178 



ANATOMY OF THE CENTEAL NEHTOUS SYSTEM. 



a powerful structure which leaves the striatum far behind in size, and grows 

 out over the posteriorly located interbrain and midbrain, even extending 

 beyond the cerebellum in man. Very highly developed brains show, besides 

 this posterior growth, also a bending of the posterior half of the mantle 

 ventrally (Fig. 136). 



The most anterior part of the hemispheres — the frontal lobes — make 

 their appearance only in the highest mammal, viz. : man. 



From the great cortical extension of the mammalian mantle comes a 

 great mass of fibers; others pass into it. These fibers, collectively desig- 

 nated the Corona radiata, pass from the cortex posteriorly, to end in the 

 thalamus, cerebellum, medulla, and spinal cord. Other large bundles tra- 

 verse the hemispheres, connecting one territory of the mantle with another. 



**'"Uiwa.jrt«ifc*J'^*'^'** 



Fig. 123. — The brain of a marsupial [Tlii/lacinus) , within which the brain of 

 a reptile is so inscribed that the Psalteria coincide (compare Fig. 114). (After 

 Flower.) 



All of these taken together form under the cortex a great mass of white, 

 medullated substance, whose extension is relatively greatest in man; in 

 lower mammals it is only small, in many — the mouse, for example — it is 

 quite unimportant. 



While the Corona radiata passes backward, it courses between the two 

 nuclei of the striatum and associates itself with the fibers arising from them. 

 The whole fiber-complex is designated as the Capsula interna. How the 

 capsule is composed of fibers from the cortex and the striatl^m may be seen 

 in Fig. 102, which shows a mammalian brain with that of a fish inscribed. 



But all of these outgoing and incoming fibers lie in the brain-mantle 

 closely associated into a bundle which spreads out anteriorly. If the cortical 

 apparatus is disproportionately larger, if it is more strongly developed in its 



