THE FACTORS CONCERNED 71 



factors already mentioned. Alkalies and alkaline salts 

 greatly increase the diffusion of other substances into liv- 

 ing cells. By means of a strong alkali one can cause a 

 substance like stain to diffuse into a cell so rapidly as to 

 induce death and staining of the-nucleus almost instantly. 

 And this marked increase of diffusion caused by alkalies 

 also takes place in an arithmetical progression; that is 

 to say, if the jelly or solution contains 2 per cent of an 

 alkali, another substance present will diffuse into the 

 cell twice as rapidly as it would if the jelly or solution 

 only contained 1 per cent of the same alkali. Our 

 equation must therefore contain a symbol for alkali 

 also: 



All the above four factors namely, the concentration 

 of the substance diffusing, the time, the heat, and the 

 alkalies increase the diffusion. Neutral salts, however, 

 decrease it. The more of a salt one adds to the jelly, 

 the less of any other substance, ceteris paribus, will 

 diffuse into the cell in a given time. And this retarding 

 effect of a neutral salt also varies exactly with the 

 amount of the salt present. We may therefore add 

 salts to our equation with a minus sign before them, 

 thus: 



diff = S+T + H+A-salts 



Acids, of course, delay the diffusion of other sub- 

 stances, for they neutralise alkalies; and the amount of 

 retarding effect due to an acid is in exact proportion to 

 its neutralising effect on any alkali present. But apart 

 from this neutralising action of acids, they also actually 



