264 THE ANATOMY OF YERTEBKATED ANIMALS. 



by a narrow neck with the above-mentioned muscular stomach 

 or gizzard (gigerium). 



Some Ophidia have a caecum at the junction of the small 

 intestine with the large ; and two such CEeca, which sometimes 

 attain a large size, are very generally developed in Aves. In 

 this class also, the small intestine, not unfrequently, presents 

 a CEecal appendage, the remains of the vitelline duct. The 

 duodenum of Birds constantly makes a loop, within v?hich the 

 pancreas lies, as in Mammalia. 



The liver in the Sauropsida almost always possesses a 

 gall-bladder, which is usually attached to the under surface 

 of the right lobe, but in the Ophidia is removed to some 

 distance from it. 



A peculiar glandular sac, the Sursa Fabricii, opens into 

 the anterior and dorsal region of the cloaca in birds. 



Three forms of heart are found in the Sauropsida. The 

 first is that observed in the Ghelonia, Lacertilia, and Ophid- 

 ia ,• the second, that in the Crocodilia ; and the third, that 

 in Aves. 



1. In the Chelonia, Lacertilia, and Ophidia, there are 

 two auricles. Generally, a distinct sinus venosus, with con- 

 tractile V7alls, and communicating by a valvular aperture with 

 the auricle, receives the blood from the venoe cavm, and pours 

 it into the right auricle. The pulmonary veins usually open 

 by a common trunk into the left auricle. 



The interauricular septum is rarely (in some Chelonia) 

 perforated. Its ventricular edge spreads out on each side into 

 a broad membranous valve, the edge of which, during the 

 systole, flaps against a ridge, or fold, developed, on one, or 

 both sides, from the margin of the auriculo-ventricular aper- 

 ture, and constituting a rudiment of a second valve. The 

 ventricle contains only one cavity, but that cavity is im- 

 perfectly divided into two or three chambers, by septa devel- 

 oped from its muscular walls. 



In the Turtle (Fig. 92), a partly muscular, and partly carti- 

 laginous, septum extends from the front wall of the ventricular 

 cavity toward its right-hand end. It imperfectly divides the 

 common ventricular cavity into a right small, and a left large 

 moiety. The latter of these receives the blood from the auri- 

 cles. In consequence of the elongated form of the ventricular 

 cavity, and the projection into it of the large auriculo-ven- 

 tricular valves, especially of that of the right side, this left and 

 larger moiety of the common ventricle is virtually divided into 



