CHEMICAL EXAMINATION OF THE BLOOD. 341 



uents of blood, such as leucin, ty rosin, acetone, bilirubin, etc., have 

 been considered in preceding chapters. 



Of gases, finally, we find in the plasma and serum small amounts 

 of nitrogen and oxygen, which are present simply in solution, and 

 somewhat larger amounts of carbon dioxide, which in part at least 

 is more or less firmly combined with albumins. 



The Leucocytes. 



The morphological characteristics and general chemical composi- 

 tion of the leucocytes have already been considered (see pages 326 

 and 329). At this place I wish merely to draw attention to one 

 substance which, according to Lilienfeld, is found in special 

 abundance in the nuclei of these bodies, and which has been termed 

 nucleohiston. 



Nucleohiston. This substance was first isolated by Kossel and 

 Lilienfeld from the thymus gland of the calf, but has since been 

 obtained from the leucocytes of the lymph-glands, as also from the 

 splenic cells, the testicular cells, the spermatozoa, and from the 

 epithelial lining of the small intestine. In all probability it repre- 

 sents an important constituent of all cellular nuclei. 



Isolation. Nucleohiston is most conveniently obtained from the 

 leucocytes of the thymus gland. To this end, the gland is carefully 

 dissected free from fat and all larger bloodvessels, and finely hashed. 

 This mass is extracted with cold water, passed through muslin, and 

 centrifugalized. The aqueous extract is further filtered, and the 

 nucleohiston precipitated by the careful addition of dilute acetic 

 acid. It is filtered off, dissolved in water with the aid of a small 

 amount of a dilute solution of sodium carbonate, reprecipitated 

 with acetic acid, and purified by a repetition of this process. It is 

 then washed with acetic water, extracted with alcohol and ether, 

 and finally dried at a temperature of from 110 to 115 C. Gam- 

 gee and Jones have pointed out that solutions of Lilienfeld's nucleo- 

 histon prepared in this manner are very opalescent, but that this 

 objection to the polarimetric examination can be removed by ex- 

 tracting the nucleohiston with a 5 per cent, solution of ammonium 

 acetate and filtering. The liquid filters very slowly, but steadily. 

 The proteid is then precipitated by pouring the solution into 95 per 

 cent, alcohol, after which it is washed and dried with alcohol and 

 ether. 



Properties. Thus obtained, nucleohiston represents a snowy- 

 white fine powder, which is insoluble in benzol, alcohol, chloro- 

 form, methyl alcohol, ether, and acetic acid, but is soluble in water, 

 glacial acetic acid, concentrated nitric acid, and hydrochloric acid, 

 in solutions of sodium carbonate, sodium hydrate, ammonia, and, 

 when freshly precipitated, also in solutions of sodium chloride and 

 magnesium sulphate, especially in the presence of a little acetic acid. 

 It has the properties of an acid salt, and on boiling with water or on 



