344 MANUAL OF ZOOLOGY SECT, xn 



The anterior part of the cavity into which the mouth 

 leads is the buccal cavity ', the posterior part is the pharynx. 

 On the floor of the buccal cavity is, in the lizard and in the 

 rabbit, a mobile muscular prominence, the tongue, repre- 

 sented in the dogfish by a much less prominent and little 

 mobile process. 



From this a wide tube leads backwards to open into a 

 spacious chamber, the stomach. From the stomach the 

 intestine, a more or less coiled tube, leads eventually to the 

 anal aperture. In the dogfish and in the lizard the anus 

 opens into a chamber, the cloaca, which also receives the 

 ducts of the urinary and reproductive organs. In the rabbit 

 a cloaca is absent, and the anus is separate from the urino- 

 genital opening. The mucous membrane of the enteric 

 canal contains numerous glands, the secretions of which play 

 an important part in digestion ; the most important of these 

 secretions is the gastric juice secreted by the glands of the 

 stomach. In addition, special large digestive glands are 

 present producing secretions, also having the function of 

 acting on the various components of the food in such a way 

 as to facilitate the passage of the useful ingredients from the 

 cavity of the alimentary canal to the blood-vessels. In the 

 rabbit these special large digestive glands are the salivary 

 glands, the liver, and the pancreas ; in the dogfish and 

 lizard the salivary glands are absent, though in the latter 

 there are numerous small glands, the buccal glands, in the 

 wall of the buccal cavity. The secretion of the salivary 

 glands, the saliva, enters the cavity of the mouth through 

 the ducts of the glands. It contains a ferment, ptyalin, 

 which has the property of converting starch into sugar. 

 The liver is in all three a relatively large organ, fixed by 

 folds of peritoneum to the dorsal wall of the abdominal 

 cavity and divided by fissures into a number of lobes. Its 



