The veins in the neighbourhood of the pros tate gland and of the neck of the bladder are remarkable for their plexiform armngement, and are called the vesico-prostatic plexus. This plexus, receiving anteriorly the dorsal veins of the penis after their entrance into the pelvis, and communicating posteriorly with the he morrhoidal veins, delivers its blood into the internal iliacs; it lies chiefly upon the upper and lateral surfaces of the prostate, and on the lateral and inferior aspects of the neck and neighbouring portion of the base of the blad der. The veins which constitute this plexus are covered by a layer of the capsule of the prostate, and bound down to the bladder by a strong membmne derived from the recto-vesical lamina of the pelvic fascia. They communi cate in the freest manner with each other, and are but moderately developed in young and healthy subjects, whilst in elderly persons and in cases of chronic disease of the bladder, as well as in calculous affections, they occasionally attain to an immense size and assume a vari cose disposition. The hemorrhage from ves sels so enlarged might be followed by a fatal result in lithotomy. The mouths of these veins remain permanently patent after they are di vided; this results from the fibrous investment which binds them down, and has been supposed by the French surgeons to predispose them to phlebitis after operations, by exposing their delicate lining membrane to the irritating influ ence of the urinary stream.
An irregular artery is sometimes found along the side of the prostate gland, and has been the source of fatal hemorrhage when divided by the lithotomist. This vessel is destined to replace one or more of the terminating branches of the internal pudic, and when present, always continues on to form the dorsal artery of the penis; it occasionally gives off the artery of the bulb and the artery of the crus penis, or this latter branch alone, during its progress. When the irregularity now described occurs, the pudic artery of the same side suffers a corresponding diminution in size, and stops short in the perineum after furnishing a variable number of branches. The irregular trunk here alluded to springs in general from the internal iliac, or from one of the branches of that artery ; but from whatever source derived, it runs akin.. the side of the prostate gland to the neighbourhood of the pubis, where it mounts above the urethra and passes beneath the sym physis, in company with the dorsal veins of the penis. This irregular vessel runs nearly in the line of the incision in lithotomy, whether per formed according to the lateral or the bilateral methods, and pursuing such an unfortunate course it can rarely escape the knife during these operations. Examples of this irregularity have been recorded by Blandin, Velpeau, Shaw, and others.
The preceding description of the deep com partment of the perineum would be imperfect without some application of the anatomy uf that space to practical purposes, particularly as the third incision in the lateral operation of litho tomy is performed within its limits. In this step of the operation the surgeon, in order to make way for the calculus, cuts through the remainder of the membranous portion of the urethra, together with the left lobe of the prostate gland, and in doing so he must also divide Wilson's muscle and some fibres of the levator ani. From the many important parts which surround the prostate, this incision is beset with difficulties. The rectum is much endangered ; this arises front its proximity to the under surface of the prostate gland, and from its occasional dilatation. To insure the safety of the gut it should be emptied by the administration of an enema previous to the operation ; the handle of the staff should also be depressed before the third incision com mences, and the edge of the knife should be duly lateralised ; without the latter precaution all other expedients to save the intestine are useless. The depression of the handle of the staff raises the beak of the instrument behind the pubis, and causes the knife to enter the bladder as much as possible in the axis of that viscus, a line of incision best calculated to protect the bowel ; and by perfornaing this manceuvre at the proper moment the operator raises the prostatic portion of the urethra from the rectum, thus contributing still further to the security of the gut.
Hemorrhage is the most formidable conse quence of the third incision in lithotomy. The pudic artery incurs a certain amount of risk when the operator, in his anxiety to save the rectum, directs the edge of the knife too much outwards, but from a former pait of this article the reader may perceive that such an accident is of rare occurrence. The irregular artery which runs along the prostate is much more to be dreaded, for the surgeon can neither foresee nor avoid the danger, and from its position all attempts to tie the vessel when wounded must ne cessarily prove fruitless, whilst the absence of a resisting surface beneath the bleeding orifice pre vents the plug from commanding the hemorrhage.
A profuse loss of blood from the vesico prostatic plexus of veins may be also encoun tered, and is most likely to happen in elderly persons. The largest of these vessels are situ ated at the neck and along the base of the bladder, so that the surgeon guards against such a casualty most effectually by confining his incisions as much as possible within the limits of the prostate gland.