It is essential to the validity of a patent that it be granted on an application signed and sworn to by the original and first inventor or inventors, or his or their executors or administrators. No other person, even with the consent of the inventor, can sign or swear to an application that will support a valid patent. The Patent Office has no means of ascertaining these facts, and will necessarily be governed by the oath of the application. Should it, however, afterwards develop that the party making the application was not the inventor, the patent will be invalid.

The fact that a person furnishes capital, machinery or material for developing the invention, gives him no right to make or join in the application for patent. Such person may acquire an interest under the patent, but this can only be done by an assignment executed by the inventor and transferring to him the whole or any fractional portion of the entire right to the inven-tion and to the patent. If such an assignment is recorded in time the patent will be issued to the assignee, or jointly to the assignee and the inventor, as the case may be.

The builder of a new machine or device is not the inventor if he did not himself originate the ideas or principles contained in such device. In other words, an inventor may employ others to construct and mechanically perfect his invention without losing his exclusive right thereto, and without giving the mechanic who constructs it any right to the patent, unless it has been agreed upon by contract between the two parties. Even in that case the mechanic will take his right only by reason of the contract and under a properly executed assignment.

If a person conceives the general plan of an invention and employs another to construct and perfect the same, and the latter under such employment originates improvements which are included in, or, as the court said in one case, an ancillary to, the general plan, such improvements nevertheless belong to the person furnishing the general plan and can be included in any patent for which he may apply.

All patents and patent rights can be assigned without restriction by the owner or owners thereof, either before or after the patent is granted, or even before the application for patent is filed. All such assignments must be executed by the party or parties who have the legal title to the invention at the time the assignment is made. An assignment may cover the whole right under the patent or any fractional portion thereof.

An assignment must be recorded in the Patent Office within three months after the execution thereof. Otherwise it will be void as against subsequent purchaser for a valuable consideration and without notice of such assignment.