1890.] Vocal Cord* in Quiet Respiration in Man, SfC. 157 



rhythmical movements synchronous with inspiration and expiration, 

 and that in more than 80 per cent, the glottis in both sexes forms 

 during quiet respiration an isosceles triangle, 2 3 times as large on 

 the average as that representing the cadaveric glottis. Under all 

 circumstances the minimum size observed during life is larger than 

 the maximum seen after death. 



Additionally corroborative literary and experimental evidence 

 (from experiments on animals) is adduced, showing that the glottis in 

 man during quiet respiration is considerably wider open than after 

 death. 



The position of the vocal cords during quiet respiration, therefore, 

 represents neither a state of inaction of their antagonistic adductor 

 and abductor muscles nor a condition of equilibrium between them. 

 It must necessarily be the result of actual muscular contraction, and 

 must represent either simultaneous activity of both the adductors 

 and abductors, with preponderance of the latter ; or, secondly, some 

 degree of activity on the part of the latter alone, the adductors 

 being not at all in a state of functional activity. 



Prior to discussing the question which of these two possibilities 

 corresponds to the actual facts, the author investigates the cause of 

 the difference found to exist between the conditions observed during 

 life and after death. He draws attention to the fact that the larynx 

 serves two functions, in a certain sense antagonistic to each other, 

 viz., those of respiration and phonation. For the purposes of tbe 

 former it is indispensable that the lumen of the air-tubes should be 

 wide enough to admit of the ingress and egress of the quantity of air 

 necessary for breathing purposes ; for those of the latter, that an appa- 

 ratus should be interpolated within the air-tubes which would admit 

 of a complete juxtaposition of the voice-producing organs. 



It is then shown by another series of comparative measurements 

 that by the interpolation of the vocal apparatus (which for reasons 

 derived from comparative anatomy must be considered to be a highly 

 specialised addition to the respiratory system) within the air-passages 

 their narrowest part is further reduced, when the vocal cords are at 

 perfect rest ("cadaveric position"), to less than one-third of its 

 natural area; and, again, by a review of experimental and pathological 

 facts, that a reduction of the glottis to this cadaveric size involves, 

 upon the commencement of any effort, however small, some alteration 

 in the type of respiration. 



From these facts the conclusion is drawn that the interpolation of 

 the phonatory within the respiratory apparatus had to be counter- 

 balanced by some arrangement which supplied the minimum of space 

 compatible with the ingress and egress of that amount of air into the 

 lower air-passages which is required for the purposes of what we call 

 normal quiet respiration. 



