456 ELEMENTARY ANATOMY. [LESS. 



In possessing a gall-bladder man resembles the great 

 majority of Vertebrates, yet it may be absent in the highest 

 and the lowest classes. Thus in Fishes it is wanting in 

 a few species, as e.g. in the Lamprey and Pristis. In 

 Birds it is wanting in most Parrots and Cuckoos, as well 

 as in the Pigeons. Amongst Mammals it is absent in the 

 Cetacea, the Sloths, the Elephant, the Camel, the Hyrax, 

 Horse, Tapir, and Rhinoceros. The presence or absence of 



FIG. 387. LIVER OF THE DOLPHIN (Delphinus) seen from beneath, its front 

 margin being turned upwards. 



(After Flower) 



lie, united left lateral and left ventral lobes ; rcl, united right central and right 

 lateral lobes ; i>c, vena cava. 



this organ, however, cannot be of very great importance, as 

 it is absent or present sometimes in the same species ; and 

 even two gall-bladders have been found coexisting in an indi- 

 vidual Giraffe. The gall-bladder may be placed exceptionally 

 on the left side, as in the Thylacine. It may be, as it were, 

 inverted, perforating part of the liver and appearing on the 

 upper surface, as in Lemuroids, e.g. Galago. 



Where a gall-bladder is wanting, the bile-duct may as in 

 the Elephant be dilated at its entrance into the duodenum. 



The colour of the liver may differ strikingly from that which 

 we find in man. This is especially the case in Fishes, where 

 it may be bright red, as in Holoccntrum Orientate ; or yellow, 

 as in Atherina presbyter ; or green, as in the Lamprey. 



The liver may also be much less dense in consistency than 

 in man as in Fishes generally ; and in aquatic Mammals, 

 such as the Cetacea, Seals, and Otter, it is said to be softer 

 than in other kinds of the same class, 



