534 S. WALTER RANSON 



DEGENERATIVE CHANGES FOLLOWING DIVISION OF THE 

 DORSAL ROOTS 



Twenty-four days after the operation the dorsal roots were in 

 an advanced stage of degeneration. Fragmentation of the axons 

 was complete and most of the resulting debris had been absorbed. 

 The greater part of the degenerated myelin had also disappeared. 

 The degenerated fibers were being transformed into nucleated 

 protoplasmic bands. This was the condition of the roots up to 

 the point at which they entered the cord, or, more exactly, up 

 to the point at which the connective tissue of the root gave place 

 to neuroglia. Levi ('06) has shown that in the lumbo-sacral 

 region this occurs just outside the cord. At this point in the 

 root just outside the cord there was an abrupt change in the 

 stage which the degeneration had reached. In the entering root 

 and in the cuneate fasciculus the degeneration had not pro- 

 gressed so far as in the extra-spinal part of the root, and large 

 irregular fragments of axons were seen in big globules of degen- 

 erated myelin. The difference was due no doubt to the presence 

 of sheath cells on the fibers outside the cord which materially 

 aided in the disintegration and resorption of the fibers. 



Almost all of the fibers in the root as it enters the cord were 

 degenerated. There were, however, in the degenerated roots of 

 Cats I, II, IV, VI and X a varying small number of fine axons of 

 normal appearance, which entered the cord along the same paths 

 as the original non-medullated fibers. Also in Cats III and VII 

 a few fine medullated fibers of normal appearance were seen enter- 

 ing the cord from the degenerated roots. These fibers may either 

 have been efferent dorsal fibers, whose cell bodies were within 

 the cord, or they may have been regensrated fibers growing from 

 the root into the cord. For reasons which will be given in another 

 paragraph I am inclined to regard them as regenerated fibers; 

 nevertheless, these experiments do not enable us to exclude the 

 possibility of the occurrence of efferent fibers in the dorsal roots. 

 But the experiments do show that at least the vast majority of 

 the non-medullated fibers degenerate in the proximal part of a 

 divided dorsal root. This would indicate that their cells of ori- 



