THE BEAIN AND SPINAL CORD. 



203 



The Pituitary Body is formed from two elements (Fig. 167): 

 (1) An epiblastic hollow bud from the stomodaeuni (Fig 22 

 p. 30). 



roof plate pineal 

 optic, thalam. \. ~- "~\ -__^^ midbrain 



caudate nucleus ><^<^ r 5^fe™Jii^ corp. quad. 



lam. terminalis 

 olfact. lobe 



sulcus of Monro 

 ,,','i^^/~~corp. mam. 



hypothalam. part 3rd vent, 

 tuber ciner. 

 '<\~notoch. 



neural part of pituitary 

 buccal pituitary 

 phar. 



Fig. 167. — A schematic figure to show the parts derived from the walls of the 

 fore-brain. (After His.) 



(2) A neuroblastic bud from the floor plate of the 3rd ven- 

 tricle (fore-brain). 



The union of the two processes takes place at the anterior 

 extremity of the notochord. The epiblast of the stomodaeum 

 and the floor of the neural tube are in contact from the very 

 beginning ; subsequently the mesoblast grows in between the fore- 

 brain and the epiblast of the stomodaeum, but the parts which 

 form the pituitary adhere. The posterior or neuroblastic bud 

 becomes solid ; its structure is that of neuroglia into which many 

 vessels have grown carrying mesoblastic tissue with them. 



The anterior or stomodaeal bud embraces the posterior. While 

 its posterior wall remains quiescent, its anterior throws out solid 

 processes between which a network of vessels lies. This forms 

 the glandular part of the pituitary — reticulated rows of cells 

 surrounding blood channels — similar in structure to the medullary 

 part of the supra-renals, carotid bodies and parathyroids. The 

 trabeculae cranii form round the pituitary. When the basi- and 



