240 PATHOGENIC BACTERIA. 



The mouse develops typical tetanic convulsions, which 

 begin first in the neighborhood of the inoculation, but 

 soon become general. Death follows sometimes in a 

 very few hours. In rabbits the period of incubation is 

 nearly two weeks, and in man may be three weeks. 



The conditions in the animal body are not favorable 

 for the development of the bacilli, because of the free 

 supply of oxygen contained in the blood, and we find 

 that they grow with great slowness, remain localized at 

 the seat of inoculation, and never enter the blood- or 

 lymph-circulation. Doubtless most cases of tetanus are 

 cases of mixed infection in which the bacillus enters with 

 bacteria, which greatly aid its growth by using up the 

 oxygen in their neighborhood. The amount of poison 

 produced must be exceedingly small and its power tre- 

 mendous, else so few bacilli growing under adverse con- 

 ditions could not produce fatal toxemia. The poison is 

 produced rapidly, for Kitasato found that if mice were 

 inoculated at the root of the tail, and afterward the skin 

 and the subcutaneous tissues around the inoculation were 

 either excised or burned out, this treatment would not 

 save the animal unless the operation were performed 

 within an hour after the inoculation. 



The circulating blood of diseased animals is fatal to 

 susceptible animals because of the toxin which it con- 

 tains ; and that the urine is also toxic to mice proves the 

 excretion of the toxin through the kidneys. 



From pure cultures of tetanus bacilli grown in various 

 media, and from the blood and tissues of animals affected 

 with the disease, Brieger has succeeded in separating two 

 poisonous substances "tetanin" and " tetano-toxin. " 



The pathology of the disease is of much interest be- 

 cause of its purely toxic nature. There is generally a 

 small wound with a slight amount of suppuration. At 

 the autopsy the organs of the body are normal in appear- 

 ance, except the nervous system, which bears the great- 

 est insult. It, however, shows little else than congestion 

 either macroscopically or microscopically. 



