vni, B. 1 Ashhurn, Vedder, Gentry: Variola and Vaccinia 19 



incline to the opinion that nontransmission of acquired char- 

 acters by heredity is a general law. 



B. We think that already known facts, to be set forth in 

 this paper, point rather to the correctness of the dual virus 

 hypothesis. 



III. EVIDENCE SUPPORTING THE HYPOTHESIS 



1. MORE OF LESS ANALOGOUS CLOSE ASSOCIATION OF VIRUSES 



Hog cholera was long ascribed to B. suipestifer, the disease 

 was stated to be produced by its inoculation, and extensive 

 vaccination was practiced as a preventive measure. (4) 



Yet now it is considered to be due to a filterable virus, and 

 the bacillus merely occurs in close association with that virus. 

 Possibly other diseases (distemper of dogs, guinea-pig epizootic 

 of Petrie and O'Brien, and scarlet fever) present a typical disease 

 picture only as a result of the combined action of filterable 

 virus and bacteria. (8) Prowazek and Baurepaire(9) think that 

 smallpox virus acts in symbiosis with streptococcus. 



The original street virus of hydrophobia, uniformly fatal 

 to man, may be changed by numerous passages through rabbits 

 to virus fixe, which causes a much shorter incubation and earlier 

 death in rabbits, yet this fixed virus may be used to immuniz.e 

 man. Hogye's method of using fresh virus diluted has had 

 extensive trial; (10) and it is even stated(ii) that the entire 

 brains of rabbits dying from inoculations with virus fixe may 

 be and have been injected into men without harm resulting, 

 and that the use of considerable doses of fresh virus fixe has 

 given excellent results in 92 cases in the Allegheny General 

 Hospital. (12) 



This indicates a close analogy between smallpox and hydro- 

 phobia, and suggests to us that hydrophobia may be due to a 

 dual and divisible virus. 



2. ANIMAL POXES. VARIOLATION OF ANIMALS 



There are a number of animal poxes, the most important 

 being smallpox, cow-pox, horse-pox (grease), sheep-pox, and 

 swine-pox. 



We know, from trial and personal observation, that man, 

 ox, horse, sheep, and swine, the respective natural hosts of 

 these diseases, are all subject to vaccinia. 



Immermann(3) says that man is occasionally subject to ovina- 

 tion, the result being a single pock, and says further: 



We have already mentioned and considered in detail the fact that cattle 

 are readily inoculated, not only with humanized vaccinia and human 



