MASTIGOPHORA 



739 



The presence of cystic forms has been questioned, and two quite 

 different forms have been called resistance or dauer cysts. The earlier 

 one, described by Ucke (1908), Bohne and von Prowazek (1908), and 

 Benson (1910), is a fairly large body; showing a double contour and a 

 central homogeneous mass, perhaps food material, and an outer ring- 

 like body containing two or more nuclei. Brumpt and Alexieff believe 

 this form to be a fungus, having no relation to the trichomonad, and 

 have called it "Blastocystis hominis." Lynch 1 agrees with these au- 

 thors, and describes an altogether different body as the resistant form. 

 It is six by eight microns in size and perfectly symmetrical in shape. 

 The wall is distinct, and there is a clear space between it and the body 

 of the parasite. The nucleus, undulating membrane and flagella re- 

 main visible in the cyst, but Lynch was unable to detect any change 

 in the parasite indicating intracystic multiplication. 



Infection takes place probably by contact, and, as in typhoid fever, 

 food, fingers and flies carry the resistant forms from one individual to 

 another. Among the natives of tropical countries infection is almost 

 universal, but the parasites are rarely seen in the large cities of the 

 North. 



GENUS 2. Tetramitis mesnili (Wenyon, 1910). Macrostoma mes- 

 nili, Chilomastix mesnili, Fanapapea intestinalis. This organism, first 

 described by Wenyon, from a native of the Bahamas, differs from tri- 



chomonas by the possession of a deep groove 

 or cystotome, in which is found the undulat- 

 ing membrane. It is present in diarrheal dis- 

 charges, but its pathogenicity is doubtful. 



FIG. 167. LAMBLIA INTESTINALIS. Cyst formation. (After Doflein, "Lehrbuch der 



Protozoenkunde. ' ' ) 



GENUS 3. Lamblia intestinalis (Lambl, 1859). The lambia are 

 peculiar, bilaterally symmetrical, pear-shaped organisms, provided 



1 Lynch, Kenneth M., Jour. Parasite!., Urbana, 1916, iii, 28. 



