PRINCIPLES OF VETERINARY SURGERY 457 



a lasting immunity is obtained, and the blood of the animals 

 so vaccinated iDreserves a great antitoxic power for eight 

 months or more. By using doses infinitely smaller, but 

 more frequently repeated, identical results are obtained on 

 the cavy. The immunity is also lasting. It persists for at 

 least one year, and in the female it is transmitted to the 

 offspring. 



Other means may be applied in the rabbit, or even more 

 sensitive animals, like the cavy and rat. One of them con- 

 sists of using toxin modified by iodine instead of by heat. 

 Iodine, in small doses, instantaneously neutralizes tetanic 

 toxin. If to five cubic centimeters of a filtered culture, of 

 which 1-6,000 of a cubic centimeter is sufficient to kill an 

 adult cavy, an equal part of iodine water, — i to 500, — is 

 added, the entire mixture may be injected into a cavy with- 

 out producing the least tetanic symptom. The injection of 

 comparatively large doses of this mixture into the veins of a 

 rabbit gives negative results. After injecting increasing 

 doses of this kind animals acquire immunity. The process is 

 applicable to the cavy and the rat and is absolutely free from 

 all danger. The same method rapidly immunized the sheep, 

 the calf and the horse. The immunity thus conferred on the 

 horse may be very considerable. Its degree is subordinate 

 to the amount of toxin injected into the vaccinated animal. 

 Nocard immunized a horse that was capable of receiving 

 250 to 300 cubic centimeters of tetanic toxin in the jugular 

 with impunity, that is to say, sufficient to kill 2,500 horses. 

 Other substances will attenuate or neutralize the tetanic tox- 

 in and replace iodine. These are trichloride of iodine, used by 

 Behring and Kitasato, extract of thymus, by Brieger, Kita- 

 sato and Wasserman, chlorine solution, 5 per cent, and car- 

 bolic acid solution, 5 per cent, by Tizzoni and Cattani. The 

 hypochlorites, permanganate of potash and carbonic acid 



