Page:Popular Science Monthly Volume 2.djvu/381

Rh thread: besides, the difference between the instants noted, or what is termed the "personal equation," of two astronomers, varies more or less according to circumstances, and may increase or diminish with time. The observer's training has a great deal to do with it, Wolf having demonstrated that, by practice, the time lost may be reduced to a minimum, with the employment of a special apparatus.

An important conclusion follows irresistibly from these experiments: it is, that the nerve-fluid is not identical with the electric fluid. Electricity darts through telegraphic wires with inconceivable rapidity, far outspeeding light, and moving 20,000,000 times faster than the nerve-agent. There exists another important difference between these two forces. Any alteration in the structure of the nerves checks the transmission of the nerve-current; crushing or partial burning is enough to interrupt its passage; once cut, they do not regain their conductive power when the separated ends are brought together again. Metallic wires, on the contrary, conduct electricity in spite of all the injuries that may be inflicted on them. Yet the well-known labors of Prof. Dubois-Reymond clearly prove that electricity plays a part of some kind in nervous phenomena. Electric currents exist naturally in nerves, and these currents are influenced and modified by the action of the nerve-currents. It may be admitted, then, that nervous phenomena are the result of a secondary action of electricity, producing certain changes, chemical or otherwise, in the nerve-substance; these manifest themselves only after the lapse of a certain time, during which the action increases in a slow and gradual manner till it becomes sensible, and produces mechanical effects. This side of the question is still enveloped in profound darkness, and we are driven to more or less plausible hypotheses. Still, we can say that a great step has been taken toward the solution of the problem of life: the experiments of which this account is given have thrown light upon its approaches, and placed the question on the ground of exact science. No doubt a long time will pass before the progress of methods of observation shall permit us to make one step nearer to the goal, and nothing authorizes the belief that we can ever fully reach it; but we may take pride in what has already been done, since the exactness of the results gained surpasses all expectation.—Revue des Deux Mondes.



T has been said that "dirt is but matter out of place," and we may likewise take for an axiom that error is force misapplied. It cannot be complained that the age in which we live is one which demands the most careful economy of our forces of all kinds, nor are we intellectually in the position which geologists are fond of predicting for