keep a fly-struck horse alive for months; alive, but robbed of all his
life and fire, his free gait replaced by a shambling walk. The wild
game, more especially the water buck and the buffalo whose blood is
teeming with these trypanosomes, but who, from generations of infection,
have acquired an immunity from these parasites, keep these flies
infected. Thus one cannot have domestic cattle and wild game in the same
area; the two are incompatible. And shortly the time will come, as
certainly as this land will support a white population, when the wild
game will be exterminated and _Glossina morsitans_ will bite no more.

More troublesome, because more widely spread, are the large family of
mosquitoes. The _anopheles_, small, grey and quietly persistent, carries
the malaria that has laid our army low. _Culex_, larger and more noisy,
trumpets his presence in the night watches: but the mischief he causes
is in inverse ratio to the noise he makes. _Stegomyia_, host of the
spirium of yellow fever, is also here, but happily not yet infected; not
yet, but it may be only a question of time before yellow fever is
brought along the railways or caravan routes from the Congo or the
rivers of the West Coast, where the disease is endemic. There for many
years it was regarded as biliary fever or blackwater or malaria. Now
that the truth is known a heavier responsibility is cast upon the
already overburdened shoulders of the Sanitary Officer and the
specialists in tropical diseases. _Stegomyia_, as yet uninfected, are
also found in quantities in the East; and with the opening of the Panama
Canal, that links the West Indies and Caribbean Sea, where yellow fever
is endemic, with the teeming millions of China and India, may materially
add to the burden of the doctors in the East. Living a bare fourteen
days as he does, infected _stegomyia_ died a natural death, in the old
days, during the long voyage round the Horn, and thus failed to infect
the Eastern Coolie, who would in turn infect these brothers of the West