2 1 8 ELEMENTS OE OEN ITHOIOGT. 



This organ consists of a main part called the cerebrum, formed 

 of two lateral rounded masses placed side by side called the cerebral 

 hemispheres, and which are medianly united to a certain extent. 

 Immediately behind them is a single, transversely marked body 



Kg. 167. 



Dorsal Aspect op Bbain of a Pigeon. 



2, One of the cerebral hemispheres ; 3, pineal gland ; 4, one of the optic 

 lobes ; 5, cerebellum. 



called the cerebellum, which if cut through shows a peculiarly 

 ramified disposition of a darker and a lighter substance, 

 termed the arbor vitce. On each side of the hinder part of the 

 cerebrum is a rounded body, and these two are called the optic 



Pig. 168. 



LBrT-siDE VIEW OP Brain of Pigeon. 



I, Olfactory lobe ; 2, left cerebral hemisphere; 3, pineal gland; 4, one of 

 the optic lobes ; 5, cerebellum ; 6, pituitary body ; 8, optic nerve, 



lobes, which lie rather beneath the front part of the cerebellum. 

 The common base of the brain continues backwards in the 

 median line, and is called the medulla oblongata, which is directly 

 continuous with the spinal cord. From the front end of each 



