circular fibres within these, and an internal longitudinal layer on which rests the submucous coat. It is disputed whether there is a sphincter at the neck of the bladder. Probably there is not; but the puckering of the mucous membrane at the neck is alleged to have a valve-like function. The peritoneal covering of the bladder will be considered subsequently.

The relation of the ureters to the bladder is of importance. Garriguez has recently investigated this subject owing to its importance in GastroElytrotomy.

In this obstetric operation, employed in cases where craniotomy or the cæsarean section is the alternative, the operator cuts through the abdominal walls with the same incision as that for ligature of the external iliac artery. The peritoneum is pushed aside and the vagina partly cut and partly torn by an oblique incision. The child is then extracted. In some of the cases the bladder or ureter has been torn into.

According to him "the ureter does not lie in the broad ligaments, it does not keep the same direction on reaching the wall of the bladder, and it does not lie close up to the wall of the cervix, all of which is taught by anatomical authorities. After having crossed the iliac vessels the ureters diverge, running downward, backward, and a little outward on the wall of the pelvis, behind the broad ligaments to a point near the spina ischii. Then they bend downward, forward, and considerably

U Uterus; ur Ureter; B Bladder; u Urethra; V Vagina; 7 Fallopian tube; 0 Ovary; b Broad ligament; r Round ligament; ct Connective tissue; x Incision of Vagina in Gastro-elytrotomy. (3)

inward so as to converge toward the bladder. They pass beneath the

base of the broad ligament, lying in the abundant cellular tissue found in this locality. They cross the cervix at some distance from behind, at an acute angle, so as to come in front of and below it. They lie outside and above the anterior part of the side wall of the vagina, on a spot as large as the tip of the finger. On reaching the wall of the bladder they turn rather sharply inward and go less downward until they open with a small slit into the interior of the bladder at the outer angle of the trigonum vesica. But on dissecting the bladder from the uterus and vagina, their substance is seen to continue running as a solid ridge

Vertical mesial section of Female Pelvis, shewing Y shape of Bladder (Fürst). (1)

between the two apertures, and forming the base of the trigone (Jurie's interureteric ligament)." (See Fig. 33).

Shape of empty bladder and changes in its position.-The empty female bladder lies completely behind the pubis, and has its fundus covered by peritoneum. When empty and viewed in mesial section it may present one of two shapes. In the large majority of specimens figured, it forms with the urethra a Y shape on sagittal mesial section. The oblique legs of the Y may be about equal in size, or the posterior may be shorter (Figs. 40, 34). This form is so common that it has been accepted hitherto by all authors as the normal one. In certain cases, however, insignificant in number as compared with the former, the empty bladder cavity forms with the urethra a continuous tube on vertical mesial section (Fig. 35). In such cases, it is oval in shape, corrugated, and firm to the touch. This latter shape is the one always found in the lower animals, such as the rabbit and dog, and is the only one seen in the human foetus. If, therefore, the pelvic floor of a woman be viewed on its peritoneal aspect, the fundus of the empty bladder will be found to be almost always large and concave, while in a few cases it is small and convex. In the former case, the inner surface of the upper segment of the bladder, large in area, is in contact with the surface of the lower segment; in the latter, the anterior and posterior inner walls, small in area, touch one another.

Vertical mesial section of Female Pelvic Floor, shewing contracted bladder in a suicide (Braune). () The peritoneum descends in front of the uterus to b and behind it to d; b a and d c are loose extraperitoneal tissue.

It is probable that when the bladder has the Y shape on section, it is in diastole (Fig. 34); and when the oval shape (Fig. 35), it

C

has been caught in systole. The bladder contracts to expel the urine and then relaxes. Between the acts of urination the bladder is there fore only a flaccid sac. Some additional facts as to the position and distention of the bladder are best considered further on, under the structural anatomy of the pelvic floor. We may here state, however, that (1) when empty, in the non-parturient female, it is behind the pubis (Fig. 32); (2) it is drawn above the pubis in the parturient female; (3) it is tilted above the pubis in retroversion of the gravid uterus.

The so-called ligaments of the bladder are false and true. The false are formed of peritoneum and will be considered under the peritoneum of the pelvic floor. The true ligaments are formed of the pelvic fascia.

RECTUM.

The Rectum extends from the left sacroiliac synchondrosis, where the

b

Fig. 36.

Rectum inflated (Chadwick).

ab Sphincter tertius; c Ampulla of Rectum.

sigmoid flexure of the colon terminates, to the anus.

It curves downwards, backwards, and inwards, to about the third sacral vertebra. This

is known as the first part of the rectum; it is completely covered by peritoneum, which forms the mesorectum. The peritoneum is reflected from the rectum on to the upper part of the vaginal wall, about 3 inches above the vaginal orifice. Thereafter, the rectum lies in relation anteriorly to the posterior vaginal wall to which it is loosely attached until about 1 inches from the anus.

The rectum is made up of peritoneal investment; unstriped muscular fibre in two layers, longitudinal and circular, the former being the outer; a submucous coat; and a mucous lining with its musculares mucosae, columnar epithelium, no villi, but with Lieberkuhnian follicles closely set together. At the upper limit of the anus, the circular fibres are very well marked and constitute the sphincter ani internus (fig. 37).

Certain oblique folds in the rectum-consisting of mucous, submucous, and circular unstriped muscular coats-are of special interest. One exists 1 inches from the anus, another is near the sacral promontory, and one is intermediate (Turner). The lowest (the valve of Houston or sphincter ani tertius of Hyrtl) has been described by Chadwick of Boston, as being not an entire circular fold but made up of two semicircular constrictions, one on the anterior wall and one on the posterior an inch higher up (Fig. 36).

The Anus is that part of the rectum at its external orifice. It is about an inch long, and has its long axis directed backwards and cutting the axis of the vagina at about a right angle. The rectum, therefore, when in contact with the posterior vaginal wall, closely follows its direction but at about 1 inch from the anus turns sharply backwards. There is thus left between it and the last 1 inch or so of the posterior vaginal wall, an angular inter-space to be filled up by the structure known as the perineal body.

Fig. 37, from Ruedinger, shews the arrangement of the voluntary and involuntary muscle of the anus. The division of the external sphincter into two parts, and the separation of the lower division (5) into compartments by fibres from the longitudinal unstriped layer (9), are noteworthy. Similarly the internal sphincter (7) is divided into compartments by fibres from the muscularis mucosae (13). Near the anal orifice the mucous membrane has certain perpendicular folds in it known as the Columnae Morgagni, with depressions between these — the Sinus Morgagni (fig 2).