790 THE NERVOUS SYSTEM. 



be more or less tinged with blood. Microscopically, the perivascular 

 spaces are distended with blood, which may have escaped into them ; 

 bhis is associated with more or less broken-down brain tissue. The hem- 

 orrhages may be single, but are frequently multiple, so that the brain 

 tissue is besprinkled with blood points. Degeneration of the extrava- 

 sated blood may give rise in later stages to reddish or brown or yellowish 

 circumscribed discoloration of the brain tissue, due to granules and crys- 

 tals of blood pigment intermingled with broken-down brain tissue, with 

 more or less fatty degeneration of its elements. Capillary haemorrhages 

 may be due to fatty degeneration of the vessels leading to rupture ; or 

 the extravasation may be due to diapedesis, or it may depend upon con- 

 ditions which we do not understand. They frequently occur in the 

 vicinity of apoplectic clots and tumors, they may be due to thrombosis 

 of the veins or of the sinuses of the dura mater ; they not infrequently 

 occur in acute encephalitis, in congestive hyperaemia, in acute mania, 

 and in delirium tremens ; and they may be associated with general dis- 

 eases, such as scurvy, purpura haemorrhagica, typhus fever, pyaemia, 

 ulcerative endocarditis, etc. ; they may be associated with embolic soft- 

 ening. 



Apoplectic foci may result from the coalescence of numerous capillary 

 haemorrhages; from injury, or from rupture of diseased arteries, either 

 with or without changes in the blood pressure. Haemorrhages from in- 

 jury to the skull may occur as well without as with fracture, and may be 

 situated over the vertex as well as at the base of the brain, and vary in 

 extent and seat, depending upon the character and point of the injury 

 and the size of the vessels involved. The so-called spontaneous haemor- 

 rhages, other than those of capillary origin, which give rise to masses of 

 blood and broken-down brain tissue, may vary in size from that of a pea 

 to those occupying a large part of a hemisphere. They are due, in a 

 very considerable proportion of cases, to the rupture of small arterial 

 aneurisms, but may arise from weakening of the walls of the arteries, 

 from arteritis, atheroma, or fatty degeneration. These latter forms of 

 lesions doubtless give rise in most cases to the formation of the aneurisms 

 whose rupture is in so many cases the immediate cause of the haemor- 

 rhage. 



Aneurisms of the cerebral arteries may be as large as a pea or 

 hazelnut, but those most frequently met with and causing apoplexy are 

 usually small called miliary aneurisms and may be microscopic in 

 size, varying from this up to that of a large pin's head or larger. They 

 may be sacculate or fusiform, and frequently exist in considerable num- 

 bers. They may occur in any of the small arteries of the brain, but are 

 said to be most frequent on the branches of the middle cerebral artery. 

 It is asserted that the bursting of miliary aneurisms is the nearly if not 

 quite exclusive cause of the formation of spontaneous apoplectic clots, 

 but this we do not believe to be true. 



As to the immediate cause of rupture, either of aneurisms or other- 

 wise diseased blood-vessels in the brain, we are in many cases entirely 



