XIII 



PHYLUM CHORDATA 



285 



of hearing not hitherto met with. Bounded externally by the tym- 

 panic membrane and internally by the outer wall of the auditory 



C/fl 



/bin 



Clfl 



Meet, cbl 



FIG. 985. Brain of Rana. A, from above"; B, from below ; C, from the side ; D, in longitudina 1 

 vertical section. C'li, cerebellum ; Cer. H, cerebral hemispheres ; ch. pLv 1 , anterioV and 

 fh. /</.'-, posterior choroid plexus (removed in A); com, commissures, the two in front the 

 nt< rior and lii/i/iocampal, the two above'the sup<. rior or habenular and the posterior ; Cr. C, crura 

 ccrebri ; Di, diencephalon ; for. M, foramen of Monro ; i, iter, or aqueduct of Sylvius ; inf, 

 infundibulum ; Med. obi, nicdulla oblongata ; Off. /, olfactory lobe ; opt. ch, optic chiasma ; 

 Opt. I, optic lobe; oj0k_jZr-ptic ventricle; '/tin, stalk of pineal body '; pit, pituitary )ody ; 

 Sp. cd, spinal cord ; 1$, third ventricle ; v 4 , fourth ventricle ; f A', cerebral nerves ; ISp. %Sp. 

 spinal nerves. (From Parker's Practical Zoology. A C, after Gaupp ; U, from Wieders- 

 heim's Comparative Anatomy ; after Osborn.) 



