ISCHIO-RECTAL FOSSA.-LITHOTOMY.

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endangered. The part of the intestine now under observation rests against the conjoined levatores ani, the coccyx, and the sacrum.

The lower end of the rectum receives small arteries on each side from the pudic; but its principal artery (the superior hæmorrhoidal, the continuation of the inferior mesenteric, p. 412,) descends behind the organ and ends in branches about three inches from the anus, which enter the gut and anastomose in loops opposite the internal sphincter. The veins, like those of the abdomen generally, are without valves. These vessels are very liable to enlarge and become varicose; and this condition is constantly associated with or even forms a great part of the disease known as hæmorrhoids.

Ischio-rectal fossa.-On each side of the rectum between it and the ischial tuberosity is contained a considerable quantity of fat, the space which it occupies being named the ischio-rectal fossa. This hollow extends backwards from the perinæum to the great gluteal muscle; it is bounded on the inner side by the levator ani as this muscle descends to support the intestine, and on the opposite side by the obturator fascia and muscle supported by the hip-bone. At the outer side and encased in a sheath of the obturator fascia is the pudic artery with the accompanying veins and nerve; and small offsets from these cross the fossa to supply the lower end of the rectum. The pudic artery, it will be observed, is about an inch above the lower surface of the tuber ischii, and at the same time, by its position under that prominence of the bone, it is protected from injury by incisions directed backwards from the perinæum; but in front of this part (in the perinæum proper), inasmuch as the vessel lies along the inner margin of the subpubic arch, it is here liable to be wounded when the deeper structures of the perinæum are incised.

The fossa is narrowed as it reaches upwards into the pelvis ; such narrowing of the space is the necessary result of the direction of the levator ani, which drops inwards from the fascia on the side of the pelvis, and thus limits the fossa at its upper end.

LATERAL OPERATION OF LITHOTOMY.

The intention of the operation, as it is usually performed, is to remove a calculus from the urinary bladder by an opening made through the perinæum and the prostatic part of the urethra. The incisions to attain

this end are commonly made on the left half of the perinæum : because this side is most convenient to the right hand of the operator; but if the surgeon should operate with the left hand, then the opposite (right) side of the perinæum would be most convenient.

The position at which the perinæum is to be incised requires careful consideration. For if the necessary incisions should be made too near the middle line of the body, the bulbous enlargement of the corpus spongiosum urethræ and the rectum are liable to be wounded; and if, on the other hand, the perinæum should be divided towards its outer boundary (the pubic arch), there is a risk of wounding the pudic artery where that vessel has reached the inner edge of the bone. The incisions are therefore to be made through the area of the small perineal space in such manner as to avoid both its sides. Again, as to the length to which the several structures are to be incised :-The integument and the subcutaneous fatty layer must be divided with freedom, because, first, the skin does not admit of dilatation during the removal of the foreign body; and, secondly, extensive incisions through the structures near the surface facilitate the egress

of urine, which, after the operation, continues for a time to trickle from the bladder. But the prostate and the neck of the bladder, on the contrary, are to be incised only for a small extent. The reasons for this rule may be stated as follows :-By accumulated experience in operations on the living body, it has been found that the structures now under consideration, when slightly cut into, admit of dilatation, so as to allow the passage of a stone of considerable size, and that no unfavourable consequence follows from the dilatation. Moreover, when these parts are freely divided (cut through), the results of lithotomy are less favourable than in the opposite circumstances. The less favourable results adverted to appear to be due to the greater tendency to infiltration of urine in the subserous tissue of the pelvis; and the occurrence of this calamity probably depends on the fact that when the prostate has been fully cut through, the bladder is at the same time divided beyond the base of the gland, and the urine then is liable to escape behind the pelvic fascia (which it will be remembered is connected with both those organs at their place of junction); whereas if the base of the gland should be left entire, the bladder beyond it is likewise uninjured, and the urine passes forwards through the external wound.

