790 



NERVOUS SYSTEM OF THE HORSE 



laterales) } The ventral surface has the reverse configuration, and presents trans- 

 verse ridges and grooves. It forms the roof of the lateral ventricles, and the 

 septum pellucidum is attached to it medially. The fibers of the corpus callosum 

 (with the exception of the longitudinal striaj) run transversely and spread out 

 laterally in all directions in the central white matter of the hemispheres to the cor- 

 tex, forming the radiation of the corpus callosum (Radiatio corporis callosi) . 



The fornix is a bilateral structure composed of white fibers which arch chiefly 

 over the thalamus and the third ventricle. It is described as consisting of a body, 

 two columns, and two crura. The body (Corpus fornicis) is formed by the fusion of 

 the two arches of which the fornix is composed. It is triangular and overlies the an- 

 terior parts of the thalami and the third ventricle. The dorsal surface gives 



Interventricular foramen 

 Anterior coininissure 



Optic Optic tract 



chiasm 



Fig. 643. — Cross-section of Brain or Horbe, About Natural Size. 

 Section passes through optic chiasm, and is viewed from in front. 1, Longitudinal fissure; 2, septum pellu- 

 cidum: 3, columns of fornix; 4> lateral ventricle; 5, chorioid plexus; 6, corpus meduUare (central whit^ matter) of 

 hemisphere; 7, caudate nucleus; 5, lenticular nucleus; 5, internal capsule; iO, external capsule; J 1, insula. 



attachment medially to the septum pellucidum, and on either side forms part of the 

 floor of the lateral ventricle. The lateral border is related to the chorioid plexus of 

 the lateral ventricle and forms the inner boundary of the interventricular foramen. 

 The columns (Columnae fornicis) (Fig. 643)^ are two slender round bundles which 

 emerge from the body in front of the interventricular foramen and diverge 

 slightly as they curve ventrally and backward to the mammillary body. 



From the mammillary body the greater part of these fornix fibers are continued to the 

 thalamus by the thalamo-mammillary fasciculus (or bundle of Vicq d'Azyr). Others pass to 

 the cerebral peduncle. A portion of the fibers cross to the opposite thalamus and cerebral 

 peduncle. 



The crura (Crura fornicis)^ are much larger bands which diverge widely from. 



' It is generally believed that these constitute an olfactory path. 



' Also known as the anterior pillars. ' Also termed the posterior pillars. 



