190 TYROSIN. 



The classical researches of Bunge and Schmiedeberg 1 have shown 

 that the synthetic production of hippuric acid by the union of benzoic 

 acid and glycin takes place chiefly in the kidney of carnivora (dogs). 

 In herbivora (rabbits) it appears that a considerable formation of 

 hippuric acid may be observed on the ingestion of benzoic acid even 

 after exclusion of the kidneys 2 , and the same is the case with frogs. 

 Pathological observations on man seem to indicate that in them the 

 kidneys play at least some part in the synthetic production of hippuric 

 acid from benzoic 3 . When benzoic acid is administered to birds it 

 reappears in the excreta as ornithuric acid : the latter when boiled 

 with hydrochloric acid splits up into benzoic acid and ornithin, the 

 latter having the composition of diamido-valerianic acid 4 . 



3. Tyrosin. C 9 H n NO 3 . [OH . C 6 H 4 . CH 2 . CH . (NH a ) . COOH.] 

 Para-oxyphenyl-a-amidopropionic acid. 



The earlier work on the synthesis of tyrosin indicated the probable 

 presence in its molecule of some aromatic (phenyl) radicle. The more 

 recent successful synthesis by the action of nitrous acid on para-am ido- 

 phenyl alanin 5 has confirmed this view and definitely established its 

 constitution 6 . It always accompanies leucin, though less in amount, as 

 a product of the pancreatic digestion of proteids, but not of gelatin, 

 also as a product of their putrefactive decomposition as well as of the 

 action of boiling mineral acids and alkalis. It is also perhaps found 

 normally in small quantities in the pancreas and its secretion and in 

 the spleen, and traces have been described as obtained from various 

 tissues of the body 7 . It is normally absent in urine but makes its 

 appearance together with leucin in this excretion in several diseased 

 conditions of the liver, notably acute yellow atrophy, also in phos- 

 phorus poisoning; there is however some conflict of opinion as to its 

 constancy in such cases. It is also present in not inconsiderable 

 quantities, along with leucin, in many plant tissues. 



Tyrosin crystallises in exceedingly fine needles which are usually 

 collected into feathery masses. The crystals are snow-white, tasteless 

 and odourless. If crystallised from an alkaline solution tyrosin often 

 assumes the form of rosettes composed of fine needles arranged 

 radiately. 



1 Arch. f. exp. Path. u. Pharm. Bd. vi. (1876), S. 233. Cf. Schmiedeberg, Ibid. 

 Bd. xiv. (1881), Sn. 288, 379. See also Hoffmann, A, Ibid. Bd. vn. (1877), S. 233. 



2 Salomon, Zt. f. physiol. Chem. Bd. in. (1879), S. 365. 



3 Jaarsveld u. Stokvis, Arch. f. exp. Path. u. Pharm. Bd. x. (1879), S. 268. 



4 Jaffe, Ber. d. d. chem. Gesell. 1877, S. 1925 ; 1878, S. 406. 



5 Alanin is a-amidopropionic acid ; CH 3 . CH (NH 2 ) . COOH. 



6 Erlenmeyer u. Lipp., Ber. d. d. chem. Gesell. 1882, S. 1544. Liebig's Annal. 

 Bd. 219 (1883), S. 161. 



v. Gorup-Besanez, Lehrb. d. physiol. Chem. Ed. iv. 1878, pp. 225, 227. 



