MODE OF DETERMINATION 75 



all added up to make a grand total figure which repre- 

 sents the "coefficient of diffusion," or, to express it 

 briefly, the "c/" of the cell. 



The coefficient of diffusion of a cell is determined 

 by adding up the total amounts of the factors required 

 to cause a certain extent of staining of the cell. The 

 extent of staining which we always use as a standard is 

 the staining of the nucleus. Now, the "moment" of 

 the staining of the nucleus of a cell can be recognized 

 through the microscope, and it has an additional 

 importance, insomuch as it is coincident with and 

 signifies the death of the cell. In reality, therefore, the 

 determination of the coefficient of diffusion of a cell, as 

 well as supplying the rate of diffusion of substances into 

 it, also tells us how much of the stain, together with 

 the other associated factors, are required to make it (the 

 stain) diffuse into the cell so as to cause the cell's death 

 in vitro. In other words, it tells us the amount of a 

 standard dye required to be in the immediate surround- 

 ings of a cell, so that it may diffuse into it to such an 

 extent as to cause its death by combining with the 

 chromatin within the nucleus. 



In order to determine the coefficient of diffusion of 

 a cell, how r ever, it is necessary to count up, not only the 

 number of the factors required to cause staining of the 

 nucleus, but also the amount of each factor required. 

 To do this it is necessary to measure each factor. One 

 could, of course, measure the chemical factors, such as 

 alkalies, salts, etc., in grammes, the heat in degrees of 

 temperature, and the time in seconds; but this would 

 necessitate a complicated total figure involving grammes, 



