1884.] Origin of the Respiratory /Sounds. 415 



Changes in the physical condition of the lungs alter the sounds 

 either in intensity or in character, or in both, or the sounds may be 

 altogether absent from parts where they are normally heard. Over 

 parts of the lung which have become consolidated, or destroyed and 

 replaced by air, and in certain other conditions, the normal sound 

 of vesicular breathing is replaced by an inspiratory and expiratory 

 sound, having more the character of the sounds heard over the 

 trachea. These altered sounds differ in character according to the 

 physical changes in the lungs, but they have the common feature 

 distinguishing them from the sounds of vesicular breathing, that the 

 expiratory sound instead of being much weaker is equal to or more 

 intense than the inspiratory sound. 



Sounds having this peculiarity are classed together as " bronchial " 

 .sounds ; they resemble more or less the sounds normally heard over 

 the trachea. 



Many different qualities of bronchial breathingmay.be heard and 

 have received different names, but for the present purpose, it will 

 be sufficient to remember their common feature, namely, that the 

 expiratory sound is as loud or louder than the inspiratory. 



When the lungs are partially consolidated or otherwise changed, an 

 alteration of the vesicular sound is often noticed over the unaffected 

 parts of the lungs. The alteration consists in an increase in the 

 intensity of both the inspiratory and expiratory sounds. 



When the vesicular sound is thus intensified it is said to be 

 " puerile " in character, the vesicular breathing of a child being louder 

 than that of an adult. 



Besides the above alterations in the breathing sounds, certain 

 accessory sounds, such as those due to fluid in the air passages, and 

 to friction of the pleural surfaces, &c., may be present. 



The sound of the voice heard over physically altered lung differs 

 both in intensity and in character from the sound heard over unaltered 

 lung, and so far as this change does not correspond to any alteration 

 in the voice sounds produced in the larynx and mouth, it must be due 

 to changes in the conducting power of the parts through which the 

 sounds are heard. 



With regard to the changes in the breathing sounds the case is not 

 so simple, for, as we do not know where the normal sounds originate, 

 it is impossible to say how much the changes due to altered conduction 

 may be supplemented by changes in the sounds produced. 



In the rest of this paper the terms vesicular, bronchial, and puerile 

 breathing will be used, in the sense just indicated, in order to save the 

 constant repetition of descriptions of the sounds. 



When the left lung is placed, as described above, in the artificial 

 thorax, the right lung lies upon the top of the chamber collapsed, 

 and is unaffected by the respiration going on in the left. 



