296 DISEASES OF THE SPINAL MARROW AND ITS MEMBRANES. 



haemorrhage and oedema, as already described) as results or fbrnjs of 

 myelitis until we shall have learned some other mode of origin for 

 them, as we have for the analogous changes in the brain. 



ETIOLOGY. Myelitis induces the same structural changes as en- 

 cephalitis does. In it there is no abundant interstitial exudation, but 

 the nerve-elements undergo inflammatory disturbances of nutrition, and 

 finally break down, just as the ganglion-cells and nerve-filaments of 

 the brain do in encephalitis. 



Apart from the cases due to propagation of inflammation from the 

 vertebrae to the medulla, myelitis must be regarded as a rare disease. 

 But this extension occurs quite frequently. Most paraplegias which 

 come on during vertebral disease are not results of the curvature of 

 the spine, but of inflammation extending from the vertebrae to the 

 membranes, and thence to the medulla. This view is supported by 

 the fact that in vertebral disease there is frequently paralysis before 

 the spine is curved, and, on the other hand, great curvature often exists 

 for years without symptoms of paralysis, till these at last accompany 

 the deformity without any increase of the curvature, but usually after 

 j.ain in the back. More rarely, wounds and contusions of the spinal 

 column, or the development of syphilitic exostoses, induce myelitis. 

 Occasionally the disease develops about neoplasia and extravasations 

 of blood. Lastly, sexual excesses, excessive straining, catching cold, 

 suppression of the perspiration of the feet, etc., are given as causes of 

 myelitis. We do not know whether in such cases the disease is 

 really due to these causes or to other unknown influences. Patients 

 with paraplegia, besides their other misfortunes, are usually subjected 

 to the unfounded suspicion that they have brought on their disease by 

 dissolute habits. 



ANATOMICAL APPEARANCES. Myelitis is sometimes confined to 

 circumscribed spots, and then, usually starting from the gray sub- 

 stance, it attacks the whole thickness of the medulla ; sometimes, as 

 " central softening," it extends widely through the gray substance, and 

 then affects the white substance but little. 



In the circumscribed spots we find the spinal medulla swollen in 

 recent cases. If we cut into it, a more or less consistent red pulp (red 

 softening) rises above the cut surface. In older cases, the color of 

 the pulpy soft spot becomes more brown or yellow (yellow softening), 

 from change of the haematin and fatty degeneration of the broken-down 

 nerve-elements. Far more rarely than in the brain, the inflamed spot 

 in the spinal medulla is converted into an abscess by the extensive 

 formation of pus-cells. The inflammation in the meninges usually ex- 

 tends beyond that of the medulla. From disintegration and reab- 

 sorpt : on of the disintegrated elements in circumscribed myelitis a 



