12 GERM-CELL CYCLE IN ANIMALS 



a hextose (carbohydrate) ; and 



phosphoric acid. 



Its formula, according to Schmiedeberg, is C 4 oH 56 

 NuOie . 2 PaOs, and according to Steudel, C 43 H57 

 Ni 5 Oi 2 . 2 P2O 5 . Considerable progress has been 

 made, especially by Emil Fischer and his students, 

 in the synthesis of protein-like bodies. Many com- 

 plex polypeptides have been built up which resemble 

 peptones in many of their reactions and when in- 

 jected into living organisms appear to be utilized 

 in metabolism in much the same way as are native 

 proteins. 



We are still, however, very far from an adequate 

 understanding of the nature of chromatin. Delia 

 Valle (1912), for example, after an exhaustive study 

 of the physico-chemical properties of chromatin 

 both in the resting nucleus and in the dividing cell, 

 has concluded that this substance resembles that 

 of fluid crystals. "Consequently all of the pheno- 

 mena presented by the chromosomes ; their mode of 

 origin, differences in size, state of aggregation, form, 

 structure, colorability, optical characteristics, varia- 

 tions in form, longitudinal division and the phenom- 

 ena which follow this mode of scattering, demon- 

 strate that the chromosomes are crystalloids." 



Two other primary constituents of protoplasm may 

 be mentioned briefly. The phosphatide, lecithin, 

 belongs with cholesterin to a group of compounds 

 called lipoids. It consists of glycerophosphoric acid 

 plus certain fatty acid radicles, such as stearic acid, 

 oleic acid, etc., and a nitrogenous base (cholin). It 



