_Ductus ejaculatorii._—The ejaculatory ducts traverse the prostate and open, by slit-like orifices, into the sinus pocularis. The wall of the ducts is much thinner than that of the vas deferens. The muscular fibres of the latter are gradually substituted in the ducts by cavernous tissue. The mucous membrane differs little from that of the vas deferens and of the seminal vesicles. [Illustration: CUT VIII. _Male urethra_ 1, bladder; 2, prostate; 3, colliculus; 4, orifice of the sinus pocularis; 5, orifices of the prostatic ducts; 6, orifices of Cowper’s glands; 7, corpus cavernosum urethræ; 8, corpora cavernosa penis; 9, præputium; 10, glans; 11, fossa navicularis.] _Urethra._—The urethra is divided into three parts, the prostatic, the membranous and the cavernous parts. The prostatic part is the widest portion of the entire urethra. It is surrounded by an unstriped muscular layer and the muscles of the prostate. The membranous part is the narrowest, shortest, and most thin-walled portion of the three parts of the urethra. It is entirely surrounded by the muscular fibres of the diaphragma urogenitale, which takes here a circulatory course. It is in this way situated on the border-line of the abdominal cavity and the exterior, within the abdominal wall. The cavernous portion of the urethra is surrounded by the corpus cavernosum urethrae. This portion shows two dilatations, one in the bulbous part, just anterior to the termination of the membranous part, where the ducts of the two Cowper’s glands open; the other dilatation is near the end, behind the meatus, forming the so-called fossa navicularis. The meatus itself is the narrowest part of the entire urethra. Numerous mucous crypts, the glands of Littré and certain lacunae, the largest among them near the fossa, open into the lumen of this part of the urethra. The entire urethra is lined with a cylindrical epithelium, except at the fossa navicularis. The latter is covered by a layer of pavement epithelia. The length of the urethra is about 18 centimeters. In the usual state the urethra possesses only a virtual lumen, i. e., the walls touch each other. [Illustration: CUT IX. _Schema of sagittal cut through penis. After Testus._ 1, bladder; 2, vas deferens; 3, colliculus; 4, prostate; 5, urethra; 6, bulbus urethræ; 7, symphysis.]