CHAP, vi.] THE CAT'S ALIMENTARY SYSTEM. 185 



blood-vessels (the aorta and vena cava) are interposed between it 

 and the bodies of the vertebra). 



It is a solid organ, thick dorsally, and thinning out below; of a 

 reddish-brown colour, smooth and convex towards the diaphragm 

 but concave and uneven on its opposite surface. It is divisible into 

 certain parts, or lobes, which are defined and marked off, partly by 

 grooves and notches in its substance, partly by ligaments and blood- 

 vessels connected with it. 



The liver is divided into two unequal lateral halves by a mem- 

 branous ligament (the broad or falciform ligament), which passes to 

 it from the adjacent surface of the diaphragm, and which consists of 

 two folds ^ of peritoneum, as will be hereafter explained. This 

 ligament is attached to the liver in a line running from its dorsal 

 margin to its ventral border ; and the part on the right side of it is 

 the larger. 



When the posterior surface of the liver is in view, a deep notch (M) 

 and groove may be observed opposite to, and corresponding with, 

 the attachment of the broad ligament. This groove is called the 

 longitudinal fissure, and it lodges a fibrous cord called the round 

 ligament. The anterior part of this cord (which passes upwards to 

 the liver from the navel) is the remnant of a structure temporarily 

 developed^in the very young condition the umbilical vein while 

 the posterior part of the cord (which joins the vena cava) is the 

 remnant of another primitive vessel the ductus venosus. 



On this account the ventral part of the groove is called the 

 umbilical fissure (u), while its posterior part is named the fissure of 

 the ductus venosus. This fissure then divides the liver into two 

 unequal lobes on its hinder surface, and each of these is again 

 subdivided by other fissures. Thus a small, prominent, undivided, 

 somewhat pyramidal lobe (called Spigelian) is placed almost medially 

 at the dorsal border of the liver (s), its apex extending outwards 

 on the hinder surface of the left lateral lobe (II). It is bounded on 

 the right by a short deep groove called the fissure of the vena cam, 

 because it is traversed by that vessel. The Spigelian lobe is bounded 

 ventrally by the transverse or portal fissure which runs, almost at 

 right angles, into the longitudinal fissure. It is into this transverse 

 fissure that the portal vein, the hepatic artery and the great nerves 

 enter, and it is from it that the main bile ducts proceed to convey 

 away the biliary secretions. 



The portal fissure runs to the right, beyond the limits of the 

 Spigelian lobe. That part of the substance of the liver which is 

 situate on the dorsal side of this outer part of the portal fissure, is 

 called the caudate lobe (c). It is a moderate-sized, ridge-like lobe, 

 which proceeds from the base of the Spigelian lobe to and along the 

 hinder surface of the right lateral lobe (rl 1 ), and is more or less 

 limited behind by the vena cava. 



The right lateral lobe is small and separated from a much larger 

 lobe, the right central (r/ 2 ) which lies next it but nearer the middle 

 line by a deep fissure called the right lateral fissure (rf). The 



