difference can at once be found.

A SAMPLE BODY-TEMPERATURE EXPERIMENT.

In an experiment the junctions are placed at the different points where
it is desired to obtain the temperature, being held in position when necessary
by a strap or bandage. The apparatus is then operated in the manner pre-
viously described, so as to obtain data for computing the temperatures at
the various points every 5 or 10 minutes, as the rate of temperature change
seems to require. A few observations from an actual experiment are given
in table 3, in which are noted: First, the time; next, an occasional balancing
of the current; then the potentiometer readings for the various junctions,
each reading consisting of a setting and a deflection as already described.
After these follows an occasional reading of the Beckmann thermometer in
the constant-temperature oven. Finally a column is provided for miscella-
neous remarks, including observations for extraneous electromotive force, etc.

Table 3. — Body-temperature experiment.
Date: March 1, 1911. Subject: C. H. H.

Time. .

Current
balance.

Potentiometer readings.

Con-
stant
oven-
tem-
pera-
ture
read-
ing.

Notes.

Junction A,
Deep1 rectum.

Junction B,
Shallow2 rectum.

Junction C,
Left axilla.

Junction D,
Mouth.

Setting.

Defl.

Setting.

Defl.

Setting.

Defl.

Setting.

Defl.

P. M.

lhllm
16
21
26

ohms

1.1

ohms
34.0
34.0
34.0
34.0

mm.

-2

±0

+ 1
+3

ohms
34.0
34.0
34.0
34.0

mm.
-3
-3
-1
±0

ohms
37.0
37.0
37.0
36.0

mm.
+ 1
+3
+8
-3

ohms
37.0
36.0
35.0
35.0

mm.

+6

+5

-4

-2

3.07

Stray

defl.=

+2 mm.

'Junction about 11 cm. deep in the rectum. -Junction about 7.5 cm. deep in the rectum.
COMPUTATIONS FOR THE EXPERIMENT.

The method of obtaining the temperatures at the different locations and
times specified involves very much the same type of computation as that used
in calibrating.1 The corrected potentiometer balance is obtained exactly as
in the calibration computations by adding two quantities to the setting: First,
the correction for extraneous electromotive force; and second, the deflection
which has been multiplied by a factor depending on the galvanometer sensi-

>See p. 25,

28

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

tiveness. Having determined the corrected potentiometer balance, the
temperature difference between the two junctions is found at once by refer-
ence to the calibration curves, where the relation between these two quantities
is shown. The oven-temperature is computed to the nearest hundredth
from the reading of the Beckmann thermometer. The body-temperature in
any particular case is then found by subtracting the temperature difference
from the temperature in the constant oven. The computations by means
of which the various temperatures in the foregoing sample experiment were
obtained are given in table 4.

Table 4. — Computations for the experiment.

Date: March 1, 1911. Subject: C. H. H.

Time.

Corrected potentiometer balance.

A B

P. M.

lhllm
16
21
26

lhll™
16
21

26

ohms
34.0+2X.04+2X.08 = 34.2
34.0+2X.04+0 =34.1
34. 0+2X. 04- IX. 08 = 34.0
34.0+2X.04-3X.08 = 33.9

ohms
34.0+2X.04+3X.08 = 34.3
34.0+2X.04+3X.08 = 34.3
34.0+2X.04+lX.08 = 34.2
34. 0+2X. 044-0 =34.1

c

D

ohms ohms
37. 0+2X.04-1X. 08 = 37.0 37. 0+2X .04-6X .08 = 36.6
37.0+2X.04-3X.08 = 36.8 36. 0+2X .04-5X .08 = 35.7
37.0+2X.04-8X.08 = 36.4 ! 35. 0+2X .04+4X .08 = 35.4
36.0+2X.04+3X.08 = 36.3 1 35. 0+2X .04+2X .08 = 35.2

Time.

Temperature difference
(from curves).

Oven-temperature.

Body-temperature.

A

B

C

D

A

Deep

rectum.

B

Shallow
rectum.

c

Left

axilla.

D

Mouth.

P. M.

°C.

°C.

°C.

°C.

°c.

°c.

°c.

°c.

°c.

lhll™

3.13

3.16

3.43

3.38

37.29+1.01X3.07

37.26 37.23

36 . 96

37.01

16

3.12

3.16

3.41

3.30

= 40.39

37.27 37.23

36.98

37.09

21

3.11

3.15

3.38

3.27

37.28 37.24

37.01

37.12

26

3.10

3.14

3.37

3.25

37.29 37.25

37.02

37.14

PRECISION OF MEASUREMENT.

To meet the approximate demands of a precision discussion, the potenti-
ometer balance may be assumed as directly proportional to the temperature
difference between the hot and cold thermal junctions; hence the relation
between the two can be expressed by a single factor, rather than by a curve.
An approximate value of this factor, by which the potentiometer balance
should be multiplied to give the temperature difference, is 0.094,

METHODS AND APPARATUS. 29

The body-temperature would then be expressed by the formula :

Tu=T0-BF
in which

Tu = unknown temperature
To = oven-temperature
B = potentiometer balance

F = factor showing relation between potentiometer balance and
temperature difference.

Assume in an average case: T0 = 40° C, B = 32, and F =0.094. This
will give for Tu a value of 40-0.094 X 32 = 37° C.

The precision of the various factors is determined as follows: T0 is the oven
temperature as read during the course of an experiment, and has been shown
in a previous paragraph to be expressed by the formula :

T0 = A+KR .
where

A = zero point of thermometer, which has been determined to at

least 0.01° C.
K = 1.01 = constant
R = reading, taken to the nearest 0.01° C.

B, the potentiometer balance, is determined in the last place by deflection,
which is read to the nearest half-division. The sensitiveness of the galva-
nometer in this case is such that a deflection of 1 division corresponds to a
change in B of 0.072 ohm. Hence the average deviation in B is 0.036 ohm.

F is obtained by calibration. In calibrating, the following data are ob-
tained: To i, the oven temperature, which may be taken as 40° C; Tfh the
temperature in the calibrating flask, for instance, 37° C; and Bh the potenti-
ometer balance, 32. From these the quantity F= (Toi—Tfo) -i-Bi is com-
puted. In calibrating, the temperatures are taken more precisely than in an
experiment, and this involves not only a closer reading, but a better deter-
mination of the zero point of the thermometers. As a matter of fact the
reading is taken to 0.002° C; and the zero known to 0.003° C. Therefore we
may say, similarly to the above, To^ =A'+ K'R' and Tf, =A" +K"R", where
A' and A" are known to 0.003°C; K' and K" are constants; and R/ and R"
are known to 0.002°C. Bh like B, is known to 0.036.

The complete expression for the unknown temperature is then as follows:

Tu = A+KR-B{A'+K'R')-(A" + K"R")

B\

The average deviations of the variables are :

A, a.d. = 0.01; R, a.d. = 0.01; B, a.d.= 0.036; A', a.d. = 0.003;
R', a.d.= 0.002; A", a.d. = 0.003; R", a.d. =0.002; Bh a.d. =0.036.

The constants K, K', and K" each have the value 1.01.

30 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

The effect on the final result of the deviation in each component is obtained
by the aid of the differential calculus. Adopting the usual notation:

&A =0.01 Mi = A' X0.01=0.01

Afi _ (A' + A-^)-U» + *"*") XQm = l X0.036 = 0.0034

B\ 32

AA' = -- X 0.003 = 0.003 Mi' = — - X0.002 = 0.002

Bi Bx

\A" = — X 0.003 = 0.003 Mi" = -— X 0.002 = 0.002

Agi=fi'[(^ + A-^-(A" + A-^)]x()036=3 X0036 = 00034

(Bi)" 32

The deviation in the final result will then be

A - V (.01)2 + (.01)2 + (.0034)2 + (.003)2 + (.002)2 + (.003)2 + (.002)2 + (.0034) 2

= 0.016° C.
It is thus seen that the deviation expected in the body-temperature,
caused by the deviations in the various components, is 0.016° C; that is, each
temperature is measured to 0.01° or 0.02° C. It should be remembered,
moreover, that the primary object of this study is to determine the temper-
ature differences between different points of the body rather than the absolute
temperatures. A number of circumstances can be conceived which might
cause an error in the absolute determination of temperature, but which would
be without effect on the difference between two temperatures. The results
stated therefore are regarded as singularly good.

LATER MODIFICATION OF THE APPARATUS.

After the conclusion of this research, it was desired to extend the application
of the apparatus to the determination of the rectal temperatures of subjects
in the respiration calorimeters installed in this laboratory. It was thought
undesirable, however, to reserve the Wolff potentiometer for this special
work, as to do so would preclude its being used for any other measurements;
therefore a special potentiometer for body-temperature measurements has
been constructed. The circuit arrangement of this instrument is somewhat
different from the ordinary potentiometer, and was suggested informally
to one of the writers by Dr. Walter P. White, of the Geophysical Laboratory
of the Carnegie Institution of Washington in Washington, D. C. It is a
pleasure here to acknowledge our indebtedness to Dr. White, whose unusual
experience with thermal junctions made his suggestions doubly valuable.

The new arrangement completely removes all sliding contacts from the
galvanometer circuit and thus frees this important circuit from the thermal
electromotive forces which are developed by the usual type of sliding contact.
An elementary diagram of the apparatus is shown in fig. 6. The battery B

METHODS AND APPARATUS.

31

sends a current through the circuit B-P-D-R-A-B, this current being meas-
ured by the ammeter A. The contact P may be moved until the fall in
potential along P-D, due to the battery current, is just equal to the voltage
of the thermal-junction system TT. When this condition is fulfilled— as
indicated by the absence of a galvanometer deflection — the voltage of the
thermal-junction system may be computed directly from the constants of
the apparatus. As before, however, the temperature difference between the
junctions rather than their voltage is desired; and this may be obtained in
the usual way by calibration.

The complete wiring diagram is shown in fig. 7. It will be noticed that, as
in the older type of apparatus, the ammeter A is replaced
by a standard cell N and galvanometer; also a variable
resistance V is included in the main circuit for adjusting
the current always to approximately the same value j1 and
the galvanometer is provided with a number of switches
by means of which it may be connected to any one of a
series of thermal-junction pairs, or to the standard cell
circuit. The circuit has a great many features in common
with that of the earlier apparatus previously described in
detail,2 and these need not be considered again at this
point. Some differences, however, will be noted. The
galvanometer sensitiveness is independent of the position
of the contact P, since moving this contact in no way
affects the resistance of the galvanometer circuit. The
sensitiveness being constant, a resistance W has been
inserted in the galvanometer circuit, and by this means
the sensitiveness adjusted until the deflection reads
directly in hundredths of a degree. No special provision
is made for reversing B and N, as experience with the
earlier apparatus showed this to be unnecessary. The
new apparatus differs from the old, also, in that the ther-
mometer must be detachable. Two heavy wires have
therefore been run to two metal blocks in each calorimeter,
and to these the thermometer can easily be attached. It will be noted in fig. 7
that each calorimeter is not provided with an entirely independent set of
connections, but that the chair calorimeter and calorimeter No. 4 are connected
in parallel, as are also calorimeters Nos. 3 and 5. This is allowable because
other considerations prevent the calorimeters thus joined from ever being
used at the same time.

