202 



Scientific Proceedings (128) 



and in attempts to determine the vitamin A content of different 

 foods. 



The body can also store vitamin A at later ages. Thus two 

 male rats of the same litter and of the same weight at four weeks 

 of age were placed on two diets one of which was richer in vita- 

 min A because of containing a higher proportion of milk than 

 the other. After completion of growth, both were placed at 

 the same time upon the same experimental diet deficient in vitamin 

 A, and the survival period was found to be nearly twice as long 

 in the case of the one which had received the diet containing the 

 larger proportion of milk. 



Rats of the same litter grown to adult size on the same diet, 

 showed strikingly uniform survival periods when placed at the 

 same age on diets devoid of vitamin A, even though these latter 

 experimental diets were made to vary widely in their mineral 

 content. 



The investigation is being continued in several directions : 

 (1) by further experiments with rats transferred at different 

 ages from adequate diet to diet devoid of vitamin A, (2) by 

 experiments in which the vitamin stored in different organs and 

 tissues is determined directly by dissecting animals of known 

 age and dietary history 7 and feeding the different parts, (3) by 

 further studies of possible relationships between vitamin A and 

 the mineral metabolism. 



100 (2060) 



Some modifications of Emil Fisher's micro-polarimeter. 

 By SOMA WEISS 



[From the Department of Pharmacology, Cornell University 

 Medical College, New York City.] 



The quantitative determination of organic compounds by 

 means of their optical activity is often convenient, and it is often 

 necessary to employ small amounts of the solutions to be investi- 

 gated. 



