The uvula or apex of the trigone varies very much in its appearance in different persons. In the normal state it is very small, and is most distinctly seen by making only a small opening in the upper region of the bladder when in situ, and looking down towards the cervix ; it then appears as a small projection in the middle line of the orifice of the urethra, which opening it thus assists to close or to fill. It is much effaced by opening the bladder from the urethra after its removal from the subject, the mucous membrane being then easily ex tended. This projection is only a slight full ness or prominence of the mucous membrane with an increase in the submucous tissue, in which small follicles or cryptw may be dis cerned. This part appears rather vascular, and probably possesses some peculiar organization ; the situation also which it holds, as well as its structure, appear to indicate it to be the seat of a proper sensibility, which, when affected, ex cites the irritability of the whole organ. Many facts which manifest themselves in the treat ment of urinary diseases seem to corroborate this idea: thus, when a calculus is pressed against this part of the mucous membrane, the pain is insupportable, whereas when it falls or is directed into the inferior fundus, the pain is comparatively trifling; also when a bougie or catheter is being passed into the bladder, a peculiarly acute sensation is experienced as the instrument comes in contact with this par ticular prominence. The uvula in the child is the most depending part of the bladder, at least in the erect posture; this is not the case in the adult; hence probably we have in part the reason why calculus is more painful in the former than in the latter.
The trigone in the female bladder comprises a smaller area, but is broader in proportion than in the male; it is not so distinct or firm in the former as in the latter, where it is sup ported not only by a dense substratum, but also by the vasa deferentia, vesiculm seminales, and prostate gland. This portion of the bladder is so firm and incompressible that it is probable the cavity corresponding to it can never be wholly obliterated, so that in the most contracted bladder a few drops of fluid are still retained: The uvula, like other similar portions. of the mucous membrane, is subject to infiltration and increase of size in acute in flammatory affections, as also to chronic and permanent enlargement; and as it lies nearly over, but a little anterior to the middle lobe of the prostate gland, it is therefore difficult, and in most cases impossible to distinguish affections of the latter from those of the former. The uvula is smaller in the female than in the male; hence the opening from the bladder into the urethra is larger in the former than in the latter.
Organization of the bladder.—a. Arteries.— In the normal state the bladder is not very vascular ; we have already mentioned that its inner surface is pale and free from any red vessels. The arteries, however, of the bladder
are very conspicuous when they have been in jected; they are long and tortuous, and are distributed chiefly along the sides, inferior region, and cervix. They are derived from various sources. The internal iliac or hypo gastric on each side, just before its ligamen tous termination, sends off one or two vesical branches, which ramify on the superior and lateral regions ; the middle hwmorrhoidal and internal pubic also very generally send some considerable branches to its inferior region and cervix; the obturator and epigastric vessels also very frequently send small arteries to it anteriorly. When the bladder is distended, all these vessels are seen very distinctly, and in the muscular coat much more than in the sub mucous tissue, contrary to what may be ob served in the other hollow viscera; this, how ever, is accounted for by recollecting that the mucous coat of the bladder does not in its normal and healthy condition possess, nor does it indeed 'require any high degree of organi zation, as it is simply a reservoir, and has no important function to execute further than to secrete a fine mucous fluid which lubricates its surface and defends it from the irritation of the urine. This secretion mingles with the urine, the properties of which it alters in a remark able manner whenever it is increased in quan tity, as occasionally occurs in chronic disease of this organ. The muscular coat of the blad der is the essential agent in expelling its con tents, and is therefore more fully supplied with vessels than any other of its tunics.
b. Veins.—Tlie veins of the bladder are large and numerous inferiorly, and in old per sons in particular. There are but few on the superior and lateral regions except towards the inferior part of the latter. In the child the veins are very inconsiderable : this difference depends on this circumstance, that the veins which are seen at the inferior region of the bladder, and which return the blood from its tunics, do not belong exclusively to this organ, but are principally derived from the dorsal veins of the penis; they also receive several branches from the vesiculce and the prostate, also from the rectum and intervening adipose substance. In the adult and old these latter veins are very numerous, indeed they may be said to form a perfect ' venous plexus' on each side, extending from the termination of the ureter to the prostate gland. All these veins are considerably less developed in children, inasmuch as the organs, at least those of gene ration, from which they are principally de rived, are comparatively small. The vesical veins ultimately discharge their blood into the internal iliac or hypogastric veins.