These five fissures taken collectively, namely, the longitudinal fissure and fissure for the ductus venosus on the left, the fissures for the gall-bladder and vena cava on the right, with the transverse fissure passing between them, are represented by Meckel as resembling the letter 11, whereof the transverse bar is placed nearer to the posterior than to the anterior extremity. Viewing them in this way the two anterior branches are, the longitudinal fissure on the left and the fossa for the gall-bladder on the right ; and the two posterior are, the fissure for the ductus venosus on the left, and the fissure for the vena cava on the right.
The existence of these five fissures upon the under surface of the liver causes its division into as many portions, which are named lobes, viz. the right, the left, the lobus quadratus, the lobus Spigelii, and the lobus caudatus.
The right lobe, (fig. 32, 1, fib. 33, 16,) (lobus major) is the largest division of the liver, and forms the whole of the bulky right extremity of the organ. It is convex upon its upper surface and irregularly con cave below ; at its right extremity and be.. bind it is thick and rounded, and thin and sharp in front. It is separated from the left lobe on its convex surface by the broad liga ment; beneath by the longitudinal fissure and fissure for the ductus venosus, and in front by the notch on the free margin of the liver. The transverse fissure and the fissures for the vena cava and gall-bladder are situated on the under surface of this lobe and serve to limit the boundaries of the three minor lobes; the lobus quadratus, Spigelii, and caudatus. Upon this surface it is marked by three depressions, one in front, of large size, for the right ex tremity of the transverse colon,and two behind, one for the right supra-renal capsule and ano ther for the right kidney.
The left lobe (fig. 32, 2, fig. 33, 17,) (lobus minor) is four or six times smaller than the right; flattened in form, and thinned to wards its circumference into a sharp margin. It is divided from the right lobe by the broad ligament above, by the notch in the anterior margin of the liver in front, and by the longi tudinal fissure and fissure for the ductus ve nosus below. Superiorly it is convex and in relation with the diaphragm, to which it is con nected by the left lateral ligament, and infe riorly it is concave, and presents a broad and shallow depression which rests upon the ante rior surface of the stomach. By its extremity
it sometimes touches the spleen, and by its posterior border corresponds with the termina tion of the (esophagus and with the right pneu mogastric nerve.
The lobos griadratos (fig. 33, 18,) (ante rior portal eminence) is a quadrilateral and slightly elevated division situated upon the under surface of the right lobe near to the middle line of the liver. It is bounded ante riorly by the free margin of the organ, poste riorly by the transverse fissure, to the left by the longitudinal fissure, and on the right by the fossa for the gall-bladder.
The lobos Spigelii (fig. 33, 20,) (posterior portal eminence) is a prominent conical lobe, smaller than the preceding, and situated near the posterior border of the liver, behind the two layers of the lesser omentum. Its base is triangular, and bounded in front by the trans verse fissure ; on the left side by the fissure fur the ductus venosus, and on the right by the fissure for the vena eava and lobus caudatuq, which last connects it with the under surface of the right lobe. By its anterior border it is in relation with the portal vein, by its left border with the fibrous cord of the ductus venosus, and by the right with the vena.cava. Its pos terior extremity is received into the angle of communication between the fibrous cord of the ductus venosus and the vena cava.
The lobos modulus (fig. 33, 21,) is a tail like appendage to the lobus Spigelit. It is ex tremely diversified in form, being sometimes well developed and a distinct lobe; at other times a mere vestige recognisible only to the eye of the experienced anatomist. Sometimes it is a slight ridge, merging into the surface of the liver on either side, and at other times is marked by a fissure on one side or even on both. Ordinarily it is an angular projection two or three inches in length, commencing by a narrow isthmus from the lobus passing obliquely outwards and forwards by the side of the gall-bladder, and subsiding at its extremity into the surface of the right lobe. The depression on the under surface of the right lobe, in front of this process, is for the re ception of the curve of the ascending colon, and the posterior depressions for the right supra renal capsule and right kidney.