Dissection of Sheep^s Brain, 169 



Posteriorly to tlie origin of the eighth Pair of Nerves, from 

 the groove between the Pyramidal and Olivary bodies, the 

 Ninth or Hypoglossal nerve takes its origin : it is the motor 

 nerve of the Tongue. 



On looking at the Superior Surface of the Brain, in 

 addition to the points enumerated before, there may be seen, 

 by slightly separating the Cerebellum from the Medulla 

 oblongata, the triangular cavity of the Fourth Ventricle, the 

 apex of which, from its resemblance to the point of a pen, is 

 called the Calamus Scriptorius. On either side of the Medulla, 

 and continuous with the ' posterior '* columns of the Cord, are 

 the Restiform Bodies, which as they proceed forwards diverge 

 from each other, assist in forming the lateral boundaries of the 

 fourth ventricle, and then enter the corresponding hemisphere 

 of the Cerebellum, forming ii^ posterior-\ peduncles : in the me- 

 dian line is a furrow which terminates at the apex of the fourth 

 ventricle in the Ventricle of Arantius, which is the remains of 

 a canal which in the foetus extends throughout the entire 

 length of the Cord : on each side of the median fissure, and 

 separated from the Pestiform bodies by a very slight groove, 

 are two narrow white cords called the Fasciculi seu Eminentia 

 teres. Projecting into the fourth ventricle on either side are 

 two delicate vascular fringes, processes of the Pia Mater, 

 called the Choroid Plexuses of the Fourth Ventricle. 



On slightly separating the Cerebral Hemispheres, the longi- 

 tudinal fissure will be seen to be floored, as it were, by the 

 Corpus Callosiim, a thick stratum of transverse fibres, connect- 

 ing the two hemispheres of the brain, and forming the roof of 

 a space in the interior of each hemisphere, called the Lateral 

 Ventricle. 



border of the spine of tlie Scapula, the Acromion, and the Clavicle : if the head 

 is fixed it elevates the point of the shoulder ; if the shoulder is fixed it draws the 

 head more or less directly backwards. 



* i.e. Superior in Qitadruped. f Cf. supra, Pons Varolii. 



Z 



