water carefully over the slide from one end, out of a measur- 

 ing glass. A white streak will be left, consisting of leucocytes, 

 the stroma of the erythrocytes and the thrombocytes. 



This tap-water is drained off and the slide is left to dry 

 resting obliquely against some object. The film must be 

 quite dry before staining is attempted, otherwise it may be 

 washed away in the process. 



The slide is now laid horizontally and flooded with a 

 mixture of 2 drops of Giemsa stain in 2 c.c. of water. The 

 water used for this purpose must not contain algae, water 

 bacteria or the like; its pH must be about 7. Sometimes or- 

 dinary tap-water can be used, but often it is necessary to 

 make use of a phosphate buffer solution (can be bought 

 from stock) or of a 1/1000 magnesium sulphate solution. 

 For this purpose a clean 10 c.c. measuring glass should be 

 used after it has been rinsed with the buffer solution; after 

 use it is again rinsed and put away filled with water of a 

 neutral reaction. This glass should never be used for any 

 purpose other than staining and never be cleaned except by 

 rinsing with the buffer solution. 



The staining fluid should be allowed to remain on the 

 film for from 20 or 40 minutes to one hour, as indicated by 

 previous experience in staining. The following factors affect 

 the result: 



Temperature. The best temperature is about 37° C. If the 

 temperature is lower the process takes longer. 



Concentration of the stain. The greater the concentration, 

 the deeper and more rapid the staining, but it is accom- 

 panied by precipitation and unrecognizably over-stained 

 leucocytes and plasmodia. In general it may be said that a 

 long immersion in a highly diluted stain gives the best re- 

 sults, but of course there is a limit beyond which this is not 

 the case. The slide should not be left in the stain for less than 

 twenty minutes! If after this period the slide is too strongly 

 colored, this may be taken as an indication for further dilu- 

 tion of the stain on the next occasion. 



Duration of coloring process. This depends on the tern- 



