740 PATHOGENIC PROTOZOA 



with a sucking disk anteriorly. There are eight pairs of flagella, the 

 two posterior ones being continuations of longitudinal axostyles. The 

 nucleus is first dumb-bell shaped and later divided into two separate 

 nuclei. Cysts are found, and according to Schaudinn conjugation 

 occurs in them with the development of four nuclei. The young para- 

 sites attach themselves to the surface of epithelial cells of the small 

 intestine by the sucking disk, but even when present in large numbers 

 do not produce any characteristic symptoms. The same or like para- 

 sites are present in mice, rats, dogs, cats, and sheep. Transmission is 

 by contact, as in trichomonad infections. 



ORDEK II PROTOMONADINA 



The Protomonadina, another order of the Flagellata, have less than 

 three flagella, and are divided into the Cercomonadidce, Bodonidce and 

 the Trypanosomidce. 



GENUS 1. Cercomonadidse Cercomonas hominis (Davaine, 1854). 

 As originally described, this organism has a pear-shaped body, 

 drawn out to a point posteriorly, is armed with a single flagellum in 

 front, and has no undulating membrane. It is a doubtful species and 

 of no present importance. 



GENUS' 2. Bodonidse Prowazekia (Hartmann and Chagas). 

 These organisms, the only examples of the Bodonidce of medical inter- 

 est, are of some importance, since they have been cultivated from hu- 

 man feces on agar plates. The genus was founded for Prowazekia 

 cruzi, a species discovered in human feces in Brazil. Other species are 

 urinaria, asiatica. parva, weinbergi and javanensis. There are two 

 flagella, arranged in the heteromastigote manner, that is, one flagellum 

 projects forward and one trails behind. There is no undulating mem- 

 brane, but in stained specimens a 'second nucleus is seen, the kineto- 

 nucleus or blepharoplast. They are also found in water, and are 

 probably not the cause of any disease. 



GENUS 3. Trypanosomidae. History of the genus. In 1841 Val- 

 entine discovered the first hemoflagellate in the blood of a trout, and 

 the following year Gruby described a flagellate in frog's blood and 

 named it a "trypanosome." It was not until 1878 that Lewis discov- 

 ered the rat trypanosome, Trypanosoma lewisi. The first pathogenic 

 member of the genus was noted by Evans in 1889 in the blood of In- 

 dian horses sick with surra, Trypanosoma evansi. Bruce in 1894 de- 

 scribed the trypanosome of Nagana, a horse disease of Zululand, and 



