BODY TEMPERATURE OF MICE 339 



upon rodents, with a view to determining the influence of air 

 temperature upon body temperature. Unfortunately, this writer 

 has pubUshed only his bare averages, giving no clue to the 

 variability of his readings, ^^ and has furnished but a brief state- 

 ment of the methods employed by him. On the other hand, the 

 number of his temperature readings, belonging to each homo- 

 geneous group, was evidently much greater than in my own 

 experiments. 



Congdon's summary of his results has already been quoted (pp. 

 317-318). The striking differences between his results and my 

 own are evident: (1) a much greater difTerence in body tempera- 

 ture, resulting from differences in atmospheric temperature, and 

 (2) a much lower mean body temperature for the mice in general. 

 I shall consider these two points in order. 



Congdon states (p. 707), on the basis of experiments upon ten 

 adult mice, that transfer from the warm room in which they had 

 been reared (16°C.) to a temperature of 5° resulted in a mean fall 

 of 3° in rectal temperature; while, in another lot of ten mice, 

 transfer from 16° to 33°, in two steps, led to a total rise of 1.5° 

 in body temperature. These mice, after the change, were each 

 tested on five different days, extending through a total period of 

 nineteen days, and the effect stated was found to persist through- 

 out this period. No figures are given for adult mice which were 

 reared (and tested) in the warm and cold rooms respectively, but 

 such figures are given for adult rats (p. 705) . Ten of these animals, 

 kept at a temperature of 33°C., showed a mean temperature 1° 

 higher than ten which were kept at 16°. 



In my own experiments, no temperature reduction as great as 

 3° was found in any single case, even with changes of air tem- 

 perature much greater than those referred to by Congdon. ^^ In 

 table 7, for example, two adult males and two females were sub- 

 jected to a fall in atmospheric temperature of 19° in the course 

 of 15 hours. The mean reduction in body temperature was 0.75° 



^^ Dr. Congdon has recently been so kind as to show me some of his original 

 notes. 



^■^ Exception being made of the two mice which lost their power of temperature 

 regulation. 



