894 DISEASES CAUSED BY F1LTRABLE VIRUS 



smallpox pustule without subsequent disease. With this experiment 

 the principles of vaccination as in use at the present time were 

 founded. 



The question as to the identity of cowpox and smallpox has been 

 the basis of a long controversy. Many observers claimed from the 

 beginning that the two diseases, though closely related to each other, 

 were essentially different. Others, on the contrary, and this seems 

 to be the prevailing opinion among scientists at the present day v 

 maintain that cowpox or vaccinia, as it is called when inoculated 

 into a human being, represents merely an altered and attenuated 

 variety of variola. This latter view is based on the following con- 

 siderations, which we take from Haccius as quoted by Paul. 11 



1. Variola is invariably transmissible to cattle, when proper methods of 

 inoculation are employed. 



2. Variola carried through several animals, in the above way, becomes 

 altered in character, approaching in nature typical vaccinia or cowpox. 



3. Such virus, reinoculated into man, gives rise to purely local lesions 

 which are mild and unlike smallpox. 



4. Inoculation with such virus protects both man and animals against 

 subsequent inoculation with cowpox, and, in the case of man, against smallpox 

 as well. 



Kolmer 12 has carried out complement-fixations, using as antigens 

 salt solution suspensions of cowpox and smallpox virus, and has 

 demonstrated close biological relationship between the two. 



It has been claimed, moreover, that cowpox originally was trans- 

 mitted to cattle by human beings affected with smallpox. This seems 

 likely both because of the comparative rarity of the former disease 

 and because of its spontaneous occurrence almost invariably upon 

 the teats of cows, although both males and females are equally 

 susceptible to experimental inoculation. 



The relationship of variola to chicken-pox or varicella has been 

 more easily determined. Chicken-pox does not protect against small- 

 pox nor is this the case vice versa. The two diseases are unquestion- 

 ably quite distinct. 



The Production of Vaccine. During the early days of vaccina- 

 tion, it was customary to inoculate human beings with the matter 



11 Paul, "Vaccination"; Kraus and Levaditi, "Handbuch, ' etc., L 

 *- Kolmer, Jour, of Immunology, No. 1. Feb., 1916. 



