396 GAULE. [Vol. VIII. 



in June, because the fibers are most clearly and sharply defined 

 at this period. 



Physiologists often find it impossible to demonstrate the 

 laws of nerve and muscle reactions with the usual degree of 

 accuracy in the late spring and summer, whereas the demon- 

 strations of the same laws are comparatively sure in the fall 

 and winter. 



Effect of Artificial Surroundings. 



It is often painfully evident to those experimenting with 

 frogs that the reaction following certain operations, or the 

 absorption of poisons, varies perceptibly from day to day in 

 captivity. The cause of this inconstancy may be referred to 

 the difference in temperature and in the character of moisture 

 in captivity and possibly to the lack or different character of 

 the food, though it is not sure that these influences alone 

 suffice to explain the mystery. 



Giirber in "Die Gesammtzahl der Blutkorperchen und ihre 

 Variation" proves that complete dryness produces remarkable 

 changes in the character of the blood. He found that frogs 

 which had been kept perfectly dry for eight days lost more 

 than one-half of their red-blood corpuscles in that time and 

 that the spleens of such frogs became extremely large. He 

 says, "I believe that the effect of dryness and moisture as 

 here demonstrated by the varying number of the blood cor- 

 puscles must play an important role in the household of the 

 frog." 



The question arises whether the natural dryness which tem- 

 poraria seeks in the summer months is not perhaps essential 

 to the life-cycle of this species. If so, we may expect to find 

 traces of the influence of dryness in the histological struct- 

 ure of the spleens during the summer months. 



Methods of Investigation. 



As I mentioned above, both Rana esadenta and tempo- 

 raria, were made the subject of study. In the earlier part of 



