324 



ZOOLOGY 



SECT. 



The stomach (Fig. 967, M, Fig. 968, Si) is a cylindrical organ 

 but little wider than the oesophagus, and with thick muscular walls. 

 At the point where the small intestine joins the large intestine 

 or rectum, the latter is produced into a short ccecum (Fig. 969, Co;). 



The liver (Ir) is divided into right 

 and left lobes, and a gall-bladder 

 (Fig. 967, G, B. ; Fig. 968, gJ) ; Fig. 

 969, gM) lies at the lower margin 

 of the right lobe. The pancreas [pn) 

 is situated in the loop between 

 the stomach and first part of the 

 small intestine or duodenum (du). 

 The stomach is attached to the 

 body-wall by a fold of peritoneum, 

 the viesogaster, the small intestine 

 by a fold termed the mesentery, 

 the rectum by a meso-rectiim. From 

 the dorsal surface of the liver to 

 the stomacb extends a thin fold, 

 the gasiro-hepatic omentura ; and 

 this is continued backwards as the 

 duodeno-Jiepatic omentum, connect- 

 ing the liver with the first portion 

 of the small intestine. 



Vascular System. — The heart 

 is enclosed, like that of the Frog, 

 in a thin transparent membrane, 

 the pericardium. It consists of a 

 sinus venosus, right and left auricles, 

 and an incompletely divided ven- 

 tricle. The sinus venosus (Fig. 968, 

 s. v.), into which the large veins 

 open, is thin walled, and has a 

 smooth inner surface. From it a 

 sinu-auricular aperture, guarded by 

 a two-lipped valve, leads to the 

 right auricle. The auricles have 

 their inner surfaces raised up into 

 a network of muscular ridges, the 

 musculi pcctifiati. Both auricles 

 open into the cavity of the ven- 

 tricle, the aperture of communication, or auriculo-ventricular aper- 

 ture, being divided into two by the auricular septum, and guarded 

 by the auriculo-ventricular valve, consisting of two semilunar flaps. 

 The ventricle (Fig. 968, v. ; Fig. 969, vent.) has very thick spongy 

 walls and a small cavity, divided into two parts by an incomplete 

 muscular partition. From the part of the ventricular cavity to 



10. OOV.— lacerta agllis. General 

 view of the viscera in tlieir natural 

 relations. Bl. urinary bladder ; Ci. post- 

 caval vein ; ED, rectum ; GB. gall 

 bladder ; H. heart ; Lg. Lg'. the lungs 

 M, stomach ; MB, small int.'stine ; Oe. 

 oesophagus ; Vn. pancreas ; Tr. trachea. 

 (From Wiedersheim's Comparative 

 Anatomy.) 



