TUBERCULA QUADRIGEMIXA. 413 



noidea, by which, membranes it is firmly retained in its 

 place, and has a very slight connection with the brain. It 

 is oval transversely, and presents the appearance of two 

 lobes, of which the anterior is the larger. It is a firm body 

 consisting of cineritious matter externally, and medullary 

 within. On either side a depression is observed connecting 

 it, by two small canals, with the infundibulum. Though 

 called a gland, yet there is nothing in its structure or func- 

 tion, so far as we are acquainted, by which it can be placed 

 among the glands. 



Tubercula Quadrigemina. Dissection. Having the base 

 of the brain uppermost, draw the cerebellum forward and 

 remove the pia ma- FIG. 116. 



ter. These are four 

 beautifully white 

 bodies, situated 

 above the crura 

 cerebri, and behind 

 are connected with 

 the tlialami. The 

 superior are called 

 the nates ; the infe- 

 rior, the testes. It 

 is the nates which are connected with the thalami. The 

 testes are united to the cerebellum by two thin, white lam- 

 inae, called the processus a cerebello ad testes, which diverge 

 to tfye cerebellum, through and forming part of its crus. 

 Between these processes is seen a white layer of medullary 

 matter extending from one side to the other, forming the 



FIG. 116 represents a longitudinal section of .the Brain, the incision being 

 made along the middle line between the two hemispheres of the cerebrum. 

 a Inner surface of the left hemisphere, b Section of the cerebellum, dis- 

 playing the arbor vitae. c Medulla oblongata. d Corpus callosum. e Fornix. 

 / One of the crura of the fornix. g One of the corpora albicantia. h Septum 

 lucidum. i Velum interpositum. j Division of the middle commissure of the 

 third ventricle, k Division of anterior commissure. I Division of posterior 

 commissure, m Corpora quadrigemina. n Pineal gland, o Aqueduct of 

 Sylvius, or iter a tertio ad quartum ventriculum. p Fourth ventricle, q Pons 

 Varolii. r Crus cerebri s Tuber cinereum. t One of the optic nerves, u 

 Left olfactory nerve. 



