98 



Mr. H. C. Ross. On a Coefficient of [Dec. 9, 



of diffusion of living cells can be obtained, and the differentiation accom- 

 p lished. 



Scheme of the Method employed. — The cells to be tested are placed on a film 

 of jelly on a slide. The film is prepared from a test-tube which contains 

 10 c.c. of jelly. The 10 c.c. of jelly contains, besides stain, some of the factors 

 such as alkalies, acids, and salts, which hasten or delay the diffusion of stain 

 into the cells. In order to simplify matters, I measure these factors in units 

 and I endeavour to arrange them in such a way that 1 unit of any one factor 

 is equal in value, as regards hastening or delaying diffusion, to 1 unit of any 

 of the other factors. The factor heat, which hastens diffusion, is applied after 

 the cells have been spread upon the film by keeping the slide at various 

 temperatures for various periods of time. This factor, as well as that of time, 

 is also arranged in units, so that 1 unit of either of them is equal in value 

 to 1 unit of the other factors contained in the agar. Hence if 1 unit of a 

 given substance delays diffusion of stain into a cell, the delay it causes can 

 be exactly neutralised by the addition, either to the agar or to the slide, of 

 1 unit of a factor which hastens diffusion. 



Consequently an equation is formulated by means of which the total 

 number of units which, with a certain amount of stain, will cause given, or 

 stipulated, staining of the cells, is equivalent to, or paid to be equivalent to, 

 their coefficient of diffusion. Therefore to find the coefficient of a cell, it is 

 necessary to prepare films from a succession of tubes of 10 c.c. of jelly, each 

 tube having a certain, known, number of units added to it, and to examine 

 each film until the stipulated staining is obtained. Since the units are equal 

 in value, it matters little, within reasonable limits, which factor is added, 

 provided that the total number of units is known. Then, after subtraction 

 of those units which delay diffusion, the remainder added to the quantity of 

 stain is the coefficient of diffusion of the cell experimented with. 



Conversely, if the coefficient of diffusion of a cell is known, one is enabled, 

 by means of the equation, to know how many units of one or several of the 

 factors it is necessary to add to the jelly, or apply to the slide, to obtain 

 stipulated staining of that variety of cell in a given time. I have mentioned 

 that the staining of healthy cells, only, appears to be constant. When the 

 rate of staining of cells of persons suffering from disease has been found 

 experimentally, the equation indicates in a moment the difference between 

 the coefficients of healthy and diseased cells, and this difference can be 

 expressed in grammes, degrees, or minutes, etc., according to the nature 

 of the factor into which the coefficient of diffusion may be ultimately 

 resolved. 



Definitions. — When a film of agar jelly contains stain and other substances, 



