The substance of the testicle is composed of large numbers of minute convoluted tubes termed "tubuli seminiferi" (e, fig. 223). These are grouped together in small masses or "lobules", and occupy the spaces, already referred to, into which the organ is divided by strands of fibrous tissue given off from the " mediastinum testis". Although occupying separate compartments the tubes of one lobule freely communicate with those contiguous with it. The semen secreted by the seminal tubes is conveyed to the "mediastinum testis" by a number of straight ducts, "vasa recta" (fig. 223c), which there unite and form a net-work, the rete testis. The secretion then leaves the testicle by means of the "vasa efferentia ", a group of vessels, each of which twists and turns upon itself to form a conical mass, "coni vasculosi", and these together constitute the globus major. From the globus major the "vas deferens" or main excretory duct takes its origin, and after twisting and turning about to form the globus minor, continues its course upward along the inguinal canal to the pelvis, where, after reaching the upper surface of the bladder, it becomes enlarged, and after joining with the duct of the vesicula seminalis it opens into the prostatic portion of the urethra by the ejaculatory duct.

Section of Testis showing the arrangement of the Ducts composing the Testicle.

Fig. 223. - Section of Testis showing the arrangement of the Ducts composing the Testicle.

A, Vas Deferens or Spermatic Duct. B, Globus Minor. c, Vasa Recta or Straight Seminal Tubules. D, Tunica Albuginea. E, Spermatic Tubules forming the Lobules. F, Rete Testis or net-work formed by the straight tubes. G, Globus Major. H, Tunica Vaginalis Reflexa. I, Spermatic Vein. J, Spermatic Artery.