APP.] CHEMICAL BASIS OF THE ANIMAL BODY. 759 



THE AROMATIC SERIES. 



Benzole acid. HC 7 F 5 O 2 . 



This is not found as a normal constituent of the body, but owes its 

 presence in. urine to the fermentative decomposition of hippuric acid, 

 whereby glycin and benzoic acid are formed : 



Hippuric acid. Glycin. Benzoic acid. 



C, H 4 (C 7 H 5 O) N0 2 + H 2 - a H 3 K0 2 + C 7 H 6 O 2 . 



The sublimed acid is generally crystallised in fine needles, which are 

 light and glistening ; any odour they possess is not due to the acid, but 

 to an essential oil, with which they are mixed. When precipitated from 

 solution, the crystalline form is always indistinct. This acid is soluble 

 in 200 parts cold, or 25 parts of boiling water, but is easily soluble 

 in alcohol or aether. It sublimes readily at 145 C. ; it also passes off 

 in the vapours arising from its heated solutions. 



Preparation. Either as above from hippuric acid by fermentation, 

 by boiling the hippuric acid with acids or alkalis or by sublimation from 

 gum-benzoin. 



Ty rosin. C 9 H n N0 3 . 



Generally accompanies leucin, and is perhaps found normally in small 

 quantities in the pancreas and spleen. It is also usually obtained in 

 large quantities by the decomposition of proteid matter, either by 

 putrefaction or the action of acids. 



The researches of Kadziejewsky 1 render it probable that tyrosin does not occur 

 normally in any part of the human organism, except as a product of pancreatic 

 digestion. 



All attempts to synthetise tyrosin were for some time fruitless, 

 although evidence was obtained sufficient to indicate the probable 

 existence in its molecule of some aromatic (phenyl) radicle 2 . More 

 recently the synthesis has been performed 3 , and we now have every 

 reason for regarding tyrosin as para-hydroxy-pheiiyl-a alanine. This 

 synthesis as well as that of uric acid, referred to above, is of considerable 

 importance, since the more definite the knowledge which is possessed 

 of the true molecular structure of the products of proteid decomposition 

 the more reason is there for expecting that the synthesis of a proteid 

 itself may be realisable in the not very remote future. 



1 Archiv. f. path. Anat. Bd. 36, S. 1. Zeitsch. f. anal. Ghent. Bd. 5, S. 466. 



2 Barth., Chum. Centralb. 1865. S. 1029. 1869. S. 761. 1872. S. 830. Hufner, 

 Ibid. 1869. S. 159. Beilstein u. Kiihlberg, Ibid. 1872, S. 830. 



3 Erlenmeyer u. Lipp., Per. d. deutsch. Chem. Gesell. Jahrg. XT. (1882), S. 1544. 



