578 BACTERIOLOGY. 
_over, that the comma bacillus is extremely sensitive to 
the action of acids, and is quickly destroyed by the acid 
secretions of the stomach of man or the lower animals 
when these secretions are normally produced. Despite 
the small prospects of success, however, from animal 
experiments, these have been undertaken again and 
again, until finally a method was found by which at 
least similar processes have been produced in test ani- 
mals by inoculation of pure cultures of the cholera 
vibrio. Koch sought to produce infection in guinea- 
pigs per vias naturales by first neutralizing the con- 
tents of the stomach with a solution of carbonate of 
soda—5 c.c. of a 5 per cent. solution injected into the 
stomach through a pharyngeal catheter—and then after 
a while administered through a similar catheter 10 c.c. 
of a liquid into which had been put one or two drops 
of a bouillon culture of the comma bacillus. The ani- 
mal then receives a dose of 1 c.c. of tincture of opium 
per 200 grammes of body-weight introduced into the 
abdominal cavity, for the purpose of controlling the 
peristaltic movements. As a result of this treatment 
the animals are completely narcotized for about half an 
hour, but recover from it without showing any ill effects. 
On the evening of the same or following day the ani- 
mal shows an indisposition to eat and other signs of 
weakness, its posterior extremities become weak and 
apparently paralyzed, and, as a rule, death occurs 
within forty-eight hours with the symptoms of collapse 
and fall of temperature. At the autopsy the small 
intestine is found to be congested and filled with a 
watery fluid containing the spirillum in great numbers. 
Koch experimented in this way on about one hundred 
guinea-pigs. These results, however, are somewhat 
