CHEMICAL BASIS OF THE ANIMAL BODY. 161 



reactions which are strictly analogous to the formation of acetamide 

 CH 3 . CO (NH 2 ) by the action of ammonia on acetyl chloride CH 3 . COC1, 

 and on ethyl-acetate CH 3 . COO (C 2 H 5 ). 



It is interesting to observe here that acetamide yields methylcyanide by treatment 

 with phosphorous pentoxide : CH 3 . CO (NH 2 ) = CH 3 . CN + H 2 0. 



Acetamide is also formed by the dry distillation of ammonium 

 acetate, the change being one of simple dehydration ; and this reaction 

 is one of general applicability, amides being formed by the removal of 

 one molecule of water from the ammonium salt of a monobasic acid or 

 of two molecules of water from that of a dibasic acid, e.g. ammonium 

 oxalate yields oxamide. Now although urea has not been formed by the 

 dehydration of ammonium carbonate, it is readily rehydrated into the 

 carbonate by the action of acids, alkalis, superheated water, or the urea 

 ferment. Further if instead of operating on ammonium carbonate, the 

 ammonium salt of carbamic acid (see p. 152) be heated in sealed tubes 

 to 140, or if it be electrolysed with a rapidly commutated current, 

 it loses a molecule of water and is converted into urea. 



When the purely chemical facts above stated are applied to the 

 formation of urea in the animal body it is at once obvious that urea 

 might originate from some cyanic source, or from a simple dehydration 

 of ammonium carbonate or carbamate. A full discussion of the 

 possibilities thus indicated lies outside the scope of this work, but it 

 may not be out of place to indicate, as briefly as may be, the various 

 views which have been put forward concerning the probable way in 

 which urea originates in the body 1 . 



There is little reason for doubting that the larger part of the 

 nitrogen which leaves the body as urea was at one time a constituent 

 of the nitrogenous muscle-substance (see 484). There is equally no 

 doubt both from general considerations and from the fact that no urea 

 can ever be detected in muscles normally, that the nitrogen does not 

 make its exit from the muscles as ready-made urea. Neither until 

 recently had urea been obtained by any purely chemical means from 

 the products of the decomposition of proteids. 



The older statements of Bechamp and Bitter that urea may be obtained from 

 proteids by the action of potassium permanganate have been shown to be erroneous". 

 It is at most possible that a trace of guanidin may be formed, and guanidin can by 

 the action of water be converted into urea and ammonia : NH . C (NH 2 ) 2 + H 2 = 

 (NH 2 ) 2 CO + NH 3 . 3 Drechsel has however obtained from among the products of 



1 The literature of the subject is very fully quoted in Bunge's PJiysioL and 

 pathol. Chemistry, 1890. Lecture xvi. pp. 310-348. 



2 Loew, Jn. f.prakt. Chem. (2) Bd. n. (1870). S. 289. Tappeiner, Ron. sachs. 

 Gesell. d. Wiss. 1871. See Abst. in Maly's Bericht, 1871, S. 11. 



3 Lessen, Ann. d. Chem. u. Pharm. Bd. cci. (1880), S. 369. 



F. I 



