730 



SCIENCE 



[N. S. Vol. XXXrV. No. 882 



it is the peculiar combinations of the latter, 

 or some ideal " balancing " of the inorganic 

 ions therein, or the presence of traces of essen- 

 tial organic compounds, or all of these, which 

 guarantee the successful outcome, remains to 

 be ascertained. 



What has been accomplished thus far with 

 the new possibilities of investigation at hand 

 may be mentioned in brief. Eats which have 

 developed marked symptoms of decline on 

 mixtures of isolated food substances contain- 

 ing a single protein have been revived in a 

 way little short of marvelous by the substitu- 

 tion of the protein-free milk in place of part 

 of the previous (non-protein) food. Instances 

 have occurred where successful realimentation 

 has thus followed in animals practically mori- 

 bund. The chart below furnishes a graphic 

 illustration. 



Even more interesting is the role of this 



protein-free milk in facilitating growth. By 

 the use of protein-free milk to furnish the 

 " accessory " portions of the diet the relative 

 deportment of different proteins in growth has 

 been investigated. Thus adequate growth has 

 been noted where the sole protein was either 

 the casein of milk, the lactalbumin of milk, 

 crystallized egg albumin, crystallized edestin 

 from hempseed, the glutenin of wheat, or gly- 

 cinin from the soy bean. But noi all proteins 

 suffice to promote growth under otherwise 

 favorable conditions. The gliadin of wheat 

 (notably lacking in glycocoll and lysine) and 

 the hordein of barley (closely resembling 

 gliadin in its chemical constitution) suffice 

 for maintenance without growth. Zein, the 

 tryptophane-, lysine- and glycocoll-free protein 

 of maize, is alone insufficient for the main- 

 tenance requirement. How well growth can 

 proceed under these somewhat artificial condi- 



Fig. 8. Showing the growth curves of young rats fed on a diet 

 together with protein-free milk. The upper broken lines in each 

 rate of growth on mixed food. 



containing a single protein 

 figure indicate the normal 



