Pathogenesis 293 



Vital Resistance. Bordoni-Uffreduzzi found that when 

 pneumococci were dried in sputum attached to clothing, 

 and were exposed freely to the light and air, they retained 

 their virulence for rabbits for from nineteen to ninety-five 

 days. Direct sunlight destroyed their virulence in twelve 

 hours. Guarniere found that dried blood containing pneu- 

 mococci remained virulent for months. 



Metabolic Products. Hiss* found that the pneumococcus 

 produces acid with ease from monosaccharids, disaccharids, 

 and such complex saccharids as dextrin, glycogen, starch, 

 and inulin. 



Toxic Products. Nothing definite is known about the 

 metabolic toxic products of the pneumococcus. That the 

 symptoms of pneumonia are not entirely dependent upon 

 the disturbance of respiration is clearly shown by the fact 

 that the patients suffer from high fever and have marked 

 leukocytosis with enlargement of the spleen. The cases in 

 which the cocci invade the blood are usually more serious 

 than those in which their operations are restricted to the 

 lung. 



The toxin must be purely or almost purely intracellular, 

 however, as filtered cultures are scarcely at all toxic. 



Auld f found that if a thin layer of prepared chalk were 

 placed upon the bottom of the culture-glass, it neutralized 

 the lactic acid produced by the pneumococcus, and enabled 

 it to grow better and produce much stronger toxin. 



Pathogenesis. If a small quantity of a pure culture 

 of the virulent organism be introduced into a mouse, 

 rabbit, or guinea-pig, the animal dies in one or two days. 

 Exactly the same result can be obtained by the introduction 

 of a piece of the lung-tissue from croupous pneumonia, 

 by the introduction of some of the rusty sputum, and 

 frequently by the introduction of human saliva. Post- 

 mortem examination of infected animals shows an inflamma- 

 tory change at the point of subcutaneous inoculation, with 

 a fibrinous exudate similar to that succeeding subcutaneous 

 inoculation with the diphtheria bacillus. At times, and 

 especially in dogs, a little pus may be found. The spleen is 

 enlarged, firm, and red-brown. The blood with which the 

 cavities of the heart are filled is firmly coagulated and, like 

 that in other organs of the body, contains large numbers 



*"Jour. Exp., Med.," vn, No. 5, Aug. 25, 1905. 

 t " Brit. Med. Jour.," Jan. 20, 1900. 



