80 



NERVOUS SYSTEM. 



Fig. 9. 



fibres which runs in each hemisphere above the corpus callosum, on 

 the edge of the longitudinal fissure, is the superior longitudinal com- 

 missure of Mr. Solly. Its use is supposed to resemble that ascribed 

 to the inferior longitudinal commissure. The fornix is of a triangular 

 shape; and constitutes the upper paries of another cavity the third ven- 



tricle. Beneath the fornix, and 

 behind, are the pineal gland and 

 its peduncles, forming the pineal 

 commissure of Mr. Solly, re- 

 specting which so much has been 

 said, by Descartes, 1 and others, 

 as the seat of the soul. Within 

 it is a small cavity; and, after 

 six or seven years of age, it al- 

 ways contains some concretions. 

 Again, anterior to the pineal 

 gland, and immediately below the 

 fornix, is another cavity the 

 thirdventricle. Itsbottom is very 

 near the base of the brain, and 

 is formed by the nervous layer 

 which unites the peduncles of 

 the brain with the eminentige 

 mammillares. At the sides, it 

 has the thalami nervorum opti- 

 corum. 



In the lateral ventricles, situ- 

 ate on each side of the corpus 

 ^^^^^ callosum, some parts exist which 



e demand attention. In the upper 



Section of the Cerebrum, displaying the surfaces of . 



the Corpora Striata, and Optic Thalami, the cavity Or anterior nail, COffi monly Called 

 of the Third Ventricle, and the upper surface of anter i or cornu and in the ante- 

 the Cerebellum. . ' 



nor part ot this, two pyniorm 



a, e. Corpora quadrigemina, a testis, e nates, b. . * r* 



Soft commissure, c. Corpus caiiosum. /. Anterior eminences are seen, of a brown- 



2: ish-gray colour, which, owing to 

 their bein formed of an assem- 



commissure, s. Posterior commissure, p. Pineal blafiTC of alternate layers ofwhite 

 gland with its peduncles, n, n. Processus a cerebello , ,, , 



ad testes. m, m. Hemispheres of the cerebellum, h and gray SUDStanCC, are Called 



?e U r P e e beiTumr rmiform *'' " N tch ***** *' corpora striata, the anterior ce- 



rebral ganglions of Mr. Solly. 



Behind these, are two whitish medullary bodies called thalami ner- 

 vorum opticorum posterior cerebral ganglions which are situate be- 

 fore the corpora quadrigemina, and envelope the anterior extremities 

 of the crura cerebri. 



Three main sets of fibres may be distinguished in the medullary sub- 

 stance, of which the great mass of the cerebrum is composed. First, 

 the ascending fibres, which proceed from the sensory tract of the me- 

 dulla spinalis, and diverge from the thalami optici to the periphery of 



1 Tractatus de Homine, p. 5. 



