54 MANUAL OF HUMAN PROTOZOA 



ber of sluggishly moving individuals as well as degenerat- 

 ing ones. 



The faecal specimen should be quickly examined with 

 the naked eye. If it is formed, it should be examined 

 mainly for the encysted form. If mucus, pus, or blood is 

 present in the specimen, examine it for active trophozoites. 

 In diarrhoeic or dysenteric faeces, one should look for 

 trophozoites and occasional cysts. 



Microscopical examination 



Microscopical examination of the faecal matter is con- 

 ducted as far as possible on fresh material, but in making 

 out certain body structures which enable one to identify 

 the protozoan under observation, permanent preparations 

 are also necessary. 



The microscopic slides of standard size, 3'' by V\ should 

 be of white glass and preferably thin, about 0.75 mm. 

 thick (No. 1). For dark field illumination thin slides are es- 

 sential. No. 1 cover-glasses should only be used for both 

 fresh and permanent preparations. They are about 0.13- 

 0.17 mm. thick. The most convenient size is about Is' 

 square covers, which are preferred to circular ones. The 

 slides and cover-glasses must be cleaned thoroughly before 

 being used. Immerse them in a concentric mineral acid 

 (nitric acid is best fitted) for about 10 minutes. Pour off 

 the acid, wash the slides and covers for about 10 minutes 

 in running water, rinse in distilled water, and keep them 

 in 90-95% alcohol. When needed they are dried one by 

 one with clean cheesecloth. Handle slides and covers 

 with a pair of forceps. If thumb and fingers are used, 

 hold them by edges or ends. 



