694 



OF THE FUNCTIONS OF THE NERVOUS SYSTEM. 



ble such an idea might seem, when the cranium of the higher Vertebrata alone 

 is examined, it at once reconciles itself to our reason, when we direct our atten- 

 tion to that of Reptiles and Fishes ; in which classes the size of the Cerebral 



[Fig. 188*. 



The drawing exhibits the cerebral connection of all the cerebral nerves except the 1st. It is from a 

 sketch taken from two dissections of this part. D. Posterior optic tubercle. The generative bodies of the 

 thalamus are just above it. E. Cerebellum. H. Spinal cord. i. Tuber cinereum. K. Optic thalamus divided 

 perpendicularly, w. Corpus restifonne. x. Pons Varolii. 6 b. Optic nerves : this nerve is traced on the left 

 side back beneath the optic thalamus and round the crus cerebri. It divides into four roots ; the first (g g) 

 plunges into the substance of the thalamus, the next runs over the external geniculate body and surface of 

 the thalamus, the third goes to the anterior optic tubercle, the fourth runs to D, the testis or posterior optic 

 tubercle, c. Third pair common oculo-muscular, arising by two roots like the spinal roots of the spinal 

 nerves, the upper from the gray neurine of the locus niger, the lower from the continuation of the pyra- 

 midal columns in the crus cerebri and Pons Varolii, p t. d. Fourth pair, apparently arising from the inter- 

 Cerebral commissure (ic), but really plunging down to the olivary tract (o t) as it ascends to the optic tuber- 

 cles, e m. Motor or non-ganglionic root of the fifth pair, arising from the posterior edge of the olivary tract. 

 e. Sensory root of the fifth pair running down between the olivary tract and restiform body to the sensory 

 tract. /. Sixth pair, or abducens, arising from the pyramidal tract, g. Seventh pair, facial nerve, or portio 

 dura, arising by an anterior portion from the olivary tract and by a posterior portion from the cerebellic 

 fibres of the anterior columns as they ascend on the corpus restiforme, w. h. Eighth pair, portio mollis, or 

 auditory nerve, with its two roots embracing the restiform body. i. Ninth pair, or glosso-pharyngeal ; and j. 

 Tenth pair, or par vagum, plunging into the restiform ganglion. J J. Fibres of the optic nerve plunging 

 into the thalamus; immediately below these letters is the corpus geniculatum Bxternum. k. Eleventh 

 pair, or lingual nerve; the olivary body has been nearly sliced off and turned out of its natural position; 

 some of the filaments of the lingual nerve are traced into the deeper portion of the ganglion, which is left 

 in its situation ; others which are the highest are evidently connected with the pyramidal tract. 1 ED.] 



or hemispheric ganglia is very small, in comparison with that of the ganglia of 

 Special Sensation ; and in which the latter evidently form but a continuation of 

 the Spinal Cord, modified in its function : so that, when we trace upward the 

 cavity of the spinal column into that of the cranium, we encounter no material 

 change, either in its size or direction. The four pairs of nerves of special sen- 



1 ["Solly on the Brain," Am. Ed.] 



