404 Dr. F. Semori. On the Position of the 



and constricting muscles ; Vierordt* and MacKendrickf as being 

 widely open ; and BruckeJ as being kept open during inspiration. 



Three widely different conditions therefore are described as repre- 

 senting the actual laryngeal phenomena observed during quiet 

 respiration in man, viz. : 



(a.) Rhythmical opening and narrowing of the glottis. 



(&.) A condition of rest, the glottis being widely open. 



(0.) A condition of rest, more or less corresponding to that seen 

 after death. 



The first of these descriptions, which dates back to prelaryngoscopic 

 times, is probably the most universally accepted one. It is generally 

 believed that even during quiet respiration, with each inspiration a- 

 very perceptible widening, with each expiration a correspondingly 

 perceptible narrowing, of the glottis takes place. 



The actual facts, however, little agree with this opinion. From 

 the metric measurements of the glottis, to be described in full further 

 on in this paper, it will be seen that only in a small percentage of 

 cases (less than 20 per cent.) the vocal cords of healthy, quietly 

 breathing adults make rhythmical excursions extending over 4 mm. 

 or more, and that in over 80 per cent, the glottis either remains 

 almost immovably open during both inspiration and expiration, or 

 that the excursions of the vocal cords are hardly appreciable. 



The truth of this statement can so easily be verified by laryngo- 

 scopic examination that it is not easy to understand how a different 

 belief could so long have held its ground, though a good many ex- 

 planations of this paradox may be advanced. Thus it may be that 

 some physiologists have simply transferred observations made on 

 animals (in which the rhythmic movements of the cords, as a rule, 

 are much more energetic than in man) to human beings, or that they 

 have drawn their conclusions from an insufficient number of observa- 

 tions on man, or that nervous persons, unaccustomed to laryngoscopic 

 examination, were experimented upon, or that, by the application of 

 the laryngoscope, reflex movements were produced, or finally, that 

 the serious mistake was committed of ordering the persons upon 

 whom the observations were made to " breathe quietly." Under any 

 of the last-named conditions, but especially under the last one, the 

 general type of respiration, in accordance with universally admitted 

 experiences, is apt to change at once in the direction of either 

 deepening or acceleration, and it is under these circumstances that 

 appreciable rhythmic excursions of the vocal cords are seen. 



But if a number of healthy, not nervous, adults, accustomed to the 

 application of the laryngoscope, are examined by a skilful observer 



* ' G-rundriss der Physiologie des Menschen,' 1877, p. 528. See also p. 224. 

 t ' Text-book of Physiology,' 1889, vol. 2, p. 311. 

 ' Yorlesungen iiber Physiologic,' 1881, p. 450. 



