20 JAMES ROLLIN SLONAKER 



movements were very slow and feeble having lost all the alert- 

 ness and quickness common to their youth. The record of No. 

 i represents its activity just two days prior to death due to 

 old age. During the last day of its life this rat turned its cage 

 94 revolutions which was a small amount cdmpared with over 

 6,000 accomplished in the prime of its life. 



Fig. 7 represents the activity at the age of 26 months. The 

 two remaining males, Nos. 2 and 4, show the characteristics of 

 old age, while the female No. 3 still shows the activity char- 

 acteristic of middle life. The record for No. 4 shows the last 

 dav's work of this rat which consisted of 48 revolutions. It 

 also shows its final death struggles which began at 7 p. m. and 

 ended soon after 9. 



The remaining figures, 8, 9 and 10, show the effect of extreme 

 old age. They represent the ages of 28, 31 and 34 months 

 respectively. Fig. 9 shows the record of No. 2 just two days 

 previous to its death. It is quite similar in its appearance to 

 that of No. 3 in Fig. 10, which is the record of this rat just two 

 days prior to its death at an age of almost 34 months. 



From the observations of the records (Figs. 1 to 10) of any one 

 rat, from the first to its death, the following points may be 

 easily seen : 



1. The daily activity increases with the advance in age until 

 a certain age is reached, after which there is a gradual reduc- 

 tion till death occurs. 



2. Distribution of the activity. In youth it is rather uniformly 

 distributed over the entire 24 hours. With maturity activity 

 becomes concentrated into one period and rest into another. 

 In extreme old age the activity becomes scattered and resembles 

 that of the very young. 



3. During the prime of life the albino rat shows almost con- 

 tinuous activity for periods of as much as two hours at a time 

 (Fig. 4, No. 3). 



4. The albino rat is nocturnal in its habits. 



5. This female is much more active than any of the males. 



THE AMOUNT OF DAILY ACTIVITY 



We have just considered the character of the activity of the 

 rat at different ages in regard to its distribution during the 

 entire dav. Let us now consider the actual amount of running 



