GUIDE TO THE HEAD AND NECK 1579 



The structures which pass through the sphenoidal fissure are next to be 

 carefully dissected, and their relative positions noted. 



Ptarygo-maxillary Region. — The temporal fascia and the part of the tem- 

 poral muscle above the zygomatic arch have been already dissected. The 

 masseter muscle has also been dissected. In order to expose the pter\'go- 

 maxillary region the dissector must proceed in a definite order. The zygo- 

 matic arch is to be divided in front of, and behind, the origin of the masseter. 

 This is to be done at first with the saw and then with the bone-pliers. The 

 zygomatic arch, bearing the origin of the masseter, is to be turned down- 

 wards until the sigmoid notch of the inferior maxilla is exposed. At this stage 

 the dissector is to show the masseteric nerve and artery emerging from the 

 pterygo-maxillary region over the sigmoid notch and entering the deep sur- 

 face of the masseter. The nerve and artery having been divided, the mas- 

 seter is to be stripped from the outer surface of the ramus of the inferior 

 maxilla as low as the angle of the bone. The extensive fleshy origin of the 

 deep part of the muscle from the inner surface of the zygomatic arch is to be 

 carefully noted. The dissector is next to turn his attention to the insertion 

 of the temporal muscle, noting how it extends downwards within the anterior 

 border of the mandibular ramus to the region of the third molar alveolus. 

 The long buccal nerve and the buccal artery are to be caught just within the 

 anterior border of the mandibular ramus as they pass forwards and down- 

 wards, or, at all events, they are to be separated from the deep aspect of the 

 insertion of the temporal muscle by pressure with the handle of the scalpel. 

 The coronoid process of the mandible is then to be got rid of by means of the 

 saw and bone-pliers in the following manner : ( i ) make a vertical cut from the 

 centre of the sigmoid notch downwards for fully i inch ; and (2) make a 

 horizontal cut from the anterior border of the mandibular ramus backwards 

 to meet the vertical cut at a right angle. In addition to these cuts through 

 the bone, the strongly tendinous fibres of the temporal muscle must also be 

 divided. The coronoid process, bearing part of the insertion of the temporal 

 muscle, is then to be turned upwards, and the muscle is to be stripped gradually 

 from the lower part of the floor of the temporal fossa. The deep temporcd 

 nerves, three in number, are to be looked for, as well as the anterior and 

 posterior deep temporal arteries. An effort should also be made to expose 

 the middle temporal artery, which, being a branch of the superficial temporal, 

 has had to pierce the temporal fascia and temporal muscle to reach the tem- 

 poral fossa. This artery ascends in the groove familiar to the dissector as 

 marking the outer surface of the squamous peirt of the temporal bone. 



Two other horizontal cuts with the saw and bone-pliers still require to be 

 made through the mandibular ramus. One is to be made immediately below 

 the neck of the inferior maxilla, thus leaving intact the insertion of the ex- 

 ternal pterygoid muscle. The other cut is to be made across the ramus from 

 its anterior to its posterior border on a level with the summit of the crown 

 of the third or last molar tooth, or, if this tooth be absent, as near that level 

 as possible. This will keep the dissector free of the inferior dental foramen 

 on the inner surface of the ramus, and will consequently leave intact the 

 inferior dental nerve and artery. 



The structures to be dissected in connection with the pterygo-maxillary 

 region are as follows : (i) the external and internal pterygoid muscles, the 

 former passing horizontally to the front of the neck of the inferior maxilla, 

 and the latter extending downwards and outwards to the inner surface 

 of the mandibular ramus between the inferior dental foramen and the 

 angle of the bone ; (2) the first and second parts of the internal maxillary 

 artery, the second part of the vessel usually lying upon the external pterygoid 

 muscle, but sometimes passing beneath it ; (3) the pterygoid plexus of veins 

 around the external pterygoid muscle ; (4) the spheno -mandibular ligament 

 (internal lateral ligament of the temporo-mandibular joint), emerging from 

 beneath the external pterygoid muscle and resting upon the internal ptery- 

 goid ; (5) the inferior dental and lingual nerves, emerging from beneath the 

 lower border of the external pterygoid and passing downwards, the former, 

 which is posterior in position, parting with it» mylo-hyoid branch close to 



