PROTOZOA IN THE DIGESTIVE TRACT 41 



faeces or in culture media, but there is no evidence to 

 show that the flagellate ingests erythrocytes still in tissues. 

 This flagellate has not yet been observed in encysted 

 condition. What were considered cvsts vears ago, are now 

 known to be Blastocijstis hoininis (p. 69). Transmission 

 is obviouslv by the trophozoites, some of which have been 

 shown to withstand the gastric digestion and pass into 

 the small intestine alive. 



6. Trichomonas elongata Steinberg 1862 



Svnonvm: T. huccalis Goodev 1917 

 T. tenax (O. F. Miiller) 

 This flagellate is found in the human mouth, especially 

 in tartar, and in pyorrhoeic sockets. It has also been ob- 

 served in the sputum and pus of tonsils. Morphologically 

 it is similar to T. hominis, and therefore description given 

 for the latter will apply for the present species also. 

 Whether these two species and T. vaginalis (p. 108) are 

 identical or not, is still unknown, althoudi some of the 

 recent observations seem to indicate that T. hominis and 

 T. vaginalis are physiologically distinct species. As in T. 

 Jwminis, T. elongata is known only in the trophic stage. 

 Transmission is apparentlv bv the trophozoites which are 

 transferred in food or water or by direct contact to another 

 person. 



7. Giardia intestinalis (Lanibl 1859) 



Synonym: G. lamhlia Stiles 1916 



This is the most conspicuous flagellate of the human 

 intestine and seems to be the commonest one. It li\ es in 

 the duodenum and other parts of the small intestine. In the 



