1881.] MR. W. A. FORBES ON THE KOALA. 185 



sented, drawn to scale of ? the natural size, in the accompanyina; 

 figures (1 and 2, pp. 180, 187). All four principal lobes are well 

 developed ; but those on the right are far larger than those on the 

 left, the left central being considerably the smallest of these. Tlie 

 umbilical fissure is distinct, extending about halfway across the liver. 

 The right central lobe, which is broad transversely, and forms the 

 largest lobe, is divided very deeply by the large cystic fissure, which 

 extends on the thoracic surface nearly as far back as the umbilical 

 one, and allows the very large and elongated gall-bladder to appear 

 above. Both right and left lateral fissures are also (in this specimen) 

 well developed. The right lateral lobe is large and somewhat oval 

 in shape, but pointed below. The caudate is not present as a free 

 structure, but it is represented by a somewhat squared, diagonally 

 ridged elevation, lying to the right of the inferior cava, and broadly 

 attached to the substance of the right lateral lobe. The lower border 

 of this elevation is slightly excavated to receive the correspondin" 

 kidney. The Si)igelian is represented by a smaller thickening, ending 

 in a jjointed and free apex, and lying to the left of the vena cava ; it 

 is united over this by liepatic tissue to the caudate. This liver is 

 further remarkable for the great tendency it has to subdivision, 

 numerous fissures, of varying sizes and depths, being develo[)ed along 

 the margin of the chief lobes. Their position and relative size will 

 be better understood from the figures than from any verbal descrip- 

 tion. They are more conspicuous on the visceral than the thoracic 

 surface. The right half of the right central lobe has one such notch 

 on its right external border ; the other half 3, on the right internal 

 border ; the left central has 4, the left lateral 3, whilst the right 

 lateral is still more cut up by about 10. Finally, the caudate has 3 

 of these supplementary fissures. 



The gall-bladder is remarkably long, projecting far beyond the 

 anterior margin of the liver, and, as already described, appearing 

 superficially. It is 2| inches long from its apex to the commence- 

 ment ot its duct opposite the anterior margin of the left central lobe. 

 The free part is connected by a peritoneal investment to the sides of 

 the cystic fissure. 



In a second liver of Phascolarctos examined (which, however, 

 having been extracted from a spirit-preserved animal, an adult $ , is 

 not so well preserved as might be wished) the same general features 

 obtain. The left lateral fissure, however, is less distinct, as is the 

 caudate : and the left central lobe is smaller proportionally to the left 

 lateral. The Spigelian wants the pointed apex ; and the development 

 of secondary fissures seems to attain an even greater extent'. 



^ In Phalangista vidpina the riglit central lobe is also, as in the Koala, the 

 biggest, and very deeply divided by a cystic fissure. The gall-bladder, however, 

 does not nearly reach the margin of the liver ; the left lateral lobe is uiiieh bigger 

 thai! the right lateral, which is as large as the left central ; the caudate is quite 

 free and narrow. All tlie lobes are remarkably distinct ; and their margins are 

 quite simple, with no trace of any such fissiu-es as obtain in the Koala. 



The liver of discus maculatus is formed on a similar principle, though tlie 

 right central lobe is not bigger than the left lateral, and the gall-bladder reaches 

 to the li^er-margin. All the lobes are simple. The caudate and Spigelian, 



