The Development of the MammaHan Pitiiitaiy Body 



175 



embryo (5th month) is illustrated. The anterior lobe is a compact structure 

 of columns of epithelial cells devoid of lumina. Many of its cells are 

 granular in character, and are beginning to differ from the clearer cells, 

 which are in closer relation with the nervous tissue. There is a well- 

 marked cleft in the epithelium, which, in this specimen, is carried right 

 round the neck of the posterior lobe. The cells of the pars intermedia, or 

 that portion of epithelium derived from the anterior wall of Rathke's 

 pouch, which is closelj'- adherent to the wall of the cerebral vesicle, are 



Fig. 7. — Sagittal section through same pituitary as shown in fig. 6, but further to one side. 

 Drawing from a photograph. 



6, tongue-like process of epithelium spreading forward ; b', epithelial cells spreading backwards over surface of the 

 brain ; c, third ventricle ; d, anterior lobe ; g, epithelial cleft ; /(, posterior lobe ; p, l>Tnph space. 



widely spread over the surface of the neck and body of the posterior lobe : 

 they also tend to break up the neck of the lobe by passing into its 

 substance along with blood-vessels, and extend forwards in a thin layer 

 for some distance over the tuber cinereum. Fig. 7 shows the appearances 

 presented by the same pituitary in a section further from the middle line. 

 The anterior lobe is rather larger here than it is in the mesial plane. The 

 posterior lobe is small, and its neck, which is a very thin one, is not seen. 

 The cleft is still seen, but the epithelium covering the posterior lobe is 

 small in amount and is confined to that part of it which borders the cleft. 

 In the human embrj'o at this stage the intermediate part of the pituitary 

 VOL. I. — APRIL 1908. 12 



