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tion may be quite free or firmly bound down to the peritoneum. It has a
peritoneal fold, the meso -appendix, containing its vessels and nerves and attached
to above half the length of the appendix, the distal portion being generally
quite free and entirely surrounded by peritoneum. The vermiform appendix is
usually hollow as far as its extremity ; and its cavity communicates with that of



d.




110



OHGANS OF DIGESTION.



the caecum by a small orifice, sometimes guarded by a valvular fold of mucous
membrane.

According to the results of Ribbert's observations the cavity of the vermiform
appendix exhibits a distinct tendency to undergo obliteration. Thus out of 400
cases examined by him 99 or nearly 25 p.c. had the lumen of the process more or
less obliterated. In 50 p.c. of the obliterated cases its distal fourth only, and in
3.5 p.c. the whole process was closed, while the remainder showed intermediate
stages. This tendency to obliteration increased with age. Lafforgue did not find
such a large proportion of cases showing this tendency, thus out of 200 cases only
7 p.c. belonged to this category. In 3 p.c. the obliteration was total, in 3 p.c. it
was closed for a distance of 1 cm. and in 1 p.c. from 2 to 3 cm.

Rtbbert has also investigated the length of the appendix at different periods of
life. At birth its average length is 84'4 mm., by the 10th year it has increased to
90 mm., during the next 10 years it grows slowly, being at the 2ith year 97.5 mm.
long. After this period it gradually diminishes in length, thus from 20 to 30 to

Fig. 140. SECTION THROUGH THE LOWER END

OF THE ILEUM, THE ILEO-COLIC VALVE, THE
C.ECUM, AND ASCENDING COLON, TO SHOW
THE RELATION OP THE TERMINATION OF
THE ILEUM TO THE CJ7.CUM. THE ANTERO-
EXTERNAL WALL OF CJ3CUM REMOVED IN
FIG. 139 IS REPRESENTED AS IN SITU. (J. S. )

a, untero-external wall of caecum ; b, cavity
of ileum ; c, lower or ilco-cascal segment of
ileo-colic valve ; d, upper or ileo-colic segment ;
d. e, fraenum on right side of ileo-colic opening ;
/, ascending colon ; y, vermiform appendix with
its mesentery ; /(, h, k, peritoneum.

95 mm. ; from 30 to 40, 87 '5 mm. ;
from 40 to 60, 85 mm. ; and the
average in subjects over CO is 82'5 mm.
Ribbert found considerable individual
variations ; in one middle-aged male it
was 210 mm., and in a child 5 years
old 120 mm. He estimates the length
of the appendix as compared with the
whole of the large intestine as 1 to 10
in the new-born, andl to 20 in the adult.

So far as is known, this appendix is peculiar to man and certain of the higher apes, and to
the wombat ; but in some animals, as in the rabbit and hare, the distal part of the crecum,
being diminished in diameter and thickly studded with lymphoid follicles, may represent a
condition of the appendix.

Ileo-colic or ileo-caecal orifice and valve. The lower end of the ileum passes
upwards and to the right, being at first internal to and then behind the caecum, and
terminates by opening into the posterior part of the large intestine at the junction
of the caecum and ascending colon (see figs. 139 and 140).

The orifice is generally situated opposite a point on the anterior abdominal wall
from 1 to 2 inches internal to and a little above the anterior superior iliac space. When
the colon is opened it appears as a transverse or slightly oblique slit about half an
inch in length. This opening is guarded by a valve composed of two segments or
folds which project into the large intestine. This is the ileo-colic or ileo-ccecal valve :
it is also called the valve of Bauhin and the valve of Tulpius, although Fallopius
had described it before either of those anatomists. The upper of the two segments




THE LARGE INTESTINE. Ill

(see fig. 140) is horizontal, and the lower and larger oblique. At each end of the
aperture these folds coalesce, and are then prolonged as a single ridge on each side
for some distance round the cavity of the intestine, forming the frceiia or fetinacula
of the valve. The opposed surfaces of the valvular folds which look towards the
ileum, and are continuous with its mucous surface, are covered like it with villi ;
while their other surfaces, turned towards the large intestine, are smooth and
destitute of villi. In the 5th month of foatal life both surfaces of the ileo-colic valve
possess villi, but by the 9th month the villi on the colic aspect of the valve are
represented by only a few stunted processes (Langer).

