208 MICROBES, FERMENTS, AND MOULDS 
to Marseilles and other Mediterranean ports by vessels 
which have served for the transport of pilgrims, by 
men, their linen, and other garments. 
It is consequently by the human body and its 
clothing, or by the water which carries away human 
feeces or has served for the washing of soiled linen, 
that the infecting microbes are carried. The air, as 
it has long been known, need not be taken into 
account. As early as 1832, it was observed that the 
wind did not affect the epidemic, which seemed rather 
to advance like a man travelling by short stages. 
Duclaux’s recent researches show that the sun 
and air attenuate and soon destroy the microbes, and 
that only dead germs are borne on the air and wind. 
“In order to retain their virulence unimpaired, the 
microbes must travel in packages of clothing, in bales 
of merchandise, or in the close, moist hold of a vessel. 
In a word, of all agents of sanitation, the sun is at 
once the most universal, the most economical, and 
the most active to which the guardians of public 
and private hygiene can have recourse” (Duclaux). 
Koch has declared that acids in general are the 
greatest hindrance to the development of the cholera 
bacillus. In this way, the acid of the gastric juice 
is the best safeguard, and many cases of contagion 
may be explained by the fact that the large quantity 
of water imbibed has diluted the gastric juice to 
excess, or else that the source of contagion has 
rapidly. passed through the empty stomach, and 
