TO SOME DISEASES OF STOCK 
887 
this country ; and although each species of domestic animal 
is commonly affected with its own species, there are some 
which will pass at least a temporary existence upon another 
host. 
We all know how differently a flea-bite may affect any two 
individuals. It is of interest to realise that some species of 
flea have their own especial poison, and that a man by constant 
bites acquires a tolerance or an immunity to a given flea. But 
let that man be bitten by a species to which he has not acquired 
a tolerance, and he will respond and react as readily as any 
other person. When I tell you that in Nairobi alone there 
are four species of flea very common upon dogs, and at least an 
equal number on cats and other animals (domestic and other- 
wise) which frequent a house, you may realise why, even after 
long resistance, you sometimes feel the effect of a bite. 
Bugs, in virtue of their essentially domestic habits, do not 
enter into the veterinary field, so far as is yet known ; but it 
is quite conceivable that subsequent research may demonstrate 
both lice and fleas to be of pathological importance as carriers 
of disease ; and I suggest these two orders to the members of 
this Society for study, both from a classification point of view 
and from that of their life histories. 
Among the flies or Diptem, we find several species of 
extreme importance as hosts and as carriers of disease in man 
and animals. Even those which do not suck blood may be 
incriminated ; for no one now disputes the r61e played by the 
common house-fly as a mechanical carrier of the typhoid and 
cholera microbes. Cases of anthrax in man have also been 
ascribed to their agency ; and when it is known that the legs 
and wings of flies, which have walked over the skinned body 
of an animal dead of this disease, can carry the germs for 
twenty days, and, should those flies have fed upon the meat, 
their excreta contain the organisms for at least the same time, 
the justification for this belief is obvious. Should a house-fly — 
and with it may be grouped those flesh- or meat-flies so common 
in some neighbourhoods — die from any cause shortly after 
having fed upon an anthrax carcass, it has been demonstrated 
that their bodies can contain the anthrax organism for upwards 
of three years at least. Flies, too, which hatch out from maggots 
