DEVELOPMENT 279 



of sows not pregnant for the purpose of answering, if 

 possible, the question whether gestation is a period of 

 such severe physiological strain on the young mother 

 that it stops normal growth. A large number of animals 

 have been under observation in this experiment and the 

 results are fairly uniform. Measurements included rec- 

 ords of changes in body weight, heart girth, length of 

 body, height at withers, and other measurements. 



The investigation is not complete, and further work 

 may modify the conclusions which seem fully warranted 

 at this time. The results so far justify the following 

 conclusions : 



1. The exercise of the reproductive functions, con- 

 tinuously from the beginning of puberty to full maturity, 

 permanently decreases the normal adult size of the mother. 



2. This permanent effect on the size of the mother 

 occurs even under a favorable environment. 



3. The period of gestation is not a check to growth 

 when a full ration of nutritious food is supplied. The 

 rate of growth is not lessened during gestation. There 

 is some evidence that pregnancy is an actual stimulus to 

 growth. 



4. The period of lactation is a very severe physiological 

 strain on the young mother, and during this period growth 

 is apparently inhibited. 



5. After the end of lactation or when the young are 

 weaned, the rate of growth in the young mother is more 

 rapid than before pregnancy and more rapid than in 

 animals which have not been pregnant. 



