1190 PHYSIOLOGY 



while removal of the parathyroids is responsible for the nervous disturbances 

 and tetany observed after total extirpation of these organs. The matter 

 cannot yet be regarded as definitely settled. 



end. 



FIG. 548. Section of parathyroid. (KoHN.) 



ep, secreting epithelium ; pig, cells containing pigment ; cap, sinus-like 

 capillaries ; end, endothelial cells. 



THE PITUITARY BODY 



The pituitary body consists of two parts which have separate modes of 

 origin. An outgrowth from the buccal cavity in the embryo meets a hollow 

 extension of the anterior cerebral vesicle. The buccal ectoderm gives rise to 

 the anterior lobe and pars intermedia of the pituitary, while the neural epiblast 

 becomes developed into the posterior lobe (Fig. 549). In some animals the 

 posterior lobe remains hollow and retains its primitive connection with the 

 third ventricle of the brain, but in man it becomes entirely solid. The 

 anterior lobe in the adult consists of nests of epithelial cells (Fig. 550), many 

 of which are filled with granules, and is richly supplied with large, thin- 

 walled capillary blood-vessels. The anterior lobe is separated from the 

 posterior lobe by a cleft which is the remains of the original hollow outgrowth 

 from the buccal cavity. The epithelial tissue immediately surrounding this 

 cleft differs somewhat from that constituting the anterior lobe. The cells, 

 which present but few granules, are arranged in islets, separated by an 

 intervening tissue continuous with the main mass of the posterior lobe. 

 Many of the islets are hollow and enclose a colloid material. The colloid 

 material has been traced by Herring into the interalveolar connective tissue 

 and into the prolongation of the infundibulum which enters the posterior 



