436 CSEMISTBT OF THE LEUCOMAINS. 



tions, free from salts of ammonia, are precipitated by ammonia, but 

 the precipitate redissolves in excess of the reagent. The scombron 

 precipitate however does not redissolve. In the presence of ammonia 

 salts the precipitate induced by ammonia is permanent. As pointed 

 out by Bang the acid albuminates and vitellin are likewise precipitated 

 by ammonia. The fixed alkalis also precipitate histon. While pure 

 solutions of histon are not coagulated on boiling this does occur in 

 the presence of a small amount of salt. As Kossel first showed 

 histon may be precipitated from acid solution by saturation with 

 sodium chlorid or other salts. With nitric acid the histons give 

 the albumose reaction ; likewise the xanthoproteic reaction. The 

 biuret test is given by all. With Millon's reagent the reaction is 

 slight but distinct. Salts of mercury precipitate some histons, but 

 not others. The most important reaction is based upon the fact that 

 while ordinary proteids are precipitated by certain alkaloidal reagents 

 in acid but not in neutral solution, the histons like protamins, be- 

 cause of their pronounced basic character, are precipitated by these 

 reagents from neutral as well as acid solutions. Sodium ferrocy- 

 anid, picrate, phosphotungstate and phosphomolybdate can be 

 thus used. Again, like the protamins, histon precipitates proteids, 

 provided free alkali is not present in excess. This property is like- 

 wise seen in the marked agglutinating action which histon exerts on 

 bacteria. On digestion with pepsin thymus histon is split up and a 

 protamin-like body results (Bang). 



The physiological action of histon is very similar to that of prota- 

 min (p. 432). The action of thymus histon on toxins and on bac- 

 teria with special reference to immunity has been studied by Novy.' 



Histon may be prepared direct from the thymus gland.^ For this 

 purpose the gland is finely divided and extracted with water. To 

 the aqueous solution hydrochloric acid is added to 0.8 per cent, con- 

 centration. The resultant precipitate is removed by centrifugation 

 and from the clear filtrate the histon is thrown down by addition of 

 ammonia. The precipitate is washed with ammoniacal water, then 

 with alcohol and finally with ether. 



According to Fleroff^ the thymus gland on extraction with dilute 

 sulphuric acid, as in the method for protamins, yields histon and 

 para-histon. The latter is soluble in ammonia and water and is thus 

 separated from histon. For the separation of histon from sperma- 

 tozoa, see Kossel {Z. P. C, 31, 192); from hemoglobin, see Schulz 

 (Z. P. C, 24, 456). 



Arginin, C^Hj^N^Oj . — The study of the constitution of this base 

 has revealed several important facts which enable us to explain sat- 

 isfactorily a number of vital reactions. The observation of Drech- 



i/oitra. Exp. Med., 1, 709, 1896. 

 'Zeits. physiol. Chem., 31, 189 ; 28, 388. 

 "ZeUs. physiol Chem., 28, 307. 



