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.
The next envelope is represented by the tunica erythroida which is the cremaster muscle, and from the lumbar region extends itself downwards into the inguinal canal along the outside of the cord, and terminates towards the superior part of the testicle in fibres spreading only over its external face. This muscle, by its deep surface, rests upon the fibrous coat—another envelope of the testicle and of the cord—and to which it is closely adherent. To the powerful contraction of this muscle is due the retraction of the testicle into the depth of the groin, which condition sometimes it is so difficult to overcome in the first stages of the operation.
The fibrous testicular envelope which we have just seen giving attachment to the cremaster, is a thin membranous bag, elongated like the neck of a bottle around the spermatic cord, which it envelopes, and dilated below, in order to enclose the testicle. Lined internally by the serous coat, to which it intimately adheres, this last membrane is a duplicature of the peritoneum, drawn downwards by the testicle when it descends from the abdominal cavity into the inguinal canal. This serous envelope has, therefore, two coats, one lying on the inside of the fibrous tunic, and called the parietal, and that which covers the cord and the testicle and is known as the visceral. These two layers approximate towards the posterior border of the cord, and, as they unite, form a sort of fold, band, or septum which divides into two parts the posterior portion of the vaginal cavity, and becomes a means of solid adhesion between the tail of the epididymis and the bottom of the sac.
The testicles, thus covered by the visceral layer of the serous coat, are suspended at the end of the spermatic cord, and surmounted upon their superior border by the epididymis, the first part of the deferent canal, which is folded upon itself, while at its posterior extremity—the “tail,” so called—it continues in a straight course, and conveys the product of the secretion of the testicles into the vesiculæ seminales, lodged in the pelvic cavity.
The spermatic cord is formed anteriorly by the spermatic or great testicular artery, which forms, in that portion, a large number of flexuosities, causing its length greatly to exceed that of the cord to which it belongs. It contains a network of veins, and lymphatic vessels in abundance, which are united to the curves of the artery by a somewhat loose cellular tissue. A large number of nervous branches, given off by the solar plexus, surrounds the whole.
Between the lamellæ of peritoneal structure which forms the posterior septum, and which unites the parietal with the visceral layer, there is found a band of grey muscular fibres—first discovered, I believe, by H. Bouley—which exerts a powerful agency in the retraction of the testicle towards the inguinal ring. Behind this muscle, and situated on the internal face of the septum, are found the deferent canal and the circumvolutions of the small testicular artery.
Having thus considered the essential points of the anatomical structure of these organs, we shall next seek to enforce the importance of their careful study in reference to the intelligent and skilful performance of the important operation which we are discussing.