Ii86 



HUMAN ANATOMY. 



cut oval bundle until, farther backward, it bends abruptly downward to disappear 

 in the white matter of the temporal lobe, to the outer side of the inferior horn of 

 the lateral ventricle, preparatory to ending in the cortex. 



The fundamental and archaic character of the rhinencephalon, this division of the hemi- 

 sphere appearing in animals in which the pallium is only feebly developed, early led to the 

 establishment of a special connection between the olfactory lobes of the two sides. When to 

 this necessity was added that of linking together the fore-parts of the temporal lobes, which are 

 to a considerable degree isolated, the establishment of a commissure supplementary to the 

 corpus callosum was effected. 



Fig. 1025. 



Corpus callosum 



Lateral ventricle 



Septum lucidum 



Anterior end of 

 fornix, cut 



Foramen of Monro 



Anterior pillars of 

 fornix 



Caudate nucleus 



Striate or terminal 

 vein 



Internal capsule 



Thalamus, anterior 

 nucleus 



Lenticular nucleus, 

 putamen 



Claustrum 

 Globus pallidus 



Anterior commissure Olfactory strands 



Frontal section of brain passing through anterior commissure. 



The hippocampal commissure connects the two hippocampi by means ot 

 fibres which cross in the psalterium (page 1158), in addition, some fibres thus under 

 going decussation join the longitudinal strands of the fornix and proceed towards the 

 thalamus. 



The Projection Fibres. — These fibres connect the cortex of the cerebral 

 hemisphere with the lower lying parts of the brain — the thalamus, the corpus 

 striatum, the tegmental region, the pons and the medulla — and the spinal cord. 

 Proceeding, as they do, from all parts of the extended cortical area towards nuclei 

 grouped within the compass of a relatively small space, the fibres, for the most part, 

 at first curve toward their objectix'e points and collectively form the extensive con- 

 verging tract known as the corona radiata. The greater number of the components 

 of the latter pursue a direct path to the lower levels and take part, therefore, in the 

 formation of the compact internal capsule. The projection fibres are by no means 

 uniformly numerous in all parts of the cortex, relatively few issuing from the frontal, 

 parietal and infero-lateral part of the temporal regions — areas which, according to 

 Flechsig, are particularly significant as association centres. Furthermore, the olfac- 

 tory cortex does not contribute to the corona radiata, its owm special projection fibres 

 being represented by the cortico-mammillary tract within the fornix (page 1 159). 

 The projection fibres are not exclusively corticifugal tracts, since the connections of 

 the thalamus are of a double nature, numerous corticipetal paths passing from this 

 great sensory nucleus to the cortex of the hemisphere. The projection fibres may 



