VITAMINES 



247 



The fourth rat was allowed to remain with its mother, sharing 

 the same food (fig. 18). For 50 days scarcely any growth took 

 place, i.e. the food that had been sufficient to enable the mother 

 to produce young and secrete sufficient milk, both as regards 

 quantity and quality, for bringing up the offspring for 30 

 days, was not able to induce normal growth after this time. 

 The essential growth vitamine was missing, and though the 



100 



ec- 



ho 



40 



Oqus 2o 40 



fco 



80 



140 



'fee 160 ZOO Z20 



100 120 

 Fig. 18. 



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



substitution of milk protein for gliadin prolonged life for 

 some time, the animal eventually died before it was half grown. 



The generation of these young rats whilst the mother rat 

 was living on a diet containing a single protein is really most 

 remarkable. During this time a large new formation of body- 

 tissue must have occurred, involving the synthesis of purines, 

 nucleic acids, pyrimidines, phospho-proteins, casein, lipoids, 

 etc., and probably the actual synthesis of the growth vitamine, 

 inasmuch as normal growth of the young rats was maintained 

 whilst they were being suckled by their mother. As, from the 

 same diet, the young rats themselves were unable to form the 

 growth vitamine, the production of the growth vitamine is 

 manifestly a function of the mature female. 



These experiments all go to show that for growth a mys- 

 terious " something " — the growth vitamine— is necessary. This 

 vitamine is associated with the fatty constituents of milk, and is 

 not destroyed by heat. Everything points to^the probability of 

 its being a different substance from those responsible for the 



