230 GEl^ERAL BIOLOGY OF MICRO-ORGANISMS 



employed to immunize against rabies (Hogyes methbd), and 

 against tuberculosis by Webb. In most diseases these methods 

 are regarded as too dangerous for extensive use. 



, Living virus, altered in its virulence, was first used by Edward 

 Jenner, when he inoculated with cow-pox (vaccinia) and induced 

 immunity to small-pox. Cow-pox is doubtless due to the organism 

 which causes small-pox, attenuated by its life in the body of the 

 cow. Viruses artificially cultivable are attenuated by a variety 

 of procedures, and are employed to induce immunity. Pasteur's 

 vaccine for anthrax, for chicken cholera and possibly the treatment 

 of rabies with dried spinal cord, are examples of the application of 

 this principle. Virus of extraordinary virulence is sometimes in- 

 jected after previous treatment with attenuated organisms, in 

 order to confer a higher degree of immunity. Thus Pasteur 

 employed the most virulent rabies virus obtainable, virus fixe, in 

 the immunization against rabies. 



Living virus, of full virulence, but apparenty influenced in 

 some way by the 'body fluid containing it, is employed in immuniz- 

 ing against rinderpest and against Texas fever. The bile of an 

 animal dpng of rinderpest is injected subcutaneously in doses of 

 10 c.c. into cattle. KoUe has shown that the virus can be sepa- 

 rated from such bile in fully virulent condition; so it appears 

 that some constituents of the bile restrain the activity of the 

 virus. In Texas fever, blood of young animals containing rela- 

 tively few of the parisites is used to inject new animals. 



Immunization by injection of dead microbic substance is now 

 extensively employed in the prophylaxis of cholera, typhoid fever 

 and plague. As a result of such injections there is a marked in- 

 crease in specific agglutinins and bacteriolysins in the blood . The 

 principle of general immunization is also employed with some suc- 

 cess in the treatment of subacute, chronic or recurrent local 

 infections, the production of antibodies and their circulation in 

 the blood and lymph exerting a favorable effect upon the local 

 lesions. The emulsions of dead bacteria employed are called 

 bacterial vaccines. 



