410 CHEMISTRY OF THE PROTEIDS CHAP. 



prepared from the mackerel resembles the protamins in being precipi- 

 tated from feebly alkaline solutions. This characteristic reaction of 

 the histones depends on their basic character, which allows them 

 to become less strongly hydrolysed than other albumins. 



5. Neutral solutions of histone give a precipitate with solutions of 

 ov-albumin, casein, and serum-albumin, if these are poor in salts, and 

 also with egg-albumin and blood-serum. The precipitate contains 

 for one part of histone two parts of casein and serum-globulin, but 

 only one part of ovalbumin. The precipitate is soluble in acids and 

 alkalies, and is not precipitated by ammonia or other alkalies in the 

 presence of salts. 



The two reactions just mentioned, namely, the precipitation of 

 histones by alcaloidal reagents from neutral or alkaline solutions, and 

 the power of combining with albumins to form insoluble compounds, 

 are common to both the histones and the protamins, and also to some 

 albumoses, set free by peptic digestion from fibrin and certain other 

 albumins, according to the statements of Kutscher l and Bang. 



Histones have also the following reactions in common : 



6. They resemble acid - albumins by being precipitated from 

 alkaline, neutral and acid solutions by the addition of small amounts 

 of salts (Bang, Huiskamp). 2 



7. Their sulphur content is low, while in accordance with their 

 basic nature their nitrogen-percentage is high. 



In other respects histones give, like other albumins, the usual pre- 

 cipitation-tests. Ether, even when added in small amounts, leads to 

 the histone separating out as a buoyant mass, swimming on the surface 

 of the layer of ether. 3 The salting-out limits, the colour-reactions, 

 the dissociation-products, and the readiness with which dissociation 

 is brought about differ greatly with each individual histone. As 

 already mentioned, the sulphur is low in amount, and the lead- 

 sulphide reaction may give negative results. Finally it is of great 

 interest that Kossel, 4 by combining protamin and albumin, obtained 

 precipitates which possessed all the properties of the histones. 



1. The Thymus-histone 



Lilienf eld 5 first prepared a nucleo-albumin, which he called ' nucleo- 

 histone,' by adding acetic acid to a watery extract of the thymus 



1 F. Kutscher, Zeitschr. f. physiol. Chem. 23. 115 (1897). 



2 W. Huiskamp, ibid. 32. 145 (1901) ; 34. 32 (1901). 



3 E. Ehrstrora, ibid. 32. 350 (1901). 



4 A. Kossel, Deutsche med. Wochenschr. 1894, p. 146 ; Zeitschr. /. physiol. Chew. 

 22. 176 (1896). 5 L. Lilienfeld, ibid. 18. 473 (1893). 



