42 JAMES ROLLIN SLONAKEB 



these rats had always an abundance of fresh air. The home of 

 the exercised rat was a tin box with a certain number of ven- 

 tilating holes through it and an entrance. It was furnished 

 with sawdust and cotton for a nest. These rats were, there- 

 fore, more closely confined during their sleeping time than the 

 control. The air was not so fresh and so free from odors. In 

 fact it was hard to keep these boxes clean. These modifications 

 in environment I think had probably something to do with 

 the differences in growth and length of life in these two groups 

 of animals. 



CONCLUSIONS 



From the foregoing experiments and data I think the follow- 

 ing conclusions can be reached concerning the activity, growth 

 and longevity of the albino rat. 



i. The daily activity increases rapidly during about the first 

 third of its life after which there is a gradual decrease until 

 its death. 



2. The change in amount of daily activity is not gradual but 

 is rhythmic in character. 



3. The character of activity during youth and old age is 

 quite similar, being more or less distributed throughout the 

 24 hours. During the prime of life the activity is confined 

 principally to night and rest to day time. In other words, 

 the albino rat is nocturnal. 



4. The female is much more active than the male. 



5. Of the whole amount of work done during the life time 

 almost three-fourths is done before reaching middle age. 

 During the last 30 per cent of life only one-eighth of the total 

 work was performed. During the first 30 per cent of lifespan 

 almost three-eighths of the total work was done. 



6. The males far surpass the females in weight. 



7. The control males not only reach their maximum weight 

 at an earlier age than the exercised males, but also greatly 

 excel them. 



8. The control rats lived longer than the exercised rats. 



9. The exercised rats are more active, more alert and brighter 

 in appearance than the control ones. 



