The bladder presents to our notice three diameters, viz. the transverse, antero-posterior, and the vertical ; the latter is also called its axis. In the contracted state the antero-pos terior can scarcely be considered as existing ; but when distended, this and the transverse diameters are nearly equal. In all states, at least in the male, the vertical diameter or axis is the longest ; this line leads in the adult from the centre of the upper region to that of the lower region or fundus : in the fcetus and infant it leads from the urachus to the orifice of the urethra ; if this line be contrasted with the axis of the trunk or abdomen, and with that of the pelvis, it will be found to correspond very nearly with the direction of the latter, and to pass very obliquely with respect to the former. The axis of the trunk may be regarded as nearly a vertical line, descending through the thorax and abdomen to the pubis, whereas the axis of the pelvis, or rather of its superior orifice, will pass obliquely downwards and backwards, and if produced at either end, it will pierce the recti muscles between the um bilicus and pubis anteriorly, and the lower end of the sacrum posteriorly. The vertical axis of the bladder in the adult is on a lower plane, but nearly parallel to that line ; in the fcetus it is more parallel to that of the trunk, the blad der at that age being placed more in the ab domen, and in a more vertical direction than in the adult.
The bladder is composed of several mem branous laminae, called coats or tunics : these are essentially three in number, a serous, a muscular, and a mucous. They are connected together by cellular tissue, the laminae of which being two in number are also considered coats ; so that the whole number of tunics is stated by most writers as five. First, the serous or peritoneal is but a partial coat ; it covers those portions only which come in contact with some of the abdominal or pelvic viscera, namely, all the posterior region, and the posterior portions of the lateral, and of the superior and inferior regions ; consequently it is deficient on all the anterior region, and on the anterior part of the superior, and of the lateral and inferior regions. The course of the vasa deferentia marks the extent or the limits of this mem brane on the bladder; all that portion which is behind and between these tubes is covered by it, except the small triangular area already noticed on the inferior region; all that which is anterior to these vessels is uncovered by this membrane. The peritoneum arrives at this viscus from the fore-part of the rectum in the male, and from that of the uterus in the female, and is continued from its lateral regions to the iliac fossae, and from its superior fundus to the inside of the recti muscles. This membrane is not very closely attached to the subjacent coat ; it can be easily separated from it ; it is much stronger and more elastic on this organ than on any of the chylopoietic viscera. When the bladder is distended, there is more in pro portion covered by peritoneum than when it is contracted. The female bladder has more of the peritoneum on its upper fundus, and less on its lower fundus than the male bladder, and in the fcetus and infant it is still more extensively covered by this membrane, which then extends over the whole of the upper region and over a small portion of the anterior. As the peritoneum passes from the sides of the bladder to the iliac fossae, it forms folds, improperly called the lateral ligaments, and in passing from the back of the bladder to the rectum or uterus, a similar fold on each side, called the posterior ligaments of the bladder. Between these the cul-de-sac of the peritoneum descends ; this in the male subject is the lowest portion of the peritoneal cavity, it extends to within about three inches and a half of the anus : in ascites it has been known to be somewhat lower, and has even been tapped in this situation from the rectum.
2dly. The external or first cellular coat con nects the serous to the muscular tissue ; it also covers those regions of the bladder where the serous membrane is deficient. In the lateral regions it is more distinct and thick, and is particularly abundant anteriorly between it and the pubes, where it is also very lax, to allow this organ when distended to move freely as it rises out of the pelvis into the abdomen. It contains some but not much adipose matter ; towards the inferior and lateral parts it con tains many bloodvessels, chiefly venous, and a great number of nerves, which can be distinctly traced from thence in all directions over the bladder. Towards the vesiculw it is dense and white, and supports a number of veins ; this coat is strong, resisting, and elastic ; it binds together, supports, and assists the muscular fibres.
