THE MENINGES. 23 



the inner surface of the dura, with the formation of one or more hemorrhagic mem- 

 branous layers. Adhesions to the pia do not occur. The disease has been seen in 

 purpuric and infectious diseases, as well as in alcoholic and demented individuals. 



Dural Hemorrhage. Hemorrhage arising from injury to the dura through 

 fracture of the skull has already been discussed (see page 18). Epidural hemorrhage 

 may, however, occur from an injury to the skull and detach the membrane from 

 the bone without a fracture being present. The possibility of this occurring is proved 

 by the remarkable case reported by Dr. J. S. Horsley {New. York Med. Jozir., Feb. 

 9, 1901). A man was struck on the head with a wooden club. He was momen- 

 tarily stunned, but soon recovered and felt perfectly well. An hour and a half later he 

 became drowsy, and in a few hours was in a state of stupor. The right side of the 

 body and face was paralyzed, and the left arm and leg were in constant jerking con- 

 vulsions. He was trephined over the left parietal eminence and four to six ounces 

 of blood clot removed. There was no evidence of fracture or wound of the dura. 

 Recovery was prompt. There have also been other recorded cases. 



In operations involving the separation of the dura from the bone, bleeding may 

 be quite free. This comes from rupture of the veins passing from the bone to the 

 dura, and sometimes from the rupture of a vein passing over or in the dura itself. 



Subdural hemorrhages always originate from the pia mater. 



Inflammation of the Pia Mater; Meningitis. This, when not of a tuber- 

 culous character is called leptomeningitis. It is commonly known as inflammation of 

 the brain, or meningitis. The pia mater of the brain being directly continuous with 

 that of the spinal cord, inflammations of the former extend to and involve the latter in 

 about one-third of the cases. The disease is then called cerebrospinal meningitis. 



Infection is the usual cause of leptomeningitis. Direct injury to the membranes 

 and their bony envelopes may cause it, but it occurs usually through some secondary 

 avenue of infection. Thus, it may follow fractures opening into the mouth, nose, 

 the various accessory bony sinuses, ear, etc. The infection may, however, not be 

 traumatic, but occur through the blood, following or accompanying the various 

 infectious diseases. Owing to the fact of the pia lying on the brain substance, and 

 its vessels with their perivascular sheaths penetrating it, the disease naturally tends 

 to involve the brain, if it is very severe or long standing. If such is the case, the 

 affection is called cerebritis or encephalitis. 



The inflammation may be serous, plastic, or even purulent. The pia mater being 

 continuous with the choroid plexuses, the ventricles may be dilated by the increased 

 fluid. The infection may follow the vessels into the brain and produce brain abscess. 

 The effusion being often localized at the base of the brain interferes with the functions 

 of the cerebral nerves. The first, or olfactory, is comparatively rarely affected. The 

 optic, or second, is more often so, producing intolerance of light. There may be 

 choked disk, and I have even seen a case in which there was total blindness without 

 any change being visible in the nerve by means of ophthalmoscopy. In this case 

 atrophy of the disk soon followed. The third, or motor oculi, according to Church 

 and Peterson, is almost always affected. This would be shown by strabismus, diplopia, 

 and changes in the pupil. Facial paralysis, from implication of the seventh nerve, is 

 sometimes seen, and the auditory, or eighth, may also be affected. Involvement of 

 the hypoglossal or twelfth nerve, will be shown by deviation of the tongue. The 

 origin of the cranial nerves from the base of the brain is shown in Fig. 28. 



Tuberculous Meningitis. In this form of meningitis the infection comes through 

 the blood, and the tuberculous lesions follow the vessels. They are most marked on 

 the base of the brain, involving the circle of Willis and the Sylvian fissure. The 

 infection follows the vessels of the pia mater through the transverse fissure into the 

 ventricles. The effusion accumulating in the ventricles has given rise to the name 

 acute hydrocephalus. It also follows the perivascular sheaths of the smaller vessels 

 into the brain substance, producing a cerebritis; thus it is seen how a knowledge of 

 the circulation of the brain explains the location of the lesions. 



The exudate involving the nerves of the base of the brain produces correspond- 

 ing symptoms by interfering with their function. 



Pial Hemorrhage. Meningeal hemorrhage may be either subarachnoid or 

 subdural. If the hemorrhage has not been violent, it spreads out under the arach- 