Fig. 6. Elementary wir-
ing diagram of mod-
ified apparatus. Cur-
rent from the battery
B flows through I'D,
this being part of the
slide wire CD, then
through the resistance
R and finally returns
to the battery through
the ammeter A. The
thermal junction sys-
tem TT is connected
through the galvan-
ometer G to the points
C and D, this circuit
being free from sliding
contact.

'It will be seen that the method as described is approximate only, and not exact, since the
measuring current changes with each position of P. The error thus introduced may be made
negligibly small for any case by making R sufficiently large as compared with CD. The
resistance CD should be kept small from another standpoint as well, namely, that of sensi-
tiveness. By the use of some kind of compensating resistance, equal to CD and arranged
so as to be decreased as CD is increased, and vice-versa, the arrangement can be made exact.

2See pp. 14-22.

32

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

The apparatus is designed to measure temperatures to 0.02° C, and has
a range of 8° C. The voltage of the cell B is 1.4 volts; that of N, 1.0197 volts.

vwwvwwwVi
o

tA'VVWWWVWV

M

CALORIMETERS
BED CHAIR NO.3 N0.4 NQ5

OVEN

Fig. 7. Complete wiring diagram of modified apparatus. Current from the battery B flows through
a portion (PD) of the slide wire CD, then through the resistances V and It, and returns to the
battery through the resistance M. The points C and D are connected without sliding
contact to the switching arrangement, of which G? connects the galvanometer G in circuit, T
replaces the thermal junction system when testing, and 1, 2, and 3 are connected to the thermal
junctions in the calorimeters and the constant-temperature oven. The constantan wires are
indicated by the heavy lines; the calorimeter thermometers are detachable at the small
circles. W is a resistance for adjusting the galvanometer sensitiveness. N is the standard
cell, protected by the high resistance O, and connected to the circuit through the double con-
tact key Gi. The switch K is for convenience in bringing the galvanometer to rest.

METHODS AND APPARATl S.

33

Copper-constantan couples are used, as previously. The slide wire C-D has
a resistance of 0.372 ohm, and is divided into 400 divisions, each of which
represents 0.02° C. temperature difference; M has a value of about 1200
ohms; and R, about 400 ohms. The maximum resistance of V is about 100
ohms; this should be variable in steps of about 1 ohm each. The value of
W has not been measured, this resistance having been adjusted by trial.
0,as before, is 10,000 ohms. For B a dry cell is used, from which a measuring
current of about 0.00086 ampere is drawn; N is the Weston Standard cell used

Fig. 8. Detachable thermometer lor use inside the calorimeter, with connections. A and E are of

constantan; B and F of copper.

previously. The potentiometer C-D consists of a 0.6 millimeter manganin
wire, arranged in the form of a circle, the sliding contact P being operated by a
knob at the center. The resistances M, R, V, and O are of manganin.

The constantan wire from the constant-temperature flask to the inside of
the calorimeter is 2.05 millimeters in diameter, insulated with rubber and
covered with a protecting braid. As will be seen in fig. 8, this wire is soldered

34 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

at the calorimeter to a small constantan block A, and in the same way the
copper wire running to the calorimeter is soldered to a small copper block B.
These blocks are mounted on a hard-rubber base C, and are provided with
binding screws of constantan and copper, respectively, by means of which the
thermal junction may be connected to the circuit without the intervention
of any metal other than the two required for the thermometer itself.

The thermometer consists of two wires 1.6 meters long, 0.0455 millimeters
in diameter, of constantan and copper respectively, well insulated, and soldered
together at one end D. At the other end the wires are screwed to two flat
terminals of constantan E and copper F, which are shaped to be received by
the binding screws already mentioned. These flat terminals are mounted
on a hard-rubber block G to which the wires are fastened in such away as to
make the joint absolutely rigid. The wires are covered by a 6.4 millimeter
rubber tube H down to some 25 centimeters from the junction itself; this
tube is protected by a spiral spring I at the point where it leaves the hard-
rubber block G. This comparatively heavy tubing is continued by a smaller
thin-walled rubber tube J for the remainder of the distance to the thermal
junction; this thin tubing fits tightly around the wires and is closed at the end
D by being tied tightly with silk.

It should be remarked that considerable trouble has been experienced by
extraneous electromotive forces developed at the point where the constantan
wire from the thermal junction is soldered to the flat constantan terminal E.
This stray electromotive force has been found to be reduced practically to
zero when the soldered connection is replaced by a clamp connection, made
by fastening the wire under the head of a small constantan screw, without
the use of solder. Apparently in this case the electromotive force is due not
to difference in the constitution of the two pieces of metal, but rather to the
unbalanced effect of the constantan-solder and solder-constantan couples.
This leads to the conclusion that when it is necesary to solder two pieces of
metal of identical constitution together, stray electromotive forces will be
less likely to be developed if the two pieces have the same size and shape and
are surrounded by as nearly as possible the same conditions of heat loss.

The operation of the apparatus is identical in procedure with the earlier
form. The current is first balanced, after which the potentiometer balance
is found, partly by setting, partly by deflection. Occasional observations
are also required of the temperature in the oven and the stray electromotive
force.

DISCUSSION OF RESULTS. 35

Part III. — Discussion of Results.

While this investigation was primarily undertaken to study simultaneously
the temperature in different parts of the body, many secondary points of
considerable importance were naturally encountered in the process of the
investigation.

THERMAL GRADIENT OF THE BODY.

The method of electrical measurement here outlined, owing to its extreme
sensitiveness and delicacy, is admirably adapted for a study of the thermal
gradient of the body. As has been previously shown, with an internal body-
temperature of not far from 37° C. and a surface temperature of about 32° C.
one would expect normally a thermal gradient. The exact significance of
this gradient may be better understood after a consideration of certain points
with regard to the physical structure of the body. If the highest heat pro-
duction were at the exact center of the body and there was a definite thermal
gradient from the center to the skin, it is obvious that the measurement of
body-temperature, particularly the average body-temperature, would present
almost insuperable difficulties. One could not select a point half-way between
the surface of the skin and the center of the body and assume that the tempera-
ture at this point would represent the average body-temperature, since there
would be no way of obtaining a record of this temperature. On the other
hand, if the thermal gradient rose sharply for the first few centimeters beneath
the surface of the skin and soon reached a point beyond which the body
temperature was not materially increased, the problem would be much less
complicated. If, as is frequently the case, we desire to note the total amount
of heat actually latent in the body at a given time, we must know the body-
temperature as nearly as possible. Consequently a study of the thermal
gradient was first made.

METHOD OF STUDYING THE THERMAL GRADIENT.

In studying the thermal gradient, the rectum was used with men, and the
rectum and the vagina with women, both being deep cavities into which the
thermal junctions could be inserted for a considerable distance. It is obvious
that at the entrance of either of these cavities the temperature will be low, i. e.,
that of the environment, but as the thermal junction is inserted deeper into
the cavity, the temperature more nearly approximates that of the interior
portion of the body. The important point to note, then, is the depth of inser-
tion required to obtain the maximum temperature. For this purpose, two ther-
mal junctions were inclosed in a single tube, and bound together in such a way
that one was exactly 3.5 centimeters from the other. This tube was then
inserted in the cavity to be studied, so that the deeper junction was approxi-
mately 10 centimeters within the cavity and the other accordingly 6.5 centi-
meters. Readings were taken until constancy had been obtained; then both
thermometers were withdrawn to a new location in the cavity, and the meas-
urement repeated. By this means the whole region was studied, the two ther-

36

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

mometers allowing simultaneous observations, each serving as a check upon
the other. With women, observations could be made simultaneously in the
rectum and the vagina.

EXPERIMENTAL RESULTS.

The results are expressed in the form of curves (see figs. 9, 10, 11, 12, and 13),
in which the depths of insertion are expressed by horizontal distances, the cor-
responding temperatures being represented vertically. The records for rectal
observations are marked RD and Rs for the deep and shallow temperatures
respectively; in a similar manner the curves for the deep and shallow vagina
are designated by VD and Vs. In some instances, when only a single thermom-
eter was used in either cavity, the subscript is naturally omitted.

372°C

37.0

£ 36 8

3

u 366
CL

z

Id

*" 36.4-

36.2

36.0

>/>

s /

t

1
1

/r

1 /

1/

1/

'

//

1

7CMS.

0 12 3 4-5

DEPTH
Fig. 9. Observations on thermal gradient, with Mrs. B— 1.

In the experiment represented by fig. 9, observations were made on a woman
(Mrs. B — 1) with one thermometer in the rectum and a second in the vagina,
the double thermometer not being

used in either case. The actual tern- Table 5.— Thermal gradient observations.
perature observations are given in
table 5.

The results show that at a depth of
3 centimeters in either cavity the tem-
perature was over a degree lower than
at a depth of 7 centimeters. The rise
was rather regular and gradual up to
5 centimeters; beyond that point the
rise was much slower and between G
and 7 centimeters it nearly ceased, in-
dicating that in this case and under the conditions of the experiment, the maxi-
mum body-temperature was reached when the thermometer was inserted G or
7 centimeters in the vagina or the rectum.

Rectal thermometer.

Vaginal thermometer.

Insertion.

Temperature.

Insertion.

Temperature.

cm.

°c.

cm.

°c.

7

37.20

7

37.12

6

37.17

6

37.11

5

36.98

5

36.98

4

36.59

4

36.80

3

36.09

3

36.00

DISCUSSION OF RESULTS.

37

37.0 C ■

Rd

36.8

p.-

' ?

36.6

/

36.4
36.2
36.0

— f-f-

/

t j

/

7

«{

/

UJ 35.8

K

D

< 35.6

a:
id
a.

i

i

/

i

;

/

^ 35.4
UJ

h

35.2

j

i—

j

/

35.0
34.8
346
34.4
34.2

• (

f"

i
i

/

i

f

i
1
i
i

f

.T4.0

i
i

6

5 6 7
DEPTH

10

II I2CMS.

Fig. 10. Observations on thermal gradient, with C. H. H.

In the experiment represented by fig. 10, a double thermometer was used in
the rectum, one of the laboratory assistants (C. H. H.) serving as a subject.
It is interesting to note from the curves that between the depths of 0.5 centi-
meters and 6 centimeters, there is a difference in temperature amounting to
2.72° C. The curves rise very rapidly until the depth of 4 centimeters is
reached, continuing to rise much more slowly for the next 2 centimeters.
Apparently with this subject the temperature reached its highest point at a

38

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

depth of about 6 centimeters, and from 6 to 12 centimeters there was no material
variation.

37.6 C

2 3 4 5 6 7 8

DEPTH

Fig. 11. Observations on thermal gradient, with Mrs. B — I,

IOCMS.-

The experimental results shown in fig. 11 were obtained with the woman
subject previously mentioned, a double thermometer being used in the vagina
and a single thermometer in the rectum. The curves show in a general way
the characteristics of the curves in the preceding tests, although the gradient
is not so sharply indicated.

37 2°C

37.0

36.8

U
or

i_ 36.6
<

UJ

0.

