OCCURRENCE OF CAUSATIV 



It is possible, to a certain degree, to differentiate the 

 pneumonias according to their causative agents : 



i. Pneumococcus-pneumonia corresponds with the charac- 

 teristic clinical picture of true croupous pneumonia, with 

 fibrinous exudation into the alveoli, and lobar distribution 

 of the morbid process. Clinically, this variety is character- 

 ized by blood-streaked sputum, and especially by the 

 sudden onset of the disease with a chill, the high, stormy 

 course, and the critical decline of the fever. That this 

 special type of disease is related etiologically to the activity 

 of pneumococci is proved almost with certainty by the 



Fig. 47. Bacillus pneumoniae of Friedlander, from the expectoration in a case of 

 pneumonia ; X 1000 (Frankel and Pfeiffer). 



following facts : In the first place, in typical cases the 

 diplococcus alone is always found in the diseased area, in 

 which it is demonstrable during life by puncture. In the 

 next place, the general symptoms characteristic of pneu- 

 monia are also often present in marked degree, in con- 

 junction with other localizations of the diplococcus, espe- 

 cially pneumococcus-angina. Finally, it may be pointed out 

 in this place that the blood of human beings that have 

 passed through an attack of typical pneumonia with 

 critical defervescence is capable of immunizing animals to 

 pneumococci. There is thus furnished evidence that con- 

 valescents from pneumonia are often immune to pneumo- 



