CHEMICAL BASIS OF THE ANIMAL BODY. 909 



THE AROMATIC SERIES. 

 Benzole Acid. HC 7 H 5 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 ben- 

 zoic acid are formed : 



Hippuric acid. Glycin. Benzoic acid. 



C 2 H 4 (C 7 H 5 0)N0 2 + H 2 - C 2 H 5 N0 2 + C 7 H 6 2 . 



The sublimed acid is generally crystallized in fine needles, which are light and 

 glistening ; any odor they possess is not due to the acid, but to an essential oil. with 

 which they are mixed. \Vhen 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 ether. It sublimes readily at 145 C. ; it also 

 passes off in the vapors arising from its heated solutions. 



Preparation. Either as above from hippuric acid by fermentation, by boiling 

 the hippuric acid with acids or alkalies, or by sublimation from gum-benzoin. 



Tyrosin. C 9 H U N0 3 . 



Generally accompanies leucin, and is perhaps found normally in small quan- 

 tities 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 Radziejewski* render it probable that tyrqsin does not occur normally in 

 any part of the human organism, except as a product of pancreatic digestion. 



All attempts to synthetize tyrosin were for some time fruitless, although evi- 

 dence 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-phenyl a 

 alanine. This synthesis, as well as that of uric acid, referred to above, is of con- 

 siderable 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 realizable 

 in the not very remote future. 



[Fie. 254. 



Tyrosin Crystals.] 



Tyrosin crystallizes in exceedingly fine needles which are usually collected into 

 feathery masses [Fig. 254]. The crystals are snow-white, tasteless and odorless, 

 almost insoluble in cold water, readily soluble in hot water, acids, and alkalies, 



1 Archiv. f. path. Anat., Bd. xxxvi., S. 1. Zeitschr. f. anal. Chem., Bd. v., S. 466. 



2 Earth., Chem. Centralbl., 1865, S. 1029; 1869, S. 761; 1872, S. 830. Hufner, Ibid., 1869, S. 139. 

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



3 Erlenmeyer u. Lipp., Ber. d. Deutsch. Chem. Gesell., Jahrg. xv. (1882), S. 1544. 