Each segment of the valve consists of two layers of mucous membrane, continuous
with each other along the free margin, and including between them, besides the sub-
mucous areolar tissue, a number of muscular fibres, continued from the circular
fibres of the ileum and of the large intestine. The longitudinal muscular fibres and
the peritoneal coat take no part in the formation of the valve, but are stretched
across it uninterruptedly from one intestine to the other ; if these be removed and
gentle traction be made upon the ileum the valve will gradually become less pro-
minent, and may ultimately disappear by being unfolded and drawn out of the colon.
The function of the ileo-colic valve is to prevent the intestinal contents passing from
the large into the small intestine. Its valvular action is independent of muscular
contraction as air or fluid forced into the large intestine in the cadaver does not
generally find its way into the ileum. It is probable that the distension of the
caecum presses the walls of the ileum against one another much in the same way as
the urine is prevented from passing from the bladder into the ureters.

Debierre (Lyon Mi-dlcal, Nov.. 1885) made a series of experiments to determine the
competency of this valve by injecting, per rectum, air or water with the intestines in situ.
and he found that it permitted these to pass from the large to the small intestine in the
proportion of about 2 out of 3. When competent, however, it resisted the pressure of a
column of water from 3 to 4 metres in height, the large intestine finally rupturing without
a drop of fluid having passed through the ileo-colic orifice. He considered that in the cases of
iucompetency the caecal segment of the valve was shorter than the colic, while in the others
it was as long or longer.

Birmingham has recorded a case of absence of the ileo-colic valve, and Struthers has
described several specimens in which the valve was imperfectly developed.

Various peritoneal folds and fossse occur in the region of the csecum, vermiform
appendix, end of ileum and commencement of ascending colon, but anatomists are
by no means agreed as to their frequency or nomenclature. The following state-
ment is based mainly upon the observations of Lockwood and Eolleston.

Ileo-colic fossa, situated in the angle between the ileum and the commencement of
the ascending colon and bounded in front by the ileo-colic fold (superior ileo-ceecal
fold of Treves).

Ileo-ccecal fossa, behind the junction of the ileum and the cascum. It may
extend upwards behind the ascending colon nearly as high as the right kidney and
duodenum. The mouth of this fossa is below, and is bounded in front by the ileo-
caecal fold (bloodless fold of Treves).

Sub-ccBcal fossa, placed directly behind the caecum. Its fundus may pass
upwards behind the ascending colon. It is less frequently met with than the other
fossas.

The vermiform appendix may be concealed within one of these pouches and
firmly attached to its walls, constituting what is termed hernia of the appendix. It
is very probable that the cases described as examples of absence of the appendix were
of this nature with the mouth of the fossa closed.

COLON. The ascending colon is continuous with the cascum at the level of
the ileo-colic opening. It passes upwards through the right lumbar into the hypo-



112



ORGANS OP DIGESTION.



chondriac region until it comes in contact with the inferior surface of the right
lobe of the liver external to the gall-bladder. Here ib bends forwards and to the
left as the hepatic flexure. The ascending colon is smaller than the caecum, but
larger than the transverse colon. It is overlaid in front by some convolutions of
the ileum, and is bound down firmly by the peritoneum which passes over its anterior



D.C





Fig. 141. TRANSVERSE SECTION THROUGH THE ABDOMEN OF A FCETUS 3 INCHES LONG. (J. S. )
D. C. , descending colon ; P, peritoneum : K, left kidney : V, body of vertebra.

Fig. 142. TRANSVERSE SECTION THROUGH ABDOMEN OF A NINE MONTHS FCETUS. (J. S.)

B.C., descending colon; Ps, psoas muscle; Q.L., quadratus lumborum ; E.S., erector spinee ;
L.V., lumbar vertebra.

surface and its sides, and generally leaves an interval in which its posterior surface
is connected by areolar tissue with the fascia covering the qnadratus luraborum
muscle, and with the front of the right kidney. In some cases, however, the peri-
toneum passes nearly round it and thus forms a distinct though very short rneso-
colon.

The transverse colon extends from the hepatic flexure in the right hypochon-

Fig, 143. TRANSVERSE SECTION

THROUGH THE ABDOMEN OF A
MALE ADULT. (J. S.)

References as in Fig. 142.

drium to the splenic flexure in
the left hypochondrium ; be-
tween these two points it
forms a loop usually directed
downwards and forwards. As
the transverse colon is con-
siderably longer than the
transverse diameter of the
abdomen, and possesses a long
meso-colon, its position is
liable to considerable varia-
tions. It generally crosses the abdomen above the level of the umbilicus, but may
reach considerably lower.

