CONDUCTING PATHWAYS IN THE SPINAL CORD 



591 



derangements give us information similar in kind to that obtained from 

 clinical observations (3, &). The resulting degenerations can also be used 

 in the same way as corresponding observations on man (3, a). Finally, after 

 partial section of the cord, one can tell by stimulation of higher parts e. g., 

 the cerebral cortex, whether certain efferent pathways have been interrupted 

 or not. 5. The Electrical Method, which has been worked out especially by 

 Gotch and Horsley. This is based upon the fact that action currents occur 

 in the central nervous system as well as in peripheral nerve trunks. Attention 

 is paid to the strength of the action currents produced by stimulation of 

 different parts after making various partial sections (cf. Fig. 263). 6. Gud- 

 den's Method (cf. page 568). 



C. 



ANATOMICAL DATA CONCERNING THE CONDUCTING PATHWAYS 

 OF THE CORD 



We use the term afferent pathways here and in what follows to designate 

 all those tracts which convey impulses from lower to higher nerve centers, 

 and the term efferent pathways to designate all those which convey impulses 



FIG. 264. A, section through the cervical, and B, through the lumbar parts of the cord, after 

 Edinger. The approximate limits of the various tracts are indicated, la, crossed pyramidal 

 tracts; 1, direct pyramidal tracts; 2, anterior ground bundle; 3, ventrolateral cerebellar tract 

 (or Gowers's tract) ; 4, dorsolateral cerebellar tract (or Flechsig's tract) ; 5, lateral boundary 

 zone of the gray substance; 6, Burdach's column; 7, Goll's column; 8, zone of entrance of pos- 

 terior root fibers ; 9, ventral portion of the posterior column ; 10, border zone. 



from higher to lower nerve centers. To the former we shall add also all the 

 paths which carry over an afferent impulse to an efferent pathway. 



As we have already seen, stimulation of a single afferent nerve may excite 

 reflexly a great many efferent nerves even when the spinal cord is isolated 

 from the brain. The connection of the afferent nerves with the motor cells 

 of efferent nerves must therefore be very complex. This leads us to assume 

 that the afferent pathways in the spinal cord are very much more complicated 

 than the efferent an assumption which is sufficiently borne out by experiment. 



The nerve fibers springing from the nerve cells of the spinal ganglia and 

 entering the spinal cord by the posterior roots for the most part divide imme- 

 diately after their entrance into the cord, into an* ascending and a (short) 



