722 PROTOZOOLOGY 



more abundant and the inclusion body smaller. Dividing forms ap- 

 pear peanut-shaped. 



In a number of parasitic Protozoa, there occur foreign organ- 

 isms which may be mistaken for food inclusions or chromatin. 

 They are vegetable organisms which were named by Dangeard 

 as Sphaerita and Nucleophaga (Fig. 335, 1,2). The former occurs 

 in the cytoplasm and the latter in the nucleus of the host protozoan. 

 These parasites are spherical and about 0.5-1^ in diameter; they 

 are found most frequently in spherical masses composed of vary- 

 ing numbers of individuals. Nucleophaga appears to destroy the 

 host nucleus. Degenerating epithelial cells or leucocytes (Fig. 335, 7, 

 8) may simulate parasitic amoebae. Fishes and birds are often in- 

 fected by Coccidia and when they are consumed as food, the oocysts 

 pass the alimentary canal unchanged and appear ,in the stools. 



The cysts of intestinal Protozoa are, as a rule, distributed through- 

 out the formed faeces and difficult to detect in small portions of the 

 voided specimens. Flecks of mucus in the fluid stool obtained by use 

 of a saline purge may contain more numerous cysts than naturally 

 passed one. Several methods for concentrating cysts for microscopi- 

 cal examination are known. The simplest one is to emulsify thor- 

 oughly a small mass of faeces about the size of a lump sugar in a 

 mortar by adding a small amount of once-boiled tap water. Add to 

 it about 500 cc. of water and pour the whole emulsion into a glass 

 cylinder, and let it stand for about 15 minutes. Remove the scum 

 floating on the surface and draw off the turbid fluid into another 

 cylinder, leaving the sediment and a little fluid just above it un- 

 touched. The majority of cysts are suspended in the drawn-off por- 

 tion of the emulsion. Centrifuge the fluid, pour off the supernatant 

 fluid and add water. Centrifuge again. Repeat this three times until 

 the supernatant fluid becomes clear. The sediment will be found to 

 contain more numerous cysts than small sample specimens. 



B. Permanent preparations 



Permanent preparations are employed, as was stated before, to 

 supplement, and not to supplant, fresh preparations. Smear prepa- 

 rations are more frequently studied, while section preparations are 

 indispensable in extensive studies of Protozoa. 



a. Smear preparations 



Smears are made either on coverglasses or slides. However, cover- 

 glass-smears are more properly fixed and require smaller amount of 

 reagents than slide-smears. Greater care must be excerised in han- 



