Vocal Cords in Quiet Respiration in Man, $c. 429 



that the abductors of the vocal cords are more easily disabled by any 

 organic mischief acting upon their nerve supply than the adductors, 

 and that they die sooner after the death of the individual than the 

 adductors,* can hardly be reconciled with the idea of a preponderance 

 of their physiological strength over that of the adductors. 



Fifthly, the central conditions of the innervation of the two laryn- 

 geal groups of muscles also tell, as I hope to show in a paper which 1 

 shall shortly bring before the Royal Society in conjunction with 

 Professor Victor Horsley, against the physiological preponderance of 

 the abductors over the adductors. 



Sixthly and lastly, the coup de grace is given to this idea by the 

 fact that stimulation of the cut end of the recurrent laryngeal in inosf 

 species of animals (except the cat) results if no undue influence of 

 the ancesthetic used during the experiment comes into playf in the 

 corresponding vocal cord being drawn towards the middle line, i.e., 

 the adductors preponderate over the abductors, though both groups of 

 fibres are equally strongly stimulated. This fact, needless t.o say, is 

 wholly incompatible with the idea of preponderance of the abductor 

 over the adductor muscles. 



Thus from whatever point of view the question of the simultaneous 

 innervation of the adductors and abductors, with preponderance of 

 the latter during quiet respiration, be looked upon, there is no evi- 

 dence for the existence of such a condition, and there are many 

 arguments against it. 



It is, indeed, much more probable that there is primarily a strict 

 differentiation between the two antagonistic groups of laryngeal 

 muscles (the phonatory and respiratory ones) and that, though 

 there is tinder certain circumstances a transition of the functions of 

 the one into those of the other, yet for the purposes of respiration 

 under ordinary circumstances the respiratory muscles, i.e., the poste- 

 rior crico-arytenoid muscles, alone are engaged, being during inspiration 

 and' during expiration in a state of semt-tonus, in order to counter- 

 balance the partial obstruction created by the interpolation of the 

 phonatory into the respiratory apparatus. 



This idea, indeed, more or less clearly expressed, has been before 

 the minds of a good many of those who since the beginning of this 

 century have worked in this field of investigation. It has been 

 shown above that Legallois was quite conscious of the necessity of 

 such a tonus existing. Lnschka, again (Zoc. cit.), and Schech (loc. cit.) 



(b.) " Ueber die Lahmung der einzelnen Fasergattungen dcs Ncrvus laryngeus 

 inferior (recurrens) " (' Berl. Klin. Wochenschrift,' 1883, No. 46, et seq.). 



* "On an apparently peripheral and differential Action of Ether upon the 

 Laryngeal Muscles." By Felii Semon and Victor Horsley (' British Medical 

 (Journal,' 4 and 11 Sept., 1886). 



f Compare the last-named paper by Semon and Horsley, p. 31. 



2 o 2 



