[Reprinted from the American Gynaecological and Obstetrical Journal 
for February, 1895.] 
THE/PERITONEUM. 
By Byron Ro.&tnson, M. D., Chicago. 
From the epoch-making-periods of Wolff, Meckel, Fleischmann, 
Oken, Haller (1708-1777, German anatomist, physiologist and phi- 
losopher) and others, we will glance at a period when certain opinions 
were becoming general property and settled. The work done on the 
anatomy and development of the peritonaeum and digestive tract had 
brought to light many natural facts. The time was right for the in- 
vestigation which told the story of the development of the final com- 
plicated structure known as the peritonaeum. This subject had en- 
grossed the attention of men for a quarter of a century. The first 
great pioneers had passed to the unknown or retired from active 
labors. We will discuss the views entertained at the beginning of the 
second quarter of this century, after which we will pass to modern 
and more practical matters. In the development of the peritonaeum 
the names of L. Fr. von Fro/iep (1779-1847, German anatomist and 
obstetrician), Lauth (1758-1826, professor of anatomy at Strasburg) 
and J. Mueller, stand prominently. The especial questions which 
man had to ask were («) How does the great omentum arise from the 
peritoneal sac ? (£) Why are the stomach and colon alone connected 
with it? (c) Why does the omentum arise in man and certain lower 
animals only and not in all ? 
The epoch-maker in the development of the peritonaeum was Jo- 
hannes Mueller, who published his labors in 1830. Mueller started 
his labors where others left off and by dissecting and examining many 
embryos under four months old, finally stated that he hoped he 
had discovered the cause of so noteworthy a formation as the great 
omentum. Mueller's idea was that the layers of the omentum coa- 
lesced and finally presented a double layer of peritonaeum reaching 
from the greater curvature of the stomach to the transverse colon and 
from the transverse colon to the posterior abdominal wall. From 
Fleischmann (1777-1850, German anatomist), Kieser (1779-1862, Ger- 
man biologist) and Meckel, Mueller knew that the digestive tract at 2 
Byron Robinson, M. D. 
first was a straight tube reaching from the heart to the cloaca. Also 
Oken (1779-1851, a German biologist whose name is connected with 
the Wolffian or Oken bodies) laid further foundations for Mueller's 
final conclusions. By this date (1830) it was well known that the 
stomach turned from the left to the right and that it also twisted on 
its axis and by these two processes in the second month of foetal life 
the stomach loses its perpendicular position in the body. He also 
knew from the labors of others that the digestive tract below made 
a peculiar long, parallel loop which passed out at the umbilicus and 
was connected at its pointed angle to the vitelline duct. This loop 
gradually returned into the abdominal cavity. Mueller considered it 
of noteworthy interest to investigate the connections of this intes- 
tinal loop to the abdominal wall after it returned. 
As is known in very young embryos (four weeks) the stomach is 
perpendicular ; hence the double fold of peritonaeum which holds it 
will also be perpendicular and arise from the middle of the dorsal 
wall. The double fold of peritonaeum which arises from the middle of 
the dorsal wall and passes to the posterior border of the upright stom- 
ach, was named by Mueller, the mesogaster. When the mesogaster 
arrives at the stomach, its two blades diverge to receive it and then 
pass forward on the right and left sides of the stomach until they 
arrive at the anterior or lesser curvature, after which the two blades 
of peritonaeum again come together and pass to the liver. The part 
of the double peritoneal membrane stretching from the stomach 
should be named the anterior mesogaster, but anatomists call it the 
gastro-hepatic omentum. .After clearly recognizing that the posterior 
mesogaster (great omentum) is the mesentery of the stomach or the 
double-bladed membrane stretching from its origin, the middle of the 
dorsal wall, to the posterior border of the stomach and that the ante- 
rior mesogaster (lesser omentum) is the double-bladed peritoneal <old 
which extends from the transverse fissure of the liver to the lesser 
curvature of the stomach, the story of the formation of the great 
omentum is simplified. 
