310 THE ANATOMY OF THE HORSE. 



arrangement that the membrane possesses a lace-like appearance. The 

 two layers of the omentum may be distinguished as superficial and deep. 



When the superficial layer is traced backwards it is seen to pass on 

 to the terminal part of the double colon (4th part) and initial part of 

 the single colon, covering the posterior aspect of these where they extend 

 across the roof of the abdominal cavity. Behind these it passes back- 

 wards along the roof of the abdominal cavity, from which it descends to 

 envelop the small intestine, forming the great mesentery, and the float- 

 ing colon, forming the colic mesentery. To the right, again, it passes 

 directly on to the caecum and the double colon ; and, after enveloping 

 these intestines, it returns to the abdominal wall, to pursue its back- 

 ward course to the pelvis. When followed forwards, the superficial 

 layer reaches the convex curvature of the stomach and the initial dila- 

 tation of the duodenum j and it passes over the anterior surfaces of 

 these organs as visceral peritoneum. Passing off the duodenum and 

 stomach, it next forms the anterior layer of the gastro-hepatic omen- 

 tum, and thus reaches the posterior surface of the liver at the portal 

 fissure. From that point it descends over the posterior surface of the 

 liver as visceral peritoneum, and turns round the inferior edge of the 

 gland to gain its diaphragmatic surface. It ascends on this surface : 

 and where the liver and diaphragm are united it passes from the former 

 to the latter, on which it descends to the inferior wall of the abdomen. 

 Along this it passes until it enters the pelvis, where it becomes continuous 

 with the same layer already followed backwards along the roof of the 

 abdomen. In the male it is to be observed that the parietal peritoneum 

 of the abdominal floor passes into the inguinal canal, and forms the 

 tunica vaginalis of the testicle, the sac of which is a simple diverticulum 

 of the great peritoneal sac. Returning again to the omentum, it will 

 be noticed that its superficial layer, towards the left side, in passing 

 forwards to gain the convex curvature of the stomach, encounters the 

 spleen. Passing round that organ, it gives to it a visceral covering, and 

 then continues its course to the stomach. The portion of omentum 

 between the spleen and the left sac of the stomach is termed the gastro- 

 splenic omentum. 



Now make a transverse opening about the centre of the great omen- 

 tum, and introduce the hand through the opening. The hand is now in 

 what is termed the cavity of Window, and the deep layer of the omen- 

 tum is exposed. When this layer is traced forwards it is seen to reach 

 the convex curvature of the stomach, where, separating from the super- 

 ficial layer, it passes over the posterior surface of the stomach and 

 initial dilatation of the duodenum. From these, again, it passes as the 

 posterior layer of the gastro-hepatic omentum, and reaches the liver at 

 the portal fissure. There it separates from the other layer of the gastro- 

 hepatic omentum, and ascends on the liver. It turns round the 



