LATEKAL ASPECT OF THE SKULL. 167 



palatine fossa; behind that, by a rough ridge, the infra -temporal crest, which 

 crosses the lateral surface of the great wing of the sphenoid, to become continuous 

 posteriorly with a ridge on the lower surface of the squamous part of the temporal 

 from which the anterior root of the zygomatic process springs. Anteriorly the 

 temporal fossa is separated from the orbit by the zygomatic process of the frontal 

 above, and by the orbital process of the zygomatic and its junction with the lateral 

 border of the great wing of the sphenoid between its orbital and temporal surfaces. 



Laterally and in front, the fossa is overhung by the backward projection of the 

 fronto-sphenoidal process of the zygomatic bone, and it is under cover of this, and 

 within the angle formed by the frontal and orbital processes of the zygomatic 

 bone, that we see the opening of the zygomatico-temporal foramen, which pierces 

 the orbital plate of the zygomatic bone and transmits the zygomatico-temporal 

 branch of the zygomatic nerve a filament of the maxillary division of the 

 trigeminal nerve. The anterior part of the inferior orbital fissure opens into the 

 lower part of the temporal fossa, and thus establishes a communication between it 

 and the orbit. If the floor of the fossa is carefully examined, some more or 

 less distinct vascular grooves may be seen. One passing upwards over the 

 posterior part of the squamous temporal, immediately in front of and above 

 the external acoustic meatus, is for the middle temporal artery; two others, 

 usually less distinct, pass up, one over the temporal surface of the great wing of 

 the sphenoid, the other over the anterior part of the squamous part of the temporal ; 

 these are for the anterior and posterior deep temporal branches of the internal 

 maxillary artery. Inferiorly the temporal fossa communicates with the infra- 

 temporal fossa, beneath the zygomatic arch, the two being separated by an 

 imaginary horizontal plane passing medially at the level of that bony bridge. The 

 fossa contains the temporal muscle with its vessels and nerves, together with the 

 zygomatico-temporal branch of the zygomatic nerve and some fat ; all of which are 

 enclosed by the fascia which stretches over the space from the upper temporal line 

 above to the superior border of the zygomatic arch below. The extent and depth 

 of the fossa depends on the size of the temporal muscle, the development of which 

 is correlated with the size and weight of the mandible. 



Springing from the front and lower part of the squamous part of the temporal 

 is the zygomatic process of that bone ; it has two roots, an anterior and a posterior, 

 between and below which are placed the mandibular fossa in front, and the 

 opening of the external acoustic meatus behind. Of compressed triangular form, 

 the process at first has its surfaces directed upwards and downwards, but 

 curving laterally and forwards, it twists on itself, so that its narrowed surfaces 

 are now turned laterally and medially, and its edges upwards and downwards; 

 passing forwards, it expands somewhat, and ends in an oblique serrated surface, 

 which unites with the temporal process of the zygomatic bone completing the 

 zygomatic arch. It is the superior edge of this bridge of bone which forms the 

 posterior root. The inferior border, turning medially, forms the anterior root, and 

 serves to separate the temporal from the infra-temporal surface of the squamous part 

 of the temporal, blending in front with the infra-temporal crest on the lateral surface 

 of the great wing of the sphenoid. The inferior surface of this root is convex from 

 before backwards, and is thrown into relief by the mandibular fossa, which passes 

 up behind it. In this way a downward projection, which is called the tuberculum 

 articulare (O.T. eminentia articularis), is formed. 



The spina angularis of the sphenoid (angular spine) lies immediately to the 

 medial side of the articular part of the mandibular fossa. Its size and projection 

 vary. It is well to remember its relation to the condyloid process of the mandible 

 when that bone is in position ; lying, as it does, to the medial side and a little 

 in front of that process, it affords attachment to the spheno-mandibular liga- 

 ment. As will be seen hereafter, the anterior extremity of the osseous part of the 

 auditory tube lies just to its medial side. 



A noteworthy feature about the articular part of the mandibular fossa is 

 the thinness of the bony plate which serves to separate it from the middle 

 cranial fossa above. The vaginal process is a crest of bone which runs obliquely 

 forwards from the front and medial side of the mastoid process, just below the 



