THE NERVOUS SYSTEM. 785 



of brain tissue, more or less fatty, may be absorbed. In this way the 

 part heals, leaving a more or less pignieuted cicatrix. The healing is in 

 most cases very slow and may occupy months or even years. The pia 

 mater may participate to a marked degree in the inflammatory healing 

 process. Abscesses may form near the seat of injury. 



After wounds which involve the removal of portions of the cranial 

 bones, it is not uncommon after a few days to see a bleeding fungous 

 mass project through the opening. This mass, sometimes wrongly called 

 hernia cerebri, consists of degenerated brain tissue, blood,, and granula- 

 tion tissue, with more or less pus. The brain tissue below it is degener- 

 ated, soft, broken down, and purulent, and there is often abscess in the 

 adjacent brain tissue. Such wounds may finally heal by the absorption 

 of the broken-down brain tissue and blood, and its substitution by gran- 

 ulation tissue. 



Lacerations of the brain tissue without fracture may appear shortly 

 after the injury as simple more or less circumscribed areas of capillary 

 haemorrhage; the brain tissue about these may degenerate, pus may 

 form, and abscesses be developed ; or the degenerated and lacerated tis- 

 sue may be gradually replaced by granulation tissue which finally forms 

 a cicatrix. The process of degeneration and softening and of healing 

 in such lacerations of brain tissue may occur very slowly indeed, even 

 occupying years, and not infrequently the degenerative changes are very 

 extensive and progressive. In many cases, of course, the injury is so 

 extensive, -or involves such important parts of the organ, that very little 

 or no inflammatory or degenerative change takes place before death. 



INJURIES OF THE CORD. 



The spinal cord may be compressed or lacerated by penetrating 

 wounds, by fracture or dislocation of the vertebrae, or by concussion 

 without injury to the vertebrae. The spinal cord is found simply disin- 

 tegrated, or there may be much haemorrhage and the disintegrated nerve 

 tissue be mixed with blood. If life continue, the nerve elements may 

 degenerate ; Gluge's corpuscles and free fat droplets may form ; blood 

 pigments may be formed; and when inflammation supervenes more or 

 less pus may be intermingled with the degenerated material. There may 

 be marked changes in the minute structure of the cord, witholit any 

 change being evident to the naked eye. 



INJURIES OF THE NERVES. 



The secondary effects of injuries to nerves are described in the sec- 

 tion on degenerations following injury. After amputation of a limb, 

 there often occur swellings of the peripheral ends of the divided nerve 

 trunks. These bulbous ends are called false or amputation neuromata. 

 They are made up almost entirely of fibrous tissue, although nerve fibres 

 have been found in them. 

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