530 BIOLOGY OF PNEUMOCOCCUS 



which suspensions of pneumococci may be rendered non-infective 

 but which will preserve a maximum of antigenicity. 



Methods of devitalizing the organism: heat and formalin. Heat 

 has long been employed as a means of devitalizing organisms to be 

 used for immunization purposes. Mosny 932 recommended the heat- 

 ing of cultures for three hours at 60°. Washbourn 1487 advocated a 

 temperature of 60°, but for a period of only one hour, and Neufeld 

 and Haendel 989 also utilized the same temperature. In preparing 

 killed suspensions of pneumococci, Avery, Chickering, Cole, and 

 Dochez 36 heated the coccal suspensions in the water-bath at 56° 

 for one-half hour. Truche (1920) 1420 preferred vaccines killed by 

 alcohol and ether, since he stated that heat-killed suspensions were 

 not tolerated well by horses. In a study of the effect of the degree 

 and period of heating on the antigenicity of pneumococci, Tani 1379 

 obtained better immunization with vaccines subjected to 100° than 

 with those heated at lower temperatures. The period of heating 

 varied from ten minutes to four hours. A culture heated at 45° for 

 two and one-half hours was found to have low immunizing value. 

 In the investigations of Gaspari, Sugg, Fleming, and Neill, 503 in 

 which a large number of rabbits were used as test animals, the in- 

 fluence of heat on the antigenic strength of the type-specific and 

 species-specific antigens of the Type II pneumococci was studied. 

 The temperatures varied from 55° to 120° applied for a period of 

 one-half hour, and the results indicated that heating pneumococ- 

 cal suspensions tends to decrease the effectiveness of the species- 

 specific antigen without having any appreciable influence on the 

 antigenic power of the type-specific complex. 



Chemical agents have also been employed in preparing pneumo- 

 coccal vaccines for animal immunization. The use of alcohol and 

 ether has already been mentioned, while glycerol extracts have also 

 been tried. Takami 1374 used carbolized cultures with rabbits, but 

 there appear to be few adherents to the practice. By the subcu- 

 taneous injection of horses with ricinoleated cultures, or with ster- 

 ile pneumococcal "toxin," Clowes, Jamieson, and Olson 244 reported 



