INTESTINAL FLAGELLATES OF MAN 31 



C. Intestinal Flagellates of Man 



1. Classification. The intestinal flagellates belong to the 

 class Mastigophora and are characterized by the presence 

 of one or more flagella. They are representatives of two 

 orders, (1) the Polymastigina and (2) the Protomonadina. 

 The Polymastigina possess from 3 to 8 flagella whereas the 

 Protomonadina have only one or two. Most of the impor- 

 tant species belong to the former. There is great need of 

 careful investigation of the intestinal flagellates since only 

 a few are known at all well, and many species have been 

 described and named but are not yet well established. The 

 best known forms are Giardia (Lamblia) intestinalis, Tri- 

 chomonas hominis, and Chilomastix (Tetramitus) mesnili. 

 These occur so frequently that they require more extended 

 treatment than those less well known. Among the latter 

 are Enteromonas hominis, Enibadomonas (Waskia) intestin- 

 alis, Tricercomonas hominis, Tetratrichomonas intestinalis, 

 Pentatrichomonas intestinalis, Oicomonas hominis, Cerco- 

 monas longicauda, and Prowazekia asiatica. 



2. Description of Species, a. Giardia (Lamblia) intestin- 

 alis (Plate IV, Fig. 6). Motile stage: When in the motile 

 stage this species is pear-shaped, from 10 to 21 microns long 

 and from 5 to 12 microns wide. The anterior half of the 

 organism bears a depression which acts as a sucking disk 

 for attachment to intestinal epithelial cells. Two nuclei, 

 one or two axostyles, and four pairs of flagella are present 

 as shown in the figure. Specimens in the motile stage are 

 not so frequently observed in feces as are the cysts. Rats, 

 mice and rabbits are often infected with what are probably 

 distinct species of Giardias and those who wish to gain a 

 preliminary knowledge of these organisms should examine 

 material from the duodenum of these animals. 



