DETECTION AND IDENTIFICATION 55 



Fresh preparation 



If the faeces is cl\ seiiteric, a small portion is placed by 

 a toothpick or platinum loop on a slide and covered with 

 a cover-glass. Before placing the cover, all large particles 

 must be removed so that the smear preparation will be 

 uniformh' thin. If the faeces is diarrhoeic, then the smear 

 is made in a similar manner. But if the faecal specimen 

 is semiformed or formed, a small drop of warm (37 C.) 

 0.85^ sodium chloride solution which has been boiled be- 

 forehand, is first placed on the slide, and by means of a 

 toothpick, a small portion of the faeces, particularly mu- 

 cus, pus, or blood, is emulsified in it and a cover is placed 

 o\'er the whole. The smear should not be too thick or 

 too thin for a satisfactorv observation. If the smear is too 

 thick, it will be impossible to distinguish objects clearly, 

 and on the other hand, if it is too thin, there will unavoid- 

 ablv be a great deal of time lost in detecting widely scat- 

 ered protozoa. The optimum thickness of the smear is one 

 through which the print on this page can be read. 



Place the preparation on the stage of the microscope and 

 examine with a moderately low power objective, by mo\ ing 

 the slide svstematically by hand or by a mechanical stage. 

 Recognize the active tiophozoites bv the refractility and 

 the change in bod\' form or movement, and in case of cysts 

 by their form and size. The determination of the size of a 

 microscopical object can be done quickly and easily, if 

 ocular micrometer divisions have been calculated in 

 combination with different objectives. When trophozoites 

 or cvsts are recognized, examine them one h\ one under 

 a high dry objective, and identify them. If necessar\ , an 



