680 ESSAY ON THE DESCRIPTIVE ANATOMY OF THE 
It is also obvious that, as situation, attachment, and shape of 
each portion of the intestinal canal differ, so must the relations 
be equally distinct, and further mention of them will therefore 
be reserved for fuller exposition elsewhere. 
Small Intestine. 
This, the smallest although longest, is also the first portion 
of the intestinal tube, extending from the pylorus to its sudden 
termination into the large intestine. In it the chymified mass 
is subjected to the modifying influence of important secretions, 
whereby its nutritive parts are fitted for absorption by the 
vessels which for this purpose are arranged in this portion of 
the intestinal track. 
The small intestine has been divided into three parts : this 
classification is, however, purely conventional. Since it does 
not recognize anatomical differences for its basis, it might justly 
be presumed that this distinction of human anatomists exhibited 
traces of imperfection, even when applied to the frame of man. 
Such being the case, it is no matter of surprise that, in referring 
the distinction to the intestinal canal of animals, the incongru- 
ities of the system should be still more apparent. 
Extending from the pylorus, the first portion is termed the 
duodenum, from its being considered as twelve fingers’ breadth 
in length : it is, however, extended round to the left side of 
the spine, posteriorly to the anterior mesenteric artery. The 
middle or floating portion of gut takes the name of jejunum, 
and the third or crncal portion is distinctively designated ileum. 
The duodenum forms a wide curve from the pylorus round 
to the right, being situated under the concave surface of the 
liver, passing above the transverse colon, so as to attain the 
posterior part of the mesentery, and, reaching the left side of the 
spine, comes in contact with the colon, where it is said to end 
in the jejunum. The duodenum is fixed by the gastro-hepatic 
omentum to the concave surface of the liver, the layers of which 
enclose the biliary and pancreatic ducts, whereby this bond of 
union is still further strengthened. The peritoneum coming 
from the right and spigelian lobes of the liver, as well as from 
the right kidney, forms a loose attachment for the duodenum by 
extending on to the hepatic flexure of the colon after it has sur- 
rounded the first-named gut. The next portion of intestine is 
attached to the spine transversely to the long axis of the body ; 
winding round the mesentery to the left of the aorta, it gets 
attached to the gastric flexure of the colon, and here it proceeds, 
under the name of jejunum, along the free borders of the 
mesentery. 
