THE ALIMENTARY CANAL. 275 



-carried away by rapture 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 ; Ghymifica- 

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

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

 Chylification, 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-membranous 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, CEsophagus, Stomach, and the Intestines. It may be 

 divided into three portions — the preparatory, or ingestive, 

 embracing 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 por- 

 tions; and the egestive, or expulsive portion, by which the 

 residue is expelled from the system. Each division is provided 



