SOAPS, PROTEIN DERIVATIVES AND TISSUES 245 



sulphate. Such facts explain the " poisonous " and swelling effects 

 of pure potassium or pure chlorid solutions upon normal cells 

 which on exposure to these lose their sodium and calcium or their 

 sulphate and phosphate, etc. 



On the other hand, anything which decreases the water hold- 

 ing power of the protoplasmic colloids is to be listed as a cause 

 for " abnormal water loss," for shrinkage of the cell or, to use 

 the terminology of the botanists, " plasmolysis." Much effort 

 has been made to bring these swellings and shrinkings into rela- 

 tionshi { > \vi t h t he laws of osmotic pressure. That all such attempts 

 have failed will surprise no one, the laws governing the water- 

 holding powers of cells are the laws which govern the water- 

 holding powers of their " normal " colloid proteins and protein- 

 ates and of the new colloid derivatives produced from these when 

 exposed to the action of different salts. Since the derivatives 

 produced are possessed of entirely different hydration capacities 

 even when the salts are applied in the same concentration the 

 ultimate swellings and shrinkings must obviously also be dif- 

 ferent in spite of equivalence in " osmotic pressure." 



As we previously listed various elements as " causes " of 

 oedema we could now in similar fashion list others as causes of 

 plasmolysis. In sufficient concentration all salts are such, but 

 in their mode of action we must distinguish between at least 

 two types of effects. Even without entering the protoplasmic 

 mass, salt molecules may bind water and so take it away from 

 the hyd rated protoplasmic mass (shrinking it through "depriv- 

 ation of solvent" as first suggested by FRANZ HOFMEISTER ] ); 

 on tin- other hand the salt radicals may replace others in the 

 protoplasmic mass binding themselves to the vacated . bonds. 

 In this way lead, mercury and similar proteinates are produced 

 which, as compared with the more " normal " potassium, sodium 

 and magnesium proteinates, suck up scarcely any water at all. 



I a 



The colloid-chemical variations accompanying chemical 



change in the fundament of the living cell are not, however, 



exhausted by this change in its water-holding power. Its -olu- 



1'ilitv in water also changes. Generally speaking those proto- 



1 FRANZ HOFMEISTER: Arch, f exp. Path. u. Pharm., 26, 6 (1888). 



