126 



APPLIED ANATOMY. 



of laryngotomy. This operation is but seldom performed. The space is too small 

 in many cases, the opening is not made sufficiently low and it is too close to the 

 vocal cords. It is an operation of emergency. It is much easier to make a 

 quick opening at this point than it is in the trachea below, as it is more superficial 

 and is held steady in place by the cartilage above and below it. Even in adults the 

 space is sometimes too small to introduce a tube without force and the operation 

 should never be done below the age of thirteen. On account of the membrane being 

 nearer the surface than is the trachea, a shorter tube should be used. Before intro- 

 ducing the tube, care must be taken that the mucous membrane has been thoroughly 

 divided, as otherwise the tube will push it before it and slip between the mucous 

 membrane and the cartilage and, therefore, not enter the cavity of the larnyx. 



Cricoid Cartilage. This is much larger posteriorly than anteriorly and rills 

 the space between the posterior edges of the thyroid cartilage. Its outside diameter 

 is larger than that of the trachea, hence it can readily be felt and forms one of the 

 most important landmarks on the front of the neck. It is about opposite the sixth 



FIG. 159. Examining the interior of the larynx by means of the laryngoscopic mirror. 



cervical vertebra. It is thick and strong and forms a complete circle, being unlike 

 the tracheal rings in this respect. It is rare that it is divided in operations. 



For the parts concerned in tracheotomy see the section on the neck. 



Laryngoscopy. The interior of the larynx is examined by means of a small 

 mirror, i to 3 cm. in diameter, introduced through the mouth and placed just below 

 the uvula at an angle of a little more than 45 degrees. The opening of the larynx is 

 not directly beneath the mirror but slightly anterior. The base of the tongue and 

 lingual tonsils, the glosso-epiglottic folds and pouches, and the epiglottis can be seen 

 in front. Posteriorly one sees the two arytenoid cartilages capped with the cartilages 

 of Santorini. Between the arytenoids is the commissure or interarytenoid space. 

 To the front and outer side of the tip of the arytenoid cartilages is the cartilage of 

 Wrisberg, and running from it forward are the aryepiglottic folds. To the outer 

 side of the aryepiglottic fold is the depression called the sinus pyriformis. It is here 

 that congenital cervical fistulae sometimes open. Near the middle are seen the two, 

 white, true vocal cords, and to the outer edge of these are seen the false vocal 

 cords. Between these two is the opening of the ventricle of the larynx. The rings 

 of the trachea can readily be seen and not infrequently even the point of bifurcation 

 of the trachea opposite about the second rib. 



