140 



COMPARATIVE ANATOMY. 



remains in an embryonic condition, and can hardly be said to have a 

 physiological fu notion ; the brain of those Fishes in which this con- 

 dition is retained probably acts mainly as a reflex machine, 

 and there is little doubt that the mental processes 



Mol 



FIG 113A. LONGITUDINAL VERTICAL SECTION THROUGH THE ANTERIOR PART OF 

 THE TELEOSTEAN BRAIN. (Founded on a figure of the Trout's brain by Rabl- 

 Kiickhard.) 



Tco, roof of the optic lobes ; Tl, torus longitudinalis ; Cp, posterior commissure ; 

 Gp, pineal gland, with a cavity (Gfp 1 ) in its inteiior ; Ep, Ep, the ependyma, 

 which lines the walls of the ventricles ; t, point at which the epithelial roof of 

 the secondary fore-brain (pallium. Pa) becomes continuous with the lining of the 

 anterior wall of the pineal tube: the former is folded inwards at /; V.cm, 

 common ventricle of the secondary fore -brain ; V.t, third ventricle ; B.ol, N.ol, 

 olfactory bulb and nerve ; C.st, corpus striatum, which was formerly taken to 

 represent the whole of the prosencephalou, and which lies on either side of the 

 middle line; Ch.n.opt, optic chiasma ; Oi, inferior commissure (Gadden) ; Ch, 

 horizontal commissure (Fritsch) ; J, infundibulum ; ff, H l , hypophysis ; Sv, 

 saccus vasculosus ; Li, lobi inferiores ; Aq, aqueduct of Sylvius ; ftr, trochlear 

 nerve ; Val, valvula cerebelli. 



which take place in the cortical gray substance of the 

 brains of higher Vertebrates do not obtain in them. 



The mid-brain and cerebellum are by far the largest 

 portions of the brain (Figs. 114 and 115, Mil, HH\ while the 

 thalamencephalon is depressed between the prosencephalon and 



