DECOMPOSITION OF THE ALBUMINS. 37 



presence of acetic acid. This test is quite commonly used for the 

 purpose of demonstrating the presence of albumin in the urine. 



7. Trichloracetic acid in 2 to 5 per cent, solution is now extensively 

 used for the purpose of testing for certain albumins, notably serum- 

 albumin, but it does not cause complete precipitation of all forms of 

 albumin. 



Decomposition of the Albumins. With the view of gain- 

 ing an insight into the structural composition of the albuminous 

 molecule, a careful study of the decomposition-products of the 

 various albumins has long occupied the attention of investigators. 

 These products vary somewhat with the method of decomposition 

 which is employed, but there are certain ones which are almost con- 

 stantly met with, and which hence may be regarded as essential 

 constituents. Especially important among these are certain amido- 

 acids, such as tyrosin, leucin, asparaginic acid, glutamiuic acid, and 

 glycocoll. These are formed from the native albumins, no matter 

 whether their decomposition has been effected by superheated steam, 

 by boiling with acids or alkalies, or by means of the so-called pro- 

 teolytic ferments. The nitrogen which is thus split off is spoken of 

 as rnono-ammo-nitrogen. At the same time another portion is 

 liberated in the form of ammonia, the so-called amido-nitrogen. As 

 tyrosin is an amido-acid of the aromatic series, viz., para-oxyphenyl- 

 amido-propionic acid, while leucin, -isobutyl-acetic acid, glycocoll or 

 amido-acetic acid, as also asparaginic acid and glutaminic acid, viz., 

 amido-succinic acid, and amido-glutaric acid, respectively, belong to 

 the fatty series, we may conclude that the albuminous molecule con- 

 tains aromatic as well as fatty acid radicles. In accordance with 

 this view, we find that all albumins which yield tyrosin on tryptic 

 digestion also give Millon's reaction, and we know, furthermore, 

 that the amide of asparaginic acid, asparagin, as also glutamin, the 

 amide of glutaminic acid, occur widely distributed in the vegetable 

 world. Glutaminic acid itself is obtained, together with asparaginic 

 acid, when albuminous substances are boiled with dilute mineral 

 acids. At the same time, two basic substances may be obtained, 

 which Drechsel has termed lysatin and lysatinin, and which are 

 apparently homologous with two other bodies which occur widely 

 distributed in the animal world, namely, kreatin and kreatinin. 

 Lysatin and lysatinin, moreover, like kreatin and kreatinin, yield 

 urea among their products of decomposition, which shows that this 

 body, which represents the final product of the normal metabolism 

 in mammals, can result directly from the original albuminous mole- 

 cule through a simple process of hydrolysis, and may possibly exist 

 in it as such. 



Other decomposition-products which may be obtained apparently 

 from all true albumins are the three hexon bases, argimn, lysin, 

 and histidin. These substances in turn are derived from certain 

 protamins, and Kossel claims that a protamin radicle is present 

 in all albumins, and gives rise to the violet biuret reaction. The 



