THE NATIVE ALBUMINS. 51 



The Histons. Although the histons do not occur in the animal 

 body independently, but in combination with certain prosthetic 

 groups, such as hsematin (in hemoglobin) and nucleinic acid (cer- 

 tain nucleoproteids), they are considered here nevertheless, as they 

 are well-defined bodies which are capable of isolation from their 

 pairlings as such. They comprise the common histon of the thymus, 

 the lymph-glands, and the spleen, the histon of the red corpuscles 

 of the goose, the salmon and scombron from the testicles of the sal- 

 ra >n and herring respectively, arbacin from the spermatozoa of 

 Arbacia pustulosa, the lota histon and gadus histon, Fleroff 's para- 

 histon and globin, the albuminous radicle of hemoglobin. 



According to Kossel, the histons are compounds of protamins and 

 albumins, and as a matter of fact compounds of this order result 

 artificially on treating solutions of albumins with protamins. The 

 histons are in turn capable of uniting with albumins, and may ac- 

 cordingly be viewed as non-saturated compound albumins. 



There are many points of similarity between the histons and the 

 protamins (see below). Both are markedly basic substances, which 

 combine with acids to form salts. Both form precipitates with the true 

 albumins. Both are precipitated by the alkaloidal reagents, in neu- 

 tral or alkaline media. Protamins and histons are both rich in 

 basic radicles (diamido-acids) ; the histons yield 40 per cent, and 

 more on hydrolysis, and the protamins from 68 to 88 per cent. With 

 the exception of cyclopterin the protamins do not give Millon's reac- 

 tion and the histons only feebly. 



Histons and protamins frequently replace each other; immature 

 fish sperm thus contains nucleinate of histon, while in the mature 

 material the corresponding protamin salt is found. It may, how- 

 ever, persist as such. 



The elementary composition of the histons is different in different 

 members of the group. Common to all is a large amount of nitro- 

 gen. In the best known representative of the group, the thymus 

 histon, elementary analysis has given the following results : C == 

 52.35 ; H = 7.5 ; N = 18.1 ; and S = 0.62. Its elementary formula, 

 according to Bang, is C 273 H 459 N 81 SO 84 . 



The histons all gave a violet biuret reaction and the xanthopro- 

 teic reaction, while Millon's reaction is feeble and Molisch's reaction 

 absent. 



The histons are soluble in water, but are precipitated on the addi- 

 tion of a very small amount of ammonia (feebly but distinctly alka- 

 line reaction). In the presence of an excess, even if slight, they are 

 again dissolved, unless an ammonium salt is present, in which case 

 they are completely or almost completely insoluble in an excess of 

 the reagent. This reaction is very characteristic, but not altogether 

 diagnostic ; parahiston does not give it, arbacin only incompletely 

 so, and in the case of scombron redissolution does not occur even 

 though ammonium salts be absent. 



On boiling a solution of histon in the absence of salts coagulation 



