MICROBES IN THE RESPIRATORY PASSAGES 269 



of bacteria from the nasal mucus, amongst which also the 

 Spirochaete dentium is often to be met with. 



In tubercular diseases of the cavity of the nose the 

 pathognomonic tubercle bacilli are found in the nasal 

 mucus, in glanders ulcers the Bacillus mallei, and thrush 

 fungus and moulds frequently occur in the secretion. [See 



p. 195.] 



The Respiratory Passages 



Micro-organisms of the respiratory passages. Micro- 

 organisms may also be very easily conveyed from the 

 air into the bronchi by respiration. Straus and Dubreuil 

 have ascertained that the expired air is almost free 

 from organisms, and even when germs do occur the 

 proportion of those in expired to those in inspired 

 air is very small (1 : 600). Tubercle bacilli produce 

 infection with greater ease, as Cadeac and Molet found, 

 when the particles of dust to which they adhere are damp 

 with aqueous vapour, than when they reach the lungs in a 

 dry state. Owing to the discovery in recent years of a 

 series of micro-organisms which excite morbid processes in 

 the lungs, it is of very great importance to acquire a more 

 intimate knowledge of the microbes occurring there, and 

 this is most conveniently done by a thorough examination 

 of the sputum. Certainly there are found in the sputum 

 admixtures of matter from the naso-pharynx and the buccal 

 and nasal cavities ; still, it is possible to exclude all the 

 elements coming from other cavities, and to retain only 

 those derived from the lungs. 



Pansini constantly found different varieties of strepto- 

 cocci in the sputum both of healthy and diseased individuals, 

 and next to these in frequency, various kinds of sarcina. 

 A yellow, reddish, or green colour in sputum is caused 

 by chromogenic bacteria. Pansini derives the yellow and 

 reddish colour from the vital activity of Bacillus aureus, 



