932 



777 K NEtt VE SYSTEM 



The indusium (gyrus epicallosus s. supracallosus), considered to he a vestige 

 of the hippocampus, is a thin strip of gray substance superimposed upon the 

 corpus callosum and raised into two paired ridges by longitudinal fibre bundles 

 which constitute the me sal and lateral longitudinal striae. 1 The indusium and its 

 striae are continued cephalad into the gyrus subcallosus; perhaps, also, into the 

 parolfactory area (Fig. 681). 



The central connections of the rhinencephalon will be considered in the de- 

 scription of the internal configuration of the hemisphere. (See Fornix, Anterior 

 Commissure, etc.) 



Internal Configuration. Each cerebral hemisphere contains a cavity, the 

 lateral ventricle (jparacele), an extension of the primitive neural cavity carried 

 outward, its contours modified by the developmental changes in the growth history 

 of the secondary fore-brain vesicle. This central cavity is surrounded by the thick, 

 convoluted walls of nerve tissue which make 'up the bulky cerebral hemispheres. 

 The cerebral tissue, as elsewhere in the central axis, is made up of gray and white 



. FASCIOLA 



CINEREA 

 - GYRI ANDREAC 



RETZII 



DENTATE GYRt 



rrcENULUM 

 GIACOMINI 



FIG. 683. -Mesal view of a partly dissected cerebral hemisphere, to show the relations of nmbri.-t, lusciola 



cmerea, dentate gyre, and uncus. 



substances. Two well-marked types of gray substance are recognizable: (a) 

 the cortical, so named because its situation upon an interior white centre invites 

 comparison with the rind (cortex) of a fruit; (b) the massive ganglionic or nugget- 

 like masses not dissimilar from the thalamus already described, comprising, in 

 this division of the brain, the caudate, lenticular, and amygdaline nuelflTT *Thp 

 white substance fills out the entire space intervening between the cortex, the cavity 

 of the lateral ventricle, and the great basal ganglia, and is composed of myelinic 

 axones which connect the elements of the cortex with other parts of the' nerve 

 system, or with other regions of the cortex of the same or the opposite cerebral 

 hemisphere. 



If a brain, resting upon its basal surface, be sliced by successive horizontal 

 sections from above, the peripheral gray and internal white are brought into view. 



J The mesal strise are also called Striae Lancisii; the lateral stria?, Teniae tectae. 



