40 



INTRODUCTION TO CYTOLOGY 



proteids in the ordinary sense, but consists of more complex phosphorized 

 bodies . . ." (Hammarsten). Such "phosphorized bodies" are the 

 nucleo-proteins, which are "probably the most important constituents 

 of the cell, both in quantity and in relation to cell activity" (Wells). 

 A long series of chemical investigations beginning with the pioneer work 

 of Miescher, Hoppe-Seyler, and Reinke, have shown that these nucleo- 

 proteins are essentially combinations of nucleic acid with proteins, or 

 sometimes with the simpler histones or the still simpler protamines. 



The nucleus as a rule is free from or very poor in uncombined carbohy- 

 drates, fats, and salts, but is characterized rather by the abundance of a 

 nucleo-protein called nuclein, isolated in 1871 by Miescher, who gave it the 

 formula C29H 4 9N9P 3 O22. It was shown by Altman (1889) that nuclein, 

 like the other nucleo-proteins, could be split into two substances: nucleic 

 acid and a form of albumin (protein), the two existing in chemical com- 

 bination like an ordinary salt. Nucleic acid from yeast was given the gen- 

 eral formula CjoHsgNuC^ 2P 2 O 5 , and that from fish sperm C^HseNuO 

 le 2P2O5. Nucleic acid was further analysed into phosphoric acid and 

 certain bases. The relation of these simple substances to nuclein, and 

 also the relation of nuclein to more complex nucleo-proteins, are shown in 

 the following scheme (mainly from Wells) : 



Higher 

 nucleo- 

 proteins 



Proteins 



Nuclein 



Proteins 



(albumins, etc.) 



f Phosphoric acid 

 Nucleic acid 



Levulinic acid 

 Purin bases 

 Pyrimidins 

 Pentoses 



Xanthin 



Guanin 



Adenin 



etc. 



The nucleo-proteins of the nucleus (chromatin) contain very little of 

 the protein constituent and are thus relatively rich in phosphorus. 

 Glaser (1916) accordingly speaks of chromatin as "a conjugated phospho- 

 protein group with a nucleic acid group, the latter group being a complex 

 of phosphoric acid and a nuclein base." Kossel (1889, 1891, 1893) 

 even concluded that in certain instances (during mitosis) chromatin 

 might be simply nucleic acid. 



In the cytoplasm, on the contrary, the proportion of the protein 

 constituents is relatively high. The cytoplasm probably has no true 

 nuclein, but is rich in nucleo-albumins, albumins, globulins, and pep- 

 tones, which, unlike nuclein, have little or no phosphorus. As a result 

 its reaction is alkaline, in contrast to the acidity of the nucleus. Accord- 

 ing to Hammarsten (1909), "the globulins and albumins are to be con- 

 sidered as nutritive materials for the cell or as destructive products in 



