INTERNAL SECRETION 495 



(is more than 51 per cent, of animals survived the operation for a prolonged 

 >eriod and of these 68 per cent, showed no specific symptoms of any kind. 

 ?rom the contradictory observations it is evident that the subject needs 

 urther investigation. 



THE PITUITARY 



The pituitary is a small body lodged in the sella turcica of the sphenoid 

 j^ne. It measures 14 mm. from side to side, 8 mm. from before backward, 

 md 6 mm. from above down, and consists of an anterior lobe somewhat 

 pink in color, and a posterior lobe yellowish-gray in color. The anterior 

 lobe is much the larger and partly embraces the posterior lobe (Fig. 223). 

 The anterior lobe is developed from an invagination of the ectoderm of the 

 buccal cavity and consists of gland tissue surrounded by a thin envelope of 

 connective tissue. It becomes separated from the mouth by the fusion of the 

 sphenoid cartilages. The posterior lobe is an outgrowth from the mid-brain 

 and is connected with the infundibulum of the third ventricle by a short 

 stalk. In the early stages of its development it presents a central cavity 

 which is, however, soon obliterated by the growth of special tissues. It 

 (persists in the cat. It has been suggested that the term 

 hypophysis cerebri be reserved for the anterior lobe and 

 the term infundibular body for the posterior lobe. This 

 distinction appears to be desirable inasmuch as in their 

 origin, structure and functions they are separate and 

 distinct bodies. 



Histology of the Pituitary Body. If a mesial 



sagittal section be made through the pituitary it will ^_ 



present an appearance which in a general way is the FK 223 _ SAGITTAL 



same in many animals though the details vary some- SECTION OF THE PITU- 



what in each animal. In the monkey the arrangement F^^J^ 1 ^; 



of the anatomic parts (Fig. 224) is similar to the ar- mG p ARTOF TfeiRDVEN- 



rangement in man. It will be observed that the posterior TRICLE. a. Anterior 



'lobe is solid and that there is no open connection with ^ it a ^Jgfg3 



the cavity of the third ventricle; that it is invested, over of the i n f un dibulum, b. 



a large part of its surface, by a thin layer of epithelium, posterior lobe comiected 



: The anterior lobe, which lies in front of it is separated g^^^^sSi 



! by a cleft which is the remnant of the cavity of the tion of opt i c c hiasm.- 



'buccal pouch. Though the appearance of the ante- (Sdwalbefrom Qu*m.) 



rior lobe, and the epithelial investment of the posterior 



lobe is somewhat different, the latter is but a differentiation of the former, a 



procedure that takes place in fetal life. The e F^W ; ^^^tJs 



usually spoken of as the pars intermedia and regarded histo log ca ly and 



physiologically as a part of the posterior lobe. Superiorly the anterior I 



and the pars intermedia are united, though a portion of he at ter pas es 



upward and embraces, if it does not entirely surround the _infund ,bi Jar 



stalk- inferiorlv and posteriorly the two bodies also unite. The posterior 



S^ investment m the mi J -toe. 



The extent to which the epithelium invests the posterior lobe vanes in dii 



f erent animals, In the cat and dog it is almost complete. 



