CA STELLA NELLA RHODESIENSIS 



425 



twelfth and twentieth day, after which they pass along the hypo- 

 pharynx into the salivary glands. Here they ^become attached to 

 the walls and are converted into crithidial forms, which divide, form- 

 ing small trypanosomes similar to those found in the blood of the 

 vertebrate. The salivary gland development requires two to five 

 days before the fly becomes infective, which only happens in about 

 8 per cent, of flies. The duration of the life-cycle in the fly depends 

 upon the air temperature. 



^•vs Vertebrate Reservoir. — ^Dukejconsiders^that he has proved that 

 the Sitatunga antelope is a reservoir for this trypanosome, and 

 considers that the infection of two boys working on the uninhabited 

 islands of Victoria Nyanza and constantly exposed to bites of G 

 palpalis is confirmatory. 



Pathogenicity. — -It is the cause of one form of sleeping sickness. 



Castellanella rhodesiensis (Stephens and Fantham, 1910). 



Synonym. — Trypanosoma rhodesiense Stephens and Fantham, 1910. 



History. — In 1910 Stephens and Fantham advanced the view that 

 the trypanosomes found in cases of sleeping sickness in the Luangeva 

 Valley in Rhodesia belonged to a new species, because the tropho- 

 nucleus of a certain percentage of short forms was situate either close 

 to or even on the aflagellar side of the kinetonucleus. This view 

 is at the present time accepted by the majority of authorities, 

 although there are some who maintain that it is a variety of C. brucei, 

 in which similar forms have also been seen. The animal reactions 

 of the new trypanosome were studied by Yorke in 1910, Bevan in 

 1911, and more recently by other observers. In 1912 Kinghorn 

 and Yorke showed that this trypanosome was transmissible by 

 Glossina morsitans, in which it -underwent development. They 

 demonstrated that it occurred in waterbuck, hartebeest, impala, 

 and wart-hogs, as well as in native dogs, and they further showed 

 the importance of atmospheric temperature on the length of time 

 required for the cycle of development in the fly. 



Morphology. — C. rhodesiensis closely resembles C. castellanii in 

 general appearance. It has a length varying from 12 to 31 

 with an average of 21-5 and shows the usual pleomorphic 

 forms — e.g., short stumpy forms varying from 13 to 21 [^ in length; 

 intermediate forms, 22 to 24 l^ in length; and long, slender forms 

 ,25 or more in length. The most common are the long, slender 

 forms. The position of the trophonucleus is variable, but it is 

 usually situate towards the aflagellar end of the parasite, and in 

 the short stumpy forms is often close to the kinetonucleus, or even 

 on its aflagellar side. 



Life-History. — (a) In the Vertebrate longitudinal division can 

 take place as in C. castellanii. About the time that trypanosomes 

 are most numerous in the blood the researches of Fantham show 

 that some forms in the lungs become converted into latent bodies 

 by disintegration and loss of the flagellar end, followed by a migra- 

 tion of the kinetonucleus towards the trophonucleus, and a sub- 



