LEPUS 



143 



part from the transverse septum. The scrotal sacs contain a 

 portion of coelomic cavity, lined with ccelomic epithelium or 

 peritoneum termed tunica vaginalis. 



The alimentary canal is supported by a dorsal mesentery. 

 The latter, in the region of the stomach, is called the great 

 omentum, and is pulled ventrally and backwards so as to 

 enclose a sac (the omental bursa) which communicates with the 

 general peritoneal cavity on the right side of the stomach by 

 the foramen of Winslow. In the rabbit the great omentum is 

 small, but in other forms it is extensive and laps over the 

 ventral side of several coils of the intestine. Fat is often 

 found deposited in the great omentum, and especially in the 



Pig- 



The pleural cavities each surround a lung, which is 

 suspended in them by a mesentery. The coelomic epithelium 

 of a pleural cavity is called the pleura, and it is divided into 

 visceral (or splanchnic) and parietal (or somatic) parts. The 

 parietal pleura lines the outer wall of the pleural cavity, the 

 anterior face of the diaphragm, and in the middle line comes 

 into contact with its fellow from the opposite side to form the 

 mediastinal septum. The visceral pleura continues from the 

 parietal and covers over the lung. When the ribs are lifted, 

 the pleural cavities increase their volume, and since the space 

 between the visceral and parietal pleura is a closed one, 

 expansion of the parietal pleura is necessarily accompanied by 

 expansion of the visceral pleura and of the lung which it covers. 

 If the thoracic box were punctured and air could get into the 

 pleural cavities, the visceral pleura and the lungs would fail 

 to expand. The pericardium lies ventral and median to the 

 pleural cavities. 



Alimentary System. — The original edge to the mouth is 

 represented by the gums, in which the teeth are set. Outside 

 these, fleshy lips are developed. The roof of the mouth is 

 formed by the false palate, due to the extension inwards of a 

 shelf from the maxilla and palatine bone on each side. In this 

 region it is called the hard palate, and it is continued posteriorly 

 a short distance by the soft palate, in which there is no bone. 

 The false palate encloses the nasal passage between itself and 



