CEEEBEAL HAEMORRHAGE. 165 



of the brain. Haemorrhage may also occur in the centrum ovale, 

 the cortex, the pons, and the medulla. The right and left cerebral 

 hemispheres are equally liable, the vascular arrangements being 

 identical. There are several reasons why the arteries of the 

 central ganglia should rupture more frequently than those of 

 the other parts. The arteries are short and come off directly 

 from the large main stem, they are terminal vessels with no 

 collateral circulation to relieve the pressure in them, and 

 they receive poor support from the surrounding grey matter. 

 The pressure in these central vessels is probably nearly as 

 great as the pressure in the internal carotid at their point 

 of origin. (See Fig. 11, p. 166.) 



The actual starting point of the haemorrhage in the corpus 

 stnatam depends on the vessel which gives way. A clot in the 

 head of the caudate nucleus is derived from the perforating 

 branches of the anterior cerebral artery ; haemorrhage into the 

 middle part of the nucleus comes from the lenticular or lenticulo- 

 striate branches of the middle cerebral artery ; haemorrhages in 

 the posterior part are derived from the lenticulo-optic branches 

 of the same main trunk. The lenticulo-striate artery from the 

 frequency with which it is the source of the bleeding has been 

 called the artery of cerebral haemorrhage. This vessel passes 

 upwards from the anterior perforated spot through the putamen 

 or outer zone of the lenticular nucleus to terminate in the internal 

 capsule and the body of the caudate nucleus. Extravasations of 

 blood from this artery lie immediately outside the motor section 

 of the internal capsule on which they exercise pressure or into which 

 they plough their way, producing hemiplegia. They also tend to 

 separate the putamen from the external capsule since anatomi- 

 cally there is but little adhesion between these two structures. 

 Haemorrhage from the lenticulo-optic branch of the middle 

 cerebral artery is in a position to cause pressure on the posterior 

 or sensory portion of the capsule. (Fig. 10, p. 165, Fig. 12, p. 179.) 



The origin of cerebral haemorrhage may be in the optic 

 thalamus instead of in the corpus striatum. The lenticulo-optic 

 artery may be responsible for haemorrhage here also, and its 



