94 THE STRUCTURE OF THE FOWL 



a hollow stalk, the infundibulum, and placed 

 immediately behind the optic chiasma. 



The two cerebral hemispheres form the most 

 conspicuous parts of the brain. Each presents 

 a convex surface looking towards the bones 

 of the cranium. With the exception of a 

 shallow groove, which possibly represents the 

 lateral fissure (of Sylvius) of the mammalian 

 brain, this surface is smooth. The hemispheres 

 are applied to each other by flat faces, and 

 are connected by a transverse band of nerve- 

 fibres known as the anterior commissure. 



The olfactory lobe of the fowl's brain forms 

 a projection in advance of the anterior end 

 of each cerebral hemisphere. From the lobe 

 the olfactory nerves take origin to pass to 

 the mucous membrane of the nasal cavity. 



The cavity of the embryonic vesicles is 

 represented in the adult brain by the ventricles 

 and the aqueduct. The lateral ventricles are 

 contained within the cerebral hemispheres, 

 and in the floor of each is an eminence, the 

 corpus striatum. An opening, the interven- 

 tricular foramen, connects the lateral ventricles 

 with the thii'd ventricle which separates the 

 two thalami from each other. The aqueduct 

 runs through the mid-brain and forms a 



