DISSECTION OF THE BRAIN. 8 1 



arises from the ventral surface of the medulla back of 

 the pons. 



g. The Facial or VII. cranial nerve arises from the 

 outer side of the anterior border of the corpus trape- 

 zoideum behind the origin of the trigeminal. 



h. The Auditory or VIII. cranial nerve arises just 

 outside of and behind the facial nerve. It is larger 

 than the facial. 



i. The Glossopharyngeal and the Vagus, the 

 IX. and the X. cranial nerves, arise together by a num- 

 ber of slender roots from the side of the medulla behind 

 and to the outer side of the origin of the auditory nerve, 



j. The Spinal Accessory or XL cranial nerve 

 arises by a number of roots from the side of the cord 

 and medulla, extending forward as far as the origin of 

 the vagus nerve. 



k. The Hypoglossal or XII. cranial nerve arises 

 from the ventral surface of the medulla close to the 

 mid-line and just outside of the anterior pyramids. 



C. THE INTERNAL STU UCTURE OF THE BRAIN. 



1. The Cerebral Hemispheres {Fore-brain or pros- 

 £ncephalon). 



With a razor kept wet with alcohol take off hori- 

 zontal slices of the cerebral hemispheres, cutting care- 

 fully mitil the corpus callosuin is reached. 



a. Note the structure of the cerebral hemispheres: 

 the outer cortical layer of gray, matter folded into the 

 interior at the sulci, and the inner or medullary por- 

 tion of white matter — nerve-fibres. 



b. Notice the direction of the fibres of the corpus 

 callosum, running transversely from one hemisphere 

 to the other. 



