146 RESEARCH IN PROTOZOOLOGY 



OBTAINING MATERIAL 



The easiest method of obtaining specimens of Giardia lamhlia 

 for study is to secure fecal samples from a number of persons, 

 especially those suffering from diarrhea. Thin smears made up 

 with 0.7% NaQ should reveal cysts or trophozoites if pres- 

 ent. Cysts in the living condition are very easy to identify. They 

 are oval in outline, average about ten microns in length and seven 

 microns in breadth and are characterized by the presence of sev- 

 eral curved lines which may be seen extending through the proto- 

 plasm in a more or less longitudinal direction. The trophozoite can 

 hardlv be confused with any other type of organism that occurs 

 in human feces. As shown in Fig. 14, they are broad, have a large 

 sucking disc on the ventral surface and a pointed tail. They roll 

 over and over in the medium without making much progress. 



Cysts of the giardias of rats and mice, as already mentioned, 

 may be obtained from the fecal pellets of these animals and 

 trophozoites in the more liquid feces as the result of treatment 

 with Epsom salts. The normal habitat of Giardia is the duodenum. 

 Here in freshly killed animals trophozoites will be found in mate- 

 rial squeezed out of a section of the duodenum on a sHde and 

 diluted with 0.7% saline solution, or in material from scrap- 

 ings of the inner surface. If small pieces of the duodenum of a 

 heavily infected animal are fixed in Bouin's or Zenker's solutions 

 and cross sections made, giardias will be found in the crypts cling- 

 ing to the epithelial cells with their sucking discs. The giardias of 

 the other animals mentioned may likewise be secured either in the 

 feces or in material taken from the duodenum of the freshly killed 

 host. Specimens in various stages of encystation may be found in 

 the jejunum, ileum, cecum and colon. 



PREPARATION FOR STUDY 



Cysts and trophozoites of the giardias available may be fixed 

 in smears with Schaudinn's solution and stained with iron-hema- 

 toxylin. When prepared in this way they exhibit the various struc- 

 tures shown in Fig. 14. 



Unfortunately giardias are among the few human protozoa that 

 have never been cultivated in artificial media. Many attempts to 

 do so have been made by a number of investigators in the writer's 

 laboratory but thus far without success. It is very important that 



