loSo A MANUAL OF ANATOMY 



lobe is connected with the anterior part of the tuber cinereum by 

 means of the infundibulum. 



The infundibulum projects downwards from the anterior part of 

 the tuber cinereurh to the posterior lobe of the pituitary body. 

 Its upper part is hollow, and contains a funnel-shaped diverti- 

 culum of the cavity of the third ventricle. 



Structure. — The anterior lobe consists of several tubules, lined with epi- 

 thelium, and invested by capillary bloodvessels. The posterior lobe, though 

 developed from the brain, is destitute of nervous elements. It is composed 

 of a reticulum of connective tissue, which contains branched cells. 



Development. — The anterior lobe is developed from a diverticulum of the 

 buccal or stomatodseal epiblast, which is known as the pouch of Rathke. 

 The diverticulum grows upwards, and, when the cranio-pharyngeal canal 

 of early life becomes closed, the connection of the diverticulum with the 

 buccal epiblast is severed. The diverticulum thereafter becomes converted 

 into tubules, which form the anterior lobe. The posterior lobe of the pituitary 

 body and the infundibulum, which is connected with it, are developed as a 

 diverticulum which grows downwards from that part of the thalamencephalon 

 or diencephalon which forms the floor of the third ventricle. The cavity 

 of the diverticulum remains permanent in the upper part of its infundibular 

 portion, but elsewhere it becomes obliterated. The lower part of the diver- 

 ticulum thereafter becomes converted into a reticulum of connective tissue, 

 with branched cells, which forms the posterior lobe. 



Side of the Neck. 



The side of the neck has a quadrilateral outline, the boundaries 

 of which are as follows : superior, one half of the base of the inferior 

 maxilla, and a line prolonged from the angle of that bone over the 

 mastoid process to the inner third of the superior curved line of the 

 occipital bone; inferior, the clavicle, and one half of the upper border 

 of the manubrium sterni ; anterior, the middle line of the neck, 

 that is to say, a line connecting the symphysis of the inferior 

 maxilla with the centre of the upper border of the manubrium sterni ; 

 and posterior, a line connecting the inner third of the superior 

 curved line of the occipital bone with the outer third of the clavicle. 



Landmarks. — ^The base and angle of the inferior maxilla can easily 

 be felt, and the clavicle, together with the upper border of the 

 manubrium sterni, is conspicuous, A deep depression, called the 

 suprasternal or jugular fossa, is perceptible above the upper border 

 of the manubrium sterni, lying between the sternal heads of origin 

 of the sterno-cleido-mastoid muscles. The outline of the sterno- 

 cleido-mastoid muscle is readily discernible when the head is turned 

 so as to direct the face towards the opposite shoulder. The muscle 

 extends in a diagonal direction from the sterno-clavicular joint to 

 the mastoid process and outer half or two-thirds of the superior 

 curved line of the occipital bone, and it divides the side of the 

 neck into two triangles — anterior and posterior. A small 

 triangular interval may be felt between the sternal and 

 clavicular heads of origin of the sterno-cleido-mastoid, just 

 above the inner end of the clavicle, in which the common 

 carotid artery and internal jugular vein lie deeply. The external 



