The invention resides in apparatus and methods for isolating and collecting cells from donor tissue for later use in medical procedures. The apparatus includes a sealed enclosure, at least one screening material inside the enclosure, an inlet port configured to conduct a fluid through the screening material, and an outlet port for receiving the fluid from the screening material and conducting the fluid out of the enclosure. A material to be screened is placed inside or conducted into the enclosure. Screened material is entrained in the fluid. The fluid carries bits of the material through the screening material and out of the enclosure for later separation from the fluid. Preferred embodiments include a series of screening materials of decreasing pore size, usually in the range from ten to one thousand micrometers in diameter. A particularly preferred embodiment includes three distinct screening materials having pore sizes of 400 micrometers, 280 micrometers, and 100 micrometers, listed in the order that the fluid passes through the screening materials. The invention is used in the collection and isolation of porcine hepatocytes for later use in medical procedures. The sealed enclosure is constructed of a series of individual segments held together by conveniently removable fasteners--bolts and wing nuts. A mechanical shaker agitates the enclosure as the fluid flows over and through the material being screened.