THEIR NATURE 107 



plasm, which, when it is alive, appears to be in the form 

 of a jelly. Now, it is obvious that if the cytoplasm 

 liquefies in a few seconds, diffusion-vacuoles cannot ap- 

 pear, for it is unlikely that a liquid like a solution of stain 

 cannot remain suspended in droplets in another liquid 

 like liquefied cytoplasm. On the other hand, if the 

 cytoplasm is alive and jelly-like, any excess of stain which 

 diffuses into it will become suspended in it as a "red 

 spot." Hence, if death is caused extremely rapidly, no 

 matter to what excess the diffusion is increased, diffusion- 

 vacuoles will not appear, and, owing to the excess, 

 liquid passes into the cell. If this excess is great, the 

 dead cell will be seen to burst (it appears even to 

 explode sometimes, especially if there are no salts to 

 delay the diffusion), and the cell-granules are scattered 

 about the field of the microscope. It is a well-known 

 fact that if water is mixed with blood, the leucocytes 

 will burst, the reason being the same, for the water 

 passes into the killed and liquefying cytoplasm, and the 

 intracellular tension is so great that rupture of the cell- 

 wall takes place. There are no salts to delay the 

 diffusion of the water, which now occurs to such excess 

 that it causes the cell to rupture. 



In order to demonstrate the diffusion-vacuoles, 

 therefore, it is necessary to delay death, which can 

 be done by placing salts in the jelly- film such as are 

 present in the "coefficient jelly." Diffusion is then 

 increased by alkali or heat until maximum diffusion, 

 short of causing death, is obtained; for it must be 

 remembered that all artificial substances will kill 

 human cells, and the more they diffuse into them the 



