2<26 THE ACUTE PNEUMONIAS 



acter. Cases of mixed fibrinous and catarrhal pneumonia also 

 occur, and in the catarrhal there may be great leucocytic emigra- 

 tion. Hemorrhages may also be observed. 



Besides the two chief types of pneumonia there, is another 

 group of cases which are somewhat loosely denominated septic 

 pueumonias, 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 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, 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 septicsemic condition with the presence of cap- 

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

 "sputum septicemia" could not at that period be properly realised, 

 as it was not recognised that an organism could produce different 

 results in different animals, and therefore it was thought 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. The 

 work of "Weichselbaum in 1886 elucidated the subject further. This 

 observer, investigating 129 cases of various types of pneumonia, isolated, 

 first and most frequently, an organism he denominated the diplococcus 

 pneumonice (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. 



Under certain circumstances other organisms, notably the b. pestis, 

 have been found to originate pneumonic processes. 



