GUIDE TO THE HEAD AND NECK 1581 



because at this stage it is most desirable that the two dissectors should work 

 in concert. The foregoing cuts will isolate the symphysial portion of the 

 inferior maxilla, and so preserve the attachments of the anterior belly of the 

 digastric, genio-hyoid, and genio-hyo-glossus muscles. By a few touches of 

 the knife the mucous membrane on the inner surface of the mandible can be 

 cut. Thereafter a needle, threaded with a ligature, is to be pushed through 

 the tip of the tongue and through the tip (or columella) of the nose. The 

 needle having now been dispensed with, the ends of the ligature are to be 

 tightly drawn and fixed. The object in this procedure will be at once obvious 

 to the dissector, namely, to put the tongue as much upon the stretch as pos- 

 sible. In the further stages of this dissection the ligature can easily be un- 

 done so as to allow the tongue to retire to its normal position. The dissector 

 will now recognise structures which he has been advised to dissect partially 

 at a previous stage. The structures covered by the mylo-hyoid muscle are 

 now to be completely dissected and mastered, namely, (i) the lingual nerve, 

 with the submaxillary ganglion ; (2) the deep part of the submaxillary gland 

 and WTiarton's duct ; (3) the hypoglossal nerve ; and (4) the sublingual 

 gland, for the ducts of which the dissector is referred to the text. The 

 genio-hyoglossus muscle now admits of complete dissection, and it will well 

 repay the dissector to study it fully. Immediately extemeil to its extensive 

 insertion into the side of the tongue he should expose the tortuous ranine 

 artery. The genio-hyoid and hyo-glossus muscles have been already referred 

 to. This region is admittedly one of extreme complication and perplexity, 

 so that the dissector should not be surprised that no hard-and fast instructions 

 can be submitted for his guidance. He may, however, show the stylohyoid 

 ligament, the stylo-glossus muscle (already referred to at an earlier stage), 

 the stylo-pharyngeus muscle, and, in connection with that muscle the glosso- 

 pharyngeal nerve. 



The hyo-glossus muscle is to be divided near its origin and reflected towards 

 the tongue. This will expose a portion of the lingual artery, which is now to 

 receive the attention of the dissector, and may be fully studied with ad- 

 vantage. The branches of the vessel are to be dissected in accordance with 

 the text, and special attention is to be directed to the ranine artery. 



Superior Maxillary Nerve, Meckel's Ganglion, and Third Part of Internal 

 Maxillary Artery. — This dissection is one of considerable difiiculty, and the 

 dissector is advised to have before him for his guidance a section of the skull 

 bearing upon this region. The contents of the orbit having been entirely 

 removed, the skull is to be sawn through in a direction downwards and for- 

 wards from a point above the meatus auditorius extemus to the region of 

 the inner end of the sphenoidal fissure. This cut will pass through the 

 squamous part of the temporal bone and the great wing of the sphenoid. A 

 second cut with the saw is to be made in advance of the preceding, on a level 

 with the anterior border of the great wing of the sphenoid, and this is to meet 

 the first cut. The portion of bone included between these two cuts is to be 

 removed. The foramen rotundum is to be carefully laid open with the bone- 

 pliers, and the infra-orbital canal is to be opened with equal care. To open 

 the posterior part of this canal the bone-pliers will be sufl&cient, but the 

 anterior part of the canal, being somewhat deeply placed, will require the saw, 

 or the chisel and mallet. The superior maxillary nerve is now to be studied, 

 its straight course forwards through the foramen rotundum, upper part of the 

 sphenomaxillary fossa, infra-orbital canal and infra-orbital foramen being 

 conspicuous. Its orbital or temporo-malar branch is to be shown, as are also 

 the two short sphenopalatine branches which descend to Meckel's ganglion. 

 A little farther forwards the posterior superior dental nerve is to be shown. 

 This at once divides into two branches which descend upon the zygomatic 

 surface of the superior maxilla. Sometimes these two branches arise sepa- 

 rately from the parent trunk. Within the infra-orbital canal, in order from 

 behind forwards, the middle and cinterior superior dental branches are to be 

 sho^vn by carefully raising the infra-orbital nerve. The dissector should 

 exercise his own discretion as to the removal of bone to expose the course of 

 these two nerves. 



