318 FRANCIS B. SUMNER 



2. Rats and mice (Mus musculus) approaching puberty show no differ- 

 ence of temperature whether reared at 33° or 16°. The common tempera- 

 ture is for young rats 37.9°, i.e., 0.7° higher than for adults reared at 33°. 

 For the young mice it was 35.7° to 35.9°, also evidently higher than the 

 adults would under like conditions show. 



3. Adult rats and mice if changed from 16° to 25° or to 33° undergo a 

 rise of average temperature for the 10 to 20 days following the change 

 of 1.5° to 2°. At 16° the temperature was 36.1° for the rats and at 25°, 

 37.8°. The mice had a temperature of 34.2° at 16° and of 35.7° at 33°. 

 [35.3° at 25°.] 



Mice approaching puberty changed from 33° to 16° and vice versa 

 showed temperature changes of about 1°. 



4. Adult rats removed from 16° to 5° undergo a fall of 1.8° to 34.4° 

 for a period of 19 days. Adult mice, some of which may have been earlier 

 at 33°, fell 3° after a light change of external temperature. Their tem- 

 perature was then 31.2°. They were measured during a period of 19 

 days . . . 



5. Myoxus glis, a hibernating animal, on removal from the 14° room 

 to the 25° room rose in rectal temperature 0.8° to 35.9°. 



The average temperature for the white rat is about 37° and for the 

 white mouse about 34.9° according to the criterion adopted above. 



The results of some experiments of my own, both with adult 

 and with young mice, are described in the present paper. These 

 experiments were incidental to certain studies of heredity upon 

 which I shall report as soon as practicable. The data which I 

 here offer are, I realize, insufficient for any very comprehensive 

 account of temperature control in mice. The number of individ- 

 uals in any one group is unfortunately too small for the strict 

 application of statistical methods, while many of the results are 

 equivocal, inasmuch as the various factors influencing body heat 

 were not, at all times, clearly distinguished. But as regards the 

 main problem which I set myself, namely the influence of atmos- 

 pheric temperature upon body temperature, under the conditions 

 of my own experiments, I think that an answer of some definite- 

 ness is forthcoming. 



No apology is needed, I trust, for publishing these data in full. 

 The fact that neither the individual variability nor the details 

 of experimental procedure have been recorded by some previous 

 writers renders it difficult to properly appraise their work. 



