410 A MANUAL OF BACTERIOLOGY 



The S. pneumonia is the cause of acute croupous pneu- 

 monia in man, and occurs in large numbers in the rusty 

 sputum and hepatised lung, and in 20 per cent, of the 

 cases can be isolated from the blood if 5-10 c.c. be cultured. 

 The production of a typical pneumonic process experi- 

 mentally and the presence of the diplococcus in a large 

 proportion of cases of acute croupous pneumonia point 

 to its specific relationship to the disease. With regard 

 to the latter observation, Weichselbaum obtained it in 

 94 cases out of 129 examined, Wolf in 66 out of 70 cases, 

 and Netter in 75 per cent, of the cases examined. In 

 America the disease has of late been much on the increase, 

 in Chicago the mortality having reached as high as 20 

 per 10,000 inhabitants. Acute croupous pneumonia some- 

 times occurs in epidemic form and has decimated the 

 native labourers in the Rand mines. 



The organism is frequently present in the saliva of 

 healthy individuals, as shown by Netter, Sternberg, and 

 others, and the generally accepted idea of the relationship 

 of " catching cold " to an attack of the disease is explicable 

 on the theory that the action of cold lowers vitality, and 

 renders the tissues vulnerable to the attacks of the organism 

 already in close proximity to them. 



Besides acute croupous pneumonia, more than half 

 the cases of broncho-pneumonia, both primary and 

 secondary in the course of other diseases, are due to the 

 S. pneumonia, which is also associated with a number of 

 other important pathological conditions in man. It is a 

 pyogenic organism, producing abscesses when inoculated 

 into a relatively insusceptible animal such as a dog, and 

 has been met with in abscesses, empyema, suppuration 

 in the antrum, and purulent arthritis. It is also found 

 in about half the cases of purulent meningitis, sometimes 

 in cerebro-spinal meningitis, in about a third of the cases 

 of otitis media and infective endocarditis, sometimes in 



