DIGESTION. 179 



masticated, dissolved by the stomach and intestines, and rendered 

 fit for absorption by the lacteals and lymphatics, and assimilation 

 by the blood. The parts concerned in digestion are the lips, teeth, 

 and tongue, the salivary glands, the gullet, the stomach, the intes- 

 tines, the liver, the lacteals, and the thoracic duct which connects 

 the digestive process with the direct function of circulation and 

 nutrition. The lips are used by the sheep in gathering its food, 

 very much as they are used by the horse, and to a much greater ex- 

 tent than by the ox. The sheep's lips are thin, and very active in 

 their movement. The upper lip is divided by a groove, or fissure, 

 so that each half can be moved independently of the other. The 

 sheep possesses no muffle or broad space between the nostrils on 

 the upper lip, which in health secretes a liquid which appears in 

 small drops upon its surface, as in the ox. The teeth have been 

 already described. Their office is well known. The tongue serves 

 to convey the food to the teeth, and from the teeth to the gullet, 

 and also the cud from the gullet to the teeth. The salivary glands 

 secrete a fluid which moistens the food during mastication, and 

 which also possesses some of the character of a solvent, or a pre- 

 paratory digestive agent, in being able to convert starch into solu- 

 ble dextrine and sugar, and thus prepare it for digestion by the 

 stomach. The glands are three in number, and are named the 

 parotid, the submaxillary, and the sublingual. The first is situated 

 at the outside of the angle of the lower jaw ; the second is placed 

 on the inside of the lower jaw, near the angle ; and the third is 

 beneath the tongue. Ducts from these glands give out the saliva 

 naturally whenever the membranes of the mouth are excited by 

 the presence of food ; or unduly, as in some diseases which cause 

 an excessive secretion of the fluid. The gullet conveys food or 

 drink from the mouth to the stomach. The pharynx is the upper 

 part of the gullet, by which it is connected with the mouth. It is 

 separated from the larynx, the entrance into the windpipe or air 

 passage, by a cartilaginous lid called the epiglottis, which, when 

 food is swallowed, closes the larynx and allows the food to slide 

 over it. The pharynx, gullet, stomach and intestines, together 

 form what is termed the alimentary canal. The gullet, also called 

 the oesophagus, is a very strong, muscular tube, lined with insensi- 

 ble white membrane. The fibers of the muscles run spirally 

 around the tube, in opposite directions, and thus cross each other. 

 By the contraction of these muscles, gradually extending down- 

 wards, food is carried into the stomach ; while by their contrac- 

 tion in an upward direction, the food is brought back to the 

 mouth to be masticated the second time in the process of rumina- 



