MECHANICAL PHENOMENA OF EXTERNAL RESPIRATION 231 



own body up again to a more erect position, but without moving 

 the hands.' Air is thus drawn into the lungs. The process is 

 repeated twelve to fifteen times a minute. 



Certain accessory phenomena (movements and sounds) are asso- 

 ciated with the proper movements of respiration. The larynx rises 

 in expiration, and sinks in inspiration. The glottis (and particu- 

 larly its posterior portion, the glottis respiratoria) is widened during 

 deep inspiration and narrowed during deep expiration. The same 

 is the case with the nostrils, and, indeed, iri some persons the alae 

 nasi move even in ordinary breathing. It has long been known 

 that in deep respiration changes in the calibre of the bronchi syn- 

 chronous with the respiratory movements may occur. In young 

 persons it may be directly observed with the bronchoscope, an 

 instrument used by laryngologists for exploring the larger bronchi, 



that these dilate 

 in inspiration 

 and constrict in 

 expiration (In- 

 galls). In part 

 at least these 

 movements are 

 passively pro- 

 duced by the 

 changes of intra- 

 thoracic pres- 

 sure, but it has 

 not been defi- 

 nitely deter- 

 mined whether 

 they are not in 

 part caused by 



alternate contraction and relaxation of the circular bronchial 

 muscles. To these muscles has sometimes been attributed the 

 function of regulating the flow of air into and out of the infundib- 

 ula, as the muscle of the arterioles regulates the distribution of the 

 blood in the organs. 



As regards the respiratory sounds, all that is necessary to be said 

 here is that when we listen over the greater portion of the lungs with 

 the ear, or, much better, with a stethoscope, a soft breezy murmur, 

 that has been compared to the rustling of the wind through distant 

 trees, is heard. This has been called the vesicular murmur. It is only 

 heard in health during inspiration and the very beginning of expira- 

 tion, and is louder in children than in adults. Around the larger 

 bronchi and the trachea a blowing sound is heard, which certainly 

 originates at the glottis, and is strengthened by the resonance of the 

 air-tubes. In health this is not recognized over the greater portion of 

 the lung. But in certain diseases in which the alveoli are devoid of 

 air, whether from compression or because they are filled up with 

 exudation, and in other conditions, this bronchial or tubular breathing 



Fig. no. Artificial Respiration in Cases of Drowning (after 

 Schafer). 



