THE ABDOMINAL VISCEEA. 1419 



of the small intestine. For descriptive purposes it is divided by anatomists into 

 three parts. From the surgical standpoint it may with advantage be subdivided 

 into a supra-colic and an infra-colic portion, the former, comprising the superior and 

 the upper half of the descending part, being situated above the attachment of the 

 transverse mesocolon ; while the latter, comprising the lower half of the descending 

 part along with both subdivisions of the third part, being situated below this 

 attachment. To expose the supra-colic portion the greater omentum and the 

 transverse colon must be pulled downwards, while to expose the infra-colic portion 

 they are thrown upwards along with the transverse mesocolon. 



The first portion proper (pars superior) lies in the right part of the epigastric 

 region, medial to the gall-bladder, where it is overlapped by the quadrate lobe of 

 the liver. As regards its blood-supply, it occupies the frontier zone between the 

 coeliac and superior mesenteric vascular areas, and the vessels which supply it 

 vary considerably in their size and mode of origin. 



This peculiarity of its blood- supply may partly account for the relative 

 frequency with which this portion of the intestine is found to be the seat of 

 ulceration. The first inch or so the duodenum possesses some degree of mobility, 

 being surrounded by the same two layers of peritoneum which invest the stomach. 

 Beyond this it is in direct contact posteriorly and inferiorly with the pancreas, 

 while descending behind it are the common bile-duct and the gastro-duodenal 

 artery. The relations must be borne in inind in performing the operation of 

 pylorectomy. When an ulcer of the superior part perforates, extravasation takes 

 place, in the first instance, into the supra-colic compartment of the peritoneum, 

 thence into its hepato-renal pouch, and subsequently down along the ascending 

 colon into the right iliac fossa, hence the possibility of mistaking the condition 

 for an acute appendicitis. Perforation of the ulcer, however, is often prevented 

 by the duodenum becoming adherent especially to the gall-bladder, to the omentum, 

 or to the transverse colon. 



If the finger is passed upwards, backwards, and to the left, immediately above 

 the first part of the duodenum and behind the right free border of the lesser 

 omentum, it will pass through the foramen epiploicuin into the omental bursa of 

 the peritoneum. 



The second portion of the duodenum (pars descendens) descends in the epigastric 

 and umbilical regions a little medial to the right lateral plane. The attachment 

 of the transverse mesocolon crosses it about its middle, while posteriorly it lies in 

 front of the hilum and medial border of the right kidney, from which it is separated 

 by loose areolar tissue. The procedure necessary to mobilise this portion of the 

 duodenum has been referred to already. 



The horizontal portion of the inferior part of the duodenum occupies the 

 superior part of the umbilical region, and crosses the median plane about one inch 

 above a line joining the highest part of the iliac crests ; behind its commencement 

 is the superior part of the right ureter. 



The ascending portion of the inferior part of the duodenum crosses the infra- 

 costal plane, and ascends upon the left side of the vertebral column opposite the 

 second and third lumbar vertebra. 



The duodeno-jejunal flexure, which lies in the transpyloric plane one inch to the 

 left of the median plane, is the landmark which the surgeon makes for when he 

 wishes to identify the commencement of the jejunum (Fig. 946, p. 1204). To find 

 the flexure the greater omentum and transverse colon should be thrown upwards 

 and the finger passed along the inferior layer of the transverse mesocolon to the 

 left side of the vertebral column. The flexure lies in the angle or recess formed by 

 the left side of the second lumbar vertebra and the inferior surface of the body of 

 the pancreas. With the finger in this recess the commencement of the jejunum 

 may be hooked forward a little to the left of the superior mesenteric vessels at 

 the root of the mesentery. In connexion with the duodeno-jejunal junction is the 

 inferior duodenal fossa of Jonnesco, formed by a fold of peritoneum which stretches 

 from the left side of the fourth or ascending part of the duodenum upwards 

 to become attached to the peritoneum of the posterior abdominal wall close to the 

 medial border of the left kidney. The free edge of the fold and the mouth of the 



