15-85 



13-00 

 8-53 

 2-44 

 1-22 

 1-22 

 In 29 the primary affection 



EXPERIMENTAL INOCULATION 233 



« 



pneumococcus. A large number of cases have been investigated 

 by Netter, who gives the following tables of the relative fre- 

 quency of the primary infections by the pneumococcus in man : — 



(1) In adults- 

 Pneumonia . . . .. 65-95 per cent. 

 Broncho-pneumonia [ 

 Capillary bronchitis \ 

 Meningitis ... 

 Empyema 

 Otitis 



Endocarditis 

 Liver abscess . ... 



(2) In children 46 cases were investigated, 

 was otitis media, in 12 broncho-pneumonia, in 2 meningitis, in 1 pueu 

 monia, in 1 pleurisy, in 1 pericarditis. 



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. 



As bearing on the occurrence of pneumococcal infections 

 secondary to such a local lesion as pneumonia, it is important to 

 note that in a large proportion of cases of the latter disease the 

 pneumococcus can be isolated from the blood. 



Experimental Inoculation. — The pneumococcus of 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 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 septicemia. Thus, if 

 a rabbit or a mouse be injected subcutaneously 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. 61). 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 pneumococcus on 

 artificial media may lose their virulence. Now, if such a partly 

 attenuated culture be injected subcutaneously into a rabbit, there 

 is greater local reaction ; pneumonia, with exudation of lymph 



