VITAMINES 



245 



normal rat had long since reached maturity and ceased to grow, 

 some milk was added to the diet. Normal growth now set in, 

 and this old rat started growing so fast that it put on as much 

 weight in 26 days as in the previous 265 days of inadequate 

 diet. (The broken line indicates the growth of the normal 

 animal.) Evidently in the added milk there is the vitamine 

 necessary for growth. 



The next diagram shows the commencement of growth of a 



Doua 20 



40 



60 



80 



100 



120 



\4C 



160 



190 



200 



FlG. 16. — Rat on casein and protein -free milk. 

 (From the Journal oj Biological Chemistry, vol. xii. 1912.) 



number of young rats, and their inevitable death when the diet 

 consisted of an artificial mixture of proteins, fats, carbohydrates, 

 and salts, with dried protein-free milk. This food, it may be 

 once more emphasised, has been proved to be quite adequate 

 to maintain adult rats in good health for at least one and a half 

 to two years. 



The next example shows that the addition of the growth 



17 



