Virology in order to immunize others. In 1717 Lady Mary Wortley Montagu observed the practice in Istanbul and attempted to popularize it in Britain, but encountered considerable resistance. In 1796 Edward Jenner developed a much safer method, using cowpox to successfully immunize a young boy against smallpox, and this practice was widely adopted. Vaccinations against other viral diseases followed, including the successful rabies vaccination by Louis Pasteur in 1886. The nature of viruses however was not clear to these researchers. In 1892, the Russian biologist Dmitry Ivanovsky used a Chamberland filter to try to isolate the bacteria that caused tobacco mosaic
German retribution against Poles who helped Jews possible to organise public protests against deportations of the Jewish population. Calculations by Teresa Prekerowa show that only 1% to 2.5% of the adult Polish population was involved in helping Jews. However, the number of helpers was also very small in the countries of Western Europe - although hiding Jews there was associated with an incomparably lower risk. Assuming the percentage of the population of European countries, which in 1945 was made up of Jews who survived the Holocaust, Poland did not differ from the average in other occupied states. On the other hand, in the Netherlands, where few Jews