46 



Sir D. Bruce and others. Infectivity of 



It will be seen from the above table that 60 attempts to determine the 

 infectivity of the flies were made by injecting emulsions of the infected 

 organs into healthy animals. In only three cases did the animals become 

 infected : once with Trypanosoma simice and twice with T. hrucei vel 

 rhodesiense. The usual experiment was to inject the contents of the 

 intestine into dogs or goats, which is known now to be useless, as the 

 developmental forms in the intestine are not infective. Doubtless more 

 positive results could be got at present with more knowledge of the laws 

 which govern infectivity. Only in two cases were the salivary glands found 

 to be invaded. This infection, of course, could only be T. hrucei vel 

 rhodesiense, and this was confirmed by injecting the glands into rats. 



In 1912 no attempt was made to diagnose directly the species of trypano- 

 somes with which the flies were infected, but in 1913 this was done, as by 

 that time a good deal of experience had been gained. For example, invasion 

 of the salivary glands could only be T. brucei vel rhodesiense ; invasion of the 

 intestine, labial cavity and hypopharynx meant T. pecorum or T. simiaz, and 

 size would distinguish between the two. Lastly, if only the labial cavity 

 and hypopharynx were seen to contain flagellates, then T. caprw was 

 indicated, and here also the size and character of the trypanosomes in the 

 hypopharynx would assist in the diagnosis. 



Table II— 1913. 





Proboscis. 









No. of fly. 







Intestine. 



Salivary 



Species of 







glands. 



trypanosome. 





Labial cavity. 



Hypopharynx. 







1 



+ 





+ 





T. pecorum. 



2 



+ 









T. vaprce. 



3 



+ 









a 



4 



+ 









it 



5 



+ 





+ 





T. simice. 



6 



+ 









T. caprm. 



7 





+ 



+ 







8 







+ 







9 



+ 





+ 





T. simice. 



10 



+ 









T. caprce. 



11 



+ 









:> 



12 







+ + 







13 







+ 







14 







+ 







15 



+ 





+ + 





T. simice. 



16 



+ 





+ 







17 



+ 









T. caprce. 



18 



+ 



+ 



+ 





T. pecorum. 



19 



+ 





+ 







20 



+ 





+ 







21 







+ + 



+ 



T. brucei. 



22 







+ 







23 



+ 









T. caprce. 



