rROTECTlVK INOCULATION 555 



solution. This action Bordet considers as a specific one. 

 Wassermann has formulated this reaction thus, " if an animal, 

 species A, be treated with blood of species B, the serum 

 derived from A will have acquired an agglutinating power 

 which differs from that of normal serum of A in one very im- 

 portant particular, namely, in that it is specifically increased 

 with respect to the red cells of species B or its nearest biologi- 

 cal relative. This clumping must not be confounded with 

 rouleaux formation in normal blood." 



For a more extended discussion of the subject of hemolysis 

 and for cytolysis, cytotoxins, agglutinins and precipitins the 

 student is referred to the special literature on these subjects. 



§ 449. Protective inoculation. The practical applica- 

 tion of immunity in protective inoculations or vaccination has 

 come to mean the establishment of partial or complete im- 

 munity in the individual against the disease in question. The 

 vaccination against small pox introduced by Jenner in 1796 is a 

 well known example of protective inoculation. Pasteur found 

 that animals inoculated with attenuated cultures of anthrax 

 and chicken cholera bacteria were subsequently immune to 

 their respective diseases. From this there has developed 

 many procedures for establishing both active and passive 

 immunity against a number of diseases of animals. The 

 methods that are now in use, together with the diseases 

 against which they are employed, may be summarized as 

 follows : 



I. Active immu72ity. 



I . The injection of non-lethal doses of the virulent virus. 

 This method is employed most extensively in immunizing 

 cattle against Texas fever and bovine contagious pleuro-pneu- 

 monia. It is used in France to immunize against sheep pox 

 (clavelization) . 



The fact that su.sceptible cattle can be immunized against 

 Texas fever by the use of blood from immunized animals has 

 been demonstrated. The method is being applied with suc- 

 cess in several places in the tick infected district. It is a 



