There are many tropical and sub-tropical diseases against which recent knowledge opens out the prospect of complete control through exact biological knowledge. Among the diseases against which protection was most urgently needed was Small Pox. This disease has been one of the greatest scourges of mankind for many ages. In the east, it had long been known that inoculation of small pox virus under favourable conditions produced a milder attack than disease arising from infection naturally derived. In 1768 Dr. Dimsdale inoculated Catherine, Empress of Russia; and between 1750 and the introduction of vaccination by William Jenner in 1799, a large part of the total population was inoculated. Edward Jenner took some of the vaccine virus from Sarah Nelms hand on May 14th, 1796, and vaccinated James Phipps with this matter on his arm. On July 1st he was inoculated with variolous matter directly abstracted from a small pox patient.