376 



DIGESTIVE SYSTEM OF THE HORSE 



irregularly quadrilateral in form. On its dorsal part is the caudate lobe, which 

 ends in a pointed process directed outward, and assists in forming the cavity for 

 the right kidney. The middle lobe is normally much the smallest. The left lobe 

 is oval in outline and thickest centrally. In old or middle-aged subjects it often 

 exceeds the right one in size. In some cases the atrophy of the right lobe is so 

 extreme that the middle lobe may exceed it in size.^ 



The hepatic duct (Ductus hepaticus) is formed at the ventral part of the portal 

 fissure by the union of right and left chief lobar ducts. It is two or three inches 

 (ca. 5 to 8 cm.) long and about half an inch (ca. 1 to 1.5 cm.) wide. It passes be- 

 tween the two layers of the lesser omentum, and pierces the wall of the duodenum 

 about five or six inches (ca. 12 to 15 cm.) from the pylorus, alongside of the pan- 



Renal impression 



Posterior vena cava 



Portal vein 

 Hepatic artery 

 Hepatic duct 

 (Esophageal notch 



Middle lobe 



Timhilical vein 



Fig 276. — Liver of New-born Foal, Hardened in situ. Visceral Surface. 

 The differences, when compared with the organ in the adult, are very striking. 



creatic duct. The ducts pass oliliquely through the wall of the duodenum for about 

 half an inch (ca. 1 cm.) before opening into the diverticulum duodeni. The 

 arrangement forms an eff(H'tive valve, which prevents regurgitation from the 

 intestine. There is no gall-bladder. 



Structure. — The liver is covered by an outer serous, and an inner fibrous coat. 

 The serous coat covers the gland except at the attachment of the pancreas and at 

 the portal fossa; it is r(^flected from it to form the ligaments and the lesser omentum. 

 The fibrous capsule is in general thin; it sends laminae into the ligaments, and also 



' Flower and Ruge describe the mammalian liver as being primarily divided by the umbilical 

 fissure into two parts, the right and left lobes. Secondary fissures on either side may subdivide 

 each of these primary lobes. On this basis we may recognize in the liver of the horse right lateral, 

 right central, left central, and left lateral lo])es. In the yoiuig foal these four lobes are distinctly 

 recogniza})le. The two central lobes would correspond to the middle lobe of the foregoing de- 

 scription, and the right central lobe would be the equivalent of the quadrate lobe of man. 



