ii8 CONTEMPORARY SCIENCE 



by Pasteur and related to Jennerian vaccination. His 

 great discovery then consisted in the determination that 

 pathogenic or disease-producing microbes may be modified 

 otherwise than by passing through foreign and relatively 

 insusceptible animal species, and that such simple agencies 

 as long cultivation in vitro (fowl cholera), high tempera- 

 tures and therefore non-optimal conditions of growth 

 (anthrax), and partial drying of the animal material car- 

 rying the microbe (rabies), would suffice so to modify 

 and attenuate the respective microbes that upon inocula- 

 tion they set up not the severe, but only mild states of 

 infection, from which not only does recovery ensue, but 

 the restored animal is enduringly protected from the ordi- 

 nary and often fatal attacks of a disease. 



Looking backward from our present higher position of 

 vantage, we may discern certain minor imperfections in 

 this fundamental work on artificial immunity. For ex- 

 ample, it would now appear that the so-called attenuated 

 cultures of the bacillus of fowl cholera, used for purposes 

 of immunization, were not so much attenuated as actually 

 dead, and that the material inoculated consisted of a mix- 

 ture of dead bacilli and their metabolic and disintegrative 

 products. In other words, it seems that Pasteur without 

 perceiving it had discovered not only a principle of wide 

 applicability in inducing artificial immunity, but a gen- 

 eral method of utilizing dead bacteria as vaccines, and 

 one which in more recent times has been widely resorted 

 to in preventing outbreaks of typhoid fever, cholera, and 

 some other diseases. 



In 1882 antirabic inoculation was perfected. Pasteur 

 had, of course, reflected deeply on the sources of the im- 

 mune state and in explanation of it he inclined to the 

 view that the basis of the phenomenon was a nutritive 

 condition. He conceived that in the course of that form 

 of microbic development within the body which came to a 

 spontaneous end and left the individual protected, certain 

 essential foodstuffs were consumed, in virtue of which 



