The surgical anatomy of the principal regions of the human body

Front matter

COLLINSON, Ij Bookbinder^ &

MANSFIBLD. ^

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CHAPTER I. DISSECTION OF THE PERINiEUM

Where it is in the power of the dissector to select a subject, he will find it of considerable advantage to make choice of the body of a muscular adult who has died of some lingering disease ; more particularly so when it is his intention to study with exactness the numerous and important vessels and fascim which are situated within the boundaries of this region. It is by no means an easy task to make even a tolerably satisfactory display of these structures when the subject is much loaded with fat.

Previously to fixing the subject in the position which is best suited for the dissection of the perinseum, it is strongly recommended that the introduction of the catheter both in the curved and straight forms should be practised, and the several modes of effecting its introduction compared with one another ; and also the most likely means of avoiding the natural obstacles which the many irregularities of the internal surface of the urethra and the structures that surround the canal are capable of presenting to the easy passage of the instrument. When the subject has been tied up in the usual position, with the thighs widely separated, it is frequently extremely difficult to introduce a catheter or staff without using a considerable degree of force, and running a great risk of lacerating the lining membrane of the urethra, and thus making a false passage ; accidents wliicli ought to be avoided, as they will interfere with the perfect display of the parts in the dissection which is about to be made.

After the catheter has been introduced into the bladder, it should be allowed to remain there, while an examination of the prostate gland and the neck of the bladder is made from the rectum by means of the forefinger of the left hand introduced by the anus into that intestine. It will be found, as soon as the extremity of the finger has entered a little way within the anus, that the calibre of the rectum becomes suddenly very much enlarged; and this more particularly so in elderly subjects, and in those who have suffered in their lifetime from habitual constipation. When the palmar surface of the finger is directed against the anterior or upper wall of the bowel, that part of the catheter which rests in the membranous portion of the urethra will be readily distinguished, since the thickness of the structures that intervene between the finger and the catheter is very inconsiderable ; at the same time, it will be readily conceived that the coats of the rectum are in very great danger of being cut in the lateral operation of lithotomy, unless the edge of the knife is carefully directed downwards and outwards, at the time when the membranous portion of the urethra is opened, previously to passing the knife along the groove of the staff into the bladder.

Introducing the finger a little farther into the rectum, still keeping it applied against the anterior surface of the intestine, the prostate gland will be perceived by its greater thickness, and by the sense of resistance which its firm and dense structure offers to the finger when it is compressed between it and the catheter. By carrying the finger a little to the side of the mesial line, a much larger proportion of the prostate gland may be felt, which is owing to the greater size of its lateral lobes.

Beyond the base of the prostate gland the catheter is again felt more distinctly through the thin coats of the base of the bladder ; this is the spot that is selected by the surgeon for entering the trocar when he punctures the bladder from the rectum for the relief of cases of complete retention of urine, and in which the prostate gland is not much enlarged.

In persons who are far advanced in years, the prostate gland

DISSECTION OF THE PERINiEUM.

is not iinfrcquently found to be miicli increased in size, and also to be almost suiTOunded, so to speak, by the rectum ; as tlie bowel, instead of lying simply underneath the gland, rises very considerably upon each side of it, and in such a manner as to invest it for two-thirds, and sometimes even more, of its circumference : this is a circumstance that is worthy of being borne in mind during the performance of the lateral operation of lithotomy upon aged individuals.

It is by examining the prostate gland in this manner, with his finger introduced into the rectum, that the surgeon is enabled to determine whether it is diseased or not ; and he is enabled by the same means to direct the point of the catheter with greater certainty in cases where the introduction of it has been rendered more than usually difficult by any injury or disease of the membranous and prostatic portions of the urethra. With the fingers introduced into the rectum, it is possible sometimes to determine the weight and fisfure of a calculus more accurately than by any other means, and to facilitate the seizing of the stone by the forceps after the operation of lithotomy has been performed in cases where the calculus lies deeply behind the prostate gland in the bas-fond of the bladder. It is from the close connections that exist between the rectum and the membranous and prostatic portions of the urethra that the recto-vesical operation of lithotomy derives its simplicity and easy execution ; though for other reasons, that will be noticed in another part of this work, it is an operation which has not been very favourably entertained by the profession.

