456 PRINCIPLES OF VETERINARY SURGERY 



modification. He determined the refractory point of the 

 rabbit "by repeated inoculations into the connective tissue 

 of the tail, beginning with small quantities, to which lactic 

 acid had been added." This method is not general. It suc- 

 ceeds with the rabbit, but is more risky in the cavy and rat. 

 Cavies have, however, been rendered refractory in [his man- 

 ner. 



Instead of using complete cultures for vaccination, one 

 can use cviltures filtered of the micro-organisms, and that 

 possess vaccinating properties. This method is more certain 

 and more practical than Behring's and Kitasato's. The ani- 

 mal is first accustomed to the tetanic poison by the inocu- 

 lation of small doses of filtered cultures whose toxic activity 

 has not been modified. It is necessary to proceed cautiously, 

 as inoculation with one dose that is a little too strong will 

 kill the subject. The process proceeds well with the rabbit, 

 but is less certain with the cavy, because of a greater sensi- 

 bility. By an artifice, Vaillard diminished the activity of the 

 toxin before injecting, and was thus able to operate with 

 greater certainty. Filtered cultures are partly deprived of 

 their toxicity by heating, and are introduced into the blood 

 in large doses, heated at gradually decreasing temperatures — 

 60°, 55", 50° C. These are followed by g-radually increasing 

 quantities of filtered cultures that are not diminished in tox- 

 icity. The application of this method is easy in the rabbit. 

 At intervals of three days two doses of ten cubic centimeters 

 of a filtered culture, heated to 60°, are injected into a vein of 

 the ear of a rabbit. Five days after, ten cubic centimeters 

 of cultures, heated to 50°, are injected. This already gives im- 

 munity to the animals and confers antitoxic properties to 

 the blood. The state is afterwards reinforced by injections 

 of cultures having their full toxicity. For this purpose' in- 

 creasing doses, 5, 10, 15, 20 and 30 cubic centimeters, are 

 injected every eight to ten days. In all the animals so treated 



