THE PATHOGENIC PROTOZOA 175 



solution of sodium carbonate; but in order to obtain 

 growth,* it is necessary to use an agar medium, and supply 

 the organisms with living bacteria. In the faeces spore 

 formation takes place. The disease is supposed to be 

 spread by drinking water and raw foods. Jordan says 

 that sand filtration will not remove Amoebae from water. 



The Trypanosomes. 



The trypanosomes have a somewhat elongated eel-like 

 form, the average length being from 20 ft to 35 IJL. They 

 belong to the Flagellata class of the Mastigophora division 

 of the Protozoa. The description of T. Brucei given below 

 is with slight modifications accurate for other species. 

 Trypanosomes have no mouth, nutrition being effected 

 by the imbibition of soluble nutrient material. When 

 living they move rapidly about in the fluids of the body, 

 being propelled by a flagellum, by the undulations of 

 a fin-like structure the undulating membrane and by 

 alternate contractions and relaxations of the body proto- 

 plasm. They reproduce by a simple longitudinal division. 

 While some authorities aver that no true conjugation 

 has been discovered, others differentiate a bulky, granular, 

 slow-moving organism as the female, and a slender, 

 active one as the male. These sexual types are said to 

 conjugate in the Glossina or other invertebrate host and 

 a transitional form between the male and female varieties 

 is regarded as an indifferent form, or as a daughter cell 

 split off from a fertilised female. 



Trypanosoma Gambiense is found in the glands, cerebro- 

 spinal fluid, and blood in sleeping sickness. The organism 

 is conveyed by a tsetse-fly * (Glossina palpalis), which 

 feeds on an infected being, and conveys the trypanosome 

 in its alimentary canal till it bites a healthy subject 

 (frequently on the back of the neck), and thus causes 

 infection. An exogenous cycle appears to take place 

 in the gut of the fly, involving differentiation into sexual 

 types and fertilisation of the female. The fly remains 

 infective after feeding on infected blood for ninety-six 

 days, and possibly for entire life. Glossina palpalis does 



* Tsetse-flies belong to the same order as the house-fly (Musddce), 

 which they resemble in general aspect, but when at rest the wings fold 

 completely over each other, like the blades of a pair of scissors. The 

 flies are viviparous, extruding single annulated adult larvce. 



