432 MESSRS. P. GOTCH AND V. HOESLEY 



SECTION 7. THE INFLUENCE OF SECTION OF BOTH POSTERIOR COLUMNS. 



A. Section of both Posterior Columns. 



The anatomical evidence clearly shows that there is an unbroken path between 

 some of the entering afferent fibres and the fibres in the posterior column, and that 

 these subsequently pass more or less completely into the posterior median column from 

 the posterior root zone. It was therefore essential to ascertain to what extent the 

 cord effect was dependent upon the presence of these fibres. This we have 

 endeavoured to do by first ascertaining to what extent the effect is due to the 

 unbroken integrity of both posterior columns. A remarkable incident in the course of 

 our experiments led us early to suspect that by far the greatest part of the effect, 

 whether crossed or direct, is conducted along these tracts. In the course of the 

 operation for one experiment, whilst opening up the neural canal, the point of the 

 bone forceps slipped, and so slightly bruised the posterior columns that the injury 

 could not be detected at the time. The preparation was proceeded with, and 

 the cord divided at the 8th dorsal. The upper end of the lower fragment was then 

 connected in the usual manner with the galvanometric electrodes, and the sciatic 

 nerves exposed for excitation. Only extremely small cord effects were, however, 

 evoked by the excitation. We then discovered the bruise and determined to make a 

 fresh section below the injury, exposing for this purpose more cord ; on connecting 

 this fresh portion with the galvanometric electrodes and exciting the nerve, an effect 

 of 175 scale was obtained. 



We now made a direct experiment along the lines thus indicated. 



The cord was exposed in a Cat, and divided at the 10th dorsal vertebra, 

 prepared for 4 centims. and connected with the electrodes by its surface and 

 cross section. Excitation of the left sciatic nerve, with the secondary coil at 

 2000 (1 Daniell in primary) for 5 seconds (500 stimuli), produced cord effects indi 

 cated by a deflection of 75 scale. The posterior columns were then divided at the 

 level of the upper border of the 12th dorsal vertebra, and a similar excitation was 

 accompanied by a deflection of only 12 scale. As a control, the cord was now 

 completely divided a,t this latter level, and the part distant from the new section was 

 connected with the galvanometer, when a similar excitation produced a deflection in 

 one case of 64, in another of 75 scale, thus indicating that the great diminution of the 

 effect was due to the local operative interference with the posterior columns, and not to 

 any general alteration in the condition of the whole cord. 



A similar result was obtained in another animal (Cat), in which the cord was 

 prepared and connected with the galvanometer at the level of the 10th dorsal 

 vertebra, and the cauda equina having been exposed, the central end of a cut 

 posterior root was excited, instead of the sciatic nerve. In this case the cord effect, 



