728 



THE GANGLIONIC CEREBRAL ARTERIES. 



large part of the optic thalami {Charcot). 



a line drawn at a distance of two centi- 

 n JuelouS Sed cle of Willis, encloses the ganglionic area The cerebra convolutions 

 arc sinned by he large branches of the circle of Willis. The anterior cerebral curves round 

 the corpus caTlosum, and supplies the gyrus rectus and the supraorbital, the first and second 

 fontel convolutions the upper part of the ascending frontal, and the inner surface of the 



tafenheto *Zlu M the quadrate lobule (fig. 510, I). The posterior cerebral goes to the 

 Snof the ocdpital lobe and the inferior aspect of the temporal lobe ; the middle cerebral 

 SVvian artery P divides into four branches, which go to the V^^^?*& 



parietal lobes, i.e., chiefly to the 

 motor areas (III), the angular 

 gyrus, and to the first temporo- 

 sphenoidal lobule. The terminal 

 branches of these ganglionic 

 arteries do not anastomose with 

 the cortical system. Fig. 511 

 shows the ganglionic arteries 

 piercing the basal ganglia. Ob- 

 viously, when haemorrhage of 

 the lenticulo-striate artery or 

 "artery of hemorrhage " (4, 4) 

 occurs, it will compress the len- 

 ticular nucleus, or tear it up, and 

 may even injure the parts out- 

 side, such as the external cap- 

 sule, claustrum (T), and island 

 of Reil (R), or those inside, e.g., 

 the internal capsule.] 



[Thus, the anterior cerebral 

 supplies the prefrontal area and 

 a small part of the motor area, 

 that for the leg-centre in the 

 paracentral lobule and upper end 

 of the ascending frontal (and 

 perhaps that for the trunk). The 

 posterior cerebral supplies the 

 centre for vision, and that con- 

 nected with the course of the 

 posterior part of the optic ex- 

 pansion, and also the sensory 

 part of the internal capsule. The 

 , , , ... , . ' . , .. ~ r, . middle cerebral supplies the 



Arteries of the base of the brain, or circle of Willis. C, C, in- motor areas of the cortex , except 

 tcrnal carotids; C A, anterior cerebral ; S, S, Sylvian arteries; t of the i e g. cen t re and the 

 V, V, vertebrals; B, basilar; CP, posterior cerebrals ; 1, 2, gasal ganglia, the auditory centre, 

 3, 3, 4, 4, groups of nutrient arteries. The dotted line shows an( j that for speech.] 

 the limit of the ganglionic area. rrhe core bral circulation has 



many peculiarities. The curves on the arteries serve to modify the effect of the cardiac shock, 

 the circle of Willis permits within limits a free circulation ; but, in as far as the skull is largely 

 a rigid box, it was at one time taught that, as the brain substanee and its fluids were prac- 

 tically incompressible, it was impossible to alter the amount of blood in the brain. This is a 

 mistake. The amount of blood undergoes an alteration in this -way, that when more blood 

 passes in, some cerebro-spinal fluid moves out, and vice versd, so that there is an intimate relation 

 between these fluids. In the developing skull, the cerebro-spinal fluid may accumulate in large 

 amount within the ventricles, and greatly distend both them and the yielding skull-case from 

 internal pressure, as in acute hydrocephalus. The peculiarities and independence of the cortical 

 and ganglionic arteries have already been referred to. Plugging by means of a clot, vegetation, 

 or wart, carried from the heart, is common in the left middle cerebral artery. Why ? When 

 the plug is washed away by the blood-stream, owing to the left carotid springing from the aorta 

 nearly in line with the blood-current, the plug readily passes into the carotid and so into the 

 left middle cerebral which is in line with the internal carotid. In such a case, the convolutions 

 and parts supplied by it are suddenly deprived of blood with immediate and serious results.] 



[The venous circulation is peculiar. The sinuses are really spaces between the layers of the 

 tough dura mater, and partly bounded by bone. The blood moves in the longitudinal sinus 

 from before backwards, but most of the cortical veins open into it in a forward direction, so 

 that their stream is opposed to that in the sinus. Thus, the blood which enters the brain by 

 ascending arteries reaches the sinuses by ascending veins, the reverse of what obtains elsewhere, 



