THERAPEUTIC STUDIES ON IONS. 77 



of which is often sought in the theory of osmotic pressure 

 is entirely clear. The introduction of the ionic theory 

 may perhaps be the first means of bringing a better 

 understanding into this field also. Under these conditions . 

 it is readily intelligible that from a classification of the 

 ions won through a study of the changes in state of pro- 

 teins only broad generalizations can be made. These 

 have, however, shown themselves valuable in pointing 

 out the direction which further investigations must take. 



The relation between the cathartic effects of salts and 

 their power to precipitate protein has been recognized 

 for a long time, more especially through the fundamental 

 investigations of HOFMEISTER. If we bear in mind what 

 has been said above, that the power of precipitating pro^ 

 tein is a property of the metallic ions, then we will also 

 have to attribute the transitory purgative action of the 

 alkali salts to their cations. This faculty is, in fact, 

 seen to reappear, only accentuated to an extreme, in the 

 case of the heavy metals, which, it is well known, are 

 able to coagulate protein in even the weakest concen- 

 tration. The mild contractile and purgative action cor- 

 responds in the latter case to the erosion and severe 

 gastro-enteritis of the toxic picture. Most of the metallic 

 ions also influence more or less markedly the irritability 

 of the nervous system, the heavy metals producing in- 

 flammation and degeneration. 



The anions also appear as mighty carriers of pharma- 

 cological properties. This is especially true of the end 

 members of one series the nitrates, bromides, and iodides. 

 They are all readily absorbed and bring about a lower- 

 ing of the blood-pressure. The Br ion shows a much- 

 utilized sedative action, while the I ion belongs among 



