RESPIRATION 127 



hear. It is hard to describe the nature of this sound, and its descrip- 

 tion is not necessary when the sound itself is so readily available. It is 

 produced by the friction of the air entering the alveoli plus the slight 

 crepitation of the alternately expanding and lessening bronchioles and 

 alveoli. < It may be heard at its best below the left clavicle. In most parts 

 of the lungs this sound is mixed, more or less in different places, with the 

 bronchial sound. 



Nasal sounds of various sorts are to be heard externally, their quality 

 and intensity depending on the configuration of the nares and the nasal 

 cavities. 



The various abnormal respiratory sounds are of extreme importance 

 to the clinician in the diagnosis of the diseases of the chest, throat, and 

 nose, and moreover, have much physiological interest because they serve 

 to illustrate and to emphasize the mechanical conditions both in the 

 structure and the function of the whole respiratory tract above the dia- 

 phragm. For the technical description and names of these numerous 

 abnormal sounds the student is referred to the special works on physi- 

 cal diagnosis. We here look briefly only at a few abnormal mechanical 

 conditions in the breathing apparatus from which the sounds arise. 

 When some of the alveoli and bronchioles are filled up by exudate, as in 

 pneumonia, the respiratory sounds may be absent altogether from that 

 part of the chest, save as they are conveyed from elsewhere. To com- 

 pensate for such diminution in the acting lung-tissue, the functioning 

 portions work more vigorously, and the more or less normal sounds are 

 increased beyond the normal intensity ("puerile breathing"). This 

 comes also from collapse or compression of a lung, as in empyema, 

 pneumothorax, or pleurisy with effusion. 



Sometimes, most often from tuberculosis, there is a cavity in the lung, 

 and this may be of any size, up to that of a whole lung. Such a cavity 

 gives rise to cavernous sounds or to amphoric breathing when of moder- 

 ate or large size, the breath echoing or resounding more or less as it 

 enters and passes by the openings into it. If the cavity be of small 

 size, the first third or so of inspiration may be harsh (as the air forces 

 a way into it). When the lung-tissue is solidified it serves as a much 

 better conductor of the bronchial sounds than when normal, and so 

 the latter may be heard in an abnormal intensity and in places where in 

 health they are faint; on the other hand, the vesicular murmur is quite 

 absent. When there is fluid in the bronchioles one may hear the crepi- 

 tating sound always made by air bubbling through a small quantity of 

 a liquid. This is the condition in the first stage of pneumonia. The 

 same condition in the larger bronchi causes mucous rales. When the 

 bronchioles are obstructed (as by mucus) in just the right degree, an 

 occasional inspiration only penetrates them and there is what is called 

 cog-wheel breathing in that region of the chest. If the bronchioles 

 are mostly filled with tough mucus, the air has to tear its way through, 

 causing the harsh, rough sounds technically known as rhonchi. When 

 this condition is extreme the whole adjacent chest- wall may be set into 



