168 OSTEOLOGY. 



external acoustic meat us, to the angular spine of the sphenoid. Passing downward 

 and slightly forwards from the centre of this, and ensheathed by it in front and a 

 the sides, is the pointed styloid process, the length of which is extremely variable. 



In the recess between the posterior root of the zygoma and the upper curve< 

 edge of the meatus there is usually a depression, though in some instances thi 

 may be replaced by a slight bulging of the bone. If from the posterior root o 

 the zygoma a vertical line be let fall, tangential to the posterior edge of the meatus 

 a small triangular area is mapped off which has been named by Macewen the supra 

 meatal triangle. Surgically this is of importance, as it is the spot selected in whicl 

 to trephine the bone to reach the tympanic antrum. 



In the suture between the posterior border of the mastoid part of the tempora 

 and the squamous part of the occipital, there is usually a foramen (mastoid) fo 

 the transmission of an emissary vein from the transverse sinus within the cranium t 

 the cutaneous occipital vein of the scalp ; this opening, which may be double, varie 

 greatly in size, and is usually placed on a level with the external acoustic meatus. 



Fossa Infratemporalis. The side of the cranium in front of the anterior roo 

 of the zygomatic process of the temporal bone is deeply hollowed, forming th 

 infra -temporal fossa. The student must bear in mind that, in examining thi 

 space, the ramus and coronoid process of the mandible form its lateral wall 

 but this bone for the present being withdrawn, enables us to get a better vie\ 

 of the boundaries of the space. In front its anterior wall is formed by th 

 convex posterior or infra-temporal surface of the maxilla, which rises behind th 

 socket for the last molar tooth to form the tuber maxillare (maxillary tuberosity 

 Anteriorly, the infra- temporal surface of the maxilla is separated from its anterio 

 aspect by the rounded inferior margin of the zygomatic process which support 

 the zygomatic bone. This latter curves laterally and backwards, forming part of th 

 upper and anterior wall of the fossa. On the medial surface of this wall will be see] 

 the suture uniting the zygomatic and maxillary bones (sutura zygomaticomaxillaris 

 which runs obliquely upwards and medially to reach the lateral extremity of th 

 inferior orbital fissure, the inferior border of which forms the superior boundary o 

 the infra-temporal surface of the maxilla. On this aspect of the bone are t 

 be seen the openings of the foramina alveolaria, two or more in number, whicl 

 transmit the nerves and vessels to the upper molar teeth. The medial wall of th 

 infra-temporal fossa is formed by the lateral surface of the lateral pterygoid lamina 

 the width and shape of which varies greatly ; its posterior border is thin and sharj 

 and often furnished with spiny points, to one of which the pterygo-spinous ligamenl 

 which stretches from this border to the angular spine of the sphenoid, is attached 

 It occasionally happens that this ligament becomes ossified. Anteriorly the latera 

 pterygoid lamina is separated from the maxilla above by an interval called tb 

 pterygo-maxillary fissure. Below this the bones are apparently fused, but a carefu 

 inspection of the skull, together with an examination of the disarticulated bones 

 will enable the student to realise that, wedged in between the two bones at thi 

 point, is a part of one of the smaller bones of the face, the pyramidal process of th 

 palate bone (O.T. tuberosity of palate bone). 



The inferior border of the lateral pterygoid lamina is usually curved am 

 slightly everted. Superiorly, where the lateral pterygoid lamina is generally 

 narrower, it sweeps upwards to become continuous with the broad inferior surfaci 

 of the great wing of the sphenoid ; this, which overhangs in part the infra- tempora 

 fossa superiorly, is limited laterally by the infra-temporal crest, which separates iti 

 infra- temporal from its temporal surface. The infra- temporal surface of the grea 

 wing of the sphenoid is limited in front and below by the edge which forms th< 

 superior boundary of the inferior orbital fissure, whilst behind it reaches as fa: 

 back as the medial extremity of the petro-tympanic fissure, where it terminates ii 

 the angular spine. It is from this point that the suture (sutura sphenosquamosa 

 curves forwards and upwards to reach the region of the pterion. The infra-tempora 

 surface of the great wing of the sphenoid, and the lateral surface of the lateral 

 pterygoid plate, alike afford extensive attachments for the external pterygoic 

 muscle, whilst the former is pierced by minute canals for the transmission o: 

 emissary veins. Occasionally a larger vascular foramen is present (foramen Vesalii) 



