NUTRITION AND GROWTH 



577 



growth vitamines?), to which were added more carbohydrate, purified 

 fat, and the protein whose influence on growth it was desired to study. 

 The same diet was fed at regular intervals to a given batch of rats, and 

 the weight of each rat was periodically taken, the observation being pro- 

 longed until the animals grew to maturity and produced young, and these 

 again grew to maturity, reproduced, and so on. By plotting the re- 

 sults in curves, with the time periods along the abscissae and the average 

 weight of the rats of each batch along the ordinates, the extent of the 

 influence of a given diet on the curve of growth was obtained. A normal 

 curve of growth is shown in No. 1 of Fig. 183. It was obtained from re- 

 sults secured by adding liberal amounts of casein to the basal diet. 



wt 



(*0 

 joo 



Days 



Each division -20 days 



Days 



Each division -20 days 



Fig. 184. Curves of growth of rats on basal rations plus the proteins indicated. In curve 



III the effect of the addition of zein to an inadequate allowance of thei perfect protein, lactalbumin, 



is shown; and in IV the effect of the addition of cystine to a deficient casein allowance. (From 

 Lafayette B. Mendel and T. B. Osborne.) 



Similar curves were obtained with lactalbumin of milk and ovalbumin 

 and ovovitellin of egg. Perhaps the most interesting substances capable 

 of producing the normal curve of growth are certain of the proteins that 

 T. B. Osborne has succeeded in separating in crystalline form from 

 vegetable foodstuffs. These are edestin (hempseed), globulin (squash 

 seed), excelsin (Brazil nut), glutelin (maize), globulin (cottonseed), 

 glutein (wheat), glycinin (soy bean), cannabin (hempseed). 



That growth proceeds normally with any one of these proteins when 

 fed abundantly does not, however, necessarily indicate that each con- 

 tains in adequate proportion all of the necessary units to meet the pro- 

 tein demands of growing tissues. In the case of casein, for example, 

 one of the units, namely, glycocoll, which is the simplest of all the 



