382 CORPUS STRIATUM. 



the fissure that separates the two hemispheres anteriorly ; and, 

 continue backwards almost as far as the commencement of the 

 fissure that separates them posteriorly : when they have attained 

 this length posteriorly, they form a considerable curve, first 

 outwards, then downwards, and afterwards forwards, so that 

 they terminate almost as far forwards as they commenced ; but 

 much deeper. 



At the posterior part of their curve, when they incline out- 

 wards, previous to their turn downwards, a process or continu- 

 ation of the cavity extends backwards, almost as far as the 

 cerebrum does itself. These elongations are called the posterior 

 cornua or sinuses, or the digital cavities. 



Each ventricle may, therefore, be divided into three parts, 

 viz. The portion under the corpus callosum ; the portion 

 which continues outwards and downwards, and terminates 

 below it : and the posterior portion. 



It has been compared to a ram's horn, by some who have 

 contemplated particularly the upper and lower portions of the 

 cavity ; and by others who have had the whole extent in view, 

 it has been called tricornis. 



The bottom, or lower surface of these cavities, is varied in 

 almost every part of its extent. The front part of the bottom 

 of each ventricle is a broad and convex eminence, which 

 becomes narrower as it proceeds backwards ; so that it resem- 

 bles a portion of a pear. It inclines outwards as well as back- 

 wards, so that the narrow posterior extremities of the two 

 bodies are farther from each other than the anterior broad ex- 

 tremities. 



The color of these bodies is cineritious externally ; but 

 they are striated with medullary matter within, and therefore are 

 called corpora striata. 



Between their posterior extremities are two other eminences, 

 which incline to the oval form, and have a white or medullary 

 color ; although their substance, when cut into, is slightly 

 striated : they are called the thalami nervorum opticorum. 

 These bodies are very near each other : and, being convex in 

 form, are in contact at the centre : they adhere slightly to each 



