HYPOPHYSIS 



435 



HYPOPHYSIS. 



i 



The hypophysis (i.e., a growth beneath the brain) is a rounded mass, 

 about half an inch wide and a quarter of an inch thick, attached to the 

 tip of the infundibulum, and lodged in the sella turcica of the sphenoid 

 bone. Its stalk of attachment to the infundibulum extends through the 

 fibrous membrane fastened to the four posts or corners of the sella, and 

 in removing the brain, the hypophysis is therefore often torn from its 

 stalk and left in the bony excavation. It is now known to be a most 

 important organ of internal secretion, consisting of two parts which are as 

 distinct from one another as the cortex and medulla of the suprarenal 

 gland. The anterior lobe is formed from Rathke's pouch (Rathke, Arch. f. 

 Anat., Phys., u. wiss. Med., 1838, pp. 482-485) which grows upward from 

 the oral ectoderm and encounters the knob-like posterior lobe which is a 

 part of the brain (Fig. 203, p. 216). The anterior lobe then sends up a 

 short process on either side of the posterior lobe, like the thumb and first 

 finger of a hand, and in later stages Gushing ventures to describe the pos- 



FIG. 447. DIAGRAMS OF THE HYPOPHYSIS CEREBRI. (From Morris's Anatomy, after Testut.) 



A, Posterior surface. B, Transverse section. C, Sagittal section, i, Anterior lobe; 2, posterior lobe; 



3, infundibulum; 4, optic chiasma; 5, infundibular recess; 6, optic recess. 



terior lobe as resting in the anterior lobe like a ball in a catcher's glove. 

 The anterior lobe becomes- separated from the roof of the mouth by the 

 obliteration of its duct, which is reduced to a slender solid epithelial strand 

 and ruptures in embryos of about 20 mm. A depression marking its former 

 outlet has sometimes been found in the vault of the pharynx, and there 

 may be a canal through the sphenoid bone, the craniopharyngeal canal, 

 which follows the course of the former duct. It is said that a small 

 "pharyngeal hypophysis," having the structure of the anterior lobe, is 

 constantly found near the pharyngeal end of this canal, on the under 

 surface of the sphenoid bone. 



The posterior surface of both lobes, as they appear in the adult, is 

 shown in Fig. 447, A, and a sagittal section is shown in C; the orientation 

 of the latter may readily be understood by comparing it with the region 

 of the optic recess in Fig. 434. 



The hypophysis can hardly be overlooked in examining the brain, and its existence 

 is recorded by the earliest writers. The epiphysis, on the top of the brain, was called 



