THE PITUITARY GLAND 253 



Observations indicate that certain i,Man<l or^janizations are purely 

 endocrine in nature. Among the outstanding endocrine organs are 

 the thyroid gland, the ])arathyroi(ls, the h\poi)hysis cerebri or 

 pituitary, and the adrenals. (Fig. lo").) 



THE PITUITARY GLAND. 



This name, literally meaning "phlegm," is said to have been 

 devised by Galen (130-200 a.d.), since that ancient anatomist- 

 physician thought that nasal secretions were produced by this 

 gland. It is also called the hi/pophysis cerebri, i. e., that which 

 grows imder the brain, and in mannnals is located in a little pocket 

 in the sphenoid bone on the floor of the skull posterior to the optic 

 chiasma. The connective-tissue sheath of the brain, the pia mater, 

 immediately surrounds it. The pituitary is connected with the 

 lower end of the infundibulum of the brain. It is found in all 



-Tiibcralis 

 Infundibulum 



Fig. 156. — Diagram of the pituitary gland of a mammal. (After Atwell, Gray's 



Anatomy.) 



the vertebrates, but its size in relation to the size of the entire 

 body decreases in successively higher groups. 



Four parts may be distinguished: an anterior lobe, or pars dis- 

 talis; an intermediate portion, or pars intermedia; an upward 

 forward part, the pars tuberalis; and a posterior lobe, the pars 

 neuralis. (Fig. loli.) It has a double embryonic origin. An 

 e^•agination of buccal epithelium (ectoderm) grows upward, forming 

 a jjocket, Hathke's ])ouch, toward the l)rain. At about the same 

 time there is a downward evagination from the floor of the dien- 

 cephalon, and Rathke's pouch comes into contact with it. These 

 two components form the pituitary gland, Rathke's pouch forming 

 the first three portions and the neural evagination forming the pars 