Position of the subject. — When these preliminary steps have been taken, the catheter may be removed, and a full-sized staff introduced into the bladder; after which, the subject is to be fixed in the usual position as when the operation of lithotomy is about to be performed, which is done by bending the legs and thighs upon the trunk, and then tying the hands and feet together with bandages. The penis and scrotum are next to be tied up to the handle of the staff, in such a manner as that they shall not obscure the view of the perinseum : the buttocks of the subject ought to be made to project a little beyond the edge of the table upon which it lies ; and, if it should be considered to be necessary, they may be elevated a little

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DISSECTION OF THE PERIN.EUM.

more by placing a block of wood imderneatli the sacrum. The rectum is to be moderately distended with a little cotton wool introduced into the anus. Before commencing the incisions of the skin, which are necessary for the exposure of the subjacent structures, it will be found of great use to refer for a moment to a dried preparation of the bones and ligaments of the pelvis, in order to determine more accurately upon the recent subject the osseous boundaries of the perinoeal region. As continual reference will be made in the course of the dissection to the bones of the pelvis, the dried preparation should be placed upon the table so as to be near at hand.

Extent of the perincEal region. — Anatomists have differed much from each other in their description of the extent and boundaries of the perinseum, and the greater number perhaps have restricted the application of the term to the space which is included between the posterior fold of the scrotum and the anus. More lately, however, it has become the custom to include the anal region also ; and then the boundaries of the perinaeum will extend from the arch of the pubis, which is in front, to the tip of the coccyx and the great sacro-sciatic ligaments behind ; the branches of the ischia and ossa pubis, and the tuberosities of the former bones, will form its limits laterally.

In the recent subject the inferior edge of the large gluteal muscles may be added, as forming a part of the postero-lateral boundary. In this manner of viewing it, the perinseal region will present an ovoid figure, the largest extremity of which is directed backwards, and the narrow or elongated one anteriorly. If a line is drawn transversely between the tuberosities of the ischia, the perinseal region will be divided into two compartments of nearly equal size : that which is posterior to this line will contain the anus, with the inferior portion of the rectum ; while that in front of it will comprise the urethra and the root of the penis, together with the numerous structures which arc connected with them. The first of these may be termed the anal, and the second the urethral division of the perinaeal region.

The urethral division, or the perinseum strictly so called, may be said to present the form of a triangle, the base of which, represented by the transverse line drawn between the tuberosities of the ischia, is a little less in its extent than the

DISSECTION OF THE PERINiEUM.

sides, tlic lengtli of tlie sides being from tliree inches to three inches and a half; while the base scarcely equals three inches, and most frequently is rather less.* The raphe or central line of the body will subdivide this triangular space into two smaller triangles, which are of equal size, within one of which the first incisions of the lateral operation of lithotomy must commence.

The external surface of the perinajum is convex anteriorly from side to side, which is owing to the prominence of the bulb of the urethra ; but between the tuberosities of the ischia it is more or less excavated, especially where the anus is situated. The skin is thin and delicate, and easily moveable upon the subjacent structures, which requires that it should be fixed with the fingers of the left hand while the first incisions of lithotomy are being made. Generally the perinseum is more or less covered with hair, wdiich ought to be removed with the razor previously to the performance of any operation upon this region. There are numerous follicles which open upon the surface of the skin, especially around the circumference of the anus ; these follicles frequently inflame and suppurate, forming small abscesses, which might be mistaken for a fistula in ano. In front of the anus the raphe or central elevation of the skin is particularly distinct where it extends forwards towards the scrotum. It is upon the left side of the raphe, and about one inch in front of the anus, that the first cut of the lateral operation of lithotomy is usually commenced, which is carried in an oblique direction downwards and outwards between the anus and the tuberosity of the ischium, a little nearer, however, to the latter point than to the anus. The length of this incision is from two to three inches.

