PROTOPLASM 27 



basic dye. The basic constituent of this substance in a Hving nucleus 

 may be a very complex protein, a simpler and more basic histon (blood, 

 thymus, echinoderm sperm), or a still simpler and more strongly basic 

 protamine (fish sperm). The following scheme will help to make clear 

 the relationships of these substances: 



Phosphoric acid 



Nucleic acid 

 Nucleo-proteins 

 "Nuclein" 

 "Chromatin" 



Pentoses or hexoses 

 Purin bases 

 Pyrimidins 

 Etc. 

 Protein base: protamine, histon, or other protein 



In the cytoplasm, in contrast to the nucleus, the proportion of protein 

 constituents is relatively high. The cytoplasm normally has no 

 "nuclein, " but it is rich in nucleo-albumins, albumins, globulins, and 

 peptones; these, unlike nuclein, contain little or no phosphorus. Accord- 

 ing to Hammarsten, "the globulins and albumins are to be considered as 

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

 transformation of the protoplasm." Volutin, a compound which resists 

 strong acids and shows an affinity for basic dyes,^ is frequently present 

 in the form of globules in the cytoplasm, notably in lower organisms. 

 It is usually regarded as a reserve substance. The importance of proteins 

 in protoplasmic activity is partly due to their amphoteric properties; 

 they may act either as acids or as bases under proper conditions. In 

 general, most of them act during life as acids. 



The fatty constituents of protoplasm comprise the true fats and a 

 number of more complex derivatives containing nitrogen and phosphorus, 

 such as the phospholipides (phosphatides). Among the fatty substances 

 which appear to have a peculiar importance in the organism are choles- 

 terol, ergosterol, and lecithin. Under the influence of certain light rays 

 ergosterol may be transformed into vitamin D.^ The staining reactions 

 of fixed cytoplasm apparently depend not only upon its chemical com- 

 position, but also upon the degree of physical dispersion induced by the 

 reagents used (see Yamaha, 1932). 



The carbohydrates found in protoplasm are chiefly pentoses (plants) 

 and hexoses (animals), which are, as a rule, combined with proteins and 

 with lipides. Glycogen exists free in many tissues and serves as a source 

 of energy. The important role played by pentoses and pentosans in the 

 activity of the plant cell has been strongly emphasized; in fact, proto- 

 plasm has been called "an intermeshed pentosan-protein colloid."" 



^Reichenow (1909), van Herwerden (1917), Doflein (1918). 

 ^ See Gortner (1929, Chaps. XXXI-XXXII, XXXV). 

 «Spoehr (1917, 1919), MacDougal (1920). 



