Bladder, vesicale seminales, and vasa defe rentia.—It is here necessary to notice briefly so much of the under surface of the bladder as is uncovered by peritoneum, and to consider in a cursory manner the vesiculm seminales and vasa deferentia. These structures are situated very deeply in the perineum, and therefore they are dissected with advantage from within the pelvis.
On looking down into the pelvic cavity in a recent subject after the peritoneum has been displaced and the bladder drawn gently to either side, the anatomist obtains a satisfactory view of the course and connections of the recto-vesical layer of the pelvic fascia, which there constitutes the superior boundary of the perineum. The recto-vesical is the innermost layer of the pelvic fascia ; after investing the inner surface of the levator ani muscle it is reflected upon the prostate gland and side of the bladder, and more posteriorly upon the rectum ; a line drawn from the lower extremity of the symphysis pubis to the spinous process of the ischium is nearly the level at which this reflection takes place. This fascia is closely connected in front to the upper surface of the prostate gland, and in that situation it forms the anterior true ligaments of the bladder; it next adheres to the edges of the gland, and more posteriorly to the sides of the bladder, there constituting the lateral true ligaments of that viscus; whilst still further back it is iden tified with the sides of the rectum as has been already described. Its attachments to the blad der at either side respectively are situated a little above the vesiculx seminales.
This fascia forms the line of demarcation between the perineum and the upper portion of the pelvic and the abdominal cavity. It is of sufficient strength to resist powerfully the des cent of any of the abdominal viscera through the space between the bladder and the parietes of the pelvis, and affords equal resistance to the progress upwards of matter or other effu sions from below ; it may be considered as a sort of shelving roof to the perineum, and a concave floor to the abdomen. Its density and strength are at their maximum in front, whilst both these properties diminish as it approaches the rectum. Above it, is found a quantity of loose adipose cellular inembrane, continuous without line of demarcation with the subserous tissue of the abdomen, whilst below it are situated the cellular tissue of the perineum and the several parts comprised in the depths of that region. His knowledge of its connections
teaches the anatomist that urine effused above the level of this fascia must soon reach the peritoneum and produce the most disastrous consequences; whilst the experienced surgeon endeavours in every operation upon the peri neum to limit his incisions, so as to spare the fascia now under consideration.
That portion of the inferior surface of the bladder which projects into the perineum is bounded posteriorly by the peritoneal cul-de sac, and extends forwards as far as the prostate gland, whilst the line along which the recto vesical fascia takes attachment to the bladder forms its lateml limits. The dimensions of this part of the bladder are exceedingly vari able, being modified by the degree of vacuity or repletion of the organ itself at the time of examination, as well as by the age of the individual ; but its measurements are always much greater transversely than from before backwards. In the adult it is in general of moderate extent, but it increases considerably when the urinary reservoir is fully distended, and it diminishes as that viscus becomes empty, whilst the variable depth of the cul-de-sac of the peritoneum (already dwelt upon in a former part of this article) is calculated still further to render its size uncertain. In the child this region of the bladder scarcely exists, an ano maly explained by the pyriform shape of the organ in early life, the narrow neck of the bladder being then its most dependent portion, and the peritoneum being prolonged very far downwards towards the anus. In old age the perineal portion of the bladder often exhibits extraordinary developement, becoming by far the lowest part of the whole organ, and form ing a pouch which projects remarkably towards the rectum. In many instances calculi become lodged within this depressed part of the viscus, far beneath the level of the cervix vesim so as to elude detection by the sound ; and in this manner is explained the valuable assistance which the finger introduced into the rectum so frequently affords the surgeon in exploring the bladder for a stone. The perineal portion of the bladder rests in great measure upon the rectum ; in the middle line it is in immediate contact with the gut, but towards either side a part of the vesicula seminalis and vas deferens is interposed.