30 On the Effects of Certain Physical and 



Having failed in inducing the electogenic condition by the 

 direct current, the conduction of the surrounding part, after all 

 our precautions, preventing the induction of the contained 

 structure by this means, it was necessary to devise some nevv^ 

 mode of experiment. 



Ex. 3 and 4. Our first attempt v^^as to denude and raise 

 the spinal marrow, by removing the bony case at the poste- 

 rior part of the canal ; our second was to effect the same ob- 

 ject by removing the bodies of the vertebrae at the anterior 

 part of that canal. We succeeded eventually in both. But 

 the latter result, on account of the less hardness of this part 

 of the bony structure, is much more easily obtained than the 

 former. 



Having denuded the spinal marrow, we raised it from its 

 bony case, with the utmost case, and gently placed it on the 

 zinc portion of the Voltaic arc of silver and zinc, whilst the 

 silver was placed on the lowest part of the spine, so that the 

 Voltaic current was directed in the spinal marrow as repre- 

 sented in fig. 3. In four minutes, the spinal marrow being 

 raised from its contact with the zinc, we had distinct tetanoid 

 contractions of the femoral muscles, not to be distinguished 

 from those produced by the electrogenic state of the lumbar 

 nerves. This state ceased instantly on dividing the spinal 

 marrow at its lowest part. 



We learn from these facts, as from some of those which 

 were given in my former paper, — 



1. That the contiguity of humidity prevents the electro- 

 genic induction of the nervous tissues ; and, 2d, that the in- 

 verse voltaic current efi^ects the electrogenic condition more 

 readily than the direct. 



I may here state that on one occasion I observed that the 

 lumbar nerves became subject to the electrogenic condition, 

 whilst still in contact with the lumbar tissues, as these be- 

 came partially desiccated, an effect which ceased on the free 

 application of moisture. And it was always observed, in the 

 experiments in which the Voltaic current ascended one lumbar 

 nerve and descended the other, that the ascending current 

 first induced the electrogenic state. 



Ex. 5. We removed the head and the bodies of the verte- 