The steps of the operation by which the foregoing general rules are sought to be carried out are the following :-The grooved staff having been passed into the bladder (and this instrument ought to be of as large size as the urethra will admit), and the body or the patient, as the case may be, having been placed in the usual position-by which position the perinæum is brought fully before the operator with the skin stretched out-the first incision is begun about two inches before the anus, a little to the left of the raphe of the skin, and from this point it is carried obliquely backwards in a line about midway between the tuber ischii and the anus, extending a little way behind the level of the latter. During the incision, the knife is held with its point to the surface, and it is made to pass through some of the subcutaneous fatty layer as well as the skin, Now, the edge of the knife is applied to the bottom of the wound already formed, in order to extend it somewhat more deeply; and the fore-finger of the left hand is passed firmly along for the purpose of separating the parts still farther, and pressing the rectum inwards and backwards out of the way. Next, with the same finger passed deeply into the wound from its middle and directed upwards, the position of the staff is ascertained, and the structures still covering that instrument are divided with slight touches of the knife,-the finger pressing the while against the point at which the rectum is presumed to be. When the knife has been inserted into the groove of the staff (and it reaches that instrument in the membranous part of the urethra) it is pushed onwards through the prostatic portion of the canal with the edge turned to the side of the prostate, outwards, or, better, outwards with an inclination backwards. The knife being now withdrawn, the forefinger of the left hand is passed along the staff into the bladder. With the finger the parts are dilated, and with it, after the staff has been withdrawn, the position of the stone is determined and the forceps is guided into the bladder.

In case the calculus is known to be of more than a moderate size, and the knife used is narrow, the opening through the side of the prostate may be enlarged as the knife is withdrawn, or the same end may be attained by increasing the angle which that instrument, while it is being passed onwards, makes with the outer part of the staff. And if the stone should be of large size, it will be best to notch likewise the opposite side of the prostate before

LATERAL OPERATION FOR LITHOTOMY.

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the forceps is introduced. The same measure may be resorted to afterwards should much resistance be experienced when the foreign body is being extracted. Lastly, this part of the operation (the extraction of the stone)

Fig. 718.-VIEW OF THE DISTRIBUTION OF THE ARTERIES TO THE VISCERA OF THE MALE PELVIS, AS SEEN ON THE REMOVAL OF THE LEFT OS INNOMINATUM, &c. (from R. Quain). a, left external oblique muscle of the abdomen divided; b, internal oblique; c, transversalis; d, d, the parts of the rectus muscle divided and separated; e, psoas magnus muscle divided; f, placed on the left auricular surface of the sacrum, points by a line to the sacral plexus of nerves; g, placed on the os pubis, sawn through a little to the left of the symphysis, points to the divided spermatic cord; h, the cut root of the crus penis; i, the bulb of the urethra; k, elliptical sphincter ani muscle; 7, a portion of the ischiun near the spinous process, to which is attached the short sacro-sciatic ligament; m, the parietal peritoneum : n, the upper part of the urinary bladder; n, n', the left vas deferens descending towards the vesicula seminalis; n", the left ureter; o, the intestines; 1, the common iliac at the place of its division into external and internal iliac arteries; 2, left external iliac artery; 3, internal iliac; 4, obliterated hypogastric artery, over which the vas deferens is seen passing, with the superior vesical artery below it; 5, middle vesical artery; 6, inferior vesical artery, giving branches to the bladder, and descending on the prostate gland and to the back of the pubes; 7, placed on the sacral plexus, points to the common trunk of the pudic and sciatic arteries; close above 7, the gluteal artery is seen cut short; 8, sciatic artery cut short as it is escaping from the pelvis ; 9, placed on the rectum, points to the pudic artery as it is about to pass behind the spine of the ischium; ', on the lower part of the rectum, points to the inferior hæmorrhoidal branches; 9", on the perinæum, indicates the superficial perineal branches; 9", placed on the prostate gland, marks the pudic artery as it gives off the arteries of the bulb and of the crus penis; 10, placed on the middle part of the rectum, indicates the superior hæmorrhoidal arteries as they descend upon that viscus.

should be conducted slowly, so as gradually to dilate the parts without lacerating them; and the forceps should be held with its blades one above the other.

The Structures divided in the Operation.-In the first incision the integument and the subjacent fatty layer are divided; afterwards a small part

of the accelerator urinæ, and the transversus perinæi with the transverse artery. Then the deep perineal fascia with the muscular fibres between its layers, the membranous part of the urethra, the prostatic part of the canal, and, to a small extent, the prostate itself are successively incised.

