7 6 



PHYSIOLOGICAL CHEMISTRY. 



metabolic activities of the animal body arginine gives rise to urea. 

 While this claim is probably true, it should, at the same time, be 

 borne in mind that the greater part of the protein nitrogen is 

 eliminated as urea and that, therefore, but a very small part can 

 arise from arginine. 



Leucine, C 6 H 13 NO 2 . Leucine is an abundant end-product of 

 the decomposition of protein material, and, together with glycocoll, 

 was the first of these products to be discovered (1820). It is 

 a-amino-isobutyl-acetic acid, and therefore has the following for- 

 mula: 



GIL 



NIL 



CH-CHo-C 



H. 



CH-C-COOH. 

 H 



The leucine which results from protein decomposition is /-leucine. 

 Leucine is present normally in the pancreas, thymus, thyroid, spleen, 

 brain, liver, kidneys and salivary glands. It has been found patho- 

 logically in the urine (in acute yellow atrophy of the liver, in acute 

 phosphorus poisoning and in severe cases of typhoid fever and 

 smallpox), and in the liver, blood and pus. 



FIG. 26. 



LEUCINE. 



Pure leucine crystallizes in thin, white hexagonal plates. Crystals 

 of pure leucine are reproduced in Fig. 26. It is rather easily soluble 

 in water (46 parts), alkalis, ammonia and acids. On rapid heating 



