104 AVES. 



not all) the Parrots. As a rule, two hepatic ducts are met with (in 

 the Ostrich however there is only one, and a single cystic duct), 

 which open generally -near to (more rarely apart from each other, 

 as in the Pigeons) the extremity of the duodenal loop. Other 

 slight varieties occur in these parts, thus the gall-bladder is very 

 long and intestinoid in the Toucan, and in the Flamingo the short 

 hepatic duct dilates into a bladder-like receptacle after its exit from 

 the liver. 



The Spleen is in general small and exhibits manifold diversities 

 of form, being elongated and cylindrical in the Passeres and in 

 Rhamphas'tos, disc-shaped in the Bustard, rounded and broad in 

 many Palmipedes. It is unusually small in the Cuckoo. In the 

 Struthionidae a small accessory spleen is frequently observed. 



The Pancreas is almost always a gland of considerable size, in- 

 variably lodged within the loop formed by the duodenum and of a 

 white or yellowish white color ; it is small and single in the Heron 

 and Cuckoo, and frequently double, consisting of two lobes united by 

 a very slender isthmoid portion, as in the Gallinae, Pigeons, many 

 Rapacious and Natatorial birds ; it is even tri-lobed, as in the 

 Woodpecker. It has mostly two, though frequently three excretory 

 ducts, as in the Rapaces, Pigeons, Ducks, &c., but more rarely only 

 a single one, as in the Ostrich and Cassowary. 



ORGANS OF CIRCULATION. 



THE Heart of birds is highly muscular, and of very large size in 

 proportion to the bulk of the body. It presents but a few trifling 

 diversities of form, such as being more elongated than usual in the 

 Passeres and Grallae, or broader, as in the Parrots. The whole 

 organ is situated, enveloped by a thin pericardium, in the middle 

 line of the body resting upon the sternum, its apex being directed 

 straight backward, and lodged between the two lobes of the liver. 

 It consists of two auricular and two ventricular chambers, which 

 are not however portioned off, as in the Mammalia, by a well-defined 

 circular groove, nor are the appendices of the auricles so distinct. 

 The cavity of the right ventricle is wider, but its walls are much 

 thinner and shorter than the left, so that the apex of the heart is 

 formed by the left ventricle alone, which is mnch stronger, being 

 furnished with walls three times as thick as those of the right. 

 The usual valves are found in front of the openings of the venae 

 cavae into the right auricle, and between the latter and the right 



