Chemical Agents on the Nervous System. 29 



6. It is also important, especially in a medical point of 

 view, to observe the manner and degree in which the vis 

 nervosa and the vis muscularis are diminished by repeated 

 Voltaic action. 



I. On the Electrogenic Condition of the Spinal Marrow. 



We made many unsuccessful attempts to effect the elec- 

 trogenic condition in the spinal marrow. If we passed the 

 Voltaic current through this structure, still contained in the 

 spinal canal, the conductibility of the surrounding tissues 

 prevented the induction of the electrogenic condition in the 

 spinal marrow itself, and the presence of a bony case, and 

 the want of firm membranes, inclosing the spinal marrow, 

 rendered it extremely difficult to denude and isolate this organ. 



JEx. 1. Our first experiment is represented in fig.l. of 

 Plate I., the Voltaic current being made to pass in the di- 

 rection of the arrows, from the spinal extremities of the 

 brachial nerves to those of the lumbar nerves, these nerves 

 themselves being excluded. In this manner, the spinal mar- 

 row was partially exposed to the Voltaic current. But we 

 found it impossible to produce the phenomena of the electro- 

 genic condition, whether we employed the direct Voltaic cur- 

 rent, as represented in the plate, or the inverse current. 



Ex. 2. Our next experiment is represented in fig. 2. The 

 head being removed, the lowest part of the spinal column, 

 technically the coccyx, was very carefully separated, and 

 every particle of muscle, or other humid tissue, was carefully 

 detached. We then inserted the end of one of the wires of 

 the voltaic circle within the spinal canal at the upper, and 

 the other at the lower orifice, thus effected, whilst we laid 

 the spinal column itself over a piece of sealing-wax, so that 

 it might become insulated, and its surface become dry. 



We now succeeded in inducing the electrogenic condition 

 of the spinal marrow ; not, however, by the direct current, as 

 represented in fig. 2, but by the inverse current applied by 

 reversing the wires of the Voltaic circle. 



The phenomena were the same, tetanoid contractions of 

 the muscle of the lower limbs (with slighter movements of 

 the anterior extremities), as are observed when the lumbar 

 nerves were subjected to the same current. 



