PNEUMOTOXINE. 159 



The poison is very sensitive to external influences. Even at 

 the ordinary temperature the toxic power of the solutions rapidly 

 decreases, and this loss takes place more rapidly at high summer 

 temperatures (25 C.) and immediately at 70 C. It is true that 

 nitrates thus heated are still poisonous to guinea-pigs and rabbits 

 when introduced in large doses, but in quite a different way, 

 possibly on account of the formation of toxoids. 



MARKL has also endeavoured to purify plague toxine, but his 

 experiments (precipitation with alcohol) are little more than 

 preliminary. He has found that it is intimately associated, 

 like all true toxines, with albuminous substances. 



It is probable that he was dealing, in the main, with 

 secondary poisons which are formed in such old cultures. 

 They cause a formation of antitoxine, even if only to a slight 

 extent. 



KOSSEL and OvERBECK/too, succeeded in producing immunity 

 by means of filtered cultivations that had been heated to 60 C. 



PNEUMOTOXINE. 



The state of affairs with regard to pneumococcus, the cause 

 of croupous pneumonia, appears to be very similar to that found 

 in the case of cholera and typhoid. 



The first important experiments throwing light upon the poison 

 of this diplococcus were those carried out by the brothers KLEM- 



PERER. 2 



They attempted to produce immunity by means of cultures 

 which, although weakened or inhibited, still contained the cells 

 of the cocci ; but they also employed germ-free solutions for the 

 purpose. 



They tried not only the simple filtrates from cultivations, but 

 also a purulent pleural exudation of which the pneumococcus was 

 the exciting cause, and which had been proved experimentally 

 to be free from bacteria, in addition to the heated sputum of 

 pneumonia patients and glycerin extracts of agar cultivations 

 filtered from the cells of the bacteria. 



In this way they obtained fairly weak toxic substances pro- 

 ducing no specific effects ; by heating these products to 60 C. 



1 Kossel and Overbeck, " Bakt. Unters. uber Pest," Arb. Kaiserl. Ges.- 

 Amt., xviii., 1901. 



2 G. and F. Klemperer, "Vers. iiber Immunisierung u. Heilung bei der 

 Pneumokokkeninfektion," Berl. Ein. Woch., 1891, Nos. 34, 35; G. Klem- 

 perer, "Die Bezieh. versch. Bakteriengifte z. Immunitat u. Heilung," 

 Zeit.f. klin. Med., xx., 165, 1892. 



