1884.] Origin of the Respiratory Sounds. 411 



II. "Experiments to Determine the Origin of the Respiratory- 

 Sounds." By J. F. BULLAR, M.B. Cantab., F.R.C.S. Com- 

 municated by Dr. LAUDER BRUNTOX, F.R.S. Received 

 October 30, 1884. 



A detailed account of the various existing theories of the produc- 

 tion of the respiratory sounds may be found in Dr. Paul Niemeyer's 

 " Handbuch der Percussion und Auscultation" (Brlangen, 1870). 



The various theories, though differing in minor points, may be 

 arranged under three principal heads. 



A. According to the first the sounds are produced all along the 

 respiratory tract by the friction of the air against its walls. 



B. According to the second the sounds are produced at the glottis 

 alone, and the differences in the sounds heard over the trachea and 

 lungs are attributed to the greater or less conducting power of the 

 structures through which they are heard at each spot. 



C. According to the third theory the sounds are produced at those 

 parts of the respiratory tract where the air passes from a narrower to 

 a wider space. Thus during inspiration one sound is produced at the 

 glottis, and another at the points where the smallest bronchioles 

 open into the vesicles. During expiration a sound is produced at 

 the glottis only. 



The sounds are represented diagrammatically in the figure. 



FIG. 1. 



The arrows show the direction of the air-current by which a sound 

 is produced at each spot. 



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