TYPES OF PNEUMONIA 233 



in the catarrhal there may be great leucocytic emigration. 

 Haemorrhages may also be observed. 



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. Farther, 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, who observed in the lungs 

 capsulated cocci, which he isolated and showed to possess pathogenic 

 properties. The situation was complicated by the subsequent observation 

 that the injection into animals of the sputum of healthy individuals 

 frequently originated a septicaemia condition with the presence of cap- 

 sulated cocci in the blood. The significance of the occurrence of this 

 "sputum septicaemia " could not at that period be properly realised. It 

 was not recognised that an organism could produce different results in 

 different animals, and therefore the tendency was to take up a position 

 that the organisms described by Friedlander were not specifically related 

 to pneumonia. Somewhat later, A. Fraenkel described diplococci in 

 pneumonia which differed culturally from those of Friedlander, and it 

 was not till the work of Weichselbaum in 1886 that the subject 

 became clearer. This observer, investigating 129 cases of various types 

 of pneumonia, isolated, first and most frequently, an organism he 

 denominated the diplococcus pneumonias (with a variant named by him 

 the streptococcus pneumonia), which corresponded to Fraenkel's organism ; 

 second, an organism he described as the bacillus pneumonice, occurring 

 less frequently and which corresponded with that originally noted by 

 Friedlander. In a few cases he found staphylococcus pyogenes aureus 

 present. 



