which are exceedingly interesting when viewed in reference to the formation of sinuses and abscesses, to effusions of urine, and to the dangers attending operations for the removal of calculi from the bladder, or for any other purpose. The great importance of a knowledge of the anatomy of the perineum should be impressed on the mind of every student independently of the idea of his ever being called upon to operate for calculi in the bladder. Very few in the profession ever have an opportunity to cut for stone, while every physician is liable to meet with cases of sinuses, abscesses, and fistulous openings in this region, which he should be able to treat properly.

To dissect the perineum, the subject must be placed on the back near the end of the table, with a small block under the pelvis. The thighs must be flexed and separated from each other; to keep them in this position, the feet may be fastened by a roller or a cord to the wrists; or a cord may be attached to one of the thighs near the knee, carried under the table and fastened in the same manner to the opposite thigh. If a cord of sufficient length be used, with blocks to support the thighs, the student will have no difficulty in placing and keeping the subject in a favorable position for making his dissection. The rectum should be thoroughly washed out and moderately and evenly distended with tow, cotton, or a piece of a roller gradually introduced into it. The scrotum should be drawn upwards and fastened by hooks.

The first thing to be done in the dissection is to remove the skin. To do this make an incision from the coccyx to the anus, and thence to the raphé of the scrotum; and another from the nates on each side to the anus. In this way the integument may be raised in four flaps. The skin is so thin at the margin of the anus that some care is requisite to raise it and leave the superficial fascia.

The common superficial fascia usually contains a large quantity of adipose substance, especially in the ischio-rectal fossa, spaces situated, one on each side of the anus and lower part of the rectum. This fascia is continuous with the superficial fascia of the parts contiguous to the perineum, and must not be confounded with the superficial perineal fascia. To remove it the same incisions may be made as were made to raise the skin. Before doing this, however, the vessels

and nerves which ramify in it should be observed; also the boundaries of the ischio-rectal fossa.

The arteries which supply the perineum are derived principally from the internal pudic, a branch of the internal iliac artery. The course of this artery is deep seated, and will be noticed at an advanced stage of the dissection. The principal branches involved in the removal of the common superficial fascia are the inferior hemorrhoidal, Fig. 194 (10). These vary in number from one to three on each side. They pierce a layer of the obturator fascia which covers the internal pudic artery, and pass transversely, or nearly so, across the ischio-rectal fossa to the anus. They supply the lower part of the rectum, including the levator and sphincter ani muscles, and the integument around the anus. They are surrounded by the adipose substance which fills the ischio-rectal fossa. The student cannot be too particular in obtaining an accurate knowledge of the position of these vessels. The subcutaneous branches in the anterior part of the perineum are not of sufficient importance to require any special notice here. They consist of small branches of the superficial perineal artery, which is also a branch of the internal pudic, arising from it just after the hemorrhoidal are given off.

The veins correspond to the arteries and require no particular notice.

The nerves of the perineum are mainly supplied by the internal pudic, which enters this region in company with the internal pudic artery; and its distribution is nearly the same as that of the artery. It sends hemorrhoidal branches to the lower part of the rectum, and to the levator and sphincter ani muscles. One of its principal divisions is called the superficial perineal nerve, Fig. 195 (2), which passes forwards in company with the superficial perineal artery. In the anterior part of the perineum this nerve becomes subcutaneous and is distributed to the skin in that region and to the scrotum. A small branch, derived from the small sciatic nerve, is also distributed to the integument of the perineum and scrotum; principally, however, to the latter.

Before examining the boundaries and relations of the ischio-rectal fossa, the sphincter ani and coccygeus muscles may be studied.

A VIEW OF THE MUSCLES OF THE PERINEUM OF THE MALE.-1, 1. Rami of the ischia. 2, 2. Tuberosities of the ischia. 3. Posterior face of the coccyx. 4. Portion of the great sacro-sciatic ligament. 5. Accelerator urinæ. 6. Erector penis. 7. Transversus perinei. 8. Sphincter ani. 9. Levator ani. 10. Musculus coceygeus. 11. Section of the gluteus maximus. 12. Adductor longus. 13. Adductor brevis. 14. Adductor magnus. 15. Gluteus maximus. 16. The urethra. 17, 17. Corpora cavernosa turned up. 18. Spermatic cord turned up. 19. Free extremity of the penis with its integuments.

neous areolar tissue, and to a fibrous structure just in front of the anus, called the perineal centre, to which the transversi perinei and the acceleratores urinæ muscles are also attached. It surrounds the lower orifice of the rectum; is narrow and somewhat pointed before and behind this opening, but an inch or more broad on each side of it. It presents an upper and a lower border. The lower one is separated from the skin by a very thin layer of areolar tissue, while the upper one is blended with the fibres of the levator ani. The outer surface is in apposition with the adipose tissue contained in the ischio-rectal fossa. It closes the anus and at the same time slightly elevates it; it also assists the transversi perinei in fixing the perineal centre.