£ 36.4

LJ

h

36.2

36.0

35. 8

Rd_^

/

Rs
e

/

/

/ /

f /

/
i
/

/

/

/

•

/

/

/
/
/

J

8 CMS.

DEPTH
Fig. 12. Observations on thermal gradient, with J. J. C.

A thermal-gradient experiment was made with another laboratory assistant
(J. J. C.) in which a double thermometer was used in the rectum, the results
being shown in fig. 12. With this subject the temperature at a depth of 0.5

DISCUSSION OF liESl 1/1 S.

39

centimeters was 35.80° C, and at 8 centimeters 37.03° C. No material differ-
ences were noted between 6 and 8 centimeters. As usual the gradient rose
very sharply up to a depth of 6 centimeters, after which the temperature
remained practically constant.

The records for a third experiment with the woman subject are given in fig.
13; in this experiment a single thermometer was used in the vagina and a
double thermometer in the rectum. The temperature rose very rapidly until
about 5 centimeters was reached ; afterwards it remained essentially constant
for the remaining distance between 5 and 10 centimeters, beyond which point
it was not studied. The temperature at 2 centimeters was about 36.8° C. and
at 10 centimeters 37.3° C, showing a difference of approximately 0.5° C.

374 C

37.2

UJ

D

en

UJ

o.

u

h

37 0

36.8

36.6

36.4-

10 CMS.

Fig. 13. Observations on thermal gradient, with Mrs. B — 1.
GENERAL CONCLUSIONS WITH REGARD TO THE THERMAL GRADIENT.

It is apparent, therefore, that the thermal gradient between the temperature
at the surface of the body and at a depth of about 5 centimeters is quite notice-
able; evidently beyond 5 centimeters the body-temperature is essentially at
its maximum. It has been neither disproved nor shown by this study, of
course, that the temperature may not be actually higher in the liver or in some
other active organs of the body; indeed, it is to be expected that where there is
special metabolic activity, as in the liver and other glands, there might be a
somewhat higher temperature. On the other hand, Rancken and Tigerstedt,1
who found that ordinarily the temperature in the stomach was about 0.1° C.
higher than that in the rectum, were unable to note any rise in temperature
during the first hour of active digestion, except such as was due to the heat of
the food. However, in finding the average temperature of the human body,
it appears safe to say that the temperature rises to its highest point at a depth
of 6 to 7 centimeters.

'Rancken and Tigerstedt, Biochem. Zeitsch., 1C08, 11, p. 36.

40 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

From the very sharp gradient, it may be easily inferred that the surface
temperatures of the body, or those slightly below the surface, are liable to the
greatest errors in determination, and consequently, as ordinarily measured,
they can have but little physiological significance.

SELECTION OF LOCALITIES FOR SIMULTANEOUS MEASUREMENT
OF FLUCTUATIONS IN BODY-TEMPERATURE.

NATURAL CAVITIES.

The rectum and the vagina used alone are not especially suitable for study-
ing the constancy or the lack of constancy of temperature fluctuations in
different parts of the body, since these two cavities are side by side. Unfortu-
nately no other cavity presents such ideal conditions for the study of fluctua-
tions in body-temperature as do these, the only other openings which could be
used being the mouth and the oesophagus. While it has long been the custom
of physicians and physiologists to take temperatures in the mouth, certain
grave objections have been raised to the use of this locality, and it is obvious
that a more careful study of buccal temperature should be made before rely-
ing upon this cavity for exact temperature measurements. Accordingly,
a considerable amount of experimenting was done in connection with this
research to test the reliability of temperatures taken in the mouth.

TEMPERATURE MEASUREMENTS IN THE MOUTH.

A variety of methods were used for taking mouth temperatures, but even
when extreme care was observed, the results were unsatisfactory. The experi-
ment was tried, for instance, of inserting a thermal junction beneath the
tongue and recording the temperature until it became constant; the thermal
junction was then withdrawn and immediately replaced by a carefully cali-
brated clinical thermometer1 which was allowed to remain in position for 5
minutes. The temperatures indicated by the two measurements were not
identical, the thermal junction giving results 0.2° to 0.4° F. lower. Again, the
mercurial thermometer and the thermal junction were fastened together and
inserted beneath the tongue for a period of possibly 20 minutes, the thermal
junction being read at regular intervals until a maximum was reached, this
requiring some 15 minutes. When the maximal reading was compared with
the clinical thermometer reading it was found to be 0.1° to 0.3° F. lower than
the latter.

This continual disagreement led to a doubt as to the wisdom of using this
locality for taking temperature records, and of the clinical thermometer as a
standard. As a further test, the experiment was then tried of tying two
clinical thermometers together, inserting them in the mouth, and removing
them at the end of 5 minutes to take the records. After the thermometers
had been shaken down, they were replaced in the mouth and further 5-minute

'Inasmuch as the Fahrenheit degree is employed in graduating practically all of the
mercurial clinical thermometers used in this country, this unit is made the basis of the
discussion of buccal temperatures, although in all other sections of the report the centigrade
scale is regularly used.

DISCISSION OF UKSII.TS.

41

records taken. For approximately 10 minutes the readings of the two ther-
mometers disagreed; afterwards they were identical. This led to the belief
that unequal conditions of heat loss caused the discrepancies observed in the
earlier readings. To equalize this heat loss, warm water was held in the mout h
and simultaneous records taken with the thermal junction and the clinical
thermometer, the water acting in a way as a protection from outside tempera-
ture influences. The results showed the thermal junction in one instance to
have the same maximal temperature as the clinical thermometer, but usually
it was 0.2° to 0.3° F. lower. Then the thermal junction was embedded in
paraffin, and its records compared with those of the clinical thermometer.
The results showed that even under these conditions the thermal junction
readings ranged from 0.1° higher to 0.3° F. lower than those of the clinical
thermometer.

98.6'F

96.6

6 7 8

MINUTES

13

F. 14. Observations showing the rise of temperature in the mouth.
(I) clinical thermometer, (II) thermal-junction thermometer.

Finally the design of the thermal junction was changed. In all of the
previous experimenting with the mouth temperature, a junction of either type
A or C (fig. 3) was used.' The new junction was built with a heavy, pear-
shaped, copper element, the bulb of which was about 1 centimeter in diameter.
The constantan element, a small wire, was soldered to the copper at about the
center of the bulb, by means of a small hole drilled through to this point.
This junction was then compared with the clinical thermometer, as in the
previous experiments. The results obtained from six comparisons show that
the thermal junction and clinical thermometer agreed in three cases, the
thermal junction was 0.1° F. higher than the clinical thermometer in two
cases, and 0.2° F. higher in the remaining case.

lSee p. 18.

42 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

Two curves are reproduced in fig. 14, showing records obtained in the mouth
with a clinical thermometer and with a thermal-junction thermometer. In
these curves the intervals of time during which the thermometer was held in
the mouth are expressed by horizontal distances, the corresponding tempera-
tures being represented vertically.

Curve I may be of interest in showing that a clinical thermometer inserted
beneath the tongue does not attain its maximal temperature for a considerable
time. The curve was obtained in the following way: A subject carefully
trained to the use of a clinical thermometer, after preparing for the experiment
by keeping his mouth closed for perhaps 10 minutes, seated himself and placed
a clinical thermometer beneath the tongue, allowing it to remain for 15
seconds. He then removed the thermometer, read it, quietly shook it down,
and replaced it, this time for 30 seconds. This procedure was repeated, the
thermometer being kept in place during constantly increasing periods of time
up to 13 minutes. Even after the thermometer had been inserted 7 minutes,
a further rise of over 0.1° F. was noted; this, it would seem, must have been
caused by the slowness of the cavity in warming up, as the true body-temperature
must have been slowly falling on account of the quietness of the subject.

Curve II was obtained shortly afterwards with the thermal junction; in
this case, however, the procedure was greatly simplified. The thermometer
was inserted at a definite instant and its temperature taken each minute by
means of the usual measuring apparatus. The curve is similar in shape to that
obtained with the clinical thermometer; the maximal temperature indicated
is, however, somewhat lower.

Having obtained such inconstant results in the mouth with these two types
of thermometers, an attempt was made to find out if better comparisons could
not be obtained in the rectum. The experiment was accordingly tried of
inserting the thermal junction about 7 centimeters into the rectum, taking
readings for perhaps 15 minutes until constancy was assured, then removing
the thermometer and replacing it by a clinical thermometer inserted to the
same depth. The results given by the thermal junction varied from 0.1° F.
lower to 0.2° F. higher than the clinical thermometer.

When the thermal junction and the clinical thermometer were fastened
together in a single rubber tube and inserted in the rectum, the maximal
reading of the thermal junction in one case was identical with that of the
clinical thermometer, while in another instance it was 0.2° F. lower than the
clinical thermometer. This pointed to an error in the thermal-junction reading,
but a further test was made which showed that the reading of the clinical ther-
mometer was by no means an indisputable standard. In this test, two
carefully calibrated clinical thermometers were inserted in a rubber tube and
placed in the rectum. After 10 minutes they were withdrawn, carefully
removed from the tube, and read. The readings were not identical, but
disagreed by 0.1° to 0.2° F.

In order to make sure that the presence of the rubber tubing did not vitiate
the results, a thermal junction and a clinical thermometer were inclosed in

DISCUSSION OF RESULTS. 43

rubber tubing exactly as for an experiment. They were then immersed in a
bath of warm water and readings were taken continuously of the thermal j unc-
tion temperature; at the end of 10 minutes, they were withdrawn from the
water, the tubing removed, and the clinical thermometer read. In one test, at
a temperature of 98° F., the reading of the clinical thermometer agreed exactly
with the record obtained with the thermal junction; in a second test, at a
temperature of about 99.4° F., the records disagreed by 0.4° F. Shortly after-
wards the clinical thermometer used was broken, so that this result could not
be verified.

Although no definite conclusion was reached, these comparison experiments
left in the minds of the experimenters grave doubts as to the feasibility of
using the mouth in temperature observations, and also an indefinite distrust
of the clinical thermometer for accurate work. It should be stated that a
type of mercurial thermometer was used that probably represented as good
an instrument as is ordinarily available, selection being made from a number
of thermometers that had been simultaneously calibrated. It is evident that
the rise of mercury in the thread in a series of impulses may easily lead to
errors as great as 0.2° F., and hence whatever value the mercury self-register-
ing thermometer has to the clinician, it can have little, if any, value when
accurate body-temperature measurements are desired.

ARTIFICIAL CAVITIES.

In the effort to find favorable places for making temperature observations,
certain artificial cavities, such as the closed axilla or groin, or between the
closed hands, were carefully studied. These so-called cavities are really
more or less exposed portions of the skin, the configuration of which has been
changed so as to form a closed pocket. On account of the large amount of
subcutaneous fat, greater possibilities for finding such cavities are afforded
with women than with men; accordingly, in experiments with a woman
attempts were made to study the temperature fluctuations by means of a
thermometer placed between the arm and the breast, between the two breasts,
and in different parts of the body more or less inclosed by flesh.

