120 HEAD AND NECK 



with a chisel chip away the floor of the hypophyseal fossa and 

 open up the sphenoidal air sinuses right and left which lie in 

 the body of the sphenoid bone below the fossa. They are gener- 

 ally of unequal size and may be replaced in some cases by a 

 single cavity. Attempt to pass a probe through the aperture in 

 the anterior wall of each sinus into the corresponding section of 

 the nasal cavity (Fig. no). 



Hypophysis Cerebri (O.T. Pituitary Body) (Fig. 40). 

 The hypophysis is an oval structure, slightly flattened from 

 above downwards, and with its long axis placed 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 hypophysis, the 

 line of separation between the two lobes is seen very distinctly. 

 The infundibulum, which connects the hypophysis with the 

 tuber cinereum of the brain, is attached to the posterior lobe 

 only (Fig. 40, 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, behind by the sterno- 

 mastoid, and in front by the middle line of the neck. Pass 

 the index finger from the chin to the sternum along the 



