from the corresponding muscle in the male. It has the same origin (viz., from the inner aspect of the pubic arch at the junction of the pubic and ischial rami), and it also divides into two bundles; but these have not the same intimate relation to the urethra. The upper or anterior bundle spreads out upon the upper or anterior surface of the urethra, whilst the lower or posterior bundle spreads out upon the wall of the vagina.

The Vagina will be fully described in connection with the pelvic viscera.

They

Bartholin's Glands.-These glands are the representatives in the female of Cowper's glands in the male. are two round or oblong bodies about the size of a horsebean, placed one upon each side of the entrance to the vagina immediately behind the rounded end of the bulb, and under cover of the sphincter vaginæ. A long duct proceeds from each gland, and opens in the angle between the nympha and the hymen or carunculæ myrtiformes (Fig. 81, p. 367).

Internal Pudic Vessels and Nerve. The internal pudic vessels and nerve have a precisely similar disposition to the corresponding vessels and nerve in the male (p. 358). If anything, they are somewhat smaller.

The student must therefore look for the artery to the bulb, a branch of the internal pudic, which in this case is given to the bulb of the vagina, and the two terminal branches of the internal pudic artery, viz., the dorsal artery of the clitoris, and the artery to the corpus cavernosum.

The internal pudic nerve ends by dividing into the perineal nerve and the dorsal nerve of the clitoris.

The perineal nerve gives off-(1) the anterior and posterior superficial perineal branches to the skin covering the labium majus; (2) muscular twigs to all the perineal muscles; and (3) a branch to the bulb of the vagina.

The dorsal nerve of the clitoris gives a twig to the corpus cavernosum, and runs forwards with the artery of the same name between the crura to reach the dorsum of the clitoris.

Dorsal Vessels and Nerves of the Clitoris.-On the dorsum of the clitoris a little dissection will display the dorsal vein occupying the groove in the middle line, with a dorsal artery and nerve lying upon each side of it.

The arteries and nerves should be traced forwards to their distribution in the glans.

The dorsal vein takes origin in the glans. As it proceeds backwards it receives certain superficial veins and also tributaries from the corpora cavernosa. At the root of the clitoris it dips downwards between the crura, and, passing between the triangular and the subpubic ligaments, is continued backwards into the pelvis to join the plexus of veins around the neck of the bladder.

ABDOMINAL WALL.

On the fifth day after the dissection of the perineum is completed, the body is placed upon its back, with blocks under the chest and pelvis, and the dissectors of the abdomen begin the dissection of the abdominal wall (Fig. 83).

External Anatomy.-It is well, however, before proceeding to the actual dissection of the part, that some attention should be paid to the general configuration and bony prominences of the region. If the subject is obese the abdomen presents a smooth, rounded, and protuberant appearance; if, on the other hand, it is spare, the abdominal wall is depressed, and the lower margin of the thorax above, and the pubes, crest of the ilium and Poupart's ligament below, stand out in marked relief. In the middle line, the student will notice a linear depression extending downwards towards the symphysis. This corresponds with the linea alba or the interval between the two recti muscles. It is a most important line to the surgeon, because here the wall of the abdomen is thin and devoid of blood-vessels, and, in consequence, it is chosen as the site for the incisions in the operations of ovariotomy, Cæsarean section,

and suprapubic lithotomy. In the same line the trocar is introduced into the abdomen in the operation of paracentesis abdominis or tapping.

In this linear depression, rather nearer the pubes than the ensiform cartilage, is the umbilicus or navel. This is a depressed and puckered cicatrix, the floor of which is raised in the form of a little button-like knob. It results from the closure of an opening in the abdominal wall of the fœtus, through which passed the constituents of the umbilical cord-viz., the umbilical vein, the two allantoic or hypogastric arteries, and the urachus.

