THE CHEMICAL NATURE OF DIFFERENTIALS 579 



However, important and suggestive as the experiments and conclusions 

 discussed in this chapter are, they do not solve the problem as to the nature 

 of the organismal differentials. After all, it is most probable that the protein 

 molecule as a whole, perhaps with the addition of smaller conjugated groups, 

 represents these differentials, while the larger haptens are characteristic of 

 organ and certain other differentials. Also, in regard to the part of the cell 

 where the organismal differential proteins are situated, no certainty exists. 

 Bensley distinguishes the mobile protein, which is found mainly in the interior 

 of the cell, from plasmosin, a viscous material extracted with 10% NaCl 

 solution and rich in nucleoprotein, and from particulate components of the 

 protoplasm, which are submicroscopic, contain nucleoprotein and phospho- 

 lipids and are identical with or associated with certain enzymes and viruses. 

 They are in certain respects similar in constitution to the mitochondria, but 

 not the same as the latter. There remain some more solid constituents in the 

 form of membranes and threads. It is very likely that the exoplasm of the 

 cell, which presumably is rich in plasmosin, plays a prominent role in the 

 reactions against strange organismal differentials, and this substance may 

 also contain, or constitute organismal differential proteins ; but the possibility 

 cannot be excluded that other cell constituents as well may bear these differen- 

 tials. The following recent observations of Claude suggest that also the par- 

 ticulate components of the protoplasm may be self-perpetuating and this in 

 turn suggests that they, too, possess individuality differentials. 



Claude distinguishes small cell particles (cytoplasmic granules or micro- 

 somes) which are suspended in the homogeneous cytoplasmic ground sub- 

 stance and which correspond to the particulate components of Bensley, from 

 mitochondria, Golgibodies and especially from the zymogen or secretory 

 granules. The latter contain more nitrogen and sulphur, but less phosphorus 

 than the microsomes, but both are composed of phospholipids and ribonucleo- 

 proteins; there is moreover some indication that the secretory granules con- 

 tain a material similar to the microsomes and both of these cell constituents 

 may have therefore a common origin. In contrast to these cytoplasmic cell 

 components in the chromosomes, which are the most important constituents 

 of the nuclei, thymonucleic acid is a significant part, but Claude suggests 

 that both these types of nucleoprotein, the cytoplasmic as well as the nuclear, 

 may have the ability to reproduce their constituents by autocatalysis. 



The prominence of the nucleoproteins in various components of the cell 

 becomes of special interest if we consider the probability that some viruses, 

 including agents which are involved in the production of tumors, are of a 

 nucleoprotein nature. 



