Coronal section of a monkey's brain, injected with carmine gelatin. Examine the section with a hand lens and note particularly the ganglionic or central arteries (b) arising from the middle cerebral artery (a) and penetrating the basal surface of the brain in the region of the anterior perforated substance. These central arteries, although small by the standard of arteries elsewhere in the body, are rather large in comparison with the cortical arteries. They pass upwards to vascularize the basal ganglia, caudate nucleus (c) and lentiform nucleus (d). But, much more important, they supply with blood the internal capsule (e) through which passes, among other fibre systems, the pyramidal motor tract. Hence, the interruption of a central artery by a clot or embolus may lead to paralysis affecting the opposite side of the body. 

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