1888 - 89 .] Dr R. W. Felkin on Tropical Diseases. 
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rains will give to cholera an impetus, whereas continuous rains, by 
completely saturating the soil, prevent its occurrence. No one 
knows the cause which gives it epidemic impulse, hut we know 
that, generally speaking, cholera becomes epidemic during the 
intensely hot weather following heavy rains. 
The wind may have a certain action on the spread of cholera, 
always provided that it he a moist wind, hut the old idea that 
winds could convey cholera poison for long distances seems now to 
he obsolete. But indirectly the south-west monsoon certainly aids 
in spreading cholera, because it brings with it moisture which is 
necessary for its propagation, and because numbers of vessels take 
advantage of this monsoon to sail from the endemic area of cholera 
to other places. As Macnamara justly remarks, “ cholera thus pro- 
gresses with man along the great high-roads upon which he travels, 
spreading no faster than he moves, and being generated by wet, hot 
weather.” Although the disease is thus indirectly spread by the 
south-west monsoon, it must not be concluded that it cannot travel 
against wind, for it travels just as fast against the wind as with it. 
Water is capable of disseminating cholera germs after they have 
been produced in the soil, or after it has been contaminated by the 
discharges of cholera patients. 
The great factor in the distribution of cholera is certainly that 
of human intercourse. Persons suffering from the disease, though it 
may be only in a latent form, undoubtedly convey the poison for long 
distances, and it is a well known fact that troops, pilgrims, and 
emigrants have spread it far and wide. It is necessary, however, 
for an epidemic of cholera to arise, that the poison conveyed into 
a district should find there a fitting soil for its growth. What that 
fitting soil is, it is impossible yet to say. 
IV. Yellow Fever. 
(See Plate IV. A.) 
Synon . — Yellow Jack; Bronze John; Yomito Prieto; Fr . Fievre 
jaune ; Ger. Gelbes Fieber. 
Definition . — A pestilential contagious fever of a continuous and 
special type. It presents two well-defined stages. The first extends 
from 36 to 150 hours, and is marked by rapid circulation and 
