906 



THE NERVOUS SYSTEM 



The blood supply of the cerebrum may best be taken as an illustration of the general plan 

 of the blood-vascular system of the encephalon. The terminal or internal branches of the 

 surface plexus, derived from the posterior, middle, and anterior cerebral arteries, are arranged 

 into two groups, a central or ganglionic and a cortical group. The central branches themselves 

 form four groups in each hemisphere : — 



(1) The antero-mesial group consists of terminal branches from the plexus of the domain 

 of the anterior cerebral artery, which pass through the medial part of the anterior perforated 

 substance and supply the head of the caudate nucleus, the septum pellucidum, the columns 

 of the fornix, and the lamina terminahs. 



(2) The antero-lateral group consists of terminal branches from the domain of the middle 

 cerebral artery. These pierce the anterior perforated substance in two sub-groups — (a) the 

 internal and (b) the external striate arteries (fig. 713). The internal striate arteries pass 

 through the segments of the globus paUidus of the lenticular nucleus and through the internal 

 capsule, to both of which they give branches, and they terminate in the caudate nucleus and 

 thalamus. The external striate arteries are larger and more numerous. They pass upward 

 between the external capsule and the putamen, and then through or around the upper part 

 of the putamen into the internal capsule, where they form two groups, the lenticulo-thalamic 

 and the lenticulo-caudate groups. The former terminate in the thalamus and the latter in the 

 caudate nucleus. On account of its larger size at its origin and its direct linear continuation 

 with the internal carotid, emboh (thrombi) pass more frequently into the middle cerebral artery 



Fig. 713. — Diagram Showing the Manner of Distribution of the Cortical and Central 

 Branches of the Cerebral Arteries. 



Cortical arteries. 



External striate arteries. 

 Middle cerebral artery 



Caudate nucleus 

 Thalamus 



Tuber cinereum 



Optic tract 



Anterior perforated 

 substance 



Internal striate arteries 



than into the anterior cerebral artery. One of the lenticulo-caudate arteries which is larger 

 and longer than the others and which is a direct branch from the middle cerebral artery has been 

 called the 'artery of cerebral hemorrhage' (Charcot), on account of the greater frequency 

 with which it is ruptured. 



(3) The postero-medial central arteries are terminal branches of the posterior cerebral 

 artery. They also enter the anterior perforated substance, but supply the floor of the third 

 ventricle, the posterior part of the thalamus, and the hypothalamic region. 



(4) The postero-lateral group are also terminal branches of the posterior cerebral artery. 

 They supply the posterior part of the internal capsule, the pulvinar of the thalamus, the gen- 

 iculate bodies, the corpora quadrigemina and their brachia, the epiphysis, and the cerebral 

 pedunccs. 



The cortical group of the cerebral arteries arise from the anastomosing plexus in the pia 

 mater of the cortical surfaces of the hemisphere. They pass into the cortical substance both 

 from the summits of the gyri and from the walls of the sulci. They consist of short, medium, 

 and long branches, and pass at riglit angles into tlie gyri. The short branches terminate in the 

 cortical substance; the medium branches supply the more adjacent white substance, and the 

 longer branches pass more deeply into the general medullary centre of the hemisphere. 



All of both the central or ganglionic and the cortical arteries are terminal in the sense that 

 they do not anastomose in the substance of the cerebrum. 



The blood-vascular system of the other divisions of the encephalon is in accordance with 

 the same general plan of that of the cerebrum. Slight individual modifications of the general 

 plan are to be expected. 



