202 THE PRODUCTS OF ALBUMINOUS DIGESTION. 



ammonium sulphate in substance. On cooling, any albumoses that 

 may have separated out, together with a large quantity of the salt, are 

 filtered off. The filtrate is heated, and, while boiling, rendered strongly 

 alkaline with ammonia and ammonium carbonate, and again saturated 

 with ammonium sulphate. On cooling, a second fraction of albu- 

 moses is filtered off. The solution is then heated until the odor of 

 ammonia has disappeared; ammonium sulphate is again added to 

 saturation, and the liquid rendered distinctly acid with acetic acid, 

 when on cooling a third fraction of albumoses separates out and is 

 filtered off. The filtrate is concentrated to about one liter and freed 

 from a large amount of ammonium sulphate, which separates out on 

 cooling. It is then diluted with water to about 3000 c.c., and treated 

 at a temperature of 30 C. with barium hydrate in substance, to re 

 move the remaining salt. A slight excess of the barium is removed 

 with carbonic acid, and is filtered off after boiling for a moment. The 

 filtrate is evaporated to about 1000 c.c., when the barium peptone is 

 decomposed with dilute sulphuric acid, care being taken that the 

 acid is not added in excess. The resulting barium sulphate 

 is filtered off and the filtrate concentrated to a thin syrup. On cool- 

 ing, absolute alcohol is added until the turbidity that first appears 

 no longer disappears on stirring. After filtering with the aid of a 

 suction pump, the solution is poured into absolute alcohol while 

 stirring. The antipeptone is then precipitated and allowed to settle, 

 when the supernatant fluid is siphoned off and the antipeptone col- 

 lected on a filter with the aid of a suction-pump. It is finally 

 washed with absolute alcohol, then with ether, and rapidly placed in 

 a desiccator over sulphuric acid. 



From this material arginin, lysin, and histidin may be isolated, 

 as described by Kutscher (Zeit. f. phys. Chem., 1898, vol. xxvi., 

 p. 110). 



The Mono-amino-acids. To study the mono-amino-acids the 

 antipeptone fraction need not be removed. 1 



Leucin. Aside from its formation during the process of pan- 

 creatic digestion or on artificial decomposition of albumin with dilute 

 mineral acids and alkalies, leucin has been demonstrated in the 

 spleen, in the lymph-glands, in the thyroid, the kidneys, the liver, 

 and the brain, though mostly under pathological conditions, when it 

 may also appear in the urine. It is further found in sheep's wool, 

 in decomposing epithelial structures, as in the desquamated material 

 which is found between the toes, etc. It is also formed as the result 

 of bacterial action upon albuminous material. 



In pure form leucin crystallizes in extremely thin white lustrous 

 platelets; but more commonly it is seen in the form of spherules of 

 variable size, which closely resemble globules of fat. In these, con- 

 centric striations, as well as very fine radiating lines, can at times be 

 made out on careful examination. 



1 For the isolation of the various mono-amino-acids, according to E. Fischer's method, 

 see Zeit. f. phys. Chem., 1901, vol. xxxiii., p. 151. 



