334 Pneumonia 



Auld* found that if a thin layer of prepared chalk were 

 placed upon the bottom of the culture-glass, it neutralized 

 the lactic acid produced by the pneumococcus, and enabled 

 it to grow better and produce much stronger toxin. 



Pathogenesis. If a small quantity of a pure culture 

 of the virulent organism be introduced into a mouse, 

 rabbit, or guinea-pig, the animal dies in one or two days. 

 Exactly the same result can be obtained by the introduction 

 of a piece of the lung-tissue from croupous pneumonia, 

 by the introduction of some of the rusty sputum, and 

 frequently by the introduction of human saliva. Post- 

 mortem examination of infected animals shows an inflamma- 

 tory change at the point of subcutaneous inoculation, with 

 a fibrinous exudate similar to that succeeding subcutaneous 

 inoculation with the diphtheria bacillus. At times, and 

 especially in dogs, a little pus may be found. The spleen is 

 enlarged, firm, and red-brown. The blood with which the 

 cavities of the heart are filled is firmly coagulated and, like 

 that in other organs of the body, contains large numbers 

 of the bacteria, most of which exhibit a lanceolate form and 

 have distinct capsules. The disease is thus shown to be a 

 bacteremia unassociated with conspicuous tissue-changes. 



In such cases the lungs show no consolidation. Even if 

 the inoculation be made by a hypodermic needle plunged 

 through the breast-wall into the pulmonary tissue, pneu- 

 monia rarely results. Monti claims to have found that a 

 characteristic croupous pneumonia results from the injec- 

 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 



* "Brit. Med. Jour.," Jan. 20, 1900. 