The third coat of the bladder is the muscular : this is composed of fasciculi running in dif ferent directions, and which, though they appear pale and feeble when contrasted with the volun tary muscles, are yet much stronger and redder than those in the corresponding coat in most of the other hollow viscera, being intermediate in these respects to those of the stomach and oesophagus ; this tunic, however, presents great diversity as to colour and density in different individuals. In the contracted state of the bladder, it of course appears more dense than in the distended ; in the latter, but particularly in the over-distended state, it appears thin and imperfect in some places, in consequence of the fasciculi being separated from each other. In the young, ceteris paribus, it is stronger than in the old, and in the female than in the male ; but long-continued irritation at any age and in either sex has the effect of thickening it, as also any disease which causes obstruction to the flow of urine. If the bladder be removed from the body, slightly distended and sub jected to maceration for a few hours, this tunic will admit of more distinct examination ; its fibres will then be seen to take such different directions as to admit of a tolerably easy, though not a perfectly natural separation into distinct laminae, the fibres in the first or super ficial of which have a longitudinal course ; be neath this is a second stratum, whose fibres are transverse or circular; and in some situa tions even a third lamina can be distinctly seen, the fibres of which are by some des cribed under the name of oblique, but the term reticular would appear more correct : in general these three laminae can be made dis tinct, . particularly on the anterior part of the bladder. The first or longitudinal lamina con sists of the longest, strongest, and most nu merous fasciculi ; many of these are connected superiorly to the urachus, thence they descend principally on the fore and back part of the bladder, a few only along the sides ; inferiorly they terminate about the neck. These fibres are very parallel, and much stronger on the an terior and posterior aspects than upon the sides, where they run more obliquely or irregularly, and decussate with one another. The inferior attachment of these fibres in the male subject may be ascertained by careful dissection to be as follows :—those on the fore part of the bladder are connected chiefly to the anterior ligaments, or to. the reflections of the fascia from the pubis on this organ ; these appear as shining and dis tinct as tendons, and have been by some con sidered as such to these muscular bands. Above this insertion these longitudinal fibres appear very numerous, and those on the right and left of the median line distinctly decussate or interlace. Several here also take a transverse or an arched or semicircular course; some of these are very distinct and are inserted laterally ; they must serve to strengthen and to bind down the longitudinal fasciculi. The latter in this situation can be divided into layers, the superficial of which only are inserted, as has been described, into the anterior ligaments of the bladder, and through these into the pubis. The deeper set are inserted, some into the dense cellular tissue about the upper surface of the prostate, and some pass deeper, and intermingle with that circular mus culo-cellular tissue which surrounds the cervix, and which constitutes the true sphincter. Some of those longitudinal fibres, particularly more laterally, pass so deep in this situation as to be very distinctly seen, when the bladder is opened, through the mucous lining of the orifice of the urethra. of the longitu dinal fibres we consider as important, as it must enable them during their contraction to draw out or expand the sphincter, so as to allow of the escape of the urine. Laterally these longi tudinal fibres are attached, a few of them to the margin of the prostate, while others expand over the lateral lobes of this gland, and are in serted into the fascia which covers it. Poste riorly these fibres are very distinct, particularly near the inferior surface of the bladder between the two ureters ; to these last-named tubes seve ral of these fibres are connected : some ascend upon them in arches concave upwards ; these we have traced several inches along the ureters ; while others descend in the same course with them, and are inserted into the trigone of the bladder. The longitudinal fibres collect into a strong flat band between and beneath the two vesiculw, over which however no fibres pass as they do over the prostate, which circum stance clearly separates these vesicles from, while the contrary disposition rather connects the prostate with, the urinary excretion. This
band of fibres can be followed near to the base of the prostate ; some of its fibres are then in serted into the submucous fibrous tissue in this situation, others into the base of the gland itself; and very generally one long delicate but distinct band enters the notch in the base of the gland, passes beneath the uvula and middle lobe of the prostate, into which it is 'sometimes insert ed, but it can frequently be traced nearly an inch further forward to be inserted by a delicate tendon beneath the seminal caruncle or the verumontanum, which is partially covered over by a fold of mucous membrane or by a sort of prepuce. The effect of this band of the longitu dinal fibres must be to depress the uvula, and thus to open the orifice of the urethra, and also to depress and to draw the seminal caruncle (a sort of organized glans) downwards and back wards within the prepuce or sinus pocularis, which covers it, and thus protects it from the irritation of the urine. In the female the lon gitudinal fibres are inserted anteriorly and late rally into the cellular, glandular, and vascular tissue which surrounds the neck of the bladder, and posteriorly into a more dense tissue which connects the urethra to the vagina; some fibres also pass in deep, as in the male, to be attached to the sphincter. This muscular lamina is de scribed by the older authors as a distinct mus cle, the detrusor urine,' arising from and around the urachus by numerous fibres, which thence descend and expand over the whole surface, and again concentrate towards the neck of the bladder to be inserted by one or two tendons into the ossa pubis. This account, however, is by no means perfectly correct ; for on attentively examining this muscular lamina, we frequently find strong transverse fasciculi crossing superficially to the longitudinal fibres, most frequently on the anterior region, but also near the neck. Occasionally some of the longi tudinal fibres alter their direction gradually or abruptly, as may be particularly noticed about the ureters and also on the lateral regions. Great diversity exists as to the arrangement of this tunic in the lower animals : thus in the dog this plane consists of strong and regularly parallel fibres, whereas in the ox