ANTERIOR ASPECT OF HEAD AND NECK. 



downward; its inner wall presents a triangular plate of car- 

 tilage which is attached at the apex to the pars ossea, while 

 the base projects into the naso-pharynx. The upper edge of 

 the plate bends outward over the tube, which is completed 

 externally and below by a fibrous layer (lamina membranacea) 

 attached to the edges of the plate. The plate is attached to the 

 skull in the groove between the petrous bone and great wing 

 of the sphenoid. [753] 



Tympanic Ossicles. These form an articulated column be- 

 tween the outer and inner walls of the tympanum. Malleus : 

 The head is elliptical, and convex above and in front; it pre- 

 sents posteriorly a facet, for the incus, which is divided by a 

 ridge into upper and lower parts. Below the prominent lower 

 edge (spur) of the facet, posteriorly, is an oblique crest (crista). 

 The neck, just below the head, is flattened antero-posteriorly, 

 and constricted. The handle runs downward, backward, and 

 inward from the neck and is attached throughout to the mem- 

 brana tympani. It is flattened antero-posteriorly above, but 

 twisted below so that the surfaces look outward and inward. 

 Near its upper end, internally, is a projection for the Tensor 

 tympani tendon; the lower end is curved with the concavity 

 in front. The short process is attached to the membrana tym- 

 pani, and runs outward from the upper end of the handle. 

 The long process runs forward from the neck toward the 

 Glaserian fissure. [754] 



Incus. This resembles a bicuspid tooth. The body has a 

 saddle-shaped facet, directed forward, for the head of the mal- 

 leus. The short process is thick and triangular; it projects 

 horizontally backward, its conical tip articulating with the 

 fossa incudis. The long process projects straight downward, 

 behind and internal to the handle of the malleus. Its lower 

 end bends inward and presents a short neck with a small knob 

 (processus lenticularis) at the tip internally, for articulation 

 with the head of the stapes. [756] 



Stapes. The head has a concave facet externally for the 



[99] 



