1882.] Leucine and Glycocine into Urea. 181 



(OH 



H.CHO + HCN= CH_ 



{1 



rnethene cyanhydrin 



OH s {^ + NH a - CH,{^ + H 2 



methene cyanaraide 



OH,{™. + 2H,0 = CH,{^ H + NH. 



glycocine 



These changes, I think, exemplify very well the way in which 

 the wants of the system are supplied ; nitrogen appearing in the 

 formulas as ammonia, NH„, when it is the result of disintegra- 

 tion of tissue, and as a cyanide, or nitrile, when required for the 

 formation of a tissue. For instance, in the series of changes given 

 for the formation of alanine, if ethidene cyanhydrin were decom- 

 posed without comiug in contact with NH 3 , it would itself at once 

 be transformed into ammonia and lactic acid — 



CH 3 . CH j°* + 2H 2 = CH 3 .CH i™ H + NH 3 



ethidene cyanhydrin lactic acid 



the lactic acid being by oxidation converted into carbonic acid and 

 water. 



CH 3 . CH {cq OH + 30 2 = 3C0 2 + 3H 2 



lactic acid 



the ammonia combining with a urethane to form urea and an 

 alcohol. 



Or the lactic acid may pass through the intermediate stages of 

 (i) formic acid and acetic acid, (ii) aldehyde and carbonic acid, or 

 (iii) oxalic acid — - 



CH 3 . CH {^ TT + = H . COOH + CH 3 . COOH 

 3 (COOH 



lactic acid formic acid acetic acid 



