Organs of Digestion. ] 5 



muscles, assist materially in keeping the food 

 effectually between the molar teeth. Through 

 their substance pass ducts or tubes which convey 

 necessary lubricating and solvent fluids to the 

 mouth. 



The molars or grinders are twenty-four in 

 number, six of which are situated above and be- 

 low upon each side of the jaws in the back part 

 of the mouth. In order to observe them par- 

 ticularly the mouth must be held wide open. 



They are large and rough upon the wearing 

 surface, and form most perfect agents in crush- 

 ing and grinding, or masticating the hard grain 

 and kernels which this animal requires as natural 

 food. 



The pharynx is a musculo-membranous bag or 

 pouch which opens at the back of the mouth, 

 and grasps the bolus of food as it is presented 

 by the tongue. Arrived at this point, its appro- 

 priate muscles successively contract and force 

 onwards the pellet to the further end opening 

 into the gullet. The food is now beyond the 

 control of the will, and cannot be returned by 

 any effort of a natural character. 



The oesophagus or gullet is also composed partly 

 of muscles and membrane. It forms an elastic 

 tube reaching from the pharynx above to the 

 stomach below, and occupies a position in the 

 neck upon the left side of the lower portion. A 

 knowledge of this fact enables us to trace the 

 passage of substances throughout its visible 



