Retractable surgical knife
FIG. 1 is a front and top perspective view of a rectractable surgical knife showing my new design; 
     FIG. 2 is a left side elevational view thereof; 
     FIG. 3 is a right side elevational view thereof; 
     FIG. 4 is a top plan view thereof; 
     FIG. 5 is a bottom plan view thereof; 
     FIG. 6 is a front elevational view thereof; 
     FIG. 7 is a back elevational view thereof; and, 
     FIG. 8 is a front and top perspective view thereof, with the blade in retracted position.