BODY TEMPERATURE OF MICE 321 



It seemed possible that, in a very cold room, an appreciable 

 amount of heat might be conducted from the bulb of the thermom- 

 eter to the stem, and from the latter radiated to the surround- 

 ing air. Apparent differences of body temperature in the two 

 rooms might thus result. Tests were accordingly made by dipping 

 the thermometers into water of about body temperature, at the 

 time when the surrounding air was between 1° and 2°C. Ther- 

 mometer 'number 2' gave a mean reading less than one tenth of 

 a degree higher when the entire stem was immersed in the warm 

 water than when it was immersed only as far as the rubber ring 

 on the neck. With the other two thermometers no certain differ- 

 ences were detected, and it is plain that with all of them this 

 source of error may be left out of consideration. 



In taking the temperature of an adult mouse, I lifted the animal 

 quietly, and placed it upon a table or other flat surface. With 

 mj^ left hand, I grasped the tail, raising the hind quarters some- 

 what from the table, but allowing the fore-feet to rest upon it. 

 The thermometer bulb was coated with vaseline and inserted 

 into the rectum. Animals varied greatly in their behavior under 

 this treatment. Some, particularly^ females, remained nearly or 

 quite passive. Others tugged hard in their endeavor to get away, 

 or move about freely in various directions. This latter mode of 

 behavior naturally rendered the observations difficult, and further- 

 more it was noted that the struggles of the animal often had a 

 marked effect upon the temperature recorded. 



It was found at the commencement of the experiments not 

 only that different individuals varied greatly in their rectal tem- 

 peratures under apparently identical conditions, but that the same 

 individual, in the course of a very few minutes, might give read- 

 ings which differed to a striking extent. Moreover, mice varied 

 greatly in the way in which their temperature changed within 

 the course of a single observation. In some cases, the mercury 

 rose to a fixed point within a half minute or less, remaining sta- 

 tionary for a considerable period thereafter. In other cases, it 

 continued to rise slowly and steadily after the first rapid ascent 

 following insertion, and did not entirely come to rest, even within 

 two or three minutes. Not infrequently, the mercury rose by 



THE JOCRNAL OF EXPERIMENTAL ZOOLOGY, VOL. 15, NO. 3 



