136 PROTOZOAN PARASITISM 



The cysts of Giardia intestinalis and Chilomastix 

 mesnili may show m diarrhoeal or purged stool or 

 they may occur only in a natural formed stool. 

 Giardia cysts are commonly numerous; they are 

 ovoid, of ground glass appearance, reveal their inner 

 structure in iodine preparation, and are readily dis- 

 coverable. A small ovoid or slightly elongated 

 ^'ground glass" body which shows ^^eyes" (the nu- 

 clei) in one end on careful observation, is likely to 

 be a G /arc? ia cyst. 



Cysts of Chilomastix mesiiili are not nearly so 

 readily found. In diarrhoeal stool or purged speci- 

 men the trophozoite may be the only form. When 

 present in a natural stool their number is variable 

 and prolonged search may be necessary to find them. 

 They are smaller than Giardia cysts, are typically 

 pear or lemon shaped, are of uniform size, "ground 

 glass" appearance, and show in iodine preparation a 

 dot on one side anteriorly (the nucleus). They are 

 apt to be confused with yeasts by the inexperienced. 



Specimens stained by the iron-haematoxylon 

 method are necessary in case stools are not to be ex- 

 amined in a reasonable period of time. Stained speci- 

 mens are essential for study of the finer details of the 

 organisms, the flagella, the undulating membrane, 

 nucleus, food bodies, etc. For the inexperienced 

 such preparations are necessary for the identification 

 of the cysts. In carefully prepared specimens stain- 

 ing by the ordinary blood film methods, such as 

 Wright's or Leishman's, may give beautiful demon- 



