DISSECTION OF THE ABDOMEN. 311 



Orifices of the Crook. — These are the apertures of communication with 

 the ileum, and with the large colon. At its termination the ileum pro- 

 jects slightly into the interior of the csecum, and beneath the mucous 

 membrane surroimding the orifice, there is developed a ring of mus- 

 cular fibres. This fold of mucous membrane with its included muscular 

 fibres constitutes the ileo-coecal valve. The opening of communication 

 with the colon is considerably larger than the preceding, above which 

 it is placed. 



Directions. — The student must now retin-n to the parts left within the 

 abdominal cavity, where, without further dissection, he will be able to 

 examine the stomach, spleen, pancreas, and liver. Should the stomach 

 be nearly empty, the ligature should be untied from the cut end of the 

 duodenum, and by means of bellows that intestine and the stomach 

 should be moderately inflated. To permit this, it will not be necessary 

 to ligature the oesophagus. At the present stage the above-mentioned 

 organs may be studied as regards their form, situation, and relations, 

 their structure being postponed for future consideration. 



The Stomach (Plates 43 and 44) is the most dilated segment of the 

 alimentary tube. When moderately distended, it will be seen to have 

 the folloAving configuration. It possesses an anterior and a posterior 

 surface, both being smoothly rounded. It has a concave or lesser cur- 

 vature, which is turned upwards and to the right; and a convex or 

 greater curvature, which is directed downwards and to the left. The 

 left extremity of the organ is much the larger, and is termed the 

 cardiac extremity, or the fundus. The smaller right end is termed 

 the pylo^'us. The stomach occupies the epigastric and left hj-po- 

 chondriac regions, and it will be observed to have the following 

 connections. The anterior surface is related to both the liver and 

 the diaphragm, and in the natural position looks upwards as well as 

 forwards. The posterior face looks downwards as well as backwards, 

 and before the removal of the intestines was related to these, and 

 chiefly to the gastro-hepatic flexure of the double colon. The smaller 

 curvature is fixed to the liver by means of the gastro-hepatic omentum. 

 If, in the present inverted position of the animal, the greater curvature 

 be pulled backwards, so as to separate the anterior surface from the 

 liver and diaphragm, the esophagus will be found entering the stomach 

 at its lesser curvature, about midway between the central point of 

 that curvature and the extremity of the fundus. The greater curvature 

 is related in its left half to the spleen, and throughout the rest of 

 its extent to the intestines, particularly to the suprasternal flexure of 

 the colon, now removed. The right extremity, or pylorus, is directly 

 continued into the duodenum, a slight constriction being the only 

 outward mark of their separation. The left or cardiac extremity 

 extends to the left beyond the insertion of the oesophagus, and is related 



