100 MANUAL OF HUMAN PROTOZOA 



medicine dropper, cover the dried blood film widi drops 

 of undiluted Wright's stain, and let the film stand hori- 

 zontally for 3-5 minutes; then the same number of drops 

 of neutral distilled water is added to the stain and the 

 whole is left for 10-30 minutes. The stain is then poured 

 off and the film is rinsed in neutral distilled water. Drv. 

 Mount in xylol and cedar wood oils as stated for Giemsa's 

 stain. 



Use of cover-glasses on a stained blood film is advocated, 

 since a cedar wood oil mounted slide allows the use of dry 

 objectives which in the hand of an experienced worker 

 would give enough magnification for species determina- 

 tion of Plasmodium, and which will very clearly reveal any 

 trypanosome present in the film. Furthermore the film is 

 protected against scratches and contamination by many ob- 

 jects which may bring about confusion in detecting pro- 

 tozoa. 



The splenic pulp smears for Leishmania and Trypano- 

 soma are also similarly treated and prepared. 



When the parasites are very few in the blood, the thick 

 film is highly useful for detection of ring forms and gameto- 

 cytes of Plasmodium and of trypanosomes, as the organ- 

 isms are much concentrated, and the haemoglobin is com- 

 pletely absent. On the other hand, the thick film brings 

 about a great deal of abnormalities in the organism so that 

 many of the specimens may be variously distorted. There- 

 fore, species identification is usually difficult. Thick films 

 should be used for detection of organisms and identifica- 

 tion should be made on thin films. 



In diagnosis of Trypanosoma and Leishmania, it is neces- 

 sary often to use culture method. The oldest medium is 