In the bilateral operation of lithotomy the external incision commences on the right side, between the tuberosity of the ischium and the anus ; and is carried across the perinseum in a semicircular direction, until it is made to terminate opposite to the point at which it was begun. The centre of the incision should be

^ In twenty-three subjects which he examined for this purpose, Dupuytren found the base of the urethral portion of the perineeum of very variable extent; in some cases not exceeding two inches, and in others being as much as three inches and a half. Velpeau has seen the tuberosities of the ischia as near to one another as If inch. In my own observations I have seldom found the base to exceed 2^ inches.

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DISSECTION OF THE PERINEUM.

situated about three-quarters of an inch in front of the anus, with the anterior half of the circumference of which its concavity should be made to correspond.

The skin around the anus is of a dark brown hue, and at the margins of this opening it becomes insensibly continuous with the mucous membrane of the rectum : when the anus is closed, the skin is thrown into numerous radiated folds or wrinkles, which arrangement no doubt allows the anus to be largely distended without a rupture of the cutaneous tissues. 1 he interspaces between these folds sometimes become the seat of very troublesome ulcerations in some forms of venereal disease, and cause the patient much pain and annoyance. These ulcerations may nevertheless exist independent of any syphilitic taint, and excite by their irritation such a painful and constant contraction of the sphincter muscle, that it becomes necessary to divide its fibres completely across before a cure can be obtained.

Within the margin of the anus the extremities of the heemorrhoidal veins are usually observed in a varicose state, foiTuing those little tumours which are well known as con stituting the affection termed piles. There are two varieties of these tumours ; one which consists in the simple varicose dilatation of the veins of the intestine ; and the other in which the tumours are in part formed by the veins dilated, and partly by coagula of blood which has become extravasated into the adjacent cellular tissue in consequence of a rupture of the coats of the vessels. The margins of the anus are frequently also the scat of the firm fleshy tumours called condylomata, which consist of a simple hypertrophy of the cellular structure ; and though very commonly the consequence of the irritation of gonorrheal" discharges, yet may exist independently of any specific disease.

Dissection of the Perinaum. — The dissection may be commenced by exposing the superficial fascia and external sphincter muscle of the anus. For this purpose make an incision from the scrotum backwards, following the direction of the raphe of the perinseuin, as far as the anterior margin of the anus, when the edge of the knife must be carried round that aperture, and thus encircle it, where the skin and the mucous membrane of the rectum are blended with one another ; from the posterior margin of the anus a single incision is to be made as far as to tlie coccyx, upon wliicli it may terminate. A notlier incision must be made across from one tuberosity of the iscliium to the other, passing in front of the anus ; the extremities of this last cut should be extended for some distance upon the thighs. These incisions should not be made deeper than is necessary for the dissection of the shin from the subjacent structures. Laying hold of the inner angles of the flaps which have been thus marked out, raise them for a considerable distance on each side, and then reflect them upon the thighs and buttocks, where they may be flxed by means of pins or hooks. While raising the two posterior flaps, the edge of the scalpel must be carried round the anus in the direction of the fibres of the external sphincter muscle, which, being imnicdiately underneath the skin, is at once exposed to view. The fascia lata of the thighs may be displayed a little distance upon each side by removing the thin layer of adipose tissue which covers its external surface, and conceals its attachments to the external margins of the tuberosities and branches of the ischia and ossa pubis. Wliile this is being done, some small nerves, which pierce the fascia lata a little in front of the lower edges of the great gluteal muscles, will be found ; and which, after dividing into several smaller filaments, pass inwards towards the mesial line, supplying the integuments of the perinseal region. These nerves are branehes of the posterior and internal cutaneous divisions of the small sciatic nerves. More posteriorly, a part of the inferior border of the large gluteal muscles may be dissected, and their attachment to the lateral borders of the coccygeal bones and posterior sacro-sciatic ligaments shown.

