INTRODUCTION. 49 



dilute the stain with double the volume of diluted Giemsa's 

 stain, one drop to each c.c. of water, and mix thoroughly. 

 Differentiate in distilled water, as in the ease of Leishman's 

 stain. 



Thick Blood-films. — The thick film method is specially 

 applicable to those cases in which the patient has already taken 

 a small dose of quinine and the malarial parasites are apt to 

 be missed in thin films. Knowles (1928) recommends taking 

 three thin films and one thick one from every suspected case 

 of malaria. The thin films are stained and examined whilst 

 the thick film is drying, and if no parasites are detected in the 

 thin films the thick film may be proceeded with. Knowles 

 and Das-Gupta (1924 a) advocate the following method for 

 preparing thick films : — Take a perfectly clean shde, prick the 

 patient's finger, and bring the slide into contact with the 

 issuing blood so that four drops are placed at the corners of 

 a small square about half an inch across. The drops should 

 not be too large nor too small. With a round needle pool 

 the four drops so as to spread the film into an even thick film 

 covering the half -inch square. Puddling should be avoided 

 and the film must not be made too thick. The film should be 

 kept covered, and will take about two hours to dry. Lay the 

 shde on a staining rack and dehsemoglobinize the film by 

 gently flooding the shde with a mixture of 2-5 per cent, 

 solution in distilled water of glacial acetic acid, 4 parts, and 

 2 per cent, solution in distilled water of crystalline tartaric 

 acid, 1 part. The dehsemoglobinized film should have a grey- 

 white colour. As soon as the process is complete drain off 

 the fluid by gently tilting the shde. Next flood the shde with 

 methyl alcohol and allow it to remain on for 3 to 4 minutes. 

 Drain off the methyl alcohol and wash the film thoroughly in 

 distilled water so as to remove every trace of acid. Stain with 

 diluted Giemsa's stain, one drop to each c.c. of water, for 

 15 minutes or longer. Differentiate in the usual way with 

 distilled water. Do not blot the film, but let it dry by 

 slanting it against a vertical surface. 



SPOR. 