DISSECTION OF THE PERINEUM.

The COCCYGEUS, Fig. 193 (10), is situated between the pyriformis and the posterior border of the levator ani. It arises from the spine of the ischium and from the small sacrosciatic ligament, and is inserted into the side of the coccyx

Fig. 194.

THE ARTERIES OF THE PERINEUM; ON THE RIGHT SIDE THE SUPERFICIAL ARTERIES ARE SEEN, AND ON THE LEFT THE DEEP.-1. The penis, consisting of the corpus The crus penis on the left side is cut through. spongiosum and corpora cavernosa. 2. The acceleratores urinæ muscles, inclosing the bulbous portion of the corpus spongiosum. 3. The erector penis, spread out upon the crus penis of the right side. 4. The anus, surrounded by the sphincter ani muscle. 5. The rami of the ischium and pubes. 6. The tuberosity of the ischium. 7. The small sacro-sciatic ligament attached by its small extremity to the spine of the ischium. 8. The coccyx. 9. The internal pudic artery, crossing the spine of the ischium, and entering the perineum. 10. Inferior hemorrhoidal branches. 11. The superficial perineal artery, giving 13. The artery of the bulb. 14. The two off a small branch, transverse perineal, upon the transversus perinei muscle. 12. The same artery on the left side cut off. terminal branches of the internal pudic artery; one is seen entering the divided extremity of the crus penis, the artery of the corpus cavernosum; the other, the dorsalis penis, ascends upon the dorsum of the organ.

and the lower part of the sacrum. It is of a triangular form; and its attachments are aponeurotic. Its inner and upper surface corresponds to the rectum. Its action is to keep the coccyx in its proper place, and to assist in forming the floor of the pelvis.

The ISCHIO-RECTAL FOSSA is wedge-shaped, and is from an inch and a half to two inches deep. The thin edge looks upwards and corresponds to the splitting of the pelvic fascia into the levator or anal fascia on the inner side, and the obturator fascia on the outer side. The base or thick edge looks

downwards, and corresponds to the integument. The inner boundary is formed below by the sphincter ani and above by the levator fascia, which covers the levator ani muscle; while the outer boundary is formed below by the gluteus maximus, and above by the obturator fascia, which covers the obturator internus muscle. The anterior boundary is formed by a reflection of the superficial perineal fascia upwards to join the deep perineal fascia; as the superficial perineal fascia is reflected upwards it is joined to the anterior border of both the obturator and the levator fascia. Thus it will be seen that the ischio-rectal fossa is bounded on three sides by fascia, especially the upper part of it. The posterior boundary corresponds to the gluteus maximus and coccygeus muscles, and to the sacro-sciatic ligaments and foramina.

When the contents of the ischio-rectal fossa have been removed and its boundaries carefully observed, the student should endeavor to obtain a distinct idea of its relations to the cavity of the abdomen. He should do this before he has attempted to master the anatomy of that portion of the perineum which belongs to the genito-urinary apparatus. As the ischio-rectal fossa is now fairly exposed, a part of the levator fascia should be carefully removed from the levator muscle. Having done this, a portion of the muscle should also be dissected away when another fascia, the pelvic, will be observed. Remove a portion of this and the sub-peritoneal areolar tissue together with the peritoneum itself will be seen. Thus a clear idea of what separates the abdominal cavity from the ischio-rectal fossa will be obtained. It will be seen that, besides the peritoneum and the sub-peritoneal areolar tissue, the bowels are separated from the ischio-rectal fossa simply by the levator ani muscle and the fascia that cover its pelvic and perineal surfaces.

It will now also be observed that the pelvic fascia, Fig. 199 (s), as it descends from the brim of the pelvis, divides into three layers. These are the obturator (13), the levator or anal (15), and the recto-vesical (8, 11). The first descends on the obturator internus muscle, and is attached below to the ramus and tuberosity of the ischium, and to the great sacro-sciatic ligament; the second passes downwards on the perineal surface of the levator muscle to the upper border of the sphinc ter ani, where it is frequently so thin that it hardly deserves