THE EFFECT OF THE BEARING OF YOUNG UPON 

 THE BODY-WEIGHT AND THE WEIGHT OF THE 

 CENTRAL NERVOUS SYSTEM OF THE FEMALE 

 WHITE RAT. 



By John B. Watson. 



{F)-om the Neurological Laboratory of the University of Chicago.) 

 With Plate VI. 



By observations in this laboratory the results of which are 

 as yet unpublished\ the normal increase in the body weight of 

 the female white rat, uninfluenced by the bearing of young, has 

 been determined. In this connection, a question arose as to 

 the effect on the body growth, if the females were allowed to 

 breed normally. The present paper reports the results of an 

 investigation carried out in answer to this question. In addi- 

 tion to the above, there arose the further question, as to the 

 effect of the bearing of young upon the weight of the central 

 nervous system, and on the percentage of water contained in it. 



So far as the writer knows, only three men have published 

 observations bearing directly upon the subject in hand; viz., 

 Edlefsen, Hensen and Minot. 



Edlefsen recorded the changes in the weight of 7 female 

 guinea pigs from birth to the end of their first pregnancy. Un- 

 fortunately he compared the weight of the females during preg- 

 nancy with the weight of the males of a corresponding age. He 

 made two points clear: ist, the actual growth of the female 

 guinea pig is slower during the period of gestation than that of 

 the males of the same age during the same time ; 2nd, that 

 while the true body weight of the mother immediately after 

 parturition is less than that of the male of corresponding age, 



^It is expected that the results of this investigation will be published at an 

 early date. 



