THE INTESTINES. 401 



the organ. Removed from the abdominal cavity, freed from the serous folds 

 which suspend it, and distended by air or water, this disposition of tho 

 small intestine naturally causes it to twist in a spiral manner. 



Course and Relations. The small intestine commences at the right cul- 

 de-sac of the stomach, from which it is separated by the pyloric constriction. 

 At its origin it presents a dilatation which, in form, closely simulates a small 

 stomach, whose curvatures are the inverse of those of the proper stomach. 

 Placed at the posterior face of the liver, this expansion, or head, of the small 

 intestine begins the narrower portion, which at first is directed forward, 

 then bends suddenly backward : thus forming a loop investing the base of 

 the caecum on the right side ; then it is carried to the left in crossing, trans- 

 versely, the sublumbar region, behind the great mesenteric artery ; here it is 

 joined to the origin of the floating colon by a very short serous fraenum. It 

 then reaches the left flank, where it is lodged, and where it forms numerous 

 folds that are freely suspended in the abdominal cavity among the convolu- 

 tions of the small colon. The terminal portion of this conduit, which is 

 easily recognised by the greater thickness of its walls and its smaller 

 diameter, disengages itself from these convolutions to return to the right, 

 and opens into the concavity of the caecum, below, and a little to the inside 

 of, the point where the large colon has its commencement. 



In the language of the schools, this terminal portion is named the ileum 

 (eiXetv, to twist) ; the part which is suspended in the left flank, and which 

 forms the principal mass of the intestine, is designated the jejunum (jejunus, 

 empty) ; and the curvature formed by this viscera at its origin, from the 

 pylorus to the great mesenteric artery, is termed the duodenum (twelve 

 fingers' breadth). 



This classical division is, however, altogether arbitrary, and scarcely 

 deserves to be retained, It would be better to divide the intestine into a 

 fixed or duodenal, and a free or floating portion. 



Mode of attachment. The small intestine is maintained in its position, 

 at its extremities, by the stomach and the caecum. But its principal means 

 of fixation consists in a vast peritoneal fold, which, from its use, is named 

 the mesentery (//.cow, orrcpov). 



This serous layer presents a very narrow anterior part which sustains 

 the duodenum, and fixes it in such a manner as to prevent its experiencing 

 any considerable displacement. Continuous, in front, with the gastro-hepatic 

 omentum, this portion of the mesentery is successively detached from the 

 base of tho liver, the inferior aspect of the right kidney, or even from the 

 external contour of the base of the caecum, and, lastly, from the sublumbar 

 region, to be soon confounded with the principal mesentery. This becomes 

 wider as it approaches the caecal extremity, and arises, as from a centre, from 

 the outline of the great mesenteric artery, to spread in every direction, and 

 is inserted into the small curvature of the floating portion of the viscus. 

 The great length of this insertion causes it to become extended in a spiral 

 or screw-like manner, around its point of origin. It may be remarked that 

 the terminal extremity of the intestine is retained between the two serous 

 layers of the mesentery, to a certain distance from its free border. This 

 peritoneal fold consequently forms at this point, at the side opposite to 

 its insertion into the intestinal tube, a particular fraenum, which is observed 

 to be carried to the anterior face of the caecum. 



Interior. The interior of the cylindrical tube formed by the small 

 intestine offers longitudinal folds, which are effaced by distention, except 

 towards the origin of the duodenal portion. Those met with in this situation 



