TEMPERATURE SENSES IN FROG's SKIN 103 



Responses to cold 



Normal frogs respond promptly and definitely when they are 

 placed in water sufficiently cold. Such behavior was observed 

 by both Torelle ('03) and Brooks ('18), who recorded that frogs 

 immersed in water of 5°C. swam downward, attempted to regain 

 the surface a couple of times, but finallj^ sank to the bottom and 

 remained there. 



In studying the effect of cold, experiments such as had been 

 made by Torelle and by Brooks were repeated in the reflex frogs 

 so as to compare their behavior with that of normal frogs. 



The temperature of the frog was taken before and after the 

 experiment. Four gallons of water at a temperature of 4°C. to 

 5°C. was kept in an aquarium jar in the laboratory and frogs 

 were placed in this water for periods of two minutes. Short 

 records of observations were made by fifteen-second intervals 

 (table 12). The first responses were uniformly either a spasmodic 

 jump or a 'set' of the whole body hke the 'freeze' of a rabbit, 

 followed by a series of jumps, then a gradual sinking in which 

 the body fell rigidly backward or forward and finally rested 

 stiffly on the bottom of the jar with the legs extended. These 

 responses were generally very uniform, but when there were 

 individual peculiarities they were persistent. For example, 

 frog no. 16 was tested on different days, but its immediate response 

 to cold was always a sudden 'set' in which the legs were tightly 

 flexed to the body, the toes extended, with the web tightly 

 stretched and the soles out. In this position the frog would sink 

 to the bottom without a contraction; it did not, however, lose 

 its rigidit}' even when it was turned from side to side with a rod. 



A few similar observations were made upon normal frogs to 

 compare their behavior with reflex frogs. The two records 

 presented in table 13 are typical of a half-dozen. Normal 

 frogs floated longer at the surface than reflex frogs did, but in 

 other respects the behavior of the two kinds was essentially 

 the same. 



Alternate dipping of the feet in water at 2°C. resulted in much 

 the same response as did total immersion. The characteristic 



