64 DIFFUSION OF SUBSTANCES INTO LIVING CELLS 



seems to be the case, judging from results; but it 

 does not prove that all the other cells of the body 

 have not also absorbed some of the drug in question 

 as well, and that they may have been affected too, 

 but have shown no signs of this effect. Strychnine, 

 for example, stimulates certain cells of the nervous 

 system, as is shown by the twitchings produced by 

 it. Strychnine also causes amoeboid movements in 

 leucocytes a fact which is easily demonstrated micro- 

 scopically; but this excitation of amoeboid movement 

 within the body gives rise to no symptoms, and of 

 course passes unnoticed. It is important to remember, 

 therefore, that because a certain drug affects certain 

 cells and gives rise to symptoms related to these cells, 

 it does not follow that only those cells have absorbed 

 the drug. All have absorbed a share, but not neces- 

 sarily to the same extent, as will be shown directly. 



A cell, therefore, cannot control the diffusion of 

 substances into itself; but after it has actually absorbed 

 them the protoplasm of different classes of cells seems 

 to treat a substance differently, and the cells may* by 

 this peculiarity of their protoplasm, be able to make 

 use of it, or, on the other hand, they may leave it 

 unchanged, or thirdly, they may have to die from 

 its effects. We shall presently describe how cells 

 can be made to absorb aniline dye which contains 

 two substances one which causes the cell to re- 

 produce itself, the other a poison which kills it. As 

 both substances diffuse into the cell together, and 

 as the cell cannot control this diffusion, it will respond 

 to both. It will reproduce itself by cell-division in 



