THE MIDDLE CEREBRAL ARTERY. 723 



3. The pracumal is a considerable vessel lying more or less in PnecuueaL 

 the calloso-marginal sulcus and distributed to the para-central 



and praecuneate convolutions as well as to the upper part of the 

 callosal. 



4. The artery of the carpus callosum is a small vessel directed Artery of 

 backwards in the callosal sulcus, and distributed to the corpus 



callosum and the lower part of the callosal convolutions. 



c. The MIDDLE CEREBRAL ARTERY (fig. 257, 4, and fig. 259) is the 

 largest branch of the carotid, and ramifies over the outer surface of the artery : 

 hemisphere. Entering the fissure of Sylvius, it divides into four or 

 five large cortical branches, which issue therefrom and supply the cortical 

 whole of the parietal lobe, together with the neighbouring parts of 

 the frontal and temporal lobes. 



As the vessel enters the fissure of Sylvius it gives off the antero- and central 

 lateral set of central arteries, which are the largest of their kind and 

 pass upwards through the anterior perforated area to the central Autero- 

 nuclei, supplying chiefly the lenticular and caudate nuclei of the set. 

 corpus striatum and the intervening white matter of the internal 

 capsule. 



The origin of the cortical branches will be seen by opening out Cortical 

 the fissure of Sylvius, as in fig. 259, and they are named as ar? 110 

 follows : 



1. External orbital. 



2. Inferior external frontal. 



3. Ascending frontal. 



4. Ascending parietal. 



5. Parieto-temporal. 



6. Temporal. 



1. The external orbital is distributed to the outer part of the under, external 

 or orbital, surface of the frontal lobe. 



2. The inferior external frontal are two or three small branches inferior 

 which pass to the lower part of the outer surface of the frontal fjjjjaf 1 

 lobe. 



3. The ascending-frontal is a considerable vessel lying more or less ascending 

 in the pre-central sulcus and distributed to the adjoining parts of fr< ltal * 

 the cortex. 



4. The ascending-parietal branch, like the foregoing, passes ascending 

 upwards ; it is partially received into the post central sulcus, and is pan 

 distributed to the cortex in its neighbourhood. 



5. The parieto-temporal are, usually, two large terminal vessels from parieto- 

 the middle cerebral which emerge from the back part of the Sylvian an 1 * 01 * 1 ' 

 fissure to pass to the outer surface of the back part of the parietal, 



the front of the occipital, and the contiguous portions of the temporal 

 convolutions. 



6. The temporal branches are two or three in number : they temporal. 

 emerge from the lower part of the Sylvian to the anterior part of 



the temporal lobe, and to the whole of its outer surface as far back 

 as the preceding vessels. 



On comparing figs. 258 and 259, it will thus be seen that the 



3 A2 



