Horizontal section of the basal ganglia and adjacent structures. Note the thalamus (Th) in the wall of the third ventricle. In it can be seen the mamillo-thalamic tract (Mth) cut in section; behind, it projects to form a rounded eminence, the pulvinar (P). At the anterior end of the third ventricle is the descending column of the fornix (F) cut in section. Note the head of the caudate nucleus (Cd) projecting into the cavity of the anterior horn of the lateral ventricle (V), and the lentiform nucleus with its two parts, the putamen (P) and the globus pallidus (G). Between the lentiform nucleus and the head of the caudate nucleus is the anterior limb of the internal capsule (IC’), and between the thalamus and the lentiform nucleus the posterior limb of the internal capsule (IC’’). It may be noted that the pyramidal tract fibres occupy the anterior two-thirds of the posterior limb. Notice also in the section the tail of the caudate nucleus (Cd’), the claustrum (Cl) and the cortex of the insula (In).

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