298 HEAD AND NECK 



Each palatine tonsil has a rich blood-supply. It derives 

 arterial twigs from the tonsillar and ascending palatine 

 branches of the external maxillary, the descending palatine 

 branch of the internal maxillary, the ascending pharyngeal, 

 and the dorsalis linguae of the corresponding side. 



The dissectors should note that the tonsil lies at about 

 the level of the angle of the mandible, and that the wall of 

 the pharynx separates it from the external maxillary artery. 

 The internal and external carotid arteries also lie lateral to 

 the region of the tonsil, but they are further away than the 

 external maxillary. 



Tuba Auditiva (O.T. Eustachian Tube). The auditory 

 tube is the canal which conveys air from the pharynx to the 

 tympanic cavity. It is about 25 mm. long and is divided 

 into two portions, according to the parts which enter into 

 the construction of its wall. In the lateral part of its course, 

 as it nears the tympanic cavity, its walls are bony, and it runs 

 in the interval between fhp fympanic and petrous portions 

 pQhe temporal bone. The medial part consists mainly of 

 cartilage! It is^placed on the base of the skull, and is 

 lodged in the gutter or groove between the petrous part of 

 the temporal bone and the great wing of the sphenoid. The 

 cartilaginous part of the tube comes under the notice of the 

 dissector at the present stage, and he should first note its 

 direction and then study its relations and the construction of 

 its wall. 



The dissector can readily ascertain the direction of the 

 canal by passing a probe into it through its pharyngeal orifice. 

 It runs backwards and laterally, with a slight inclination up- 

 wards, and passes first alcove and then to the lateral side of 

 the elevator muscle of the soft palate, and along the medial 

 side of the upper part of the tensor of the soft palate. It 

 lies, therefore, in a considerable part of its extent, between 

 the two muscles (Fig. 218). 



Before removing the mucous membrane from the 

 pharyngeal part of the tube, the dissector should note that at 

 the lower margin of the orifice there is a prominent rounded 

 eminence, the levator cushion, due to the subjacent elevator 

 muscle of the soft palate. The removal of the mucous 

 membrane will reveal the fact that the wall of the tube is 

 formed, in great part, by a triangular plate of cartilage, which 

 is folded upon itself so as to protect the tube on its upper and. 



