I can not conceive. It was practiced by the Bakwains at a
time when they had no intercourse, direct or indirect, with the southern
missionaries. They all adopt readily the use of vaccine virus when it is
brought within their reach.

A certain loathsome disease, which decimates the North American Indians,
and threatens extirpation to the South Sea Islanders, dies out in the
interior of Africa without the aid of medicine; and the Bangwaketse, who
brought it from the west coast, lost it when they came into their own
land southwest of Kolobeng. It seems incapable of permanence in any form
in persons of pure African blood any where in the centre of the country.
In persons of mixed blood it is otherwise; and the virulence of the
secondary symptoms seemed to be, in all the cases that came under my
care, in exact proportion to the greater or less amount of European
blood in the patient. Among the Corannas and Griquas of mixed breed it
produces the same ravages as in Europe; among half-blood Portuguese it
is equally frightful in its inroads on the system; but in the pure Negro
of the central parts it is quite incapable of permanence. Among the
Barotse I found a disease called manassah, which closely resembles that
of the 'foeda mulier' of history.

Equally unknown is stone in the bladder and gravel. I never met with a
case, though the waters are often so strongly impregnated with sulphate
of lime that kettles quickly become incrusted internally with the salt;
and some of my patients, who were troubled with indigestion, believed
that their stomachs had got into the same condition. This freedom from
calculi would appear to be remarkable in the negro race, even in the
United States; for seldom indeed have the most famed lithotomists there
ever operated on a negro.

The diseases most prevalent are the following: pneumonia, produced
by sudden changes of temperature, and other inflammations, as of the
bowels, stomach, and pleura; rheumatism; disease of the heart--but these
become rare as the people adopt the European dress--various forms of
indigestion and ophthalmia; hooping-cough comes frequently; and every
year the period preceding the rains is marked by some sort of epidemic.
Sometimes it is general ophthalmia, resembling closely the Egyptian. In
another year it is a kind of diarrhoea, which nothing will cure until
there is a fall of rain, and any thing acts as a charm after that.
One year the epidemic period was marked by a di