MAMMALIAN. 49 



Avhich are collected together as they pass the anterior border of the remains of the 

 auditory nucleus, forming quite a broad bundle which may be traced onward to the 

 raphe where it decussates with its fellow from the opposite side. As we pass 

 upward the roots constantly diminish in number, and are presently replaced by the 

 small or motor root of the fifth nerve, the nucleus of which appears to be an upward 

 extension of the motor column from which the facial, abducens and hypoglossal " 

 roots are derived 



The caput cornu steadily increases in size and in the number of its cells, con- 

 tributing with the remains of the auditory nucleus to form the principal nucleus 

 from which the sensitive fibres of the fifth or trifacial nerve originate. The remains 

 of the auditory nucleus have at this height passed backwards towards the cerebellum, 

 together with the restiform columns (Fig. 16", ?•). The little group of cells lying 

 close to the remains of the auditory root is still persistent, and is now seen to be 

 in very close connection with the flocculus. 



(11.) The changes which are observable still higher up, in the form and structure 

 of the gray substance, are chiefly produced by the development of the pons Varolii 

 and the formation of the nucleus of the trifacial, the motor roots of which are 

 derived apparently from the upward extension of the fasciculus teres, and its sensi- 

 tive roots from a large pyramidal nucleus, composed of the caput cornu together 

 with the upward extension of the auditory ganglion. 



