942 
selves, by using great care in manipulation, 
that it is not the result of violence; it exists 
also in the mesenteries of same animals. 
The arteries that ramify in the great omen- 
tum are branches of the gastro-epiploica dextra 
and sinistra, and some anastomosing ones from 
the colica media which pass round the colon 
and enter the omentum on the side of the in- 
testine opposite to that on which the artery 
reaches it. Veins and doubtless nerves accom- 
pany these arteries, and there are some lym- 
phatic glands enclosed between the layers of the 
great omentum along the greater curvature of 
the stomach. 
The use of the great omentum has never 
been satisfactorily pointed out. It is peculiar 
to, and universal in, the class Mammalia, and 
therefore always co-exists with a diaphragm ; 
probably it has some reference to the incessant 
motion and constantly recurring compression to 
which the intestines are subject from the action 
of that muscle in respiration. It is frequently 
seen dipping very deeply between the convo- 
lutions of the intestines, and occupying their 
interspaces as a moveable packing material, 
as if thereby enabling them to retain their 
cylindrical form whilst subject to incessant 
disturbance. 
The great omentum, being continuous as one 
sheet with the splenic omentum, may be re- 
garded as a great pouch or widening of the 
mesentery of the stomach. In those animals, 
such as the Carnivora, which have a very short 
colon, the great omentum does not extend from 
the stomach to the colon, but from the stomach 
to the pancreas, or to a transverse line of attach- 
ment corresponding in position with that of the 
transverse part of the duodenum in the human 
subject. e large intestine in these animals 
crosses over the small intestine at a point very 
near the termination of the latter in the cecum, 
that is to say, over the lower part of the ileum, 
where it usually has a proper mesentery.* 
The annexed drawing represents the abdo- 
minal viscera of a lizard, There is a prepa- 
ration, showing the same parts of a lizard, 
in the Hunterian collection, (No. 444 D, Phy- 
siological Series.) The whole of the intestines 
of this animal, from the esophagus to the 
rectum, are copnected to the posterior abdo- 
minal parietes by one continuous mesentery 
attached along the mesial line. In the sheet 
situated anterior to the stomach, connecting 
that organ to the liver and enclosing the gall- 
duct in its free edge, we recognise the lesser 
omentum in what we heretofore considered its 
typical position. In that part of the mesentery 
which connects the upper part of the stomach 
to the posterior parietes we recognise the sple- 
netic omentum ; the spleen is seen enclosed 
between its layers—apparently a large mesen- 
teric gland. That art of the common mesen- 
tery which, immediately succeeding the last 
mentioned, connects the middle and lower part 
of the stomach to the parietes, we cannot help 
regarding as the great omentum (the pancreas 
* Insome Carnivora, as the cat, the large intes~ 
tine cannot be said fairly to pass over the small in- 
testine at all. 
is just below this). Now pouch out this p . 
towards the left, and a great omentum, nee 
PERITONEUM. 
LZ” 
Abdominal viscera of a Lizard, 
a, stomach ; 5, liver; c, lesseromentam; d, gall- — 
duct; e, duodenum; /, pancreas; g, great omen- 
tum; h, spleen; i, cecum; k, ovary and kidney; 
I, lung. :, 
is found in the Carnivora, is produced, with the 
same relation of other parts, except in the obli- 
quity of the parietal attachment in the last- 
named animals, which is but slight. We have 
but to enclose the transverse colon between th 
layers of this sac, to obliterate that portion o 
the mesentery which is connected to the pan- 
creas and duodenum, and to carry the trans 
verse portion of the latter across just in the line 
of parietal attachment, in order to uce the 
condition of the parts which exists in man. J 
will readily be perceived how, in the me: 
time, a foramen of Winslow will have bee 
formed by this imaginary manipulation.* W 
should deem this pouching or widening of t 
gastric mesentery to have reference to the gn 
distention to which the stomach is liable, b 
that the sac is far too ample to be obliterated b 
any possible distention of that organ. 
he transverse mesocolon, formed of t 
layers of peritoneum, derived as described abo 
is about six inches broad in the middle, a 
gradually narrows off on each side. It reta 
the transverse portion of the colon in situ, 
transmits the veins, arteries, and nerves to | 
part of the intestine. At its root its two Tay 
separate, leaving a prismoid space, which | 
* The whole duodenum of many mammal 
animals, the cat for instance, has a mesentery 
that case the lower boundary of the fe 
Winslow is determined by the hepatic 
s, so that no part of itis ra 
these animals this portion of the 
passes off downw 
verse. 
