In mammals Sir William Flower pointed out that a generalized type of liver exists, from which that of any mammal may be derived by suppression or fusion of lobes. The accompanying diagram of Flower (fig. 4) represents an ideal mammalian liver. It will be seen that the umbilical fissure (u) divides the organ into right and left halves, as in the lower vertebrates, but that the ventral part of each half is divided into a central and lateral lobe. Passing from right to left there are therefore: right lateral (rl), right central (rc), left central (lc), and left lateral (ll) lobes. The gall-bladder (g), when it is present, is always situated on the caudal surface or in the substance of the right central lobe. The Spigelian (s) and caudate lobes (c) belong to the right half of the liver, the latter being usually a leaf-shaped lobe attached by its stalk to the Spigelian, and having its blade flattened between the right lateral lobe and the right kidney. The vena cava (vc) is always found to the right of the Spigelian lobe and dorsal to the stalk of the caudate. In tracing the lobulation of man's liver back to this generalized type, it is evident at once that his quadrate lobe does not correspond to any one generalized lobe, but is merely that part of the right central which lies between the gall bladder and the umbilical fissure. From a careful study of human variations (see A. Thomson, _Journ. Anat. and Phys_. vol. 33, p. 546) compared with an Anthropoid liver, such as that of the gorilla, depicted by W. H. L. Duckworth (_Morphology and Anthropology_, Cambridge, 1904, p. 98), it is fairly clear that the human liver is formed, not by a suppression of any of the lobes of the generalized type, but by a fusion of those lobes and obliteration of certain fissures. This fusion is, probably correctly, attributed by Keith to the effect of pressure following the assumption of the erect position (Keith, _Proc. Anat. Soc. of Gt. Britain, Journ. Anat. and Phys_. vol. 33, p. xii.). The accompanying diagram (fig. 5) shows an abnormal human liver in the Anatomical Department of St Thomas's Hospital which reproduces the generalized type. In its lobulation it is singularly like, in many details, that of the baboon (_Papio maimon_) figured by G. Ruge (_Morph. Jahrb_., Bd. 35, p. 197); see F. G. Parsons, _Proc. Anat. Soc_., Feb. 1904, _Journ. Anat. and Phys_. vol. 33, p. xxiii. Georg Ruge "Die äusseren Formverhältnisse der Leber bei den Primaten," (_Morph. Jahrb_., Bd. 29 and 35) gives a critical study of the primate liver, and among other things suggests the recognition of the Spigelian and caudate lobes as parts of a single lobe, for which he proposes the name of lobus venae cavae. This doubtless would be an advantage morphologically, though for human descriptive a natomy the present nomenclature is not likely to be altered.