Bacterial Invasion of Respiratory Tract. 195 



between the hydrogen ion concentration of the feces and the 

 bacterial flora. That is to say, the hydrogen ion concentration 

 limits remained essentially the same during the preliminary and 

 the transforming periods of the different experiments. 



103 (1563) 



An unrecognized pathway for bacterial invasion of the respiratory 



tract. 



By M. C. Winternitz, G. H. Smith and E. S. Robinson (by 



invitation). 



[From the Brady Laboratory of Pathology and Bacteriology, Yale 

 University School of Medicine, New Haven, Conn.] 



Normally, the ciliated, mucus-secreting epithelium is a mech- 

 anism competent to protect the lungs against infection by way of 

 the upper respiratory tract. When this epithelium is injured by 

 toxic gas or when the mechanism is otherwise incapacitated, 

 as for example, in aspiration pneumonia, the lumen of the trachea 

 undoubtedly is the pathway traveled by the agent responsible for 

 the pulmonary inflammation. Pneumonia may occur, however, 

 and this is especially true of the lobar type, without demonstrable 

 gross lesion of the upper respiratory tract, and in these circum- 

 stances some route other than the above must have been provided. 



Experimentally, the introduction of pneumococci by intra- 

 tracheal instillation or by needle puncture of the tracheal wall 

 through the neck, may result in pneumonia. With either of these 

 methods of inoculation, local damage to the mucosa of the trachea 

 occurs. When the needle method is employed, an opportunity 

 is at hand, not only for infection of the submucosa, but of the 

 peritracheal tissue as well. When the organisms are introduced 

 by insufflation into the rabbit, damage to the mucosa of the 

 larynx or upper trachea can hardly be avoided. In either case, 

 an atrium of invasion for the submucosa of the trachea is provided, 

 and histologically infection of the submucosa is evident at the 

 point of inoculation. From here it may be traced throughout the 

 submucosa of the trachea and larger bronchi to the hilum of the 



