Pathogenesis 295 



tion of cultures into the trachea of susceptible animals. 

 This observation, however, lacks confirmation. 



Lesions. The lesions of croupous pneumonia of man are 

 almost too well known to need description. The distribution 

 of the disease conforms more or less perfectly to the divisions 

 of the lung into lobes, one or more lobes being affected. 

 An entire lung may be affected, though as a rule the apex 

 escapes consolidation and is simply congested. The in- 

 vaded portion of the lung is supposed to pass through a 

 succession of stages clinically described as (i) congestion, 

 (2) red hepatization, (3) gray hepatization, and (4) resolu- 

 tion. In the first stage bloody serum is poured out into the 

 air-cells, filling them with a viscid reddish exudate. In 

 the second stage this coagulates so that the tissue becomes 

 solid, airless, and approximately like liver-tissue in appear- 

 ance. The third stage is characterized by dissolution of 

 the erythrocytes and invasion of the diseased air-cells by 

 leukocytes, so that the color of the tissue changes from 

 red to gray. At the same time the coagulated exudate be- 

 gins to soften and leave the air-cells by the natural pas- 

 sages, and the stage of resolution begins. 



In more rare cases circumscribed areas of consolidation 

 occur in the lung-tissue. The inflammatory lesions of other 

 organs present nothing characteristic by which they can be 

 recognized by macroscopic examination. 



The pneumococcus is not infrequently discovered in dis- 

 eased conditions other than croupous pneumonia ; thus, Foa, 

 Bordoni-Uffreduzzi, and others found it in cerebro-spinal 

 meningitis; Frankel, in pleuritis; Weichselbaum, in perito- 

 nitis; Banti, in pericarditis; numerous observers in acute 

 abscesses; Gabbi isolated it from a case of suppurative 

 tonsillitis ; Axenfeld observed an epidemic of conjunctivitis 

 caused by it; Zaufal, Levy, and Schroder and Netter have 

 been able to demonstrate it in the pus of otitis media, and 

 Foulerton and Bonney* isolated it from a case of primary 

 infection of the puerperal uterus. It has also been found 

 in arthritis following pneumonia, and in primary arthritis 

 without previous pneumonia by Howard. f 



Interesting statistics concerning the relative frequency of 

 pneumococcus infections in adults given by Netter J are as 

 follows : 



*" Trans. Obstet. Soc. of Lond.," 1903, part n, p. 128. 

 t" Johns Hopkins Hospital Bulletin," Nov., 1903. 

 J " Compte-rendu," 1889. 