The one great difficulty with all of these so-called artificial cavities is that
they require considerable time to warm them to the maximum temperature.
The temperature of the exposed skin before the cavity is made may be as low
as 32° C, while that in the inclosed cavity, equilibrium having once been
established, may be 36° or 37° C. At the beginning of a test, therefore, the
cavity will have a temperature not far from 32° C, and will gradually become
warmed to 36° C. or thereabouts, before it can be used for comparison with
natural cavities, such as the rectum and the vagina. The warming-up period
usually occupies 20 or 30 minutes for the axilla, the length of the period
depending principally on the closure obtained. For the cavities made by the
groin and by the hands, the preliminary warming period is even longer, since
these cavities are formed from places ordinarily less inclosed than the axilla.
To avoid this loss of time, a hot-water bottle, previously filled with water at

44 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

a temperature 2° or 3° C. higher than that of the body, was placed in the
inclosed portion for 5 minutes before inserting the thermometer. By this
means the cavity was preheated to approximately normal temperature, and
came to its final value in about half of the time previously required.

SIMULTANEOUS OBSERVATIONS OF BODY-TEMPERATURE IN

DIFFERENT LOCALITIES.

From the previous discussion of the thermal gradient it is obvious that it
would be practically impossible to determine the average temperature of the
human bod}-, although as a gradient effect is most marked in the last peripheral
4 centimeters of body material, a large portion of the body would have a tem-
perature not far from that of the rectum. Fortunately, for purposes of calorim-
etry, what is chiefly desired is the fluctuations in temperature from hour to
hour or from day to day. One must be sure that the fluctuations in tempera-
ture throughout the whole body are of equal value, since otherwise no accurate
estimate can be made of the total heat gained or lost due to a rise or fall in
temperature.

The temperature of the body rarely remains constant, even for so short a
time as 10 minutes; this was shown by a series of observations1 made every 4
minutes for several days in which practically no two consecutive readings were
exactly alike. The normal temperature rhythm, with a maximum between 4
and 5 o'clock in the afternoon and a minimum between 2 and 5 o'clock in the
morning, is considerably accentuated by a number of extraneous factors, but
even with the subject lying in bed without food, or with a small amount of food,
the range in temperature in 24 hours may be as high with a normal subject
as 1.3° C. (2.3° F.).

In the collected results of body-temperature measurements obtained in a
large number of experiments with the respiration calorimeter at Wesleyan
University, Benedict and Carpenter2 report that the average body-temperature
in experiments with food was 36.82° C. (98.3° F.),the minimum being 35.67° C,
and the maximum, 38.23° C. The average range for all of the experiments
was 0.96° C, the minimum range, 0.44° C, and the maximum, 1.64° C. In a
series of experiments with 11 subjects in which food was not taken, covering in
all 31 days of 24 hours each, the average temperature of the subjects was
36.67° C. (98° F.). The minimum temperature observed was 35.53° C, and
the maximum, 37.74° C. The average range in temperature was 0.77° C, the
minimum range being 0.38° C, and the maximum, 1.36° C. (2.45° F.).

The large number of observations made on body-temperature by electrical
methods in the last few years have shown that there are fluctuations aside
from the normal rhythm — fluctuations that can be produced artificially; for
example, changing from a lying to a sitting position will cause a slight rise in
temperature, as will also the taking of hot drinks or hot food. Eating a meal
ma}' cause a rise of as much as 0.15° C. in 20 minutes, and severe muscular

■Benedict and Snell, Archiv f. d. ges. Physiol., 1902, 90, p. 33.

'Benedict and Carpenter, Publication No. 126, Carnegie Institution of Washington,
1910, p. 121.

DISCUSSION OF RESULTS.

45

work as much as 0.50° C. in 30 minutes. In fact, any increase in body activity
tends to increase the temperature. On the other hand, muscular relaxation
and sleep, as well as cold water and cold food, will cause a fall in temperature.
Consequently, in certain of our experiments the effort was made by various
means to produce artificially these fluctuations in temperature in order to
enable us to secure better conditions for measurements of temperature fluctua-
tions in different parts of the body.

The 24 experiments in this study of body-temperature were all made with
healthy people, including five men and one woman; the data regarding the
age, height, and weight of these subjects may be found in table 6. With but
few interruptions, the experiments continued daily from the beginning of Janu-
ary until the middle of March, 1911. The experimental conditions remained
essentially the same throughout the series, save that in all experiments prior to
January 27, 1911, the water in the Dewar flask inside of the constant-tempera-
ture oven was not stirred by compressed
air. While this change in the apparatus
tended to insure a constancy of temperature
that added somewhat to the accuracy of
the subsequent results, nevertheless the
experiments were usually of short duration,
and hence were not subject to wide errors
due to imperfect stirring.

Previous to an experiment, the ther-
mometers were adjusted and the subject
immediately lay down on a comfortable
couch or occasionally sat in a chair, chang-
ing the position from time to time to avoid

extreme discomfort. In each experiment one main question was usually
studied, and incidentally numerous minor points. In giving the results,
therefore, it seems best to present the curves for each experiment by itself,
with the conclusions drawn therefrom, and finally to summarize the results and
give the conclusions drawn from the experiments as a whole. In these curves,
as usual, the time is expressed by distance measured horizontally and temper-
ature is represented vertically. The records for the various localities are
designated as follows: Deep rectum, RD; shallow rectum, Rs; deep vagina,
VD; shallow vagina, Vs; right axilla, AR; left axilla, AL; mouth, M; groin, G;
upper leg, L; hand, Hc and HP; and various surface points, S.

Table 6. — A

je, height, and
subjects.

weight of

Subject.

Age.

Height.

Weight
without
clothing.

Mrs. B— 1..

years.
43

cm.
164

kilo.
56

F. G. B....

40

183

83

J. J. a...

27

175

65

C. H. H...

18

169

55

V. G

17

162

55

F. A. R....

34

163

74

EXPERIMENTAL RESULTS.

Experiment of January 6, 1911, with C. H. H. — A thermometer was placed
in each axilla, and two thermometers in the rectum, one of the latter being
inserted 10.4 centimeters, and the other 6 centimeters. The experiment
began shortly after the subject reached the laboratory in the morning, and it
will be noticed that in consequence there was an initial fall in temperature of
both the rectal thermometers. This is usual after muscular exercise, even so

46

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

limited an amount of exercise as would be incidental to coming to the labora-
tory. The length of time required to raise the temperature in the axilla to
constancy was from 20 to 30 minutes; when constancy had been assured, the
axillas were opened and cooled for a short time, and the thermometers again
inserted.

The two axillas had about the same temperature curve, and in a general way
the fluctuations followed those in the rectum; the records of the axilla ther-
mometers were, however, lower than those of either the shallow or the deep
rectal thermometer.

The results of the measurements are shown in fig. 15, in which the curves
are marked as previously indicated.

37.2°C

37 0

36.8

36.6

36.4

36.2

36.0

3S.8

356

8.30A.M. 8.50 9.10 930 9.50 10.10 10.30 10.50

Fig. 15. Temperature curves for experiment of January 6, 1911, with C. H. H.

Experiment of January 6, 1911, with Mrs. B — I. — This experiment was made
primarily to test the feasibility of obtaining the body-temperature of women.
The subject came to the laboratory after the noon meal and immediately lay
down upon the couch. A single thermometer was inserted in the rectum to
a depth of 7 centimeters and a second thermometer in the vagina. A ther-
mometer was also placed in the right axilla, the subject lying on the same side
to keep the cavity closed. No special bandages were used. In addition, a
fourth thermometer was placed under the breast, with the breast folded over
it as much as possible and kept in place by a bandage. At 4h 23m p. m., the
thermometer was removed from under the breast and placed in the groin; the
axilla was also opened at this time, and the thermometer replaced in the cavity
at 4h 34m p. m. The curves for the rectum and the vagina had agreed remark-
ably well until this time, but during the change the vaginal thermometer was
accidentally moved out of position and the temperature record changed to a
level a little over 0.5° C. below the original. After the vaginal thermometer

DISCUSSION OF RESULTS.

47

had slipped out, it was unquestionably more or less covered by the labia and
the fleshy portion of the leg, so that the temperature was not extremely low.
The subject lay in a somewhat curled-up position after the placing of the ther-
mometer in the groin, which helped to keep the record of the vaginal ther-
mometer high in spite of the fact that it was not deeply inserted.

An unusually long time was required for the thermometers in the artificial
cavities to reach constancy, this being unquestionably due to the imperfect
closing of the cavities. The curves for these localities follow each other quite
closely, but illustrate admirably the difficulty of securing proper temperature
records without special precautions for perfect closure.

37.4"C

37 2

37.0

36.8

36.6

36.4

36.2

36.0

35.0

35.6

35.4-

2.20 PM. 2.40 3.00 3.20 3.40 4-.00 4.20 4.40 5.00 5.20

Fig. 16. Temperature eurves for experimeni of January 6, 1911, with Mrs. B— 1.

The results of the temperature measurements are given in fig. 16. The
curves for the rectal and axilla thermometers are marked in the usual way,
while the curve for the vagina is designated as V, that for the thermometer
placed under the breast as S, and for the thermometer in the groin as G.

Experimentof January 7, 1911, wift J. J. C— Both, the deep and the shallow
thermometers were used in the rectum, inserted to a depth of 10 centimeters
and 5 centimeters respectively. Temperature records were also taken simul-
taneously in both axillas, the arms being folded across the chest and held in
place by cloth bandages so as to insure perfect closure. The subject sat in a
chair during the experiment and was very sleepy. At 12h 09m p. m., both
axilla thermometers were removed so as to give more freedom of movement.
Between 12h 16m p. m. and 12h 36m p. m. the subject ate a dinner consisting

48

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

of steak, rolls, and coffee. At 12h 57m p. m. he changed to a more comfortable
lounging chair and the axilla thermometers were replaced. At lh 35m p. m.
he put his feet up on another chair.

The occasional fluctuations noted in the curve for the shallow rectal ther-
mometer were probably due to the fact that the thermometer was not inserted
to a sufficient depth, as the observer noted that the temperature fluctuated

„o

<o

«t

<\i

o

oo

iT>

4

N

N

s

N

VO

to

vO

f>

m

n

ro

m

n

CO

CO
CO

10

S"/

"7

DISCUSSION OF RESULTS.

49

whenever the subject moved his legs. Of particular interest, however, is the
fact that while the curve for the shallow rectal thermometer is much lower
than that for the deeper thermometer, the two curves follow each other very
closely, thus indicating simultaneously the temperature gradient previously
discussed, and also a constancy in the curve of body-temperature at different
parts of the body. The temperature curves for the axillas show, first, the
long time required to warm the axilla to constancy, and second, the fact that
unless special precautions are taken to hold the thermometers in place and
fully covered with flesh, the results will have but little value. There is a
marked lack of uniformity between the temperature curves for the axillas
and that for the rectal thermometer. This can be explained only by the fact
that the subject was very sleepy and proper precautions were not taken to

374C

37 2

37.0

36.8

36.6

36.4-

36.2

36.0

35.8

35.6

•\

^•«

* V

+

. «

-i •

V
t « ft

■ • •

R

e

V

W— 1
R

■'■ ' •

A.R..

