THE MICROBES OF HUMAN DISEASES. 207 
ducing the attenuated microbe into the stomach by 
means of pills or a liquid, would not be more rational. 
Mode of Propagation and Persistence of Cholera.— 
The upper part of the delta of the Ganges seems to 
be the original home of cholera and its microbe. 
Below this region, the stagnant water on each side 
of the river, infected with every species of ordure, 
renders the maritime base of the delta wholly unin- 
habitable. But even in its upper part the land is 
nearly covered by water. In order to build a house, 
the earth is heaped up to raise the level of the soil, 
and the house stands on the embankment, surrounded 
by water. <A high temperature is necessary to enable 
the bacillus to live in water, and it is probable that it 
will never become acclimatized in our colder climate. 
The drainage which has been carried on round Cal- 
cutta has already rendered epidemics less serious. 
The disease is always propagated by man. In 
India, Arabia, and Egypt, its diffusion is chiefly owing 
to pilgrimages. In Bengal the pilgrims all bathe 
together in sacred pools, often only a few square 
metres in size, and receiving some thousands of men 
in the course of the day, streaming with sweat and 
exhausted by long journeys and insufficient food, and 
under such conditions cholera is often developed. 
From India it passes to Arabia by means of the 
Mussulman pilgrims, whose caravans block the nar- 
row streets of Mecca every year, and thence it is trans- 
ported to Egypt. Finally, it is carried from Alexandria 
