CAPSULA INTEKNA5 CORPUS STRIATUM, INTERBRAIN-GANGLIA. 369 



originates and fibers from the stratum zonale, as well as fibers of a still unknown 

 origin, together form -a proper medullary capsule around the nucleus anterior. The 

 lateral part of this capsulCj and a portion of the ventral, may be traced far back- 

 ward as the lamina medullaris interna thalami. 



The tail of the nucleus caudatus of the corpus striatum is visible dorsally and 

 ventrally. On its mesial side it has the tract of the stria terminalis. Besides this 

 part of the corpus striatum there is visible the lenticular nucleus with its three 

 divisions, from which the fibers of the ansa lentiformis are seen to develop at pre- 

 cisely this level. 



These fibers pass to the basal part of the eapsula interna, which they cross to 

 enter the thalamic ganglia from below. For almost this entire distance they lie 

 upon the fiber-system, which likewise passes into the thalamus, as the inferior thal- 

 amic pedicle, from the temporal, lobe. 



The internal capsule here contains nearly the entire motor fiber-system. More- 

 over, it contains the pathways from the frontal lobe to the pons. Many coronal fibers 



Corpus callos 



Fornix ~ 



Niicl. ant 



Lam. med. int 



Nucl. lat 



Tsenia 



Nucl. medial 



Tr. thai, mam 



Fornix 



Ansa lentif 



Coram, med 

 Infundib ' 



Tuber cin., chiasma " 



Nucl. caud. 

 Tsen. aemic. 

 Latticed layer 

 Capsula interna 



Putamen 

 Insula 

 01 au strum 



' Comm. ant. 



/Thai, pedicle and 

 I ansa lentif. 



■ Nucl. amygdal. 



Fig. 174. 



pass from it into the thalamus. The motor speech-pathway still lies in the same 

 place as in the preceding figure. Ventral to the lenticular nucleus lies the com- 

 missura anterior, and under this we see the nucleus amygdalae. 



The optic thalami everywhere lie so close upon the internal capsule that dis- 

 eases only rarely come under observation in which the thalami alone are involved. 

 Even in these it often remains doubtful how many of the phenomena which appear 

 are to be referred to the thalami, since the function of the neighboring fibers of the 

 capsula interna was impaired indirectly. For this reason it has not yet been possible 

 accurately to determine the symptoms that are produced by disease of the optic 

 thalamus. According to Meynert, the innervation sensations of the upper extremi- 

 ties are thereby disturbed. In this manner are said to arise the delusive ideas con- 

 cerning the position of these members, and from these ideas, again, the forced posi- 

 tions. Motor paralysis is probably not produced by destruction of the thalamus; 

 just as little, sensory paralysis. Disturbances of sight in the form of homonymous 

 lateral hemianopsia, perhaps of crossed amblyopia also, were repeatedly observed. 



