PROTEIN REQUIREMENTS 67 



the extreme values of Voit and KorkunofF. Michaud (284), who has 

 since dealt with this problem, attributed the previous failure of workers 

 to get nitrogenous equilibrium with the fasting nitrogen output to the 

 fact that the protein fed differed too markedly in composition from that 

 of the tissue protein. He nearly reached the hunger minimum if he 

 fed a protein which was of exactly the same constitution as the tissue 

 protein, i.e. if he fed dogs on dogs' flesh. As a result of his experiments, 

 he drew up a scale of the amounts of protein required. This scale 

 varied according to the similarity in composition of the protein to that 

 of the tissue. Flesh of another animal horse flesh fed to a dog was 

 less valuable than dog flesh, caseinogen was still less, and vegetable 

 protein the least. He did not believe that the apparent unsuitability 

 of vegetable protein depended on the lack of extractives present in 

 these proteins. Zisterer (425) has published experiments which 

 substantiate this hypothesis of Michaud. He agreed with the general 

 results reached, although he thought that Michaud was not careful 

 enough in establishing his hunger value. Zisterer's figures for the ratios 

 of the different protein material as regards the minimal requirements 

 were as follows : 



Dog's Flesh. Horse Flesh. Caseinogen. Nutrose. Edestin. Gliadin. 



loo 108 128 121 153 163 



These figures bear out the conclusion reached by Michaud, that an 

 an animal can subsist on an intake of protein which is lowest when the 

 protein given resembles most closely the tissue protein. Recently 

 Frank and Schittenhelm (49) have carried out some work along the 

 same line as Michaud. They found, however, that all their dogs did 

 not give the same results. Thus, one dog, which was tested with a 

 protein mixture prepared from the " whole " animals of the most varied 

 species, did not reach the lowest level of nitrogen intake with the dog 

 preparation. On the other hand, two other dogs most unmistakably 

 showed a diminution in nitrogen output when placed on dog flesh. 

 They also tested a boy with goose, fish and ox flesh, and found that 

 goose flesh took first place, and fish flesh next. Busquet (83) in a 

 somewhat similar set of experiments on frogs found that if frogs were 

 fed with frog muscle the gain in weight by the animal was much 

 greater than when they were fed with the same amount of ox flesh ; 

 Billard (65) found that tadpoles fed on frogs' liver developed even 

 better than those fed on calf-liver or algae. 



Siven (374, 375) carried out a long investigation on the question 

 of the possibility of reducing the protein intake employing an entirely 

 different method. He experimented upon himself, using diets contain- 



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