362 PATHOGENIC MICROORGANISMS 



In complications of pneumonia, pneumococci are found usually in 

 the pleura where they may cause a simple dry pleurisy or even empy- 

 ema. Less frequently they may cause pericarditis and endocarditis. 

 Meningitis may be either secondary to pneumonia or independent. 

 Such cases are grave, almost invariably ending in death. Other lesions 

 which may be caused by pneumococci, either as post-pneumonic proc- 

 esses or without previous pneumonia, are otitis media, osteomyelitis, 

 and arthritis. Cases of pneumococcus peritonitis occur somethn3s 

 secondary to appendicular inflammations, occasionally without traceable 

 portal of entry. Severe catarrhal conjunctivitis may be caused by these 

 diplococci, usually during the course of a pneumonia. Ulcerative 

 endocarditis with pneumococcus septicemia, apparently independent of 

 a pulmonary lesion, is not infrequent. 



Toxic Products of the Pneumococcus. Our knowledge of pneumococ- 

 cus poisons is still very imperfect. Attempts to obtain soluble toxins by 

 the filtration of cultures have been, practically unsuccessful. (I. and F. 

 Klemperer, 1 Mennes, 2 Pane, 3 Foa and Carbone, 4 and others failed to 

 obtain pneumococcus nitrates of any degree of toxicity, though working 

 with highly virulent strains. The feeble toxin so obtained produced no 

 antitoxin. 



The general failure to procure strong soluble poisons from cultures, 

 gives weight to the assumption that the most potent toxic products of 

 pneumococsi are in the nature of endotoxins and closely bound to the 

 cell-bodies themselves. This assumption is borne out by the more 

 recent experiments of Macfadyen. 5 This author obtained acutely 

 poisonous substances from pneumococci by trituration of the organisms 

 after freezing, and extracting them with a one 1 : 1,000 caustic potash 

 solution. With the nitrates of these extracts he was able to cause rapid 

 death in rabbits and guinea-pigs by the use of doses not exceeding 0.5 

 to 1 c.c. He found, furthermore, a striking parallelism between the 

 degree of toxicity and the virulence of the extracted culture. Cole, 6 

 too, in recent studies, inclines to the belief that the poisons of the pneu- 

 mococcus are in the nature of endotoxins and has produced toxic sub- 

 stances by salt solution and bile extraction of the organisms. 



Immunization. Recovery from a spontaneous pneumococcus in- 



1 G. and F. Klemperer, Berl. klin. Woch., xxxiv and xxxv, 1891. 



* Mennes, Zeit. f. Hyg., xxv, 1897. 3 Pane, Rif. med., xx\ 1898. 

 4 Foa und Carbone, Cent. f. Bakt., x, 1899. 



* Macfadyen, Brit. Med. Jour., ii, 1906. 



6 Cole, Harvey Lecture, N. Y., Dec., 1913. 



