FEEDING EXPERIMENTS WITH ABIURET PRODUCTS 41 



tained and there was even a certain retention of nitrogen. The body 

 weight increased and the general condition was good. Unfortunately 

 the experiment could not be prolonged as towards the end the enemata 

 were not well retained and this was of course followed by a diminu- 

 tion in absorption. 



The Value of Asparagine. 



The nutritive value of amides like asparagine is another question 

 very closely related to that of the maintenance of nitrogenous equili- 

 brium and the growth of animals fed on mixtures of amino acids. 

 It has been very actively discussed by agriculturists, as amides play 

 a large part in the nutrition of the herbivora. It is, however, one of 

 great interest from a general point of view, particularly as regards the 

 question of resynthesis in the body ; if it can be proved that an animal 

 can thrive when fed on a single amide or an amide mixture it is in- 

 direct evidence in favour of a transformation taking place of amino 

 acids one into another. 



Mercadente (280) was one of the earliest workers to suggest that 

 the formation of protein could take place from asparagine, particularly 

 in plants. He believed that a decomposition first took place. Schulze 

 (363) also recognized the possibility of such a synthesis occurring, al- 

 though he found it difficult to believe that the simple direct union of 

 the amide with the nitrogen-free substance could yield protein. Sachse 

 (346), on the other hand, thought that asparagine formed protein 

 simply by the addition of fatty aldehydes. O. Loewi (258) believed 

 that asparagine was converted into protein in the presence of carbo- 

 hydrate by a series of condensations. 



As regards animal metabolism, Zuntz (426) suggested many years 

 ago that in the herbivora before utilization the amide was built up 

 into a protein by the aid of "Pansen" bacteria and that the animal 

 lived on the protein thus formed. Miiller (291) states that he has 

 definitely proved that this hypothesis of Zuntz is correct. He found 

 that these bacteria could form, not only from asparagine, but also 

 from ammonium tartrate, higher molecular nitrogenous substances which 

 in part resemble native protein, and in part peptone. The peptone 

 formation represented about 39 per cent, of the asparagine used, and the 

 active protein about 10 per cent. In the ammonium tartrate experi- 

 ment after twenty-four hours' incubation about 28 percent, of the total 



