342 



MANUAL OF ZOOLOGY 



SECT. XII 



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

 On the floor of the buccal cavity in the Lizard and in the 

 Rabbit is a mobile muscular prominence, the tongue, re- 

 presented in the Dog-fish by a much less prominent 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 Dog-fish 

 (Fig. 202), and in the Lizard the 

 anus opens into a chamber, the 

 cloaca, which also receives the 

 ducts of the urinary and repro- 

 ductive organs. In the Rabbit 

 a cloaca is absent, and the anus 

 is separate from the urinogenital 

 opening. The mucous mem- 

 brane of the enteric canal con- 

 tains numerous glands, the secre- 

 tions of which play an important 

 part in digestion ; the most im- 

 portant of these secretions is 

 the gastric juice secreted by the 

 glands of the stomach. In ad- 

 dition, special large digestive 

 glands are present producing 



secretions, which also have 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 into the blood-vessels. In the 

 Rabbit these special large digestive glands are the salivary 

 glands, the liver and the pancreas : in the Dog-fish and 

 Lizard the salivary glands are absent, though in the latter 



zc 



FIG. 201. Longitudinal section 

 of a tooth, semi-diagrammatic. 

 PH, pulp cavity ; PH', open- 

 ing of same ; ZB, dentine ; 

 ZC, cement ; ZS, enamel. 

 (From Wiedersheim's Verte- 

 brata.) 



