ANTIGENICITY OF PNEUMOCOCCUS 335 



from lobar pneumonia was followed by a rapid drop in tempera- 

 ture and relief of subjective symptoms. Larson believed that the 

 effect was due to the presence of antitoxin in the serum. 



In a later communication, Larson 789 reported that the intraperi- 

 toneal injection of large amounts of soaped pneumococci of Types 

 I, II, and III protected rabbits against infection induced by the 

 Goodner technique, and claimed that by this method it was possi- 

 ble to produce both species-specific and type-specific immunity. 



Sensitized Pneumococci 



The use of pneumococci sensitized with homologous immune se- 

 rum was described by Levy and Aoki (1910), 801 while Alexander, 7 

 after similarly treating and incubating the cocci with leucocytes, 

 could immunize rabbits with the preparations. Protective sub- 

 stances appeared in the serum of the animals within eight to eleven 

 days after the first injection, but the method possessed no advan- 

 tages over the use of heat or formalin for the preparation of anti- 

 gens. Levy and Aoki, and also Killian, 704 employed phenol as a 

 devitalizing agent, but the latter author found that phenolized 

 vaccines showed a definite loss of immunizing power after six weeks' 

 preservation. 



Filtrates and Extracts 



CULTURE FILTRATES AND BACTERIAL EXTRACTS 



Early investigators turned to culture filtrates and to other 

 products and derivatives of Pneumococcus in a search for some 

 principle which would increase the resistance of experimental ani- 

 mals and eventually of man to pneumococcal infection. 



Warden (1912) 1485 claimed to have immunized rabbits with pan- 

 creatic extracts of pneumococci and made the additional observa- 

 tion, which apparently has never been confirmed, that similar ex- 

 tracts of staphylococci and pancreatic extracts alone were capable 

 of inducing immunity in infected and non-infected rabbits, and of 



