104 DIFFUSION- VACUOLES 



certainly not composed of liquid; they are not cavities; 

 and, so far as we have observed, they play no part in 

 cell-division. When the cytoplasm liquefies at death 

 they disappear, and when a cell divides they seem to 

 migrate into the cytoplasm, remaining outside the 

 chromosomes and centrosomes. 



The diffusion-vacuole is quite another kind of body 

 (fig. 17). It is never seen in a normal cell which has 

 been freshly removed from the tissues. "Red spots" 

 alw r ays appear gradually (fig. 18), beginning as minute 

 coloured points in the cytoplasm, which gradually 

 become larger until in the case of leucocytes they 

 may become as large as a lobe of the nucleus. Two 

 or more may coalesce to form one large diffusion- 

 vacuole; and their appearance depends entirely on the 

 laws of diffusion; in fact, they may be produced in 

 leucocytes at will by arranging the plus factors, heat 

 and alkali, in the equation in such a way that they 

 promote the diffusion of a substance to excess. 



Diffusion-vacuoles appear only in living protoplasm. 

 After death the cytoplasm liquefies and the cell 

 becomes disorganized, when diffusion-vacuoles cannot 

 appear in it. The actual passage of a substance, say, 

 stain, through a living cell's cytoplasm occupies a 

 certain amount of time, which can be shortened by 

 Jieat or alkalies and lengthened by salts. If heat and 

 alkali are present, but the salts are absent, the stain 

 diffuses into the cell so quickly that death may ensue 

 in a few moments, because the nucleus becomes stained.. 

 Indeed, one may thus cause death in a few seconds; 

 and death is accompanied by liquefaction of the cyto- 



