THE ALIMENTARY CANAL. 275 



carried away by rupture of the glandular sac, or by absorption 

 into the neighbouring lymphatics. 



The liver has been termed a reticular gland, because its ducts 

 form a network at their origin. 



Digestive System. 



The digestive organs comprise the alimentary canal and its 

 accessories, by which the alimentary matter is received and sub- 

 jected to specific actions, which adapt it for purposes of nutri- 

 tion. Digestion therefore embraces the collective operations and 

 changes which the food undergoes in the alimentary canal. 



The functional processes of digestion are — Prehension, the 

 taking up of food, which is performed in the horse by the lips ; 

 Mastication, chewing, grinding ; and, simultaneously with this, 

 Insalivation, or mixing the ingesta with the fluid secretion of 

 the salivary glands ; Deglutition, or swallowing the prepared food 

 by means of the tongue, pharynx, and oesophagus ; Chymification, 

 or conversion of food in the stomach into a pultaceous chyme, 

 by maceration and the action of the gastric juice ; Ghylijication, 

 or conversion of the chyme into chyle, a change which takes 

 place in the duodenum, presumably by the agency of the biliary 

 and pancreatic secretions ; Absorption of the nutrient material 

 into the circulation; and finally. Defecation or excretion, the 

 expulsion of residual inert matter. 



the alimentary CANAL. 



The alimentary canal is a musculo-membrauous tube extend- 

 ing from the lips to the anus ; its walls are composed of muscular 

 tissue, for the most part of the non-striated kind, and lined 

 throughout by mucous membrane. It consists of a continuous 

 series of tubes and cavities, the chief of which are the Mouth, 

 Pharynx, Oesophagus, Stomach, and the Intestines. It may be 

 divided into three portions — the preparatory, or ingestive, em- 

 bracing the mouth, pharynx, and oesophagus, in which the food 

 is prepared ; the essential, or digestive, including the stomach 

 and most of the intestines, where the food passes through various 

 changes, and is deprived of its nutritive portions ; and the 

 egestive, or expulsive portion, by which the residue is expelled 

 from the system. Each division is provided with accessories, the 



