CHAPTER III 



CHANNELS OF INFECTION 



l^vISEASE germs gain access to the bodies of sus- 

 ^ ceptible individuals, giving rise to infectious 

 diseases, through various channels. The most im- 

 portant of these are doubtless the alimentary and 

 respiratory tracts, to which access is obtained through 

 the mouth and nasal passages. It is sometimes diffi- 

 cult to ascertain whether infection has occurred as a 

 result of the deposition of germs contained in inspired 

 air upon the mucous membrane of the respiratory 

 passages or by reason of their having been taken into 

 the stomach with food or drink. 



Germs suspended in the air would be to a consid- 

 erable extent deposited upon the moist mucous mem- 

 brane of the mouth and nasal passages, and would be 

 carried thence to the stomach rather than to the 

 lungs. However, in certain diseases, infection no doubt 

 results from the deposition of germs in the bronchial 

 tubes. This is true of pulmonary consumption, of 



u 



