478 



Col. Sir D. Bruce and others. Trypanosome [May 13, 



months, they remained negative. Stomoxys are so numerous in every part of 

 the country all the year round that it seems inconceivable that they can act 

 as carriers. From October, 1908, until the following September, although 

 numerous cases of cattle with Trypanosoma pecomm in their blood grazed all 

 day long with healthy cattle, yet not a single case of infection took place. 

 The Stomoxys were exceedingly numerous all this time, forming a small 

 cloud of flies round the cattle, and passing constantly from one animal 

 to another, being driven hither and thither by the rapidly-swishing tails. 

 This is a natural experiment on a large scale. 



It will therefore require very convincing proof to bring this Commission to 

 the belief that Stomoxys are carriers of this disease. 



The subject of the carrier of Trypanosoma pecor^im must remain in this 

 unsatisfactory state for the present, but it is hoped that experiments which 

 are at present being carried out at Mpumu may throw some light on this 

 important part of the subject. 



Cultivation of Trypanosoma Pecoeum. 



One difficulty experienced at Mpumu in attempts to cultivate the various 

 trypanosomes was that rabbits were not available to supply the blood for 

 Novy and MacNeal's medium. The blood of rats, goats, and oxen was used ; 

 but in making the cultivation of trypanosomes a factor in their diagnosis 

 uniformity must be of the first importance. 



Another difficulty was the frequency of contamination of the tubes. This 

 was, perhaps, to be expected in a laboratory on the top of a hill in the 

 tropics, with very free ventilation. 



Trypanosoma pecorum grows fairly readily on blood-agar medium. At the 

 end of 24 hours clumps may be seen containing many trypanosomes, with 

 their flagellar ends directed outwards and in active motion (Plate 12, fig. 1). 

 The individual flagellates have irregularly-shaped granules of chromatin 

 scattered through their body substance, and also many brightly-refractile 

 vacuoles. After 48 hours' culture every field contains many active trypano- 

 somes, and also small clumps composed of 10, 20, or more members 

 (Plate 12, fig. 2). 



After six days the trypanosomes arc still very active ; they vary mucli 

 in size and shape, from the plasmodial to the elongated, flagellated, highly 

 active trypanosome. After this tliey .seem to degenerate, and in a few days 

 living tryj)anosonies can no longer be found in tlie tube. 



This description approaches to some extent that of the cultural characters 

 of Dr. Edington's trypanosome from Zanzibar and Trypanosoma dim orphon, 

 but tliere is not that extraordinary growtli which was described as covering 



