CHAP, v.] THE SPINAL CORD. 605 



without any regeneration in the divided tracts, recovery has ulti- 

 mately taken place, the return of voluntary power being nearly if 

 not absolutely complete. So also cases have been recorded in which 

 the section of a lateral (say right) half of the lower dorsal cord has 

 led to an impairment of sensibility and voluntary power in the hind 

 legs, most marked on the same side, but in which the impairment 

 has in the course of time completely or nearly completely dis- 

 appeared without any regeneration of the cord taking place, and 

 further in which a second lateral section higher up in the cord, and 

 this time of the other (left) half, has again led to impairment, again 

 to be followed by complete or nearly complete recovery. Gases of 

 this kind, carefully conducted and observed by competent persons, 

 place us in considerable difficulties. If we admit that the imme- 

 diate effects of the operation are largely due to 'shock' and inhibi- 

 tory processes, and that after the lateral section of the right half of 

 the cord, sensory volitional impulses passed to and from the hind 

 legs by the left half, then the recovery from the second operation 

 shews that these impulses must have crossed between the two 

 sections from the left to the right side. From which we might infer 

 that impulses travelling along the cord were continually passing in 

 a zigzag fashion from one lateral half to the other ; and an analo- 

 gous series of experiments in which the anterior and posterior 

 halves were divided at different heights would lead us to infer in 

 addition that the impulses also crossed in a similar zigzag fashion 

 from front to back and back to front. But then the serious 

 question is started, Is this serpentine path the normal one, or an 

 artificial one forced upon the impulses by the abnormal condition 

 of the cord ? Finding their usual path blocked, did they make for 

 themselves new tracts ? But if such alternative passages be pos- 

 sible how can we trust to either experiment or disease to shew us 

 the normal paths, or what right have we to speak of normal paths 

 at all? 



It will be seen from the foregoing that the time is not yet ripe 

 for making any dogmatic statement concerning the conduction of 

 impulses along the cord ; and indeed the controversies concerning 

 it have perhaps acquired a factitious importance. If we might 

 venture to deduce any distinct lesson from all the various conflicting 

 statements and results, it would be that the complexity and per- 

 fection of the nervous mechanisms of the spinal cord itself has been 

 underrated rather than overrated. We spoke at the beginning of 

 this section of a system of relays ; we insisted on the existence of 

 mechanisms with which the anterior and posterior roots were 

 respectively in immediate connection; and the results of experi- 

 ment as well as of pathological experience seem to shew that im- 

 pulses, whether of volition or of sensation, work their way along 

 the cord through a whole series of such and similar mechanisms, 

 rather than through simple direct straightforward tracts of con- 

 tinuous fibres whether in the lateral columns or elsewhere. 



