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 B x 



\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 



