1 170 



HUMAN ANATOMY. 



Fig. 1008. 



Thalamus 



Cau 



vertical and in immediate contact with a thin sheet of white matter, the external 

 capsule, which separates the nucleus from the claustrum. Its ventral surface is hori- 

 zontal and only feebly curved and is continuous in front with the caudate nucleus 



and farther backward, about its middle, with 

 the anterior perforated substance on the 

 basal surface of the brain. The lenticular 

 nucleus is unequally subdivided by two thin 

 concentric sheets of white matter, the ex- 

 ternal and internal medullary laminae, 

 into three segments. The outer of these, the 

 putamen, is much the largest and occupies 

 the base of the nucleus, being bounded by 

 the external capsule laterally and by the 

 external medullary lamina mesially. Of its 

 two somewhat rounded ends, the anterior 

 is the broader and extends farther forward 

 and alone joins the caudate nucleus of which 

 it morphologically is a part (page 1169). 

 The putamen is the most conspicuous part of 

 the lenticular nucleus, not only on account of 

 its size but also by reason of its darker color, 

 in which respect it corresponds with the caudate nucleus. This contrast depends 

 less upon the actual pigmentation of the cells of the putamen than upon the 

 lighter color of the other zones of the nucleus. In consequence of the small 

 number of fibres entering the external capsule from the putamen, the attachment 

 between the latter and the capsule is relatively loose and the two structures may be 



Lenticular 

 nucleus 



Reconstruction of corpus striatum and thala- 

 mus ; lateral aspect ; probe lies in space occupied 

 by internal capsule. Drawn from Steger model. 



Fig. 1009. 



Superior frontal gyrus 



Corpus callosum 



Septum lucidum 



Right lateral ventricle, 

 anterior horn 



Middle frontal gyrus 



Inferior frontal gyrus 



Caudate nucleus 



Internal capsule 

 Lenticular nucleus 



Temporal lobe 



Internal orbital gyrus Continuity of caudate and lenticular nuclei 



Frontal section of brain passing through anterior end of corpus striatum where caudate and lenticular nuclei are 



continuous below. 



readily separated. This condition influences the course taken by extravasations of 

 blood, which are frequent in this locality and may occupy a large part of the lateral 

 surface of the putamen. The remaining divisions of the lenticular nucleus are much 

 lighter in tint and together constitute the globus pallidus. They are subdivided 