..-"'

1

A^_

R

p_» '

» V

•
•
•

/,'

SC"

• • •

/ /

2.20 PM. 2.40 3.00 3.20 3.4-0 4.00 4.20 4.40 5.00 5.20

7. i 1 5 . Temperature curves for experiment of January 9, 1911, with Mrs. B— 1.

insure a thorough closure of both axillas, although it is a significant fact that
both the axilla temperature curves show a tendency to fall off at about the
same degree of rapidity.

The results of the temperature measurements are given in fig. 17, the curves
being designated in the usual manner.

Experiment of January 9, 1911, with Mrs. B — I. — A single thermometer was
used in the rectum and another in the vagina, each being inserted to a depth
of 7 centimeters. A thermometer was also used in each of the axillas and one
between the breasts, which were drawn together and folded over the ther-
mometer by means of a cloth belt. The thermometers in the artificial cavities
required a long time to reach constancy, doubtless on account of the imperfect
closure of the cavities. At 3h 30m p. m. both the thermometer in the right

50

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

axilla and the skin thermometer were removed; also, the rectal thermometer
and the vaginal thermometer were each supposedly withdrawn 2 centimeters.
At this time, however, the vaginal thermometer slipped out, causing a discrep-
ancy in the records. At 4h 09m p. m. both the rectal thermometer and the
vaginal thermometer were returned to their original positions, without disturb-
ing the left axilla, and from this time on the curves agree very satisfactorily.

The results of the temperature measurements are given in fig. 18, the curves
being marked as usual.

Experiment of January 11, 1911, with J. J. C. — This experiment was divided
into three parts in order to study the rectal gradient, the effect of warming the
axilla previous to inserting the thermometer also being studied. Two ther-
mometers were used in the rectum, and one in each axilla. In the first part of
the experiment, the deep thermometer was inserted in the rectum to the depth
of 7 centimeters, and the shallow thermometer to the depth of 4 centimeters; in
the second part, the insertions were 5.5 centimeters and 2.5 centimeters respec-
tively; and in the last part, 3.75 centimeters and 0.75 centimeter.

37.2°C

370

36.8

36.6

36A

36.2

2.20 PM. 2.40

300

3.20

3.40

4.00

4.20

4.40

5.00

Fig. 19. Temperature curves for experiment of January 11, 1911, with J. J. C.

Previous to the first part of the experiment, a hot-water bottle, at a tempera-
ture of 40° C, was placed in the left axilla for 5 minutes, the thermometer
being inserted in the right axilla, as usual without preheating. The effect of
this preheating is shown by the fact that the curve for the left axilla rose more
abruptly than that for the right. In the second part of the experiment, the
conditions were reversed, a hot-water bottle with a temperature of 45° C.
being used in the right axilla, but none in the left. Without doubt the tempera-
ture of the water used was too high, as the curve for the right axilla did not
fall to the temperature level of the body for some time. In the third part of
the experiment, the conditions of the first part were duplicated, the hot-
water bottle at a temperature of 40° C. being placed in the left axilla, and the
thermometer inserted in the right axilla without preheating the cavity. The
same tendency to an abrupt rise in the curve for the left axilla was again noted,
although it was not so pronounced as in the first part of the experiment. The
curves for the rectal thermometers show the usual fall in temperature at the
beginning of the experiment. It should be noted that the curves for the deep

DISCUSSION OF RESULTS.

51

and shallow rectal temperatures, by being roughly parallel but not coincident,
indicate clearly the thermal gradient already discussed in considerable detail.1
In view of this fact and that previous experiments indicate a similar gradient,
a fall in temperature would be expected to follow the withdrawal of the ther-
mometers to a less depth. This fall in temperature is not, however, shown.
The discrepancy can be explained only by the fact that as the thermometers
were adjusted by the subject, which involved considerable movement on his
part, the statement regarding the depths of insertion is doubtless inaccurate.

The measurements of the body-temperature in the different localities are
given in fig. 19, the curves being designated as usual.

Experiment of January 12, 1911, with C. H. H. — The deep and shallow
rectal thermometers were used, also a thermometer in each axilla, the axillary
thermometers being held in place by bandages. This experiment, like the
preceding, was divided into three parts so that a study could be made of the
rectal gradient and of the effect of preheating the axilla. In the first part of
the experiment, the depth of insertion of the shallow thermometer was 6.5
centimeters, and of the deeper thermometer, 9.5 centimeters; in the second
part, they were inserted 4 and 7 centimeters, respectively; and in the third
part, 0.75 centimeter and 3.75 centimeters, respectively. A ho-twater bottle,
at a temperature of 40° C, was placed in the left axilla 5 minutes before the
experiment commenced, the right axilla not being preheated. In the second
part of the experiment, the left axilla was again preheated by means of a hot-
water bottle at the same temperature as before, while in the last part the
hot-water bottle, at a temperature of 42.5° C, was used in the right axilla.

During the experiment, the subject apparently slept at times, but usually
was lying awake and quiet. In the first part of the experiment, the left axilla
had a -temperature somewhat above that of the right, although the records for
the two thermometers remained parallel after constancy had been obtained.

370"C

36.8

36.6

36.4-

362

36.0

8.30A.M. 8.50 9.10 9.30 9 50 10.10 10.30 10.50 11.10 11.30 11.50 12.10 P.M. 12.30

Fig. 20. Temperature curves for experiment of January 12, 1911, with C. H. H.

At the beginning of the second part, the temperature curve for the left axilla
was above normal, but fell rapidly until the two axillary curves became essen-
tially the same. In the third part of the experiment, the preheating of the

'See p. 35.

52

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

right axilla raised the temperature above normal and consequently this curve
shows an initial fall, while the curve for the left axilla rose as usual, becoming
constant in approximately 20 minutes.

It is noted that here, as in the preceding experiment, the rectal temperature
curves are apparently unaffected by a change in the depth of insertion. The
explanation is probably the same as before, namely, that the depth of insertion
was changed by the subject himself, and therefore the depths as stated may be
very seriously questioned. The fluctuations in both the rectal curves follow
each other with considerable regularity, the curves being in general parallel.

The measurements of the body-temperature are given in fig. 20, the designa-
tions of the curves being as usual.

Experiment of January 12, 1911, with F. A. R. — In this experiment a single
thermometer was used in the rectum at a depth of 10.5 centimeters; also,
two thermometers were placed between the hands, one in the center of
the palms, the other near the base
of the second finger. To provide for 38°°c
the closure for the two latter ther-
mometers, the hands were firmly
clasped and tied together with
bandages. The curves for the
hands show at first the slowness of
the cavity in approaching its final
temperature; then, beginning about
2h 30m p. m., there was a decided fall
in temperature, undoubtedly caused
by the unconscious partial opening
of the hands. The strain upon the
wrists was relieved at 2h 46m p. m.
by fastening a cotton strap about
the arms above the elbows to prevent
the hands from opening; after this
the cavity gradually increased in
temperature, the curves following
essentially the same course. It re-
quired a long time for the cavity
to attain body-temperature, and as
the subject appeared to be uncom-
fortable, the experiment was discon-
tinued before any opportunity was
afforded to observe the parallelism
of the three curves.

The measurements of the body-temperature are given in fig. 21, the designa-
tion for the rectal curve being the same as usual, those for the hands being Hc
and HF for the thermometers in the center of the palms and at the base of the
second finger, respectively.

\r

Hi

jt:

HAC*

A A

A n

A

A*

J

A

A

A.

a'

AA

'a

4

.

37.8

37 6

37.4

37.2

37.0

36.8

36.6

36.4

36.2

36.0

35.8

1.40 P.M. 2.00 2.20 240 3.00 3.20 3.4-0

Fig. 21. Temperature curves for experiment of January
12, 1911, with F. A. R.

DISCUSSION OF RESULTS.

53

Experiment of January 13, 1911, with V. G, — In this experiment, a ther-
mometer was used in the rectum at a depth of 9.5 centimeters; also, as in the
previous experiment, a thermometer was placed in the center of the palms and
another at the base of the second finger, with the hands clasped and tied with
bandages. The space between the hands was warmed for 5 minutes before
the experiment by a hot- water bottle at a temperature of 40° C.

During the experiment the subject occasionally fell asleep, but sat quietly
the remainder of the time. The two thermometers in the hand gave readings
which agree very well with each other, and while the parallelism with the
records of the rectal thermometer is not perfect, there was a tendency for the
temperature of the hand to fall as the temperature in the rectum fell. The
slight rise between 3h 19m p. m. and 3h 41m p. m. indicated by the curve for
the rectal thermometer is also seen in the curves for the thermometers in the
hand.

The measurements for this experiment may be found represented in fig. 22,
with the designations of the curves as for previous experiments.

37.4 C

37.2

37.0

36.8

36.6

36.4

V

R

r*"^

*-♦

t

A

* t

—A

A
A A

i He,

A A "

i*

. A

A A

-zr

2 * o

i HF

2

A**

*A*
A

A A *

""1

'**:

i A
i A

1.40 P.M. 2.00 2.20 2.40 3.00 3.20 3.40 4.00 4.20 4.40

Fig. 22. Temperature curves for experiment of January 13, 1911, with V. G.

Experiment of January 14, 1911, with C. H. H.—In this experiment the
subject sat in the chair, and both the deep and the shallow rectal thermometers
were used, the former inserted to the depth of 9.5 centimeters, and the latter
6 centimeters. The temperature of the hands was taken by two thermome-
ters as in previous experiments, the hands being clasped and bandaged as
usual. Still another thermometer was placed between the crossed legs above
the knees. No hot-water bottle was used.

The initial fall in the rectal temperature, noted in practically all of the
experiments, is here very well marked. The curves representing the tempera-
ture in the hands remained fairly parallel throughout, but did not follow the
curve of the rectal thermometer. On the other hand, the temperature of
the upper leg, while requiring a very long time to reach equilibrium, followed
the rectal temperature with remarkable constancy and accuracy when it had
finally reached the upper level. An effort was made in other experiments to
measure the body-temperature between the crossed legs, but these attempts

54

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

were unsuccessful, and the locality does not appear favorable for such observa-
tions, as its use involves much discomfort to the subject.

The records obtained in this experiment are given in fig. 23, the curves being
designated as usual, that for the artificial cavity between the crossed legs
being marked L.

37.4°C

37 2

370

368

366

364

36.2

36.0

35.8

V

\

CD

*N,

f*"*^

■*■ a i

® ®

He

A'i*

®

3

"^V
9 ^

®i

^®

> ®

® *

HF £
®

»A*A

4*.

A

A <

®

A*i

{*i*

a

A - A

i*A

h 4 A >

®

" a °

ft A 4 ■"

®

110 PM. 130 1.50 210 2 30 2.50 310 3 30 3.50 410 4 30

Fig. 23. Temperature curves for experiment of January 14, 1911, with C. H. H.

Experiment of January 16, 1911, with Mrs. B — I. — The deep and shallow
thermometers were used in the rectum, inserted 7.5 centimeters and 4 centi-
meters respectively, and a single thermometer in the vagina at a depth of

37,6 C

37.4

37.2

37.0

36.8

36.6

36 4 _

230PM a50 3.10 3.30 3.50 4.10 4.30 4.50 5.10

Fig. 24. Temperature curves for experiment of January 16, 1911, with Mrs. B — 1.

