II. The Pelvic Diaphragm (Fig. 94). Under the pelvic fascia, which forms a fibrous layer of the pelvic floor, is found a horseshoeshaped muscular expansion, which is open in front, is attached all around to the wall of the pelvis, and forms a double loop behind the vagina and the rectum. It is generally described as two muscles, the levator ani and the coccygeus, but they touch each other with their edges, so that one is a continuation of the other, and sometimes they are even grown together. This diaphragm has also been described as composed of three muscles: the pubo-coccygeus, the obturatococcygeus, and the ischio-coccygeus (Savage), but not one of the fibers that start from the pubes are inserted on the соссух.

The levator ani muscle takes its origin from an oblique line on the posterior surface of the body of the pubic bone, running from the upper end of the obturator foramen to the lower end of the symphysis pubis, just above and inside of the insertion of the obturator internus muscle (M. pubo-coccygeus). It starts half an inch from the middle line of the symphysis. Its other bony origin is a small circle just in front of the base of the ischial spine. Between these two points. it springs from the tendinous arch of the pelvic fascia (M. obturatococcygeus).

The pubic portion (M. pubo-coccygeus) goes backward and inward, is in connection with the deep layer of the triangular ligament, and is attached to the urethra. It crosses the vagina, and is united to it by strong connective-tissue attachments, besides that the longitudinal fibers of the vagina on its lateral aspects are interwoven with those of the levator. Some loops go from side to side between the vagina and the rectum, but the greater part go behind the rectum, forming loops without intermediate tendon. They hug the concavity of the end-curve of the rectum and support it from below (Fig. 95). The muscle goes in between the external and internal sphincter, and intermingles with both of them, as well as with the longitudinal fibers of the rectum. Some of the fibers are inserted on the thin mesial aponeurosis, extending from the coccyx to the anus (raphe ano-coccygea).

The fascial portion of the levator ani muscle (M. obturato-coccygeus) goes with convergent fibers to the rectum and the coccyx. It takes part with the pubic portion in the formation of a loop behind the rectum, and another part of it is inserted on the fourth coccygeal vertebra.

The ischio-coccygeal muscle (= the coccygeus) forms likewise a triangle, but the base of this triangle is turned inward. It takes its origin on the spine of the ischium and the lesser sacro-sciatic ligament, and is inserted on the side of the upper part of the coccyx and the last two vertebræ of the sacrum.

Function. The pelvic diaphragm strengthens the pelvic floor; in

connection with the two fascia that cover its upper and lower surface (the vesico-rectal and the anal fascia) it forms a strong sheet on which rest the uterus and the bladder. It is the antagonist of the thoracic diaphragm, being relaxed under inspiration and contracting under expiration. By inserting a Sims speculum it is easy to see

Side View of the Levator Ani (L) after Removal of the Ischium. The lower bundles are the strong and heavy ones. The sphincter ani is shown surrounding the anus, and the coccygeus (C) is faintly indicated (Luschka-Dickinson):

the rhythmical movement synchronous with the respiration. The anterior wall of the vagina goes downward and backward under inspiration, and then upward and forward during exspiration.

The pelvic diaphragm lifts the rectum up during the act of defeca

tion, and draws the anus forward in the direction of the symphysis. It exercises a similar function toward the vagina during childbirth by pulling it upward and pushing the child forward, so as to make it turn round the pubic arch. By means of the loops that go between the vagina and the rectum it becomes a sphincter vagina, which can produce coarctation of the vaginal entrance. It draws the coccyx forward.

III. The Perineal Region. The perineal region is a somewhat rhomboid space bounded by the symphysis and the descending ramus of the pubic bone, the ascending ramus and the tuberosity of the ischium, the lower edge of the gluteus maximus muscle, and the tip of the coccyx. In depth it comprises all the tissue lying within these boundary-lines between the surface and the pelvic diaphragm. It is shorter and broader than in man, and contains more fat. It may be subdivided by a line drawn just in front of the tuberosity of the

Diagram of the Fascia of the Pelvic Floor in mesial section, to show how the levator ani muscle is backed by strong and dense sheets of fibrous tissue (Dickinson): 1, superficial perineal fascia, outer layer (this we call simply subcutaneous adipose tissue); 2, superficial perineal fascia, inner layer (our superficial perineal fascia); 3, triangular ligament, or deep perineal fascia, outer layer; 4, triangular ligament, or deep perineal fascia, inner layer: 5, vesico-rectal (part of pelvic) fascia.

ischium on either side into two triangles, an anterior, or uro-genital region, and a posterior, or anal region.

