In patent law. Any act or substance which is known in the arts as a proper substitute for some other act or substance employed as an element in the invention, whose substitution for that other act or substance does not in any manner vary the idea of means. It possesses three char-acteristics: It must be capable of performing the same office in the Invention as the act or substance whose place it supplies; it must relate to the form or embodiment alone and not affect in any degree the idea of means; and it must have been known to the arts at the date of the patent as endowed with this capability. Duff Mfg. Co. v. Forgie, 59 Fed. 772, 8 C. C. A. 261; Norton v. Jensen, 49 Fed. S»>8, 1 C. C. A. 452; Imhaeuser v. Buerk, 101 U. S. G55, 25 L. Ed. 945; Carter Mach. Co. v. Hanes (C. C.) 70 Fed. 859; Schillinger v. Cranford, 4 Mackey (D. C.) 466
Source: Black’s Law Dictionary 2nd Ed (1910)
