64 



Sir D. Bruce and others. Trypanosome 



trypanosomes attached to the labrum were seen growing in colonies in the 

 labial cavity. They were moving freely and some detached individuals were 

 swimming actively up and down the lumen of the tube. 



It is to be regretted that the contents of the hypopharynx were not 

 specially noted. These were two of the earliest experiments, and at that time 

 the contents of the labial cavity and the hypopharynx were not differentiated. 



In Experiment 1847 seven infected flies were found. It will observed 

 (Table VI) that the first was dissected on the 16th day after the last infected 

 feed and that the proboscis was not infected. Another fly dissected on the 

 32nd day had also no infection of the proboscis. A third fly dissected on the 

 31st day had the labial cavity of the proboscis infected but not the hypo- 

 pharynx. The remaining four were found to contain swarms of trypanosomes 

 in both the labial cavity and the hypopharynx. On examination it was 

 observed that there were two distinct varieties. One found in the hypo- 

 pharynx closely resembled small blood forms of T. simice (Plate 8. figs. 18 

 to 21). They swarmed in the narrow tube, which had the appearance of being 

 blocked up by their enormous numbers. These small blood forms of the 

 parasite were readily distinguishable from those growing in the labial cavity. 

 Those growing in the labial cavity resemble Lcptomonas, and are peculiar in 

 having their non-flagellated extremity prolonged to a snout-like extension 

 (Plate 8, figs. 12 to 16). They are assembled in clusters and attached by 

 their flagella to the inner surface of the labrum, their prolonged free extremity 

 moving vigorously in the lumen of the tube (Plate 6, fig 1). 



The contents of the hypopharynx of a living infective fly isolated from 

 Batch 2 was examined by inducing the fly to salivate on a cover-glass as 

 described above. On examination of the stained preparations typical blood 

 forms of T. simice were seen embedded in the saliva which the fly had ejected 

 on the cover-glass in its efforts to reach the skin (Plate 8, figs. 22 to 25). 

 Another infective fly was taken alive from its glass tube and its proboscis 

 gently squeezed until a minute drop of fluid was observed at its tip, which 

 was then lightly rubbed over a cover-glass. Here again typical blood forms 

 of T. simice were found embedded in the salivary secretion (Plate 8, figs. 26 

 to 29). 



In Experiment 1847 it is seen that a positive result is associated with the 

 finding of infected flies in which T. simice resembling those found in the 

 blood of infected animals are found in large numbers blocking up the tube of 

 the hypopharynx. 



The experiment of tempting the infective fly to feed through a cover-glass 

 demonstrates the fact that when the fly salivates, as it undoubtedly does in 

 puncturing the skin, these blood forms of the parasite are washed out of the 



