Distribution of Tropical Diseases in Africa. 445 
Amongst the natives, nervous diseases are rather frequently 
seen. Hemiplegia, paraplegia, epilepsy (especially in women), 
acute mania, and dementia are met with. 
Throughout the whole coast endemic dropsy occurs, but 
here again, as I said before in referring to the east coast, I 
think thisis a form of beri-beri. Ague-cake is very common, 
especially in Creoles. It is said, however, to be un- 
common in Sierra Leone, and Gore attributes its rarity in 
that region to the ferruginous character of the soil. Goitre 
is not frequently seen on the west coast of Africa; there are, 
however, some reports of its occurrence in the Cameroon 
district. 
The west coast of Africa presents four seasons, which 
generally begin and end as follows, allowing for latitude 
and local peculiarities. The summer season extends from 
February 15 to May 15, the rainy season from May 15 
to August 51, the harvest season from September 1 to 
November 15, while the harmattan or cold season begins 
on November 15 and ends on February 15. 
The summer is hotter than any of the other seasons, the 
heat being greatest in the region of the trade winds, and 
greater in Sierra Leone than on the Gold Coast and Bight of 
Benin. In addition to the prevailing winds, which vary 
from N. and N.E. in February to S. and S.W. in April, 
the Gambia region is subject to the simoon, a hot wind 
charged with fine sand which blows from the desert, 
destroying vegetation and causing much distress, especially 
in respiratory diseases. Whirlwinds are also prevalent 
during this season. 
The rainy season is ushered in by a cloudy atmosphere 
and frequent tornadoes. The rain gradually increases till in 
July and August it descends in torrents, in many places 
inundating the country and washing away huts and bridges. 
In the Gambia region the commencement of the rains is 
marked by occasional dirt gales, a strong wind carrying the 
surface earth along with it. The actual rainfall varies in 
different places, and also in the same place from year to year. 
It is greatest-during the night, and at the beginning and 
end of the season the fall is limited to the night time. In 
