97 



On the Determination of a Coefficient by which the Rate of 

 Diffusion of Stain and other Substances into Living Cells can 

 be Measured, and by which Bacteria and other Cells may be 

 Differentiated. 



By Hugh C. Eoss, late Surgeon B.N., Pathologist to the Boyal Southern 



Hospital, Liverpool. 



(Communicated by Major Eonald Eoss, C.B., F.E.S. Eeceived December 9, 

 1908— Eead February 11, 1909.) 



[Plate 3.] 



In former papers (3, 4, 5) it has been shown that when blood is spread 

 upon a film of agar jelly which contains Unna's stain and certain salts, the 

 cells will absorb the stain, and that the absorption increases with the tempera- 

 ture and the time during which the cells have been resting on the film. The 

 following facts have also been published : — (1) That alkalies, like heat and 

 time, increase the diffusion of stain into the cells ; (2) that acids and neutral 

 salts delay the diffusion ; and (3) that the staining of the nuclei of leucocytes 

 is a sign of death. Soon after death the staining ceases, and the cells rupture 

 or lose their stain. 



Evidence has also been given that these phenomena are due to the diffusion 

 of stain into the jelly-like cytoplasm being hastened or delayed, as the case 

 may be, by the agency of these factors, and that death, coincident with the 

 staining of the nucleus, is followed by liquefaction of the cytoplasm and 

 other changes which cause the cells to lose their stain and enter a phase which 

 has been called the condition of achromasia (6). 



I have made further investigations in this subject, and have ascertained 

 that if the constituents of the agar film are arranged in a constant manner 

 and the other factors are constant, the staining of the cells will be constant 

 provided that the latter are in the same healthy condition when placed on 

 the agar. It has also been found that when one class of blood cell stains on 

 a given agar film, others do not. By altering one or more of those factors 

 which hasten or delay diffusion of stain into the cytoplasm, that class of cells 

 which previously refused the stain will now absorb it. Therefore the rate of 

 diffusion of stain into the cells differs with the class of cell. Cells other than 

 blood cells, especially bacteria, have also been tried and have been found to 

 be subject to the same conditions ; and it has been possible, by altering the 

 arrangement of the factors, to differentiate cells by their rate or coefficient of 

 diffusion. The object of this paper is to give methods by which the coefficient 



VOL. LXXXI. — B. H 