Between the external margin of the sphincter of the anus and the borders of the tuberosities of the ischia, a large quantity of adipose substance will be observed, which must be next removed in order that the fibres of the levator ani muscles may be exposed, as they descend from the sides of the pelvis towards the extremity of the rectum.^

* In removing the masses of fat -which fill up on each side the space between the anus and the tuberosities of the ischia, the knife should not be carried farther forwards than a line extended across the perinaeum in front of the anus, in order to avoid doing any injury to the superficial fascia where it passes upwards to unite, behind the transverse muscles of the perinaeum, with the deep fascia or triangular ligament of the urethra.

DISSECTION OF THE PERINEUM.

During the removal of this fat, some small arteries which run in its substance should be preserved : these are the external or inferior hsemorrhoidal arteries, branches from the internal pudic vessels, and given off from these as they are running along under cover of the tuberosities of the ischia. They are distributed to the superficial structures around the inferior extremity of the alimentary canal. These little vessels are worthy of attention, as they are frequently divided in the operations of lithotomy and of fistulse in ano, &c. and may sometimes furnish a considerable quantity of blood ; sufficient indeed to render the application of a compress or a ligature necessary, to prevent the continuance of the bleeding.

When all the fat has been removed, a large excavated hollow remains on each side of the anus ; these have been named by M. Velpeau the ischio-rectal fossae. The figure of each of these spaces is triangular, the base being formed by the skin, and the apex or summit by the angle where the fibres of the levator ani separate from the obturator fascia. The internal wall is very oblique, and is formed by the fibres of the levator ani ; the external one on the other hand is nearly perpendicular, and is formed by the obturator fascia and the tuberosity of the ischium.^ The depth of the cavity increases towards the external wall, where it may be estimated at nearly two inches. If the subject has been injected, by placing the finger against the external wall of the cavity, about an inch above the edge of the tuberosity of the ischium, the internal pudic artery can be

* The obturator fascia is a thick and strong membrane, which binds down the obturator internus muscle to the internal surface of that part of the os innominatum, and to the ligament of the thyroid foramen, from which its fibres take their origin. The fascia is attached superiorly to the margins of the thyroid foramen, posteriorly to the spinous process of the ischium, and inferiorly to the falciform process of the great sacro-sciatic ligament, and the rami of the ischium and os pubis. Relations — externally with the obturator interuus muscle ; internally with the pelvic fascia, part of the origin of the levator ani, and the adipose substance which fills the ischio-rectal space. The internal pudic vessels and nerve, as they pass from the smaller sciatic foramen, by which they re-entered the pelvis, to their termination in the branches which they furnish to the bulb, corpus cavernosum, and dorsum of the penis, are inclosed in a sheath, which is formed by the division of the fascia into two lamellae at this point. The inferior heemorrhoidal and superficialis perinaei arteries pierce this fascia immediately after their origin from the trunk.

DISSECTION OF THE PERINiEUM.

felt as it is running along enclosed between the layers of the fascia, accompanied by its corresponding veins and nerve.

It is in the large quantity of adipose tissue which occupies the ischio-rectal fossae, that the greater number of those abscesses form which degenerate into confirmed fistulae in ano. By a reference to the structure of the walls of the ischio-rectal cavity, it will be readily understood why it happens that these fistulse can rarely be cured, except by the division of the external sphincter muscle ; an operation which allows the walls of the fistula to remain at rest, and to unite with one another by the process of granulation.

The superjicial fascia of the perinseum is next to be exposed by removing the layer of adipose and cellular tissue which lies between it and the skin. It is difficult to effect this in corpulent subjects without doing some injury to the fascia, which in such instances is frequently very thin and weak. The best way is to remove the subcutaneous layer carefully by degrees in one spot, until the smooth and regular surface of the fascia is exposed, when it can be followed on each side to its insertions into the edges of the branches of the ischium and ossa pubis, forwards into the scrotum, and posteriorly to its attachment to the triangular ligament of the urethra.

