SMALLPOX 659 



for centuries that one attack of smallpox protects against subsequent 

 attacks. This knowledge was made use of by the physicians of ancient 

 China and India, who, during mild epidemics, exposed healthy children 

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

 immunity. WhUe 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 imnecessary by the classical 

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

 had been impressed with the fact that coimtry-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.^ 



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

 of inoculation are employed. 



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

 comes altered in character, approaching in nature typical vaccinia or 

 cowpox. 



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

 which are mUd and unHke 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. 



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



^Jenrter, "Inquiry into the Causes and Effects of the Variola^ Vaccinae," 

 London, 1798. 



'Paid, "Vaccination"; Kraus and Levaditi, "Handbuch,'' etc., I. 



