xiv INTRODUCTION 



oughly understands the nature of ferments and fermentations shall 

 be much better able than he that ignores them to give a fair account 

 of diverse phenomena of certain diseases (as well fevers as others), 

 which will perhaps be never properly understood without an in- 

 sight into the doctrine of fermentations." In the further develop- 

 ment of the origin of infectious disease in living organisms perhaps 

 the work of Rayer and Davaine on anthrax was of the utmost im- 

 portance. They reported in 1850 that in the blood of anthrax vic- 

 tims " are found little thread-like bodies about twice the length of a 

 blood-corpuscle. These little bodies exhibit no spontaneous motion." 

 In 1863 Davaine showed that the blood containing these rods could 

 transmit the disease while blood free from them did not transmit 

 the infectious agent. Davaine suggested at this time that the 

 manifestations of the disease might represent the results of the 

 specific fermentation produced by these bacilli. Such a parasitic concep- 

 tion of disease was further supported by the discovery in 1873 of the 

 spirillum of relapsing fever by Obermeier. Subsequently the work of 

 Louis Pasteur, Koch, and the great school of early bacteriologists gave 

 the final evidence in support of the " contagium vivum." 



Although the essential development of the science of immu- 

 nology necessarily awaited the critical study of infectious disease, 

 as can be seen from the foregoing summary of the development of 

 the knowledge of the cause of infections, yet throughout the ages 

 there had been speculations as to the nature of immunity running 

 hand in hand with hypotheses as to the nature of infection. Im- 

 munology took its most important step forward more than a half 

 century before the work of Schwann had reached its fruition in the 

 studies of Davaine, Obermeier, and Pasteur ; namely, in the master- 

 ful experiments of Jenner. It is almost certain that for at least a 

 century before Jenner's publication there had been practised, in the 

 far and near East as well as in certain parts of Europe, including 

 England, the inoculation of smallpox during full health in order to 

 produce a mild attack of the disease and thus protect against later 

 more severe or fatal attacks. It is indeed possible, as claimed by 

 Carburi, that such a procedure originated in Europe as early as the 

 sixteenth century and was carried to Constantinople and thence to 

 the far East. Similar attempts to produce mild attacks of other 

 diseases were tried, but with little success, as, for example, the work 

 or Vesepremi in 1755 with plague, of Home in 1757 with measles, and 

 of Turenne in 1844 with syphilis. It seems unlikely, however, that 

 any of this work had any direct bearing on the discovery of Jenner. 

 Sprengell states that for many years before Jenner's time the pro- 

 tective influence of cowpox against smallpox was known in certain 

 districts of Ireland, Holstein, Brandenburg, Switzerland, Catalonia, 

 Peru, and the East Indies. Similar observations had been published, 

 as, for example, the statement of Bose in 1769, that persons who 

 had suffered cowpox were not subsequently attacked by smallpox. 

 Jesty in 1774 had inoculated some members of his family with cow- 



