REPUDIATION OF AN OFTEN-ALLEGED OPINION.
"It is not meant that electricity is life. There are strong analogies between electricity and magnetism; and yet I do not know that any one has been hardy enough to assert their absolute identity[40]. I only mean to prove that Mr. Hunter's theory is verifiable, by showing that a subtile substance of a quickly, powerfully mobile nature seems to pervade everything, and appears to be the life of the world; and therefore it is probable that a similar substance pervades organized bodies, and produces similar effects in them.
"The opinions which, in former times, were a justifiable hypothesis, seem to me now to be converted into a rational theory[41]."
IN RELATION TO MICROSCOPIC OBSERVATION.
"This general and imperfect sketch of the anatomy of the nervous system relates only to what may be discovered by our unassisted sight. If by means of the microscope we endeavour to observe the ultimate nervous fibres, persons in general are as much at a loss as when, by the same means, they attempt to trace the ultimate muscular fibres[42]."
ILLUSTRATION, OF MOTION NOT NECESSARILY IMPLYING SENSATION.
"Assuredly, motion does not necessarily imply sensation; it takes place where no one ever yet imagined there could be sensation. If I put on the table a basin containing a saturated solution of salt, and threw into it a single crystal, the act of crystallization would begin from the point touched, and rapidly and regularly pervade the liquor till it assumed a solid form. Yet I know I should incur your ridicule if I suggested the idea that the stimulus of salt had primarily excited the action, or that its extension was the effect of continuous sympathy. If, also, I threw a spark amongst gunpowder; what would you think, were I to represent the explosion as a struggle resentful of injury, or the noise as the clamorous expression of pain[43]?"