PATHOGENICITY FOR EXPERIMENTAL ANIMALS 183 



isms through the nodes at the hilum and thence through the tho- 

 racic duct into the circulatory system. The author believed that 

 the process was, in its essentials, comparable to that occurring in 

 spontaneous pneumonia in human beings, the chief difference being 

 a more intense interstitial involvement in the experimental disease. 



Through the insufflation of the lung with cultures of pneumo- 

 cocci of Types I, II, and III, and of Group IV, Gaskell (1925) 500 

 reported that organisms of Group IV possessed a greater patho- 

 genicity for the rabbit than those of Type I which, in turn, were 

 more invasive than those of Type II, while the Type III culture 

 employed was the least virulent of all. 



Stuppy and Falk (1931) 1352 found that intrabronchial insuffla- 

 tion of rabbits with cultures of pneumococci of uniformly high 

 virulence gave rise to bronchopneumonia which, with septicemia 

 and a generalized distribution of cocci in the lungs, usually caused 

 the death of the animal in two to five days. In some animals there 

 was acute inflammation of the interstitial tissue of the lung, with 

 perivascular and peribronchial lymphangitis. Suppurative bron- 

 chitis and pleuritis were only occasionally seen. On the whole, the 

 pulmonary lesions induced in rabbits by strains of Type I, II, and 

 III pneumococci of the same virulence were quite similar, while in- 

 dividual virulence rather than the serological type of the culture 

 employed appeared to be the important factor in establishing in- 

 fection. In a study of the effects of the inhalation of pneumococci, 

 Stillman 1336 observed that, following the spraying of rabbits with 

 cultures of virulent Type III cultures, the organisms tended to re- 

 main in the lungs for a considerable period of time without invad- 

 ing the blood stream. When once the organisms had reached the 

 blood, a fatal septicemia resulted. The course of events was in con- 

 trast to that ensuing after the similar administration of Type I 

 and II strains. Organisms of Types I and II frequently entered the 

 circulation, but in such instances, only a relatively small number of 

 the animals died. 



Another organ of the rabbit possessing little or no resistance to 



