The epididymis, composed of a much-convoluted tube some 20 feet long, is applied to the posterior border of the testicle, from which it is separated by an involution of the serous covering, forming a groove called the digital fossa. It presents a body connecting globular upper and lower extremities, the former and larger being called the globus major, and the latter the globus minor. The tube begins in the globus major, where it receives the seminal fluid through some twenty minute vasa efferentia, which pierce the tunica albuginea to reach it, and ends at the globus minor in the vas deferens. Attached to the globus major, one or more small pedunculated bodies, called hydatids of Morgagni, are frequently present, and above the globus major a similar, but larger, body, called the organ of Giraldés, or paradidymis, is occasionally met with. These bodies probably give rise to certain forms of hydrocele and spermatocele. The epididymis is covered by the tunica vaginalis on its exposed parts, except over the greater portion of its posterior border. It is chiefly by this exposed border of epididymis that the testicle is fixed in situ, where it remains even in large hydroceles.

The testicle body, about inches long, 1 inch from before backwards and rather less in thickness, is suspended in the scrotum, with its long axis directed upwards, slightly forwards, and outwards. The left testicle hangs at a lower level than the right, and this is given as one reason for the prevalence of varicocele on the left side. The testicle is enveloped in a tough white inelastic coat called the tunica albuginea, which sends in septa to its interior, and which is perforated by the vessels and lymphatics at the posterior border, where the tunic and septa meet, forming a fibrous mass called the mediastinum testis (corpus Highmori). It is partly owing to the unyielding character of this coat that acute affections of the testicle are generally very painful.

The tunica vaginalis resembles the peritoneum, from which it is derived, in structure and also in its relationship to the testicle which it encloses. It is a shut sac into which the testicle is invaginated. Hence there is a visceral layer enveloping the testicle, dipping into the digital fossa, and covering the epididymis, save at the point of exit of the various structures of the cord, and a parietal layer which lines the scrotal sac. In hydrocele of the tunica vaginalis the sac may attain a very large size, holding many pints, and when tapping such conditions in order to draw off the fluid, it is important to remember that the testicle lies on the posterior surface, a short distance from the bottom. Distension of the tunica vaginalis with blood is called hematocele.

The testicle is supplied with blood by the spermatic artery, a branch of the aorta, which traverses the cord to reach it, and anastomoses with the artery to the vas. The blood is returned by a series of veins which, issuing on the posterior border of the testis, form a dense plexus called the pampiniform plexus. This plexus is of importance surgically, as it frequently becomes varicosed, particularly on the left side, giving rise to the condition known as varicocele. In addition to the fact that the left testicle hangs lower than the right, there are several anatomical reasons for the predominance of left-sided varicocele : On the right side the spermatic vein (which receives the blood from the plexus) is valved, and discharges its blood obliquely into the inferior vena cava, whereas on the left it is frequently not valved, and discharges its blood at right angles into the renal vein. Further, the left vein is subject to pressure from a distended colon or sigmoid. Some small veins also run up along the vas accompanying its artery. The lymphatic vessels of the testicle pass up along the cord to the lumbar lymphatic glands. The nerve-supply is derived from the tenth dorsal segment through the aortic and renal plexuses, and communicates on the lower part of the vas with branches from the hypogastric plexus. Thus, kidney and testicle are closely associated in nerve-supply, and the testicle is in direct communication with the solar plexus and semilunar gangliae, which are associated with the termination of the vagus. Hence, injury to the testicle frequently causes collapse and a marked tendency to vomit, while pain is generally felt in the renal region in testicular neuralgia, and conversely the testicle is retracted in passage of renal calculus, etc. The epididymis receives its nerve-supply from the pelvic plexus. The artery to the vas-a branch of one of the vesical arteries-accompanies it to the testicle, where it anastomoses with branches of the spermatic artery. The vesiculi seminales are supplied by the inferior vesical artery. Both vasa and vesiculi are supplied by branches of nerve from the hypogastric plexus.

Many of the affections to which the testicle is liable resemble in outward appearance an inguinal scrotal hernia. Hydrocele of the tunica vaginalis, and of the cord, and varicocele have already been described.

The testicle itself may be affected by (a) tubercle, which first affects the epididymis (epididymitis), and is chronic ; (b) gonorrhoea, which also first affects the epididymis, but is acute (epididymitis) ; (c) syphilis, which first affects the body of the testicle (orchitis) ; and (d) sarcoma, which rapidly involves both body and epididymis, and spreads up the cord. Sarcoma is very malignant, and might almost be described as subacute, the lungs rapidly becoming involved, unless early castration be performed. The testicle may retain its foetal position within the abdomen (cryptorchismus), or it may descend to about the position of the external abdominal ring, and resemble an inguinal bubonocele, or hernia, which has not descended into the scrotum. To this form of testicular displacement, as well as that first described, the term undescended testicle may be applied. Sometimes also the testicle may descend, but becomes turned-inversion of the testicle-so that it lies in front of the tunica vaginalis, and would therefore be liable to be wounded in the ordinary method of tapping a hydrocele. Where the testicle has not fully descended, attempts may be made to bring it down by operation and fix it in position, and if these attempts do not succeed, it is generally safer to remove it, lest malignant degeneration occur.

In removing the testicle-castration-it is generally advisable to cut the vas far up, so as to get beyond the disease, if possible ; to fix the cut end to the abdominal parietes after ligature and disinfection ; and to ligature the other structures of the cord separately.

The scrotum, in which the testicles are lodged, consists originally of two lateral folds, one on either side of the urogenital furrow. In the female these folds remain separate, and form the labia majora. In the male they coalesce, the median raphe marking the line of coalescence. The integument of the scrotum is thin and delicate, and the subcutaneous tissue is devoid of fat, and contains a layer of unstriped muscle, called the dartos tunic, by the contraction of which the scrotum may be. thrown into folds. These folds, or rugae, frequently lodge dirt, which, causing'irritation, may set up eczema. Chimney-sweep's cancer, which occurs on the scrotum, was supposed to be due to soot lodging in these crevices. On the other hand, the skin is very distensible, as is seen in large hydroceles, herniae, etc., and when thus stretched is fairly translucent, enabling the translucency of a contained swelling to be tested by transmitted light. The subcutaneous tissue is lax, and is readily affected in cedematous swelling and elephantiasis. The interior of the scrotum is divided into two by an incomplete septum, derived partly from the dartos tunic. The left compartment hangs lower than the right, and each is lined by separate tunica vaginalis, infundibuliform, cremasteric, and intercolumnar fasciae. The scrotum is supplied with blood by superficial perineal branches of the internal pudic posteriorly, and external pudic branches of the femoral anteriorly. The nerves are derived from superficial perineal branches of the internal pudic, perineal branches of small sciatic, and from the ilio-inguinal nerve. The lymphatics run to the inguinal glands.