Slonaker, Activity of the Rat. 359 



inactive. Somewhere between these two extremes we find the 

 age of greatest activity. 



3. These experiments indicate that the age of greatest activity, 

 as represented by the number of revolutions of the revolving cages, 

 ranges between 87 and 120 days. 



4. Owing to the marked individuahty exhibited, a correct 

 curve of activity from birth to death cannot be constructed from 

 the results of one rat or of several individuals of different ages. 



5. A curve representing the normal activity from birth to 

 death due to senility must be based on the records of a number 

 of individuals of the same age and subjected to the same con- 

 ditions. 



6. The white rat is affected by light. This, I think, is mainly 

 due to the structure of the eye and to certain tendencies which 

 they inherited from their wild ancestors. 



7. From these preliminary experiments no correlation can be 

 made between the age at which they are most active and the age 

 at which they learn most rapidly. 



