STATISTICS OF NUTRITION 617 



and no glycin, or yields too little to be detected with certainty. 

 It also yields comparatively little histidin and arginin. Now, it 

 has been found that a dietary containing carbo-hydrate in the form 

 of starch, fats in the form of lard, and inorganic salts, but no pro- 

 tein except gliadin* suffices to maintain adult rats in good condition 

 for very long periods (up to 290 days), and also to maintain young 

 rats in a stationary condition as regards growth, but in perfect 

 health. The youthful appearance of the rats whose growth was 

 thus inhibited was very striking, and corresponded with their size 

 rather than with their age. The capacity for growth on a normal 

 diet was apparently not in the least diminished; the growth pro- 

 cesses simply remained in abeyance. 



' In one rat, after a continuous suppression of growth lasting 277 days, 

 when the animal was 314 days old an age at which normally little or 

 no growth takes place satisfactory growth was resumed on a suitable 

 diet.' A still more remarkable experiment was the following: ' A male 

 rat, kept for 154 days with gliadin as the sole protein in the food, was 

 paired with a female also on the gliadin diet. At the end of 178 days 

 on the gliadin diet she gave birth to four young, which were satisfactorily 

 nourished by the mother, still on gliadin, during the first month of 

 their existence. After a month three of the young rats were removed 

 from the mother and put on diets of casein food (i.e., casein plus suitable 

 proportions of carbo-hydrate, fat, and inorganic materials), edestin 

 food and milk food respectively. The fourth was left with the mother. 

 The fourth rat began to evince a failure to grow at about the period 

 (thirty days) when young rats are wont to depend upon extraneous 

 food. 



The meaning of this last observation can only be that the young 

 animal, when obliged to depend upon its share of the gliadin food, 

 left with the mother in place of the milk formed by the mother 

 from this same gliadin food mixture, showed the typical failure to 

 grow on a diet inadequate as regards the power of producing growth 

 in respect to the protein contained in it. On the other hand, in the 

 body of the mother this inadequate diet had been so transformed 

 that not only had she maintained her body-weight and repaired 



* Certain accessory substances of unknown nature, contained in some of 

 the natural foods must also be supplied (p. 632). Osborne and Mendel, for 

 instance, gave their animals a certain amount of ' protein-free milk,' contain- 

 ing the salts of milk, but only traces of milk proteins. The important thing 

 in the ' protein-free milk ' is neither the slight residue of protein nor the salt, 

 but an unknown substance, a so-called 'water-soluble vitamine.' When this 

 was supplied in the ' protein-free milk ' the animals were maintained on the 

 artificial diet for very long periods, although they did not grow. It has since 

 been rendered probable that in addition to the water-soluble vitamine, fat- 

 soluble vitamine (McCollom) is necessary for full growth of rats and the main- 

 tenance in health of the adults, upon otherwise complete artificial diets, for 

 a great part of their natural life-span. Such fat-soluble vitamines may be 

 supplied by replacing a part of the lard by butter-fat, egg-yolk fat, beef fat, 

 or codliver oil. 



