Distribution of Tropical Diseases in Africa. 439 
The total rainfall is about 58 inches annually, and the mean 
annual temperature 80° F. The mean annual variation is 
very slight, being only about 10°. 
The Niger district has almost the same characteristics as 
the one just mentioned, except that the temperature is 
somewhat higher, the heat during March to June or July 
averaging 105° F., the mean annual temperature being 
about 86° F. The rainfall is about 60 inches; the relative 
humidity about 85. Proceeding farther south, we come to 
Gaboon, where the mean annual temperature is 95° F., the 
rainfall from 100 to 110 inches, the relative humidity very 
high, rarely under 90. The heaviest rains occur between 
September and January. 
The next district to be mentioned is that at the mouth of 
the Congo. The mean annual temperature is 76° F., the 
annual range 9° F.; the rainfall 43 inches; the relative 
humidity for the year 75 per cent., the annual range 13. 
The rainy season is from November to May, with prevailing 
westerly winds. 
With regard to the next region, Angola, the following data 
represent the climate at St Paul de Loanda. The mean 
annual temperature 74° F., the annual range 12° F.; the 
rainfall 13 inches; the relative humidity 82 per cent., and 
the annual range of humidity 10. Here there are two rainy 
seasons—October to December, and March to May. 
In the districts to the south, namely, Benguela and Mosa- 
medes, the country is drier, the rainfall varying from 10 to 
30 inches, the mean annual temperature being about 68° F. 
the annual range 20° F. 
The disorders met with on the west coast of Africa, and 
which may be regarded as the most prevalent tropical 
diseases, are numerous, and we have to deal with two of them 
which are unknown on the eastern side of the continent, 
namely, yellow fever and yaws. Following the rough order 
which I have hitherto adopted, we find that typhoid fever is 
met with occasionally in Senegambia, more rarely perhaps in 
Sierra Leone. It is not reported from the Gold Coast, but it 
occurs in the Niger district, as also in Gaboon. There are 
no reports of typhoid fever from the Congo, but, as it is 
