THE TRYPANOSOMES 593 



A trypanosome has a slender, flexible, flattened body, one 

 extremity of which is pointed ; the other passes into a single 

 flagellum. A delicate undulating membrane runs along one 

 edge of the body. The organism lives in the plasma, in which it is 

 actively motile, the flagellated end being usually anterior, and 

 measures 15-30 p., or even 40-50 n, in length. The protoplasm 

 of the organism is finely granular, and near the centre of the body 

 is a large macronucleus, and generally between it and the non- 

 flagellated end is a smaller micronucleus or blepharoplast. 

 From the latter a chromatin filament starts, runs along the free 

 edge of the undulating membrane and passes into the flagellum. 

 Reproduction takes place by longitudinal division, occasionally 

 probably by transverse division, and amoeboid and plasmodial 

 masses may be found in the internal organs and bone-marrow. 

 The trypanosomes have great morphological similarity, which 

 renders them practically indistinguishable by structural char- 

 acters. They can usually be differentiated into three forms 

 indifferent, male, and female which in some cases may all 

 occur together, but only become fully differentiated in an inverte- 

 brate host. The males are slender, active, only slightly granular, 

 and with an elongated nucleus ; the females are bulky, sluggish, 

 granular, and have a rounded nucleus ; the indifferent forms 

 are intermediate. The males usually soon die off unless they 

 conjugate ; the indifferents are more hardy, the females most 

 so. The sexual forms conjugate in an invertebrate host, but if 

 the males have died off, both male and female forms may be 

 reproduced from the females by a process of parthenogenesis. 



Trypanosoma Gambiense 



In human trypanosomiasis and sleeping-sickness of 

 West and Central Africa, a trypanosome (Tr. Gambiense) 

 is the causative agent (Plate XXIV, a). It is usually 

 present, though scanty, in the blood, but can often be 

 found in numbers in the fluid aspirated from the enlarged 

 cervical glands. In the later stages, when cerebral symp- 

 toms ensue, it is found in the cerebro-spinal fluid, but 

 scantily, centrifuging being necessary in order to demon- 

 strate the parasites. The blood may give the Wassermann 



M.B. 38 



