278 THE DIVISION OF LEUCOCYTES 



It is necessary to employ the photomicrographic 

 apparatus which I have already described, and the 

 photographs must be taken with as little delay as 

 possible after the cells have been ruptured. Unfixed 

 cells may rapidly become achromatic after death, and, 

 in the case of a ruptured cell, the loss of stain may 

 occur with great rapidity. 



The blood of the person to be examined is drawn 

 into a capillary tube and there mixed with an equal 

 volume of citrate solution. At the room tempera- 

 ture this solution will keep the cells alive for some 

 days; but when it is intended to count the granules of 

 the eosinophile leucocytes, it is better to examine the 

 blood as fresh as possible. 



A jelly is prepared thus: To a tube containing 

 5 cc. of coefficient jelly add 4 units of TJnna's poly- 

 chrome stain, 7 units of the 5-per-cent alkali solution, 

 and, instead of making the contents of the tube up 

 to a total of 10 cc. with water, 3.9 cc. of a molten 

 2-per-cent solution of agar in water is used. The 

 last solution contains agar in order to make the jelly 

 exceptionally firm, so that the ultimate bursting of the 

 cells can be facilitated. The jelly is melted and boiled 

 and a drop of it run on to a slide, where it is allowed 

 to set. A drop of the citrated blood is then placed 

 on a cover-glass, which is inverted and allowed to fall 

 flat on the film in the usual way. The slide is then 

 placed in the 37 C. incubator for three minutes exactly. 

 When examined microscopically it should be seen that 

 the nuclei of the eosinophile leucocytes are just staining 

 scarlet, showing that death is occurring; the granules 



