COLLECTION, CULTIVATION, OBSERVATION 711 



Intestinal Protozoa of man are usually studied in the faeces of an 

 infected person. Natural movement should be collected. Do not use 

 oily purgatives in obtaining faecal specimens, as they make the 

 microscopical examination difficult by the presence of numerous oil 

 droplets. The receptacle must be thoroughly cleaned and dry, and 

 provided with a cover. Urine or water must be excluded completely. 

 The faeces must be examined as soon as possible, since the active 

 trophozoites degenerate quickly once leaving the human intestine. 

 If dysenteric or diarrhoeic stools are to be examined, they must not 

 be older than one hour or two. In case this is not possible, wrap the 

 container with woolen cloth while transporting and keep it in an in- 

 cubator at 37°C. The organisms may live for several hours. Care 

 must however be exercised during the microscopical examination, as 

 there will be present unavoidably a large number of degenerating 

 forms. If the stool is formed and normal, it would contain usually 

 encysted forms and no trophozoites if the host is infected by a 

 protozoan, unless mucus, puss, or blood is present in it. Examination 

 of such faeces can be delayed, as the cysts are quite resistant. 



Cultivation 



For extensive study or for class work, a large number of certain 

 species of Protozoa are frequently needed. Detection and diagnosis 

 of human Protozoa are often more satisfactorily made by culture 

 method than by microscopical examination of the collected material. 

 Success in culturing Protozoa depends upon several factors. First an 

 abundant supply of proper food material must be made available. 

 For example, several species of Paramecium live almost exclusively 

 on bacterial organisms, while Didinium and allied ciliates depend 

 upon other ciliates as sources of food supply. For cultivating chroma- 

 tophore-bearing forms successfully, good light and proper kinds and 

 amount of inorganic substances are necessary. In the second place, 

 the temperature and chemical constituents of the culture medium 

 must be adjusted to suit individual species. As a rule, lower tempera- 

 tures seem to be much more favorable for culture than higher tem- 

 peratures, although this is naturally not the case with those parasitic 

 in homoiothermal animals. Furthermore, proper hydrogen ion con- 

 centration of the culture must be maintained. In the third place, both 

 Protozoa and Metazoa which prey upon the forms under cultivation 

 must be excluded from the culture. For instance, it is necessary to 

 remove Didinium nasutum in order to obtain a rich culture of Para- 

 mecium. For successful culture of Amoeba proteus, Aeolosoma, Daph- 

 nia, Cyclops, etc., must be excluded from the culture. 



