XII.] 



THE CEEEBRAL COMMISSURES. 



381 



hemispheres. These commissures are (1) the anterior 

 commissure, (2) the fornix, and (3) the corpus callosum, 

 the two latter being peculiar to Mammalia. 



Fio. 124. 



Transveese Section through the Brain of a Sheep's 

 Embryo or 2'7 cm. in length. (From Kolliker.) 



The section passes through the level of the foramen of 

 Monro. 



St. corpus striatum ; m. foramen of Monro ; t. third ventricle ; 

 pi. choroid plexus of lateral ventricle ; /. falx cerebri ; th. 

 anterior part of optic thalamus ; ch. optic chiasma ; o. optic 

 nerve ; c. fibres of the cerebral peduncles ; h. comu am- 

 monis ; p. pharynx ; sa. pre-sphenoid bone ; a. orbito- 

 sphenoid bone ; s. points to part of the roof of the brain at 

 the junction between the roof of the third ventricle and 

 the lamina terminalis ; I. lateral ventricle. 



