782 



NERVOUS SYSTEM OF THE HORSE 



base blends in front with the junction of the striae 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 cerebrimi (Commissura aboralis cerebri). 



The pineal body is enclosed in a fibrous capsule from which numerous trabeculae pass inward, 

 dividing the organ into spaces occupied by round epitheUal 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 rliin-aJ 

 Ventral horn of 

 lateral ventricle 



thalaini 



FiG. 637. — Cross-section" of Br.\ix of Hoese, Natural Size. 

 Section passes through posterior part of third ventricle and is viewed from behind. 1, Longitudinal fissure; S, 

 hippocampus; 2', fimbria; 3, septum pellucidum; 4> lateral ventricle; 5, thalamus: 6, habenula; 7, third ventricle; 

 S, 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 tsenias 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 cm.) 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 



