408 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



tissue or vessels completely shut out (fig. 241). In this 

 interlacement unmistakeably participate also, as Arnold has 

 already remarked, fasciculi proceeding to the fornix from the 

 posterior parts of the gyms fornicatus, which expand over the 

 surface of the lower half of the septum pellucidum (fig. 241, 6r). 



The principal mass of the projection system, constituting 

 the corona radiata (stab-kranz), is covered both upon its con- 

 vex as well as upor? its median surface by the formations of 

 the already-named systems arising and terminating in the 

 cortical substance. The projection system is by no means, 

 however, composed of radiating fasciculi alone, which, like 

 those represented in fig. 233 proceeding from the occipital 

 apex (P'), penetrate directly into the ganglia, but it contains 

 also arched portions, the most remarkable instance of which is 

 the fornix, which represents in the optic thalamus the cortical 

 portion of the gyrus fornicatus. 



Another remarkable projection fasciculus pursuing this 

 direction is the stria cornea, the arch formed by which con- 

 nects the apex of the temporal lobe with the whole length of 

 the internal margin of the caudate nucleus. 



The number of fibres belonging to the projection system 

 entering a ganglion from any portion of the cortex must stand 

 in direct relation to the size of that ganglion which contains 

 the cells in which they terminate. The large anterior cerebral 

 ganglia of the caudate and lenticular nuclei develop by far 

 the largest portion of their mass towards the frontal extremity 

 of the hemispheres, thus constituting the head of the corpus 

 striatum and the cuneiform base of the lenticular nucleus. 

 Posteriorly, however, one of these ganglia runs out into an 

 attenuated process, the other into a dentated equally thin ridge. 

 It cannot therefore be doubted that the frontal lobes in these 

 (which are well known to be motor) ganglia are represented 



corpus albicans ; Gi, internal corpus geniculatum ; Ge, external cor- 

 pus geniculatum ; m th, fasciculi of corona radiata from the frontal 

 lobes in the optic thalami ; P, crusta of the cms cerebri ; Om, medul- 

 lary fibres proceeding from the occipital lobe to the cushion, to the 

 arm of the superior corpora bigemina, Bs ; to the two corpora geni- 

 culata, the arm of the lower corpora bigemina, Bi ; to the crusta of 

 the crus cerebri and to the lenticular nucleus. 



