100 " COEFFICIENT OF DIFFUSION OF CELLS" 



stance is made to diffuse into the cells, they may each 

 affect the diffusion of the other; for they may them- 

 selves be alkalies, acids, or salts. In this case the unit 

 of each must be found, and their action on the diffusion 

 of other substances into the cell allowed for. 



It is necessary to point out that this method is 

 reliable only within certain limits, and precautions must 

 be taken to prevent errors due to employing excessive 

 amounts of substances, heat, and time, and those due 

 to possible contingencies arising when dealing with cells 

 from tissues. 



The following list of precautions has been copied 

 from the paper in the Proceedings of the Royal Society: 



Precautions. As regards Life and Death: In a 

 previous paper 1 it has been shown that the staining 

 of the nuclei of leucocytes, when examined by this 

 method, is a sign of death, and that the nuclei of dead 

 cells will stain, ceteris paribus, before those of living 

 cells. Consequently all the experiments given in the 

 present paper have been made with fresh normal cells, 

 and in the case of micro-organisms, with cultures not 

 more than forty-eight hours old. It may also be men- 

 tioned that the liquefaction of the cytoplasm which 

 occurs after death materially alters the conditions of 

 staining of leucocytes, and that the cf of living cells 

 falls gradually after the blood has been shed. 



As regards Excess of Alkali, causing rapid death 

 and liquefaction of the cytoplasm, with consequent 

 prevention of staining (achromasia) : The addition of 



1 "On the Death of Leucocytes" (H. C. Ross, Journal of Physiology, 

 vol. xxxvii., p. 327,1908). 



