i 3 4 SCIENCE PROGRESS. 



reactions to staining agents. Thus on staining different 

 substances with the Ehrlich-Biondi triple stain Kossel 1 

 found that proteids select the acid stain, i.e., the fuchsine, 

 that nucleic acid on the other hand takes the basic stain, the 

 methyl-green. On staining resting nuclei with the triple 

 stain they are tinted of a violet colour, and therefore Kossel 

 argues contain the nucleic acid combined with proteid ; on 

 the other hand, in cells that are subdividing, the nuclei stain 

 a green colour, showing that a large part of the nucleic acid 

 is probably in a free state. The same reaction to stains is 

 shown by the nuclei of freshly formed spermatozoa. 



It is, however, with the constitution of nucleic acid that 

 we are here chiefly interested, and our knowledge so far de- 

 pends upon the decomposition products that have been ob- 

 tained from it by various methods. The whole of the 

 phosphorus may be separated as phosphoric acid by boiling 

 it for a short time with dilute sulphuric acid. According to 

 Liebermann 2 the phosphorus exists in the nucleic acid mole- 

 cule in the form of metaphosphoric acid, for he obtains it as 

 such by heating for a short time with dilute nitric acid. 

 That it is not all held in the same way in the molecule is 

 shown by the fact that one part of it can be readily split off 

 from the molecule by simply heating it for a time in water. 

 The major part, however, under such treatment remains 

 unaffected. 



Since Kossel first showed that the nuclein prepared 

 from yeast yielded xanthin and hypoxanthin, and at a later 

 time that the nucleic acid molecule was the source of these 

 bases, many nucleic acids have been examined for these 

 alloxuric bodies, so that now the identification of a nucleic 

 acid depends upon proving the existence of one or more of 

 these bases as a result of decomposition of the moleule. 

 The chief members of this group of alloxuric bases are as 

 follows : — 



i. Xanthin, C 5 H 4 N 4 2 , which has been obtained from 



1 Kossel: Deutsche, med. Woch, 1894, No. 7. 



2 Liebermann : Pflilger s Arch., Bd. 47, S. 155, 1890 ; and Ber. d. d* 

 Chem. Ges., Bd. 21, S. 598, 1888. 



