382 DEVELOPMENT OF ORGANS IN MAMMALIA. [CHAP. 



By the fusion of the inner walls of the hemispheres 

 in front of the lamina terminalis a solid septum is 

 formed, continuous behind with the lamina terminalis, 



Transverse Section through the Brain of a Sheep's 

 Embryo op 2-7 cm. in length. (From Kblliker.) 



The section is taken a sliort distance behind the section 

 represented in Fig. 124, and passes through the posterior part of 

 the hemispheres and the third ventricle. 



St. corpus striatum ; th. optic thalamus ; to. optic tract ; t. third 

 ventricle ; d. roof of third ventricle ; c. fibres of cerebral 

 peduncles ; c'. divergence of these fibres into the walls of the 

 hemispheres ; e. lateral ventricle with choroid plexus pi ; 

 h. cornu ammonis ; /. primitive falx ; am. alisphenoid ; a. 

 orbito-sphenoid ; sa. presphenoid ; p. pharynx ; mk. Meckel's 

 cartilage. 



