40 ADAPTATION AND DISEASE 



Following the classical experiment on adaptation of Dallinger 1 

 in the 'seventies, they first gradually accustomed the bacilli 

 to grow at body temperature by cautiously increasing the tem- 

 perature of growth, degree by degree, over a considerable period, 

 until they would multiply instead of being killed at 37-5° C. Next 

 they sensitized animals by injecting into them a fair dose of 

 the killed bacilH. Ten or fifteen days later they gave a second 

 injection of the live bacilh, recovered the bacilli from the tissues 

 of the animals, and repeated the process with another animal 

 of the same species. 



Doing this they found that the bacillus which had been 

 motile lost its flagella, acquired a capsule, became stumpier and 

 thicker, and, to their astonishment, acquired all the characters 

 of the anthrax bacillus, both morphologically and in the 

 lesions it produced. The harmless, naturally non - pathogenic 

 bacillus became in fact so virulent that a small amount of 

 the culture introduced into guinea-pigs killed them in twelve 

 hours. 



Nor is this the only non-pathogenic organism that these 

 observers have induced to become pathogenic by this method 

 of prehminary anaphylaxis. They have obtained parallel results 

 with other non-pathogenic microbes (B. phlei, B. smegmatis, etc.). 



Their work has been confirmed independently by Kniest 

 Paber, 2 who noted that employing virulent streptococci he 

 obtained arthritis in rabbits upon a first injection, but with a 

 weakly pathogenic form such as Streptococcus mitis var. viri- 

 dans he found that in order to set up the lesions of arthritis 

 he had to give rabbits two sensitizing doses ; that these doses 

 had to be narrowly specific ; he had, that is, to employ the 

 particular strain of streptococcus. Prehminary intravenous in- 

 jections of the S. mitis set up no arthritis, but if he injected it 

 direct into the knee-joint, so setting up a localized arthritis 

 of the one joint, allowed this to subside, and now gave an 

 intravenous injection of the same organism, there followed 

 immediately an acute arthritis of the treated joint. This form 



1 Proc. Boy. Soc. xxvii., 1878, 332. Dallinger, it may be recalled, gradually, 

 over long months, raised the temperature at which the flagellate infusorian, 

 Dattingeria drysdalei (Kent), would grow and multiply, from 60° F. to 168° P. 

 (=70° C.) — i.e. some 20° C. higher than that causing the death within a few 

 minutes of ordinary (untreated) vegetative infusoria. 



2 Journ. of Exper. Med. xxii., 1915, 615. 



