INTRODUCTION xv 



pox and reported that they remained free from smallpox. In 1791 

 Jensen and Plett practised protective inoculation with cowpox and 

 reported good results, as did also Penster in 1765. None of these 

 studies, however, bore critical scientific examination, nor did they 

 serve to stimulate active work along this line. Indeed, it seems un- 

 likely that they influenced Jenner in any way. Jenner brought to 

 bear the critical method of the experimental investigator and proved 

 the point. The method was rapidly put into clinical practice, 

 spread over the British Isles and Europe and stood the test of 

 time and wide application. With very slight modifications it stands 

 to-day, in spite of our great advances in the study of immunity^as 

 the most effective method we have to guard against infectious dis- 

 ease. Jenner vaccinated a boy on the arm with cowpox virus ob- 

 tained from a lesion on the hand of a dairy maid, and subsequently 

 inoculated the boy with fresh smallpox virus, which failed to pro- 

 duce the disease. He also reported an attempt to inoculate small- 

 pox unsuccessfully in ten persons who had had cowpox nine 

 months to fifty-three years previously. In 1800 Waterhouse in 

 Boston repeated the experiment of Jenner on his own son, and in 

 1802 performed a more extensive and even more critical experi- 

 ment, in which he vaccinated nineteen boys with cowpox. Twelve 

 were inoculated with smallpox virus three months later and failed 

 to develop the disease, the same virus being inoculated at the same 

 time into two unvaccinated boys, producing well-developed small- 

 pox. The virus from these latter two boys was later inoculated into 

 all the iiineteen vaccinated boys without, results. Thus began the 

 period of experimental investigation of the phenomena of immunity. 

 Further progress of importance was not made until 1880, when 

 Pasteur announced his results in vaccination against chicken 

 cholera. No brief review such as this can do justice to the stimulus 

 to modern biological science furnished by this man and his asso- 

 ciates, and the reader is referred to the interesting and intimate 

 view of the life of Pasteur written by Valery Radot, his son-in-law. 

 At the beginning of Pasteur's work the theory of spontaneous gen- 

 eration was still generally accepted by the scientific world, and be- 

 fore he was compelled to cease his active investigations not only 

 had this theory been overthrown, but also the ideas of chemists in 

 regard to crystallization and to the rotation of light by bodies in 

 solution had been completely revised, the silk and wine industries 

 of France, and indeed of the world, had been entirely rejuvenated, 

 the bacteriological cause of numerous diseases conclusively proven, 

 and the science of immunology put on a plane where its progress 

 must be uninterrupted. His first contribution to the science of im- 

 munology was in connection with his work on chicken cholera. 

 Although he did not offer it as such, nevertheless, this incident well 

 illustrated his doctrine that " chance favors the prepared mind." He 

 had saved some old cultures of this bacterium and later found that 

 they were avirulent. He subsequently tried to cause the disease in 



