PRINCIPLES OF VETERINARY SURGERY 455 



the nerve is divided in one of them, — it resists, while the 

 other dies. 



IMMUNIZATION.— Tetanus is not a self-Hmiting dis- 

 ease. One attack does not secure the patient against 

 a second. Every animal is immune against the micro- 

 organism deprived of its toxin, but none is ever im- 

 mune to the toxin. Tetanus is a toxic disease. To immu- 

 nize against it is to immunize against the tetanic poison. Nu- 

 merous attempts have been made to give animals complete 

 immunity. By repeated injections of small doses of culture 

 Tizzoni and Cattani in 1891 immunized a dog and two pig- 

 eons. Instead of inoculating with pure cultures, Behring 

 and Kitasato, in 1890, sought to modify the culture by add- 

 ing certain substances. They inject a virulent culture into a 

 rabbit, then, immediately, three cubic centimeters of a one 

 per cent solution of trichloride of iodine. In twenty-four 

 hours four similar injections are given. Rabbits thus acquire 

 a degree of immunity that permits them to receive with im- 

 punity from two to three cubic centimeters of a virulent cul- 

 ture at the end of fifteen to twenty-five days. Their resist- 

 ance increases, and soon they are able to resist five cubic 

 centimeters of very active culture. The method is, how- 

 ever, not perfect, as a great number of the animals ;uccumb. 

 — probably 60 per cent. And, besides, it is not a general 

 process; it is applicable only to the rabbit; it fails in the 

 cavy and mouse. 



Brieger, Kitasato and V\'asserman have sought for a more 

 perfect method. They have obtained better results by using 

 cultures of tetanus bacilli in extract of thymus glands. The 

 micro-organisms thus cultivated formed neither spores noi" 

 toxins. The inoculation of these cultures, which are vaccin- 

 ative and not toxic, immunized the rabbit and the mouse. 

 Vaillard recommended a very dififer.-nt method, which con- 

 sists of utilizing the micro-organism without attenuation or 



