80 DIFFUSION OF SUBSTANCES INTO LIVING CELLS 



(B. Vol. 81) ; and the description of the methods and 

 laws given herein are in reality an elaboration of the 

 original ones given in the papers mentioned. Much 

 work has been done, however, since those papers were 

 written, including induced cell-division by a variety 

 of chemical substances, and all of it has been carried 

 out with those specifications as bases. The point is 

 mentioned in order to show that the method is fairly 

 reliable. New technics of this nature, where one is 

 dealing with a series of factors, all of which are 

 variables, are prone to become involved in their 

 application. The "moment" of the staining of the 

 nucleus cannot be a very accurate one, and the more 

 factors and units one deals with, the more do small 

 errors assert themselves. 



It is a simple matter to note the effects on a cell 

 of two or three units of a dye and a unit or two of 

 alkali. But when one deals with complicated equa- 

 tions involving twenty or thirty variable units, each 

 of which modifies the action of its neighbour, it 

 sometimes follows that complicated situations arise. 

 For instance, the units of the two salts are satisfactory 

 when small quantities of them are used; but with 

 larger quantities it will be found that they are not 

 quite so accurate. For practical purposes, however, 

 the units given have been found to be sufficiently 

 useful ; but if this method was to be employed to 

 determine the more scientific data of the action of 

 the several physical factors in increasing and decreasing 

 diffusion, I am prepared to admit that some units will 

 require modification. 



