144 



Scientific Proceedings (59). 



88 (905) 

 Weight fluctuation in frogs. 

 By C. C. Guthrie and F. V. Guthrie (by invitation). 



[From the Physiological Laboratory, University of Pittsburgh.] 



It is known that frogs lose weight when removed from water or 

 very moist places and are placed in dry surroundings; and that 

 gain in weight occurs under reversed conditions. 1 To test the 

 magnitude of such change under local laboratory conditions, 

 beginning in 1909, several series of experiments have been per- 

 formed. Leopard frogs (Rana Pipiens) were used. 



The first series were performed during June and July and the 

 laboratory was not heated. During the day the windows were 

 opened and the temperature varied from about 23. 6° to 30.2 0 C. 

 Night temperatures were not taken, but the minimum observed 

 by the local weather bureau for the period was 16. 7 0 C. Showers 

 occurred during the experiment, so the air was not abnormally dry. 



Placed in water and weighed hourly, a maximum hourly 

 fluctuation of 10 per cent., a minimum o, and an average for 10 

 hours of 3.8 per cent, was observed. A total gain in weight 

 amounting to 20 per cent, occurred. Placed in wire cages in the 

 air of the laboratory a very rapid loss of weight occurred, amount- 

 ing to as much as 40 to 45 per cent, of the original weight in 

 twenty-four hours. If the loss was not greater than this, recovery 

 might take place if the animal were placed in water. The gain in 

 weight was very rapid, the total weight within four hours amount- 

 ing to as much as 121 per cent, of the original weight, or 200 per 

 cent, of the weight after drying. During the next sixty hours, 

 the weight fluctuated moderately, rising during the afternoon of 

 the second day to 136 per cent, of the original weight before drying. 



The time of death by drying is not very exactly shown by the 

 experiments, owing in part to the sluggish reactions supervening. 

 In one case the animal was alive thirty hours after being placed 

 in the dry cage at which time the loss of weight amounted to 42 



1 Donaldson, Jr. Compar. Neurol., 1898, VIII, 314. A. Durig, Arch. f. d. ges. 

 Physiol., 1901, LXXXV, 401; 1901, LXXXVII, 42; 1902, XCII, 293. 



