x THE NUCLEO-PROTEIDS 449 



The nucleic acid is linked to the albumin in the following 

 manner : According to Lilienfeld, 1 O'S per cent hydrochloric acid 

 liberates the basic histone from the nucleo-histone, which is a nucleo- 

 proteid of the thymus, and therefore nucleo-histone may be regarded 

 simply as a salt ; but Huiskamp 2 on electrolysing a solution of sodium 

 nucleo-histone, found that it gave rise to the ions : nucleo-histone and 

 sodium, and not to nucleic acid and historic. Cohnheim believes this 

 dissociation (nucleic) to speak against the existence of acid histone- 

 nucleates. In other nucleo-proteids, as, for example, in that of the 

 pancreas, which has been investigated very fully, a dissociation by 

 acids analogous to that occurring with the nucleo-histone of the 

 thymus cannot be observed, for the pancreas nucleo-proteid 3 when 

 boiled in neutral solutions dissociates into albumin and nuclein, which 

 speaks strongly against a salt-like combination, according to Cohnheim. 



On dissociation taking place, nucleic acid is never split off from 

 the nucleo-proteid as a free acid, but as a nucleic-acid-compound 

 containing a certain amount of albumin. This albumin-nucleate is 

 known as nuclein. Nucleic acid would therefore appear to be 

 linked to two albumin-radicals, one of which is readily split off while 

 the other is firmly adherent. Lilienfeld 4 has expressed this by the 

 following scheme : 



Nucleo-proteid 



albumin nuclein 



(histone) >X x s s ^ 



albumin nucleic acid. 



It must, however, be pointed out that nucleins are still more difficult 

 to prepare in a pure state than are the nucleo-proteids, and that 

 therefore it is still easier to get mixtures of substances and artefacts. 5 

 Nucleo-proteids in a pure state resemble other albumins in forming 

 loose, white, non-hygroscopic powders ; as they do not occur in 

 solution, but only as cell-constituents, it is difficult to say in how far 

 we are acquainted with their natural properties, and to what extent 

 they have been altered by the process of isolating them. They 

 are all markedly acid, are soluble in water and in salt solutions, and 

 still more soluble in alkalies. They are precipitated by acids, but with 



1 L. Lilienfeld, Zeitschr. f. physiol. Chem. 18. 473 (1893). 



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



3 F. Umber, Zeitschr. f. klin. Med. 40. Hefte 5 and 6 (1900). 



4 L. Lilienfeld, Arch. f. (Anat. u.) Physiol. 1892, p. 128. 



5 F. Umber, Zeitschr. f. klin. Med. 43. Hefte 3 and 4 (1901). 



2 G 



