ACUTE ARTICULAR RHEUMATISM. 729 



thus putting the hypothesis of Eberle on a firm 

 basis. 



Ashburn and Craig were unable to find the or- Fiiterabmty 

 ganism responsible for the disease, but demon- 

 strated that the filtered blood of infected persons 

 can produce the disease in healthy subjects. They 

 were unable to cultivate or detect in other ways 

 any micro-organisms. 



According to Ashburn and Craig, an attack of 

 dengue confers immunity. They were unable to 

 produce a second attack by the injection of infec- 

 tious blood in individuals who had recovered from 

 the disease. 



VI. ACUTE ARTICULAR RHEUMATISM. 



(See p. 525.) 



VII. SMALLPOX AND VACCINIA. 



Vaccinia and smallpox may be considered to- Relation of 

 gether, having in mind the likelihood or, indeed, " 



the certainty, that they have a common etiology. 

 This view seems the only possible one, in spite of 

 our uncertainty as to the exact nature of the cause. 

 To hold a different view would be to acknowledge 

 that immunization with one kind of microbe may 

 confer immunity of the strongest and most spe- 

 cific character against another, a condition for 

 which we could find no parallel. 



More satisfactory knowledge, however, comee 

 from actual conversion of smallpox virus into vac- smallpox. 

 cine virus by passing the former through cows. 

 Abbot quotes W. J. Simpson as follows : "In No- 

 vember, 1885, with smallpox lymph from an un- 

 vaccinated patient, 1 inoculated a cow with fifth- 

 day lymph and a ewe with eight-day lymph from 



