56 MANUAL OF HUMAN PROTOZOA 



oil immersion objective should be used to make out finer 

 details. 



The objectives used depend upon the training and ex- 

 perience of the one who carries on the examination. A low 

 power objective must be used as far as possible. The lower 

 the magnification, the brighter and the larger the field. 

 The success of examination depends almost entirely on 

 continued practice, since the faecal matter contains myri- 

 ads of objects which may resemble protozoa that them- 

 selves may quite often be at various stages of degeneration 

 and disintegration. Experienced observers can recognize 

 most of the protozoa described in the preceding pages 

 easily in a low power objective field. 



It is important to examine the fresh preparations care- 

 fully and thoroughly. If no protozoa here mentioned are 

 found, make several more preparations from different parts 

 of the specimen and examine. Often it is necessary to 

 obtain and examine specimens on several successive days 

 from a person, before a positive or negative diagnosis can 

 clearly be established. Remember demonstration of either 

 the trophozoite or the cyst is absolutely necessary for a 

 positive diagnosis of a protozoan parasite. 



The flagella of the actively moving flagellates are difficult 

 to recognize in an ordinary bright field, but the peculiar 

 movement in combination with the finding of certain struc- 

 tures such as cytostome, undulating membrane, etc., will 

 suggest that the organism is flagellated. In order to see 

 actively moving flagella, a dark field condensor is neces- 

 sary. Rut when this is not possible, treat the specimens with 

 LugoFs solution (p. 57). 



The cysts are as a rule distributed throughout the formed 



