654 



NERVOUS SYSTEM OF THE HORSE 



accessory nerves are connected by a linear series of roots with the lateral aspect of 

 the ventral surface of the medulla. The spinal part of the accessory nerve comes 

 forward along the edge of the medulla to join its medullar}^ root. 



The twelfth or hypoglossal nerve arises from the posterior part of the medulla 

 along the lateral edge of the pyramid. 



The parts that are visible when the brain is viewed from aljove are the cerebral 

 hemispheres, the cerebellum, and part of the medulla ol)longata. The cerebral 



Longitudinal 



fissure Olfactory bulb 



y 



Transverse fissure 



Frontal pole of hemisphere 



Cerebrum 



Occipital pole of 

 hemisphere 



Cerebellum 



\fcduUa oblongata 



Fig. 498. — Br.\in of Horse, Dors.\l View, about f Natural Size. 

 1, Entomarginal fissure; £, marginal fissure; S, ectomarginal fissure; 4. suprasylvian fissure. 



hemispheres form an ovoid mass, and are se]:)aratcd from each other by the median 

 longitudinal fissure, in whicli the falx cerebri is situated. Their surfaces are marked 

 by thick folds, the gyri cerebri, separated by sulci. The upturned ends of the 

 olfactory bulbs are seen in front of the frontal poles of the hemispheres. The 

 occipital i)oles of the hemispheres overlie the anterior part of the cerebellum, from 

 whicli they are separated \)y the transverse fissure and the tentorium cerebelli 

 contained in it. The cerebellum is a much smaller rounded mass which conceals 

 the greater part of the medulla oblongata. Its surface is divided into a middle 



