To identify molecular determinants of lytic bone disease in multiple myeloma, the expression profiles of \u02dc12,000 genes in CD138-enriched plasma cells from newly diagnosed multiple myeloma patients exhibiting no radiological evidence of lytic lesions were compared to those with \u22673 lytic lesions. A multiplexer receives input signals from both the ROM microcode and RAM microcode, and a control signal which is one or more RAM data bits is used to select from the RAM or ROM microcode inputs for further execution by the microprocessor. A second directory structure is provided in main memory that includes one or more entries with each entry formatted to provide addressability to a predetermined number of entries in the first directory structure. A further embodiment of the invention includes a second suction device mounted adjacent the inlet side of the sieve in trailing relationship to the brush arrangement so as to be able to carry away contaminants loosened by the brush arrangement but still clinging to the inlet side of the sieve.