234 LECTURE XI 



We will only refer here to these interesting investigations, and await 

 further developments. 



We must also consider Hofmeister's hypothesis and its claims. Hof- 

 meister succeeded first of all in producing urea by the oxidation of albu- 

 min, and then also of amino acids, in the presence of ammonia. From 10 

 grams glycocoll he obtained 3 grams urea. The assumption of an oxidizing 

 synthesis in the formation of urea has much in its favor. On the one 

 hand, the conditions in the animal organism are very favorable for such a 

 production of urea from amino acids; and then again, the whole process 

 harmonizes very well with our conception of the degradation of the proteins. 

 The hypothesis, however, has not yet been proved. 



If we take everything that we know about the formation of urea in the 

 animal organism, into consideration, we can conclude that a part of urea 

 is directly produced by the hydrolytic cleavage of albumin, the amount 

 depending on the nature of the latter. Arginine is the only source so far 

 known for this process. This does not, however, exclude the possibility 

 that other analogous complexes to that of this amino acid may be present 

 among the as yet unknown elementary constituents of albumin. We 

 also know that amino acids and polypeptides, when incorporated in the 

 animal organism, go over into urea. We do not, however, know the manner 

 in which this further decomposition is accomplished. It is not impossible 

 that the anhydride formation, or the oxidizing synthesis, plays an impor- 

 tant part. Both assumptions are supported by experimental evidence. As 

 far as the place of formation of the urea is concerned, we are certain that 

 the liver produces it. We do not know whether other organs also par- 

 ticipate in its formation. 



It has been desired to draw definite conclusions from the presence of the 

 following compounds in the urine. If we administer aminobenzoic acid 

 to the animal organism we will find carbaminobenzoic acid in the urine: 



NH 2 . C 6 H 4 . COOH --> NH 2 . CO . NH . C 6 H 4 . COOH. 1 



After the administration of ethylamine (carbona-te) we find ethylurea: 

 C 2 H 5 NH 2 -* C 2 H 5 . NH . CO . NH 2 . 2 



Taurine, under analogous conditions, goes over into carbaminoisethionic 

 acid, sulphanilic acid into sulphanilcarbamic acid, and o- and p-amino-sal- 

 icylic acid into the corresponding carb amino acids. 



We can easily imagine a conjugation of urea with the compounds in 

 question, and ascribe an analogous role to it, as to glycocoll, sulphuric 



1 E. Salkowski: Z. physiol. Chem. 7, 93 (1883-83). Cf. also R. Cohn: ibid. 17, 274, 

 292 (1893). 



2 O. Schmiedeberg: Arch. exp. Path. Pharm. 8, 1 (1877). 



