582 ANTERIOR AND POSTERIOR GANGLIA OF CEREBRUM. 



occupies all the cavity of the cranium, with the exception of 

 the fossa, formed on the inferior portion of the occipital bone. 

 It forms, as it were, a sort of efflorescence or expansion on the 

 top of the spinal column, into the centres of which on each side, 

 (corpus striatum and thalamus opticus,) we have now traced 

 all the fibres of the medulk oblongata and cerebellum. The 

 volume of the cerebrum, a structure which is peculiarly large 

 in man, is from eight to twelve times greater than that of the 

 cerebellum.* 



The corpus striatum, (anterior ganglion of the cerebrum,) 

 and the thalamus nervi optici, (posterior ganglion of the 

 cerebrum,) receive the fibres which come upwards from the 

 spinal marrow, and are continuous with those from the cere- 

 bellum. The corpus striatum is placed in front and slopes 

 obliquely upwards, forwards, and outwards, in the direction of 

 the anterior and middle lobes of the cerebrum, and thus 

 receding from its fellow of the opposite side, contributes to 

 form the cavities called the lateral ventricles. It is about two 

 and a half inches long, about an inch broad at its anterior part, 

 and is terminated in a tail-like process behind, which embraces 

 the upper portion of the thalamus. The thalamus is placed 

 more posteriorly ; it is about two inches long and one broad, 

 and is sloped downward and backward in the direction of the 

 posterior lobes of the cerebrum, and the posterior part of the 

 middle lobes ; by receding from its fellow of the opposite side, 

 it forms the upper and lateral boundaries of the third ventricle. 

 It is covered with medullary fibres on its outer face, and pre- 

 sents four rounded elevations. Three of these are found at its 

 posterior extremity ; one is above the other two, and is called 

 the tuberculum posterius superius ; those below consist of the 

 corpus geniculatum internum, and corpus geniculatum exter- 

 num ; and there is one in front called tuberculum ante- 

 rius. Its interior is composed of cineritious neurine, which is 

 continuous between the organs of the two sides, forming the 



* In three young subjects, Cruvielhier found the weight as follows : 



Ibs. oz. oz. 



Cerebrum, weighing 2 2 Cerebellum, 4 



28 " 8J 



25 " 5. 



