THE CEREBRAL HEMISPHERIC 959 



(V) The terminal (ascending) cere be llo cortical pathway, arising as the fibres of 

 the superior peduncles of the cerebellum, decussating and ending in the red nucleus 

 and lateral nucleus of thalamus, is thence directly projected by new axones to the 

 somesthetic cortical area, or indirectly projected via thalamus (lateral nucleus). 



Connections of the Corpus Striatum. The connections of the caudate and len- 

 ticular nuclei with each other and with the cortex may be summarized as follows: 



(a) Fibres from the cortex to the caudate and lenticular nuclei, entering into 

 the formation of the corona radiata. 



(/;) Fibres from the caudate nucleus and putamen of the lenticular nucleus 

 coursing to the thalamus and hypothalamic region. Those from the caudate 

 nucleus pass through the internal capsule to traverse the globus pallidus, are joined 

 by the fibres from the putamen to again traverse the internal capsule and end 

 in the thalamus, forming the striatothalamic radiation. 



(c) Fibres coursing ventrad in the medullary lamina* of the lenticular nucleus, 

 and reenforced by additional fibres from the globus pallidus, course mesad to 

 the hypothalamic region to form the subthalamic radiation or ansa lenticulaiis 

 (described on p. 952). This radiation is further reenforced by the ventral stalk 

 of the thalamocortical radiation to form the ansa peduncularis (described on p. 952). 



The Olfactory Pathways. 1. Peripheral Pathway. Impressions from the 

 upper portion of the Schneiderian mucous membrane pass along the olfactory fila 

 (central processes of the intraepithelial bipolar olfactory cells) to the glomeruli 

 olfactorii in the olfactory bulb (Fig. 711). 



2. Central Pathway. In the glomeruli the impression is transmitted to the 

 brush-like, dendritic endings of the mitral cells and brush cells; the axones of 

 these cells carry the impression centrad to the gray masses of the olfactory tract, 

 trigonum olfactorium, anterior perforated substance, and adjacent parts (Fig. 

 706). These constitute the primary centres. 



The primary centres are connected with secondary or cortical centres (hippo- 

 campus, gyms dentatus, uncus) by the following tracts: (1) Lateral olfactory 

 stria?, from the olfactory trigone to the uncus, ending in the gyms ambiens and 

 gyrus semilunaris (p. 929). (2) Axones from cells in the olfactory trigonal 

 gray through the fornix to hippocampus. (3) Striae medialis (Lancisii) from the 

 trigone into gyrus subcallosus around the corpus callosum to gyrus dentatus and 

 hippocampus. 



The amygdaline nucleus is by some regarded as a cortical centre to which 

 impressions are carried by the taenia semicircularis. 



The fornix fibres arise from the pyramidal cells in the hippocampus and the 

 polymorphous cells of the dentate gyre. Some fibres traverse the median plane 

 as the hippocampal commissure to the opposite hippocampus; the remainder end 

 in the corpus albicans, gray nucleus, or, in small part, are retroflexed as the stria 

 medullaris thalami to the habenular ganglion. In the corpus albicans impressions 

 are transmitted to the cells of two nuclear masses; from the medial nucleus arise 

 axones constituting the fasciculus albicantis princeps, each axone bifurcating 

 and the diverging bundles forming, respectively, the albicantiothalamic and the 

 albicantiotegmental fasciculi (p. 908). 



The stria medullaris thalami consists of the following bundles ending in the 

 habenular ganglion: (a) Axones from hippocampus via forpix the cortico- 

 habenular tract; (6) axones from the hemiseptum of the septum lucidum and 

 olfactory gray the olfactohabenular tract; (c) axones from the thalamus to the 

 habenular ganglion the thalamohabenular tract. In the habenular ganglion 

 axones arise which pass as a distinct bundle ventrad through the tegmentum to 

 the gray of the posterior perforated substance (ganglion interpedunculare [inter- 

 crurale] of Gudden) the fasciculus rctroflexus of Meynert. 



The primary olfactory centres of the two sides are connected by the pars 



