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SCIENCE 



[N. S. Vol. XXXIV. No. ! 



component in the mixture that a defect ought 

 soon to manifest itself — as indeed it did with 

 zein. Nor did the animals fare better when 

 more than one protein was present. Here, too, 

 the ultimate decline in the grown rats in- 

 evitably showed up, as will be seen in the 

 illustrative charts below. 



What is the factor or what are the causes 

 connected with the ultimate failure of the 

 older rats to thrive on the dietaries outlined, 

 or of young rats to grow? Evidence which 



Days 



Pig. 5. (Taken from Carnegie Publication No. 

 156, page 46.) This rat was fed 160 days on a 

 diet containing casein and pea legumin as tlie only 

 proteins. 



Remarkable in this connection were the ob- 

 servations made on small white rats during 

 the period of active growth. Lacking food, at 

 this stage, the animals speedily die, since the 

 reserve stores are small or wanting. With an 

 appropriate mixed diet growth is vigorous, and 

 the rate of gain is strikingly similar in healthy 

 animals of related origin. When young rats 

 are fed on diets containing a single protein in 

 the mixtures described above they fail to grow, 

 although they can be maintained at uniform 

 body weight and size for long periods. Here 

 then is an evident distinction between main- 

 tenance and growth in respect to the function 

 of the ration. An illustration of the stunting 

 of animals in this manner is graphically af- 

 forded by the appended curves in which a 

 dwarfed animal is compared with a suitably 

 fed one from the same litter. 



Fig. 6. Showing the body weight and food in- 

 take of a small rat grown normally on a diet of 

 dried milk and lard in the upper curves. The 

 lower curves are charted from a rat of the same 

 litter maintained without growth on a diet con- 

 taining glutenin as the sole protein in a mixture 

 unsuitable for growth. 



need not be reviewed here pointed to some- 

 thing other than the character of the protein, 

 fat or carbohydrate. Animals will thrive and 

 grow on a " mixed " diet of corn, vegetables, 

 etc.; but we have, furthermore, noted that 

 their nutritive needs can be met with an " arti- 

 ficial " food mixture in which dried milk and 



