yore ee, 
PITUITARY BODY. 504 
that some of its ventral fibres pass downwards into the posterior longitudinal 
bundle. Ferrier and Turner have traced fibres from the optic radiation across the 
middle line in the posterior commissure. 
The locus perforatus posticus (substantia perforata posterior) has already been 
described on p. 440. Some delicate bands of white matter, termed the tenia pontis, 
may frequently be seen emerging from the gray matter of this region; they then 
curve round the erura cerebri in close ea to the upper border of the pons, 
into which they ultimately sink (Fig. 335, p. 449). 
Corpora Mammillaria.— The corpora nen ater are two round white bodies, 
each about the size of a pea, which lie side by side in the interpeduncular space on 
the base of the brain, immediately in front of the locus perforatus posticus. 
Each corpus mammillare is coated on the outside by white matter derived 
from the anterior pillar of the fornix and contains, in its interior, a gray nucleus 
with numerous nerye-cells. fae important strands of fibres are connected with 
the corpus mammillare: (1) The anterior pillar of the fornix curves downwards in 
the lateral wall of the third ventricle to reach the corpus mamunillare, and its 
fibres end amidst the cells of that body. (2) A bundle of fibres, called the bundle 
of Vicq d’Azyr, which at first sight appears to be almost continuous with the 
anterior pillar of the fornix, takes 
origin in its midst and extends 
upwards into the optic thalamus, 
to end in fine arborisations around 
the large cells in the anterior Horsman of 
thalamic nucleus. (38) Another Anterior _ 
bundle of fibres, the pedunculus Reise site J 
corporis mammillaris, takes form Cia 
within the corpus mammillare and mammillare 
extends downwards in the gray Optic nerve — 
matter of the floor of the third Infundibulum —— 
ventricle, to reach the tegmentum 
of the mesencephalon. The ulti- 
mate destination of these fibres is 
doubtful. 
Tuber Cinereum and Infundi- 
bulum.—The tuber cinereum is a 
small, slightly prominent field of 
Pituitary body — 
gray Inatter, which occuples the Fre. 376.—Mestar Section THROUGH THE Prrvrrary REGION 
anterior part of the interpedun- IN A CHILD OF TWELVE MONTHS OLD. 
cular space between the corpora From a photograph by Professor Symington. 
mammillaria behind and the optic 
chiasma in front. From its fore-part the infundibulum, or stalk of the pituitary 
body, projects downwards and connects that body with the base of the brain. In 
its upper part the infundibulum is hollow, a small, funnel-shaped diverticulum 
of the cavity of the third ventricle being prolonged downwards into it. 
Pituitary Body (hypophysis).—This is a small oval structure, flattened from 
above downwards, and with its long axis directed transversely, which occupies the 
pituitary fossa in the floor of the cranium. It is composed of two lobes—a large 
anterior lobe and a smaller posterior lobe, which are closely applied the one to the 
other. The infundibulum, which extends downwards from the tuber cinereum, is 
attached to the posterior lobe. 
The infundibulum and posterior lobe of the pituitary body are developed in the form of 
a hollow diverticulum, which grows downwards from the floor of that part of the 
embryonic brain, w hich afterwards forms the third ventricle. The original cavity of this 
diverticulum becomes obliterated, except in the upper part of the infundibulum. In 
structure, the posterior lobe of the pituitary body shows little trace of its origin from the 
wall of the brain-tube. It is chiefly composed of connective tissue and blood- -vessels, with 
branched cells scattered throughout it. 
The anterior lobe has quite a different origin, and if any part of the pituitary body is 
functional, it is this lobe. It is derived by a tubular diverticulum, which grows upw: ards 
