IMMUNITY. 201 



through a relatively insusceptible animal. Councilmann* 

 and his co-workers regard cow-pox and small-pox as identical. 

 But Law, Salmon and Smith f regard the two diseases as 

 different. 



This question cannot be settled with certainty until the or- 

 ganisms causing small-pox and vaccinia have been isolated 

 in pure culture. Their identity and mode of action may then 

 be determined. 



Small-pox has been inoculated into calves and passed 

 through other calves in succession, producing finally an erup- 

 tion indistinguishable from cow-pox. Not only does recovery 

 from spontaneous or artificial cow-pox protect against small- 

 pox, but it has been shown that recovery from small-pox 

 protects against cow-pox. 



Attenuated Virus and Cultures in Which the Bacteria 

 are Killed. Pasteur conceived the idea of attenuating the 

 virulence of the bacilli of fowl-cholera by prolonged exposure 

 to the air. He made use of the virus thus attenuated as a 

 vaccine against the disease. 



A nearly similar principle was shortly afterward applied by 

 him to the preparation of a vaccine against anthrax. When 

 anthrax bacilli were cultivated at a temperature of 43 C., 

 Pasteur obtained bacilli of very slight virulence. Such bacilli 

 did not produce death when inoculated into animals that were 

 ordinarily susceptible. Yet animals that were vaccinated with 

 this virus were able afterward to resist inoculation with fully 

 virulent anthrax bacilli. (See Bacillus anthracis, Part, IVj. 



Successful methods of inoculation have been found for 

 rinderpest, an infectious disease of cattle in which the digestive 

 organs are mainly involved. There are three ways which are 

 eflficacious:J (i) Injection of bile from an animal recently 

 dead of rinderpest; (2) inoculation of glycerinated bile, fol- 



* Journ. Med. Research. VII. No. i. 



^Diseases of Cattle. Dept. Agr. Pub. 1904. p. 237 and p. 426. 



^Diseases of Cattle. Dept. Agricult. Publication. 1904. pp. 380-381. 