In the second month of foetal life the stomach makes three move- 
ments : (tz) It rotates from left to right, it twists on its axis, and (f) 
it descends lower into the abdominal cavity. The result of the three 
movements is (<z) the right surface of the stomach becomes posterior 
and the left anterior and (Z>) the stomach assumes a horizontal position 
or rather the pylorus is carried backward. As the stomach passes 
through these movements the greater curvature is carried to the left 
and forward so that the mesogaster must necessarily elongate. The The Peritonceum. 
3 
mesogaster elongates by moving toward the left and in so doing it 
creates at first, a wide, shallow depression behind the stomach. As 
. the stomach completes its rotating and twisting the shallow depiession 
behind the stomach becomes deeper and the circumference of its 
mouth becomes narrower until, finally, in the fourth month the depres- 
sion becomes the lesser bag of omentum and its mouth becomes the 
foramen of Winslow (foramen epiploon), to use Johannes Mueller's 
words, from his original article in 1830, " Diese Beobachtung ist neu, 
und mir eigen ; sie ist, wie ich glaube, der Schiissel zur Bildungsge- 
schichte des grosses Netz." ("This observation is new and my own ; 
it is, as I believe, the key to the development of the great omentum.") 
Now, since the mesogaster arises from the middle line of the dor- 
sum and reaches around to the greater curvature of the stomach, there 
will exist behind the stomach a space or sac made by the folds of the 
elongated mesogastrium. In order to reach from the mid-dorsal line 
to the greater curvature of the stomach the mesogaster must needs 
stretch very much. The bag found behind the stomach gradually 
assumes such a position that the mouth opens just at the right of the 
vertebral column at the point known as Winslow's foramen. Wins- 
low's foramen should open in the middle line, but the liver (enor- 
mously large in embryos) atrophies rapidly and drags it to the right 
over the spinal column. Winslow's foramen opens at the lower part 
of the lesser curvature of the stomach. Now the anterior wall of the 
lesser omental cavity is the stomach itself, while the posterior wall is 
the mesogaster itself. This aperture, Winslow's foramen, is the nar- 
row neck leading to a wide bag of peritonaeum lying behind the 
stomach, known generally as the lesser omental cavity. The neck or 
foramen is at first simply a wide depression in the mesogastbr, but 
gradually the bag narrows at its neck, until it admits one to three 
finger tips in the adult. 
It should be noted that the mesogastrium and mesenterium of the 
duodenum are one and the same thing ; that the mesogaster ceases 
when the mesentery begins. In early embryos this is at the pylorus, 
but in adults it is at the junction of the duodenum and jejunum. In 
between the stomach and jejunum there is a piece of bowel in adults 
without a mesentery, lying behind the peritonaeum. It is the duo- 
denum. however, in embryos, in the lower animals the duodenum has 
a long mesentery. 
The notable feature in development of the great omentum and 
colon is that they remain a long time without any relation or contact. 
But the more the colon bends and fixes itself in a higher position the 4 
Byron. Robinson, M. D. 
more the great omentum assumes a bag-like form. At this time (say 
six weeks) the great omentum (mesogaster) assumes an oblique inser- 
tion and the mesentery of the colon also assumes an oblique or trans- 
verse insertion. The two more and more approach each other until 
the great omentum passes directly from the greater curvature of the 
stomach to the transverse colon. It has been asserted and reasserted 
that there is a coalescence or an absorption of some of the layers of 
the great omentum in order to produce the condition found in adults. 
I shall attempt to show, both by embryos and especially by the dog, 
that this is not the case, but that the whole matter concerning the 
relations of the great omentum and the transverse colon is brought 
about by a readjustment of parts. Certain organs in developing and 
assuming their positions appropriate portions of peritonaeum, while 
others give up some peritonaeum. It will be observed in both em- 
bryos and dogs that the final adjustment of the great omentum to 
the transverse colon in the adult begins at the right end of the trans- 
verse colon and progresses toward the left. The credit of announc- 
ing just how the omentum and transverse colon coalesced, Mueller 
gives to Meckel. Many ideas of the peritonaeum and its folds have 
been copied without the slightest recognition of the labors of 
Meckel and Mueller. But right here it would seem to me to be 
appropriate to copy the figures which Mueller drew sixty-five years 
ago to represent the development of the great omentum, a discovery 
which he says belongs to the industrious Meckel. However circum- 
stances forbid. 
