ioo GROWTH 



mineral matter, and in water. It is equally obvious that if 

 growth has taken place and the body weight has remained con- 

 stant, there must have been a decrease in the content of body 

 fat, and presumably of glycogen. One of the earlier attempts 

 to maintain constant weight has been recorded by Aron. 49 He 

 observed that puppies may be held at constant weight for sev- 

 eral months by restricting the food supply, but ultimately the 

 animals would die of starvation unless the food supply were 

 increased sufficiently to permit at least some gain in weight. 

 Stewart and Jackson made similar observations on albino rats 

 under somewhat more severe conditions, and noted that death 

 ultimately intervenes if the young are maintained at birth 

 weight. 



We have seen then that there is a lower limit below which 

 the food supply cannot be reduced without disastrous conse- 

 quences. We will next consider the case of an animal that re- 

 ceives a quantity of food sufficient to at least permit some 

 growth throughout the experimental period, yet decidedly in- 

 adequate in amount to permit growth to proceed at the normal 

 rate. 



One of the first such studies does not answer the question en- 

 tirely, as it was not continued sufficiently long to enable us to 

 decide whether or not growth was permanently retarded. This 

 is the work of Waters. 50 He placed fifteen yearling steers on a 

 ration that permitted no gain in weight, and observed the result- 

 ing changes in conformation. It was noted that skeletal growth 

 continued, the steers increased in length and height, but of 

 course the fat reserves were depleted, and the steers became 

 exceedingly thin. 



It is then well established that even during semistarvation, 

 true growth is by no means completely suppressed, but the chief 

 interest is attached to the permanent consequences of under- 

 feeding. In some respects it would be simpler to take up the 

 more important contributions in chronological order, but for 

 the sake of clarity it may be best to arrange them in two groups. 



