584 BACTERIOLOGY. 
become completely dry there is little danger. Further, 
we must conclude from the distribution of the cholera 
bacillus in the body and from experiments upon ani- 
mals that the commonest mode of infection is by way 
of the mouth, and chiefly by means of water used for 
drinking purposes, for the preparation of food, ete. In 
recent times cholera spirilla have been found not infre- 
quently in water (wells, water-mains, rivers, harbors, 
and canals) which have become contaminated by the 
dejections of cholera patients. 
But, like other infectious diseases, not everyone who 
is exposed to infection is attacked by cholera. The 
bacilli have been found during cholera epidemics in the 
dejections of healthy individuals without any patholog- 
ical symptoms. Abel and Claussen found, for example, 
in 14 out of 17 persons belonging to the families of 7 
cholera patients, cholera vibrios, in some of them for a 
period of fourteen days. In Hamburg there were 28 
such cases of healthy choleraic individuals with abso- 
lutely normal stools. It is evident, therefore, that an 
individual susceptibility is requisite to produce the dis- - 
ease. In the normal healthy stomach the hydrochloric 
acid of the gastric secretions may destroy the spirilla; 
and, finally, the normal vital resistance of the tissue. 
cells to the action of the cholera poison may be taken 
into consideration. According to the greater or less 
power of this vital resistance of the body the same 
infectious matter may give rise to no disturbance what- 
ever, aslight diarrhoea, or it may lead to serious results. 
Furthermore, it may be accepted as an established fact, 
that recovery from one attack of cholera produces per- 
sonal immunity to a second attack for a considerable 
length of time. This does not appear to depend upon 
