254 



THE ENDOCRINE GLANDS 



neuralis. (Fig. 157.) The connection of Rathke's pouch with the 

 mouth cavity disappears, and the original huiien of this pouch 

 is eliminated, due to the great OAcrgrowth of the anterior wall to 

 form the pars distalis. Lateral lobe enlargements on either sirle 

 unite with each other to form the pars tuberalis. The posterior wall 

 of Rathke's pouch remains relatively thin and forms the jjars inter- 

 media. In some forms the pars intermedia grows around the pars 

 neuralis. The original lumen in the downgrowth from the brain 

 disappears in most forms. 



Fig. 157.— Photograph of a section through the dicncephalon and pituitary of the 

 kitten. The inner Hghter portion of the pituitary is the neuralis and is surrounded 

 by the intermedia. There is a space between the intermedia and the adjacent masses 

 of the pars distaUs. 



The pars distalis (anterior lobe) of an adult pituitary is an 

 epithelioid mass with cells arranged in cords. Three types of cells 

 are recognized, namely, basophil cells, acidophil cells, and chromo- 

 phobe cells. In higher vertebrates there are relatively more of the 

 first two types. Between the cords and groups of ei)ithelioid cells 

 are sinusoidal capillaries. Around the outside of the lobe is a 

 dense connective-tissue ca])sule from which extensions ])ass into 

 the interior, separating the cohunns of cells and sui)])()rting the 

 vascular su])ply. 



The i)ars tuberalis resembles the ])ars distalis in structure. There 

 may be inc()m])lete follicular arrangements of cells with colloid 



