In pig progeny testing and in bacon carcass competitions some of the marks are awarded on the basis of measurements taken on the intact sides. These measurements help in assessing the value of the side, but to obtain a more complete picture of the amount of fat and to assess the size and shape of the longissimus dorsi muscle, another important point, it is usual to cut through the side at the level of the head of the last rib at right angles to the line of the back to examine a cross-section of this muscle. Whilst the fat to lean ratio is important, much attention has also been paid to the size and shape of the transverse section of the longissimus dorsi muscle, especially as regards the depth (B measurement) see Fig. 1.