DISSECTION OF THE ABDOMEN. 325 



in the posterior fissure, and (2) a group, between the portal vein and 

 the pancreas. The glands of the spleen are placed on the course of 

 the splenic vessels. The lymphatic vessels emanating from the 

 stomach, liver, and spleen traverse these groups of glands; and, after 

 anastomosing with each other, they pass to the thoracic duct. 



The Bile Duct. This is the main duct for the conveyance of the 

 bile from the liver to the intestine. It is formed at the portal fissure 

 of the liver, by the union of secondary branches from the three principal 

 lobes, and it passes between the layers of the gastro-hepatic omentum to 

 penetrate the wall of the duodenum, about six inches from the pylorus. 

 The excretory apparatus of the horse's liver has the peculiarity — shared 

 by a few other animals — of being without a gall-bladder. 



The Celiac Axis (Plates 43 and 44) is a collateral branch of the 

 abdominal aorta, arising from the inferior face of that vessel between 

 the pillars of the diaphragm. It is less than an inch in length, and it 

 divides into three branches : the gastric trunk, the hepatic artery, and 

 the splenic artery. 



The Hepatic Artery is directed obliquely forwards, downwards, and 

 to the right, to gain the posterior fissure of the liver, which it penetrates 

 in company with the portal vein and the bile duct. At first embedded 

 in the pancreas, it then passes over the duodenum, and reaches its des- 

 tination by passing between the layers of the gastro-hepatic omentum. 

 It crosses the posterior vena cava, from which it is separated by the 

 foramen of Winslow. It gives off the following collateral branches : — 



1. Pancreatic Branches. 



2. The Right Gastro-omental Artery, which is, at its origin, of larger 

 volume than the continuation of the parent trunk, crosses behind the 

 duodenum ; and, placing itself in the texture of the great omentum, it 

 is carried round the greater curvature of the stomach to inosculate with 

 the left gastro-omental artery. It gives off the pyloric and duodenal 

 arteries, besides numerous omental and gastric branches. The pyloric 

 artery is detached from the right gastro-omental artery near its origin, 

 and sometimes it is a branch of the hepatic artery. It supplies the 

 pylorus and the initial dilatation of the duodenum. The duodenal artery 

 is detached from the right gastro-omental artery before that vessel 

 crosses the duodenum ; and, following the lesser curvature of the 

 duodenum, in the narrow serous band that fixes the bowel, it meets and 

 inosculates with the first artery from the left branch of the anterior 

 mesenteric artery. The omental branches of the right gastro-omental 

 are small and unimportant. The gastric branches pass from the 

 concave side of the parent artery ; and, bifurcating at the greater 

 curvature, they are distributed to the right sac of the stomach on both 

 its surfaces, where they anastomose with branches of the pyloric and 

 gastric arteries. 



