230 DISEASES OF THE BRAIN. 



provement is due to the favorable influence of the baths on the inflam- 

 mation about the clot, and on that portion of the paralysis due to it. 



Lastly, it cannot be denied that paralyses are generally improved 

 by the employment of the induced current of electricity. This is doubt- 

 less solely because " faradisation localised " is one of the most powerful 

 means of therapeutic gymnastics. After paralysis has lasted some 

 time, its degree almost always depends partly on diminished excita- 

 bility of the nerves, and on commencing atrophy of the muscles from 

 long disuse. For both of these states the methodical excitement of 

 the nerves by the induced current is certainly the best remedy, and, 

 at all events, it deserves the preference to irritating liniments, salves, 

 and tinctures. 



CHAPTER VI. 



HAEMORRHAGES OF THE CEREBRAL MEMBRANES APOPLEXIA MENIN- 



GEA H^EMATOMA OF THE DURA MATER. 



ETIOLOGY. Excepting traumatic haemorrhages of the meninges, 

 among which are to be classed those occurring during birth, this is a 

 rare affection. Effusions of blood in the subarachnoid space, or be- 

 tween the dura mater and arachnoid, result mostly from the breaking 

 through of a cerebral haemorrhage. Occasionally, ruptures of aneu- 

 risms, or of degenerated arteries, cause the meningeal bleeding; in 

 other cases, the cause cannot be found. 



The extensive capsulated collections of blood occasionally found, 

 on autopsy, on the under surface of the dura mater, are not, according 

 to Virchow's instructive examinations, as was formerly supposed, 

 simple extravasations of blood, at whose periphery the fibrin has been 

 precipitated and the fluid part capsulated, but they are the remains 

 of chronic inflammations of the dura mater (pachy meningitis), with 

 haemorrhagic exudations. Virchow calls this blood-sac haematoma of 

 the dura mater. The blood filling it comes from the numerous large 

 and thick-walled capillaries that have formed in the pseudo-membrane 

 of the dura mater during this variety of chronic inflammation, and it 

 has been effused between the layers of the pseudo-membrane. The 

 causes of chronic pachymeningitis, with haemorrhagic exudation, are 

 not perfectly known. The disease occurs chiefly in old age, and re- 

 markably often in persons with mental disease, and in drunkards. It 

 appears to develop sometimes as an independent, sometimes as a sec- 

 ondary disease, due to injuries of the brow. In the latter case it is 

 said that years may intervene between the injury and the first symp 

 terns of haematoma ( G-riesinger). 



ANATOMICAL APPEARANCES. If the blood be effused hi the sub 



