THE NERVOUS SYSTEM. 829 



Chronic Interstitial Myelitis. Under this heading are embraced a 

 variety of lesions which probably differ from one another somewhat 

 in the nature of the changes involved, but more in the seat of the dis- 

 ease. We shall consider without special classification the most impor- 

 tant forms. 



Chronic Transverse Myelitis. In certain cases of pressure on the spinal 

 cord from a tumor or from displacement of the bones of the vertebral 

 column, etc., instead of becoming softened or undergoing acute inflam- 

 matory changes, the cord becomes the seat of a localized formation of 

 new connective tissue, with consecutive atrophy of more or less of the 

 nerve elements in the gray and white matter. The cord becomes in this 

 way harder, and sometimes shrunken at the seat of lesion, and gray in 

 color. This change may be followed by ascending and descending de- 

 generation. 



Chronic Disseminated Myelitis Multiple Sclerosis. This lesion, similar 

 in its nature to multiple sclerosis of the brain, often occurs with it. It 

 consists in the formation, in more or less numerous scattered, circum- 

 scribed areas, of new connective tissue, apparently derived from the neu- 

 roglia. The formation of new connective tissue is preceded or accom- 



FIG. 543. MULTIPLE SCLEROSIS IN THE SPINAL CORD. 



Showing irregular areas in which there are atrophy of the nerve fibres and their replacement by connective 



tissue. 



panied by degeneration and atrophy of the nerve fibres and ganglion 

 cells. The new connective tissue consists of the characteristic branching 

 ueuroglia cells, surrounded by a more or less dense network of fine 

 fibrillae, many if not most of which seem to be branches of the neuroglia 

 cells. Corpora amylacea and sometimes fat droplets, either free or con- 

 tained in cells, may be present in the sclerosed areas. 



must be revealed by microscopical study, because our technical procedures in the study 

 of the brain, even in normal conditions, are still in many respects quite unsatisfactory 

 and incomplete. The brain tissue is so delicate and so liable to post-mortem changes, 

 and the effects of different preservative agents are so liable to variations, that great 

 caution is necessary in arriving at conclusions regarding the more minute lesions affect- 

 ing the nerve tissue of the brain. 



