HYPOPHYSIS 437 



Like the cortex of the suprarenal gland, the anterior lobe of the hypophysis is the 

 larger part, and has a characteristic epithelial structure, whereas the portion associated 

 with the nervous system is smaller, with less striking morphological characters. Never- 

 theless the latter, in both cases, produces the more active extracts, and its products are 

 better understood. The anterior lobe of the hypophysis appears to "preside more 

 intimately over skeletal growth;" and overgrowth, acromegaly and gigantism are at- 

 tributed to its excessive activity. The administration of extracts of the posterior lobe 

 causes a rise in blood pressure, owing to the contraction of the vascular musculature, 

 thus resembling adrenalin in its action. Repeated injections cause emaciation; and 

 deficient secretion, or the removal of the gland, leads to a high tolerance for sugars 

 with the resultant accumulation of fat. "Thus normal activity of the posterior lobe 

 is essential for effective carbohydrate metabolism " (Gushing, The Pituitary Gland and 

 its Disorders, 1912). 



The posterior lobe consists of a mass of neuroglia cells, the pars nervosa, 

 and an epithelial investment, the pars intermedia. The latter is of special 

 interest since its cells, sometimes ciliated, tend to become arranged in 

 cysts containing a hyaline or colloid secretion. According to Stohr, these 

 cysts belong with the anterior lobe, and since the two lobes are in contact 

 near the anterior part of the infundibular stalk, it is possible that its ele- 

 ments have grown around and invested the pars nervosa, thus producing 

 the pars intermedia. Except anteriorly, however, the two lobes of the 

 hypophysis are generally separated by a cleft. 



The pars nervosa contains ependymal and neuroglia cells, but no 

 nerve cells and only a few nerve fibers. The ependyma lines the cavity 

 which extends downward into the lobe from the inf undibulum. According 

 to Tilney, "very often in the human hypophysis the lumen is not only seen 

 to be distended by large masses of colloid, but its walls are evaginated so 

 as to give rise to cysts of varying sizes, all containing colloid" (Mem. of 

 the Wistar Inst., No. 2, 1911). The colloid material is believed to be 

 evidence of a secretion which is eliminated into the third ventricle, and 

 which finds its way into the cerebro-spinal fluid. Possibly it may be given 

 off from the outer surface of the lobe, for the inconstant cavity or lumen 

 is not a typical duct; but the secretion apparently does not enter the blood 

 vessels, which in this lobe are neither abundant nor sinusoidal. Eosino- 

 philic cells are generally absent. 



PINEAL BODY. 



The pineal body (sometimes called the epiphysis) is a median dorsal 

 outpocketing of the diencephalon (Figs. 434 and 435), terminating in a 

 small nodule composed of neuroglia and round or polygonal epithelial 

 cells. The human pineal body contains no nerves (Kolliker) but below it 

 there is the commissura habenularum. A connective tissue capsule sends 

 prolongations into its interior and surrounds groups of epithelial cells, and 

 follicles. 



