CH. VII] VARIATIONS IN PATHOGENICITY 105 



not only gave rise to atypical symptoms and lesions (namely 

 those of rabies) in the human body in the course of disease 

 but produced no less atypical lesions when inoculated into a 

 rabbit {vide p. 100). 



Again, Savage (1908-9) found in further experiments that 

 a virulent strain of the streptococcus mastitidis from the udder 

 secretion in a case of bovine mastitis, under certain conditions 

 (namely 3 days', residence in the human pharynx), was almost 

 deprived of its characteristic power to produce mastitis in 

 goats. 



Again, Mohler and Washburn (1906) claim that the various 

 types of tubercle bacilli — human, bovine, avian — can be readily 

 converted one into another, byprolbngedresidence in a suitable 

 animal host, so as to be indistinguishable by the ordinary in- 

 oculation tests. 



Rosenow (1914) obtained a strain of haemolysing strepto- 

 cocci from the throat in a case of scarlet fever. A culture on 

 blood agar yielded two distinct kinds of colonies, (a) non-ad- 

 herent colonies of a haemolysing organism which fermented 

 mannite but failed to ferment maltose and saccharose, 

 (6) adherent, green-producing colonies of a non-haemolysing 

 organism which would not ferment mannite but fermented 

 maltose and saccharose. When injected into a rabbit, the 

 former attacked primarily the joints while the latter showed 

 a predilection for the heart valves. In other words, the original 

 strain on artificial cultivation gave rise to two strains which 

 differed in their pathogenicity. 



Finally, may be mentioned Foa's experiments (1890). He 

 inoculated a rabbit with the diplococcus lanceolatus capsulatus 

 with a fatal result. From this dead rabbit he inoculated two 

 others, the first by injecting organisms derived from some of 

 the fresh fibrinous pneumonic exudate in the lung, and the 

 second by injecting organisms derived^om the cerebrospinal 

 fluid. He found that the disease set up in these two rabbits 

 differed. The first rabbit showed, for example, an inflammatory 

 oedema of the skin ; the second did not show this. He found, 

 however, that if the strain isolated from the lung were grown 

 anaerobically and then injected into a rabbit the effects it 



