ANTIGENICITY OF PNEUMOCOCCUS 337 



young rabbits resisted intratracheal inoculation with a virulent 

 culture, and that resistance could be increased by repeated in- 

 halation of the preparation. The attenuating action of filtered 

 broth cultures of pneumococci on fresh cultures of the same or- 

 ganism was reported by Okischio (1932), 1023 but the use of anti- 

 virus either for the preparation of vaccines or for the treatment 

 of pneumococcal infections has not come into general use. 



There are yet other references to the use of extracts and au- 

 tolysates of Pneumococcus for the purpose of inducing immu- 

 nity. Among them might be mentioned those of Day (1930 and 

 1934 ) 307 ' 309 who reported that the intraperitoneal injection into 

 mice of autolysates of both Type I and Type II cultures was fol- 

 lowed one week later by protection against one thousand to ten 

 thousand fatal doses of culture. Another communication was that 

 of Harley (1934) 591 in which was reported the preparation of an- 

 tigens by extracting Type I and II pneumococci with 0.05N hy- 

 drochloric acid at 60°. 



TISSUE EXTRACTS AND EXUDATES 



The possibility that products arising from the vital activities of 

 Pneumococcus in animal tissues might exert immunizing action and 

 that such products might be applied to the protection or treat- 

 ment of animals and human beings has not been neglected. Foa 

 and Carbone, 463 Bonome (1891), 137 and Mosny (1892) 932 were 

 thus able to render rabbits relatively invulnerable to the injection 

 of otherwise lethal doses of pneumococcal cultures. Hartman 

 (1913) 598 studied the antigenic action of the principal constituents 

 of pneumonic exudates, but the results were largely negative. 

 Freedlander (1928) 480 employed saline extracts of organs of in- 

 fected rabbits as antigens and, after three injections at five to 

 seven-day intervals into normal rabbits, obtained a serum of high 

 protective titer for mice against Type I Pneumococcus and a se- 

 rum of somewhat less potency against a Type II culture. While 

 the serums compared favorably in protective action with thera- 



