x THE NUCLEO-PROTEIDS 451 



proteids by Miescher, 1 and constitutes one of their chief characteristics, 

 the others being their phosphorus and iron content, and the presence of 

 purin-bases. Milroy 2 and Umber 3 have, however, shown that a consider- 

 able amount of nucleic acid is liberated by good pepsin-hydrochloric acid. 

 The precipitate, according to Umber, may be pure nucleic acid, but 

 as a rule it still contains albumin, and is termed a * nuclein ' (see p. 

 449). By trypsin nucleo-proteids are dissolved ; peptones, amino-acids 

 and nucleic acids pass into solution (Umber). 



That extracts of the liver nucleo-proteids liberate ionic iron as the 

 result of auto-digestion has been pointed out by Bottazzi. 4 



The nucleins are intermediate between the nucleo-proteids and 

 the nucleic acid both genetically and as regards their properties. 

 They are much more strongly acid than are the nucleo-proteids, and 

 only with difficulty soluble in acids, even if acids are used in excess. 

 Judging by their percentage-composition, they are far removed from 

 the albumins, for, as a rule, they contain only about 40 per cent, or 

 a little more, carbon, but 4 to 7 per cent of phosphorus, from which 

 it follows that they are composed of nucleic acid to the extent of 

 at least 150 per cent. They still give the reactions of albuminous 

 substances. In gastric juice they are only soluble with difficulty, and 

 therefore pepsin-hydrochloric acid is employed in preparing them. 

 They are, however, readily dissolved by trypsin. When treated with 

 alkalies they give rise to nucleic acids or to sodium nucleates. 



Nucleo-proteids have been found by Miescher 1 in the nuclei of 

 pus-corpuscles, and by Plosz 5 in the nuclei of the red blood corpuscles 

 of birds and snakes. Lilienfeld, 6 Huiskamp 7 and others have pointed 

 out in the case of the thymus, and Miescher, 8 Kossel 8 and Schmiede- 

 berg 8 in the case of spermatozoa, that nucleo-proteids pass always 

 into solution, and only into solution when the nucleus disintegrates. 

 The nucleo-proteids are therefore constituents of the cell nuclei, and 

 in those organs specially rich in cells, such as the thymus and the 

 lymph glands, they exceed in quantity all the other albumins. 

 Lilienfeld could show that 77 per cent of the dried leucocytes of the 

 thymus represent nucleo-histone, and, not taking into account the 

 ether-soluble products, the heads (nuclei) of the ripe spermatozoa of 



1 F. Miescher, Hoppe-Seyler s Med. -diem. Untersuch. p. 441 (1871). 

 - T. H. Milroy, Zeitschr. f. physiol. Cfiem. 22. 307 (1896). 



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



4 F. Bottazzi, ZentrcdU. f. Physiol. 18. 98 (1904). 



5 P. Plosz, ibid. p. 461 (1871). 



6 L. Lilienfeld, Arch. f. (Anat. und) Physiol., Physiol. Abteil. 1892, p. 128. 



7 W. Huiskamp, Zeitschr. f. physiol. Chem. 32. 145 (1901). 



8 See footnotes 1 and 2 on p. 452. 



