PRACTICAL CONSIDERATIONS : THE BRAIN. 1207 



The corpus striatum, both the caudate and lenticular nuclei, are supplied chiefly by branches 

 from the middle cerebral artery, which pierce the anterior perforated space and, as the lenticular, 

 lenticulo-striate and lenticulo-thalamic vessels, all end-arteries, traverse the lenticular nucleus 

 and the internal capsule and terminate in the caudate nucleus and the thalamus. One of the 

 lenticulo-striate arteries, which pierces the outer part of the putamen, was named by Charcot 

 the "artery of cerebral hemorrhage" since it is frequently ruptured. 



The choroid plexus of the lateral ventricle receives its blood-supply from the anterior and 

 posterior choroidal arteries. The first of these, given off by the internal carotid artery, enters 

 the anterior and lower part of the choroidal fissure and takes part in forming the most depend- 

 ent portion of the vascular complex which overlies the hippocampus. The posterior choroidal 

 artery, usually represented by a number of small twigs, is derived from the posterior cerebral 

 and enters the upper part of the fissure. After supplying the velum interpositum, it completes 

 the choroid plexus in the descending horn and in the body of the lateral ventricle. 



The cerebral hemispheres are supplied by the cortical branches of the anterior, middle and 

 posterior cerebral arteries. Of these the middle one is the largest and is distributed to the 

 most extensive area, which embraces the greater part but not all of the external surface of the 

 hemisphere. This vessel also supplies the outer half or more of the orbital surface and the 

 anterior part of the temporal lobe. The anterior cerebral is essentially the artery of the mesial 

 surface, the anterior two-thirds of which, in conjunction with an adjoining zone on the external 

 and on the orbital surface, it supplies. The distribution of the posterior cerebral is chiefly on 

 the mesial and tentorial surface of the occipito-temporal region, and in addition an adjoining 

 strip along the postero-inferior margin of the hemisphere. It follows, therefore, that, with the 

 exception of the occipital lobe, which is entirely supplied by the posterior cerebral artery, all of 

 the conventional divisions of the hemisphere receive their arterial supply from more than a single 

 source. 



The frontal lobe is supplied by the anterior cerebral artery : — over its entire mesial surface ; 

 over the superior and the anterior two-thirds of the middle frontal convolutions and the upper 

 end of the precentral convolution ; and over the orbital surface internal to the orbital sulcus. 

 Over all the remaining parts, the frontal lobe receives the branches of the middle cerebral 

 artery. 



The parietal lobe is supplied by the middle cerebral artery on the external surface, with the 

 exception of a narrow strip along the upper border ; this zone, together with the mesial surface 

 of the lobe, is supplied by the anterior cerebral artery. The occipital lobe is supplied e.xclusively 

 by the posterior cerebral artery. The temporal lobe is supplied by the middle cerebral artery 

 over its superior and the upper half of the middle temporal convolution with the tip of the lobe ; 

 the remainder of the lobe receives the branches of the posterior cerebral. 



The limbic lobe shares in the distribution of the anterior and posterior cerebral arteries, the 

 district of the former including the gyrus callosum to the vicinity of the isthmus, whilst that 

 of the posterior cerebral includes the remainder of the lobe. 



The veins returning the blood from the brain are all tributaries of the dural 

 sinuses, and they therefore only to a Hmited degree follow the course of the cerebral 

 arteries. They are further distinguished by the absence of valves. The superior 

 cerebral veins, after emerging from the surface of the brain, course within the pia 

 over the convex aspect of the hemisphere and proceed, for the most part, towards 

 the superior longitudinal sinus into which they open, either directly or through the 

 lacunae laterales, by from 12-15 trunks. The veins draining the structures situated 

 around the lateral and third ventricles are tributary to the paired lesser veins of Galen, 

 which run backward within the velum interpositum and, emerging below the splenium, 

 unite to form the great vein of Galen. This vessel joins with the inferior longitudinal 

 sinus to form the straight sinus, which is lodged in the line of juncture between the 

 falx cerebri and the tentorium cerebelli. 



PRACTICAL CONSIDERATIONS : THE BRAIN AND ITS 



MEMBRANES. 



Congenital Errors of Development. — Various defects of development of the 

 brain and its membranes are not uncommon. The brain may be absent {anen- 

 cephahis), it may escape from the skull {exencephalus) , the brain, membranes and 

 vessels may be only rudimentary {pseudencephalus), or there may be arrest of 

 development in any limited portion (^porencephaliis — a name more suitably applied 

 when there is a marked depression in the surface of the brain). The brain as a whole 

 may be defective (microcephalus) , or it may be abnormally large {macrocephalus) . 



