THE BRAIN AND ITS MENINGES. 149 



extracted from it. That the vena portie does go for secre- 

 tion, the distribution of its capillaries, twining around the 

 minute ends of the biliary ducts, sufficiently proves. More- 

 over, the hepatic artery is not large enough to furnish all 

 the bile. This artery is not in communication with the 

 parts which would enable it to secrete : it nourishes the 

 substance of the liver ; the coats of the vena portee ; and 

 the tunics of the hepatic ducts ; but when it has done this, 

 the blood it contained is expended ; and its venous blood is 

 brought back by hepatic veins, and mingles with that of 

 the vena portse. It is the mouths of these veins, which, 

 penetrating the posterior cava as it passes along the top of 

 the liver, give the coats of the vessel the appearance of 

 being pierced by numerous holes. 



SECTION XII. 



NEUROLOGY. 



DESCRIPTION OF PLATE V. 



THE BASE OF THE BRAIN, SHOWING ITS NERVES AND ARTERIES. 



Fig 1 . — The brain, shoicing the origin of the nerves : 

 A, A, the hemispheres of the cerebrum ; 1, 1, the first pair, 

 or olfactory nerves, which confer the faculty of smell ; a, the 

 sinus, or cavity within the olfactory nerve, exposed ; 2, the 

 second pair, or optic nerves, upon the healthy state of which 

 vision is dependent ; b, the decussation, or rather, junction 

 of the optic nerves ; c, the corpus albicantium, or pituitary 

 gland ; d, the infundibulum, leading to and joining the 

 corpus albicantium at the base of the brain ; e, e, the crura 

 cerebri ; 3, the third pair, or motores oculorum, which go 

 exclusively to the eye for motion ; 4, the fourth pair, or 

 pathetic nerves, which chiefly proceed to the superior 

 oblique of the eye for motion ; /, the pons varolii ; 5, 5, 5, 5, 

 the flfth pair of nerves, or the first pair of mixed nerves, 

 being distributed principally about the head for motion and 

 sensation ; although from these spring the gustatory nerv^es, 

 or nerves of special sense. The subject from which this 

 brain w^as taken had the fifth pair of nerves unusually de- 

 veloped ; 6, 6, the sixth pair, or abducens, proceeding prin- 

 cipally to the abductor muscle of the eye for motion ; 7, 7, 



