VITAMINES 



241 



milk (a commercial article consisting of lactose and salts, with 

 only a small amount of fat and protein) be added to the diet, 

 the resulting mixture is adequate to keep the rats in excellent 



<"" Days. 



Fig. 11. — Curve showing variation of weight of rat on different foods. The lower 

 dotted line shows weight of food eaten by rat. 



(From the Journal of Biological Chemistry, vol. xiii. 1912.) 



condition for many months. Some of their experiments with 

 individual rats have extended over 600 days. 



As an example of their work, I have selected fig. 1 1 (repro- 

 duced from the Journal of Biological Chemistry, vol. xiii. 1912). 

 During the first 60 days, on a diet of casein, starch, sugar, lard, 

 and salts, the rat was evidently being insufficiently nourished. 



240 



Tli 260 £*AY3 



Fig. 12. — Curve showing variation of weight of rat before and after 

 addition of milk 10 diet. 



(Aus Thomas B. Osborne und I<afayette B. Mendel unter Mitwirkung von Edna L. Ferry, Beobachtungen 

 iiber Wachstum bei Futterungsversuchen mit isolierten Nahrungssubstancen in Hoppe-Seyler's 

 Zeitschrift fur Physiologische Chemie, Band Ixxx. Verlag von Karl J. Trtibner, Strassburg.) 



Substitution of protein-free milk for the sugar restored the rat 

 to its original weight. After 170 days the casein food was 

 again tried, and immediately the weight of the rat began to 

 fall, to be again restored when the diet was supplemented by 



