1. A medication infusion system for infusing a plurality of fluids into a living body, comprising: a main cassette including therein a first fluid pump having an inlet to which a first fluid is supplied from a first source, and an outlet from which said first fluid is pumped, said main cassette also including therein a battery for providing power to said system; at least one auxiliary cassette including therein a second fluid pump having an inlet to which a second fluid is supplied from a second source, and an outlet from which said second fluid is pumped; a main pump unit onto which said main cassette and said auxiliary cassette may be removably attached; a first prime mover comprising the means for driving said first fluid pump, said first prime mover being mounted in said main pump unit; a second prime mover comprising the means for driving said second fluid pump, said second prime mover being mounted in said main pump unit; electronic controller means for controlling the operation of said first and second prime movers, said electronic controller means controlling each of said first and second prime movers independently to cause said first and second prime movers to drive said first and second pumps independently of each other, said electronic controller means being mounted in said main pump unit; and electrical connecting means for electrically connecting said battery to said electronic controller means, said electrical connecting means comprising a first connecting means mounted in said main cassette and a second connecting means mounted in said main pump unit.