CAUSING ACUTE INFECTIONS. 
87 
theria bacilli that persist in the throat after recovery. 
The toxins formed by the bacillus are both endo- and 
extra- cellular. Immunity in animals is produced with 
much difficulty, but in man no way of producing im¬ 
munity has been devised. 
The Spirillum of Asiatic Cholera. 
The micro-organism causing cholera is a small, 
curved rod, often shaped like a comma, and therefore 
called the comma bacillus. When two are placed end 
to end they are S-shaped. True corkscrew forms 
occur, particularly in cultures in fluid media. The 
spirillum was discovered by Professor Koch in 1884. 
It is motile, being propelled by a single flagellum placed 
at one end, and grows on all the laboratory media in 
the presence of oxygen. No spores are formed. It is 
Gram negative. 
Cholera exists constantly in India and countries 
of the Orient. It has been carried occasionally to 
other countries, causing epidemics. A very bad epi¬ 
demic occurred in Hamburg in 1892. In this country 
the disease has been imported on several occasions, 
but no epidemic has developed since 1873. Strict 
measures are taken at the chief ports,—New York, 
New Orleans, and San Francisco,—to quarantine all 
suspects among the immigrants. 
Infection always takes place by way of the ali¬ 
mentary tract, from infected water and food. While 
infected water is the most common cause, the infection 
may be carried on vegetables that have been washed 
in infected water, particularly those used as salads. 
Distri¬ 
bution of 
the disease 
Path of 
infection 
