1566 ^V^-' A MANUAL OF ANATOMY 



the spine of the axis to the transverse process of the atlas, and the dissector 

 will note that the great occipital nerve, preparatory to piercing the complexus, 

 winds round the lower border of the inferior oblique in a backward direction. 

 The obliquus capitis superior will be found extending upwards and inwards 

 from the transverse process of the altas to the occipital bone between the 

 outer parts of the superior and inferior curved lines. The rectus capitis 

 posticus major is to be shown extending from the spine of the axis upwards 

 and outwards to the outer part of the inferior curved line of the occipital 

 bone and the subjacent area. The rectus capitis posticus minor is partially 

 visible internal to the preceding muscle, but is also under cover of it. It 

 will be recognised as a fan-shaped muscle, lying very deeply, and extending 

 from the posterior arch of the atlas, close to the posterior tubercle, in a 

 radiating manner upwards to the inner third of the inferior curved line of 

 the occipital bone and the subjacent area. The suboccipital triangle will 

 now be exposed, lying between the inferior oblique, superior oblique, and 

 rectus capitis posticus major. Within this triangle the dissector, by exer- 

 ■cising great care, should expose and study the following structures : (i) the 

 posterior primary division (undivided) of the first cervical or suboccipital 

 nerve, lying in close contact with the vertebrarterial groove of the atlas ; 

 (2) the third part of the vertebral artery ; (3) the posterior occipito-atlantal 

 ligament (one half), and one half of the posterior arch of the atlas. The 

 suboccipital plexus of veins also occupies this triangle, from which the blood 

 is conveyed away by the vertebral and deep cervical veins. 



Up to this stage of the dissection it m.ay be presumed that the period 

 allowed for the subject to lie with its face downwards has expired. 



Removal of the Brain. — The brain may be removed whilst the subject lies 

 upon its face, but there is no objection to removing it whilst the subject lies 

 upon its back. The scalp having been previously dissected, together with 

 the temporal fascia and the origin of the temporal muscle, the cranium is 

 to be cleared for the saw by carrying a scalpel around it, passing about i inch 

 above the orbits, and about ^ inch above the external occipital protuberance. 

 The external table of the cranial bones is then to be sawn through, and there- 

 after the internal table is to be cracked by means of a chisel and mallet. The 

 calvaria is then to be eased all round by inserting the chisel, and forcibly 

 raised from the dura mater, which is adherent to it. The dura mater, being 

 now exposed, is to be carefully sponged and studied in situ. The superior 

 longitudinal sinus, which runs in an antero-posterior direction in the median 

 line, is to be laid freely open, and its interior examined. On either side of 

 this sinus the outlines of the Pacchionian bodies are to be noted, and the 

 ramifications of the middle meningeal artery are to receive attention. 



The dura mater is then to be divided on a level with the sawn margin of 

 the skull, its mesial attachments in front and behind being left intact. On 

 being raised towards the median line, the* subdural space will be freely ex- 

 posed, and the arachnoid membrane and pia mateir are to be examined. The 

 ■cerebral veins, as they pass to the superior longitudinal sinus, are to receive 

 attention, and it should be noted that the direction of these veins is from 

 behind forwards, so that the current of blood in them is opposed to that in 

 the superior longitudinal sinus. The cerebral hemisphere is now to be 

 slightly pulled away from the median line in order to expose the falx cerebri. 

 When this process has been studied, its attachment to the crista galli is to be 

 severed, and the process is to be thrown backwards towards the tentorium 

 cerebelli, after which the brain is to be removed. 



Assuming the subject to be lying upon its face, the posterior cerebral lobes 

 are to be raised, which will expose the tentorium cerebelli. This is to be 

 divided near the superior border of the petrous part of the temporal bone, 

 and for a short distance along the course of the lateral sinus on either side, 

 but the sinus is not to be laid open. At the same time the fourth and fifth 

 pairs of nerves are to be divided. Exactly in the median line the vena magna 

 <Jaleni is to be cut as it is about to enter the straight sinus. The tentorium 

 ■cerebelli, along with the falx cerebri, is then to be turned backwards, which 

 will expose the cerebellum. The cerebellar hemispheres are next to be care- 



