Chemical Changes in Animal Organism. 307 



rnent of this sugar with weak solutions of caustic alkali, 

 this acid is produced in appreciable quantities. The 

 exact mechanism of the formation is unknown, but it is 

 lighly probable that it is also an intermediary degrada- 

 tion product produced from dextrose in certain biologi- 

 cal processes. The interest of Embden's observation lies 

 in the fact that an ammo-acid can be synthesized from 

 ammonia and a degradation product of a sugar. By the 

 conjugation of amino-acids protein-like substances can be 

 produced. The production of alanine from ammonium 

 actate may be regarded, therefore, as a stage in the 

 synthesis of a protein from carbohydrates. This observa- 

 tion of the formation of alanine from ammonium lactate 

 is, however, of too isolated a character to permit of any 

 useful speculations as to the mode of synthesis of proteins 

 in the animal body. 



The number of experiments by the perfusion method 

 is somewhat limited. The complexity of the apparatus, 

 which is not available in all laboratories, and the chemical 

 difficulties of separating small amounts of the reaction 

 products from large quantities of blood, probably account 

 for this fact. 



(C) METHOD BY ADMINISTRATION TO ANIMALS OF INTER- 

 MEDIARY PRODUCTS OF METABOLISM. 



Some intermediary products of metabolism are known. 

 Thus, for example, it is an established fact that peptones 

 and amino-acids are produced from proteins by the action 

 of proteoclastic ferments in the alimentary tract. It is 

 conceivable that information as to the subsequent fate of 

 such intermediary products could be obtained by the direct 

 administration of these to animals, and by attempting to 

 isolate the end products of their metabolism from the 

 urine. Such a direct method of experiment does not 



