246 TYROSINE. [BOOK n. 



newly-separated ' reticulin ') we find leucine amongst the products of 

 decomposition, though how greatly the yield of leucine may vary is 

 stated at page 237. Tyrosine stands in this respect in a different 

 relation to leucine, in that some of the derivatives of albumin do not 

 yield it. The first example in illustration of such bodies is offered by 

 gelatin. When long boiled with dilute sulphuric acid, it yields large 

 quantities of amido-acetic acid, or glycocoll (C 2 H 5 NO 2 = CH 2 (NH 2 ) 

 COOH), an amido-acid which is not, in general, yielded by a similar 

 treatment of proteids, or their derivatives and inter alia, it yields 

 about 1*5 per cent, of leucine (Nencki). From gelatin, however, we 

 can obtain no trace of tyrosine. Under the influence of putrefactive 

 bacteria gelatin again yields glycocoll and leucine but neither tyro- 

 sine nor indol. Gelatin, it may be noted in this connection, does not, 

 when pure, exhibit Millon's reaction. This reaction, which is fur- 

 nished by all the albuminous bodies proper and by nearly all their 

 immediate allies the albuminoid bodies, which are capable of 

 yielding tyrosine, is identical with Hoffmann's tyrosine-reaction. 

 It has already been stated (p. 228) that whilst solutions of ampho- 

 peptones give, in a characteristic manner, Millon's reaction, pure 

 antipeptone fails to do so ; in accordance with this fact, which they 

 discovered, Ktihne and Chittenden found that by long boiling with 

 dilute sulphuric acid, antipeptone yields no tyrosine. 



Quantities of From horn, Stadeler obtained 4 per cent, of its 



tyrosine ob- we ^} lt o f tyrosine. Ellenmeyer and Schoffer obtained 



tained from al- f -, J , Z.AOC ? 



buminous and "' om H0OMMM& nuchae 0'25 per cent.: from horn 3*6 per 



albuminoid cent. : from blood-fibrin 2'0 per cent. : from egg-albumin 



bodies. I'O per cent. 



Schiitzenberger by the action of barium hydrate, at temperatures 

 from 160 200 C., for a period of from 4 to 6 days, obtained 

 from blood-albumin and vegetable-fibrin 2 per cent. : from blood- 

 fibrin 3'3 per cent. : from casein 4'1 per cent, of tyrosine 1 . 



Quantities of I n the paper in which Kiihne first announced his 

 tyrosine (as di scover y O f the profound decomposition which the 

 cine) obtained P r teid molecule undergoes under the influence of the 

 by digestion of proteolytic enzyme of the pancreas, he gave details of 

 fibrin by tryp- an experiment which furnishes some idea of the quan- 

 sin - tities of leucine and tyrosine obtained by the digestion 



of blood-fibrin. 



The fibrin had been thoroughly boiled, and then freed mechani- 

 cally from much of its adherent moisture. The amount subjected 

 to digestion was equivalent to 382 grammes of dry fibrin. It was 

 suspended in 6 litres of water at 40 48, and to it was added 

 55 grammes of minced pancreas, corresponding to 15*2 grammes of 

 dried gland. After a digestion lasting 6 hours, 16'0 grammes of 



1 All the data given under this head are taken from Maly, Hermann's Handbuch, 

 Vol. v. n. pp. 218 and 219. 



