THE PHYSICAL CHEMISTRY OF PROTOPLASM 227 



erated by it, and the equilibrium point of the reaction is changed 

 by the proportions of water which are present in the reacting mass. 

 Hence, the presence of large proportions of water in the colloidal 

 complex known as protoplasm has a very important influence upon 

 its possibilities of biological reactions, 



SALTS 



Active protoplasm contains mineral salts in solution. These 

 are of the same general nature as those found in sea-water, which 

 is the original habitat of the earlier evolutionary forms of living 

 matter. Or, it might be said that both plants and sea-water derive 

 their mineral salts from the same source, namely the soluble salts 

 of the soil. Recent investigations have shown that the propor- 

 tions of sodium ions to calcium ions in sea-water are precisely 

 those which maintain fats, proteins, etc., in a true colloidal emul- 

 sion; and that comparatively small variations in the ratio of 

 these two cations produce very marked effects upon the colloidal 

 conditions of these substances in an artificial colloidal preparation, 

 which resemble very closely the changes which apparently take 

 place in cell protoplasm under the influence of narcotics, or nerve 

 stimulants, in blood-coagulation, in the parthogenetic develop- 

 ment of germ cells, in cancerous growth of tissues, etc. In other 

 words, in so far as it has been studied in this respect, cell plasma 

 exhibits exactly the same responses to variations in the propor- 

 tions of salts (electrolytes) in solution, that artificial emulsions of 

 oils (fats) in water do; and the normal, or critical, equilibrium 

 proportion of these electrolytes for all colloidal complexes is that 

 in which they occur in sea-water. It must be admitted that 

 there is as yet no definite evidence that the observations which 

 have been made upon the protoplasm of animal tissues will apply 

 equally well to plant cell protoplasm. But many of the phenomena 

 which have been studied in animal tissues have what are appar- 

 ently similar, if not identical, effects in plant tissues, and it seems 

 reasonable to suppose that these conclusions apply generally to 

 protoplasm of either animal or plant origin. 



The effects which salts produce in protoplasm are undoubtedly 

 due to the fact that, when in solution, they readily ionize and 

 conduct the electric current. A discussion of the nature and 

 importance of the theory of dissociation of electrolytes in solution, 