10 centimeters. A thermometer was also placed in the left groin. At the
beginning of the experiment a thermometer was strapped between the arm
and the breast, but the temperature for this locality was very slow in reaching

DISCUSSION OF RESULTS.

55

constancy and the thermometer was later removed, and two thermometers
were placed side by side in the left groin.

The usual initial fall in temperature on lying down on the couch is well
shown in the curves for the deep and shallow rectal thermometers and for the
vaginal thermometer. The temperatures for these three localities followed
one another with fair constancy throughout the whole test. The groin tem-
perature required considerable time to reach constancy, but thereafter followed
the fluctuations in the temperature of the rectum and the vagina with reason-
able regularity. As will be seen by the curves, the thermometers used in the
latter part of the experiment for obtaining the temperature of the groin agreed
fairly well with each other, and also followed closely those of the rectum and the
vagina. While the temperature indicated by the shallow rectal curve is
considerably lower than that of the deep rectal curve, it is interesting to note
that the parallelism of the two records is very marked.

The records for this experiment are given in fig. 24 ; the curves are designated
in the usual manner, the curve for the thermometer between the arm and the
breast being marked S, and those for the groin, Gi and G2.

Experiment of January 17, 1911, with Mrs. B — I. — In view of the parallelism
shown in the previous experiment between the groin temperature and the
temperatures of the rectum and the vagina, this experiment was designed to

378 C

37.6

374-

37 2

37 0

5.20

2.20 PM. 2.40 3.00 3.20 3A0 4-00 4.20 440 5.00

Fig. 25. Temperature curves for experiment of January 17, 1911, with Mrs. B— 1.

make a comparative study of the temperatures of the groin, the deep and the
shallow vagina, and the rectum, a thermometer being placed in all of these
localities. In the rectum, the thermometer was inserted to a depth of 7
centimeters, while in the vagina, one thermometer was inserted to the depth
of 10 centimeters, and the other to the depth of 6.5 centimeters. Before
the experiment began, a hot-water bottle at a temperature of 42° to 43° C.
was placed in the groin for 5 minutes. From the curves, it may be seen that
the groin temperature was at first considerably higher than normal, then
fell off until it reached a constant level somewhat below that of the vagina and
the rectum, and thereafter followed in a general way the fluctuations of the
other thermometers.

The records of the experiment may be found in fig. 25, with the curves
designated as usual.

56

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

Experiment of January 20, 1911, with C. H. H. — In this experiment the
subject crossed his arms on his chest, and one thermometer was placed between
the lower arm and the chest, and another at the point where the arms crossed.
In addition, two thermometers were used in the rectum, and one in each of
the axillas, 6 thermometers in all being used. The thermal junctions were
kept in position in the usual way by bandages. The locations between the
crossed arms, and between the arm and the chest are particularly unfavorable
for accurate records of body-temperature, as it is difficult to secure a perfect

closure. The curves, however, seem

37.0 C

36.8

36.6

36.4-

36.2

36.0

35.8

35.6

354

2.00 PM

4.00

to follow one another very fairly,
this doubtless being due to the care
exercised by the subject not to dis-
place the thermometers. No hot-
water bottles were used for preheat-
ing any of the cavities, and conse-
quently the length of time required
for the different parts to reach equi-
librium is very well shown by the
rise in the temperature curve at the
beginning of the experiment. The
usual initial fall of the deep and the
shallow rectal temperatures is shown
in this experiment. Between 3h 17m
p. m. and 3h 22m p. m., the legs were
uncovered in an attempt to produce
a lowering of the temperature by
exposing the skin surface, but this
was without appreciable effect.
The records of the measurements
are given in fig. 26, the curves being marked as usual. The curve for the
thermometer between the arm and the chest is designated by Si and the curve
for the thermometer at the point where the arms crossed by S2.

Experiment of January 23, 1911, with C. H. H. — In this experiment the
deep and shallow rectal thermometers were used to give a base line for com-
parison with the records of thermometers inserted in the right and the left
axillas between the crossed arms, as in the previous experiment, and in the
mouth. The thermometers in the rectum were inserted 12 centimeters and
8.5 centimeters respectively. The subject lay on a couch on his right side,
the thermometers in the axillas being held in position by bandages as usual.
At 10h08m a.m., the subject became uncomfortable, and lay on his back
instead of on his right side. Between 10h22m a.m. and 10h27m a.m., the legs
were uncovered to find if exposure would lower the temperature. As a matter
of fact, the curves indicate a slight rise in temperature instead of a fall. The
temperature in the left axilla quite closely parallels that in both the rectum
and the mouth. The abnormal course of the temperature in the right axilla

Fig. 26. Temperature curves for experiment of Jan. 20, 1911,
withC. H. H.; 3.17 p.m. to 3.22p.m., body surface exposed.

DISCUSSION OF RESULTS.

57

and between the arms can be readily explained by the difficulty in securing a
proper position on account of the discomfort of the subject. It is of interest
to note that from 10h 20m a.m. to 11 a.m., the temperature between the arms
(curve M) followed almost exactly that of the rectum.

The records of the measurement may be found in fig. 27, the designations of
the rectal and axillary curves being as usual. The curves for the thermometers
between the crossed arms and in the mouth are marked S and M, respectively.

37 2°C

37 0

368

36.6

36.4

36.2

36.0

358

35.6

354

8.50 AM. 9.10

9.30

9.50

10.10

10.30 10.50 11.10

Fig. 27. Temperature curves for experiment of January 23, 1911, with C. H. H.;
10.22 a. m. to 10.27 a. m., body surface exposed.

Experiment of January 24, 1911, with J. J. C. — The conditions of this experi-
ment were essentially the same as in the experiment of January 23, save that
a different subject was chosen and the thermometer between the arms was
omitted. Two thermometers in the rectum were used at a depth of 8 centi-
meters and 4.5 centimeters, respectively, one in each of the axillas, and one in
the mouth. The subject slept much of the time during the experiment, and
there was consequently so much trouble in securing a proper closure of the
mouth that at 9h31m a. m. the mouth thermometer was removed and replaced
at 9h44m a.m. surgeon's plaster being used to hold the lips together. At
9h46m a.m., the subject changed his position and lay more on his side. Be-
tween 10h59m a. m. and llh03m a.m., he drank 2\ cupfuls of hot coffee, the
thermometers in the mouth and the axillas being removed for this purpose.
The subject then turned on his side and the thermometer was replaced in the
left axilla. The thermometer in the mouth was likewise replaced, surgeon's
plaster being again applied. Near the end of the experiment, there were
indications that the shallow rectal thermometer was closer to the anus than
was reported by the subject; the wide discrepancies between the records of

58

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

the two rectal thermometers from llh10m a.m. to llh59m a.m. can hardly be
explained in any other way. Similarly, at the beginning of the experiment a
temperature difference of approximately 0.6° C. between the two rectal records
appears to be due to the fact that the shallow rectal thermometer was not
inserted to so great a depth as was supposed.

The measurements of the temperature are shown in fig. 28, the curves being
marked as in previous experiments.

372 C

37 0

36.8

36.6

36.4

36 2

36.0

35.8

35.6

8.30 A.M. 8.50 9 10 9.30 950 10.10 10 30 10 50 II 10 II 30 H 50 12.10 PM.

Fig. 28. Temperature curves for experiment of January 24, 1911, with J. J. C; 10.59 a.m. to 11.03 a.m.

drinking hot coffee.

Experiment of January 27, 1911, with Mrs. B — I. — In this and all succeed-
ing experiments, compressed air was used to stir the water in the Dewar flask
in the constant-temperature oven.

Two thermometers were used in the vagina, at a depth of 10 and 6.5 centi-
meters, respectively, and a thermometer in the rectum at a depth of 6 centi-
meters. In addition, a thermometer was placed in the groin and one in the
right axilla, and intermittent observations were made in the mouth.

The curves for this experiment are interesting in that they show a period
of 3 hours in which the temperature in the vagina and the rectum did not
change more than approximately 0.1° C. The deep and shallow thermometers
in the vagina remained within 0.07° C. of each other throughout the whole test,
the records with the deep vagina thermometer being somewhat higher than
those with the shallow thermometer. The rectal temperature was slightly
higher than the vaginal temperature, the maximum deviation from the tem-
perature of the deep vagina being 0.07° C. It was observed that during this
experiment the rectal thermometer was embedded in feces. The thermometer
in the groin required about 20 minutes to reach constancy. The curves for
both the axilla and the groin temperatures follow in a general way the parallel
temperatures of the deeper thermometers, although the temperature fluctua-

DISCUSSION OF RESULTS.

59

tions throughout the whole test were not sufficiently striking to make these
records of very great value in this connection. The records of the mouth
temperature are chiefly of interest as indicating the time required to warm the
cavity to approximate constancy. With the mouth closed about 10 minutes
prior to taking the temperature (see the curve at about 4h29m p.m.), constancy
was reached in about 8 minutes. With the mouth open for 10 minutes pre-
vious to taking the temperature, a period of over 15 minutes was required
(see the curve at about 5 p.m.).

The records of body-temperature may be found in fig. 29, the curves being
designated as usual.

364

2.30 P.M. 2.50

3.10

3.30

3.50 410

4.30 4.50

5.10

5.30 5.50

Fig. 29. Temperature curves for experiment of January 27, 1911, with Mrs. B — 1.

Experiment of January 31, 1911, with Mrs. B — I. — In this experiment the
temperature was taken in the vagina with the deep and the shallow ther-
mometers; in the rectum with a single thermometer, also in the groin, and in
either the right or the left axilla, no hot-water bottle being used for preheat-
ing the artificial cavities. An attempt was also made to secure the temperature
of the mouth from time to time throughout the day, the subject being asked
not to breathe through the mouth previous to the observations.

At the beginning of the experiment, the thermometer in the right axilla
was not in proper position, and it was accordingly readjusted at 9h58m a. m.
When this temperature had attained the maximum, however, it remained
fairly constant. At llh 58m a.m. the subject changed from the couch to a
chair, and sat quietly reading, except between lh 04m p.m. and lh 29m p.m.,
when she ate a dinner consisting of steak, coffee, and potato chips. At 3h 25m
p.m. she lay down again on the couch and remained either sleeping or lying
quietly awake for the rest of the experiment. During the time she sat in the
chair, the thermometer was placed in the left axilla, and that in the groin
removed. When she again lay down on the couch, however, the thermometers
were returned to their original positions.

The curves for the deep and the shallow vaginal temperatures and for the
rectal temperature follow one another throughout the day with remarkable
regularity for the most part. The groin temperature required a long time to
reach the maximum, but thereafter the records followed those for the rectum

60 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

and the vagina. On changing the thermometer to the left axilla, considerable
time was required for the temperature to reach the maximum, and this was
also the case when the right axilla was again used after the subject lay down
on the couch in the afternoon. The records of mouth temperature are of
value only for showing the length of time required to reach the maximum;
the highest point in the curve should be taken to indicate the actual temper-
ature of the mouth, an imaginary curve joining these high points conforming
to the general shape of the curves for the deep thermometers. The tendency
for the curves to rise throughout the day, even when the subject lay on the
couch, is characteristic of the diurnal variation in which the highest temper-
ature is in the late afternoon.

