be perpendicular to the other two, and it is obviously a little square, with an area of (ô§ã₤ a )ÿ£¢ 2 =ã₤ô¥ã₤ a ÿ£¢ 2 ã₤.
From this we may draw the simple rule that, for a rectangular body or parallelopiped to be divided equally by means of a partition of minimal area, (1) the partition must cut across the longest axis of the figure; and (2) in the event of successive bisections, each partition must run at right angles to its immediate predecessor.
We have already spoken of ãSachsãs Rules,ã which are an empirical statement of the method of cell-division in plant-tissues; and we may now set them forth in full.
- (1) The cell typically tends to divide into two co-equal parts.
- (2) Each new plane of division tends to intersect at right angles the preceding plane of division.
The first of these rules is a statement of physiological fact, not without its exceptions, but so generally true that it will justify us in limiting our enquiry, for the most part, to cases of equal subdivision. That it is by no means