Above, the transverse colon is in contact with the under surface of the liver, the
gall-bladder, the great curvature of the stomach and the lower end of the spleen. It
is covered in front by the great omentum. On the right side it crosses in front of
the second part of the duodenum to which it may be united by areolar tissue or
attached by a short peritoneal fold. In the rest of ifs course it has behind it some




THE LARGE INTESTINE. 113

of the convolutions of the jejunum and ileum to the left of the second part of the
duodenum. The two layers of the transverse meso-colon are attached to its upper
border, and aft-r investing the colon they become continuous with- the great
omentum. Tho part of the transverse meso-colon which is often found in front of
the duodenum is formed entirely by the great sac, while that to the left of the
duodenum is derived from both great and small sacs.

The descending colon is continuous with the left extremity of the transverse
colon by a sudden bend named the splenic flexure, which is higher up and farther
back in the left hypochondrium than the hepatic flexure in the right hypochondrium.
At this bending there is found a fold of peritoneum, the costo-colic or phreno-colic
ligament, which stretches with a lunated free border to the colon from the diaphragm
opposite the tenth or eleventh rib. As was pointed out by Haller, it supports the
spleen although unconnected with that organ, and may be termed " sustentaculum
lienis." From the splenic flexure the colon descends in contact with the outer
border of the left kidney. At the lower end of the kidney it usually turns inwards
a little and then descends near the outer border ^f the psoas muscle to the iliac fossa
where it joins the sigmoid colon. In a young foetus (see fig. 141) the descending
colon has a relatively long meso-colon which is attached to the abdominal wall
internal to the kidney, and passes outwards in front of that organ to join the colon.
This meso-colon is obliterated before birth (see fig. 142), probably by a blending of
its posterior layer with the peritoneum in front of the kidney. After foetal life the
descending colon is generally covered by peritoneum on its anterior arid outer sur-
faces, the posterior and inner surfaces being uncovered.

Occasionally, especially when the colon is empty, the peritoneum lies behind the
outer part of the posterior surface (see fig. 143), but the existence of a distinct
descending meso-colon is rare.

The sigmoid colon may be defined as that part of the colon which is attached
to the left iliac fossa from the iliac crest to the brim of the true pelvis. In front of
the crest of the ilium it is continuous with the descending colon ; from this point it
usually passes downwards, forwards, and somewhat inwards for two or three inches,
approaching the anterior abdominal wall internal to the anterior superior iliac spino.
This part generally lies in close relation with the fascia in front of the iliacus and is
covered by peritoneum on its anterior and lateral aspects only. The rest of the
sigmoid colon is generally very movable, being provided with a long meso-colon
which is attached transversely in front of the psoas, and becomes continuous
internally near the bifurcation of the common iliac artery with the meso-rectum.
This portion may be termed the sigmoid loop or the sigmoid flexure proper. It is
very variable in its length and position, and frequently forms with the first part of
the rectum an omega loop (Treves). In many cases it forms a loop hanging down
into the true pelvis ; if the bladder or rectum is distended it is pushed out of the pelvis
and may curve upwards as high as the umbilicus, and even in rare cases touch the
liver (Treves). Occasionally this loop lies in the iliac fossa in front, and to the outer
side of the first part of the sigmoid colon. When its meso-colon is short it simply
passes downwards and inwards across the iliac fossa, usually entirely covered in front
by the convolutions of the small intestine. The average length of its meso-colon is
about 3 inches. On turning upwards the sigmoid loop and its meso-colon the
mouth of a peritoneal pouch is sometimes seen, which is called the inter-sigmoid
fossa. It is somewhat funnel-shaped and extends upwards a variable distance in the
direction of the ureter.

THE RECTUM. The lowest part of the large intestine (intestinum rectum} extends
from the sigmoid loop of the colon to the anal canal. It is situated entirely
within the true pelvis to the posterior wall of which it is attached. It is continuous
at the pelvic brim near the left sacro-iliac articulation with the sigmoid flexure, and

VOL. III., PT. 4. i




Fig. 144. MEDIAN SECTION OF THE PELVIS AND ITS VISCERA IN AN ADULT MALE. (J. S.) g.

