HEAD AND NECK OF THE HORSE 203 



because its surface is crossed by the external arcuate fibres (fibra? 

 arcuato3 externae) that traverse tlie lateral border of the medulla 

 oblongata obliquely. Behind the facial tubercle the medulla resembles 

 the lateral part of the spinal cord, and to the naked eye it appears as if 

 the lateral columns of the cord were merely prolonged into the medulla. 

 This appearance, however, is contrary to fact ; for the lateral column of 

 the cord contains fibres not present in a similar position in the medulla 

 {e.g. the crossed pyramidal tract). 



On each side of the dorsal median fissure there is a very conspicuous 

 funiculus cuneatas,^ continuous with the like-named I'asciculus of the 

 spinal cord. At the posterior end of the fourth ventricle the funiculus 

 diverges from the middle line, and appears to join the restiform body. 

 In reality, however, it ends at what is often called the cuneate tubercle, 

 though it is generally quite impossible to detect any specific elevation 

 that would justify the use of the term. By the divergence of the 

 cuneate funicles a glimpse of the clava - is usually permitted. This is 

 the termination of the funiculus ffvacilis^ that is not elsewhere 

 visible on the surface of the medulla, because the fasciculus giacilis of 

 the spinal cord, of which it is the continuation, disappeared from the 

 surface at the second cervical segment. The " cuneate tubercle " and 

 the clava contain collections of nerve cells (nucleus funiculi cuneati: 

 nucleus funiculi gracilis). 



Immediately behind the level of the posterior end of the ventricle, 

 and lateral to the funiculus cuneatus, there is an elevation to which the 

 name of tuberculum cinereuni is given. This is associated with the 

 iractus spinalis nervi trigemini that begins to form a low ridge on 

 the spinal cord at the second cervical segment. The tract gradually 

 increases in width as it is followed forwards into the medulla, and is 

 produced by an enlargement of the substantia gelatinosa covered by the 

 spinal root of the trigeminal nerve. 



The restiform * body (corpus restiforme) is a thick strand that, after 

 formino^ the floor of the lateral recess of the fourth ventricle, turns 

 abruptly dorsalwards and enters the hemisphere of the cerebellum. It 

 will be observed that the external arcuate fibres enter largely into its 

 formation. 



The Pons. — The pons is a transverse prominence between the 

 medulla oblongata and the cerebral peduncles. Its ventral surface is 

 convex from side to side with a very shallow antero-posterior groove 

 (sulcus basilaris) in the middle line. The dorsal surface assists in the 



1 (Jnneahis [L.], wedge-shaped. 



2 Clava [L.], a knotted branch, a club. ^ Gracilis [L.], thin, .slender. 

 * Eestis [L.], a rope or coid. Forma [L.], form. 



