ASIATIC CHOLERA 151 



with 8606 deaths, while Altona during the same 

 period had 516 cases, most of them having been in- 

 fected while working in Hamburg, with 316 deaths. 



Since this epidemic Hamburg has estabhshed a 

 satisfactory system of filtration; and though there 

 has been no opportunity for proving its value in 

 times of cholera, the death rate from typhoid fever 

 has fallen from 34 per 100,000 to 6 per 100,000. 



Cholera in Animals. — Under natural conditions 

 animals do not contract cholera. Rabbits have 

 been successfully inoculated by injection into the 

 ear vein, and young rabbits have been infected 

 through spirilla being placed upon the teats of the 

 mother. 



Intraperitoneal injections into guinea-pigs has 

 also produced cholera, this method being often 

 employed to test the virulence of cholera cultures. 



Toxins. — For a long time there was no evidence 

 that cholera spirilla produced toxins, as do the teta- 

 nus and diphtheria bacilli, and it was supposed that 

 the cholera spirilla contained only an endotoxin, 

 that is, a poison within the organism; but later 

 investigations of Metchnikoff, Roux, and others 

 proved that toxins are produced, and that the 

 serum of actively immunized animals does contain an 

 antitoxin which neutrahzes the cholera toxin. 



