122 THE VITAMINES 



animals. The animals showed a coarse and sparse coat, and a- 

 decreased resistance toward infections of all kinds, such as ophthal- 

 mia, and pulmonary affections, like pneumonia. Tsuli (339a) 

 investigated the action of deficient diets on thyroid, gonads, parotid, 

 pancreas and other organs. Aron (340) observed these conditions, 

 including neuro-paralytic changes in the skin, to which he also 

 attributed ophthalmia. Morgulis and Gies (340a) found the calcium 

 content of rachitic bones and teeth lower than in the normal. Mattill 

 (340b) compared the creatine, creatinine, and urea content of the 

 blood in fasting rats and those deprived of B-vitamine. The non- 

 protein N was increased in both cases in fasting animals, mostly in 

 the form of urea, while in the others, it was in the form of creatine. 

 Briining (340c) saw in rats fed on a carbohydrate-rich diet a patho- 

 logical condition arise resembling "Mehlnarhrschaden." 



A question that has greatly interested the author for a long time, 

 was to determine if with both of the above mentioned vitamines, all 

 of the nutritive requirements of the rat have been fulfilled. Looking 

 through the many reports dealing with this problem, one is tempted 

 to answer this question in the affirmative. First of all, we must see 

 whether the growth that has been obtained till now on artificial 

 diets, represents the optimum growth of rats. It is obvious from 

 most of the growth curves that growth on the experimental diet 

 compares favorably with that on a normal diet. To satisfy ourselves 

 on this point, we (I.e. 325) followed the growth of a number of rats 

 on a normal diet, which contained, among other things, yeast and 

 condensed milk. The experiments showed that the growth, regarded 

 by Osborne and Mendel and also McCollum as normal, was not the 

 optimum for this type of animal. For comparison, we append the 

 normal weight curves obtained by us, Osborne and Mendel, and 

 McCollum. It should also be noted that in a large percentage of 

 these investigations, particularly those of McCollum and his co- 

 workers, still more complicated food complexes were fed, which, at 

 least theoretically, might still contain one or more unknown factors. 

 On the other hand, we must admit that in laboratories greatly experi- 

 enced in rat nutrition, for example, those of Osborne and Mendel, 

 the condition of the artificially fed rats, in relation to the state of 

 health and the ability to rear their young, leaves nothing to be 

 desired. The explanation here may be that through considerable 

 experience a dietary composition has been chosen, the components 



