The very small difference between the acquisitions of the two, however marvellous when viewed abstractedly, sinks into nothing when compared to the secrets of nature which yet remain unexplored. This comparison is the true source of that humility which, while it adds dignity to the acquirements of intellect, is the foundation on which we may most securely rest the hope of increasing possessions. The intellectual vision of the wisest man confines him to a very small area, when compared with the boundless realms of nature. There are, indeed, a number of objects within the range of his perceptions whose nature and relations he has the power of examining; but there are also a multitude of others which, from their dimly sketched outline, he feels to be beyond the bounds assigned to his limited faculties. One of the most curious things in animals is the rigidity or stiffness of their muscles after death. It is, as it were, the last effort of the living principle. This phenomenon may be indefinitely modified by particular states, by lightning, by poison, and other peculiar conditions, induced by the manner and the period at which the death may have occurred; and in all cases it continues but for a short time. It is the last exercise of that power which resides in muscles or flesh, of contracting, and thus moving the various parts to which it is attached. In a very large sense, this power is under the dominion of the will, and enables animals to move as their instincts or their wants suggest. Now it is a curious thing to think that this power can be excited after death, by placing the parts between two pieces of metal, or galvanizing them; so called after the name of the discoverer, Galvani. It is difficult, at this day, to imagine the astonishment of the wife of Galvani, or his pupil, when first they observed the leg of a dead frog thrown into convulsions on being touched by a piece of metal. Such, however, was the apparently simple origin of a long series of wonderful discoveries. It has been well observed, however, that "discoveries, apparently the result of accident, always imply the exercise of profound thought." And this was no less the case in respect to galvanism. A fact, which, but for the mention of it to Galvani by his wife, might have passed unobserved, was, by the scarcely less than creative power of mind, improved into a most important branch of human science. Ignorant as men still remain of the _intrinsic nature_ of the principle or power which gives rise to the phenomenon, the observation and study of _its laws_ and _operations_ have led to discoveries which, in their value, their importance, and their surprising character, yield to no other yet achieved. Abernethy, who, at this laborious period of his life, had his observation directed everywhere, made some experiments on this power (galvanism), in its relations to the muscles of frogs.