The spongy urethra is that part which is enclosed in the penis after piercing the anterior layer of the triangular ligament. At first it lies in the substance of the bulb and, later, of the corpus spongiosum, while finally it passes through the glans. In the great er part of its course it is a transverse slit, but in traversing the glans it enlarges considerably to form the fossa navicularis, and here, in transverse section, it looks like an inverted T (1), then an inverted Y (A), and finally at its opening (external meatus) a vertical slit. Into the whole length of the urethra mucous glands (glands of Littre) open. As a rule the meatus is the nar rowest part of the whole canal.
Opening into the spongy urethra where it passes through the bulb are the ducts of two small glands known as Cowper's glands, which lie on each side of the membranous urethra.
The penis is the intromittent organ of generation, and is made up of three cylinders of erectile tissue, covered by skin and sub cutaneous tissue without fat. In a transverse section two of these cylinders (the corpora cavernosa) are above, side by side, while one, the corpus spongiosum, is below. At the root of the penis, the two corpora cavernosa diverge, become more and more fibrous in structure, and are attached on each side to the rami of the ischium, while the corpus spongiosum becomes more vascular and enlarges to form the bulb. The whole length of the corpus spon
giosum is traversed by the urethra. The anterior part of the penis is formed by the glans, a bell-shaped structure, apparently con tinuous with the corpus spongiosum, and having the conical ends of the corpora cavernosa fitted into depressions on its posterior surface. On the dorsum of the penis the rim of the bell-shaped glans projects beyond the level of the corpora cavernosa (corona glandis). The skin of the penis forms a fold which covers the glans (prepuce or foreskin) ; when this is drawn back a median fold, the frenulum praeputii, is seen running to just below the meatus. After forming the prepuce the skin is reflected over the glans and here looks like mucous membrane. The structure of the corpora cavernosa consists of a strong fibrous coat, the tunica albuginea, from the deep surface of which trabeculae penetrate the interior and divide it into a number of spaces which are lined with endothelium and communicate with the veins. Between the two corpora cavernosa the sheath is not complete and, having a comb-like appearance, is known as the septum pectinatum. The structure of the corpus spongiosum and glans resembles that of the corpora cavernosa, but the trabeculae are finer and the net work closer.