In powerful well-developed subjects the rectus muscle stands out on each side of the middle line, and its outer margin gives rise to a curved line, the concavity of which is directed inwards. This line corresponds to the linea semilunaris-i.e., the line along which the aponeurotic tendon of the internal oblique muscle splits to enclose the rectus. The linea semilunaris is also frequently selected by the surgeon as the site for incisions through the abdominal wall.

The student should now place his finger upon the upper part of the symphysis pubis and carry it outwards, over the pubic crest, to the pubic spine; from this he should follow the line of Poupart's ligament to the anterior superior spine of the ilium, and, having identified these parts, let him next endeavour to determine the position of the external abdominal ring. This is easily done in a male subject. Immediately external to the spine of the os pubis the spermatic cord can be felt as it passes over Poupart's ligament to reach the scrotum. Taking this as a guide, push the loose skin of the scrotum upwards before the finger. The tip of the finger enters the opening, the sharp margins of which can now be felt.

The spermatic cord, as it passes downwards into the scrotum, should be taken between the finger and thumb. On pressure being applied the vas deferens can be easily distinguished at the back of the cord, by the hard whipcord-like feel that it conveys to the fingers.

The crest of the ilium, as it proceeds upwards and backwards from the anterior superior spine, can be easily felt. Indeed, in most cases it is visible to the eye for a distance of about two and a half inches. At the point where it disappears from view a prominent tubercle is developed on its outer lip, and it is here that the outline of the trunk joins the ilium. It is the highest point of the iliac crest, therefore, that can be seen from the front. As we shall see later on, use is made of this fact in subdividing the abdominal cavity into regions.

In females who have borne children the skin over the lower part of the abdomen is wrinkled and scarred.

Parts to be dissected.-A dissection of the abdominal wall will display the following parts :—

1. Superficial fascia.

2. Cutaneous vessels and nerves.
3. The external oblique muscle.

4. The internal oblique muscle.

5. The lower six intercostal nerves and accompanying vessels ; the ilio-inguinal and ilio-hypogastric nerves.

7. The rectus and pyramidalis muscles and the sheath of the

rectus.

8. The transversalis fascia.

9. The deep epigastric and deep circumflex iliac arteries.
10. The superior epigastric and musculo-phrenic arteries.

II. The spermatic cord.
12. The inguinal canal.

13. The extra-peritoneal fat.

14. The parietal peritoneum.

Reflection of Skin.-Incisions-(1) Along the middle line of the body from the ensiform cartilage to the symphysis pubis. At the navel the knife should be carried round so as to surround it with a circular incision. (2) From the ensiform cartilage transversely outwards around the chest, as far back as the knife can be carried. (3) From the symphysis pubis outwards along the line of Poupart's ligament to the anterior superior spine of the ilium, and then backwards along the crest of the ilium (Fig. 83).

The large flap of skin thus mapped out should be carefully raised from the subjacent superficial fascia and turned outwards. If the abdominal wall is flaccid, the dissection may be facilitated by inflating the abdomen. Make an incision through the umbilicus large enough to admit the nozzle of the bellows, and when the walls are quite tense secure the opening with twine, which has previously been sewn round the lips of the incision.

The Superficial Fascia.-The superficial fascia which is now laid bare is seen to present the same appearance, and possess the same characters as in other localities. Above, it is thin and weak, and is directly continuous with the corresponding fascia over the chest. Following it downwards, it will be noticed to become more strongly marked, and to acquire a greater density. Towards the lower part of the abdomen it consists of two layers-a fatty superficial stratum called Camper's fascia, and a deep membranaceous stratum termed Scarpa's fascia.

There is another point, however, in which the superficial fascia differs somewhat from the same fascia in other parts of the body. It is more elastic, and this elasticity is due to the presence of elastic fibres in its deeper membranaceous part. Over the lower part of the linea alba the elastic tissue is generally seen collected in the form of a distinct band. A reference to comparative anatomy gives interest to this fact. In the human subject this elastic band is the rudimentary representative of a continuous and distinct layer of yellow elastic tissue (the abdominal tunic), which is present in the horse.