584 APPLICATION OF METHODS OF BACTERIOLOGY 



two hours. They are killed when acted upon for three 

 hours by corrosive sublimate, 1 : 1000, and in thirty minutes 

 by the same solution plus 0.5 per cent, of hydrochloric acid. 



Action upon Animals. — After subcutaneous inoculation 

 of mice with minute portions of a pure culture of this 

 organism tetanus develops in twenty-four hours and ends 

 fatally in from two to three days. Rats, guinea-pigs, and 

 rabbits are similarly affected, but only by larger doses than 

 are required for mice, the fatal dose for a rabbit being from 

 0.3 to 0.5 c.c. of a well-developed bouillon culture. The 

 period of incubation for rats and guinea-pigs is twenty-four 

 to thirty hours, and for rabbits from two to three days. 

 Pigeons are but slightly, if at all, susceptible. 



The tetanic convulsions always appear first in the parts 

 nearest the seat of inoculation, and subsequently become 

 general. 



At autopsies upon animals that have succumbed to 

 inoculations with pure cultures^ of bacillus tetani there is 

 little to be seen by either macroscopic or microscopic exami- 

 nation, and cultures from the site of inoculation are often 

 negative in so far as finding the tetanus bacillus is concerned. 

 At the site of inoculation there is usually only a hyperemic 

 condition. In uncomplicated cases there is no suppuration. 

 The internal organs do not present any macroscopic change, 

 and culture-methods of examination show them to be free 

 from bacteria. The death of the animal results from the 

 absorption of a soluble poison, either produced by the bac- 

 teria at the site of inoculation or, which seems more probable, 

 produced by the bacteria in the culture from which they are 



' Animals and human beings that have become infected with this organism 

 in the ordinary way commonly present a condition of suppuration at the 

 site of infection; this is not due, however, to the tetanus bacillus, but 

 to other bacteria that gained access to the wound at the time of infection. 



