74 THE ANIMAL PARASITES OF MAN 



shaped. The undulating membrane is thrown into folds and is 

 bordered by the fiagellum. A small basal granule may be present 

 near, or at the actual origin of the flagellum. 



Multiplication in the vertebrate is brought about by longitudinal 

 division. According to the recent account of division by Miss 

 Robertson, the blepharoplast doubles, then the flagellum splits for the 

 greater part of its length, and the daughter flagella separate, one being 

 shorter than the parent flagellum. The nucleus often shows two well 

 marked dark granules on the membrane at opposite poles, and these 

 appear to act as centrosomes. Nuclear constriction occurs and the 

 halves gradually separate. Finally the two daughter organisms become 

 free, the aflagellar end splitting last. The products of division may be 

 equal or unequal. Repeated division goes on in the general circulation 

 until the blood swarms with parasites. Then the trypanosomes gradually 

 disappear, and a period occurs when it is practically impossible to 

 demonstrate the parasite in the blood. At such a period, trypanosomes 

 can be obtained by puncture of the enlarged lymphatic glands or of 

 the spinal canal, or can be found in the internal organs, more particu- 

 larly in the spleen, lungs, liver and bone-marrow. In the latter 

 organs, latent bodies are produced (fig. 29, d /) which are capable of 

 again becoming flagellates and entering the general circulation. 

 Their formation was described by Fantham (191 1). 1 The parasite 

 contracts, the blepharoplast migrates towards the nucleus, a very thin 

 coat differentiates around the two nuclei and a certain amount of cyto- 

 plasm, and the parts exterior to the coat disintegrate, leaving a small, 

 oval body behind. Fuller details are given in connection with 

 T. rhodesiense. Laveran (191 1) 2 considers that latent bodies are 

 " involution " forms, but acknowledges that they can flagellate and 

 become infective in fresh blood. 



No multiplication of the trypanosomes w 7 ithin the cells of the 

 lung, liver or spleen of infected monkeys was found by Miss 

 Robertson in her recent researches. 



There appear to be negative periods in infected monkeys, since, 

 although trypanosomes may occur in their blood at such times, they 

 are not infective to Glossina. 



Development in Glossina palpalis. The principal accounts are 

 those by Sir D. Bruce and his colleagues (19 n), 3 and by Miss 

 Robertson 4 (1912), whose results will be followed. According to the 

 latter investigator T. gambiense never enters the body cells of the fly 

 (G. palpalis), nor does it penetrate the gut wall into the body cavity. 

 Practically no crithidial stage occurs in the fly's main gut, but a 

 trypanosome facies is retained therein. 



After the trypanosomes are ingested by the fly during a meal of 



1 Proc. Roy. Soc,, B, Ixxxiii, p. 212. '* C. R. Acad. Set., 153, p. 649. 



3 Proc. Roy. Soc., B, Ixxxiii, p. 513. 4 Froc. Roy. Soc., B, Ixxxvi, p. 66. 



