THE LIVER 373 



duct is nearly half an inch (ca. 1 cm.) wide, and is very thin-walled. It is situated 

 in the substance of the gland near its dorsal surface; none of it is free. The acces- 

 sory pancreatic duct (Ductus pancreaticus accessorius [Santorini] ) arises either 

 from the chief duct or its left radicle, and ends on a papilla in the duodenum oppo- 

 site the chief duct. 



Structure. — The pancreas belongs to the class of tubulo-alveolar glands, the 

 alveoli being long, like those of the duodenal glands; in other respects it resembles 

 the serous salivary glands very closely. It has no proper capsule and the lobules 

 are rather loosely united. 



Vessels and Nerves. — The arteries of the pancreas come from the branches of 

 the coeliac and anterior mesenteric arteries. The nerves are derived from the 

 cceliac and mesenteric plexuses of the sympathetic. 



THE LIVER 



The liver (Hepar) is the largest gland in the body. It is situated obliquely 

 on the abdominal surface of the diaphragm. Its highest point is at the level of 

 the right kidney, its lowest on the left side, usually about three or four inches 

 (ca. 8 to 10 cm.) from the abdominal floor, opposite the lower end of the seventh 

 or eighth rib. The greater part of it lies to the right of the median plane. 



It is red-brown in color and is rather friable. Its average weight is about ten 

 to twelve pounds (ca. 5 kg.). When in the body, or if hardened in sitv, it is 

 strongly curved and accurately adapted to the abdominal surface of the diaphragm. 

 When removed in the soft state, it flattens out into a cake-like form quite different 

 from its natural configuration. It presents for descrijition two surfaces and a 

 circumference, which may l^e divided into four borders. 



The parietal surface (Facies diaphragmatica) is strongly convex, and lies 

 against the diaphragm. It faces chiefly upward and forward. It presents, just 

 to the right of the median plane, a sagittal groove for the posterior vena cava (Fossa 

 venae cavse). The vein is partially embedded in the substance of the gland, and 

 receives the hepatic veins. 



The visceral surface (Facies visceralis) faces in general downward and back- 

 ward; it is concave and irregular, being moulded on the organs which lie against it. 

 It presents, a little to the right of the median plane, the portal fissure (Porta 

 hepatis). Through this the portal vein, hepatic artery, and hepatic plexus of 

 nerves enter, and the hepatic duct and lymph vessels leave the liver. The portal 

 or hepatic lymph glands are also found here. The pancreas is attached at and to 

 the right of the fissure, and the gastro-hepatic omentum to the left of it. Above 

 the fissure is a ridge which represents the caudate lobe (Lobus caudatus Spigelii), 

 and is continued to the right by the pointed caudate process (Processus caudatus). 

 Further to the left there is a large depression (Impressio gastrica) for the stomach. 

 To the right of this may be seen a groove passing to the right and dorsally ; this is 

 the duodenal impression (Impressio duodenalis). Ventral to these is a large de- 

 pression for the great colon (Impressio colica). Dorsal to this is a smaller depres- 

 sion for the blind end of the base of the caecum.^ Coils of the small intestine may 

 also lie on this surface, and the apex of the spleen may reach to it when the stomach 

 is empty. 



The dorsal border (Margo obtusus) is thick for the most part. It presents 

 from right to left: (1) a depression for the right kidney (Impressio renalis); (2) a 

 notch, which is the dorsal end of the fossa venae cavse; (3) a deep notch (Impressio 



' These impressions are not evident on the soft organ. In hardened material they are 

 clearly mapped out, although of course variable in size, in conformity with the degree of fullness 

 of the various hollow viscera. The caecal impression may not be evident if, as often happens in 

 old horses, the right lobe of the liver is much atrophied. 



