MAMMALIA. 199 



composed of the tract of the larger portion of the Intermediate layer, after it 

 has been joined by the tract of the first convolution of the intercedent region. 

 It gives origin to the smaller portion of the fifth, the sixth, the hard portion 

 of the seventh, and to the ninth by its extension down the oblong medulla. 

 It will be, therefore, observed that, whilst the smaller portion of the interme- 

 diate layer supplies the third nerve, the larger portion of the intermediate 

 layer gives origin to the sixth, which is sent to the abductor and retractor 

 muscles, and can oppose all the others ; the fourth nerve, supplying the 

 superior oblique muscle by its origin behind the quadrigeminal bodies, 

 derives also some opposing power from the tracts proceeding to the restiform 

 body. 



FIG. V. 



THE SHEEP. 



(OVIS AEIES.) 



IT affords a side view of the brain, which has been divided at the median line. 



1. Great commissure. 2. Anterior crus of the fornix. 3. Anterior commissure. 

 4. Nates. 5. Pineal gland. 



FIG. VI. 



(THE SAME.) 



IT shows the lateral ventricles laid open, and continued into the bulb of the 

 olfactory nerve. 



1. Attachment of the great commissure to the septum lucidum. 



