1888 - 89 .] Dr R. W. Felkin on Tropical Diseases . 283 
countries is certain. It appears to be equally certain that, apart 
from the original impetus given to cholera in 1817, the commerce 
of the world has been the means of spreading it over such a world- 
wide area as indicated on the map. 
The first pandemic, of which we have authentic data, occurred 
during the years 1817-1823, in which period the disease devastated 
an area from Nagasaki, 147° E., to the coast of Syria, 52° E„, and 
from Bourbon, 21° S., to Astrakan, 46° 21' N. 
The second pandemic, which took place during the years 1826- 
1837, overspread nearly the whole of the countries marked on the 
map as being affected by cholera. From 1837-1846 Europe, Africa, 
and America were free from further outbreaks of the disease. 
The third great pandemic occurred from 1848-1863, with a 
remission, as far as the eastern hemisphere is concerned, between 
1850 and 1852 ; and during this pandemic it visited the whole of 
the northern hemisphere, and reached lat. 25° S. in the Old world and 
30° S. in the New. 
The fourth pandemic occurred during the years 1865-75, and 
is noticeable for the rapidity with which cholera was introduced 
into Europe by sea from the coast of Arabia. In the former 
pandemics it had always come from the east by way of Afghanistan, 
Persia, and Asiatic Russia. From 1875 until the limited outbreak 
in 1883, when cholera appeared in Italy, Spain, and the south of 
France from Egypt, the disease has been confined to Asiatic soil, 
and in the year mentioned the spread of cholera was very strictly 
limited. 
Remarks . — Before referring briefly to some points in the origin 
and spread of cholera, it may be well to remark that, however 
the disease is produced, the researches of Koch, which have been 
very recently confirmed by Drs Milles and Macleod, who investigated 
the subject in 1875 at Shanghai, and an abstract of whose researches 
was read before the Royal Society of Edinburgh on Dec. 17, 1888, 
have almost definitely proved that the comma bacillus has a causal 
relation to cholera. This bacillus is constantly present in Asiatic 
cholera, and it has never been found anywhere but in Asiatic 
cholera. Granting, as we think we are right in doing, that cholera 
is produced by a morbific microbe, we must next refer to various 
facts with regard to the conditions necessary for an epidemic of 
