320 Journal of Comparative Neurology. 



exposure to a shallow bath. The water was taken up entirely 

 by means of the part of the body immersed, as frogs do not 

 under any circwnsta^ices take water by the mouth. 



In other similar experiments, a slightly greater loss of 

 water than that here recorded, caused the frog to die in convul- 

 sions, so that the loss above given, approximates the limit to 

 which drying can be carried. The rate at which the water was 

 absorbed was surprising, nevertheless the frogs remained in good 

 condition, as was shown by the vigorous manner in which they 

 jumped away when set free an hour later. 



We conclude, therefore, that to obtain from a series of 

 frogs records which shall be comparable, the frogs should be 

 put in water for a few hours before they are examined and thus 

 allowed to absorb the maximum amount of water which is nor- 

 mal for them. 



The major part of the observations recorded in this paper 

 were made on frogs kept in a large dark box beneath which 

 flowed a small brook, the box being so arranged that they could 

 be in or out of the water at will. It was assumed that they 

 would all be equally moist, but the records show that even un- 

 der these conditions some frogs are found much dryer than 

 others. 



The influence of the water absorbed, on the weight of the 

 central nervous system and on the ratio of the brain weight to 

 that of the spinal cord, is shown by the following observations, 

 all made on one lot of frogs collected from the same locality, in 

 the month of July. 



They were made on successive days on groups of three 

 frogs at a time. The group marked A "wet," had been in 

 about half an inch of water for twenty four hours previous to 

 the examination. Those marked B "dry" had been in a dry 

 dish for the same length of time. 



TABLE 6. 



Average body weight in grms. Average brain Average spinal cord 



Frogs " wet." Weight. Weight. Ratio. 



Group A, 211, "wet." .198 .097 2.04 



Group B, 211, "dry." .197 .084 2.34 



