PATHOGENICITY FOR EXPERIMENTAL ANIMALS 181 



tion in reality was a subcutaneous one, since it was necessary to 

 injure the membrane by scratching it before infection took place. 



Intravenous inoculation. The rapid and frequently fatal infec- 

 tion resulting from the injection of pneumococci into the circula- 

 tory system has often been utilized for testing the specific resist- 

 ance of rabbits after various immunizing treatments. Among the 

 many references, there might be mentioned the observations of Til- 

 lett (1927) 1403 " 4 who, in attempts to stimulate the production of 

 immune bodies, discovered differences in the pathogenicity of cer- 

 tain Type III strains for man and for rabbits. Some of the strains 

 isolated from human sources, despite the possession of large cap- 

 sules and high virulence for mice, exhibited low virulence for rab- 

 bits. The intravenous injection of the Type III strains avirulent 

 for the species produced a non-fatal bacteriemia which, however, in 

 its course differed from that caused by non-encapsulated, rough 

 forms of pneumococci. 



Intradermal inoculation. In 1928, Goodner 525 " 6 described the 

 acute and often fatal infection developing in the rabbit following 

 the introduction of Type I Pneumococcus into the skin. After the 

 injection of a small quantity of a broth culture of the organism 

 into the skin at the midline of the abdomen, within eight to twelve 

 hours there appears a local lesion, consisting of a swollen, edema- 

 tous area which may spread until the whole midabdominal region is 

 involved. The development of the lesion is accompanied by an 

 abrupt rise in temperature and invasion by the cocci of the blood 

 stream. A varying proportion of the animals so treated spontane- 

 ously recover and, as a result of the infection, may become tempo- 

 rarily immune. Goodner pointed to the analogy between the nature 

 of the localized and subsequent systemic infection arising after in- 

 tradermal inoculation of the rabbit with Pneumococcus and that of 

 lobar pneumonia in man. Since it does not come within the province 

 of the present volume to discuss, except in a cursory way, the path- 

 ological processes caused by pneumococcal infection, the reader 



