PROGRESSIVE SPINAL MUSCULAR ATROPHY. 435 



primary degeneration affecting the lateral columns, especially 

 the pyramidal tracts. The changes usually begin in the 

 lumbar cord, and are bilateral. The chief clinical character- 

 istics are paralysis, muscular spasms, and exaggerated muscle- 

 reflexes ; the first being of course readily accounted for, and 

 the two latter, in part at least, may be referred to the absence 

 of the control exercised by the higher centres upon those in 

 the cord, and transmitted normally through the tracts now 

 degenerated. 



In some cases, to which the term amyotrophic lateral 

 sclerosis has been applied, the anterior cornua of gray matter 

 are also involved, adding muscular atrophy to the symptoms 

 already present (Figs. 206 and 207). 



FIG. 207. 



The same as previous figure, except that the section is of the seventh to eight dorsal 

 segments. The pyramidal tracts are sclerosed,and there is considerable degen- 

 eration in the intermedio-lateral tract (F. W. Mott). 



Progressive spinal muscular atrophy (chronic anterior polio- 

 myelitis) is characterized by a gradual atrophy of the large 

 ganglion-cells of the anterior cornua ; and clinically by pro- 

 gressive atrophy and consequent paralysis of the muscular 

 system commonly being first manifest in the hand. Though 

 the degenerative changes affect mainly the ganglion-cells of 

 the anterior cornua., the motor fibres arising from them, and 



