318 INNERVATION. [CHAP. XI. 



impediments to accurate experiments, and sufficiently explain the 

 discrepancies which are apparent in the results of the various ex- 

 periments which have been published. Moreover, the resultant 

 phenomena, after experiments of this kind, are extremely difficult 

 of interpretation, especially with reference to sensation. " The 

 gradations of sensibility," remarks Dr. Nasse, " are almost imper- 

 ceptible ; the shades are so delicately and so intimately blended, 

 that every attempt to determine the line of transition proves inad- 

 equate. There is a great deal of truth in an expression of Calmeil, 

 that it is much easier to appreciate a hemiparalysis of motion 

 than a hemiparalysis of sensation. If the anterior fasciculi of the 

 cord possesses sensibility, but only in a slight degree, the mere open- 

 ing of the vertebral canal and laying bare the cord must cause sucl 

 a degree of pain as would weaken or destroy the manifestatioi 

 of sensibility in the anterior fasciculi. This has not been suffi- 

 ciently attended to by experimenters. Again, the practice of first 

 irritating the posterior fasciculi, and afterwards the anterior, musl 

 have had considerable effect in producing the same alteration. II 

 is plain that, in this way, the relations which the anterior fasciculi 

 bear to sensation must be greatly obscured ; yet, with the exception 

 of some few experiments, this has been the order of proceeding 

 generally adopted."*" 



All those who have made experiments with the view of ascer- 

 taining the function of the columns of the cord, agree in stating 

 that irritation of the anterior columns was attended with more or 

 less movement. The results of stimulation of the posterior columns, 

 however, have been differently stated by various observers : many 

 found that it was attended with the excitation of motion ; am 

 others, that the least irritation of the posterior columns excif 

 pain. M. Longet, who is among the latest experimenters on this 

 subject, observes, that motions result from irritation of the posterioi 

 columns only when the experiment has been made immediately 

 after the transverse division of the cord, and he refers such motions 

 to the excitability of the cord itself. After a little time, however, 

 this subsides; and then M. Longet has been able to pass the gal- 

 vanic current through each or both of the posterior columns, without 

 exciting any motions when the lower segment of the cord was acted 

 upon, but causing pain, as evinced by loud cries and writhing of the 

 body, when the upper segment was tried. Dr. Baly's experiments 

 on tortoises showed that movements might be excited whether the 



* Loc. cit. ; quoted from an abstract in the Brit, and For. Med. Review, vol. iv. 



