The Pelvis.—Before taking up the pelvic organs, the pelvis itself should be described. The name pelvis has been given to the bony ring which is interposed between the spine and the femurs on account of its resemblance to a basin. At the back of this basin or pelvis are the sacrum and coccyx, already described in connection with the back, and at the sides and meeting in the median line in front are the two ossa innominata or nameless bones, so called on account of their peculiar and indescribable shape. At birth each os innominatum is made up of three bones, the ilium, ischium, and pubes, but about the age of puberty the three become welded into one. At their point of junction is the cavity of the acetabulum for articulation with the head of the femur or thigh bone.

The upper, expanded portion of the os innominatum is the ilium, whose upper border is known as the crest and which has two spinous processes front and back, a superior and an inferior, the superior spine being in each case the larger. These spines, especially the anterior superior spines, and the crest give attachment to many muscles, and to the outer surface of the bone the gluteal muscles are attached. The anterior superior spine is also important in making measurements to ascertain whether both legs are of equal length.

Below the ilium posteriorly is the body of the ischium, which has on its lower edge a tuberosity, the prominent bone on which one sits. Near the upper edge is the spine of the ischium, between which and the posterior inferior spine of the ilium is the greater sacro-sciatic notch for the passage of vessels and nerves, including the sciatic nerves. From the tuberosity the ramus extends forward below the obturator foramen, a large opening between the ischium and the pubes, also for the passage of vessels and nerves, to meet the pubes, the last and smallest of the three bones which go to make up the os innominatum.

The anterior surface of each pubes presents a crest, ending externally in a spine, and the two pubic bones join in front in the symphysis pubis. The bone gets its name from the growth of pubic hairs over this region at puberty.

Anteriorly the ossa innominata support the external organs of generation, while within are the internal organs of generation. On the inner surface of the ilium, slightly above the level of the acetabulum, is the ileo-pectineal line, above which lie the iliac fossæ. A plane drawn through the prominence of the sacrum, the ileo-pectineal lines, and the upper margin of the symphysis pubis serves to divide the upper or false pelvis from the lower or true pelvis. The false pelvis, which is the larger, serves to support the intestines and to take part of the weight from the abdominal walls, while the true pelvis, being more surrounded by bone and so capable of affording more protection, guards the internal organs of generation. The lower circumference of the pelvis is known as the outlet. In the female the bones are lighter, the sacrum less curved, and the diameters greater than in the male.

On the whole, the pelvic bones are well covered in with muscles. The anterior superior spine, however, is easily felt in front and the whole crest can be felt back to the posterior superior spine. The tuberosity of the ischium also can be felt, especially when the thigh is flexed, for it is largely uncovered of muscles. The spine of the os pubis can always be felt, on a level with the great trochanter, and the relation of its position to that of a hernia shows whether the rupture is above or below Poupart’s ligament, that is, whether it is inguinal or femoral.

Occasionally there is lack of development of the pubic bones for two or three inches and the bladder is exposed. Fracture of the pelvis may occur, perhaps with injury to the viscera. The acetabulum may be fractured or the sacrum broken, with injury to the sacral plexus of nerves, causing paralysis of the lower extremities and of the sphincters, with resultant involuntary passage of urine and feces, and in childbirth the coccyx is often broken. In rickets there may be great deformity of the pelvis, causing trouble in childbirth later in life. Osteomalacia is a disease of adults, in which the bones are soft and the weight pushes the promontory of the sacrum forward and approximates the sides of the pelvis.

The Male Generative Organs.—The male generative organs consist of the prostate gland, testes, and penis.

The prostate gland is shaped like a small horse-chestnut and is composed of numerous glands from which come a dozen or more excretory ducts. It surrounds the neck of the bladder and the beginning of the urethra and is next to the rectum, through which an examination may be made to determine its size. For it often enlarges in elderly men, the frequent passage of urine in small amounts being a symptom of enlarged prostate.

The procreating glands, which secrete the spermatozoa or semen, are two in number, the testes or testicles, and are homologous to the ovaries in the female. They are ovoid in form and are suspended by the spermatic cords in a sac, the scrotum, back of the penis. During early fetal life they are in the back of the abdomen near the kidneys, but before birth they descend along the inguinal canals into the scrotum. The excretory duct of the testis is called the vas deferens. It passes up by the spermatic cord through the inguinal canal into the pelvis to the base of the bladder and at the base of the prostate joins the duct of the vesicula seminalis to form the ejaculatory duct. The two vesiculæ seminales are small receptacles for the semen lying in contact with the base of the bladder and secrete a fluid with which they dilute the semen. The ejaculatory duct terminates near the prostate in the urethra by a slit-like orifice on each side, the spermatozoa being finally excreted through the urethra.

