1. Testicular envelope. 2. Posterior serous septum. 2′. White muscular fibres of Bouley. 3. Serous membrane--portion of the tunica vaginalis. 3′. 3″. Visceral layers of the tunica covering the cord and the testicles. 4. The testicle with its peritoneal covering. 5. The epididymis. 5′. Globus major. 5″. Globus minor, the tail. 6. Deferent canal. 7. Spermatic blood vessels and nerves.] ANATOMY. We now pass rapidly in review the anatomical structure of the inguinal region and of the testicular organs. A knowledge of these is of course essential to a proper understanding of the description of the various modes of operation, and of some of their sequelæ, upon which we shall soon enter. The testicular envelopes, passing from the surface inwards, are represented by the scrotum, the dartos, the cellular coat, the tunica erythroida, formed by the cremaster, and the fibrous and serous or vaginal sac (Fig. 2). The scrotum is a continuation of the skin, and forms a complete bag, common to both testicles, which it contains and covers; the skin being here thin, vascular and nervous, usually black in color, almost hairless, and soft and unctuous to the touch. It is divided into two lateral halves by a raphæ or median line. It is very elastic, and easily yields to the efforts of distention, to which it is subjected, and when stretched over the organs it contains, presents a shining aspect, due to the sebaceous secretion which covers it. It easily contracts to its shrunken condition, and may be closely drawn up into the inguinal canal, when it assumes a thickly wrinkled surface. The second envelope, the dartos, is a prolongation of the tunica abdominalis, and is a yellow, fibrous structure, forming two distinct sacs resting upon each other, and lying on the inside of the scrotum, to which it is intimately adherent. In the lateral and superior parts the adhesions are looser, and in front it becomes continuous with the suspensory ligament of the sheath, which, like itself, forms a portion of the abdominal tunic. Under the dartos is a layer of very loose cellular tissue, the lamellæ of which are so formed that it may be divided into several superimposed layers. This formation endows the testicle with great mobility in the dartoid sac; and these layers may be easily separated with the finger from the external surface of the fibrous coat beneath, except posteriorly, where it forms a strong band which sometimes requires even the aid of an instrument to divide.