542 THE ORGANS 



Afferent Roots, their Terminal Nuclei, Secondary Tracts, and Tertiary 

 Neurones. — The optic tract here forms a part of the ventral surface of the brain. 

 The geniculo-cortical portion of the optic path forming a part of the optic 

 radiation may be seen. Other afferent paUial connections are hardly distin- 

 guishable among the fibres connecting thalamus and pallium. 



Efferent Suprasegmental Neurones. — A great part of the pes has now entered 

 the corona radiala. The part now about to enter the corona is the anterior limb 

 of the internal capsule (Fig. 360). The ansa lenticularis is, according to some 

 authorities, composed of fibres or collaterals from the pes to the lenticular nucleus. 

 The fibres of the anterior peduncle of the thalamus are evident. They are con- 

 sidered by some as composed of cortico-thalamic fibres. The anterior pillars of 

 the fornix (efferent rhinopallial) are shown cut through twice, the upper section 

 shows its earlier course emerging from the fimbria, the lower section is near its 

 termination in the mammillary body. 



For other structures of thalamus, epithalamus, and hypothalamus see Fig. 

 361. 



The Pallium. — In the white matter distinguish as far as possible the corona 

 radiata, the corpus callosum, and the long association bundles {inferior longitudinal 

 fasciculus, fasciculus uncinatus, ajid fasciculus arcuatus) (seep. 541). Note the 

 nucleus amygdaliformis , the anterior perforated space and the anterior commissure, 

 belonging to the rhinencephalon. 



Other details shown in Fig. 361 should be studied. 



The Cerebral Cortex.- — The following types of cells are found in 

 the cerebral cortex: (i) Pyramidal cells. This is the prevailing 

 type and is characterized by a long apical dendrite usually directed 

 toward the surface of the brain. This dendrite gives off branches, 

 and usually reaches the outer cortical layer, there to break up into a 

 number of branches. From the cell body are also given off a number 

 of basal dendrites. By the Golgi and EhrHch methods, gemmules 

 can be demonstrated on the dendrites. The axone proceeds from the 

 base of the cell (opposite to the apical dendrite) and usually passes 

 into the white matter. It gives ofl several collaterals on its way to 

 the white matter. (2) Stellate cells. These have dendrites passing 

 in various directions. Many, especially the smaller (granules), may 

 have short, axones (Golgi's second type). (3) PolymorpJious cells of 

 a triangular or spindle shape are usually found in the deepest layers of 

 the cortex and send their axones into the white matter. (4) Hori- 

 zontal cells (of Cajal), found in the outer layer, with long horizontal 

 dendrites and axones confined to the outer layer. (5) Inverted 

 pyramidal cells (of Alartinotti) with axones directed toward the 

 surface. (Fig. 363.) 



The largest cells of the cortex (giant cells of Betz) are very rich in 

 chromophilic substance arranged similarly to that in the efferent 



