528 



PHYSIOLOGY 



CHAP. 



cerebral cortex' which appears on the surface of the anterior 

 perforated space. 



The corpus striatum arises from the 'base of the telencephalou 

 in the cavity of the cerebral vesicles. Its position is invariable 

 from the fishes to man. Since it is covered by the palh'um it 

 cannot be seen in the intact brain ; in teleosteans only, in which 

 the pallium is composed of a thin membrane, it is visible, and 

 composes the entire fore -brain. The fish's brain, according to 

 Edinger, may be morphologically compared with a human brain in 



FIG. 261. Olfactory lobe of human brain. (His.) Hu, olfactory bulb; T, tract; 7'r.o., trigone ; 

 R, rostrum of corpus callosum ; p, peduncle of corpus callosum, passing into G.s., gyrus 

 subcallosus (diagonal tract, Broca) ; Br, Broea's area ; f.p., flssura prima ; F.s., tissura serotina ; 

 C.o., position of anterior commissure ; /,.<., lamina terminalU ; CA., optic chiasma ; T.o., optic 

 tract; p.olf., posterior olfactory lobe (or anterior perforated space); m.r., mesial root; l.r., 

 lateral root of tract. 



which the hemispheres have been excised but the corpus striatum 

 left ; to show this it is only necessary to draw a section of the 

 fore-brain of a bony fish within the diagrammatic outline of a 

 human brain. As shown in Figure 262, the fibres of the corpus 

 striatum lie in the region occupied in mammals by the anterior 

 part of the internal capsule (cf. Fig. 247, p. 492). In the lower 

 vertebrates (fish, amphibia, reptiles) the pallium is little or not 

 at all developed as compared with the basal ganglion; in birds, 

 although the mantle is developed, the basal ganglia always 

 forms the main part of the fore-brain ; in mammals lastly, and 

 particularly in man, owing lo the enormous development of the 

 palh'um, the basal ganglia become a purely secondary part of 

 the brain. 



