140 LECTURE VII. 



other compound is not a nucleic acid, but a combination of this with 

 albumin. This is called nuclein. On further decomposition, it breaks 

 down into albumin and nucleic acid. 



The nucleoproteids are all soluble in water and salt solutions. They 

 are very soluble in alkalies. They are distinctly acid in their charac- 

 teristics. They are precipitated by acids, although redissolved by an 

 excess. The nucleoproteids can be " salted-out " and coagulated by 

 heat and other means. When nucleoproteids are digested with pepsin- 

 hydrochloric acid, nuclein settles out, while the albuminous cleavage- 

 product is dissolved by the ferment in the usual manner. Fr. Miescher, 1 

 the discoverer of the nucleins, noticed this characteristic property. The 

 nucleins themselves are but little affected by pepsin-hydrochloric acid, 

 although more so by trypsin. It is very difficult to purify them; in fact, it 

 is doubtful whether they have ever been isolated in a pure condition. 



The nucleoproteids often contain iron, and it is very probable that the 

 main supply of this element in the system occurs in these, and in hemo- 

 globin. They are present in every cell, and are found in the nucleus. 

 Miescher first noticed them in the little pus cells. They were isolated 

 shortly afterwards also from the blood corpuscles of birds and snakes. 

 We must also state that efforts have been made to place the ferments 

 themselves in the group of nucleoproteids. By the discovery of nuclein 

 and the nucleoproteids, Fr. Miescher has substantially advanced our 

 knowledge of the constituents of the nuclei. The fact that all nuclei 

 whether plant or animal contain nucleoproteids is another link between 

 these two great kingdoms. We must not, however, forget that we know 

 practically nothing about the biological significance of these substances. 

 They have interested us greatly, especially on account of their predomi- 

 nance in the nuclear material, and the ease of obtaining them. The 

 importance assigned to them may, however, be entirely unwarranted. 

 Our knowledge of the other constituents of the nuclei is far too meager 

 to tell us much concerning the functions of the nucleus. 



Nucleoproteids have been isolated from almost every organ. So, also, 

 from the spermatozoa-masses. Those of fishes contain up to 96 per cent 

 of nucleic-acid-protamine, or -histon. Fr. Miescher and Schmiedeberg give 

 the following composition to salmon spawn: 60.5 per cent nucleic acid, 

 35.56 per cent protamine. A nucleic-acid-histon has been obtained from 

 the sea-urchin (Arbacia pustulosa)? The spermatozoa of bulls also 

 contain a nucleoproteid, which, however, does not contain protamine 

 nor histon, but some other kind of protein. 3 Nucleoproteids have also 

 been isolated from the thymus gland, from the red corpuscles of birds 



1 Fr. Miescher: Hoppe-Seyler's Med.-chem. Untersuchungen, p. 441 (1871). 



2 A. Mathews: Z. physiol. Chem. 23, 399 (1897). 



3 Fr. Miescher: Arc. exp. Path. Pharm. 37, 100 (1896). 



