EXPERIMENTAL INOCULATION 243 



different species, as Gamaleia has shown, varies to a considerable 

 extent. The rabbit, and especially the mouse, are very sus- 

 ceptible ; the guinea-pig, the rat, the dog, and the sheep 

 occupy an intermediate position ; the pigeon is immune. In 

 the more susceptible animals the general type of the disease 

 produced is not pneumonia, but a general septicaemia. Thus, if 

 a rabbit or a mouse be injected subcutaneously with pneumonic 



FIG. 69. Capsulated pneuniococcus in blood taken from the heart 

 of a rabbit, dead alter inoculation with pneumonic sputum. 



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

 fuchsin and partly decolorised, x 1000. 



sputum, or with a scraping from a pneumonic lung, death 

 occurs in from twenty-four to forty-eight hours. There is some 

 fibrinous infiltration at the point of inoculation, the spleen is 

 often enlarged and firm, and the blood contains capsulated 

 pneumococci in large numbers (Fig. 69). If the seat of inocula- 

 tion be in the lung, there generally results pleuritic effusion on 

 both sides, and in the lung there may be a process somewhat 

 resembling the early stage of acute croupous pneumonia in man. 

 There are often also pericarditis and enlargement of spleen. 



