EXPERIMENTAL INOCULATION. 197 



relatively lower susceptibility is only marked by the fatal 

 dose being larger. In sheep, however, greater immunity is 

 marked by the occurrence, after subcutaneous inoculation, 

 of an enormous local sero-fibrinous exudation, and by the 

 fact that few pneumococci are found in the blood stream. 

 Intra-pulmonary injection in sheep is followed by a typical 



FIG. 55. Capsulated pneumococci in blood taken from the heart of a 

 rabbit, dead after inoculation with pneumonic sputum. 



Dried film, fixed with corrosive sublimate. Stained with carbol-fuchsin 

 and partly decolorised. x 1000. 



pneumonia, which is generally fatal. The dog is still 

 more immune, but in it also intra-pulmonary injection is 

 followed by afibrinous pneumonia, which is only sometimes 

 fatal. Inoculation by inhalation appears only to have been 

 performed in the susceptible mouse and rabbit, and the 

 effects were similar to those of subcutaneous injection. 



