GUIDE TO THE HEAD AND NECK 1565 



muscle. In removing this fascia the dissector will note that its deep surface 

 gives origin to the superficial fibres of the temporal muscle superiorly. The 

 upper portion of the temporal muscle is then to be studied, but it cannot be 

 followed at the present time beyond the level of the zygomatic arch. 



At this stage the dissector, in association with his companion, may take 

 the steps necessary for the removal of the brain, the subject being now assumed 

 to have lain for two days face downwards. It may, however, be preferable 

 to complete the dissection of the back of the neck. 



The trapezius is to be divided by a vertical incision about i inch from the 

 spines of the vertebrae, in association with the dissector of the upper limb. 

 The spinal accessory nerve is then to be dissected along the deep surface of 

 the muscle, in company with the superficial cervical artery, and the plexi- 

 form communication between the spinal accessory and the branches from 

 the anterior primary divisions of the third and .fourth cervical nerves is to^ 

 be shown. The insertion of the stemo-cleido-mastoid is to be in great part 

 detached and turned forwards towards the auricle. Assuming that the dis-r 

 sector of the upper limb has paved the way by dividing and reflecting the 

 rhomboid muscles and the serratus posticus superior, the splenius muscle 

 is then to be fully dissected in co-operation A^dth the dissector of the upper 

 limb. Its twofold condition at its insertion, namely, the splenius capitis 

 and the splenius colli, is to be clearly brought out. The muscle is there- 

 after to be divided by a vertical incision about i inch from the spines of the 

 vertebrje, a procedure which will enable the dissector to display more fully 

 the twofold condition of the muscle at its insertion. 



The trachelo-mastoid and complexus muscles fall next to be dissected, 

 the former being very narrow and ribbon-like, whilst the latter is a large and 

 powerful muscle, and is pierced by the great occipital nerve. Tendinous 

 intersections are to be looked for in these muscles, one in each, and in the 

 case of the complexus the condition of its mesial portion is to be carefully 

 looked to. The dissector will note that this portion presents an intervening 

 tendon, with a fleshy belly at either end, thus accounting for the name biventer 

 cervicis, by which the inner portion of the complexus is known. 



At this stage the second part of the occipital artery falls to be dissected. 

 Its princeps cervicis branch (arteria princeps cervicis) is to be dissected very 

 carefully, and preserved for immediate further dissection. The trachelo- 

 mastoid is to be divided, and the relation of structures in the mastoid region 

 from the surface downwards is to be carefully noted. The complexus is to- 

 be divided about 2 inches below its insertion, and on reflecting the muscle 

 the dissector should follow downwards the cirteria princeps cervicis. About 

 the level of the spine of the axis he will find that it anastomoses with the 

 deep cervical artery, which, he will note, ascends beneath the complexus. 

 The subsequent and final stage of this dissection consists in displaying the 

 structures of the infra-axial arid supra-axial regions. Below the level of 

 the spine of the axis the semispinalis colli muscle, as regards its fourfold in- 

 sertion, is to be made clear. The origin of this muscle must be dissected in 

 concert with the dissector of the upper limb. Ascending upon it there is, as 

 stated, the deep cervical arter^'. Passing inwards upon it will be found the 

 internal branches of the posterior primary divisions of the third, fourth, and 

 fifth cervical spinal nerves, whilst those of the sixth, seventh, and eighth 

 nerves pass inwards underneath the muscle. When the semispinalis colli is^ 

 removed the upper part of the multifidus spinae falls to be dissected. The 

 interspinales muscles, along with the ligamentum nuchae, are next to receive 

 attention, and the tendinous slips of insertion of the cervicalis ascendens and 

 transversalis cervicis into tubercles (posterior tubercles) of transverse pro- 

 cesses are to be made evident. At this stage the dissector should familiarize 

 himself with the relative position of muscles, proceeding from the tubercles 

 (posterior tubercles) of cervical tiansverse processes, and passing backwards 

 to the cervical spines. 



Above the level of the spine of the axis four muscles and the suboccipital 

 triangle, with its contents, require very careful dissection. The obliquus- 

 capitis inferior will be found extending obliquely outw^ards and upwards from 