The Blood-vessels: their relation to the incisions.-The transverse artery of the perinæum with, it may be, the superficial artery of the perinæum, is the only artery necessarily cut through when the vessels have their accustomed arrangement; for in such circumstances the artery of the bulb is not endangered if the knife be passed into the staff in a direction obliquely upwards, the artery being anterior to the groove of that instrument; neither is there a risk of wounding the pudic artery, unless the incisions through the deep parts (the prostate for instance) should be carried too far outwards. *

But in some cases the arteries undergo certain deviations from their accustomed arrangement, whereby they are rendered liable to be wounded in the operation. Thus, the artery of the bulb when it arises, as occasionally happens, from the pudic near the tuber ischii, crosses the line of incision made in the operation.† The arterial branches ramifying on the prostate are in some instances enlarged, and become a source of hæmorrhage,‡ and the veins, too, on the surface of that gland, when augmented in size, may give rise to troublesome bleeding. § Lastly, it should be added that the occasional artery (accessory pudic), which takes the place of the pudic when defective, inasmuch as it lies on the posterior edge of the prostate, might be divided if the gland were cut through to its base, and only in this event. ||

* For reference to some cases in which the pudic artery was divided in lithotomy, see Crosse's "Treatise on Urinary Calculus," p. 21. London, 1835.

The Anatomy of the Arteries," &c., by R. Quain, p. 442, and plate 64†, figs. 1 and 2. A case in which death resulted from division of the artery of the bulb is recorded by Dr. Kerr, in the "Edinb. Med. and Surg. Journal," July, 1847, p. 155.

See an essay, entitled "Remarks on the Sources of Hæmorrhage after Lithotomy," by James Spence, in the "Edinburgh Monthly Journal of Medical Science,” vol. i. p. 166; 1841. And The Arteries," &c., by R. Quain, p. 445.

"The Arteries," &c., by R. Quain, p. 446, and plate 65, fig 3.

|| Ibid. p. 444, and plate 63. An instance in which fatal consequences resulted from the division of such an artery has been placed on record. See "Case of Lithotomy attended with Hæmorrhage, by J. Shaw, in "The London Medical and Physical Journal," vol. Iv. p. 3, with a figure. 1826.

DIVISION III.

DISSECTIONS.

THE object of the following Directions is to serve as a short and simple guide for the display of the structure of the body by students in dissectingrooms, the various organs and their parts being mentioned in the crder in which they may best be exposed, and such methods being indicated as may enable each student to obtain the greatest amount of information from his dissection, and at the same time to prevent interference among the neighbouring dissectors as much as possible.

I. GENERAL MANAGEMENT OF THE DISSECTIONS.

1. In different schools various plans are pursued in the allotment of portions of the body to different dissectors. According to the method here recommended, the subject is divided into ten parts, five on each side of the body, which are left in connection with one another until the dissection is sufficiently advanced to admit of their being conveniently separated. The boundaries of the parts are so adjusted, that by their due observance interference between the different dissectors may be as much as possible avoided.

2. In the case of a male subject, a day is recommended to be set apart at the commencement for the dissection of the perinæum. Thereafter, and in the case of a female subject, immediately on its being brought into the rooms, the subject is to be placed with the face downwards for four days, during which time the posterior regions are to be dissected, in so far as within reach, in the order afterwards mentioned for each part. It is then to be turned and laid upon its back, when a dissection of the various parts in front is to be made. The whole dissection is supposed to be completed within six weeks,—the time fixed by the Anatomy Act.

3. The dissection of the head and neck and of the limbs should be begun at once when the subject is laid upon its face; that of the abdomen as soon as it is turned on the back, and the thorax must not be opened until the upper limbs are removed. The limbs ought not to be removed until the parts which connect them with the trunk have been fully dissected, and an opportunity has been given for the examination of the surgical anatomy of the subclavian artery and the parts concerned in hernia, by the dissectors of the head and the abdomen; all of which may be accomplished before the tenth day. The further dissection of the several parts may then proceed in accordance with the methods suggested in the special directions.