定義： A 1D measurement of a single cell along its longest axis. Typically, this is the distance along a straight line connecting the anterior-most point and the posterior-most point.
定義： A 1D measurement of a single cell. Typically, this is the distance along a straight line connecting the left-most part of the cell to the right-most part of the cell. It is perpendicular to the length axis and the depth axis.
