CAPSULA INTERNA, CORPUS STRIATUM, INTBRBRAIN-GANGLIA. 367 



and the fronto-ocoipital association-bundle. Besides these, the entire white medullary 

 substance is here traversed by fibers of the corpus callosum. Only a few white fibers 

 pass from this region into the capsula interna. Of the tracts that are important 

 clinically there are essentially only the coronal fibers from the facialis and hypo- 

 glossus centers, and the speech-pathway, the transverse section of which is to be 

 assumed as lying somewhat lateral to the fasciculus fronto-ocoipitalis. The ventral, 

 cortical region belongs to the gyri orbitales, over which the olfactory lobe passes. 



A section made only a little farther back passes through, the most posterior 

 part of the septum pellucidum, and now cuts the pillars of the fornix, which ascend 

 there. I demonstrate such a transverse section (Fig. 172), because it is also well 

 adapted to show the course of the commissura anterior, the decrease in size of the 

 head of the nucleus caudatus, and the increase in that of the lenticular nucleus. 



The triangular, gray mass between the commissure and the caudate nucleus 

 by this time belongs to the central gray matter which covers over the thalamus. 

 The white fiber-tract that covers this mass and projects free into the ventricle is 

 the stria terminalis, especially that part of the same which arises from the anterior 

 commissure. 



Just posteriorly there lie in the same relation, and having a similar course, the 

 tracts of the tsenia thalami. Ventrally, the olfactory area begins to appear. 



A section made exactly where the olfactory lobe becomes" intimately connected 

 with the base of the brain (Fig. 173) strikes, farther dorsally, the posterior portion 

 of the septum, where are found the posterior pillars of the fornix. These have 

 reached their present position from the postero-ventral region of the brain. Their 

 transverse sections will be met with in all the succeeding illustrations until here 

 in front, where they turn toward the base of the brain and pass ventrally into the 

 central gray matter of the ventricle. Their oval frontal sections lie in the gray 

 matter directly in front of the transverse fibers of the commissura anterior. 



The lateral ventricle, here only a fissure, lies lateral to the pillars of the fornix; 

 into it projects the most anterior portion of the thalamus, the nucleus anterior. 

 This is covered over by white fibers, which penetrate into its interior, and here 

 separate it from the nucleus lateralis thalami. The thalamus here receives fibers at 

 its lateral and at its ventral surfaces. The lateral fibers come from the capsula 

 interna and belong, the same as the ventral fibers, to the fiber-systems coming from 

 th^ cortex, as well as from the corpus striatum. Those fiber-tracts, especially, which 

 enter at the ventral end are plainly formed by the inferior pedicle from the temporal 

 lobe and the lenticular loop -from the corpus striatum. 



In the plane of this section the fibers from the anterior central gyrus have 

 in large part become mingled with those of the internal capsule. This now contains 

 at least the coronal fibers for sight, the motor speech-pathway, the hypoglossus and 

 a part of the pyramidal fiber-system for the arm and hand. I'ibers from the caudate 

 nucleus, , which run ventro-posteriorly, pass through its tracts arising from the 

 mantle. The white medullary substance is still formed essentially as in the previous 

 sections. 



Lateral to the capsula interna there is now met with the greatest expanse of 

 the corpus striatum: the putaiSen and the tAVO divisions of the globus pallidus. 



Numerous medullary radiations arise in the first; they pass, in large part, into 

 the lenticular loop (ansa lentiformis). Ventral to the corpus striatum the trans- 

 verse section of the commissura anterior is recognized. It lies just over the olfactory 

 formation, the cortex and medulla of which may here, indeed, be separated from one 

 another. The entrance of the olfactory radiation into this is to be recognized. 

 From this region the tsenia thalami rises dorsally and enters the layer of white 



