128 THE BRAIN OF REPTILES 



' cerebral peduncle.' On the upper and inner part of each 

 of these composite peduncles, just anterior to the optic 

 lobes, there is a small 'projection, supposed to answer to 

 another very important ganglionic body, which, in higher 

 vertebrates, is known as the ' Thalamus.' As to the 

 identity of these bodies, however, some difference of 

 opinion exists. They, together with the inner faces of 

 the peduncles on which they are situated, constitute the 

 lateral boundaries of another brain cavity, known as the 

 ' third ventricle,' which is mostly covered over above, by 

 the backward extension of the cerebral lobes. 



A band of fibres, termed the ' anterior commissure,' 

 which connects certain regions of the two cerebral lobes 

 hereafter to be specified arches across the anterior part 



FIG. 60. Vertical Longitudinal Section of the Brain of Perch. (Mivart.) 1, Olfac- 

 tory lobe ; 2, cerebral lobe ; 3, pineal body ; 4, optic lobe, with large cavity within ; 

 5, cerebellum ; 6, pituitary body ; 7, hypoarium. 



of this Third Ventricle ; whilst the upper strata of the two 

 cerebral peduncles are connected by means of a smaller 

 ' posterior commissure,' crossing the posterior boundary of 

 this ventricle, just in front of the optic lobes. The 

 peduncles or attachments of the before-mentioned ' pineal 

 body ' are in structural relation with the posterior com- 

 missure. 



The Third Ventricle is continuous below with a funnel- 

 like prolongation, at the extremity of which is a structure 

 named the 'pituitary body,' not altogether unlike the 

 ' pineal body,' and whose use is similarly unknown. 

 Though present in Fishes and higher Vertebrata, the 

 pituitary body is especially large in many Reptiles. 



