5 2 



FEEDING EXPERIMENTS WITH ISOLATED FOOD SUBSTANCES. 



-oio =J 



dead 



240 



Chart XXI. Rat 73 fed 181 days on Casein and Zein, and for 53 days on Pea-Legumin as the 

 only proteins. See p. 50. Numbers on Body-weight line indicate time at which 

 each period began. 



decline sufficient to explain their ultimate death. This fact strongly 

 suggests that death was not necessarily attributable to any primary 

 nutritive defect, but rather to incidental causes. Occasional fatali- 

 ties will not surprise those who have experienced the difficulty of 

 protecting a large number of rats, under the conditions noted, from 

 the appearance of infectious or parasitic maladies which may become 

 fatal. In the same surroundings sudden death has also come to not 

 a few of our animals on ordinary mixed diets consisting of seeds and 

 vegetables. In some cases obvious causes were revealed at autopsy ; 

 but systematic post-mortem examinations have not been attempted. 



With young rats fed similarly we have succeeded in maintaining 

 weight, although with little if any growth. In our preliminary 

 studies of growing animals the food intake was not determined with 

 appropriate care to correlate our findings with the altered curves 

 of growth; hence the insufficient diet rather than any chemical 

 deficiency may have been a possible cause of arrested development. 

 Rats of 30 grams initial weight have been kept by us for many days 

 without gaining weight when fed with a mixture containing a single 

 protein ; with desiccated milk in the food they subsequently attained 

 a perfectly normal growth. 



Despite the obstacles encountered we are inspired to the belief 

 that with modifications in the feeding suggested by our first year's 

 experiments still further progress can be made. Meanwhile further 

 conclusions respecting the inadequacy of the individual proteins for 

 nutritive functions are not justified. 



