AVENUES OF EXIT OF INFECTIOUS AGENTS. 155 



ear disease) complicates diphtheria, or follows as a 

 sequela, the discharge from the ear is quite likely to 

 contain diphtheria bacilli; and in the same way the 

 purulent pleurisy (empyema) which often complicates 

 pneumonia, is usually an extension to the pleura of the 

 same micro-organism which caused the pneumonia. 

 Failure to give due regard to such considerations may 

 lead in certain of the infectious diseases to serious con- 

 sequences. Cases in point are otitis media following 

 diphtheria and scarlet fever, the discharges from the 

 throat and ear in either case remaining infectious for 

 weeks after recovery. The virus of scarlet fever is 

 especially tenacious in that way, and the records of the 

 disease are full of instances in which it has been con- 

 veyed by children with discharging ears after release 

 from quarantine. 



The sputum is a prolific source of infection, 



ExPECTOR- • 



since always in the expectoration, to a 



ATION. -^ . ^ 



lesser extent m the nasal secretions, are 

 discharged the microbes that give rise to inflammatory 

 conditions of the air-passages : the lungs, the bronchi and 

 trachia, the pharynx, the buccal and nasal cavities. 

 The inflammations in question may be primary in the 

 part affected, or secondary to an inflammatory process 

 elsewhere; or they may be part of a general disease. 

 An example of these various conditions is found in 

 pneumonia. Pneumonia may occur as an independent 

 infection; it may be secondary to an inflammatory 