The bladder contained about 3 oz. of urine and there were some faeces in the lower part of the
rectum. 5th L.V., body of 5th lumbar vertebra; S, on body of 2nd sacral vertebra; P.S., pubic
symphysis ; R.R., rectum; P.R., plica dextra recti ; A.C., anal canal with its longitudinal folds of
mucous membrane the columns of Morgagni. The tissues between the anal canal and the coccyx
constitute the ano-coccygeal body. I.S., internal sphincter; E.S., external sphincter; LA., levator
ani ; R.C., resto-coccygeus muscle ; Bl., bladder ; P, P 1 , P 2 , prostate gland, P, its middle lobe,
between P and P 1 , the common ejaculatory duct ; M., membranous part of urethra ; S. , spongy part of
urethra; C.C., corpus cavernosum ; G. , glans penis; B., bulb of corpus spongiosum ; B.C., bulbo-
cavernosus muscle ; F., supra-pubic pad of fat ; F-, retro-pubic pad ; p, peritoneum.



THE LARGE INTESTINE. 115

passing downwards, backwards, and to the right, usually reaches the middle line
opposite the third piece of the sacrum. This is generally called the firsfc- part of the
rectum. At the third sacral vertebra it changes its direction, and curving forwards
and downwards as far as the lower end of the prostate gland forms the second part
of the rectum which is continuous below with the anal canal.

The first part of the rectum, about 5 or 4 inches long, is covered by peritoneum,
and attached by a fold of this membrane called the meso-rectum to the front of the
sacrum. Some convolutions of the small intestine, or a loop of the sigmoid colon,
usually lie against its anterior aspect. In the male a distended bladder will push the
intestines upwards and come in contact with it, while occasionally in the female the
uterus touches it. On its left side are the ureter and the branches of the internal
iliac artery.

The second part of the rectum, 3 or 4 inches in length, is only partially covered
by peritoneum. It has no meso-rectum, and its posterior surface is entirely uncovered
by the peritoneum. At its commencement it is covered in front and at the sides,
but the peritoneum gradually leaves the lateral surfaces, and is finally reflected from
the anterior aspect on to the bladder about an inch above the prostate gland. In
passing from the rectum to the bladder the peritoneum forms a cul-de-sac, the recto-
vesical pouch, which is bounded above on each side by a lunated fold of the serous
membrane of which the left is almost always the larger (posterior false ligaments of
the bladder}. Distension of the bladder and rectum tends to draw up the peritoneum
and thus diminish the depth of the recto- vesical pouch. The posterior wall of this
part of the rectum lies from above downwards on the lower part of the sacrum, the
coccyx and the ano-coccygeal body. The anterior wall, which is longer and more
curved than the posterior, is in contact with the recto-vesical pouch of peritoneum, a
triangular area at the base of the bladder with its lateral boundaries, the vasa
deferentia and the vesiculae seminales, and the prostate gland. Opposite the prostate
gland it turns downwards and backwards to end in the anal canal, not unfrequently
forming below the prostate a short blind recess (see fig. 144). In the female the
second part of the rectum is in relation with the pouch of Douglas and the posterior
vaginal wall. Sometimes the sigmoid flexure is displaced towards the right iliac
fossa, and the first part of the rectum descends in the pelvis in front of the right
half of the sacrum.

VARIATIONS ACCORDING TO AGE. The rectum is straighter, more vertical, and
relatively larger in the infant than in the adult.

Structure of the rectum. The rectum differs in some respects from the rest
of the large intestine in the arrangement of both its muscular and mucous coats.

The muscular coat is thick ; the external or longitudinal fibres are found
all round the bowel, but are collected chiefly into two bundles, one on the anterior
and the other on the posterior aspect. The longitudinal fibres being rather shorter
than the other coats give rise to sacculations, which are chiefly situated at the sides
of the rectum. The circular fibres are well developed and form thick bundles at the
constrictions between the sacculations (Otis). A pair of small bands of plain
muscular tissue, which arise from the front of the second and third coccygeal
vertebra;, and are also connected with the pelvic fascia, pass with a slight downward
inclination to the posterior part of the anal canal (see fig. 144), and become inter-
mingled with its longitudinal fibres. They are known as the recto-coccygeal muscles.

The mucous membrane of the rectum is thicker, redder, and more vascular
than that of the colon ; and it moves more freely upon the muscular coat. When
the rectum is empty and contracted it exhibits numerous folds, most of which are
obliterated by distension. Several transverse or oblique folds are, however, of a
more permanent character, and have been designated "valves of the rectum"
(Houston) or " plicae recti." One of these, usually the largest, is situated on

i 2



116



ORGANS OF DIGESTION.



the right side opposite the reflection of the peritoneum from the rectum to the
bladder, and was named by Kohlransch the " plica transversalis recti." There
are generally two other folds, both on the left side, one about an inch above, and the
other about the same distance below, the fold on the right side. From the position
and projection of these folds they may more or less impede the introduction of
instruments. The dilatation of the rectum between the anal canal and the lowest
of these folds is called the rectal ampulla. (For the appearance of these folds on
rectal inspection with the body in the genu-pectoral position, see Otis, " The
Sacculi of the Rectum," Leipzig, 1887.)

