Most inflammations begin in the epididymis, and may remain limited to it or extend to the testicle. In the causation two groups of cases are recognizable, one in which an affection of the urethra has preceded the disease, and the other in which the infection has occurred through the blood.

To the first group belong cases of urethritis, chiefly gonorrhoea!, also cases in which the inflammation has succeeded catheterization. In explanation of the transference of the inflammation from the urethra to the testis the terms metastasis and sympathy have been used. It may be that reflex contraction of the vessels of the testicle may induce a testitis, but there seems little doubt that in most cases there is an actual propagation of the inflammation by the vas deferens. The urethritis of gonorrhoea is due to a specific microbe, which may advance by multiplication, and after catheterization there may be a septic urethritis and microbes may similarly extend. This implies that the vas deferens is inflamed in its course from the one situation to the other, and there are often symptoms of this.

Orchitis is an occasional accompaniment of Parotitis or Mumps. It is probable that here the two local manifestations are due to the specific infection which" is present in the blood. Orchitis also occasionally accompanies or succeeds certain other general diseases, such as typhoid fever, small-pox, gout, scarlet fever, and acute tonsillitis.

The inflammation usually begins in the epididymis, and generally remains almost limited to that structure. There is hyperemia and serous exudation producing great swelling. At the same time there is often serous fluid in the tunica vaginalis. The testis itself is usually but slightly swollen. There may be resolution without suppuration, or the disease may become chronic, or suppuration may occur. In the latter case an abscess or abscesses form in the epididymis or testicle, and these may burst externally. On the other hand, the abscess may dry-in and form a caseous mass, which becomes surrounded by a fibrous capsule. This mass may ultimately become calcareous.

Chronic orchitis may arise out of an acute attack, whether suppurative or not. Most cases of so-called spontaneous orchitis are really syphilitic or tubercular. The ordinary chronic orchitis is characterized by new-formation of connective tissue in the stroma of the organ, and consequent induration of it. The tubules atrophy and the whole organ is reduced in bulk and hardened. Generally on section it can be seen that the tunica albuginea and the septa, which proceed towards the mediastinum, are greatly thickened. At the same time there is frequently adhesion of the tunica vaginalis so as to obliterate the sac.