PITUITARY BODY (Lat. pituitarius, relat ing to phlegm, from pituita, phlegm; connected with .spuerc, Gk. rr6eLy, ptyein. Lith. spianti, Lett. splaut, OChurch Slay. prima, plyuti, Goth. speitean, 011G. spfivan, Ger. spcien, AS. spizran, Eng. spew, and ultimately with Eng. spit). The bypophysis of the brain, often called the pitui tary body, is an appendage of the lower side of the 'twixt-brain in vertebrates. Its origin shows that it is a compound body, the different parts of which arise from different areas in the em bryo. When fully developed the pituitary body consists of three parts, a stalk, an anterior and a posterior lobe. This stalk arises as an evagina tion of the floor of the 'twixt-brain and is called the infundibulum. Its distal portion subsequent ly develops into the posterior lobe. In the lower vertebrates the stalk and posterior lobe are clear ly made up of nervous tissue. but in the higher animals the posterior lobe contain, very little nervous substance. The anterior lobe arises as
an evaginatiou or outgrowth of the upper sur face of the mouth, and only secondarily comes into connection with the other parts. It has a very characteristic structure, contains no ner vous elements, and resembles very closely a duct less gland. In no living vertebrate does the bypophysis have any known function, and even if it be granted that it is homologous with the suhneural gland of tunicates, its actual use to the animal, either past or present, would still be an open question. Numerous theories have been proposed to account for its structure and function, but none have met with very general acceptance. The most recent (1903) is that the pituitary body is in intimate nervous connection with the suprarenal capsules, and through them regulates the amount of oxygen absorbed by the blood. But this view is not adequately sup ported by clinical or experimental evidence.