216 DISEASES OF THE BRAIN. 



chapter we treat of the lesion of the brain characterized by rupture of 

 the blood-vessels and escape of their contents, whether it induces the 

 symptoms of sudden paralysis of the brain or not. 



ETIOLOGY. Cerebral haemorrhages almost always occur from the 

 smaller arteries or the capillaries of the brain, and are caused partly 

 by structural disease of the arterial walls, partly by an anomalous con- 

 dition of the part of brain surrounding the vessels, partly by increased 

 pressure of the blood against the wall of the vessel. The bleeding 

 most frequently occurs when several of the factors act together. 1 



The structural changes in the walls of the vessels, to which their 

 abnormal fragility is due in most cases, are the results of endarteritis 

 deformans, which was treated of in the first volume. This explains 

 the frequency of apoplexy in persons over forty years of age, which 

 was noticed even by Hippocrates. Next to this, simple fatty degen- 

 eration of the arterial walls, not dependent on inflammation, but occur- 

 ring in badly-nourished cachectic and chlorotic persons, also induces 

 greater fragility and ruptures of the cerebral vessels. Still we must 

 say that fatty degeneration of the finer cerebral arteries is found far 

 more frequently than would be expected from the proportionately rare 

 occurrence of apoplexy. Occasionally rupture of the entire arterial wall 

 is preceded by rupture of the inner and middle coats, while the adven- 

 titia still resist. In such cases the blood escapes between the external 

 and middle coats, and small dissecting aneurisms are formed. Lastly, 

 there are cases where abnormal weakness of the cerebral vessels must 

 be supposed, although it cannot be proved. These are the rare cases 

 where cerebral haemorrhages are found in convalescents from typhus 

 and other acute infectious diseases and during scorbutus. 



We have already mentioned that, in necrotic softening of the 

 brain, capillary haemorrhages not unfrequently occur along the borders 

 of the softened part. Frequently, gradual atrophy of the brain causes 

 dilatation and final rupture of the vessels. While the brain-substance 

 disappears, a vacuum cannot form in the skull ; hence increase of the 

 cerebro-spinal fluid and dilatation of the vessels are necessary results 

 of senile or any other form of atrophy of the brain, which is a frequent 

 sequel of the most varied forms of disturbance of nutrition. Perhaps 

 the frequency of apoplexy in advanced age depends at least partly OP 

 this circumstance, and there is no doubt that the atrophy of the brain, 

 which is in many cases caused by the first apoplectic attack, has some- 

 thing to do with the frequent recurrence of apoplexy. 



The increased pressure of the blood on the walls of the vessels, by 

 which the latter are ruptured, may depend on any of the causes which 

 wo indicated in the first and second chapters as causes of hyperaemia. 

 The frequent occurrence of apoplexy during long and luxurious meals 



