THE NERVOUS SYSTEM. 819 



volved. Marie lays particular stress upon the arterial systems of the cord as the prime 

 factor in many cases, calling attention to the fact that the lesion, as it is most commonly 

 found, coincides almost exactly with the distribution of the posterior spinal arteries. 

 By others the lesion is ascribed to a multiple sclerosis, the restriction of the degeneration 

 to definite tracts being only apparent. It is possible that in some cases the patho- 

 logical picture of a combined sclerosis may be due to secondary degeneration following 

 myelitis. 



A subacute type of combined system degeneration has been described by Russell. ' 

 The degeneration involved the same tracts affected in the more chronic type, and was 



\ 



FIG. 535. -COMBINED SYSTKM DISEASE. 



Showing: degeneration and sclerosis in the columns of Goll, the direct and the crossed pyramidal tracts, and 

 the direct cerebellar tract. 



often very extensive at some levels of the cords studied, there being only a thin layer 

 of normal fibres covering the gray matter. 



Under the name of diffuse degeneration of the spinal cord, Putnam and Taylor* 

 describe a somewhat similar condition, leaving open the question as to the systemic 

 nature of the process. 



FRIEDREICH'S ATAXIA. (Hereditary Ataxia. ) 



This disease while often referred to as hereditary ataxia, has more of 

 a family than of a distinctly hereditary character. Its pathology is 

 marked by a decrease in the size of the spinal cord, the diameter of which 

 is often not more than three-quarters that of the normal cord. Degeii 

 eration of the columns of Goll is usually quite complete. Less marked 

 degeneration is found in the columns of Burdach, in the direct cerebellar 

 and in the crossed pyramidal tracts. The marginal tract of Lissauer may 

 or may not be affected. In the posterior horns and in the columns of 

 Clarke the condition, resembles that in tabes. There may be atrophy of 

 the cerebellum. 



1 Brain, Spring, 1900, vol. xxiii., No. 89. 



2 Journal of Nerv. and Ment. Disease, January and February, 1901. 



