BODY TEMPERATURE OF MICE 341 



It seems to me more than possible that these differences between 

 Congdon s results and my own depend upon differences in the 

 methods employed. Congdon states that "the thermometer was 

 nserted just deep enough so that its neck was at the level of the 

 anal sphincter muscles" (p. 705). It has been stated above that 

 the proximal end of the bulb, in my exper ments, was 5 to 7 mm. 

 within the anal sphincter, and that the latter was further blocked 

 by a rubber ring or collar, fixed at a definite point on the elongated 

 'neck' of the thermometer. Thus I obtained the temperature of 

 a deeper lying part of the body than if the bulb had been just 

 within the anal sphinctei'. 



Now this difference in method would account for both of the 

 principal differences between Congdon's results and my own, 

 namely for the greater changes following changes of atmospheric 

 temperature, and for the lower averages given by Congdon 

 throughout. It would also account for the fact that the changes 

 of body temperature, n his experiments, persisted, apparently, as 

 long as the animals were kept at the temperatures in question. 



That the depth of insertion of the thermometer has a marked 

 influence upon the thermometer readings was shown by Finkler's 

 experiments upon guinea-pigs, already cited. This writer found 

 differences as great as 36.1° and 38.9° at depths of 2.5 and 9 cm., 

 respectively. Further, the difference between the readings for 

 animals kept at widely different temperatures was greater when 

 the thermometer was inserted to the former depth than to the 

 latter. In my own experiments, the dependence of temperature 

 upon depth of insertion was observed, though not in a systematic 

 way. Record is made of one such observation in table 1 1 (mouse 

 No. 24-3). (See, also. Supplementary Note, p. 354.) 



That the mean temperature given by Congdon for white mice 

 in general is abnormally low is confirmed by the fact that Pem- 

 brey gives a figure even higher than mine. He states^^ that 

 "the rectal temperature of tame mice was found to be 37.4° in 27 



'* Giving equal value to the warm-room and cold-room figures, and to those 

 for the old males, young males and females, respectively. 



