Thorax
the breast, and specially the bones inclosing it. It is somewhat conical, with convex walls. Its upper opening is contracted, and bounded by the first dorsal vertebra, the first pair of ribs, and the manubrium of the sternum.
Its inferior margin slopes downward on each side to the 12th rib; its longitudinal axis is directed upward and somewhat backward; its transverse diameter at the widest part greatly exceeds the distance THORAX from the breast to the back. It consists of the dorsal vertebræ, the sternum, the ribs, and the costal cartilages, and contains the lungs, the heart, etc. The muscles of the thorax are: The intercostals, levatores costarum, the sub-costals, triangularis sterni, with which may be included the diaphragm. In comparative anatomy, the part of the trunk above or anterior to the diaphragm. In entomology, the central diversion of the body of insects. It is formed of three consolidated somites or segments; the prothorax, the mesothorax, and the metathorax. Also, a breastplate, cuirass, or corselet.