CRYSTALLOID IN LIVING CELLS 27 



affinity, then we arrive at a conception which is capable of linking 

 together the osmotic properties of the cell, not merely in a statical 

 but in a dynamic way, and gives a basis for understanding the 

 variations in osmotic effects which accompany cell activities from 

 one phase to another. 



With the view of an inert semi-permeable membrane of fixed 

 properties, not sharing the varying changes in chemical constitu- 

 tion associated with life, or in other words not possessing the 

 properties of bioplasm outlined above, all that can be arrived at 

 is a continual tendency in one direction to a fixed equilibrium. 



The other view, that the osmotic properties are developed by 

 the bioplasm itself in its varying unions with' crystalloids, gives 

 room for that up and down play of properties which is the out- 

 standing characteristic of living matter. 1 



For example, a circulating hormone, a drug substance or a 

 nerve impulse arriving at a given set of cells in a tissue, may activate 

 the cells by momentarily disrupting unions between bioplasm and 

 crystalloids or the reverse, and so may cause an uptake or a giving 

 out of water accompanied by certain crystalloids free in excess to 

 or from the cell, or may alter water distribution in varying parts 

 provoking muscular contraction or other form of protoplasmic 

 movement. 



Similarly molecular movements of radicles attached to the 

 bioplasm may be induced, causing changes in molecular arrange- 

 ment and synthesis of new bodies within the cell. Further, the 

 osmotic pressures and concentrations of the crystalloids and other 

 bodies so set free need obviously bear no immediate relationship 

 to the concentration of these substances in the plasma outside the 

 cell, and so the very varying concentrations of secretions may be 

 understood in a way that cannot be realised on any basis of pure 

 osmosis or filtration. 



The experimental facts of cell life, both in regard to the taking 

 up and giving out water and substances in solution, furnish a 

 clear demonstration that neither osmosis nor any other physical 

 hypothesis which leaves out the peculiar and varying chemical 

 constitution of bioplasm can yield an explanation of absorption, 

 secretion, or excretion. 



1 It is interesting to note that serum proteins exactly at their neutral point 

 show no osmotic ptvssun- whatever, I nit addition of minute amounts either of acid 

 or alkali at once gives rise to an osmotic pressure which up to certain limits 

 increases with amount of acid or alkali added. 



