produced, he is entitled to a claim whose breadth of language is
commensurate with the improvement he has wrought in the art. He cannot
claim functions or performance, but must limit his claim to mechanism,
in other words, to the combination of elements which produces the new
result. His claim recites those elements by name. If the new result
cannot be produced by any other combination of elements, then, of
course, no question will arise regarding infringement. But it may be
that a competitor contrives a device having some of the elements of
the combination as called for by the claim, the remaining elements
being omitted and substitutes provided. The competing device will thus
not respond to the language of the claim. But the courts will deal
liberally with the claim of the meritorious pioneer inventor, and will
apply to it the doctrine of mechanical equivalents, and will hold the
claim to be infringed by a combination containing all of the elements
recited in the claim, or containing some of them, and mechanical
equivalents for the rest of them. Were it not for this liberal
doctrine, the pioneer inventor could gather little fruit from his
patent, for the patent could be avoided, perhaps, by the mere
substitution of a wedge for the screw or lever called for by the
claim. The court, having ascertained from the prior art that the
inventor is entitled to invoke the doctrine of equivalents, will
proceed to ascertain if the substituted elements are real equivalents.
A given omitted element will be considered in connection with its
substitute element, and if the substitute element is found to be an
element acting in substantially the same manner for the production of
substantially the same individual result, and if it be found that the
prior art has recognized the equivalency of the two individual
elements, then the court will say that the substituted element is a
mechanical equivalent of the omitted element, and that the two
combinations are substantially the same. This reasoning must be