326 



ABDOMEN 



and an internal stratum of circular fibres. The circular layer 

 is the thicker and more distinct of the two. The external 

 longitudinal fibres are spread out, in the form of a thin con- 

 tinuous layer, all round the circumference of the intestine, 

 but the layer is thickest in that part of the wall which is 

 furthest from the mesenteric attachment. The submucous coat 

 is composed of loose areolar tissue which binds the muscular 



to the mucous coat. It 

 is more firmly connected 

 with the latter than the 

 former. The mucous coat 

 must be examined 

 throughout the whole 

 length of the jejunum and 

 ileum. 



FIG. 150. Typical part of Jejunum, show- 

 ing numerous and large Plicae Circulares. 



Dissection. It has 



already been noted that 

 little distinction can be 

 drawn between the up- 

 per and lower parts of 

 the small intestine from 

 their external appear- 

 ances, beyond the fact 

 that as the intestine 

 descends it diminishes 

 slightly in calibre and 

 its walls diminish in 

 thickness (cp. p. 273). 

 The internal appear- 

 ances of the upper part 

 of the jejunum and the 



lower part of the ileum, on the other hand, are very different, 

 and the small intestine must now be opened in order that the 

 internal difference may be investigated. In the first place, 

 however, remove about 30 cm. (twelve inches) of the upper 

 part of the jejunum ; ligature it at both ends and distend it 

 with air by means of a blow-pipe ; then hang it up to dry, in 

 order that the folds of the mucous membrane, called plicce 

 circulares, may be investigated in their entirety. The best way 

 to open the remainder of the small intestine is to tie a ligature 

 round the lower cut end of the ileum and then fill the gut as 

 full as possible with water. When that has been done take 

 the scissors and impale a small piece of costal cartilage on the 

 point of one blade. Introduce the blade, so protected, into the 

 gut and run the scissors downwards along the line of the 

 attachment of the mesentery. If the procedure described is 

 followed the gut will easily be laid open from end to end. 



Mucous Membrane of the Small Intestine. "Yte plica circu- 

 lares (O.T. valvula conniventes] are the most conspicuous objects 



