I02 Immunity 



in preventing epidemics by which great numbers of the barnyard 

 fowls of France were being destroyed. 



In 1881 Pasteur,* in experimenting with Bacillus anthracis, ob- 

 served that if the organism were cultivated at unusually high temper- 

 atures it lost the power of producing spores, and diminished in viru- 

 lence. He also found that when the organisms had been so attenuated 

 they could not regain virulence without artificial manipulation. 

 It occurred to him that such organisms, possessing feeble virulence, 

 might be able to confer immunity upon animals into which they were 

 inoculated, and he continued to investigate the subject until he 

 found that by using three "vaccines" or modified cultures of increas- 

 ing virulence, it was possible to render animals immune against the 

 unmodified organisms. This method was put to practical test 

 with great success, and has since been extensively practised in differ- 

 ent parts of the world. 



Arloing, Cornevin and Thomas, f and Kittf found that exposure 

 of the Bacillus anthracis symptomatici to a high temperature in 

 the dry state modified its virulence and devised a practical method 

 of protecting cattle against symptomatic anthrax by inoculating 

 them with powdered muscle tissue containing the bacilli attenuated 

 by drying and exposure to 85°C. This method has since been in use 

 in many countries, and has given excellent satisfaction. 



In 1889 Pasteur',§ continuing his researches upon the experimental 

 modification of the germs of disease and their use as prophylactics, 

 published his famous work upon rabies, and showed that, although 

 the micro-organism of that disease had so far eluded discovery, it 

 was contained in the central nervous system of diseased animals, 

 where it could be modified in virulence by drying. By placing spinal 

 cords removed from rabid rabbits in a glass jar containing calcium 

 chlorid, he was able to diminish the virulence of the contained 

 micro-organisms according to the duration of the exposure. The 

 introduction of the attenuated virus followed by the develop- 

 ment of a certain degree of immunity. By repeated inoculation of 

 more and more active viruses animals acquired complete immunity 

 against street virus. These experiments form the basis of the 

 "Pasteur method" of treating rabies, which is nothing more than 

 immunization with the modified germs of the disease during the long 

 incubation period of the disease. 



Haffkine|| found that the introduction of killed cultures of virulent 

 cholera spirilla produced immunity against the living micro-organ- 

 isms, and used the method with considerable success for preventing 

 the disease. Later** he applied the same method, also witi. consider- 



* " Compte rendu de la Soc. de Biol, de Paris," 1881, xcii, pp. 662-665. 

 t"Le Charbon Symptomatique du Bceuf," Paris, 1887. 

 j"Centralbl. f. Bakt.," etc., I, p. 684. 



§ "Compte rendu de la Soc. de Biol, de Paris," 1881, cviii, p. 1228. 

 I! "Brit. Med. Jour.," 1891, 11, p. 1278. 

 ** "Brit. Med. Jour.," 1895, 11, p. 1541. 