I wish to state that I consider Mueller's figures as well as 
Meckel's views partially wrong. It should be remembered that 
what is transitional in man's embryo may be permanent in the lower 
animals. The great natural fact is that man goes through the devel- 
opment, in embryo, of all the animals below him. Hence we must 
learn the thread of progressive development by the examination, not 
only of the rapid transitional stages of man's embryo, but of the per- 
manent stages of the lower animals. The dog, for example illustrates 
a peculiar permanent condition of a stage of development far below 
man in two special conditions. One represents the partial rotation 
of the intestinal canal. The caecum remains near the navel and does 
not descend. Another is that the great omentum does not directly 
insert itself into the colon at all. 
In some mammals the omentum will remain bag formed. In 
others it still remains a part of the original mesentery, i. e., the meso- 
gaster may remain a simple mesentery of the stomach or it may show The Peritonaeum. 
5 
different degrees of sac formations as dog and man. Also a peculiar 
point arises that the spleen may be far away from the stomach as in 
man or directly in contact with the stomach as in embryos and some 
animals. Again in man one can easily observe that the pancreas is 
posterior to the peritonaeum, but in the dog it is distinctly in the 
mesentery in contact with the stomach and duodenum. The same may 
be observed in certain stages of human embryos. Further, the foramen 
of Winslow is large in human foetuses, but the same opening in some 
other animals is hardly an inlet at all, but a wide plane or depression. 
Hoffman's sloth simply has a wide-mouthed bag for a lesser omental 
cavity, so that this omentum as found in man is the result of long 
ages of evolutionary development. But one can observe the evolution 
of unnumbered ages in nine months of foetal life. In fact the changes 
in man during intra uterine life are more wonderful than those after 
birth. 
The following remarks on the abdominal viscera and peritonaeum 
of a foetus of perhaps four months and a half may be of interest: 
Foetus, male. Five inches long. Fingers and toes distinctly formed. 
.Nails visible. No eyebrows or hair. The external genital organs are 
just beginning to be distinctly recognizable to decide sex. The rhaphe 
is closed. The abdomen is very large on account of the large liver. The 
liver is almost symmetrical, but still the larger lobe is the right. The 
umbilical vein being cut, the fold of abdominal wall containing the two 
hypogastric arteries and the urachus is turned down for the best view. 
The testicles are descended to the internal inguinal ring. The 
right testicle, like the right corner of the uterus, does not descend as 
fast as the left. The sigmoid flexure is three quarters of an inch long. 
Its mesentery is directly in the middle line, until it was entirely dis- 
placed by the growing kidney The kidney appropriated all of the 
mesentery of the descending colon so that the descending colon runs 
along the outer border of the kidney. The bowel is solidly adherent 
to the kidney. Then we have no descending meso-colon and the 
only primitive mesentery left on the large bowel is the sigmoid mes- 
entery, which in this foetus of five inches arises exactly in the middle 
line of the dorsal abdominal wall. The descending colon is half an 
inch long. The costo-colic ligament shows distinctly in this foetus to 
be the lower left-hand border of the great omentum. The trans- 
verse colon is nearly an inch. The omentum is over half an inch 
from the colon to its lower border. The descending colon is half an 
inch long. It makes a wide, obtuse angle, unlike the splenic bend, 
which is a sharp, acute angle. The descending colon runs on the 6 
Byron Robinson, M. D. 
internal border of the kidney and is tightly adherent to the kidnev. 
