572 DISEASES OF UNKNOWN ETIOLOGY 



1789; he showed experimentally that a successful inoculation of man 

 with cowpox virus protected the individual against infection with 

 the virus of smallpox. 



The change which the smallpox virus undergoes during passage 

 through calves is not definitely known, but Councilman, Magrath, 

 Brinkeroff and others are of the opinion that the smallpox virus 

 is somewhat widely distributed in the viscera and different organs 

 of the body (in man); passage of the virus through calves so modifies 

 its activities that it localizes rather specifically in pavement epithelium. 

 The relatively insignificant local lesions of vaccinia in contrast to the 

 general distribution of the eruption and lesions of smallpox are in 

 harmony with this view. 



FIG. 95. Guarnieri cell inclusion bodies. 



Jenner's remarkable studies upon the immunity to smallpox that 

 follows vaccination with cowpox virus have been amply confirmed 

 by the observations of Brinkerhoff and Tyzzer, 1 who showed that 

 vaccination of monkeys protects them from subsequent infection 

 with the smallpox virus. 



Originally vaccine virus was perpetuated by arm to arm inocula- 

 tion, but the danger of transmitting syphilis or other disease as well 

 as the uncertainty of the method have led to the use of calves as a source 

 of vaccine virus. 



The source of the virus is threefold: 2 



1. Virus descended from spontaneous cowpox and continued through 

 an indefinite series of animals the true animal vaccine. 



1 Jour. Med. Research, 1905, xiv, 209. 



2 Theobald Smith, Med. Soc. Proc., June 10, 1903. 



