PLATE 45, Fig. 2.--There exists a very evident analogy between the canals through which both herniae pass. The infundibuliform fascia, 3, 3, of the spermatic vessels is like the infundibuliform sheath, 9, 9, of the femoral vessels. Both sheaths are productions of the general fibrous membrane of the abdomen. They originate from nearly the same locality. The ring of the femoral canal, 12, is situated immediately below, but to the inner side of the internal inguinal ring, 3. The epigastric artery, 1, marks the width of the interval which separates the two rings. Poupart's ligament, 5, being the line of union between the oblique aponeurosis of the abdominal muscle and the fascia lata, merely overarches the femoral sheath, and does not separate it absolutely from the spermatic sheath. [Illustration: Abdomen, showing bone, blood vessels and other internal organs.] PLATE 45.--FIGURE 2 PLATE 45, Fig. 3.--The peritonaeum, 2, 3, closes the femoral canal, 12, at the femoral ring, in the same way as this membrane closes the inguinal canal at the internal inguinal ring, 3, Fig. 2, Plate 45. The epigastric artery always holds an intermediate position between both rings. The spermatic vessels in the inguinal tube, 3, 3, Fig. 2, Plate 45, are represented by the round ligament in the female inguinal canal, Fig. 3, Plate 45. When the bowel is about to protrude at either of the rings, it first dilates the peritonaeum, which covers these openings. [Illustration: Abdomen, showing bone, blood vessels and other internal organs.] PLATE 45.--FIGURE 3 PLATE 45, Fig. 4.--The place of election for the formation of any hernia is that which is structurally the weakest. As the space which the femoral arch spans external to the vessels is fully occupied by the psoas and iliacus muscles, and, moreover, as the abdominal fibrous membrane and its prolongation, the femoral sheath, closely embrace the vessels on their outer anterior and posterior sides, whilst on their inner side the membrane and sheath are removed at a considerable interval from the vessels, it is through this interval (the canal) that the hernia may more readily pass. The peritonaeum, 2, and crural septum, 13, form at this place the only barrier against the protrusion of the bowel into the canal. [Illustration: Abdomen, showing bone, blood vessels and other internal organs.] PLATE 45.--FIGURE 4