It has no mesentery. It may be observed that both ascending and 
descending colons are more fixed and have a shorter mesentery at 
their upper ends or at their flexures than they have at their lower. A 
fact which holds good in adults. 
The appendix is half an inch long, ft runs parallel to the lower 
end of the ilium. It has a mesentery. It lies in a spiral form and 
the fold of peritonaeum stretches from the ilium on to it at both its 
sides. It is so small that the superior and inferior ileo-caecal fossa can 
not be distinctly marked out. This foetus shows very clearly that the 
ascending colon as it descends appropriates the mesoduodenum for 
its own covering. The descending colon lies for a quarter of an inch 
against the front surface of the duodenum and at that point has no 
peritonaeum over it, but the peritonaeum is used to cover the ascend- 
ing colon. As the ascending colon descends it drags the right lower 
omental border with it out into a conical point. Besides the splenic 
flexure has become also quite firmly fixed into the (costo-colic liga- 
ment) left lower border of the great omentum. The gall-bladder is 
nearly half an inch long. The stomach has assumed an adult con- 
dition. The spleen lies against the left end of the stomach. The 
pancreas can be seen lying in the great omentum, but it is being un- 
covered by the dragging of the ascending colon. 
The lesser omentum stretches from the liver to the stomach. It 
is a thin transparent membrane, however, of considerable strength. 
The whole of the small intestines hang on a very narrow neck and 
the mesentery crosses the. vertebral column and great vessels at a 
very high point, much higher than in adults. 
The jejunum is about twice the size of the colon. In this foetus 
of five inches the colon does not show a trace of sacculation, or longi- 
tudinal bands or appendicae epiploicae. In fact the colon throughout 
its length is in this foetus the smallest part of the digestive tract. The 
upper end of the jejunum is three times the size of the colon. The 
mesogaster inserts itself in the posterior median line. 
The small intestine is fifteen inches long. The large is three 
inches long. It is as one to five, almost adult relations. 
This foetus is five inches long and about four months old. At 
this age we may note the following points. The ascending and de- 
scending colons have no mesentery, the kidney on each side has 
appropriated it to cover its rapidly increasing volume. The splenic 
flexure is acute as it is in adults. The transverse meso-colon is four 
fifths of an inch. The hepatic angle is obtuse and the caecum has The Peritonceum. 
7 
descended to the lower border of the left kidney. The colon has no 
sacculations, bands or appendices epiploicae. The colon is the small- 
est part of the digestive tract. The omenta (gastro-hepatic, gastro- 
colic and gastro-splenic) are definitely formed. A very curious mat- 
ter in the small intestine of this foetus is that at some six inches below 
the beginning of the jejunum the gut widens and retains a large 
caliber up to three inches from the caecum, when it rapidly narrows. 
The liver has just begun to lose its symmetry and is perceptibly 
large in the right lobe. The point where the round (hepatic) liga- 
ment of the liver comes out between the two lobes is exactly at the 
level of the umbilicus and before the liver begins to perceptibly shrink 
in one lobe this point extends below the navel. A peculiar, but 
general feature of the foetus is, that the descending colon, is, at four 
months always at the left border of the kidney and with no mesen- 
tery, while the ascending colon is at the left border of the right kidney. 
However, I posted an adult in which the ascending colon lay on the left 
border of the right kidney, but no doubt that was a foetal type. The 
duodenum is being deprived of its mesentery by the ascending colon. 
The appendix is rapidly approaching adult conditions. The kidney 
is half an inch long. The mesentery has a higher position than in 
the adult. The hepato-duodenal ligament is large and prominent. 
No trace of the fossa duodeno-jejunalis can be made out. The sig- 
moid mesentery arises directly from the middle line and it is broken 
by the kidney stealing away the mesentery of the descending colon. 
No under sigmoid fossa can be found. The abdomen was fully closed 
at the navel. The rotation of the digestive tract is almost completed. 
'There is no trace of Meckel's diverticulum. The urachus rapidly 
tapers from the bladder and is quickly lost between the two hypo- 
gastric arteries.