166 CLINICAL APPLIED ANATOMY. 



relation to the sensory portion of the capsule has just been 

 indicated. Branches derived from the posterior cerebral artery 

 help to supply the outer part of the thalamus, and these may 

 give rise to bleeding which also causes pressure on the sensory 

 part of the capsule, and may extend either towards the third 

 ventricle or downwards into the crus. The posterior cerebral 

 and posterior communicating arteries supply branches to the 

 ventricular portions of the optic thalamus, and haemorrhage from 

 these may easily break into the ventricles. (Fig. 10, p. 165.) 



A large haemorrhage in the white matter of the hemisphere 

 has usually spread into it from the corpus striatum. When 

 primary haemorrhages occur in the white matter they are usually 

 small and of oval outline, being compressed into this form by the 

 general direction of the nerve fibres among which they lie. 

 Branches of the calcarine arteries from the posterior cerebral 

 trunk are the sources of haemorrhages in the white matter of the 

 occipital lobe close to the visual centre. 



Large haemorrhages in the hemispheres tend to burst into the 

 ventricular cavities rather than on the surface. They travel in 

 the direction of least resistance. Having gained access to the 

 lateral ventricle the blood passes from one cavity to another 

 through the natural communications, and may ultimately reach 

 the fourth ventricle and exercise pressure on the important 

 bulbar nuclei or induce glycosuria. Blood from the ventricles 

 may appear outside the brain by traversing the transverse or the 

 choroidal fissures, or may burst through the floor of the third 

 ventricle, or in some cases invade the pituitary body. The blood 

 when it appears on the brain surface infiltrates the subarachnoid 

 space and may form a thin coating over the cerebellum and other 

 parts. 



Branches of the posterior cerebral trunk and of the posterior 

 communicating artery supply the crus, but are seldom responsible 

 for primary haemorrhage into its substance. -The crus may also 

 be infiltrated from above by a haemorrhage which has ploughed 

 up the basal ganglia or from below by a haemorrhage extending 

 from the pons. Crossed paralysis or alternate hemiplegia 



