PREVERTEBRAL REGION 351 



be effected right up to the base of the skull. At this point great caution 

 must be observed, otherwise the pharyngeal wall or the insertions of the 

 prevertebral muscles will be damaged. The base of the skull having been 

 reached, the point of the knife should be carried across the basilar portion 

 of the occipital bone, between the pharynx and the prevertebral muscles, 

 to divide the thick investing periosteum. 



The basilar portion of the occipital bone must now be divided by means 

 of a chisel. Still retaining the part upside down, place the skull so that its 

 floor rests upon the end of a wooden block. Then apply the edge of the 

 chisel to the under surface of the basilar portion of the occipital bone, 

 adjust it accurately in the interval between the pharyngeal wall and the 

 prevertebral muscles, and with a wooden mallet drive it through the base 

 of the skull, inclining it, at the same time, slightly posteriorly. 



The next step in the dissection consists in making two saw-cuts through 

 the cranial wall. The head having been placed upon its side, the saw 

 must be applied to the lateral aspect of the skull, half an inch posterior to 

 the mastoid process, and be carried obliquely antero-medially to reach a 

 point immediately posterior to the jugular foramen. A similar saw-cut 

 must be made upon the opposite side of the head. 



To complete the dissection the dissector must again have recourse to the 

 chisel. Placing the preparation so that the floor of the cranium looks 

 upwards, divide the base of the skull, on each side, in the interval between 

 the petrous portion of the temporal bone and the basilar portion of the 

 occipital bone. Anteriorly, this cut should reach the lateral extremity of 

 the incision already made through the basilar portion ; whilst posteriorly, 

 it should be carried to the medial side of the jugular foramen to reach 

 the medial end of the saw-cut. When this has been done upon both sides 

 of the basilar portion, the anterior part of the skull carrying the pharynx and 

 the great blood-vessels and nerves can be separated from the posterior part of 

 the skull and cervical portion of the vertebral column. The only large 

 nerve which will be divided is the hypoglossal, but, as it is cut close to the 

 basis cranii, and above its connection with the ganglion nodosum of the 

 vagus, it retains its position. 



The pharynx and anterior portion of the skull should now be covered 

 with a piece of cloth soaked in preservative solution, and the whole 

 enveloped in an oil-cloth wrapper. It can then be laid aside until the 

 dissection of the prevertebral region and the ligaments of the cervical 

 vertebrae and the occiput have been completed. 



Returning to the posterior part of the skull and the cervical 

 portion of the vertebral column, the dissector should proceed 

 to define the attachments of the muscles which lie anterior 

 to the transverse processes and the bodies of the vertebrae. 

 These are three in number on each side, viz. : 



1. The longus colli. 



2. The longus capitis (O.T. rectus capitis anticus major). 



3. The rectus capitis anterior (O.T. anticus minor). 



Musculus Longus Colli. This is the most powerful of the prevertebral 

 muscles, and it lies nearest to the median plane. Its connections are some- 

 what intricate, but when it has been thoroughly cleaned it will be seen to 

 consist of three portions viz., upper and lower oblique parts, and an 

 intermediate vertical part. 



The lower oblique division arises from the lateral aspect of the bodies of 



