[Illustration: _a._ The inner surface of the Bladder, showing the direction of the Muscular Fibres. _b._ The opening of the right _Ureter_ into the Bladder, whence the urine issues. _c, c._ The Prostate Gland cut through, and its sides exhibited. _d._ The Urethra. _e._ Verumontanum. _f, f._ Orifices of the Seminal Ducts, marked by twigs inserted therein; the other points mark the orifices from the Prostate and other Glands.] The position of the _perineum_ is seen in the following cuts in which the skin has been removed, disclosing— [Illustration: 1. The superficial fascia of the Perinœum. 2. The fascia lata, or shiny covering of the muscles of the thighs. 3. The tuberosity of the ischia, or part whereupon we sit. 4. The last portion of the spine, called the Coccyx, easily to be felt posteriorly to the rectum. _a._ The Sphincter muscle of the Anus. _b._ The inferior border of the great muscles of the buttock, called the Gluteal. _c._ The Levator Ani, or muscles which elevate the rectum.] The following cut represents the muscles of the perinœum exposed, the superficial fascia having been removed. [Illustration: 1. Point in the Perinœum where the principal muscles arise or meet. 2. Covering of the Thigh. 3. Seat. 4. Corpora Cavernosa of the Penis. 5. Corpus Spongiosum. 6. Coccyx. 7. Great Sacro Sciatic ligament. _a, a._ Erector Muscles of the Penis. _b, b._ Accelerator Urinæ Muscles. _c._ Line whence the above Muscles take their origin. _d._ Transverse Muscles of the Perinœum. _e, e._ Sphincter Muscle of the Anus, supposed to be distended with tow or wool. _f, f._ Levatores Ani. _g, g._ Great Gluteal Muscles.] A brief description of the structures displayed in the two preceding and the following drawing (p. 14) will render this part of our subject perfect. The _Fasciæ_ means the coverings of muscles, such as is seen in cutting a domestic joint—a leg of mutton, for instance—a shiny surface; their use is to strengthen the action of the muscles, to bind them well together, and they mostly exist about the buttocks, back, &c. The office of a Sphincter Muscle, of which we have several, as that of the bladder and anus, is to keep closed the aperture they surround. The sphincter ani closes the rectum, and pulls down the bulb of the urethra, by which it assists in ejecting the urine and semen. The Levator Muscles lift up the part they are connected with. The levator ani muscles form the funnel appearance of the rectum, and help to draw it up after the fæces or stools are evacuated. They also assist in sustaining the contents of the pelvis, and help to eject the semen and urine, and contents of the rectum, and, perhaps, by pressing upon the veins, contribute to the erection of the penis.