The curves showing the body-temperature for the different localities may be
found in fig. 30.

Experiment of February 3, 1911, with Mrs. B — /. — The deep and shallow
vaginal thermometers were used in this experiment, inserted to a depth of 10
and G.5 centimeters, respectively, also a single rectal thermometer at a depth
of 8 centimeters. Thermometers were placed in the groin, in either the right
or left axilla, and temperatures were taken intermittently in the mouth
throughout the experiment. A hot-water bottle at a temperature of 44° C.
was used in the axilla, and another with a temperature of 49° C. in the groin
for about 5 minutes before the experiment, but this preheating was not so
effective as usual in shortening the time required to secure constancy.

During the first part of the experiment the subject lay on the couch quietly
reading. At 9h 19in a. m. the axilla thermometer was placed in a better posi-
tion, and later (at llh 24m a. m.), as the subject had been moving about con-
siderablj7, it was again readjusted. At 12h 14m p. m., the subject changed from
the couch to the chair; at the same time the thermometer was changed from
the right axilla to the left axilla, which had been previously heated by means of
a hot-water bottle at a temperature of 46.5° C. The temperature of the left
axilla fell for the first few minutes, indicating that the preheating had raised
the temperature of the cavity somewhat above the normal. From lh 01m p. m.
to lh 25m p. m. the subject was eating dinner. At 2h 30m p. m. she lay down
on the couch again, a hot-water bottle at a temperature of 47° C. being placed
in the groin, and another at the same temperature in the axilla. In both
instances the temperature rose considerably, but apparently the maximum tem-
perature was reached in a much shorter time than in the earlier portion of the
test. At 3h 01m p. m., the lips were fastened together with surgeon's plaster
in order to keep the mouth thermometer in place for continuous observation.
The subject was asleep and moved about somewhat. At 4h 24m p. m. she was
asked to keep the mouth tightly closed. Finally the thermometer was removed
from the mouth at 4h 56m p. m. and reinserted without the use of plaster at
5h 19™ p. m. A higher temperature was then observed in this locality, which
may have been due to a better closure of the mouth after the rest in the interval
when the thermometer was not in position.

The peculiar feature of the curves in this experiment is the general uniformity
of the records for the deep and the shallow vaginal thermometers and the rectal

DISCUSSION OF R.KSI LTS.

Gl

62 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

thermometer, with the single exception of the record for the shallow vaginal
thermometer between 2 p. m. and 2h 30m p. in. It would appear as if the
thermometers in the vagina had been displaced during this interval, and that
the shallow thermometer had slipped out of the cavity. The groin tempera-
ture followed with considerable regularity the temperature indicated by the
other thermometers, while the inequalities of the axillary temperature in the
early part of the experiment may be accounted for by the restless movements
of the subject. The great irregularities in the temperature of the mouth
accentuate the undesirability of this locality for such observations.

The curves showing the records of bod3r-temperature may be found in fig. 31.

Experiment of February 6-7, 1911, with Mrs. B — I. — This experiment was
planned to continue for 24 hours, in order to secure the total diurnal variation.
The subject was lying on a couch during the whole experiment except when
sitting in a chair between llh 59m a. m. and 2h 10m p. m., and 5h 24m p. m.
and 1 1 h 19m p. m. A single thermometer was inserted in the rectum at a depth
of 8 centimeters, and both deep and shallow thermometers in the vagina at a
depth of 10 centimeters and 6.5 centimeters respectively. While the sub-
ject lay on the couch, temperature observations were made in the right axilla
and in the groin. During the time the subject sat in the chair, the groin obser-
vations were discontinued, and the axillary temperature was taken in the left
axilla instead of the right. Observations of the mouth temperature were made
intermittently.

At the beginning of the experiment the groin and axilla were warmed by
means of hot-water bottles at a temperature of 45° C. The temperature of
the groin reached the maximum very shortly, but the temperature of the axilla
required a long time to acquire constancy. An abnormal and wholly inexplica-
ble rise in axillary temperature was noted, beginning at 10h 39m a. m. When
the subject changed from the couch to the chair at llh 59m a. m.,the groin tem-
perature records were discontinued and the temperature was taken in the left
axilla instead of the right, so that the subject could use the right hand in eating.
Before inserting the thermometer, the left axilla was heated with a hot-water
bottle, at a temperature of 47° C, but gave very unsatisfactory results at first.
The subject was asked to readjust the thermometer at 12h 59m p. m., and the
results thereafter were much more uniform. Between lh 07m p. m. and lh 32m
p. m. she ate her dinner, and at 2h 12m p. m., she returned to the couch. The
groin and axilla were heated with hot-water bottles at a temperature of 47° C.
before the thermometers were inserted, and the temperature of the groin rose
considerably above even that of the rectum, cooling again rapidly to a constant
temperature. The axillary temperature also quickly attained constancy. The
subject was asleep between 3h 17m p. m. and 4h 07m p. m., and on waking up
asked for water, drinking a half glassful at 4h 12m p. m. While it may have
been a mere coincidence, all of the curves show a slight tendency to a lowering
of the temperature after the drinking of the cold water. At 5h 24m p. m. the
subject again changed from the couch to the chair, and the axillary temperature
was taken in the left axilla, while the groin records were discontinued. During

DISCUSSION OK RESULTS.

63

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64 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

this period, the subject ate her supper. While she sat in the chair, the records
were so irregular that they are not given. It is possible that the thermometers
were not well located, as it was noted that a difference in temperature was
caused by the subject sitting forward or back in the chair. At llh 19m p. m.
the subject changed from the chair to the bed, and beginning at llh 45m p. m.
the temperature curves are again given. The groin and right axilla were heated
by means of a hot-water bottle at a temperature of 47° C. The groin tem-
perature was noticeably affected by the preheating and rapidly attained con-
stancy, but the temperature in the right axilla required the usual 20 minutes
to reach a constant level. The subject lay very quietly the first of the night,
and the temperature curves fell off in accordance with the general diurnal varia-
tion. From lh 30m a. m. to 2 a. m. she moved about considerably, and also
between 3 a. m. and 3h 27m a. m. At 3h 27m a. m. the subject was told that
she need not keep the groin closed, and this temperature record was discon-
tinued until 4h 12rn a. m. She reported that she had slept at times. The
subject moved more or less until about 5 o'clock, but she was very quiet from
5 a. m. until 5h 30m a. m. Later she moved somewhat and at 6h 46m a. m.
asked several questions. The groin and axilla thermometers were removed at
7h 14m a. m., and the deep and the shallow vaginal thermometers at 7h 52m
a. m. At 8 a. m. the thermometer was replaced in the groin, the groin and
rectal temperatures being recorded continuously thereafter. The subject ate
breakfast between 8h15m a. m. and8h39m a. m., and from that time until the end
of the experiment, at 9h 27m a. m., she was awake, talking and reading.

While the groin required considerable time to reach a constant temperature,
except when preheated, when the body-temperature had finally been acquired
the records followed with remarkable regularity those for the rectum and the
vagina. The temperature of the axilla varied considerably and does not show
the parallelism which would be expected, this parallelism evidently depending
upon the accuracy and constancy with which the axilla is closed, thus accentu-
ating very sharply the fact that the groin is on the whole a much better locality
than the axilla for taking body-temperatures. The temperature observations
made in the mouth show their usual irregularity, although a curve drawn
through the maximal readings would follow the curves for the rectum and the
vagina.

The curves showing the records of body-temperature may be found in fig. 32.

Experiment of February 27, 1911, with J. J. C. — In this experiment the deep
and shallow thermometers were used in the rectum at depths of 9.5 and 6
centimeters respectively, and a thermometer in the left axilla. A ther-
mometer was also inserted in the mouth and held there continuously.

During the experiment the subject sat in a chair, sometimes awake and
reading and sometimes apparently asleep. At 9h 23m a. m. he drank some
cold water. He changed his position in the chair at 10h 33m a. m., and the
axilla thermometer was also readjusted at this time. At llh 16m a. m. the
left shoulder became uncovered, and at llh 22m a. m. the subject removed
his feet from the couch on which he had been resting them. From 12h 21 m

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Fig. 32. Temperature curves for experiment
of Februarj 6-7, 1911, with Mrs. B- 1.
1.03 p. in. to 1 i_' p. in., eating; 4.12
p. in., drinking water; 8.15a. m. t 18 39
a. m.. eating.

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66

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

p. m. to 12h 38m p. m. he was eating, the thermometers in the mouth and in
the axilla being removed during this time. Before reinserting the thermometer
in the left axilla, the cavity was heated by a hot-water bottle at a temperature

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of 40° C; this resulted in a rapid rise to constancy. Toward the end of the
experiment the subject became very tired and uncomfortable, and at 2h 14m
p. m. rested his feet on the couch again.

DISCUSSION OF RESULTS.

67

The general tendency toward parallelism of all of these curves is rather
striking; nevertheless, the temperature of the mouth 'exhibits considerable
fluctuation from time to time,
and the temperature of the left
axilla falls off more rapidly be-
tween llh 18m a. m. and llh 48m
a. m. than do cither the deep or
the shallow rectal temperatures,
these differences being more
marked than in most of the ex-
periments. The rapidity with
which the temperature of the
left axilla came to constancy after
the use of the hot-water bottle at
12h 47m p. m. is also noticeable.

The measurements of the body-
temperature are shown in fig. 33.

Experiment of March 1, 1911,
with C. H. H. — The deep and
shallow rectal thermometers were
used in this experiment, with an
insertion of 12 and 8.5 centimeters,
respectively. A thermometer was
also used in the left axilla, and
one in the mouth. This experi-
ment was designed to duplicate
more Or less the experimental con-
ditions of the study made with
J. J. C. on February 27. The
mouth temperature was not taken
continuously, however. A hot-
water bottle at a temperature of
43° C. was used in the left axilla.
The subject was eating between
12h 37m p. m. and lh 04m p. m.;
at lh 05m p. m. he changed the
position of his feet, resting them
on a stool instead of on the couch.

The parallelism of the curves is
very striking in all instances, the
curve for the axilla, although
showing a lower temperature, fol-
lowing the curves for the rectal co
temperature very satisfactorily.

The measurements of the body-temperature may be found in fig. 34.

68

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

Experiment of March 2, 1911, with F. A. R. — The deep and shallow rectal
thermometers were used, with an insertion of 12 centimeters and 8.5 centi-
meters respectively, and two thermometers in the hand, one in the center of
the palms and one at the base of the second finger, the cavity between the
hands having been previously heated with a hot-water bottle at a temperature
of 42° C. Intermittent observations were also made of the mouth tempera-
ture. As in previous experiments, the hands were closety clasped, tied with
cloth bandages, and covered with a pile of loose pieces of cloth. The arms
were bound together above the elbows, as usual, to prevent the spreading
apart of the wrists. At 8h 58m a. m. one of the hand thermal junctions was
inserted a little farther toward the center of the hand. To test the effect of
hot and cold drinks, the subject was given cold water at 9h 48m a. m. and a
cupful of hot coffee at llh 08m a. m.

