and accomplishes a similar result is not invention. Even if
the substituted part performs the function better, there is no
patentable invention unless some new function or result is secured.
Changes therefore of the relative location of parts without changing
the functions performed by them are not an invention, nor is the
omission of a part with a corresponding omission of function.

A patent can issue only to the inventor, or if he is dead to his
executor or administrator. If there be two original inventors the one
who first made it or brought it to this country is entitled to a
patent. A patent granted on the application of a non-inventor is void.
By first inventor is meant the one who first had a mental conception
of the invention provided he exercised diligence in perfecting it. If
there be a rival claimant the party who first reduced to practice the
invention was, until the contrary fact is shown, the first inventor.
One who merely utilizes the ideas of others is not an original
inventor and is not entitled to a patent. In the United States any
person, regardless of residence, citizenship or age may obtain a
patent.

An invention is reduced to practice when it is so far perfected that
it may be put into practical and successful use. The machine may not
be perfectly constructed, but it embodies all the essential elements
of the invention. Demonstration of its success by actual use is
usually necessary, but not always. The reduction to practice must be
by the applicant for a patent, or by his agent; to do this by a third
party will not suffice. The person who first conceived the invention,
but was later than his rival in reducing it to practice, is not
regarded as the first inventor unless he exercised due diligence to
perfect his invention after the time that his rival entered the field
against him.

Two or more parties may contribute in developing an idea and producing
an invention, which is truly the result of their joint mental efforts,
and not the separate invention of either. In such case both must apply
for the patent, which is granted to them jointly. But if a patent is
thus issued to two and only one of them is the inventor, the patent is
invalid. Nor can one of two joint inventors make application and
secure the patent on assignment from the other; both must join.

The patent must issue on the application of and in the name of the
real inventor even though he was employed to make it for the benefit
of