196 



MAMMALIAN ANATOMY 



overlapped by the posterior portion of the outer border of the 

 alisphenoid. This area faces downward and backward, and is covered 

 by the inner part of the upper anterior end of the ectotympanic, 

 which does not touch it, however, in all places, thus forming the 

 Glaserian 1 fissure. A distinct groove in its outer part is converted 

 into the canal of Huguier. 2 The rest of the lower surface within 

 the auditory meatus might be almost called a portion of the inner 

 surface of the squamous (Fig. 132), inasmuch as it faces almost 



FIG. 132. 



Fossa for Malleus and Incus. 



Mastoid. 



Bridge, with Groove leading down 

 to Stylo-mastoid Foramen. 



Foramen for Chorda Tympani. 

 Pit for Tympano-hyal. 



Bullar Septum . 



Groove for Vessels. 



Entocranial Surface of Squa- 

 mous. 



Hook on Ectotympanic. 



External Auditory Meatus. 



Eustachian Groove. 



Spine, completes Basiphenoidal 



Notch. 

 Spine, with Basisphcnoid. 



LEFT TEMPORAL BONE. INNER SURFACE. PETROUS PORTION REMOVED. 



directly inward and only slightly downward. It is about twice as 

 long as high. It forms the upper part of the outer wall of the 

 tympanum, and is impressed by two fossae. The larger, upper, and 

 anterior fossa lodges the heads of the malleus and incus. It is 

 oval, the long axis running longitudinally. Its sharp, elevated, upper 

 border joins the anterior border of the petrous portion of the temporal, 

 and the rough space for the ectotympanic attachment limits it in front. 

 Below, it is bounded in part by the emarginate, rounded border of 

 the auditory meatus, and in part by a longitudinal convexity which 

 separates it from the second fossa. It faces directly inward. The 

 second fossa lies below and behind the first. It is smaller, almost 

 round, and contains the superior process of the incus. It faces down- 

 ward and inward. Its upper anterior limit is the convexity already 

 mentioned, due in reality to the difference between its plane and that 

 of the other fossa. The anterior and lower boundary is, in front, the 



Glaser (A.D. 1629-1675). 



2 Huguier (A.D. 1804-1874). 



