When we remove the internal oblique and cremaster muscles, we expose the transverse muscle, which may be regarded as the fifth inguinal layer, F, Pl. 30. This muscle is similar in shape and dimensions to the internal oblique. The connexions of both are also similar, inasmuch as they arise from the inner edge of the crista ilii, and from the outer half of, V, Poupart's ligament. The fleshy fibres of these two muscles vary but little in direction, and terminate at the same place--viz., the linea semilunaris, which marks the outer border of the rectus muscle. But whilst the fleshy parts of these three abdominal muscles, D E F, form successive strata in the groin, their aponeurotic tendons present the following peculiarities of arrangement in respect to the rectus muscle. The tendon of the external oblique, d, passes altogether in front of the rectus; that of the internal oblique is split opposite the linea semilunaris into two layers, which enclose the rectus between them as they pass to be inserted into the linea alba. But midway between the navel and pubes, at the point marked G, both layers of the tendon are found to pass in front of the rectus. The tendon of the transverse muscle passes behind the rectus; but opposite the point G, it joins both layers of the internal oblique tendon, and with this passes in front of the rectus. The fibrous structure thus constituted by the union of the tendons of the internal oblique and transverse muscles, e f, is named the "conjoined tendon." The conjoined tendon, f, Plates 30 and 31, appears as a continuation of the linea semilunaris, for this latter is in itself a result of the union of the tendons of the abdominal muscles at the external border of the rectus. As the conjoined tendon curves so far outwards to its insertion into the pectineal ridge of the pubic bone, as to occupy a situation immediately behind the external ring, it thereby fortifies this part against the occurrence of a direct protrusion of the bowel. But the breadth, as well as the density, of this tendon varies in several individuals, and these will accordingly be more or less liable to the occurrence of hernia. The arched inferior border of the transverse muscle, F, Plate 30, expresses by its abrupt termination that some part is wanting to it; and this appearance, together with the fact that the fibres of this part of the muscle blend with those of the internal oblique and cremaster, and cannot be separated except by severing the connexion, at once suggests the idea that the cremaster is a derivation from both these muscles.