PERINEUM. 
the operator’s success in lithotomy turns upon 
his knowledge of the relations, the size, and 
the density of this organ as well as of the re- 
sistance of its capsule. The prostate is heart- 
shaped ; it has been also not unaptly compared 
‘to a chesnut. Its base, directed backwards 
and upwards, embraces the neck of the bladder, 
and usually presents a notch for the entrance 
of the ejaculatory ducts; its apex, truncated 
and directed forwards and downwards, is in 
contact with Wilson’s muscles and separated 
from the triangular ligament of the urethra by 
an interval of less than half an inch; its under 
surface, grooved longitudinally in the middle 
line, looks somewhat backwards and rests upon 
the rectum with the intervention of a quantity 
of rather dense cellular tissue, in which fat 
never accumulates ; its upper surface, inclining 
slightly forwards and less extensive than the 
lower, is connected to the pubis by the anterior 
true ligaments of the bladder; and its sides, 
which are rounded, are covered by the levatores 
ani muscles. The vesicule seminales are re- 
lated to the base of the prostate gland, and the 
dorsal veins of the penis lie upon its upper 
surface, which is scarcely three-quarters of an 
inch distant from the pubis. The rectum, when 
empty, is in contact with the under surface 
only of the prostate, but when distended, it 
also encroaches upon the sides of the gland; 
this occurs to an extreme degree whenever the 
bowel presents the dilatation so commonly 
observed in elderly persons; in such cases the 
prostate appears embedded in the walls of the 
gut, a disposition fraught with danger to the 
intestine in the ordinary operation for stone. 
The prostate gland varies so much in size at 
different periods of life, and even in different 
individuals of the same age, that it is impossi- 
ble to gps its exact dimensions. The organ 
is small in the child; it increases greatly at 
puberty; in middle.age its measurements are 
still larger, and in the decline of life they 
become not unfrequently excessive. In the 
healthy adult subject: the extreme length of the 
prostate gland from base to apex may be esti- 
mated at from an inch and a quarter to an inch 
and a half; its.depth at the base seldom ex- 
ceeds one inch, whilst from side to side it 
measures somewhat more than an inch and a 
quarter. ‘The urethra traverses the prostate from 
base to apex, and runs much nearer to the upper 
than to the lower surface of that body, so that the 
canal is very unequally surrounded by glandu- 
lar substance. At the base of the prostate the 
glandular substance above the urethra varies 
from two to four lines in depth; below the 
canal it is upwards of six lines deep ; laterally 
its thickness may be estimated at about eight 
lines, whilst in the direction of the ordinary 
“incision in lithotomy, viz. downwards and out- 
wards, from nine to twelve lines is the average 
measurement. Exceptional cases have been 
reported by Velpeau and others, in some of 
which no trace of glandular substance existed 
_ above the urethra, and in others little or none 
beneath it; the latter variety might lead to un- 
pleasant consequences in lithotomy. 
The prostate gland is enveloped by a dense 
933 
capsule continuous with the fibrous membrane 
derived from the posterior layer of the triangu- 
lar ligament of the urethra, and investing the 
membranous portion of that canal. This cap- 
sule is identified above with the anterior and 
lateral true ligaments of the bladder, and its 
strength is such as to impart great firmness to 
the prostate, and a power of resistance altoge- 
gether foreign to the glandular substance. The 
anatomist finds it extremely difficult to lacerate 
the prostate so long as the capsule retains its 
integrity, but a trifling force suffices to tear or 
to split the gland after it has been deprived of 
this covering. The strength of the capsule 
explains the difficulty experienced by lithoto- 
mists in dividing the prostate gland by the 
cutting gorget, and was doubtless in great 
measure the cause of those distressing accidents 
which so frequently resulted from the slipping 
of that instrument, and which have led to its 
disuse in latter years. The common ‘ejacula- 
tory ducts traverse the prostate gland from 
behind forwards and upwards ; they are closely 
approximated to each other, and for practical 
purposes may be considered to occupy the 
middle line. It would be impossible to 
effect with certainty a median section of the 
gland in the living subject without injury to 
one or both of these ducts: this constitutes a 
strong objection to the recto-vesical operation 
of lithotomy, but they are out of danger in the 
lateral and bilateral methods. 
The veins in the neighbourhood of the pros- 
tate gland and of the neck of the bladder are 
remarkable for their plexiform arrangement, 
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 membrane 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 
