muscle on either side will cause, on account of the contraction of the muscle of the opposite side, a displacement laterally of the mouth of the vagina and anus. A destruction of the anterior fibers of the levator ani muscles, those having their attachment to the pubis, will cause the vagina and anus to be drawn backwards by the contraction of the portion of the levator ani muscle attached to the coccyx. A destruction of the transversus perinei muscles on both sides at the point of junction in the perineum; a destruction of the sphincter vaginæ at the point of decussation in the perineum; a destruction of the levator ani muscle at the point of junction in the perineum; will cause a vacuum in the perineum because of the contraction of these muscles toward their bony attachments, and the posterior mucous membrane of the vagina and the anterior wall of the rectum will fall in apposition.

Method of Laceration of the Perineum.-With normal conditions and normal labor the soft parts of the floor of the pelvis, including the decussating fibers and layers of fascia constituting what is commonly known as the perineum, are relaxed and will stretch to such an extent that the delivery of the child's head and shoulders can be accomplished without destroying any of their supporting fibers. The first to yield to the pressure of the child's head will be the decussating muscular fibers constituting the recto-vaginal septum, or perineum; second, the fascial layers of connective tissue constituting the recto-vaginal septum; third, the isthmus of skin covering the perineum, that part lying between the anus and the vulva; fourth, the mucous membrane of the vagina; fifth, the mucous membrane of the anus.

The degree of laceration will depend upon the extent of the injury to all of these tissues. Frequently the muscular layers are almost completely crushed out while the skin and mucous membrane of both the vagina and rectum remain uninjured. It is very seldom, on the other hand, that a laceration of the skin and mucous membrane occurs without

an excessive destruction of the fascial layers and the decussating muscular fibers.

Extent of Injury.-The extent of the injury to the perineum cannot be estimated by a casual observation of the external parts. It is obvious that it would be impossible by an ocular inspection of the external genitals alone, to ascertain the extent of the injury of the muscles in the recto-vaginal septum, if, as is very frequently the case, the skin and mucous membrane of the perineum be injured.

Very frequently only the sphincter muscles of the vagina are destroyed. With such an injury the vulvar outlet will be increased in diameter as a result of the destruction of the constricting fibers of the sphincter and the mucous membrane of the posterior wall of the vagina will fall away from the anterior vaginal wall, corresponding to the degree of the laceration.

If the injury is still more extensive and the external fibers of the sphincter ani, as well as the fibers of the sphincter vaginæ, are destroyed, this will involve also a portion of the fibers of the levator ani, which decussate between the vulva and the anus, to such a degree that the same will be drawn backwards by the posterior fibers of the levator ani; this in turn drawing backwards the posterior wall of the vagina which has fallen in apposition to the anterior wall of the bowel or anus (because of the destruction of the tissue between the two) to such an extent that the vulva will present a gaping cavity, the vulvar opening being transformed so that its long diameter lies anterior-posteriorly, instead of laterally.

With the destruction of the muscles to this extent, too, the torn ends of the contracting fibers will cause small dimples or pits in the mucous membrane of the posterior vaginal wall, representing the points of their separation. As a rule a laceration of this extent will also carry with it a partial destruction of the skin surface of the perineum and more or less destruction of the mucous membrane of the posterior vaginal wall. These scars will be apparent to the naked eye, and in

the case of a recently lacerated perineum there will be no difficulty whatever in discovering the torn tissue. If the laceration involves a destruction of the muscles of the sphincter vaginæ, the transversus perinei, the sphincter ani, and the decussating fibers of the levator ani, the mucous membranes of both the vagina and the rectum, together with the skin of the perineum, will be, as a rule, destroyed, and a sickle-like projection some distance above the vulvar and anal outlet will represent the septum between the two tubes, the upper surface of this septum being lined with the mucous membrane of the vagina while the posterior surface of the septum will be lined with the mucous membrane of the rectum.

Mechanics of the Repair of the Perineum.-In observing carefully the different degrees of laceration and the behavior of the vulva and anus under different degrees of destruction of the recto-vaginal septum, one will soon be impressed with the difficulties to be encountered in the proper repair of a laceration of this tissue. One will notice that the anus and the vulvar outlet will fall away from the pubic arch in exactly the degree that the anterior fibers of the levator ani muscles are, destroyed. He will notice that a loose vulvar outlet indicates a destruction of the sphincter muscles of the vagina. He will frequently notice pits or depressions beneath the mucous membrane of the vagina, which indicate the points of the ends of the disrupted fibers which are constantly pulling in the direction of their bony attachments-the transversus perinei toward the spine of the ischium, the levator ani in the direction of the rami of the pubes, and the posterior fibers of the levator ani in the direction of the anus and its bony attachment the coccyx.

A close observer will be impressed with the behavior of the various tissues destroyed and by their action will be able to study out the method of repair.