PARTS SEEX IX THE BASE OF THE CEREBRUM. 539 



In the middle it is prolonged into a hollow conical process, the infundi- 

 bulum, to the extremity of which is fixed the pituitary body. 



The pituitary body or hypophysis cerebri, formerly called pituitary gland, 

 from its being erroneously supposed to discharge pituita ii,to the nostrils, is 

 a small reddish grey mass, of a somewhat flattened oval shape, widest in the 

 transverse direction, and occupying the sella turcica of the sphenoid bone. 

 It consists of two lobes, of which the anterior is larger, and concave behind, 

 where it embraces the smaller posterior lobe. Its weight is from five to ten 

 grains. In the adult it is solid, and of a firm consistence. 



The anterior lobe consists of two kinds of matter, one hard and grey, the 

 other, situated within, softer and of a yellowish white colour. The posterior 

 lobe is darker and redder than the anterior. Both are very vascular. 



The pituitary body appears to approach in structure to the vascular or duct" 

 less glands, such as the thyroid and suprarenal bodies, &c. According to Sharpey's 

 observations, with which those of subsequent writers agree, it differs greatly in 

 structure, at least in its anterior and larger lobe, from any other part of the ence- 

 phalon. The substance of the anterior lobe appears to be constituted by a mem- 

 branous tissue forming little round cavities or loculi, which are packed full of 

 nucleated cells. The loculi are formed of transparent, simple membrane, with a few 

 fibres and corpuscles resembling elongated cell-nuclei disposed round their walls. 

 The cells contained in the cavities are of various sizes and shapes, and not unlike 

 nerve-cells or ganglion-globules ; they are collected into round clusters, filling the 

 cavities, and are mixed with a semi-fluid granular substance. This thin granular 

 matter, together with the cells and little specks of a clear glairy substance like 

 mucus, can be squeezed from the cut surface, in the form of a thick, white, cream-like 

 fluid. 



In the foetus, the pituitary body is proportionally large, and contains a cavity 

 which communicates, through that of the infundibulum, with the third ventricle. 

 This body is constantly present, and has the same connection with the brain in all 

 vertebrate animals. 



In the middle line of the base of the brain, in front of the optic commis- 

 sure, is the anterior portion of the great longitudinal fissure, which passes 

 down between the hemispheres. At a short distance in front of the com- 

 missure, this fissure is crossed transversely by a white mass, which is the 

 anterior recurved extremity of the corpus callosum. On gently turning back 

 the optic commissure, a thin connecting layer of grey substance, the lamina 

 cinerea, is seen occupying the space between the corpus callosum and the 

 commissure, and continuous above the commissure with the tuber cinereum. 

 It is connected at the sides with the grey substance of the anterior perforated 

 space, and forms part of the anterior boundary of the third ventricle : it is 

 somewhat liable to be torn in removing the brain from the skull ; and, in 

 that case, an aperture would be made into the fore part of the third 

 ventricle. 



At a short distance outwards from the lamina cinerea is the anterior per- 

 forated spot (locus perforatus anticus), a depression near the entrance of the 

 Sylvian fissure, floored with grey matter, and pierced with a multitude of 

 small holes for the passage of blood-vessels, most of which are destined for 

 the corpus striatum, the deeper portion of the brain beneath which it lies. 



The grey surface of each perforated space is crossed by a broad white 

 band, which may be traced from the middle of the under surface of the 

 corpus callosum in front, backwards and outwards along the side of the 

 lamina cinerea towards the entrance of the Sylvian fissure. These bands of 

 the two sides are named the peduncles of the corpus callosum. 



When the entire encephalon is viewed from below, the back part of the 



