TECHNIQUE 245 



allow it to be deficient in alkali by a unit or so at 

 first. A film is made with some fresh blood spread 

 on it and incubated for ten minutes. The temperature 

 of 37 C. must be accurate; many failures have resulted 

 owning to the neglect of regulation of the incubator 

 temperature. If the chromosome-granules of the 

 lymphocytes are unstained, a drop or two of alkali 

 solution is added to the jelly and a fresh film is tried. 

 Soon the right alkalinity will be obtained to induce 

 early mitosis in the ten minutes ; and now if more alkali 

 is very carefully added to the jelly and another film 

 made, later stages of mitosis will be induced. It is 

 instructive to proceed farther and once more add alkali, 

 when the cells will be killed too quickly, and only very 

 early stages will be seen in the ten minutes, for there 

 has not been time for late phases to occur before the 

 cells have died. If more alkali is again added, owing 

 to rapid death the cells will appear quite at rest, as if 

 there had been no agent to cause cell-division in the 

 jelly at all. But the granules and nucleoli will be 

 deeply stained, and the polymorphonuclear cells will 

 probably all be burst and achromatic. 



When first we showed the mitotic figures to some of 

 our friends we received some adverse criticisms. It is 

 always possible to induce mitosis in lymphocytes, but it 

 is not always possible, at a few minutes' notice, to find 

 figures which resemble the diagrammatic drawings of 

 mitosis in the cells of plants and the lower animals as 

 given in the text-books on cytology. However, when 

 a convincing figure did appear, the nature of the 

 chromosomes, the spindle, and the centrosomes were 