When these directions have been properly executed, the structures which are exposed to view are as follows : surrounding the anus is the external sphincter muscle, in front of which is the superficial fascia of the perinseum ; on each side of the sphincter muscle are the ischio-rectal fossae, emptied of the large masses of adipose tissue which naturally fill them ; the inner walls of the fossae are formed by the fibres of the levator ani muscles, which must be more completely displayed by removing a thin fascia that covers them, and which is a prolongation backwards of the triangular ligament of the urethra : posteriorly are the coccyx, the inferior border of the great gluteal muscles, and, under cover of these, part of the sacro-sciatic ligaments ; externally to the tuberosities of the ischia, a portion of the fascia lata of the thigh is exposed. (See Plate I.)

Before proceeding any further with the dissection, each of these structures should be more closely examined in succession.

The external sphincler of the anus encircles the inferior extremity and orifice of the rectum. The muscle is of an cllipti-

DISSECTION OF THE PERINtEUM.

cal figure, and is composed of two bundles of fleshy fibres, which are united with one another in front and behind the aperture of the anus, at the same time diminishing in their breadth. Posteriorly, the fibres of the muscle are attached to the extremity of the coccyx by means of a narrow fibro-cellular band of about an inch in length ; anteriorly, the fibres are inserted partly into the inferior surface of the superficial fascia, and partly into the central tendinous point of the perinseum. The structure of the muscle is fleshy, except at its attachment to the coccyx, where it is slightly tendinous. In some subjects the muscle is very thick and strong, while in others it is extremely delicate. Relations — interiorly, this muscle is covered by the skin ; superiorly, with the superficial fascia and the levator ani, from which last, however, it is separated by some of the fibres of the triangular ligament of the urethra ; externally, with the adipose tissue which occupies the ischio-rectal fossae ; and internally,

EXPLANATION OF PLATE I.

This represents a dissection of the superficial fascia of the perinaeum : posteriorly, the external sphincter and levatores ani muscles are dissected in order to show the ischio-rectal fossae.

1. 1. The superficial fascia of the perinaeum. This fascia covers the muscles of the penis, and is attached on each side to the edge of the branches of the ischia and ossa pubis ; anteriorly, it is continuous with the dartos of the scrotum.

2. 2. These figures indicate the point where the superficial fascia of the perinaeum passes behind the transverse muscles to become attached to the anterior surface of the triangular ligament of the urethra.

3.3, The fascia lata of the thighs covering the adductor muscles.

4. 4. The tuberosities of the ischia.

5. The coccyx.

a. The external sphincter muscle surrounding the anus, which is stuffed with a little cotton wool. The attachment of the fibres of the muscle upon the inferior surface of the superficial fascia is seen in front; posteriorly, the fibres are connected by a fibro-cellular band to the coccyx.

h. b. The inferior border of the great gluteal muscles, c. c. The levatores ani. Between the tuberosities of the ischia and the anus, are the hollow spaces named by M, Velpeau the ischio-reclul Jbssce.

frurlcinfl . litii ■

.Frinltd Ovlxiirlmid.

DISSECTION OF THE PERINEUM.

with the circular muscular fibres of the intestine, which are here more strongly developed than elsewhere, and which in consequence have been named the sphijicter ani internus. The action of this muscle is to close the extremity of the rectum, and prevent the escape of its contents. It belongs to the class of voluntary muscles, and is supplied by a branch from the pudic nei’ve.

This muscle is cut across in the recto-vesical operation of lithotomy and in the operation for fistula in ano, and occasionally also to promote the cure of painful and obstinate ulcerations near the margin of the anus.

The internal sphincter muscle consists, as has been already mentioned, of the most inferior of the circular fibres of the muscular coat of the rectum, and which are more strongly developed than the rest. Circular in its form, the muscle embraces the mucous membrane of the bowel, and is covered externally by the external sphincter.

