222 HEAD AND NECK 



The meningeal veins may be regarded as being arranged in 

 two sets : one set consists of small channels which pour their 

 blood into the blood sinuses; the other set is composed of 

 veins which accompany the meningeal arteries and carry 

 their blood to venous trunks on the exterior of the cranium. 



Hypophysis Cerebri (O.T. Pituitary Body) (Fig. 91). 

 The over-hanging margin of the diaphragma sellae should be 

 cut away and the hypophysis carefully dislodged from the 

 fossa hypophyseos (O.T. pituitary fossa) of the sphenoid bone. 

 It is an oval structure, slightly flattened from above down- 

 wards, and with its long axis directed transversely. It consists 

 of a large anterior lobe, and a smaller posterior lobe. The 

 anterior lobe is hollowed out posteriorly so as to form a 

 concavity for the lodgment of the posterior lobe. If a sagittal 

 section is made through the body, the line of separation 

 between the two lobes is seen very distinctly. The infundi- 

 bulum, which connects the hypophysis with the tuber cinereum 

 of the brain, is attached to the posterior lobe only (Fig. 91, i). 

 Thus, even in the adult, there is a clue to the different modes 

 of development of the two lobes. The posterior lobe is derived 

 from the brain, whilst the anterior lobe is an off-shoot from 

 the primitive buccal cavity. 



When the inspection of the interior of the cranium is completed the 

 dissectors must fill the cranial cavity with tow steeped in preservative solu- 

 tion ; replace the skull-cap in position and retain it by bringing the scalp flaps 

 over it, and stitching them accurately together. The brain must be put in 

 a jar in a 5 per cent solution of formalin and placed aside till the dissection 

 of the remaining parts of the head and neck is finished. 



THE ANTERIOR PART OF THE NECK. 



After the skull-cap has been replaced and the scalp has 

 been stitched over it let the head hang down over the end of 

 the table, pull the chin as far from the sternum as possible 

 and fix it in position with hooks. Then examine the region of 

 the front of the neck. It is a large triangular area, bounded 

 laterally by the anterior borders of the sterno-mastoid muscles, 

 above by the lower border of the mandible, and below by the 

 middle part of the upper border of the manubrium sterni ; and 

 it is divided by the median plane into two smaller subsidiary 

 triangles, the anterior triangles of the neck, each of which is 

 bounded above by the mandible, posteriorly by the sterno- 



