Vocal Cords in Quiet Respiration in Man, $c. 427 



one another. On the contrary, the tonic opening of the glottis may 

 and does at any moment under the influence of emotion, mechanical 

 effort, will, reflex irritation, &c., give way to a rhythmical widening 

 and narrowing of the glottis, and this again on return of normal 

 conditions gives way to the tonic state of widening above described. 

 There can, however, be no doubt that this tonic condition is, much 

 more than rhythmic movements, representative of the participation 

 of the larynx in quiet respiration of man. This has been amply 

 demonstrated by the mutual proportions described in a previous 

 paragraph. 



The question now arises : What does this tonic widening represent, 

 and how is it produced ? 



It has already been mentioned that it may represent as well a state 

 of tonic innervation of both the glottis openers and glottis closers, 

 with preponderance of the former, or, secondly, a tonic innervation 

 of the abductor muscles alone. 



The existence of the first-named condition has been very ingeniously 

 argued for by Rosenbach in the paper referred to above. He writes 

 as follows: "The more complete and delicate the innervating 

 mechanism and the active muscular apparatus are, the more exact 

 must, no doubt, be the co-operation of the muscular groups in 

 question. Now, the action of the vocal cords during respiration and 

 phonation requires an extraordinarily delicate mechanism, and the 

 position of the arytenoid cartilages depends in a high degree on the 

 co-operation oj: all muscles attached to them. Nay, disturbances 

 would have to be registered far more frequently than is now the case 

 if an extensive vicarious action of healthy muscles were not possible, 

 replacing those disabled from fulfilling their functions. It is, 

 therefore, probable that during the normal position of the vocal 

 cords nervous impulses are constantly carried down to both adductors 

 and abductors, but that the abductors, being the stronger muscles, 

 preponderate, just as in other muscular territories even during 

 quiescence the activity of the extensors preponderates. The stronger 

 the inspiratory innervation is, the more will the glottis become 

 opened, and the expiratory constriction, so trifling during quiet 

 respiration, is very likely to be considered mostly as a remission of 

 the innervation of the abductors, i.e., as a more passive occur- 

 rence." 



In spite, however, of this clever advocacy of a preponderance of 

 the abductors over the adductors, both being supposed to act 

 simultaneously, the theory seems to me not tenable from whatever 

 point of view it be examined. Anatomical, physiological, and patho- 

 logical facts equally militate against it. 



In the first place, it is not easy to understand how the abductors, 

 being in number and aggregate amount of muscular tissue inferior 



