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to infection, hoping that mild attacks would result which would confer 

 immunity. While dangerous in the extreme, such "variolation," never- 

 theless, was not without some benefit and was even introduced into 

 Europe in the eighteenth century by Lady Mary Wortley Montagu. 



Such practices, however, were made unnecessary by the classical 

 investigations of Jenner * published in 1798. Jenner, as a student, 

 had been impressed with the fact that country-people who had been 

 infected with a disease known as cowpox, were usually immune against 

 smallpox. His studies and observations came to a practical issue when, 

 in 1796, he inoculated a boy, James Phipps, with pus from a cowpox 

 lesion on the hand of an infected dairy-maid. Two months later the 

 same boy was inoculated with material from a 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 be- 

 ginning 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, 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 considerations, which we take from 

 Haccius as quoted by Paul. 2 



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

 oculation are employed. 



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

 tered 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 subse- 

 quent inoculation with cowpox, and, in the case of man, against smallpox as well. 



Recently Kolmer 3 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 



1 Jenner, "Inquiry into the Causes and Effects of the Variola- Vaccinse," London, 

 1798. z Paul, "Vaccination"; Kraus and Levaditi, "Handbuch," etc., I. 



3 Kolmer, Jour, of Immunology, No. 1, Feb., 1916. 



