434 Anatomy Applied to Medicine and Swgery. 



involves the inferior surface of the cerebellum and presses 

 secondarily on the medulla. Pressure on the internal 

 capsule causes widespread paralysis, since the cortical 

 fibres are here compressed in their passage between the 

 optic thalamus, caudate nucleus and the lenticular nucleus. 

 A glance at the diagram on page 426 will indicate the 

 fibres that would be affected in a lesion in this situation, 

 and the disturbance that would necessarily follow. A 

 small lesion here will cause more extensive distribution 

 than a much larger one involving the cortex of the brain. 



Cerebral Haemorrhage. The arteries that sup- 

 ply the cerebrum are derived from the internal carotid and 

 the vertebral which form the circle of Willis. The mid- 

 dle cerebral, the larger of the two terminal branches of 

 the internal carotid, gives off a number of central arteries. 

 These supply the basal ganglia, i.e., the optic thalamus, 

 the lenticular nucleus, the corpus striatum, and the inter- 

 nal capsule which lies between them. One of these cen- 

 tral arteries the lenticulo-striate supplies the lenticular 

 nucleus and then passes into the internal capsule. This 

 has been called, by Charcot, the artery of "cerebral haemor- 

 rhage," and, since it supplies the internal capsule, it fol- 

 lows that, when ruptured, symptoms indicative of pres- 

 sure on the fibres of the capsule result. The left len- 

 ticulo-striate artery is said to be more often involved than 

 the right. This may be due to the fact that the axis of the 

 left carotid artery with reference to the thoracic aorta, is 

 such, that the current of blood from each systole of the 

 heart is driven more directly into the left carotid than into 

 the innominate or left subclavian, so that greater strain 

 is thrown on the left carotid than on the right. 



These central arteries are terminal, and, when one is 

 plugged, as by an embolus, there is not sufficient collateral 

 circulation established to repair the area damaged by this 

 local withdrawal of the circulation in the vessel. 



