ANATOMY, 



pansion, passing under the fornix, and 

 called the velum. 



The lateral ventricle contains certain 

 eminences, which form its sides; the cor- 

 pus striatum is the anterior and superior 

 eminence, grey on its external surface, 

 and striated internally. The posterior emi- 

 nence in each ventricle is called the thala- 

 mus nervi optici ; it is hemispherical, and 

 white, and joined to its opposite one by 

 an union of substance, called the soft com- 

 missure. The hippocampus major is a 

 large elongated eminence, lying in the de- 

 scending portion of the lateral ventricle : 

 and the hippocampus minor is u smaller 

 one, in the digital cavity. 



The pineal gland, orconarium, is found 

 behind the optic thalami. Its size is about 

 that of a small horse-bean ; its colour 

 grey, and figure conical. Two small me- 

 dullary chords connect it to the optic tha- 

 lami. In the substance of this body is 

 found a small quantity of a gritty matter, 

 nearly resembling sand. It consists of a 

 number of semi-transparent and light yel- 

 low grains. Soemmering, who first dis- 

 covered that this belonged to the healthy 

 structure of the brain, calls it the acervulus 

 of the pineal gland. This liitle body has 

 been more attended to and noticed than 

 it would otherwise have been, in conse- 

 quence of the chimerical dream of Des- 

 cartes, who represented it as the seat of 

 the soul. 



Below the pineal gland is a square por- 

 tion of the brain, divided into four super- 

 ficial eminences, called corpora quadrige- 

 mina, and from these a thin production 

 extends to the cerebellum, under the 

 name of valvula cerebri. 



By drawing asunder the optic thalami, 

 and separating their soft commissure, we 

 expose the third ventricle of the brain. 

 This appears as an oblong cavity, about 

 jin inch and a quarter in length. A round 

 medullary rope is seen in front of it, and 

 a similar one behind ; these are called the 

 anterior and posterior commissures. A 

 round aperture is observed under the an- 

 terior commissure, beyond which the ven- 

 tricle terminates by a pointed and conical 

 extremity, from which a short process is 

 continued to the pituitary gland, under 

 the name of infundibulum. The foramen 

 commune anterius is an opening observed 

 between the optic ihalami before they are 

 disturbed, and lending from the aperture 

 of communication, which connects the 

 two lateral ventricles under the fornix, in- 

 to the third ventricle. Just before the pos- 

 terior commissure a round opening is 

 found, leading through a shoi-t canal, in 

 front of the tubercula quadrigetnina, t o the 



fourth ventricle. It is named canulis me- 

 dius, iter ad quartum ventriculurn, or 

 aquseductus Sylvii. Thus the four first 

 ventricles of the brain have a free com- 

 munication with each other. 



Under the posterior lobes of the cere- 

 brum there is found a transverse produc- 

 tion of dura mater, called tentorium,which 

 is attached to the internal transverse ridge 

 of the occiput behind, and to the petrous 

 portions of the temporal bone in front. 

 Under this membrane lie the two lobes of 

 the cerebellum, separated by a small per- 

 pendicular production, called the falx ce- 

 rebelli. 



The fourth ventricle is a cavity, left be- 

 tween the upper and posterior surface of 

 the medulla oblongata,and the front of the 

 cerebellum. It extends laterally to a con- 

 siderable distance in the crura cerebelli : 

 a groove runs along the middle of the me- 

 dulla oblongata, which constitutes the 

 front of the ventricle, and terminates at 

 the end of the cavity in a point. From the 

 lateral productions, and the pointed ter- 

 mination of the cavity, it has been named 

 the calamus scriptorius. 



The pituitary gland is a firm substance, 

 differing in texture from the brain, and 

 lodged in the sella turcica. Its name is 

 derived from a supposition that it secreted 

 the mucus of the nose, which in ancient 

 times was supposed to flow from the head. 

 It is connected by the infundibulum to the 

 basis of the brain. Behind the last men- 

 tioned part, at the basis cerebri, are seen 

 two small rounded eminences, called cor- 

 pora subrotunda. The crura cerebri are 

 two large medullary processes going from 

 the cerebrum to the medulla oblongata. 



The cerebellum is situated in the lower 

 fossae of the occipital bone, under the ten- 

 torium. It consists of an intermixture of 

 cortical and medullary substance, arrang- 

 ed differently from the order observed in 

 the cerebrum. A perpendicular section of 

 this part discovers a very elegant structure 

 in this respect. A thick trunk of medul- 

 lary matter sends off processes, in every 

 direction ; from these other branches pro- 

 ceed, all of which are surrounded by cor- 

 tex. This is called the arbor vit<e. The 

 arbor vitae constitutes the cms cerebelli . 

 on each side, and these processes join the 

 medulla oblongata. 



The medulla oblongata is a large me- 

 dullary protuberance, resting on the busi- 

 lar process of the occiput. Its connection 

 with the crura cerebri and cerebelli have 

 been already noticed. A medullary chord 

 is continued from its posterior end, under 

 the name of medulla spinalis. 



^ Mir Ha spinal is. This is a roundish 



