508 



THE BRAIN 



lateral root is partly continuous with the superior brachium, and partly 

 with the corpus geniculatum laterale and the pulvinar. The superior 

 quadrigeminal body, the corpus geniculatum laterale, and the pulvinar 

 constitute the lower visual centres. 



Pedunculi Cerebri (O.T. crura cerebri). The pedunculi 

 cerebri constitute the chief bulk of the mesencephalon. 

 When viewed from below, they appear as two large rope- 

 like strands, which emerge, close together, from the upper 

 aspect of the pons, and diverge as they proceed upwards to 

 enter the cerebral hemisphere. At the point where each 



Corpus geniculatum mediale 

 Pulvinar. \ 



Stria terminali 



Corpus geniculatum 

 laterale 



Basis peduncul 



Optic tract 



Ant. perforated 

 substance 



Optic nerve 



Superior brachium 

 Inferior brachium 



Superior quadrigeminal body 



Inferior 

 quadrigeminal body 



Aquaeductus cerebri 



Posterior perforated 

 ~~ substance 



Corpus mamillare 

 Tuber cinereum 

 Optic chiasma 



FIG. 210. The Origin and Relations of the Optic Tract. 

 (Professor Thane, from Quairis Anatomy.} 



peduncle disappears into the corresponding hemisphere, it is 

 embraced, on its lateral side, by the optic tract and the gyrus 

 hippocampi. 



The pedunculus cerebri of each side consists of two parts, 

 viz., a dorsal tegmentum, which is prolonged upwards to the 

 region below the thalamus ; and a ventral basis (O.T. crusta), 

 which is carried upwards into the internal capsule on the 

 lateral side of the thalamus. When the base of the brain 

 is examined it is the basis pedunculi which is seen. It is 

 white in colour and streaked in the longitudinal direction. 

 On the exterior of the mesencephalon, the separation between 

 the two parts of the pedunculus cerebri (i.e. the tegmentum 

 and the basis pedunculi) is indicated by a medial and a 

 lateral groove or sulcus. The medial sulcus is the deeper 



