810 THE NERVOUS SYSTEM. 



cussatiou a somewhat different picture is presented. In a complete trans- 

 verse lesion there is degeneration of both crossed and of both direct pyr- 

 amidal tracts. If the lesion is unilateral the degenerations are upon the 

 same side as the lesion. The areas of degeneration are also larger and 

 less sharply defined than in cerebral lesions. Then in addition to the 

 degeneration of the pyramidal tracts there is a degeneration of a con- 

 siderable number of fibres in a crescent-shaped area lying near the periph- 

 ery of the autero -lateral region and extending from the crossed to the 



FIG. 530. -SECONDARY ASCENDING DEGENERATION. 



Following complete crushing of the cord about two segments below the level at which the section was 

 taken. Degeneration is almost complete in the columns of Goll, of Gowers, and in the direct cerebellar 

 tracts. A few normal fibres are seen in the columns of Burdach. These are the ascending axones of spinal 

 ganglion cells between the point of injury and the level of the section, and are seen to occupy that part of 

 the posterior columns adjacent to the posterior horns. 



direct tract. Degeneration of these fibres has been described by Marchi ' 

 after removal of the cerebellum. He considers them descending cere- 

 bellar fibres. The so-called comma-shaped degeneration in the posterior 

 columns is sometimes present. Schultze 2 regards these fibres which 

 are situated about the middle of the posterior columns, as descending 

 axones of spinal ganglion cells. Tooth 3 thinks that they are more prob- 

 ably descending branches of commissural neurones. In the fundamental 

 columns the degeneration extends but a short distance below the seat of 

 injury, and of course affects only those axoues which descend. 



ASCENDING DEGENERATION. Any lesion which destroys the spinal 

 ganglion cells or which interrupts their axones determines a secondary 

 ascending degeneration in the posterior columns (Fig. 530). Any lesion 



l MarcJii, "Origine e decoroso dei peduncoli cerebellari. " Rev. Sper. de Fren. e 

 Med. eleg., Bd. xvii.. p. 367. 



8 Schultze, "On Comma-shaped Degeneration of the Posterior Columns." Arch. f. 

 Psych., 1883. 



3 Tooth, " Goulstonian Lectures on Secondary Degeneration of the Spinal Cord," Lon- 

 don, 1889. 



