THE HORSE. 



113 



contact with the pancreas, and then be- 

 tween the folds of the gastro-hepatic omen- 

 tum, and it reaches the porta on the left 

 side of the portal vein. After giving off 

 pancreatic and duodenal branches, it di- 

 vides into two, a right and a left one. The 

 right, the largest and somewhat the longest, 

 penetrates into the right lobe, giving off 

 collateral branches, first to the middle and 

 then to the right lobe itself. The left is the 

 smallest division, and is distributed to the 

 lobe corresponding to it in position, and also 

 to the middle one. 



The liver is exceptional for having, be- 

 sides an artery, another afferent vessel — a 

 vein, known as the portal vein, formed by 

 the splenic, which also receives the gasti'ic 

 and mesenteries, meeting each other at the 

 same spot near the posterior part of the 

 pancreas. From its origin, the portal vein 

 takes an oblique course from left to right 

 through the pancreas, and being surrounded 

 by nerves, it reaches the porta of the liver, 

 and here divides into three principal 

 branches, one for each lobe. 



At the porta we also see the biliary duct 

 coming out, formed by the union of several 

 branches, corresponding in number to the 

 ramification of the blood-vessels. This 

 duct passes through the gastro-hepatic 

 omentum, meeting the pancreatic duct at 

 almost a right angle, and with it opening 

 into the duodenum about five or six inches 

 from the pylorus. 



Having thus far considered the main 

 vessels, we may examine further the inter- 

 nal structure of the liver. At the porta 

 the branches of the vessels and ducts are 

 associated together, and surrounded by cel- 

 lular tissue, which sheaths grooves or canals, 

 cut in various directions in the substance of 

 the organ. These are the portal canals, 

 and the cellular tissue in question is Glis- 

 son's capsule. 



The vessels and ducts ramifying on the 

 sheath acquire the name of vaginal branches, 

 and, as they are traced between the lobules, 

 they are termed interlobular. Here the un- 

 assisted eye ceases to take cognizance of 

 their further relation ; but, with careful dis- 



15 



section, and a common pocket lens, they 

 may be traced to the lobules, which they 

 enter; and the blood of the hepatic artery 

 and portal vein is emptied into a common 

 set of vessels, the hepatic vein. The rela- 

 tion of these vessels in the lobules may be 

 seen on the surface in a good injected speci- 

 men of liver, where the hepatic veins have 

 been injected one color, and the other ves- 

 sels differently. By this means the centre 

 of the lobule is colored with the injection 

 thrown into the hepatic veins, and the cir- 

 cumference with that of tl^e portal vein. 



The hepatic veins issuing from the lo- 

 bules cross the structure of the liver in sep- 

 arate grooves, formed by the coalescence of 

 the hepatic particles, so that their base is in 

 contact with the veins, and hence the name 

 of the latter is that of the sub-lobular he- 

 patic veins. These empty into the posterior 

 cava by several orifices, as well as by two 

 larger ones, guarded by semi-lunar valves, 

 situated just at the foramen dextrum of the 

 diaphragm. 



In addition to the blood-vessels and ducts 

 of the liver, it is supplied with nerves from 

 the solar plexus, which ramify with the ves- 

 sels. 



The lymphatics of the liver are abundant, 

 and aiTanged, like in other organs, as a su- 

 perficial and deep set, which inosculate 

 freely in the substance of the organ, and, 

 uniting to form several branches, they issue 

 from the porta of the liver, passing through 

 some lymphatic glands situated round the 

 fissure, and from this they advance to the 

 receptaculum chyli. 



PANCREAS. 



The pancreas is a compound vesicular or 

 racemose gland, being much of the same 

 nature as the salivary glands. 



The pancreas occupies the interval be- 

 tween the layers of the transverse meso- 

 colon, along the upper surface of the trans- 

 verse colon. 



Its attachments are merely cellular, with 

 the exception of the pancreatic duct, which 

 attaches it pretty closely to the duodenum. 



The pancreas is spoken of as having a 



