THE PNEUMOCOCCUS 287 



Hemotoxin. Recently Cole 1 has shown that solutions obtained by 

 dissolving pneumococci in dilute solutions of bile salts, or by tritura- 

 tion, are hemolytic for rabbits, guinea-pigs, sheep and human red blood 

 cells, and that their activity is inhibited by minute amounts of choles- 

 terin. The injection of these solutions in gradually increasing amount 

 leads to an inhibition of their action; in other words, this "hemolytic 

 endotoxin" appears to act as an antigen. 



Pathogenesis. Human. At least 90 per cent, of all cases of lobar 

 pneumonia, one of the most prevalent and fatal of human diseases, 

 is caused by the pneumococcus, but this disease is by no means the 

 only one in which the organism is an etiological factor. Many 

 bronchopneumonias which follow acute infections, as typhoid, diph- 

 theria, so-called " aspiration pneumonia," are also of pneumococcic 

 causation. Pleurisy, a frequent complication of both types of pneu- 

 monia, is quite commonly a pneumococcus infection, and a majority 

 of sporadic cases of meningitis, particularly in children, are also caused 

 by the organism. Indeed, in children the pneumococcus is rather 

 more commonly isolated from suppurative processes than any other 

 organism; in adults the incidence of pneumococci in suppurations is 

 on the whole considerably less. Middle ear involvement, inflamed 

 mastoids, endo- and pericarditis are all frequently caused by the 

 pneumococcus. The channel of infection appears to be through the 

 blood stream, and pneumococci have been isolated from the blood 

 stream in a very large percentage of all cases of lobar pneumonia. 2 

 Less commonly the organisms become localized in joints, causing 

 arthritis, and around the shafts of bones, causing osteomyelitis. 

 Conjunctival inflammation of varying degrees of severity which 

 occasionally leads to ulcer formation is frequently a pneumococcus 

 infection. 



It was formerly stated that virulent pneumococci could be obtained 

 from the sputum of fully 30 per cent, of normal individuals. The 

 supposition was that the patient became the victim of his own 

 organisms. Recent studies by Dochez and Avery 3 suggest strongly 

 that the pneumococci found in the sputum during pneumonia are 

 commonly replaced by pneumococci of a less virulent type soon after 

 convalescence. Their observations, furthermore, make it justifiable 

 to consider those patients who harbor the more virulent types after 



1 Jour. Exp. Med., 1914, xx, 346. 



2 Rosenow, loc. cit. 



3 Quoted by Cole, New York Med. Jour., January 2 and 9, 1915. 



