332 EQUILIBKIUM OF COLLOID AND CRYSTALLOID 



in anaemia. So, too, quinine, and the alkaloids generally, furnish a 

 basic ion affecting specific cells of the organism in each case, or of 

 pathogenic foreign organisms present in it, for which at different 

 stages they possess special affinities. 



The same specific action due to different detail in structure of 

 bioplasm, which we see exemplified in the selective action of 

 drugs in the multicellular organism, is seen, and from the same 

 cause, in the action of different drugs upon different stages of the 

 same parasitic organism. 



For example, quinine only attacks the malarial parasite when 

 it is breaking forth from the erythrocyte. Again, the drug atoxyl 

 acts on the ordinary motile form of the trypanosome, but rapid 

 recurrence shows that it does not destroy the latent bodies, while 

 mercury is shown, by the prolongation in the period of recurrence 

 which it causes when given after atoxyl, to attack the latent bodies, 

 although it has no action whatever on the ordinary motile stage. 



The closer and more detailed study of the conditions of the 

 formation of these unstable unions between bioplasm and the 

 dissolved substances of its natural and artificially varied environ- 

 ment must furnish the key to many of the intricate problems both 

 of physiology and of practical medicine; and it may perhaps be 

 added that these subjects, whether studied in the laboratory or 

 by the bedside, form one organic whole, for the subject of study 

 in both is the living cell in all its wealth of reaction to changes in 

 its environment. 



