322 THE ANATOMY OF THE HORSE. 



greatest just beyond the pylorus, and at this point it presents, when 

 inflated, a small dilatation like a miniature stomach with its greater 

 curvature superior. Throughout the whole of its course it is retained 

 in position by a narrow band of peritoneum formed by the serous 

 membrane as it passes to envelop the bowel. The right extremity of 

 the pancreas rests against the duodenum, a few inches from the pylorus, 

 and at that point the wall of the bowel is perforated by the bile and 

 pancreatic ducts. 



The Spleen (Plates 43 and 44) is a bluish-purple solid organ placed 

 in close proximity to the left sac of the stomach. In the horse it has 

 a scythe-shaped outline. It presents an external face, which is slightly 

 convex ; an internal face, which is slightly concave and narrower than 

 the outer ; an anterior thick border ; and a posterior border, which is 

 sharp. Its surfaces are widest above, where they terminate in the base 

 of the organ, and below they taper to the apex. The spleen is situated 

 in the left hypochondriac region, and has the following relations : Its 

 outer surface is related to the diaphragm ; its inner surface contacts with 

 the double colon ; its anterior border is penetrated by the vessels and 

 nerves of the organ, and is related to the greater curvature of the 

 stomach ; its posterior border is free, and is included between the intes- 

 tines and the diaphragm ; its base is related to the pancreas and left 

 kidney. The spleen is retained in the left hypochondrium by the gastro- 

 splenic omentum, and by a special splenic ligament. The g astro-splenic 

 omentum forms a loose connection between the left half of the greater 

 curvature of the stomach and the anterior border of the spleen. The 

 splenic ligament is a fold of peritoneum developed at the base of the 

 organ, and formed by the serous membrane in passing from around the 

 anterior end of the left kidney to envelop the spleen. 



The Pancreas (Plate 44) is a body having a lobulated structure and a 

 very irregular shape. It is placed across the roof of the abdominal cavity, 

 its central portion underlying the last dorsal vertebras. Its upper face 

 is applied to the aorta, the coeliac axis, the vena cava, the pillars of the 

 diaphragm, and the right kidney, and is partly covered by peritoneum. 

 Its lower face towards the right is adherent to the crook of the caecum 

 and the termination of the double colon, while to the left it is covered 

 by peritoneum. Its anterior border is related to the stomach, the 

 duodenum, and the liver. Its posterior border is related about its centre 

 to the anterior mesenteric artery. Its right extremity, or head, is in 

 contact with the duodenum ; while the left extremity, or tail, is related 

 to the base of the spleen. The entire thickness of the gland is perforated 

 by the portal vein, which passes from its lower to its upper surface 

 through what is named the pancreatic ring. The gland possesses two 

 excretory ducts, both of which leave it at its right extremity. The main 

 duct is named the duct of Wirsung, and it perforates the w T all of the 



