Abstract: A specimen processing cartridge includes a first fluid source operable to deliver a first liquid to a first flow path and to transmit the first liquid to a testing area. The cartridge also includes a second fluid source operable to deliver a second liquid to a second flow path and a bridging member positioned between the first flow path and second flow path. The bridging member is operable to receive the second liquid from the second fluid source, and to deform from a first position to a second position upon receiving the second liquid. When not deformed, the bridging member does not contact the first flow path. When deformed, however, the bridging member contacts the first flow path and is operable to transmit the second liquid to the first flow path upon contact.