BASE, 535 



posterior perforated space, the corpora albicantia, and the tuber cinerenm, 

 from which is prolonged the infundibulum attached to the pituitary 

 body. 



The posterior perforated space (locus perforatus posticus) (fig. 

 376, X ) is a deep fossa situated between the peduncles, the bottom of 

 which is composed of greyish matter, connecting the diverging crura 

 together. It is perforated by numerous small openings for the passage 

 of blood-vessels ; and some horizontal white striffi usually pass out of the 

 grey matter and turn round the peduncles immediately above the pons. 



The corpora albicantia or mammillaria are two round white emi- 

 nences in front of this fossa, each about the size of a small pea, sur- 

 rounded by grey matter, and connected together across the middle line. 



The cori^ora albicantia are formed, as will hereafter be explained, by the 

 anterior extremities of the fornix ; hence they have also been named iulhs of 

 ilic forr.ix. In the foetus they are at first blended together, and they become 

 separatfd about the beginning of the seventh month. In most vertebrate animals 

 there is but one white eminence or corpus albicans in their place. 



The tuber cinereuin (fig. 376, if c) is a lamina of grey matter extending 

 forwards from the corpora albicantia to the optic commissure, -to which 

 it is attached, and forming, as afterwards described, part of the floor of 

 the third ventricle. In the middle it is prolonged into a hollow conical 

 process, the infundibulum, to the extremity of which is fixed the 

 pituitary body. 



The pituitary body or hypophysis cerelri (fig, 376, h), formerly called 

 pituitary gland, from its being erroneously supposed to discharge pitmia 

 into 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 l^one. It consists of two lobes, of which the 

 anteiior 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 

 veiy vasctilar. 



The pituitary body appears to approach in structure to the vascular 

 or ductless glands, such as the thyroid and suprarenal bodies, &c. Ac- 

 cording 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 encephalon. The substance of 

 the anterior lobe appears to be constituted by a membranous tissue 

 forming little round cavities or loculi, which are packed full of nu- 

 cleated cells. The loculi are formed of transparent, simple membrane, 

 with a few fibres and corpuscles resembling elongated cell-nuclei dis- 

 posed 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, to- 

 gether with the cells and little specks of a clear glairy substance like 

 mucusj 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 



