NUTRITION. 267 



nutrition. The experiments there described have been continued and ex- 

 tended and the following facts we now consider to be established. 



Rats can be maintained throughout their natural adult lives on a diet 

 containing a single protein, if the inorganic constituents and a part of the 

 carbohydrate is supplied in the form of "protein-free milk." 



Proteins of diverse chemical constitution, like casein, from cow's milk; 

 edestin, from hempseed ; or gliadin, from wheat flour, serve equally well for 

 maintenance. 



Proteins which yield no tryptophane, like zein from maize, or gelatin 

 from animal tissues, do not maintain rats in spite of an abundant food in- 

 take. Replacing a part of the zein or gelatin with an efficient protein results 

 in maintenance. 



Rats can not only be maintained throughout their adult lives on so-called 

 incomplete proteins, like gliadin, which yields no glycocoll or lysine, but even 

 (after long feeding therewith) can reproduce vigorous young and suckle 

 them normally. 



The foregoing facts appear to be the most conclusive evidence yet ob- 

 tained, not only of a synthesis of new protein by the animal, but of some of 

 the amino-acids from which the new protein is constructed. 



Growth depends on chemical conditions of nutrition which are different 

 from those of maintenance. A diet which fully meets all the requirements 

 for maintenance may be incapable of promoting growth. 



Growth is arrested if the diet contains an insufficient quantity of inorganic 

 constituents or a sufficient quantity in an improper state of combination. 



No growth results unless the diet contains a suitable carbohydrate. 



Growth fails unless the diet contains a sufficient quantity of protein of 

 proper chemical make-up. 



Normal growth is made on a diet free from fat, as well as all other 

 substances soluble in ether. 



Normal growth, to nearly full adult size, is made on diets containing, as 

 their sole protein, either edestin or glutelin from the hempseed, glycinin 

 from the soy-bean, glutenin from wheat, globulin from cotton-seed, lactal- 

 bumin or casein from cow's milk, glutelin from maize, excelsin from the 

 Brazil-nut, globulin from the squash-seed, or ovalbumin or ovovitellin from 

 the hen's egg. 



Very little growth was made on diets whose sole protein was legumelin 

 from the soy-bean. 



No growth was made on diets whose sole protein was gliadin from wheat 

 or from rye, hordein from barley, conglutin from the lupine seed, legumin 

 from the pea, or vignin from the cowpea. 



Young rats are neither maintained nor grow if the sole protein of the 

 diet is phaseolin from the kidney bean, zein from maize, or gelatin from 

 animal tissues. 



These results show that normal growth, to nearly full adult size, can be 

 made with proteins of very diverse chemical constitution, all of which, how- 



