EXPERIiMENTAL INOCULATION. 



215 



¥" 



Thus in children the primary source of infection is in a great 

 many cases an otitis media, and Netter concludes that infection 

 takes place in such conditions from the nasal cavities. 



Experimental Inoculation. — The. ptu-itmococcus oi Fraenkel is 

 pathogenic to various animals, though the effects vary somewhat 

 with the virulence of the race used. The susceptibility of 

 different species, as Gamaleia has shown, varies to a consider- 

 able extent. The rabbit, and especially the mouse, are very 

 susceptible; the - 



guinea-pig, the 

 rat, the dog, 



and the sheep , . ..^ 



occupy an inter- •. •" *" , 



mediate posi- 

 tion; the pigeon 

 is immune. In 

 the more sus- 

 ceptible animals 

 the general 

 type of the dis- 

 ease produced 

 is not p n e u- 

 monia, but a 

 general septice- 

 mia. Thus, if 

 a rabbit or a 

 mouse be in- 

 jected s i m u 1- 

 taneously with 



pneumonic 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. 84). 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. 

 We have already stated that cultures of the pneumococci on 

 artificial media in a few days begin to lose their virulence. 



Fig. 84. — Capsulated pneumococci in blood taken from the 

 heart of a rabbit, dead alter inoculation with pneumonic sputum. 

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

 fuchsin and partly decolorised. X looo. 



