NUTRITION. 383 



proteins unsuitable for the synthetic processes of growth, or is low in 

 protein. Growth in the cases referred to is resumed at a rate normal 

 for the size of the animal at the time. It need not be slow, and may 

 actually exceed the usual progress. 



The period of growth may be greatly prolonged by inadequacies in 

 the diet so that growth becomes very slow without being completely 

 inhibited. Though the time of reaching full size is thus greatly de- 

 layed, growth, as indicated by body-weight, can ultimately be com- 

 pleted even during the course of an enforced retardation. 



The methods of partially retarding or completely suppressing growth 

 are too varied and unUke to permit final answers as yet regarding the 

 outcome of all of the procedures of inhibition for the subsequent welfare 

 of the individual. Our observations apply to the effects upon size and 

 a few other incidental features mentioned. Although it is doubtful 

 whether the fundamental features will be altered, far-reaching dogmatic 

 statements are scarcely justifiable until the experiments have been 

 extended to include other factors and other animal species. 



The experiments mentioned in our last report as being undertaken 

 with some of the high-protein feeds which were designed to show the 

 most economical combinations in which these can be used to furnish 

 protein for both growth and maintenance have been in progress during 

 the present year and are yielding results of interest. Work along these 

 fines is being continued as rapidly as facilities admit and it is expected 

 that before long we shall have sufficient data for our first publication 

 on this subject. 



An attempt to study the value of gelatin in nutrition yielded such 

 results that we felt the need of a more precise knowledge of the amino- 

 acids yielded by this pecufiar protein before continuing them further. 

 We have therefore devoted much time to an analysis of the products 

 of hydrolysis of gelatin and incidentally have obtained much infor- 

 mation respecting the shortcomings of the methods available for deter- 

 mining the amount of the various amino-acids yielded by boihng 

 proteins with strong acids. It is hoped that the experience thus 

 gained may lead to improvements in the methods whereby the results 

 may be more nearly quantitative than in the past. 



The preparation of large quantities of ''protein-free milk" used in 

 our feeding experiments has given us an opportunity to study a num- 

 ber of substances which are present in milk in very small propor- 

 tions, but which may have much more importance in nutrition than 

 has heretofore been assumed. Whether milk contains lecithin or 

 similar phosphatides has long been discussed, but no satisfactory evi- 

 dence on either side has been set forth. We have been able to settle 

 this question finally, by isolating from the alcohol washings of lactal- 

 bumin relatively large quantities of two different phosphatides. One 

 of these is a monaminophosphatide containing nitrogen and phosphorus 



