524 Sir D. Bruce and others. Trypanosome 



The Tkypanosomes Found in the Alimentary Tract. '• 



In this species of trypanosome the developmental changes which take place 

 in the intestine of G. morsitans are similar to those already described as- 

 occurring in the development of T. gambiense in G. palpalis* The latter 

 development has also been worked out very fully and completely by others.-]- 

 It is therefore unnecessary here to do more than refer to these previous 

 descriptions as being equally applicable to the species under consideration. 



In this species of trypanosome also, as in T. gambiense, it is only a small 

 percentage of the flies fed on an infected animal which become infected. In 

 one series of T. gambiense this was 8 per cent.| In this species the 

 experiments with laboratory-bred flies was 8 - 7 per cent., with wild flies 9 per 

 cent. Just as in T. gambiense, the development takes place in the alimentary 

 tract and salivary glands and not in the proboscis. 



The Trypanosomes Found in the Salivary Glands. 



In the trypanosome causing disease in man in Nyasaland, as in T. gambiense, 

 the crux of the whole matter is the invasion of the salivary glands. After a 

 certain number of days — in this species from 14 to 31 — the trypanosomes 

 reach the salivary glands and the fly becomes infective. 



Plate 24, figs. 3-28, represent the various stages in the development of this 

 trypanosome in the salivary glands. Figs. 1 and 2 are trypanosomes from the 

 proventriculus ; these represent the dominant intestinal type, from which the 

 salivary-gland types arise. It is still a matter of speculation as to how they 

 gain access to the glands, but as described in a former paper, § there is no 

 doubt they are often thrown forward into the proboscis during or. just in the 

 act of feeding, and may, under these conditions, be drawn into the hypo- 

 pharynx and so reach their destination. These proventricular forms, however, 

 have never been actually seen by the Commission in the hypopharynx. 

 Figs. 3-11 are forms found in the salivary glands. Many of these are 

 crithidial in type and occur in numbers. Figs. 12-14 are what appear to 

 be encysted forms. Figs. 16-21 are " blood forms " and occurred in large 

 numbers in the same preparation as the crithidial type shown in figs. 3-8. 

 Figs. 22-28 are " blood forms " which were thrown out on to a cover-glass by 

 a living infective fly. The preparation was beautifully clear, each individual 

 trypanosome standing out distinctly. Fig. 23 is from the same preparation 



* Ibid., B, vol. 83, p. 515 (1911). 



t Muriel Robertson, M.A., 'Phil. Trans.,' B, vol. 203 (1913). 



\ 'Boy. Soc. Proc.,' B, vol. 83, p. 514 (1911). 



§ Ibid., B, vol. 87, p. 65 (1913). 



