546 VOICE AND SPEECH 



the vocal cords, and that the mechanism just described is the one 

 ordinarily made use of in raising the pitch of the sounds. The ap- 

 proximation of these cartilages may be felt by placing the finger in 

 the notch below the pomum Adami while sounds of different pitch 

 are produced. In the human larynx, the vocal cords are penetrated 

 by a few muscle fibers which take their origin upon the arytenoid 

 cartilages and eventually reach the anterior wall of the larynx. 

 Their contraction is said to render the vocal cords more tense and 

 hence, this muscle, which is known as the tensor vocalis, is com- 

 monly regarded as an aid to the cricothyroid. Grlitzner,^ on the 

 other hand, believes that its contraction renders these bands more 

 flabby and forms, therefore, a typical detentioner. NageP adheres 

 to the first view and states that these muscle fibers antagonize the 

 lateral displacement of the edges of the vocal cords, thereby retain- 

 ing them more fully in the path of the expiratory currents of air. 



The Approximation of the Vocal Cords. — As has been stated above, 

 the musculature of the larynx is arranged in a manner to form a sphinc- 

 ter for the upper end of the respiratory passage, the closure of which 

 is really effected at three different levels, namely, at the epiglottis, at 

 the false vocal cords and at the true vocal cords. The first two actions 

 having been discussed, we are now in a position to analyze the third, 

 namely, the adduction and abduction of the vocal cords. 



The arytenoid cartilages are two triangular platelets which are 

 placed transversely upon the tips of the cricoid processes. They 

 attain their greatest width posteriorly, while their tapering extremities 

 or vocal processes, are directed forward to serve as points of attach- 

 ment for the vocal cords. Furthermore, while their anterior processes 

 are freely movable in a transverse direction, their basal portions are 

 relatively fixed, because they form articulations with the vertical 

 plates of the cricoid cartilages. The latter, as has been shown by 

 Stieda and Will,^ are prolonged upward into two small cylindrical 

 projections, the convex surfaces of which are turned upward to fit 

 into corresponding concavities upon the under surfaces of the aryte- 

 noid cartilages. These joints are adjusted in such a way that the out- 

 ward movement or abduction of the vocal processes necessitates a slight 

 elevation of these cartilages, while their inward movement, or adduction, 

 permits them to reassume their former low level. By inference, it 

 may then be concluded that the adduction of the arytenoid processes 

 brings the vocal cords closer together, while their abduction separates 

 them more widely. Consequently, the glottis assumes a mere slit- 

 like outline during the former rnovement and a typical V-shaped 

 outline during the latter. It should also be observed that the approxi- 

 mation of the vocal cords is greatly facilitated by an inward movement 



1 Ergebn. der Physiol., i, 1902, 466. 



2 Handb. der Physiol., iv, 1909, 702. 



3 Dissertation, Konigsberg, 1895. 



