REASON FOR ACIDITY OF JELLY 89 



Stain, Unna's polychrome methylene blue (Grubler), 

 behaves as if it increased diffusion. Unit 0.1 cc. 



The reason why the "coefficient jelly" is made acid 

 at the outset is this. Alkalies increase diffusion; 

 acids delay it. Acids neutralise alkalies, and between 

 the two there is a neutral point. If the jelly is 

 neutral at the outset, we might have to add acid in 

 the case of a cell having a very low coefficient of 

 diffusion. Again, we may frequently have cases of 

 cells which stain on a neutral jelly. Our equation, 

 therefore, would have to include these three factors 

 alkalies, acids, and a neutral point which would 

 be very complicated, as the neutral point would 

 introduce zero. The object throughout has been to 

 make the determination of coefficient of diffusion of 

 cells, and the estimation of diffusion of substances 

 into them, as simple as possible in their practical 

 application, and in order to do this the "coefficient 

 jelly" is rendered acid at the outset and one deals 

 only with the one factor alkali. The original 50 cc. 

 of jelly contains . 083 gramme of citric acid ; therefore 

 each tube of 5 cc. of "coefficient jelly" contains 0.0083 

 gramme of citric acid; and each tube will ultimately 

 be made up to 10 cc., which, of course, will also 

 contain this amount of citric acid, unless it is 

 neutralised by alkali. This 0.083 gramme of citric 

 acid represents 2 units of acid, and it is neutralised 

 by 2 units of alkali. If we w r ant to try a jelly which 

 is acid to the extent of 2 units, w T e simply add no 

 alkali. We are not likely to want a jelly which is 



