4. Poisons, mephitic air, aëriform fluids, and condensed air, do not prevent animal electricity from being excited. 5. The influence of a vacuum on animal electricity is various. In dead animals, if kept a long time in vacuo, the animal electricity is weakened: in living animals it is considerably increased. 6. Though a vacuum does not prevent the electricity from being excited, it will not serve as a conductor of it when it has been excited: if an arc from the nerves to the muscles be intercepted by the smallest vacuum, no contractions take place. 7. As metallic armatures are of great effect in attracting and collecting artificial electricity, the case is the same with animal electricity; but care must be taken not to ascribe to them that electricity which the muscles naturally possess. 8. Though unlike armatures have a great effect in calling forth animal electricity, we have reason to conclude from several experiments, that they do not contain two kinds of electricity capable of producing muscular motion. 9. As natural electricity issues with great force from sharp-pointed bodies, and proceeds to them more readily than to others, the case is the same in regard to animal electricity, as it issues more readily from the pointed parts of the metallic arming applied to the nerves and muscles. 10. The nervo-electric fluid is propagated with that rapidity which is required in restoring to an equilibrium two opposite kinds of electricity. 11. The same conditions which cause two flasks to be discharged when an arc is established from the exterior coating of the one to the interior coating of the other, excite contractions in two frogs, when an arc is formed from the nerve of one to the muscles of the other. 12. The arc applied as above mentioned to the interior coating of two phials, and to the nerves of two frogs, seems to give more force to the proposed analogy; for the electric explosions have a great similarity to the muscular motions excited in the frogs. I might have enlarged the number of these corollaries, had not the well-known fate of various opinions, now consigned to oblivion, rendered me more timid in hazarding conjectures. I, however, did not allow myself to think that I ought so far to give way to my timidity as to check the spirit of inquiry, or to abandon the hope of one day attaining to the truth. But it would be unreasonable to expect in animal electricity, which is yet in its infancy, that precision and those satisfactory results which can be the work only of time, and of the continued labour of philosophers. [7] As this term is improperly used by philosophers, I must here observe, that I shall in future understand by it air highly rarefied by the usual means.