Distribution of Tropical Diseases in Africa. 455 
excepting in the Kalahari Desert, where it rises to about 76° F. 
The mean annual range of temperature varies somewhat: on 
the coast it is from 10° to 20°; inland it is from 20° to 
40° F, The annual rainfall varies considerably. It is least 
on the west, where it is under 10 inches; indeed, in the 
north-west, it is only about 3 inches annually. On the 
eastern coast the precipitation is heavy, varying from 18 to 
40 inches. Between these two areas, in the South African 
Republic and Orange Free States, the annual rainfall is from 
10 to 25 inches, 
In the most northern part of this area we have two 
districts—Mashonaland and Matabeleland. The altitude of 
this country is about 4000 feet. The rainy season is from 
November to February, and, on the whole, the district 
appears to be fairly healthy, although we have not sufficient 
reliable information upon which to offer a final opinion. 
We know, however, that dysentery, diarrhcea, and rheu- 
matism are very prevalent, and that malaria also prevails, 
though, perhaps, not so extensively as it does to the north 
of the Zambesi—Bechuanaland has the same elevation. In 
the west we have the Kalahari Desert, with a very slight 
rainfall and with considerable heat; but the eastern district 
is better known, and therefore, probably, we have informa- 
tion of more numerous diseases, although, on the whole, the 
country would appear to be healthy. The rainy season is 
from December to April; the average rainfall is 25 inches ; 
the temperature may be as high as 85° or 90° F. The 
climate is, on the whole, dry and invigorating. Probably 
the most fatal disease in this district is dysentery. Enteric 
fever is also met with; malarial fevers are unimportant; 
measles and small-pox occur in epidemics; phthisis is 
unknown; bronchitis, pleurisy, and pneumonia are only 
very rarely seen. Syphilis is now common; rheumatism 
and hepatitis are both met with; ophthalmia is extremely 
common, and so is whooping-cough. Leprosy is not 
endemic; this is rather surprising, as the disease is pre- 
valent at the Cape. 
The Orange Free State is an elevated plateau lying 4000 
to 5000 feet above sea-level. It possesses a remarkably 
