PERINEUM. 
losing altogether its cylindrical shape. It will 
be readily understood that when such a dispo- 
sition prevails in a calculous subject, the rectum 
must undergo serious danger during lithotomy 
performed according to the lateral or bilateral 
methods, and that therefore the precaution of 
emptying the bowel previous to these opera- 
tions is highly advisable. 
The relations of the perineal portion of the 
rectum deserve from the surgical anatomist his 
most attentive consideration. Anteriorly the 
inferior fundus of the bladder, together with 
the vesicule seminales and vasa deferentia, 
come into contact with the rectum immediately 
beneath the line of reflection of the peritoneum ; 
lower down the prostate gland rests upon the 
front of the rectum, to which it is very inti- 
mately connected, nothing but some cellular 
tissue intervening between them, whilst still 
lower down the membranous portion of the 
urethra and the bulb are related to the rectum, 
though not immediately, for neither of those 
parts of the urinary apparatus is found to touch 
the parietes of the gut. The bulb of the urethra 
in the adult is usually situated about half an 
inch in front of the rectum and about one 
inch above the anus; the membranous portion 
of the urethra lies about ten lines anterior to 
the rectum, and rather more than an inch and 
a half above the anus, whilst the prostate gland 
is placed within one line of the anterior wall of 
the gut, and about two inches above the anus. 
These anterior relations of the rectum explain 
how the finger introduced into its cavity may 
assist the catheter in its passage along the 
urethra in the living subject; how by the same 
manceuvre the surgeon obtains valuable infor- 
mation as to the state of the bladder and pros- 
tate gland in various morbid conditions of those 
organs; how, in sounding, he is able at times 
to raise up the calculus by his finger so as to 
bring it into contact with the instrument; how 
the bladder may be punctured from the rectum 
and the urine withdrawn by this route in certain 
cases of retention; how, acute inflammations 
and other diseases of the bladder and urethra 
or their appendages so frequently occasion mor- 
bid sympathies in the intestine, such as pro- 
lapsus, tenesmus, hemorrhoids, &c. ; and above 
all, how great must be the danger to the bowel, 
and how urgent the necessity for protecting it 
during the lateral operation of lithotomy. 
Posteriorly a quantity of loose cellular tissue 
connects the lower part of the rectum to the 
sacrum and coccyx; it is there related, parti- 
_ cularly when distended, to the pyriformis and 
_ ischio-coccygeus muscles, and towards its anal 
- extremity to some of the fibres of the levatores 
ani and the ano-coccygeal ligament. 
On either side the rectum gives insertion to 
a portion of the recto-vesical layer of the pelvic 
fascia, which, though weak and cellular in that 
locality, nevertheless admits of being fairly 
traced to the walls of the gut; but the levatores 
ani muscles constitute the principal lateral rela- 
tions of the intestine. In their descent they 
_ cover its surface extensively, and form in great 
measure the partition between the bowel and 
the ischio-rectal fossa. 
921 
The perineal portion of the rectum affords in 
some respects a striking contrast to the upper 
part of the same intestine; being totally devoid 
of serous investment, it is more fixed and 
(except at the anus) more dilatable than the 
superior division of the bowel, and its con- 
nexions with the recto-vesical layer of the pelvic 
fascia, the ano-coccygeal ligament, the genito- 
urinary passages, and the middle tendinous 
point of the perineum, contribute to fix it still 
more firmly in its position. 
The coats of the rectum present certain pecu- 
liarities interesting to the surgical anatomist. 
Its muscular tunic is of uncommon strength, 
and consists of two very distinct layers ana- 
logous in many particulars to those of the 
corresponding strata in the cesophagus; the 
superficial layer is formed of highly developed 
longitudinal fibres, florid in colour (as con- 
trasted with those of the remainder of the large 
intestine), and which spread out so as to invest 
the whole circumference of the gut: the fibres 
of the deeper layer are circular, and acquire 
increased developement towards the anal extre- 
mity of the intestine, where they are continuous 
with the internal sphincter. The mucous mem- 
brane is remarkable for its thickness and vascu- 
larity and for the great laxity of its connexion 
with the other tissues of the gut: it adheres so 
loosely to the subjacent coat in the vicinity of 
the anus that it sometimes protrudes through 
that opening, and in this manner one form of 
prolapsus ani is produced. 
Upon the free surface of the mucous mem- 
brane a number of longitudinal folds run down 
to the immediate neighbourhood of the anus ; 
they are called the columns of the rectum, and 
converge slightly as they descend ; their number 
is variable though it seldom exceeds eight or 
ten, and between them inferiorly some trans- 
verse semilunar folds may be observed, of which 
the free concave margins are directed upwards. 
In these folds of the mucous membrane the 
physiologist recognises a provision to facilitate 
the distension of the gut, and to their presence 
some surgeons attribute the occurrence of cer- 
tain morbid conditions of the intestine. In 
addition to these folds, which are constant, 
others have likewise been described within the 
rectum; these latter were named by the late 
Dr. Houston “ the valves of the rectum,” and 
appear at times remarkably distinct. When 
present they are each of a semilunar shape, 
and formed by a duplicature of mucous mem- 
brane containing cellular tissue and a few 
muscular fibres between its folds. Each valve 
is attached by its convex margin to the walls of 
the gut, whilst its free edge is directed more or 
less inwards towards the cavity of the intestine. 
One of these valves is situated (according to 
Houston’s statement) opposite to the base of 
the bladder, on the anterior wall of the gut and 
about three inches distant from the anus, whilst 
another is sometimes placed within one inch of 
the anal orifice. 
That projections from the parietes of the 
rectum, such as have been described by Houston, 
may be made apparent by a certain mode of 
preparation cannot be denied, but that they can 
