Distribution of Tropical Diseases in Africa. 449 
V. THE SAHARA AND SOUDAN. 
This area, which includes the country as far south as 
10° N. latitude, takes in the districts of Bornu, Wadai, 
Darfur, and Kordofan, and must be dismissed in a few lines, 
statistics being wanting with respect to it. On the whole 
the climate is intensely hot in summer, but the diurnal 
variation is very great. Sometimes the thermometer is 
many degrees below freezing point at night, although during 
the day it may be as much as 115° F. In the northern part 
of this district the mean annual variation or range of tem- 
perature is from 40° to 50°. In the southern part, in Wadai, 
Darfur, Kordofan, the range is considerably less, being only 
from 10° to 20° F. Over the greater part of the area the mean 
annual temperature is over 80° F., although in the district 
round Wadai it varies from 70° to 80°, this being due to the 
altitude of the country, which is from 3000 to 8000 feet. On 
the whole, this district may be said to be healthy. Except 
in the oases, malaria is almost absent. In Darfur and Kor- 
dofan dysentery, diarrhoea, and typhoid fever are met with; 
syphilis and bronchitis are fairly common; and in the southern 
part of Darfur the guinea-worm is very frequent, the area of 
its northern distribution at this point being about 11° N. 
lat. Goitre is not infrequently seen in inhabitants of the 
Djebel Marra. The most malarious parts of this district are 
the low swampy regions round Lake Chad, Dibbe, and Filter, 
and the province of Fezzan. 
VI. EQUATORIAL CENTRAL AFRICA, 
including the Congo Free State, and reaching south to the 
18th degree of S. lat. 
The mean annual temperature of the whole of this region 
is about 78° F., being slightly lower to the west of the 
Victoria Nyanza in the Ruwenzori mountain region, on the 
high plateau to the east of the Victoria Nyanza, and in 
Msiri’s kingdom, where it varies from 65° to 70° F. The 
mean annual range of temperature in the Congo region is 
less than 5° F.; in the remaining area it is between 5° and 
10° F., except in the region to the south of the Victoria 
