328 BIOLOGY OF PNEUMOCOCCUS 



servations on the comparative antigenic action of pneumococci 

 when in the living and in the dead state.* In 1902, Neufeld 974 ob- 

 tained satisfactory agglutinating serum by the injection of rabbits 

 with either living or heat-killed pneumococci, but for the routine 

 preparation of immune serum he gave the animals, first, heat-killed 

 cultures, and then living cultures. Wadsworth, 1457 in 1912, claimed 

 that only after immdnization with living, virulent cultures did the 

 serum acquire marked curative properties. 



Cotoni and Brasie 281 made a comparative study of the immuniz- 

 ing effect of pneumococci heated at 56°, of cultures treated with 

 alcohol and ether and suspended in salt solution, and of these sus- 

 pensions heated for fifteen minutes at 110°. The heat-killed cocci 

 proved to be far superior to the other antigens in protecting rab- 

 bits against infection. 



The influence on antigenic action of varying exposures of pneu- 

 mococci to different temperatures was investigated by Tani. 1379 Ac- 

 cording to the results obtained, cultures of Type I pneumococci 

 incubated for a long period at 39°, when injected intraperitone- 

 al^ into mice, were found to have lost virulence and were feeble 

 immunizing agents ; cocci heated for two and one-half hours and 

 not completely killed showed poor immunizing power, whereas an- 

 other specimen heated at the same temperature for an equal length 

 of time and completely killed, and then later heated for one-half 

 hour at 56°, gave good protection. After subjecting a similar cul- 

 ture to a four hours' exposure at 100°, it was still antigenic in 

 that it afforded protection to mice. Tani's results point to viru- 

 lence as an essential property of cultures used for immunization. 

 Davidson, 298 too, tested the antigenic action of living pneumococci, 

 of heat-killed cultures, and of detoxified and defatted vaccines. 

 Rabbits injected with the killed cultures acquired immunity, and 

 the serum contained protective substances. The living cultures pro- 



* These facts and many similar observations by others have never been pub- 

 lished but are widely current in the stable lore of manufacturing laboratories. 



