Donaldson, Nervous System of the Frog. 319 



might be subject to considerable alterations in weight. As these 

 normal alterations in a measure account for variations in the 

 ratio of the weight of the brain to that of the spinal cord, we 

 shall present such observations as we have made upon this 

 point. 



The amount of water in a frog is subject to rather wide 

 fluctuation. In support of this statement, the following typical 

 observation is offered. Six frogs, were freshly caught at 

 8 a. m., and divided into two groups of 3 each. These groups 

 are designated as A and B. 



At 9:30 a. m., August 12th., 



Group A. (3 frogs) weighed 132 grams. 

 " B. (3 " ) " 125 " 



Immediately after the weighing, each group was put in a 

 shallow earthen dish about 30 cm. in diameter and the dish cov- 

 ered with a sieve. The dishes stood side by side, out of the di- 

 rect sunlight, but exposed to a moist breeze. 



The dish containing Group A. was dry, that containing 

 Group B. had several layers of very wet filter-paper on the bot- 

 tom. At the end of exactly seventy-two hours : 

 Group A. weighed 93.5 grams. 

 " B. " 1 21.0 grams. 



Thus, both groups had lost weight during this time, which 

 was to be expected, since they had been without food. 

 The loss in Group A was 29 %. 

 " " " B " 3.2 %. 



The loss in Group B was due to lack of food and to defeca- 

 tion ; in Group A, to similar causes combined with drying, 

 hence the difference in loss amounting to 25.8 %, approxi- 

 mately represents the loss of water from Group A. 



It is plain therefore, that a frog can lose a quarter of its 

 weight by slow drying. After the last weighing, fresh water suffi- 

 cient to cover the frogs above the level of the anus was put in 

 both dishes. Within three hours after adding the water, Group 

 A attained a weight of 134.5 grams, while the weight of Group 

 B was not changed. Thus all the water which had been lost 

 during three days of drying was regained by the three hours 



