EXPERIMENTAL PRODUCTION OF PATHOGENICITY 37 



speaking, Ms observations and hypotheses gain confirmation 

 from the clinical observations of Billings 1 and the Chicago 

 school. I like to flatter myself with the thought that an address 

 which I delivered in Chicago in 1899 2 was the starting-point 

 for these activities. 



The Experimental Conversion of non-Pathogenic into 

 Pathogenic Microbes 



Years ago Vincent, one of the most distinguished of French 

 bacteriologists, to whom we owe the recognition of the relation- 

 ship between the- Bacillus fusiformis and Vincent's angina, or 

 better, Vincent's disease, 3 described how by placing broth cultures 

 of a perfectly harmless, non-pathogenic microbe from the soil, 

 the Bacillus megatherium, in hermetically sealed celloidin 

 capsules, and inserting the capsules within the tissues of lower 

 animals, he was able to accustom, or adapt, them to growth 

 within the organism of warm-blooded animals. 4 By simple 

 subcutaneous or intramuscular injection of a few ccm. of a 

 broth culture of this bacillus into the rabbit, for example, no 

 harmful results ensue : the bacilli are rapidly destroyed. Placed 

 in delicate celloidin capsules the bacilli gain nourishment from 

 the diffused lymph, and are at the same time protected from 

 the phagocytic action of the leucocytes. By this means he an- 

 nounced that the bacilli gradually gained pathogenic properties. 

 That was close upon twenty years ago, and unfortunately I 

 cannot hear that this experiment of Vincent's has been repeated 

 and confirmed. When some years ago, in my laboratory at McGill, 

 Dr. Charles Higgins employed this method with tubercle bacilli 

 of the typus humanus, inserting celloidin capsules containing a 

 glycerine broth culture of these into the tissues of the calf, even 

 after some months he obtained no clear evidence of modification. 

 The capsules became surrounded by dense fibrous tissue, and 

 where the cultures did not die out they showed no assumption 



1 Local Infection, Appleton, 1916. 



2 " Latent Infection and Subinfeotion," American Medical Assoc. Journal, 

 Deo. 1899. 



3 Better, because, as Vincent himself pointed out, the organism may be 

 associated not merely with a tonsillitis (angina), but also with a speoial form of 

 stomatitis and gingivitis, while also the conjunctiva may be affected, and the 

 organism may grow upon the glans penis, setting up a balanitis. 



4 Ann. de Vlnst. Pasteur, xii., 1898, 785. 



