THE NERVOUS SYSTEM. 823 



smaller cells filled with fat granules (Gluge's corpuscles), pus cells, gran- 

 ular matter, neuroglia cells, and sometimes corpora amylacea. The vari- 

 ous combinations of these elements give rise to the different gross ap- 

 pearances which the diseased part presents. In earlier stages of the 



FIG. 536. DEGENERATED TISSUE FROM ACUTE MYELITIS. 



lesion the blood-vessels may be dilated, the nerve fibres and cells swollen ; 

 or the walls of the blood-vessels maybe thickened or fatty, or surrounded 

 by a sheath of leucocytes and cells derived from the connective-tissue 

 cells of the adventitia. 



The lesion is apt to commence in the gray matter or at its edge, and 

 then extend first laterally and afterward upward and downward. 



In a certain number of cases the degenerated material maybe absorbed 

 and a cicatrix or cyst formed. After the least extensive forms of the 

 lesion there may be a restoration of the functions of the cord. 



Secondary degeneration, both ascending and descending, may occur 

 in this form of myelitis, varying in extent according to the size of the 

 primary lesion. The terms central myelitis, peripheral myelitis, and uni- 

 lateral myelitis, are sometimes used to designate localizations of the lesion. 



Poliomyelitis Anterior Myelitis of the Anterior Horn. This name is 

 applied to a group of cases which are characterized by clinical symptoms 

 indicating changes in the anterior horns. The disease is most common 

 in children, under the name of infantile spinal paralysis, but occurs also 

 in adults. It usually begins with symptoms of an acute infectious dis- 

 ease, the paralysis supervening after a few days. It varies in acuteuess, 

 severity, and duration. In many cases there is complete recovery, and 

 then we must suppose that the changes in the nervous tissue were not 

 destructive in character. In other cases the symptoms are more perma- 

 nent, indicating a destructive lesion. 



At first a considerable group of muscles, usually of the arms or legs, 

 is affected. Eesolution taking place, there may be complete disappear- 

 ance of the paralysis. More commonly there is return of function in 

 most of the muscles, while some few remain permanently paralyzed and 

 become atrophied. The lesion is most frequent in the lumbar and cer- 

 vical enlargements, but may occur anywhere, and is often found in scat- 

 tered patches. Earlier autopsies were in cases of long standing, and 

 the changes found consisted in degeneration (Fig. 537), shrinkage, pig- 



