We may conveniently designate further an upper concave surface, or vault, of the bladder, and a floor, or base, as well as right and left lateral walls. These terms basal and apical, right and left lateral, may he reserved for affections located at the more central parts of these areas, near imaginary poles whose axes cross the bladder from side to side, and from top to bottom, at right angles to the first axis described.
Natural Landmarks. —In the anterior vesical hemisphere there are several striking natural points of reference. First of all is the internal orifice Of the urethra itself, with its circumurethral area, extending for an arbitrary distance, say from 1 to 2 cm. on all sides. That portion of the bladder lying immediately above the urethra may be designated as the symphyseal area.
Below the urethra and toward the base of the bladder, on either side, lie the ureteral orces, furnishing the most characteristic land marks, often called into requisition in description, since they are fre quently the seat of disease.
In the knee-breast position the ureteral orifices stand out most prominently, each one forming a little elevation which I propose to call the right and the left mons ureteris. The lower two or three cen timetres of each ureter forms a prominent ridge, in some cases pro jecting into the bladder; I would call this ridge the ureteral fold.
Between the ureters, the interureteric fold often forms a conspic uous landmark, whether traceable by its elevation or by the injection of its vessels. It represents the position of the inter-ureteric liga ment beneath; it may also be a purely imaginary line drawn from one ureteral orifice to the other.
Three lines, one connecting the ureters and one uniting each ure ter to the internal urethral orifice, together form the urethro-ureteral triangle, or better the vesical triangle, or simply the triangle (tri gonum), situated at the anterior part of the base of the bladder, a most convenient area for reference in the description of diseases com ing within its limit, or immediately adjacent to it.
"Posterior to the interureteric fold or line" is an expression fre quently found convenient in the description of affections of the base of the bladder.
Relations to Surrounding Structures.—Important points of reference also for the urologist are those relating to the fixed and movable portions of the bladder. As the bladder becomes emptied, the upper, more movable portion, covered with peritoneum and in relation with the supra-vaginal cervix posteriorly, settles down into the lower less movable portion, until it comes to lie within it as one saucer rests in another.
During respiration the free upper half of the bladder may often be seen moving on the lower half, as if hinged, and the line of de marcation between them may be distinctly made out.
This difference between mobility and relative immobility seems to determine to some extent the localization of the inflammatory affections.
Certain other diseases, such as uterine fistulae and carcinoma, affect by preference the narrow strip of surface in the posterior hemi sphere in close relation to the cervix uteri, above the line of flexion just mentioned.
Below this and running out into pockets in front of the broad liga ment on either side, and clearly developed as the bladder contracts, are the right and left vesical cornua (coma vesicce dextrum and cornu vesicce sinistrum).
As these cornua become evident by the contractions of the blad der, the posterior fold (plica posterior) is seen to form low down, extending across the bladder from side to side, while at the same time two other folds, one on either side, are observed running around the lateral walls in the direction of the urethra.
These three folds mark the boundary line between the freer por tion of the bladder and the attached inferior portion and may in the future be conveniently spoken of as the plicce vesicales, posterior, sin istra, et dextra.