BACTERIA OF THE MOUTH. 345 



those intense inflammatory changes characteristic of croupous 

 pneumonia, or acute inflammation of the lungs, and in some 

 cases, where the organisms appear to be more virulent, septic 

 pneumonia and gangrene of the lung. It may be, however, 

 that this gangrenous pneumonia is the result of the invasion 

 and action of another organism. It has already been men- 

 tioned that the Streptococcus aureus and S. albus sometimes 

 occur in the mouth, but it would appear that these forms 

 are more frequently met with in the posterior nares and 

 in the cavities of the nose. To their action is supposed 

 to be due the suppuration or festering that almost invariably 

 follows small operations of the mucous membrane of the 

 nostrils, unless the mucous surface is previously prepared by 

 careful antiseptic washing out of the cavities and by frequent 

 application of antiseptics after the operation has been per- 

 formed. The micrococcus tetragonus is also found in the 

 mouth, whence, in cases of tuberculosis, it makes its way into 

 the lungs, and is there found, especially in suppurating cavi- 

 ties ; this organism, which is fatal to white mice and guinea- 

 pigs, usually occurs in little packets of four, each coccus 

 being about in in diameter. On gelatine, according to 

 Eisenberg, it grows as small white colonies, which when mag- 

 nified appear to have a peculiar ground glass appearance ; 

 it does not give rise to any liquefaction of the gelatine. 

 Various other septic forms have been isolated from sputum. 

 It will thus be seen that in certain cases injury of the 

 mouth, of the periosteum of the jaw, or the soft tissues of 

 the pharynx, may lead to infections of very different kinds, 

 but it may be laid down as a general rule that septic infec- 

 tion is frequently the result of invasion from these regions, 

 and very numerous are the cases recorded in which death has 

 resulted even from the most trifling operations in the mouth 

 and naso-pharynx. I have seen several cases where death 

 has ensued, with all the symptoms of most acute septicaemia, 

 or with symptoms of more chronic poisoning, as in pyaemia, 

 from the extraction of a tooth or the lancing of the gums in 

 patients with imperfectly cleansed mouths, or in persons who 

 have been engaged in attendance on patients suffering from 

 certain infectious diseases ; the organisms in such cases find- 

 ing their way from positions in which they were compara- 

 tively harmless, into the wounds that were unavoidably 

 made, whence they invaded the lymphatics or passed 



