[Illustration: _a._ Bladder, or receptacle of urine. _b._ Ureters, or passages through which the urine comes from the kidneys, where it is formed, to the bladder. _c._ Vas Deferens, through which the semen passes from the testicle, where it is formed, to the seminal vesicles, where it is matured. _d, d._ Openings of Ureters into the bladder. _e._ Prostate Gland. _f._ Orifices of excretory ducts. _g._ Openings of the seminal ducts. _h._ Ischio-cavernous muscles. _i._ Bulb of Urethra divided. _k._ Cowper’s Glands. _l._ Wide part of Urethra. _m._ Narrow part. _n._ Fossa Navicularis, usually affected in gonorrhœa. _o, p._ Prepuce.] The urethra is constantly moistened with a mucous secretion,—from the membrane itself, the glands, and the folds which yield to the pressure of the urine as it flows, or from other altered conditions of the urethra pour out their contents. The inner surface of the urethra is very vascular and sensitive, as is shown by the slightest laceration by the bougie or by chordee, when considerable bleeding often takes place. Its sensitiveness is well known in the first passing of the bougie, or in inflammation, when the pain of the former and the act of urinating in the latter, often causes fainting. The bladder is the reservoir of the urine, which is formed in the kidneys, comes into the ureters, passages leading from the kidneys to the bladder, and thence flows, drop by drop, into the bladder. The bladder is shaped somewhat like a pear, but this shape is varied by its contents, and the relative condition of its adjacent parts. Thus, when the bladder is full, its upper part may be felt rising above the pubis, that portion of the lower part of the belly that is covered with hair. In very fat persons the bladder is flattened by the weight of the intestines, and obliged to find room where it can, as in pregnant women. Anatomists, when describing the bladder, speak of its body, base, or upper part, sides and neck, where the urethra or water passage begins, and which is surrounded by the prostate gland. These parts are seen in the first engraving on the opposite page. The bladder is composed of several coats. There is a peculiar membrane investing the important structures in the abdomen called the peritonœum. The base and back part of the bladder is covered by a portion of this peritonœum, which in a measure supports the bladder in its position, and also exercises certain properties which may hereafter be alluded to.