A compressor including a hollow housing having a suction chamber, a discharge chamber, and a crank chamber formed therein. This new cell fluorescence method correlates with other methods of enumerating cells such as the standard plate count, the methylene blue method and the slide viability technique. The inlet and outlet can be switched so that an exit previously serving as the outlet is utilized as an entrance serving as the inlet and at the same time an entrance previously serving as the inlet is utilized as an exit serving as the outlet. The scanning head assembly, coupled to the lighting device, scans the document. The technique is applicable in both the reception mode and the transmission mode.