ANTIGENICITY OF PNEUMOCOCCUS 339 



evidence was advanced to show that the immunity was antitoxic in 

 nature. 



In 1912, Rosenow 1168 obtained from pneumococci a poisonous 

 substance, similar to histamine in its action, but wholly incapable 

 of provoking any immune response. Larson, 788 and then Olson 

 (1926), 1029 believed that Pneumococcus contained a toxin and that 

 by injecting animals with whole cultures of the organism treated 

 with sodium ricinoleate, or with autolyzed broth cultures, it was 

 possible to produce an antitoxic serum. The assumption was based 

 solely on the physiological effect of the serum and not on any 

 demonstration or titration of the antitoxin which the serum was 

 supposed to contain. 



The work of Parker 1061 and of Parker and McCoy (1929) 1062 is 

 more suggestive. By allowing pneumococci of Types I, II, and III 

 to autolyze under strict, anaerobic conditions, the authors ob- 

 tained a preparation that was toxic for guinea pigs and for horses 

 and which, when injected repeatedly into horses over a period of 

 eight months, caused the animals so treated to develop in the serum 

 substances capable of neutralizing in vitro the toxic autolysates. 

 Parker reported that antipneumotoxic serum produced in rabbits 

 or horses by immunization with sterile filtrates of pneumotoxin af- 

 forded heterologous protection to guinea pigs — at least as far as 

 Type I or Type II pneumococci were concerned — against the de- 

 velopment of pneumonia, while the serum of some of the treated 

 horses exerted a curative action against infection with pneumo- 

 cocci of the homologous type, but contained little if any antitoxin 

 for heterologous types. Furthermore, since the serums contained 

 no specific protective antibodies against pneumococci, Parker con- 

 cluded that the serum was antitoxic in action. 



The experiments of Parker and McCoy, including a definite de- 

 termination of the toxic power of sterile pneumococcal autolysates 

 and of the neutralizing strength of serum produced in response to 

 the injection of the autolysates, with evidence of the absence of 

 specific protective antibodies, constitute the first accurately con- 



