532 S. WALTER R ANSON 



that a part of the iion-medullated fibers in the tract of the cat 

 and other animals in which this lateral expansion is not so well 

 develoi)ed, were also of endogenous origin. 



The present investigation was begun with a three-fold object: 



1. To determine what proportion of each of the two kinds of 

 fibers in the tract are of endogenous origin. 



2. To trace by the method of degeneration the course in the 

 cord of the non-medullated fibers of the dorsal roots, and to find 

 where these fibers terminate. 



3. To determine whether or not any of the non-medullated 

 fibers of the dorsal roots are efferent, i.e., arise from cells in the 

 spinal cord. 



TECHNIQUE 



In this investigation cats were used because the normal struc- 

 ture of the dorsal roots and tract of Lissauer has been most care- 

 fully studied in this animal. Furthermore, the spinal cord of 

 the cat Was known to react in a uniform and favorable manner 

 to the pyridine-silver stain which was to be employed in prepar- 

 ing the material. 



Nine adult cats and one half-grown kitten were used, besides 

 those in which for various reasons the operation was unsuc- 

 cessful. A laminectomy was performed and the dura exposed 

 over the sixth and seventh lumbar and first sacral roots (under 

 the sixth and seventh lumbar spinous processes). In the first 

 three operations the exposed roots (both ventral and dorsal on 

 one side) were ligated proximally to the ganglion without open- 

 ing the dura. Strong braided silk was tied very tightly about 

 the roots in such a way as to insure a complete degeneration. In 

 the other seven the roots (both ventral and dorsal on one side in 

 the exposed area) were cut proximally to the ganglion. In these 

 the dural sheath was of necessity opened by cutting through its 

 prolongations on the roots. 



An interesting phenomenon was the rapid development of shock 

 following the division of the roots. An animal would remain in 

 good condition until this stage of the operation was reached. 

 Immediately after the roots were cut, the animal would show signs 



