814 THE NERVOUS SYSTEM. 



a Walleriaii degeneration. The lesion is confined wholly to the sensory 

 fibres, the motor fibres remaining intact. It is usually most pronounced 

 in the smaller peripheral branches of the nerves. Degeneration of the 

 optic nerve so-called optic neuritis occurs in from ten to twenty per 

 cent of cases. The same condition is less frequent, but occurs in the 

 auditory and in the sensory fibres of the pneuinogastric, glosso-pharyngeal, 

 and trigeiniuus. 



2. The Cell Bodies. Marked degenerative changes in the cells of the 

 spinal and analogous cranial ganglia have been described. In a number 

 of cases they have been found early in the disease. There is a reduction 

 both in number and in size of the ganglion cells, with a replacement 

 connective-tissue hyperplasia. Chromatolysis with nuclear eccentricity 

 as demonstrated by the method of Xissl has also been observed. Similar 

 changes have been noted in the nerve cells of the retina. ' 



3. The Central Processes. () The sensory nerve roots, consisting as 

 they do of the central processes of the spinal ganglion cells, show more 

 or less complete degeneration. It is, in fact, in this part of the neurone 

 that the earliest and most conspicuous changes are usually found. The 

 extent and location of the degeneration vary. In the more common 

 type of the disease lumbar tabes the earliest lesions appear in the 

 posterior roots of the lumbar nerves. Only a few of the roots are at first 

 affected and only some of the fibres in these roots. With the progress 

 of the disease more fibres are involved and the degeneration extends 

 downward to the sacral roots and upward to those of the dorsal and cer- 

 vical nerves. In specimens stained by Weigert's method (see page 

 838) the contrast between the darkly stained anterior root fibres and the 

 almost unstained posterior root fibres is often marked. 



(6) The spinal cord. On removing the cord in a case of advanced 

 tabes, certain changes are usually apparent to the naked eye. The pia 

 mater between the two posterior horns is apt to be thickened, of a dull 

 appearance, and adherent to the cord. This, in contrast to the normal 

 condition of the rest of the pia, gives the effect of a narrow band ex- 

 tending the length of the cord. The posterior columns may be depressed, 

 of a grayish color, and firmer than the rest of the cord. On section the 

 contrast between the posterior columns and the rest of the white matter 

 of the cord is often very distinct. In cords removed from cases dying 

 during the earlier stages of the disease there are often no macroscopic 

 lesions. 



The microscopic appearances vary, depending on the stage, extent, 

 and location of the lesion (Fig. 532). 



In a case which comes to autopsy early in the disease the appearance 

 of the lesion differs from that in a case of advanced tabes. As already 

 noted, the most marked changes are in the posterior columns. In the 

 more common type of the disease in which the degeneration begins in 



1 In Plate XIII., 7, is seen a portion of a spinal ganglion from a case of advanced 

 tabes. In addition to a degeneration of the cells present, there was a marked reduction 

 in the number of cells in the ganglion. 