they assume a reticular and irregular course : in man they re semble the arrangement of the carnivorous more than that of the graminivorous animals. This tunic must have the effect of compressing the bladder towards the ossa pubis, and of course urging the contents of the cavity in that direc tion, while at the same time some of its fibres will expand the orifice of the urethra by draw ing out the sphincter above and on either side, and below by depressing the uvula and the verumontanum. This stratum of muscular fibres can be raised with a little careful dissec tion ; a few fibres must be divided, which now and then change their direction, and join some of the deeper orders : this separation is difficult and can be but imperfectly made on the lateral regions, but on the anterior and posterior it can be fully accomplished. The second order of muscular fibres is circular or transverse ; they are paler, weaker, and more scattered than the former, particularly towards the superior part of the bladder, where they are often indistinct. As they descend they increase in thickness, par ticularly near the cervix, where they are so close and distinct as to have induced many to consider them as a sphincter to the bladder,--a term, however, to which they do not appear to have been entitled, for there is no distinction between the fibres in this situation and those which have a parallel course at a greater dis tance ; and inasmuch as the latter are obviously designed to contract the organ and to expel its contents, it is most probable that the former must contribute to the same effect, and forcibly expel the last drops which it contains : indeed it is impossible to draw such a line of distinc tion in this lamina as could denote the limit between the expelling and the retaining or sphincter fibres. In addition to this plane of circular fibres, several others may also be ob served taking a parallel direction ; thus we oc casionally find transverse bands superficial to the longitudinal plane, both on the anterior and posterior regions in different situations. We very generally also find them near the superior fun (is, and constantly on the anterior and lateral parts of the neck, where they cover the decus sation of the longitudinal fibres. In the inter val between the ureters, these transverse fibres are very distinct, particularly above, where they usually form a very distinct cord, arched a little upwards : this semilunar band or projection may be better seen when the bladder is opened; it corresponds to the base of the trigone, ex tends from one ureter to the other, and is im mediately in front of the pouch or bas fond of the bladder, which is so well marked in the adult and old. Throughout the rest of the trigone the circular fibres are by no means so distinct or strong as they are behind it, or as they are towards the anterior and lateral parts of the cervix. This circular plane of fibres may next be raised ; it is almost impossible to do this completely, because many of them deviate from that course, and join into the next or third lamina, taking a totally different course; the separation, however, can be accomplished suffi ciently to demonstrate the peculiar arrange ment of the third plane of fibres, not all over the bladder, but only in particular situations, namely, in the greater part of the anterior and posterior regions, but only very imper fectly on the superior fundus, and on the sides, and not at all on the trigone. Wherever this third layer is exposed, the fasciculi appear very large and thick, and present a very remark able appearance and course, not unlike the inner surface of the cavities of the heart. Large fleshy bundles, bearing some resemblance to the carnece columnw, separate, unite again, and again subdivide, the fibres taking various direc tions, and inclosing interstices of the mucous surface of various size and form : several of the fibres also join those of the circular plane. It is owing to this reticularly arranged stratum of muscular fibres that the bladder, when opened, presents its peculiar irregular surface, which in some cases, particularly if the bladder have been hardened in alcohol, resembles a honey comb surface. If the bladder which has been opened be everted, then carefully closed and distended, this reticular coat will become very distinct when the mucous membrane has been removed. Its action during life must obviously be to contract the capacity of the bladder in every direction. When the internal surface of the bladder, even in the healthy state, is in spected, the different orders of muscular fibres become very apparent; and when this coat has become thickened from any of those causes which are well known to produce thickening, some of the fasciculi often project into the bladder : such a condition of the organ is named a co lumnar state of the bladder. In cases of irritable bladder, when calculous symptoms have been present, and the bladder has been sounded in consequence, these fleshy projections meeting the extremity of the sound, have in some in stances deceived the surgeon into the idea of the existence of a calculus, and this is still more likely to occur should there be any gritty mat ter adhering to their surface. Some of those recorded cases of the operation for lithotomy, in which no stone could be detected, although the symptoms of the disease previously existed, may admit of explanation by a knowledge of this fact. In the bladder of some persons the muscular fibres do not perfectly cover the mu cous surface, particularly if the organ be very capacious. In such cases the mucous membrane may be pushed through some of the cells or meshes of the muscular fibres, and thus a hernia of the mucous coat be produced ; that is, a small pouch or purse of this membrane will protrude between the muscular fasciculi, and will be covered only by peritoneum or by cellular tissue. This pouch may continue to increase in size, because it possesses no power of empty ing itself, and the muscular fibres around its orifice can only contract the latter without affecting the sac itself; hence a process of this sort may enlarge indefinitely, and has been known in some cases to have formed a part of the contents of an inguinal hernia. Pouches of this nature, for there may be several in the same individual, sometimes contain calculi, the latter having probably been the cause of the former, inasmuch as the muscular coat having been excited by the irritation of the stone to increased action, has forcibly pressed the latter into one of the cells of the mucous membrane, which has then become enlarged and protruded, so as to contain the calculus impacted in it. The consequence of this occurrence to the indi vidual, however, is often a fortunate remission of suffering, because the stone being now fixed in a cell, ceases to excite pain or irritation : it is by occurrences of this nature that the boasted and sometimes fortunate efficacy of certain lithontriptic medicines as cures for stone is to be explained.