890 
INSECTS AND THEIR RELATION 
birds, and small wild mammals harbour trypanosomes without 
apparent injury; and there is one quite common in cattle of 
this Protectorate, as well as in England, that does not appear 
to produce any symptoms, and which will not affect any species 
of animal but cattle. 
The first disease-producing, or pathogenic, trypanosome 
was found in India in 1880. In forwarding the discoverer’s 
report to the Government of India, the Lieutenant-Governor 
of the Punjab wrote that although this discovery might be of 
some interest, and of possible importance, he regretted that 
Veterinary Colonel Evans had not discovered a cure. Thirty- 
seven years later the same regret can be expressed, although 
the number of pathogenic trypanosomes now known in domestic 
animals and man exceeds twenty. 
The geographical distribution of these trypanosomes, and 
the diseases they give rise to, is wide : Persia, India, Malay 
States, and the Philippine Islands in Asia ; Paraguay, Uruguay, 
Brazil, Guiana, and the Panama Canal Zone in America. In 
Africa they extend from Zululand to the Mediterranean. 
Australia is free, except for cases imported from India. Europe’s 
only form of disease-trypanosome, is one that is not normally 
transmitted by a biting fly, but occurs chiefly in stallions and 
mares on stud farms. 
Compare this distribution with that of the tsetse-flies, 
which, with one insignificant exception, are localised to Africa. 
In this continent, people are accustomed to think that the 
tsetse- fly alone is the carrier of the disease : they pooh-pooh 
the idea that any of the many other species of biting fly can 
be a responsible agent, forgetting or being ignorant of the 
fact that in America and Asia there must be other means of 
transmission. 
On those continents it has been demonstrated that the 
family of horse-flies — Tabanus and Haemato'poda or blind-fly, 
and the genus Stomoxys or 4 stinging house-fly ’ — may carry 
infection by mechanical means from one animal to another. 
The proboscis of these flies is sharp, and is provided with a 
number of irregular teeth, in the shelter of which trypanosomes, 
acquired from the sick animal’s blood, may lodge, to be conveyed 
to a new animal at the next bite. Fortunately, we know that 
