Chapter XXIII 



DISEASES OF THE RESPIRATORY 

 TRACT 



COLDS AND INFLUENZA 



Colds, whether acute or chronic, are due to 

 bacterial infection. The bacteria commonly 

 found in the respiratory passages of healthy 

 persons are the pneumococcus, staphylococcus, 

 streptococcus, influenza bacillus, and members 

 of the micrococcus catarrhalis group. When 

 the mucous membrane is in a weakened condi- 

 tion owing to undue exposure of the body to 

 sudden changes in temperature the local vaso- 

 motor disturbances increase the secretions and 

 the bacteria grow more rapidly and may become 

 sufficiently virulent to attack the tissues. Ex- 

 posure and other predisposing causes are not 

 always required to produce an acute or chronic 

 cold, for sometimes the bacteria in the respira- 

 tory passages become sufficiently virulent to at- 

 tack a perfectly healthy person, and contagious 

 colds spread in the same way as an epidemic of 

 measles or scarlet fever. 



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