316 THE EQUILIBKIUM OF COLLOID AND 



which we know as internal secretions, lysins, antibodies, toxins, 

 hormones, etc. 



Turning now from the organic food-stuffs and the synthesised 

 products of metabolism to the inorganic crystalloids of the cells 

 and body fluids, we find abundant evidence of union in labile equili- 

 brium between these and the organic constituents of the body- 

 unions which are absolutely essential to the life and work of the 

 cell, specific in character from one type of cell to another, and 

 which owe their peculiar and effective functional power in the life 

 of the cell to the very feebleness of the union which allows of inter- 

 change and reaction. So that we have stability of the whole system 

 in the midst of and indeed as a consequence of the instability of the 

 constituent parts. 



The first evidence which may be quoted in favour of this form 

 of union is the peculiar distribution of the inorganic salts and ions 

 as between tissue cells and their environing fluids, the plasma and 

 lymph. 



Although the same inorganic salts are present in the cells 

 of the tissue and in the blood-corpuscles as are found in 

 the lymph and plasma, the quantitative distribution is very 

 different in the two cases. The cells are rich in potassium 

 and phosphatic ions, and relatively poor in sodium and chlorides, 

 while the converse holds in the case of the bathing fluids of 

 the cells. 



This peculiar distribution finds an easy explanation on the basis 

 that the proteins of the cells are so constituted chemically that they 

 possess affinities for absorbing or uniting with potassium and 

 phosphatic ions, and have no such power for holding sodium and 

 chlorine, while the converse holds for the proteins of the plasma. 

 For under these conditions, with the same osmotic pressure of 

 dissolved constituents within and without the cell, any particular 

 ion will increase in amount in the absorbed or united form in that 

 particular region where protein is found possessing an affinity 

 for it. 



No other view which has been put forward furnishes an adequate 

 explanation of this peculiar distribution of the salts. The other 

 view which has obtained most adherence is that there exist mem- 

 branes with peculiar and specific properties surrounding the cells 

 which present a varying resistance to the passage of different ions. 

 These membranes, which recently have been regarded as consisting 



