782 NERVOUS SYSTEM OF THE HORSB 
base blends in front with the junction of the striz medullares of the thalamus. 
Immediately under the posterior part of the stalk is a short transverse band of white 
matter, the posterior commissure of the cerebrum (Commissura aboralis cerebri). 
The pineal body is enclosed in a fibrous capsule from which numerous trabecule pass inward, 
dividing the organ into spaces occupied by round epithelial cells of the same origin as the epen- 
dyma of the ventricle. 
The mammillary body (Corpus mammillare) is a white, round elevation a little 
larger than a pea which projects ventrally at the anterior end of the median furrow 
of the interpeduncular fossa. While it is a single body in external form in the horse, 
Sulcus rhinalis 
Ventral horn of 
lateral ventricle 
Optic tract 
Tenia 
thalami 
Fic. 637.—Cross-sEcTION OF BRAIN OF Horsr, NATURAL SIZE. 
Section passes through posterior part of third ventricle and is viewed from behind. 1, Longitudinal fissure; 2, 
hippocampus; 2’, fimbria; 3, septum pellucidum; 4, lateral ventricle; 5, thalamus; 6, habenula; 7, third ventricle; 
8, cerebral peduncle; 8’, hypothalmus; 9, mammillary body; 10, hypophysis or pituitary body; 11, piriform lobe; 
12, ventral end of hippocampus; 13, amygdaloid nucleus. Between the upper parts of the teniz thalami is the chorioid 
plexus of the third ventricle, and above this are the internal cerebral veins. 
sections show that it is double in structure and contains a nucleus of gray matter 
on either side (Fig. 637). 
Three sets of fibers are connected with the mammillary body. The column of the 
fornix curves down in the lateral wall of the third ventricle to the body and many of the fornix 
fibers end in it. A bundle (Fasciculus thalamo-mammillaris) passes dorsally and backward 
from it into the anterior part of the thalamus, and a tract (Fasciculus pedunculo-mammillaris) 
extends back in the floor of the third ventricle to the tegmentum of the mid-brain. 
The hypophysis cerebri or pituitary body was mentioned as covering part of the 
interpeduncular fossa. It is oval in outline, flattened dorso-ventrally, and nearly an 
inch (ca. 2 em.) in width. It is attached by a delicate tubular stalk, the infundibu- 
lum, to the tuber cinereum, a small gray prominence situated between the optic 
chiasm in front and the mammillary body behind. A fibrous capsule, derived from 
the dura mater, encloses and is intimately adherent to it. 
The body consists of two parts which can be distinguished on sections by their color (Fig. 639). 
The glandular lobe is brown in color and forms the external and greater part of the body. It is 
