96 TOPOGRAPHICAL ANATOMY OF THE 



phragmatic flexure, and the right dorsal colon, which bring the tube 

 back again to the neighbourhood of the pelvic inlet. 



If now the left portion of the great colon be raised, some coils of the 

 small colon and the small intestine will be disclosed. Not infrequently 

 short lengths of these parts of the intestinal tube are visible without 

 disturbance of the great colon. The small intestine is readily 

 distinguished from the small colon by the absence of those sacculations 

 that produce the characteristic appearance of the large intestine of 

 the horse. 



It is worthy of note that, in the horse, neither the stomach nor the 

 liver are visible before disturbance of the intestinal mass. That is, 

 neither of these organs is in contact with the ventral wall of the 

 abdomen. 



Dissection. — After a general survey of the intestines has been made 

 as above, the dissector should lift the left ventral and left dorsal colon 

 out of the abdomen and straighten out the ventral and dorsal diaphrag- 

 matic flexures. This will permit him to examine the whole intestinal 

 tube with the exception of the first and last portions. 



The small intestine (Intestinum tenue). — The small intestine is 

 a fairly uniform tube about G-8 cm. in average width and some 20 metres 

 in length. It extends from the pylorus, where it is continuous with the 

 stomach, to the lesser curvature of the csecum. The greater part of the 

 tube, in company with the small colon, occupies the dorsal and left part 

 of the abdomen, but, owing to its mobility, portions of it may be found 

 in other regions. 



The small intestine is divided into — (1) The duodenum ; ^ (2) the 

 jejunum^ (intestinum jejunum); and (3) the ileum'^ (intestinum 

 ileum). The coils of the jejunum and ileum are freely movable, since 

 they are suspended from the dorsal wall of the abdomen by a long fan- 

 shaped sheet of peritoneum, the mesentery * (mesenterium) ; but the 

 duodenum, being provided with a very short fold of peritoneum 

 (mesoduodenum), is incapable of much displacement. 



A definite line of demarcation between the jejenum and ileum 

 cannot be determined. Generally, in the dissection subject, the ileum 

 is the more contracted part of the tube, though when in the flaccid 

 condition it is the wider. The last part of the ileum, however, is not 



^ Duodeni [L.], twelve each, by twelves, twelve. This part of the small 

 intestine is so called because in man its length is about twelve finger-breadths. 



^ Jejunus [L.], emjity. 



■^ Ileum [L.], elXeii/ (eilein) [Gr.], to roll up, to twist. This part of the intestine 

 is so named from its numerous coils in man. Horace uses ilia (the ilank) to indicate 

 the entrails of animals. 



* M^o-oj (mesos) [Gr.], middle ; ivrepov (enteron) [Gr.], bowel. 