In the anterior triangle we distinguish the following layers:
Skin;

Adipose tissue;

Superficial perineal fascia;

Deep perineal fascia divided into two layers;
Anterior continuation of ischio-rectal fossa;
Levator ani muscle;

Vesico-rectal fascia (i. e. part of pelvic fascia).

In the posterior triangle are found the following layers:
Skin;

Adipose tissue entering and filling ischio-rectal fossa;
Anal fascia inside, lower part of obturator fascia outside;
Levator ani muscle inside, obturator muscle outside;
Vesico-rectal fascia.

A. The Perineal Fascia and Ligaments.-The uro-genital region has under the skin a layer of adipose tissue (Fig. 96), which is a continuation of the similar layer on the surrounding parts (Fig. 97).

FIG. 97.

3 2PM 4 S

Transverse Section of Pelvis through Axis of Vagina (Savage): V, vagina, showing posterior wall; O, ischio-rectal fossa filled with fat: I, ischial tuberosity; B. perito

neal cavity; D, recto-vesical fascia covering upper surface of levator ani muscle; C, anal fascia covering lower surface of levator ani; N, obturator fascia; P, posterior aponeurosis of perineal septum, or the deep layer of the triangular ligament; M, anterior aponeurosis of the same, or superficial layer of the triangular ligament; S, superficial perineal fascia; 1, cross-section of right crus clitoridis and

Under that layer is found a sheet of dense connective tissue called the superficial perineal fascia. It is fastened in front and on the sides to the edge of the rami of the pubis and ischium, and behind it turns over the superficial transversus perinæi muscle, and is here grown together with the deep perineal fascia. In its anterior part it is grown together with Broca's pouch (p. 37), and at the ramus of the ischium with the obturator fascia.

The deep perineal fascia, also called the triangular ligament of the urethra, has two layers-an anterior, or superficial layer, and a posterior, or deep layer. The su

perficial layer is at the sides attached to the rami of the pubes and ischium, in front to a strong transverse ligament called the transverse ligament of the pelvis

erector clitoridis muscle: 2, superficial (Henle), which lies immediately

transversus perinæi muscle; 3, bulb; 4, deep perineal muscles.

under and behind the subpubic ligament, an opening for the dorsal

vein of the clitoris separating the two. Behind it is grown together

with the superficial perineal fascia and with the deep layer of the deep fascia. The deep layer of the deep fascia is likewise fastened to the rami of the pubes and the ischium, where it joins the obturator fascia (p. 94), and covers the anterior part of the lower surface of the levator ani muscle. At its anterior attachment it is contiguous with the vesico-rectal fascia. Behind it is continued as a dense fascial sheet covering the lower surface of the levator ani muscle (the anal fascia, or levator fascia).

The deep perineal fascia is perforated by the urethra and the vagina. Where the superficial perineal fascia and the two layers of the deep perineal fascia come together, at the posterior margin of the superficial transversus perinæi muscle, they are fortified by a strong transverse fibrous band, the ischio-perineal ligament, which is inserted on the ramus of the ischium, just in front of the tuberosity, and forms the boundary-line between the uro-genital and the anal regions. It is a strong cross-beam, which by its connection with all the adjacent parts forms the chief support of the pelvic floor. Together with the posterior end of the superficial and deep perineal fascia it forms a partition between the anterior and posterior part of the perineal region, called the transverse perineal septum.

In the anal region the skin is darker and has large sebaceous glands. The anus forms an opening at the deepest point of the sulcus between the nates. It is closed from side to side so as to show a line of closure in the antero-posterior direction (Fig. 87, 12). It is surrounded by radiating folds of the skin, and often hairs. In women the raphe between the anus and the vulva (perineal raphe) is often effaced, and has sometimes a whitish color, much like a cicatrix, which has to be borne in mind in answering the question whether a subject for examination has given birth to a child or not. Under the skin is found a thick layer of adipose tissue. There is no special superficial fascia, and the deep perineal fascia does not extend so far back.

Between the rectum and the ischium is found a space on either side which is called the ischio-rectal fossa, and has the shape of an irregular triangular pyramid. Its top is at the spine of the ischium; the inner wall is formed by the levator ani muscle, covered by the anal fascia, the outer by the obturator internus muscle, covered by the obturator fascia, below the line of demarkation between that fascia and the vesico-rectal fascia covering the upper surface of the levator ani muscle (p. 94). Its entrance from below is bounded by the lower edge of the gluteus maximus and the greater sacro-sciatic ligament behind, the transversus perinæi superficialis muscle in front, and the external sphincter ani on the inner side. Posteriorly these two spaces communicate by means of the loose adipose tissue behind the rectum and pelvic fascia. In front the fossa is limited by the line of junction of the superficial and deep perineal fascia. Here it be