In numerous other cases purely local troubles so undermine the vessel's strength that it ruptures. The writer has shown this for foci of softening; these erode and weaken the wall of some vessel in the involved area; then, of course, rupture easily results. Em bolism also, and in like manner, some times occasions an early break at the point of plugging. Then tumors not rarely so weaken and drag on the local vessels that small and large liwnior rh ages result.
There is no conclusive evidence that either increased blood-pressure or nerv ous influences are ever of themselves suf ficient to rupture a brain-artery, without pre-existing degenerative changes in the vessel-Ivan.
Though any part of the brain may be the site, there are certain favorite start ing-points. These correspond to the territory of the terminal arteries, viz.: the pre- and post- perforating and the branches from the basilar entering the pons. Statistics regarding site have been collected in this country by Dana.
Seventy-seven personal cases appar ently confirming Dana's views. Longe.t.
duration since attack had been twenty two years. E. D. Fisher (N. Y. Med.
Jour., Jan. 5, '95).
Four ea .ses of trauniatic cerebral hamiorrhage, in all of which the vessel ruptured was the middle meningeal. In oue case, a man aged 75, operation re sulted in perfect recovery. Rasing (Hospitalstidende, No. 3, '93); Little wood (London Lancet, Feb. 17, '94).
2. As to the blood thrown out. There is less resistance to the outflow in the gray than in the white matter. It may vary in quantity from minute capillary extravasations up to those of several ounces. Some coagulation soon takes place in the extravasated blood; but be fore this has occurred the blood—if, e.g., it has found a way into the cavities or meninges—may have scattered widely in these spaces and have even passed over in part to the other side. Where, how ever, it has not broken throucrh, but been retained in one focus, it remains long enough and sufficiently fluid to work its way into all accessible inter stices. This is assisted, so long as the flow continues, by the pressure of the blood in the ruptured vessel. As a con sequence, the focus is always irregular and ragged in shape. Much also de pends on the surrounding structures; if these are stratified tracts the blood naturally makes a long pocket; if, how ever, these are soft tissues or matted fibres, then a more globular focus re sults.
The free fluid and granular material is gradually absorbed, leaving the char acteristic brownish pigment and some times pultaceous material that long re mains like a cyst.
Experimental studies to determine the age of li.Tmorrhagie extravasations. 1-hemorrhage artificially induced in rab bits through a trephine-opening. Ani mals lived from one to seventy-two day,;. Certain changes in cellular metamor phosis and in chemical character found to occur with marked constancy. Alost marked changes corresponded with the first, second, fifth, sixth, eighteenth, twentieth, and forty-fifth (lays. Memo siderin is the chemical medium through which the ag;e of the lnemorrha2-it extrav asation may be approximated. Herman Durek (Review of Insanity and Nerv. Dis., June, 94).
3. Changes of nerve-tissue, caused or provoked by the hmorrhage. The pri mary effects consist of tearing and com pression of the surrounding substance. The fibres and gray matter may be forced apart, but often they are ground up, disintegrated, and mixed with the blood, making a pulp into which pro ject abundant iragments of severed tracts. Where fibres are simply forced apart, there may be scarcely any of this chowdering, the compression of adjacent tissues being then all the greater. In limited effusions the compression is ex erted chiefly on the immediate neig,,h borhood; but, where the volume is considerable, it may affect the whole brain, as is shown by the vomiting, coma, etc.
Nerve-fibres once severed do not, so far as we know, ever reunite; conse quently loss of function due to this cause must be permanent. On the other hand, fibres whose function is disturbed by compression or cedema may yet regain their usefulness, and to this is due the degree of recovery that we often see. For on this acute stage there follows one of reaction. It is largely due to the ac companying infiltration and inflamma tory- cedema of adjacent parts that so many cases end fatally in from two to ten days. Even where life is retained this reaction still further jeopards neigh boring structures and diminishes the ex tent of eventful recovery.