126 DISSECTION OF THE PHARYNX. 



Dissection (fig. 29). Open the pharynx by an incision along its mid- 

 dle, and, after removing the tow from the interior, keep it open with 

 hooks: a better view of the cavity will be obtained by partly dividing the 

 occipital attachment on each side. The mucous membrane is to be care- 

 fully removed below the dilated extremity of the Eustachian tube on the 

 right side, for the purpose of finding some pale muscular fibres, salpingo- 

 pharyngeus C, which descend from it. 



The ELEVATORS of the pharynx are two in number on each side an 

 external (stylo-pharyngeus), and an internal (salpingo-pharyngeus). 



The stylo-pharyngeus (external elevator) may be read again with the 

 pharynx. Its description is given in p. 10(5. 



Salpingo-pharyngeus, c (internal elevator). This little band is fixed 

 by tendon to the lower border of the cartilage of the Eustachian tube near 

 the orifice. Its fleshy fibres end below by joining those of the palato- 

 pharyngeus Q. If the part is not tolerably fresh the muscle may not be 

 visible. 



Action. This thin muscle elevates the upper and lateral part of the 

 pharynx above the spot where the large external elevator enters the wall ; 

 but it is probably used chiefly in opening the Eustachian tube in swal- 

 lowing. 



The interior of the pharynx (fig. 29) is wider from side to side than 

 from before back, and its greatest width is opposite the hyoid bone ; from 

 that spot it diminishes both upwards and downwards, but much more 

 rapidly in the latter than in the former direction. Through the part of 

 the passage above the mouth the air moves in respiration; whilst through 

 that below the mouth both air and food are transmitted the air passing 

 to the aperture of the windpipe, and the food to the oesophagus. In it 

 the following objects are to be noticed : 



At the top are situate the posterior apertures, G, of the nasal cavity, 

 which are separated by the septum nasi; and below them hangs the soft 

 palate, partly closing the cavity of the mouth. By the side of each nasal 

 aperture is the trumpet-shaped end of the Eustachian tube, F. 



Below the soft palate, the opening into the mouth isthmus faucium, 

 H, is to be recognized; and on each side of this is the tonsil, K, which is 

 placed in a hollow between two prominences named pillars of the soft 

 palate the one, I, proceeding from the soft palate to the side of the 

 tongue, and the other, L, from the same part to the side of the pharynx. 



Next in order, below the mouth, comes the aperture of the larynx, N; 

 and close in front of it is the epiglottis, or the valve which assists to close 

 that opening during deglutition. Lowest of all is the opening, o, from 

 the pharynx into the oesophagus. 



The apertures into the pharynx are seven in number, and have the 

 following position and boundaries: 



The posterior openings of the nasal fossae, G, are oval in form, and 

 measure about an inch from above down, but only half an inch across. 

 Each is constructed in the dried skull by the sphenoid and palate bones 

 above, and by the palate below ; by the vomer inside, and the internal 

 pterygoid plate outside; and it is lined by mucous membrane. 



The Eustachian tube, F, is a canal, partly osseous, partly cartilaginous, 

 by which the tympanic cavity of the ear communicates with the exter- 

 nal air. 



If the mucous membrane be removed from the tube on the right side, 

 the cartilaginous part appears to be nearly an inch long. It is narrow 



