ix THE HISTONES 409 



Reactions of Histories (Nos. 1 to 5 after Bang) 



1. Histones are precipitated from their watery solutions by 

 ammonia. This reaction is the most important, for it led originally 

 to the discovery of the histones. 1 According to v. Fiirth 2 myogen 

 (Halliburton's myosinogen) is also precipitated by ammonia, and the 

 acid-albumins behave similarly (Bang), but the precipitates of these 

 substances redissolve in the slightest excess of ammonia, and the 

 precipitation is never complete, while in histone- solutions ammonia 

 produces an abundant heavy precipitate. In excess of ammonia the 

 histones are soluble, and they are even more readily dissolved by an 

 excess of free alkali. The amount of ammonia required to precipitate 

 histones and to redissolve the precipitate differs for the individual 

 histones. The thymus-histone and that prepared from the mackerel 

 is only completely precipitated by ammonia, according to Bang, if 

 salts are also present. Bang's statements regarding the other histones 

 are not correct and are also not quite accurate regarding the thymus- 

 histone (Cohnheim). 



2; Histones are coagulated by boiling only in the presence of 

 salts, and even then not completely, for if the precipitates be dissolved 

 in acids and be then neutralised they remain in solution, showing that 

 they were not converted into acid-albumin, and for the same reason 

 they are again precipitated on being heated. It is at present im- 

 possible to say in how far histones differ in this respect from other 

 albumins and what part is played by the amount of acid or base 

 present. 



3. With nitric acid histones give a precipitate in the cold, which 

 dissolves on heating and reappears on cooling. Therefore they give 

 the reaction which is generally said to be typical of albumoses, and 

 Kossel for this reason classed histones originally amongst the 

 albumoses. 



4. While the other albumins are only precipitated by the so-called 

 alkaloidal reagents if the reaction be acid, histones are precipitated 

 from neutral solutions. 3 They are, therefore, precipitated by sodium 

 phosphotungstate or molybdate, sodium picrate, or potassium ferro- 

 cyanide; globin is dissolved by an excess of the reagent, probably 

 because the reaction of the solution becomes alkaline. The histone 



1 A. Kossel, ibid. 8. 511 (1884) ; 32. 81 (1901). 



2 0. v. Fiirth, Arch. f. experim. Path. u. Pharmak. 36. 231 (1895). 



3 A. Kossel, Zeitschr. /. physiol. Chem. 25. 165 (1898) ; Kossel and F. Kutscher, 

 ibid. 31. 165 (1900) ; A. Mathews, i6id. 23. 399 (1897) ; J. Bang, ibid. 27. 463 

 (1899) ; 32. 79 (1900). 