The levator ani muscle is but partially seen in this stage of the dissection, as only those of its fibres have been exposed which are attached at the circumference of the muscle to the spinous processes of the ischia, and to the tendinous band which stretches across from them to the posterior surface of the bodies of the ossa pubis ; which band is situated at the summit of the ischio-rectal fossae, in the angle that is formed by the separation from one another of the pelvic and obturator fasciae. The fibres of the muscle are inserted into the sides of the cocevx, and between the extremity of that bone and the anus they are blended with one another by means of a common band of junction, which is situated above the posterior portion of the external sphincter of the anus ; more anteriorly the remaining fibres descend to be inserted between the external sphincter and the muscular coat of the rectum, having attachment to both of these structures. The structure of the muscle is chiefly fleshy, though it is slightly tendinous where it is inserted into the coccyx, and the raphe between the extremity of that bone and the anus.*

The superficial fascia of the perinceum is situated in the anterior or urethral division of the perinseal region, and is a thin

* For a more complete description of this muscle, see page 47.

DISSECTION OF THE PERINEUM.

membranous layer wliicb conceals the muscles of the penis. On each side the fascia is attached to the borders of the branches of the ischia and ossa pubis ; anteriorly it passes forwards into the scrotum, where it appears to become continuous with the dartos ; posteriorly it is inserted into the inferior surface of the triangular ligament of the urethra, behind the posterior border of the transverse muscles of the perineeum, which it covers. The superficial fascia is pierced at various points by some of the small cutaneous branches of the superficial arteries and nerves of the perinseum. Relations — by its inferior surface with the

skin, the subcutaneous layer of adipose tissue, and some of the fibres of the external sphincter muscle which are inserted into it near the mesial line ; by its superior surface with the crura and erector muscles of the penis, the accelerator urinre, and transverse muscles, and with the cellular tissue which fills up the interspaces between them, in which the superficial vessels and nerves of the perinseum ramify.

If a small slit be made into this membrane posteriorly, and the extremity of a blowpipe introduced underneath it, the air which is inflated will be observed, after distending the perinseal portion of the fascia, to pass forwards into the scrotum, and diffuse itself into the loose cellular tissue which separates the dartos from the sheath which the spermatic cords and testicles receive from the margins of the external abdominal rings. If the inflation is continued, the air will, after distending the scrotum, make its way upon the front of the abdomen in the loose cellular tissue which connects the aponeuroses of the external oblique muscles with the superficial fascia of the inguinal and hypogastric regions. It is by following the same course that the urine, which is sometimes extravasated underneath this fascia by a rupture of the anterior part of the urethra, is seen to make its way along the perinseum into the scrotum, and even upon the anterior and lateral parts of the abdominal parietes.* Dissection of the muscles of the penis. — The muscles of the penis may now be exposed by laying open the superficial fascia by a crucial incision, and reflecting to either side the flaps,

* Previously to the description of the superficial fascia by Mr. Colles, of Dublin, it was found difficult to explain the course which the urine pursued when extravasated into the perinaeum, as may be seen by referring to the second Volume of IMr. Abernethy s Surgical Observations, p. 245.

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DISSECTION OF THE PERINEUM.

whicli will sliow more completely the attachments of the fascia to the edges of the arch of the pubis, and the mode in which it incloses the root of the penis and its muscles, as it were, in a sheath. In dissecting the muscles of the penis it is necessary that the edge of the knife should be carried in the same direction as that of their fibres, for they are very delicate and easily injured. While removing the cellular tissue which fills up the space between the accelerator urinae and the erectores penis, the small arteries, which are named superjicialis and Iransversus perin<^i\ branches of the internal pudic arteries, may be also dissected and preserved : — the first of these runs forwards between the erector penis and the accelerator urinae, and the other along the posterior border of the transverse muscle. Each of these arteries is accompanied by corresponding branches of the nerve and veins.