THE PITUITARY GLAND. 131 



to be secreted (p. 41), the movements of the intestine to be in- 

 hibited (p. 79), whereas it has no action on the blood vessels 

 of the lungs or brain, which do not possess vasomotor nerves. 

 This similarity between the results which follow suprarenin in- 

 jection and stimulation of the sympathetic system is particularly 

 significant when we call to mind the fact that the medulla of the 

 adrenal gland is developed from the same embryonic tissue as 

 the sympathetic system. The clotting power of the blood is 

 diminished after injections of suprarenin. 



The Pituitary Gland. This occupies the Sella Turcica of the 

 base of the cranium and is composed of three portions or lobes. 

 The anterior lobe consists of large epithelial cells and is really 

 an isolated outgrowth from the epiblast of the upper end of the 

 alimentary canal. Its complete excision causes death in a few 

 days, but if only a part is removed, a condition called Jiypo- 

 pituitarism develops, of which adiposity and sexual impotence 

 are the main symptoms. When this lobe becomes excessively 

 active in man (because of hypertrophy), it causes a peculiar 

 growth of the bones, particularly of the lower jaw, thus making 

 the person look as if he were very powerful. This disease is 

 called acromegaly (Fig. 12), and besides the changes in the 

 bones, there is frequently considerable metabolic disturbance, 

 causing a mild form of diabetes. When the hypertrophy of the 

 anterior lobe occurs in youth, most of the bones of the body may 

 be affected, thus causing the condition known as giantism. 



The intermediary lobe is also composed of columns of epithe- 

 lial cells, but there is often some colloidal material between the 

 columns. This colloid differs from that of the thyroid in con- 

 taining no iodine. 



The posterior lobe is really a downgrowth from the brain, and 

 is composed of neuroglia mixed with some of the epithelial cells 

 of the intermediary lobe. This lobe can be excised without caus- 

 ing any evident change in the animal, but nevertheless it must 

 have some important functions to perform, because extracts of it, 

 when injected intravenously, have very pronounced effects, viz. : 

 (1) a rise in blood pressure; (2) a very striking diuretic action 

 (i. e., causes urine to be excreted) ; (3) secretion of milk. The 



