TYPES OF PNEUMONIA 197 



be of a serous, haemorrhagic, or purulent character. Cases 

 of mixed fibrinous and catarrhal pneumonia also occur, and 

 in the catarrhal there may be great leucocytic emigration. 

 Hsemorrhages also may occur here. 



Besides the two chief types of pneumonia there is another 

 group of cases which are somewhat loosely denominated septic 

 pneumonias, and which may arise in two ways : (1) by the 

 entrance into the trachea and bronchi of discharges, blood, etc., 

 which form a nidus for the growth of septic organisms ; these 

 often set up a purulent capillary bronchitis and lead to infection 

 of the air cells and also of the interstitial tissue of the lung ; (2) 

 from secondary pyogenic infection by means of the blood stream 

 from suppurative foci in other parts of the body. (See chapter 

 on Suppuration, etc.) In these septic pneumonias various 

 changes, resembling those found in the other types, are often 

 seen round the septic foci. 



In pneumonias, therefore, there may be present a great variety 

 of types of inflammatory reaction. We shall see that with all of 

 them bacteria have been found associated. Special importance 

 is attached to acute croupous pneumonia on account of its course 

 and characters, but reference will also be made to the other 

 forms. 



Historical. Acute lobar pneumonia for long was supposed to be an 

 effect of exposure to cold ; but many observers were dissatisfied with 

 this view of its etiology. Not only did cases occur where no such 

 exposure could be traced, but it had been observed that the disease 

 sometimes occurred epidemically, and was occasionally contracted by 

 hospital patients lying in beds adjacent to those occupied by pneumonia 

 cases. Further, the sudden onset and definite course of the disease con- 

 formed to the type of an acute infective fever ; it was thus suspected by 

 some to be due to a specific infection. This view of its etiology was 

 promulgated in 1882-83 by Friedlander, whose results were briefly as 

 follows. In pneumonic lungs there were cocci, adherent usually in 

 pairs, and possessed of a definitely contoured capsule. These cocci 

 could be isolated and grown on gelatin, and on inoculation in mice they 

 produced a kind of septicaemia with inflammation of the serous membranes. 

 The blood and the exudation in serous cavities contained numerous 

 capsulated diplococci. There is little doubt that many of the organisms 

 seen by Friedlander were really Fraenkel's pneumococcus, to be presently 

 described. 



By many observers it had been found that the sputum of healthy 

 men, when injected into animals, sometimes caused death, with the 

 same symptoms as in the case of the injection of Friedlander's coccus ; 

 and in the blood and serous exudations of such animals capsulated 

 diplococci were found. A. Fraenkel found that the sputum of pneumonic 

 patients was much more fatal and more constant in its effects than that 

 of healthy individuals. The cocci which were found in animals dead of 

 this "sputum septicsemia," as it was called, differed from Friedlander's 

 cocci in several respects, to be presently studied. Fraenkel further 