The anal canal and its muscles. The terminal portion of the alimentary
canal, which is surrounded by the sphincters of the anus, may be termed the anal
canal. It is an antero-posterior slit in the pelvic floor ; its lateral walls being in
opposition, it differs in this respect from the lower part of the rectum, which when
empty appears as a transverse slit (fig. 145). The anal canal is directed downwards

Fig. 145. A TRANSVERSE AND NEARLY
VERTICAL SECTION OF ADULT MALE
PELVIS ; THE SECTION PASSED FROM
ABOVE DOWNWARDS AND SLIGHTLY

BACKWARDS. Life size. (J. S.)

B. , cavity of bladder ; V. D. , vas
deferens ; S. V., seminal vesicle; R,
second part of rectum ; A.C., aual canal ;
L.A., levatorani; I.S., internal sphincter
of anus ; E.S., external sphincter of
anus.

and backwards, and measures
fully an inch in length when the
rectum is empty, but is shorter
when the rectum is distended.
Its antero-posterior extent is
from half to three-quarters of an
inch (see fig. 144). It is bounded
behind by the ano-coccygeal body,
and at the sides by the fat of the
ischio-rectal fossse. Its anterior
relations differ in the two sexes ;
in the male the bulb of the
corpus spongiosum lies a little
in front of it, while in the

femal it is separated from the vulval opening, and the lower end of the vagina
by the permeal body.

In the skin around the anus and about a centimeter from its margin is a circular
zone of large sweat glands which are known as the circumanal glands. At the anus
the epidermis is continued for a short distance into the aperture, but becomes
gradually thinner and finally is replaced by the columnar cells of the mucous
membrane. The crypts of Lieberkiihn do not appear immediately ; there is a
narrow zone of mucous membrane destitute of glands.

The mucous membrane of the anal canal is thrown into 4 or 5 longitudinal
folds on each side which were named by Morgagni the columns of the rectum.
These folds contain longitudinal muscular fibres (apparently part of the inuscu-
laris mucosee) which terminate both superiorly and infer iorly in elastic tissue
'Treitz).

The muscles which close the anal canal are the internal and external sphincters







LITERATURE OF THE INTESTINES. 137

and the levatores ani. The external sphincter and the levator ani will be found
described in Vol. II. pt. 2.

The internal sphincter is a pale muscle, composed of non-striped~fib~res, which
surrounds the entire length of the anal canal. It is of nearly uniform thickness,
about 4 mm., in its entire extent, and ends almost abruptly above, where it
becomes continuous with the much thinner circular fibres of the rectum.

Vessels and Nerves of the Rectum and Anal Canal. The arteries of the
rectum spring from three sources, viz., the superior hcemorrhoidal from the inferior
mesenteric, the middle hcemorr/wicfal from the internal iliac, and the inferior hcemor-
rhoidal from the pudic artery. Of these the most important is the superior hsernor-
rhoidal. It is a single vessel which descends in the meso-rectum, and then divides
into two branches which form loops, one on each side of the rectum, with the con-
vexity of the loop directed downwards. From these loops several branches arise which
pass downwards, pierce the muscular coat, and run in a longitudinal direction under
the mucous membrane, and anastomose freely with one another. In the anal canal
they lie in the longitudinal folds of the mucous membrane and reach as far as the
verge of the anus. The arrangement of the veins is somewhat similar ; they com-
mence in little dilatations at the lower end of the anus, ascend beneath the mucous
membrane for about three inches, where they communicate with one another to form
the hsemorrhoidal plexus, and then pierce the muscular coat by 5 or 6 openings,
and pass upwards to the superior haemorrhoidal vein, which forms the beginning of
the inferior mesenteric trunk. According to Quenu, the hsemorrhoidal plexus
communicates freely with the tributaries of the inferior htemorrhoidal, but only
slightly with those of the middle haemorrhoidal.

The lymphatics enter some glands placed in the hollow of the sacrum (see
Vol. II., Pt. 2, p. 551).

The nerves are very numerous, and are derived from both the cerebro-spinal and
the sympathetic systems. The former consist of branches derived from the sacral
nerves, and the latter of offsets from the inferior mesenteric and hypogastric plexuses.
Experiments upon animals have shown that the longitudinal muscular fibres of the



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