490 MUCOUS MEMBRANE OF THE LARYNX. 



connexion with the chordae vocales, act upon the whole length of those 

 cords. 



The thyro-epiglottideus acts principally by compressing the glands of 

 the sacculus laryngis and the sac itself: by its attachment to the epiglottis 

 it would act feebly upon that valve. The aryteno-epiglottideus superior 

 serves to keep the mucous membrane of the sides of the opening of the 

 glottis tense, when the larynx is drawn upwards and the opening closed 

 by the epiglottis. Of the aryteno-epiglottideus, the "functions appear to 

 be," writes Mr. Hilton, " to compress the subjacent glands which open 

 into the pouch ; to diminish the capacity of that cavity, and change its 

 form; and to approximate the epiglottis and the arytenoid cartilage." 



Mucous Membrane. The aperture of the larynx is a triangular or cord- 

 iform opening, broad in front and narrow behind ; bounded anteriorly 

 by the epiglottis, posteriorly by the arytenoideus muscle, and on either 

 side by a fold of mucous membrane stretched betw r een the side of the epi- 

 glottis and the apex of the arytenoid cartilage. On the margin of this 

 aryteno-epiglottidean fold the cuneiform cartilage forms a prominence more 

 or less distinct. The cavity of the larynx is divided into two parts by an 

 oblong constriction produced by the prominence of the chordae vocales. 

 That portion of the cavity which lies above the constriction is broad and 

 triangular above, and narrow below ; that which is below it, is narrow 

 above and broad and cylindrical below, the circumference of the cylinder 

 corresponding with the ring of the cricoid ; while the space included by 

 the constriction is a narrow, triangular fissure, the glottis or rima glottidis. 

 The form of the glottis is that of an isosceles triangle, bounded on the 

 sides by the chordae vocales and inner surface of the arytenoid cartilages, 

 and behind by the arytenoideus muscle. Its length is greater in the male 

 than in the female, and in the former measures somewhat less than an inch. 

 Immediately above the prominence caused by the chorda vocalis, and ex- 

 tending nearly its entire length on each side of the cavity of the larynx, is 

 an elliptical fossa, the ventricle of the larynx. This fossa is bounded be- 

 low by the chorda vocalis, which it serves to isolate, and above by a border 

 of mucous membrane folded upon the lower edge of the superior thyro- 

 arytenoid ligament. The w r hole of the cavity of the larynx, with its pro- 

 minences and depressions, is lined by mucous membrane, which is con- 

 tinuous superiorly with that of the mouth and pharynx, and inferiorly is 

 prolonged through the trachea and bronchial tubes into the lungs. In the 

 ventricles of the larynx the mucous membrane forms a ca?cal pouch of va- 

 riable size, termed by Mr. Hilton the sacculus laryngis* The sacculus 



* This sac was described by Mr. Hilton before he was aware that it had already 

 been pointed out by the older anatomists. I myself made a dissection, which I still 

 possess, of the same sac in an enlarged state, during the month of August, 1S37, without 

 any knowledge either of Mr. Hilton's labours or Morgagni's account. The sae projected 

 considerably above the upper border of the thyroid cartilage, and the extremity had 

 been snipped off on one side in the removal of the muscles. The larynx was preM^iied 

 to me by Dr. George Moore of Camberwell ; he had obtained it from a child who died 

 of bronchial disease ; and he conceived that this peculiar disposition of the mucous 

 membrane might possibly explain some of the symptoms by which the case was ac- 

 companied. Cruveilhier made the same observation in equal ignorance of Morgagni'fl 

 description, for we read in a note at page 077, vol. "ii. of his Jlnatomie Descriptive. " J'ai 

 vu pour ia premiere fois cette arriere cavite chez un individu effects de phthisic laryngee. 

 MII elle 6iait tres-deve'oppee. Je fis des recherches sur le larynx d'autres individu^, et 

 ]e trouvai que cette disposition etait constaute. Je ne savais pas alors que Morgagui 



