1910. | as Carriers of Trypanosoma pecorum. 355 
The normal calves and the control calf were examined bi-weekly for 
trypanosomes throughout the experiment, and for one month after its 
completion. The infected calf was also examined bi-weekly ; Trypanosoma 
pecorum were always seen in its blood; sometimes they were present in large 
numbers, sometimes scanty. — 
Table I gives the result of these experiments at a glance. 
Table I. 
: : No. s Approximate 
Species of Tabanus | Experiment eg eey | No. of aa | Resale 
used. No. of calves. f ’ 
| ed on calves. used. | 
Tabanus secedens | 23804 & 2305 30 1500 Negative ; calves re- 
(Walk.) mained healthy. 
Tabanus fuscomargi- | 2400 & 2401 43 2150 % 5 
natus (Ricardo) | 
Tabanus thoracinus 2542 - 50 2650 a re) 
(Pal. de Beauv.) | 
Remarks.—It is seen that the Tabanide had ample opportunity to feed indiscriminately on the 
infected and healthy calves over a considerable period of time. Large numbers of flies were used, 
yet no normal calf contracted the disease. The fact that the Tabanide died within 48 hours of 
being put in the kraal does away with the possibility of a development of Trypanosoma pecorum 
in the flies. These experiments, therefore, only prove that these flies do not transmit the 
trypanosome mechanically. 
4, A STUDY OF THE FLAGELLATES FOUND IN TABANUS SECEDENS, TABANUS 
FUSCOMARGINATUS AND TABANUS THORACINUS. 
In this investigation two series of dissections were made. In the first 
wild flies caught in the neighbourhood of the laboratory were dissected. In 
the second series dissections were made of wild flies caught in the neighbour- 
hood and introduced into the fly-compartment of the kraal, where they were 
used in the transmission experiments detailed above. 
As wild flies were used throughout, it was necessary to carefully study the 
flagellates which may infect these flies, in order that parasites natural to the 
flies, such as Crithidia or Herpetomonas, should not be mistaken for 
developmental forms of pathogenic trypanosomes in the fly. 
It should be noted here that the cattle which grazed in the neighbourhood 
where the flies were caught were healthy during the period that the 
investigations were being carried out. 
In the first series of dissections 158 Zabanus secedens and 49 Tabanus 
thoracinus were dissected. Of the Zabanus secedens 7 (5 per cent.) showed 
a heavy infection of flagellates in the hind-gut, rectum, and proctodeum. 
The mouth parts and remainder of the alimentary tract contained no 
2D 2 
