50 CELLULAR 



fashion. The diflPerence between a cell imme- 

 diately before and just after death might there- 

 fore be essentially a difference in the structure 

 and chemical composition of the semipermeable 

 surface. 



It may be added that such semipermeable sur- 

 faces are not confined to the exterior of the cell 

 but exist also at the boundaries of nuclei, plas- 

 tids, microsomes, and other structures in the cell. 

 It may be that the chief advantages of cell divi- 

 sion (as well as of the differentiation of cell 

 organs) is to provide such surfaces and thereby 

 to segregate various vital activities. 



In this connection we may recall that Loeb 

 has insisted that the colloidal properties of 

 matter are manifested only where semiperme- 

 able surfaces exist. A study of such surfaces is 

 important for chemistry as well as for biology 

 and it is possible that further investigations in 

 this field will lead to contributions to chemical 

 theory just as did the work of Pfeffer at an 

 earlier period. 



These and other studies now in progress have 

 changed our point of view and are bringing a 



