S. T. Darling 
85 
Furthermore, dissections of a number of specimens of S. calcitrans 
from both corrals (17 flies were taken from an experimentally infected 
mule) were made without ever finding a trace of a flagellate in their 
intestinal tracts. A few Tabanids were caugbt at the isolation stable, 
but on dhssectiou none ever showed traces of flagellates. All attempts 
to incriminate biting flies, ticks, bats, or other blood-sucking vertebrates 
or invertebrates, failed. 
Upon looking into the nature of the work the animals performed 
(the disease being confined to work-animals) it was ascertained that 
a large number of the infected animals had been in and out of the 
sick corral, having been usually laid up from cuts received by dirt 
scrapei's and from collar galls. These, and other injuries, not only 
opened the skin, and furnished a portal of entry and exit for trypano¬ 
somes, but, as this work on scrapers is very exhausting, the animals 
were no doubt rendered as susceptible as possible to infection. Among 
the infected mules in the isolation corral it was observed that during 
the few days before death, excoriated patches which exuded infectious 
serum appeared on the neck, head and sides of the animals from their 
leaning against the stalls. Swarms of flies, Musca, Gompsomyia and 
Sarcophaga, were attracted to these places and fed upon the exuded 
serum. 
The impression now became confirmed that the disease was being 
transmitted mechanically by flies (occasionally, perhaps, by attendants) 
passing from infected to healthy animals, and transporting the trypano¬ 
somes which were alternately taken up and then deposited upon 
cutaneous wounds. Acting on this belief, it was arranged that all 
animals having a temperature above 101° F. should at once be isolated 
in a screened stable. Daily blood examinations were made of all isolated 
suspects, and when trypanosomes were found in a suspect, the animal 
was shot. Coal tar disinfectants, distasteful to flies, were freely used in 
this stable to keep away intruding flies that had accidentally effected an 
entrance, and the following recommendations were made; 
The temperatures of all animals in the corrals to be taken daily, as a 
matter of routine, for the detection of suspects. 
All animals having a temperature above 101° F. to be immediately 
isolated in a screened stable. 
The diagnosis to be made by blood examinations; occasionally by 
the inoculation of mice or rats, in those cases where trypanosomes have 
disappeared from the peripheral blood for two or three weeks. 
G-2 
