218 
PHYSIOLOGY: BENEDICT, MILES AND JOHNSON 
THE TEMPERATURE OF THE HUMAN SKIN 
By F. G. Benedict, W. R. Miles, and Alice Johnson 
Nutrition Laboratory, Carnegie Institution of Washington, Boston, Massachusetts 
Read before the Academy, April 28, 1919 
The clinical importance of records of body-temperature, as taken usually in 
the mouth and occasionally in the axilla or rectum, has quite obscured the 
physiological significance of the skin temperature. Extensive researches have 
shown that the temperature of the human body, deep in the body trunk or in 
any of the natural cavities, remains reasonably constant, although there is a 
diurnal ryhthm, with a minimum value at about 4 a.m. and a maximum-at about 
5 p.m. Simultaneous observations of temperature at different parts of the 
body show that there is almost always a parallelism in curves for tempera- 
ture. Thus, the temperatures in the rectum or vagina, the well-closed groin 
or axilla, and the mouth, show similarly shaped curves, although at markedly 
different levels. 
The technical difficulties in recording skin temperature have undoubtedly 
retarded extensive study in this phase of body-temperature research. The 
temperature of the human skin is the resultant of several factors, as heat is 
suppfied from the subcutaneous tissues and lost from the surface of the body by 
radiation, conduction, and the vaporization of water. An attempt to secure 
accurate records of skin temperature by the application of an ordinary mercury 
thermometer is obviously useless, for but a small proportion of the bulb of such 
a thermometer comes in actual contact with the skin. Even thermometers 
constructed with a special bulb providing a large surface to apply to the skin 
have a like surface exposed to the environmental temperature. If, as is oc- 
casionally done, this outer surface is covered with non-conductive material, 
there is almost immediately a disturbance in the temperature of the skin due 
to the fact that there is a retardation of the normal loss of heat, with a conse- 
quent accumulation of heat from the subcutaneous tissue. The true tempera- 
ture of the skin should therefore be recorded by an apparatus which is nearly 
instantaneous in action and sufficiently protected from the environment to 
insure a true record of the surface temperature, and not a resultant of skin 
and environmental temperature. 
A method recently used at the Nutrition Laboratory consists of two copper- 
constantan junctions, one located in a constant-temperature bath — a Dewar 
flask — and the other appKed to the skin. The resulting current which can be 
measured on any one of several types of galvanometers is directly propor- 
tional to the temperature difference between the two junctions. All ther- 
mometric lag is thereby eliminated and it is only necessary that the junction 
which is applied to the body should be properly protected from the environ- 
mental temperature. It was found that when this junction was backed with 
