242 



INTERNAL SECRETION 



pars nervosa, up into the infundibulum, and enters the 

 third ventricle. Other observers deny this. 



The pituitary receives nerve fibres from the cervical 

 sympathetic. 



Fig. 35. — Mesial sagittal section through the pituitary body of an 

 adult monkey (semi -diagrammatic) : a, optic chiasma ; b, 3rd ven- 

 tricle (infundibulum) ; e, pars anterior; /, cleft ; g, pars intermedia ; 

 h, pars nervosa (Herring). 



Development 



The anterior and intermediate parts are derived from 

 an outgrowth of the buccal epitheUum {Rathkes 'potich), 

 the cleft between them being the remains of the original 

 lumen of the invagination. The pars nervosa develops 

 as a hollow downgrowth of the third ventricle. In man 

 the cavity becomes obliterated. 



It will therefore be seen that the pars intermedia, while 

 morjjhologically related to the pars anterior, becomes 



