THE DUCTLESS GLANDS 



1331 



pituitary, while the neural epiblast becomes developed into the pos- 

 terior lobe (Fig. 547). 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. 548), many of which are 

 rilled with granules, and is richly supplied with large, thin-walled capil- 

 lary 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 



FIG. 547. Mesial sagittal section through the pituitary body of an adult monkey 



(semi-diagrammatic). (After HERRING.) 



a, optic chiasma ; b, third ventricle ; c, tongue-like process of pars inter- 

 media ; d, epithelial investment of posterior lobe ; e. anterior lobe ; /, epi- 

 thelial cleft ; g, pars intermedia ; h, posterior lobe. 



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 lobe. One must therefore conclude that the 

 colloid material secreted by the cells of this part passes directly into the 

 third ventricle. The amount of colloid material increases in animals 

 which have undergone extirpation of the thyroid gland. 



Our first clue to the importance of this organ in the normal pro- 

 cesses of the body was furnished by the observations of Pierre Marie, 

 who found that the morbid condition of ' acromegaly ' is associated 



