A system for conducting commercial transactions between buyers and sellers is disclosed. Thereby, when a taking lens 11 of a first group having an O-ring 16 fitted thereto is mounted into the barrel 15, air in the barrel 15 is pushed out from the image-side opening 15\u20142 of the barrel 15 through the ventilation channels 15b1, 15c1, 15d1, and 15e1. The apparatus is configured to maintain the first and second needles in a first position, during insertion of the biopsy needle point into the tissue being sampled. A portion of the second opposite end of the elastic member may extend beyond the downwardly facing surface of the base to make contact with the resting surface to prevent the device from sliding on the surface.