37.6 C

37.4

37.2

37.0

36.8

36.6

36.4-

36.2

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8.30 A.M. 8.S0

9.10

9.30

9.50

10.10

10.30 10.50

11.10

11.30

11.50 12.10 RM.

Fig. 35. Temperature curves for experiment of March 2, 1911, with F. A. R. 9.48 a. m., drinking

cold water; 11.08 a. m., drinking hot coffee.

In a general way the curve for the thermometer in the middle of the hand
follows the curve for the rectal thermometer, although in the latter part of the
experiment the rise in temperature is not so noticeable as in the curve for the
rectal thermometer. While the temperature curve for the thermometer at
the base of the second finger shows wide variations, nevertheless the general
tendency is not far from that shown in the curve for the thermometer in the
middle of the palms. The temperatures taken in the mouth are very irregular
and it is impossible to draw any deductions from the observations in this cavity.
Just after taking hot coffee, a slight rise may be noted in all of the temperature
curves, but the cold water appeared to have no effect.

The curves showing the measurement of the body-temperature may be
found in fig. 35.

Experiment of March 3, 1911, with F. G. B. — In this experiment, the shallow
and deep rectal thermometers were used, a thermometer in the left axilla,
and one in the mouth. Before inserting the thermometer in the left axilla,

DISCUSSION OF RESULTS.

69

the cavity was heated by means of a hot-water bottle at 42° C. The subject
sat in a chair throughout the experiment. From 2h 55m p. m. until 3h 23™
p.m., he endeavored by muscular activity to stimulate a rise in temperature;
he moved his legs and arms and exercised with a stool, lifting it, holding it at
arm's length, and raising and lowering it above the head. He also placed ;i
book rest on his toes, and moved it up and down. The exercise was sufficient
to cause perspiration and fatigue. After the exercise, he was very quiet,
closed his eyes, and tried to go to sleep. His elbows rested on the arms of the
chair, and his head on his hands. At 3h 41m p. m., as the mouth thermometer
was in position, some directions were written on a piece of paper. At 3h 49m
p. m., 400 cubic centimeters of cold water at a temperature of 4.8° C. were taken.
During the muscular work, the mouth thermometer was used, and held
continuously in place until it was removed when the cold water was taken.
It was then immediately replaced and allowed to come to the maximum
temperature.

376 C

374

37 2

37.0

36 8

36A

36.2

360 L

I.40RM. 2.00

2.20

240

3.00

3.20

3.4-0 4.00

4.20 4.40

Fig 36 Temperature curves for experiment of March 3, 1911, with F. G. B. 2.55 p. m. to 3.23 p. m ,
muscular exercises; 3.49 p. m„ drinking cold water.

Special care was exercised by the subject to keep the mouth closed and to
breathe only through the nose, so as to keep the mouth temperature as nearly
constant as possible. Care was also taken not to disturb the position of the
axillary thermometer. The curves for this experiment show remarkably
well the uniformity between the deep and the shallow rectal temperatures,
the temperature in the left axilla, and that in the mouth. The fluctuations
during the muscular exercise, the succeeding quiet condition, and the taking
of the cold water were almost exactly equal in all the curves and were clearly
defined. As would be expected, the muscular exercise produced a rise in
temperature, while the subsequent quiet condition and the taking of cold
water evidently caused a lowering of the temperature.

The curves showing the body-temperature measurements for the different
localities may be found in fig. 36.

70

TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

Experiment of March 10, 1911, with J. J. C. — The deep and the shallow
rectal thermometers were used at a depth of 15 centimeters and 11.5 centi-
meters, respectively. A thermometer was also placed in the left axilla, this
cavitjr having been previously heated by a hot-water bottle at a temperature
of 42.5° C, and intermittent observations were also taken in the mouth. The
influence of muscular activity was studied in this experiment, and beginning
at 3h 26m p. m. the subject exercised quite vigorously. This activity appeared
to tire him, as he breathed heavily and perspired freely. During the exercise
he was more or less exposed, as he wore a blanket over his shoulders instead
of a sweater. At 3h 49m p. m. he stopped exercising and became quiet. For

37 8°C

37.6

37.4-

37.2

37.0

36.8

36.6

36.4-

36.2

360

3S.8

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t

''ft'

^V

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WTS

v°

2.10 RM. 230 2.50

3.10

3.30

3.50 4.10

4-.30 4-.50

Fig. 37. Temperature curves for experiment of March 10, 1911, with J. J. C. 3.26 p. m. to 3.49 p. m.,

muscular exercise.

some unaccountable reason there was not a very close parallelism between
the two rectal records, although all of the curves show a general tendency
toward parallelism, especially the curves of the rectal and the axillary temper-
atures. The muscular exercise did not produce a rise in the temperature;
while this is not easy to explain, it may have been due to the fact that the
surface of the skin was more exposed during the exercise than when the sub-
ject was quiet, causing a tendency to cool the surface.

The curves showing the measurements of the body-temperature in the
different localities may be found in fig. 37.

Experiment of March 13, 1911, with F. A. R. — In this experiment both deep
and shallow rectal temperatures were taken, also the temperature of the left

discission OF RESULTS.

71

axilla, and occasionally the temperature of the mouth. The two rectal ther-
mometers were inserted at a depth of 10 and G.5 centimeters respectively.
The axilla was preheated by means of a hot-water bottle at a temperature of
42° C, which caused the subject to perspire; during the experiment the bandage
holding the axilla thermometer loosened. In previous experiments it had
been noted that the rectal temperatures usually fell at the beginning of an
experiment, which would indicate that the temperature when the subject was
active before the experiment was higher than after he became quiet. For
this reason it was decided to take the mouth temperature at the very beginning
of the experiment. If the curves indicating the mouth and rectal temperatures

37.6 C

37.A

37 2

37.0

36.8

36.6

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1.30 PM 150

2.10

2.30 2.50

310

3 30

3.50

4.10

4 30 4.50

Fig. 38. Temperature curves for experiment of March 13, 1911, with F. A. R. 3.02 p. m. to about 3.50
p.m., muscular exercise; 3.50p. m., drinking cold water.

are to be parallel, this first observation of the mouth temperature should be
very high, and this was found to be actually the case. At 3h02m p.m., the
subject began to exercise by lifting a stool, and at 3h32m p.m. he was still
exercising but not working very hard. At 3h50mp. m., just after he had
stopped exercising, he drank a glass of cold water at a temperature of 10° C.
A subsequent fall in temperature of almost 0.2° C. was noted, which may have
been due in part to the influence of the cold water. The temperature curves
for this experiment were in general parallel, the curves for the temperatures
of the mouth and the rectum being more nearly parallel than usual.

The curves showing the measurement of the body-temperature in the
different localities may be found in fig. 38.

72 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY.

CONCLUSIONS.

From this series of temperature observations made on a number of different
subjects, certain definite conclusions have been drawn:

1. When two thermc meters are placed in one internal cavity at not less than
6 centimeters deep, the temperature curves are parallel and approximately
equal. This is shown in figs. 15, 20, 23, 25, 27, 29, 30, 31, 32, 33, 34, 35, 36,
and 38, but certain abnormalities not easily explainable are seen in figs. 26
and 37.

2. When two thermometers are placeel in one internal cavity and the dis-
tance between them is 3.5 centimeters, one being within 5 centimeters of the
surface of the body, the curves obtained are parallel, but not equal in value,
thus indicating a temperature gradient. See figs. 17, 19, 24, and 28.

3. Thermometers placed in the rectum and the vagina, at depths of at
least 6 centimeters, show curves that are parallel and approximately equal.
See figs. 16, 18, 24, 25, 29, 30, 31, and 32.

4. Thermometers in the right and left axillas give curves that are parallel,
showing approximately equal temperatures. This is indicated in figs. 15, 17,
and a part of 19, also in 20 and 26. Exceptions to this are shown in figs. 18,
27, and 28, but in considering these exceptions one must not lose sight of the fact
that it is very difficult to secure constant and well-closed axillas undisturbed
by body movements; we have every reason to believe that the conflicting
results in these three curves are due to misplaced thermometers.

5. Two thermometers placed in the groin give results that are parallel and
approximately equal. This is shown in fig. 24.

6. Two thermometers placed in the hand give results that are equal and
parallel. See figs. 21, 22, and 23. In fig. 35, the curves are parallel but not
equal, indicating a slight gradient.

7. The use of the hot-water bottle hastens the warming-up of such artificial
cavities in the body as the axilla, groin, and hand. This fact is shown in figs.
19, 20, and 22, and in parts of 31, 32, and 33, also in 34, 35, 36, 37, and 38.

8. When lying on a couch after the slight muscular work involved in coming
to the laboratory and moving about before the experiment, there is usually an
initial fall of internal temperature. This is clear^ evident in figs. 15, 19, 20,
21, 22, 23, 24, 26, 27, 28, 33, 34, 36, and 37, but not so well shown in figs. 17,
18, 25, 29, 30, and 35, and is entirely absent in figs. 16, 31, 32, and 38.

9. Temperatures taken in the mouth are in general extremely irregular and
unsatisfactory, as may be seen in figs. 28, 29, 30, part of 31, and 32, also in
fig. 35. Nevertheless fair results are shown in figs. 27, 33, and 34, and very
satisfactory results in figs. 36 and 38.

10. The effect of eating a meal tends to increase somewhat the temperature
of the body. See figs. 17, 30, 31, 32, 33, and 34.

11. On exposing portions of the skin under the conditions of the experiments
here made, no effect on bocty-temperature was apparent in figs. 26 and 27.

DISCUSSION OF RESULTS. 73

12. On drinking hot coffee, the body temperature was very slightly in-
creased. This is shown in figs. 28 and 35.

13. Drinking cold water had a tendency to lower the body-temperature.
See figs. 36 and 38. This effect was not evident in the experiment repre-
sented by fig. 35, however.

14. Muscular exercise produced a marked increase in body-temperature
in at least one experiment (see fig. 36), but was without effect in others (see
figs. 37 and 38). Of significance was the fact that while obtaining the' data
for fig. 37, the skin of the subject was more or less exposed to the air.

15. The internal temperature of the body and that of the axilla, breast,
groin, hand, arm, and mouth, have a tendency toward parallelism. This is
evident in practically all of the curves, but is especially well shown for the
internal temperature and the axilla in figs. 20, 27, 33, 34, 36, and 38, although
in fig. 27 this is not true of the right axilla for reasons previously explained.
The parallelism is also shown for the internal temperature and the groin in
figs. 24, 25, and 31; for the internal temperature and the mouth in figs. 27, 33,
34, 36, and 38; and for the internal temperature and the upper leg in fig. 23.

Finally, it can be stated that an examination of all the results obtained
show's in the temperature curves a remarkable trend toward parallelism, a
parallelism that would be exact, there is every reason to believe, if the ther-
mometers could remain in precisely the same position and if the cavities
could remain absolutely constant in their closure. We feel justified, there-
fore, in summing up this work by stating that, aside from the skin temperature,
a rise or fall in rectal temperature is accompanied by a corresponding rise or
fall in temperature of all other parts of the body.

Nutrition Laboratory, Carnegie Institution of Washington,

Boston, Massachusetts, July, 1911.

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