504 INFECTION AND IMMUNITY. 



which the coccus possesses as a parasite, increases its 

 resistance. When dried and powdered it is much 

 less resistant, being killed by direct sunlight in 

 about an hour. Like other bacteria, it resists 

 diffuse sunlight better than direct, and in the 

 former may live for as long as 55 days in a dried 

 state (Bordoni-Uffreduzzi, cited by Weichsel- 

 baum). It has very little resistance to heat, being 

 killed by a temperature of 52 C. for ten minutes. 

 Toxic No characteristic soluble toxin has been obtained, 

 although more or less poisonous substances, some 

 of them of a chemical nature, have been described. 

 Presumably the toxic properties reside in an endo- 

 toxin. The pneumotoxin of F. and G. Klemperer 

 was prepared by precipitation with alcohol. The 

 pneumococcus is a pyogenic organism and causes 

 exudates which are rich in fibrrh. Occasionally 

 serous rather than purulent exudates are produced. 

 Its toxic action is directed toward various organs, 

 and it is doubtful if any of the tissues of the body 

 are non-susceptible. Some strains are supposed to 

 be more neurotoxic than others. 

 suscepti- The susceptibility of animals varies greatly. 



bility of r . J 



Animals. Rabbits and mice are extremely susceptible and are 

 used as test animals for the identification of the 

 organism. Other laboratory animals have greater 

 resistance, and the pigeon and chicken are almost 

 absolutely immune. In susceptible animals a rap- 

 idly fatal coccemia or more or less extensive local 

 lesions are produced, depending on the virulence of 

 the culture, the seat of inoculation and the suscep- 

 tibility of the animal. In rabbits lobar pneumonia 

 has been produced by inoculation into the pleura, 

 trachea, blood stream or subcutaneous tissue. 



