68 DIFFUSION OF SUBSTANCES INTO LIVING CELLS 



contains a certain quantity of an aniline dye, such as 

 Unna's polychrome methylene blue. This dye com- 

 bines with the cell-granules and stains them red, and 

 the rate of the diffusion of the dye can be estimated 

 by observing the depth of coloration of the granules 

 and the time occupied before the nucleus stains. The 

 first granules to stain, of course, are those which are 

 nearest to the jelly, for the cell is pressed against it by 

 the cover-glass. With a given quantity of dye, the 

 depth of coloration and the rapidity of the extent of 

 staining will take a certain length of time. No matter 

 how often this experiment is repeated, provided the 

 arrangement of the jelly is always the same, with the 

 same type of cell, the result is always the same; but 

 if a fresh jelly is prepared, with double the quantity of 

 stain, the depth of coloration will be double, and the 

 same extent of staining will be reached doubly as 

 quickly as with the first jelly. If the concentration 

 of the dye is trebled or quadrupled, etc., the depth of 

 coloration and the rapidity of the given extent of 

 staining are also trebled, quadrupled, etc., as the case 

 may be. 



Hence we arrive at the first law, which is, that the 

 diffusion of a substance into a cell varies directly with 

 the concentration of the substance in the solution in which 

 the cell is resting. The more concentrated the sub- 

 stance, the more it will diffuse into the cell, apparently 

 in arithmetical proportion. In a given time, ceteris 

 paribus, a 2-per-cent solution of a substance will have 

 double the effect on a cell as compared with a 1 -per- 

 cent solution. 



