VI.] THE PITUITAKY BODY. 119 



the pineal gland (Fig. 38, e), while the centre of the 



floor is produced into a funnel-shaped process, the infun- 



dibulum (Fig. 39, In), which, stretching towards the 



FIG. 39. 



LONGITUDINAL SECTION THROUGH THE BRAIN OF A YOUNG 

 PRISTIURUS EMBRYO. 



cer. commencement of cerebral hemisphere ; pn. pineal gland ; 

 In. infundibulum ; pt. ingrowth of mouth to form the 

 pituitary body ; mb. mid-brain ; cb. cerebellum ; ch. noto- 

 chord ; al. alimentary tract ; laa. artery of mandibular arch. 



extreme end of the oral invagination or stomodceum, 

 joins a diverticulum of this which becomes the pituitary 

 body. 



The development of the pituitary body or hypophysis cerebri 

 has been the subject of considerable controversy amongst embryo- 

 logists, and it is only within the last few years that its origin 

 from the oral epithelium has been satisfactorily established. 



In the course of cranial flexure the epiblast on the under side 

 of the head becomes tucked in between the blind end of the 

 throat and the base of the brain. The part so tucked in constitutes 

 a kind of bay, and forms the stomodaeum or primitive buccal 

 cavity already spoken of. The blind end of this bay becomes 

 produced as a papilliform diverticulum which may be called the 

 pituitary diverticulum. It is represented as it appears in a 



