26 THE EQUILIBRIUM OF COLLOID AND 



be neglected. In fact a wider appreciation of the phenomena of 

 union between the bioplasm and crystalloid constituents widens 

 rather than narrows our conceptions of the cell as an osmotic 

 centre, by allowing us to regard the cell as a chamber with vary- 

 ing osmotic properties, both of contents and wall, rather than as 

 heretofore as a- more or less fixed solution, bounded by a mem- 

 brane of fixed properties also, and resembling a semi-permeable 

 copper-ferrocyanide wall. 



The rigorous conception of the cell as analogous in all respects 

 to a fluid medium holding crystalloids simply in solution and 

 bounded by a semi-permeable wall is most pernicious in biology, 

 for there are no experimental facts to warrant such a view, but 

 rather, as has been shown above, quite the reverse. 



The whole chemical structure of the cell and that part of it 

 which is physiologically active is the osmotic machine, and needs 

 no membrane permeable or impermeable in order to exhibit the 

 usual osmotic phenomena of shrinking or swelling, leading finally 

 to disruption. In some cases membranes in the narrower sense 

 of the word are demonstrable surrounding the cell mass, and in 

 other cases which form the vast majority, no such coarsely structural 

 membranes exist ; but in all cases the nature of the bioplasm is 

 so differentiated chemically as to form a dividing surface readily 

 permeable to the solvent, and this is all that is required, in addition 

 to the varying unions or holding powers between the cell colloids 

 and crystalloids, to establish an osmotic cell. As an example of 

 what is meant here we may instance the swelling of fibrin, con- 

 nective tissue, and gelatine under the imbibition of water. Be- 

 tween gelatine and water there is no. structural membrane with 

 semi-permeable pores, yet the gelatine takes, in water in a truly 

 osmotic fashion, and the pressure developed, if the swelling and 

 uptake of water are resisted, is Very high. 



It is hence necessary to get our minds rid of the preconceived 

 idea derived from too closely drawn analogies with experimentally 

 constructed osmotic cells that the cell membrane is responsible 

 for the osmotic behaviour of the whole cell. 



If instead of this we take the view, which is supported by ex- 

 perimental facts, that the bioplasm holds the crystalloids in loose 

 union in the cell, so that they cannot for the time escape or diffuse 

 out, and yet admits of a degree of molecular freedom to the 

 crystalloids, so that they still attract water molecules by residual 



