SMALL INTESTINE. 



1209 



to the other, if cut across a very short distance from the posterior abdominal wall, it will here be 

 found to form a wavy or undulating line. Further away still this condition becomes more and more 

 marked ; and finally, if the bowel is removed by cutting through the mesentery close to its attach- 

 ment to the intestinal wall, it will be seen that its free edge is not only undulating, but is frilled or 

 plaited to an extreme degree. When shown in this way, it is found that the plaiting or folding 

 is not quite indiscriminate, but that the main folds, of which there are usually six, run alter- 

 nately to the right and left. As a rule, the first fold runs to the left from the duodeno-jejunal 

 flexure, and goes to a coil of jejunum which lies under the transverse mesocolon, and helps to 

 support the stomach. The second fold passes to the right, the third to the left, and so on up to 

 the fifth and sixth, which are usually small. From the margins of these primary folds secondary 

 folds project in all directions, and from these again even a third series may be formed. 



6th costal cartilage 



Yth costal cartilage 

 Lig. teres 



8th costal cartilage 



Gall-bladder 



9th costal cartilage 



Liver 



10th costal cartilage 



Duodenum 



Right flexure of colon 

 Kidney 



Caecun 

 Ileun 



Vermiform process ._ 



-Xiphoid process 

 -,6th costal cartilage 



f-Ttli costal cartilage 



i~ Stomach 

 -.8th costal cartilage 

 Transverse colon 

 -9th costal cartilage 



-10th costal cartilage 

 -_ Duodeno-jejunal 

 flexure 



-Kidney 



-Descending colon 

 -Mesentery, (cut) 



Bifurcation of abdominal 

 aorta 



..Iliac colon 

 -Pelvic colon 



-Urinary bladder 



.FIG. 949. ABDOMEN, AFTER REMOVAL OF SMALL INTESTINE. 



This order is of course by no means constant, but if the intestine is removed from a hardened 

 body in the way suggested, without disturbing the mesentery, it will be found to be arranged 

 with more or less regularity, on some such plan as that indicated. 



Differences between Jejunum and Ileum. If the small intestine is followed 

 down from the duodenum to the caecum no noticeable change in appearance will 

 be found at any one part of its course, to indicate the transition from jejunum to 

 ileum ; for the one passes insensibly into the other. Nevertheless, a gradual change 

 takes place, and if typical parts of the two, namely, the upper portion of the 

 jejunum and the lower portion of the ileum, is examined, they will be found to 

 present characteristic differences, which are set forth in the following table : 



Jejunum. 



Wider, 1J- to 1^ inch in diameter. 

 Wall, thicker and heavier. 

 Redder and more vascular. 

 Plicae circulares, well developed. 

 Noduli lymphatici aggregati [Peyeri], 

 few and small. 



Ileum. 



Narrower, lj to 1 inch in diameter. 

 Wall, thinner and lighter. 

 Paler and less vascular. 

 Plicae circulares, absent or very small. 

 Noduli lymphatici aggregati [Peyeri], large 

 and numerous. 



