STATISTICS OF NUTRITION 605 



other limitation of its chemical powers. While the cyclic (and hetero- 

 cyclic) compounds cannot be replaced by other ' Bausteine ' of the 

 proteins, they may to some extent replace each other. Thus it would 

 seem that tyrosin can be replaced by phenylalanin (Abderhalden). 

 While some of the food proteins like casein are sufficient by 

 themselves to supply all the amino-bodies necessary not only for 

 the maintenance, but also for the growth of the body, and can 

 accordingly be termed adequate or complete protein food sub- 

 stances, others, like gelatin, are insufficient by themselves to supply 

 the protein required for mere maintenance, still less for growth, 

 and may be spoken of as inadequate or incomplete proteins. There 

 is a third intermediate group, comprising proteins which suffice 

 when given as the sole protein food to maintain the body for an 

 indefinitely long period, and to repair the tissue waste without per- 

 mitting growth of the animal to take place. Gliadin and hordein 

 (see footnote, p. 604) are representatives of this group. The ex- 

 periments of Osborne and Mendel with gliadin are of special interest, 

 since this substance is very differently constituted from the ordinary 

 food proteins, as well as from the tissue proteins of the animal 

 body. While, as already stated, it yields very large quantities of 

 glutaminic acid, prolin, and ammonia, it either contains no lysin 

 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, fats, and 

 inorganic salts, but no protein 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 processes 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), edeotin 

 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 



