128 DIFFUSION- VACUOLES 



have disappeared altogether the cell resembles the 

 ordinary erythrocyte. The nucleated red cell has a 

 coefficient of diffusion of about 11, and so has the 

 granular cell. An ordinary erythrocyte's coefficient of 

 diffusion seems to be much higher, however; but since 

 it has no nucleus or granules to stain, it is difficult to 

 determine it. 



To stain the stroma of an ordinary red cell it re- 

 quires a jelly with an index of diffusion of nearly 20. 

 Like other blood-cells, the coefficient of diffusion of 

 red cells falls the longer the blood has been shed, 

 until, with a jelly suitable for staining the nuclei of 

 leucocytes, the stroma (or perhaps it is the haemoglobin 

 itself) of red cells will stain in many instances. It 

 is presumed that this more rapid staining of the stroma 

 or haemoglobin of red cells which have been shed some 

 time is due, as in other cells, to the lowering of the 

 coefficient of diffusion, for extracts of dead tissues and 

 morphia also have this effect on them. 



The stroma or haemoglobin whichever it may be 

 stains more readily in nucleated and granular red cells 

 than in the others. "Red spots" will fairly often be 

 seen in nucleated red cells and in granular ones; but 

 they have only been seen three times in ordinary 

 erythrocytes. 



Apart from their scientific interest, however, diffu- 

 sion-vacuoles are not of great importance, we think, 

 except that their appearance, as noted above, is a 

 signal that maximum diffusion is being occasioned. 



I have now described what we know concerning the 

 diffusion of substance into living cells. It is a complex 



