522 Journal of Comparative Neurology and Psychology. 



Conclusions. 



1. The groups of mated rats grew to be somewhat heav- 

 ier than the unmated groups. This was found to be true in 

 four out of the five groups, Group A being the exception (see 

 note, p. 521). The mated individuals were, on the average, 9 

 ^0 heavier than the unmated. 



2. The mated rats had both absolutely and proportionate- 

 ly the heavier central nervous systems. 



3. The weight of the brain, in the mated rats, was how- 

 ever not so heavy as we should have expected from the body 

 weight. Assuming that the brain weight should increase 



4 

 among mature rats in proportion to the}/ of the body weight^ 



and taking the unmated rats as the standard, we find that the 



brain weight observed in the mated rats would correspond to a 



body weight of 219.5 gr. But the observed body weight is 



226.2 gr. We draw the conclusion that the mated animals 



were somewhat fatter than the unmated — a conclusion which 



harmonizes with the facts observed at autopsy. 



4. The spinal cord was disproportionately heavy in the 

 mated groups. From the laboratory records of breeding 



females of about the same weight, it appears that one gram of 

 increase of body weight is accompanied by .oo20gr. of increase 

 in the weight of the cord. If we take the relation between the 



'DuBois found that in man at maturity the brain weights were related as 



4 



the^/ of the body weights. Dhbrb and Lapicque, have determined a like 

 relation in dogs of different sizes. 



