BASE OF BRAIN 



457 



The facial nerve issues from the pons close to its lower 

 border, and just to the medial side of the acustic nerve, 

 by two roots, a large motor root, and a small sensory root 

 (O.T. pars intermedia). The two roots unite in the internal 

 acustic meatus. 



Abducent Nerve. This is a small nerve which emerges 

 from the groove between the lower border of the pons and the 

 lateral part of the pyramid. 



Trigeminal Nerve. This is the largest of all the cerebral 

 nerves. It appears at the side of the pons, nearer its upper 



A. Cerebral hemisphere. 



B. Cerebellum. 



D. Medulla oblongata. 



C. Pons. 



b, a. Mesencephalon. 



c. Brachium pontis. 



d. Restiform body. 



e. Lateral fissure. 



FIG. 185. Diagrammatic view of the manner in which the several parts of 

 the Brain are connected with one another. (From Schwalbe. ) 



than its lower border and in a line with the facial and acustic 

 nerves. It consists of two roots a large sensory root, portio 

 major, composed of a great number of fila loosely held together, 

 and a small, more compact motor root, portio minor, which 

 emerges antero-medial to the point at which the sensory root 

 enters the pons. 



Trochlear Nerve. The superficial origin of the trochlear 

 or fourth nerve cannot be seen at present. It emerges from 

 the anterior medullary velum, on the dorsal aspect of the 

 brain-stem. It is a delicate little nerve which has a long 

 intracranial course. It winds round the lateral side of the 

 pedunculus cerebri, between the cerebrum and cerebellum. 



