The science and art of obstetrics / by Theophilus Parvin.

  • Parvin, Theophilus, 1829-1898.
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: The science and art of obstetrics / by Theophilus Parvin. Source: Wellcome Collection.

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    attached to the border of the coccyx and of the lower part of the sacrum, and the apex to the ischial spine. The two ischio-coccygeal muscles hinder the backward movement of the coccyx. They, with the anal levators, make the deep muscular layer of the perineal floor, aod beneath the plane they form the anal sphincter is placed. This muscle has the form of an ellipse, the long diameter being antero- posterior ; it arises by muscular fibres attached to the last bone of the coccyx and subjacent skin; these then form on each side of the amis a semicircular baud, and, converging in front, are inserted in the perineal body. Beneath the sphincter is the skin. The part of the pelvic floor thus described is called the posterior perineal region; it is triangular in form, the apex of the triangle being at the tip of the coccyx and its base a line between the ischial tuberosi- ties. The anterior perineal region is included between the line just mentioned and the pubic joint. The pelvic floor is here formed ot skin, fasciae, and muscles. The latter are seven, viz., one vaginal sphincter and two ischio-cavernosi, two transverse perineal and two ischio-bulbous. The vaginal sphincter arises from the perineal body, surrounds the vaginal orifice, and is inserted upon the body of the clitoris and its suspensory ligament. The ischio-cavernosus has its origin on either side from the ischial tuberosity and from the ischio- pubic ramus, and is inserted by two tendinous expansions, one above and the other below the union of the crura of the clitoris. The trans- verse perineal muscles arise from the ischial tuberosities below the pre- ceding, and are inserted in the perineal body. The ischio-bulbous muscle passes from the ischium on each side to the corresponding bulb of the vagina. Three aponeurotic planes are found in the anterior perineal region—the deep, the middle, and the superficial. Between the last two the muscles just described are placed. Perineum. This part of the pelvic floor is of especial interest to the obstetrician. It is bounded by the anus behind, by the ischial tuberosities on the sides, and by the vulval opening in front. These limits apply to its external surface only. It has also a vaginal and a rectal surface, so that a median section of the perineum would in form resemble a spherical triangle. The distance from the anal to the vulval opening is about three centimetres, or a little more than an inch, according to Spiegelberg. Foster1 found that in the parous this measurement was rather less than an inch, 2.7 centimetres, but in the nulliparous somewhat more than an inch. The hypertrophy of pregnancy may increase this measure- ment to an inch and a half, or four centimetres. In labor the perineum may be so stretched by the presenting part as to measure five inches and a half, or fourteen centimetres. It is generally held that this dis- tensibility depends upon an irregularly limited mass of elastic tissue and muscular fasciculi situated midway between the posterior commis- sure of the vulva and the anus, known, since the investigations ot Henle and Savage, as the perineal body. According to Savage,2 the greatly stretched perineal body is the final covering of the presenting 1 American Journal ot Obstetrics, 18S0. Anatomy of the Female Pelvic Organs,