The penis is the external organ of generation in the male and is attached to the pubes and the anterior part of the ischium. It is composed of erectile tissue and encloses the urethra, the meatus urinarius appearing at its end as a vertical slit. Toward the end the skin of the penis is loose and is prolonged forward in what is known as the prepuce or foreskin. It is this that is clipped away in circumcision.

The Female Generative Organs.—The female generative organs include the ovaries, Fallopian tubes, uterus, vagina, and the external genitalia or vulva.

The ovaries, which are homologous to the testes in the male, are two flattened oval bodies, grayish pink in color, suspended from the lateral or broad ligaments which fasten the uterus to the walls of the pelvis. They are one and a quarter inches long, three-quarters of an inch wide, and half an inch thick and are attached at the upper end to one of the fimbriæ of the Fallopian tubes. They consist of numerous Graafian follicles embedded in a fibrous stroma, each follicle containing an ovum about ¹/₁₂₅ inch in diameter and just visible to the naked eye. When a follicle ruptures and discharges an ovum, an irregular yellow spot, the corpus luteum, appears at the point of rupture. After ordinary menstruation it is known as the false corpus luteum and after conception as the true one, this one being larger and lasting longer.

The Fallopian tubes are the oviducts and convey the ova from the ovaries to the uterus. They are four inches long and lie between the layers of the broad ligaments, opening into the uterus by an orifice the size of a bristle, while the end next to the ovary spreads out trumpet-like and is edged with fimbriæ as with a fringe, the fimbriated extremity. There are three coats: a serous coat which is continuous with the peritoneum, a muscular coat, and, within, a mucous coat covered with cilia, continuous with the mucous membrane of the uterus. One fimbria is attached to the ovary and as the ovum is given off it finds its way into the tube and thence to the uterus.

The uterus is a pear-shaped organ, about three inches long, two inches broad above, and one inch thick, situated in the pelvic cavity between the rectum and the bladder. The wide part or fundus is above and the narrow neck or cervix below, lying partly within the vagina. The whole is held in place by ligaments. These include the broad ligaments, which extend from the sides of the uterus to the lateral walls of the pelvis, and the round ligaments, two muscular cords, about four inches long, which pass out through the abdominal ring into the inguinal canal and so to the mons veneris and labia, thus corresponding to the spermatic cords in the male. The cavity of the body of the uterus is small and flattened and opens into the cervix by the internal os uteri, the external os being at the opening of the cervix into the vagina. There are three coats: a serous coat derived from the peritoneum, a muscular coat of unstriped fibers which forms the bulk of the whole organ, and a mucous coat covered with ciliated epithelium.

The uterus is always enlarged during menstruation and is enormously enlarged in pregnancy. It receives the fecundated ovum, retains and supports it during the development of the fetus, and is the chief agent of expulsion. In tubal or extra-uterine pregnancy the ovum becomes attached in the tube instead of in the uterus, and develops there, rupturing the tube and causing serious hemorrhage.

The passage from the cervix out of the body is the vagina, a membranous canal, curved upward and backward to conform to the axis of the pelvis, and attached above to the cervix. Ordinarily the sides are in contact.

The arteries of the internal organs of generation are the uterine from the internal iliac and the ovarian from the aorta in the female, the pudic branches of the internal iliac and the spermatic from the aorta in the male. The nerves are largely from the sympathetic system.

Abscess formation occurs frequently in the tubes and gonorrheal infection may spread up the vagina and through the uterus to the tubes, and even to the abdominal cavity itself. The tubes may also be tubercular.

Salpingectomy or removal of the tubes is the commonest operation after that for appendicitis. Cancer of the uterus may necessitate panhysterectomy or removal of the uterus and all its appendages.

The external genitalia in the female, as in the male, are situated over the pubic arch. They are known as the vulva and include the mons Veneris, the labia majora and minora, the vaginal orifice, the clitoris, and the meatus urinarius.

The mons Veneris is a rounded eminence composed of fatty tissue, which surmounts the pubic bones and is covered with hair at puberty. From it two prominent longitudinal folds of skin, covered with hair on the outside, the labia majora, extend backward, forming the lateral boundaries of the vulva. Within these labia again are two thin cutaneous folds, the labia minora or nymphæ, which run back from the clitoris for about one and a half inches and enclose the vaginal orifice. The clitoris corresponds to the penis and is just above the upper part of the labia minora. Between it and the vagina is the meatus urinarius. The orifice of the vagina is partly closed in the virgin by the hymen, a thin fold of mucous membrane, which occasionally closes it completely, imperforate hymen. The fourchette is a small transverse fold of skin at the junction of the labia minora posteriorly. Between the vagina and the rectum is the perineal body, a somewhat triangular structure made up of many small muscles. Its surface is known as the perineum. It is frequently torn wholly or in part during childbirth and has to be sewed up.