THE CEREBRUM. 369 



it particularly deserving of notice. The Posterior Cornu ex- 

 tends from the base of the fornix to the distance of an inch or 

 more in the substance of the posterior lobe of the cerebrum. 

 Its cavity is conoidal, somewhat curved, with its convexity 

 outwards, and of six or seven lines in diameter at its base. Its 

 internal side is furnished with an oblong eminence called Hip- 

 pocampus Minor, or Ergot, from its resemblance to a cock's 

 spur, but its size and form are somewhat variable. When this 

 eminence is cut through transversely, it is easy to see that it is 

 formed by a convolution of the posterior lobe projecting into 

 the posterior cornu. The convolution is covered by medullary 

 matter on the side of the ventricle, and of course by cineritious 

 on the side of the periphery of the brain, and is the bottom of 

 an anfractuosity. 



The Inferior, Middle, or Lateral Cornu, of the Lateral ven- 

 tricle is situated in the middle lobe of the cerebrum. It com- 

 mences at the posterior angle of the fornix, and winds down- 

 wards and forwards in a semicircle towards the fissure of 

 Sylvius, presenting its convexity outwards, and its concavity 

 within. Its floor is furnished in its whole length with an ele- 

 vated ridge, the surface of which is semi-cylindrical. This 

 ridge is the Cornu Ammonis, or Hippocampus Major, and in- 

 creases somewhat, both in breadth and elevation, as it winds 

 down the process of the ventricle. Its lower or anterior extre- 

 mity is terminated by two or three small tubercles, and is the 

 Pes Hippocampi. Occasionally the Hippocampus Major is 

 marked off by a middle- longitudinal fissure into two elevations, 

 of which the external is the smaller. On its concave side there 

 is the thin edge of medullary matter, continuous with the ex- 

 ternal margin of the fornix. The extremity of a knife handle 

 may be insinuated for a short distance between this edge and 

 the Hippocampus; it ceases about half way down the latter, 

 and in the natural state of the parts is concealed by the plexus 

 choroides. This edge is, as mentioned in the account of the 

 fornix, the Tsenia Hippocampi or Corpus Fimbriatum of the 

 lateral ventricle. Beneath the latter, and partially covered by 

 it, there is another body, which presents itself in the form of a 

 small cord of cineritious matter, is not quite so long as the 

 Taenia, and is called Fascia Dentata, from being divided into 



