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At a former meeting I called the attention of the Association to the painlessness of incisions and injuries when made by circular saws, bullets and other objects moving at a rate exceeding 200 feet in a second. I also detailed some experiments with a revolving knife made to move by a powerful spring at a similar velocity.
A careful study of certain classes of surgical injuries, seems to show that pain exists only when the traumatic agent moves at a certain intermediate range of velocity, and that wounds made by objects moving on the one hand at a very high speed, or, on the other hand, at a very slow, imperceptible rate of motion, are nearly painless—often entirely so.
Practical application of this law has long been made in surgery, where a fine rubber thread is made slowly and painlessly to cut through the sphincter in cases of fistula in