300 



SPLANCHNOLOGY. 



into the pharynx is purely voluntary ; but as soon as it enters 

 the oesophagus, the act of deglutition is entirely involuntary, the 

 food travelling by a vermicular or peristaltic motion, caused by 

 the circular muscular fibres of the oesophagus contracting with 

 successive regularity. 



ABDOMEN. 



The ultimate organs of digestion are contained in the abdomen, 

 or belly, v^hich is a large and somewhat ovoid cavity, bounded 

 superiorly by the muscles of the sublumbar region ; inferiorly and 

 laterally by the abdominal muscles ; and anteriorly by the dia- 

 phragm ; posteriorly it is continuous with the pelvic cavity. It 

 contains chiefly the stomach, intestines, and hidneys, with their 

 acccf^sories. It is lined by the peritonei'^m, a serous membrane^ 

 which is reflected over the viscera. 



For convenience of description, the abdomen 12 divided into 

 nine regions, indicated by imaginary lines drawn as follows : — • 

 Two transverse lines divide it into three primary regions. The 

 first line is drawn from the cartilage of the last false rib on one 

 side, to that of the other ; the second unites the right and left 

 anterior iliac spines. These divide the cavity into the anterior 

 or epigastric, middle or umbilical, and posterior or hypogastric 

 regions. These regions are each subdivided into three secondary, 

 or right, left, and central regions, by two longitudinal lines, 

 extending from either side of the ensiform cartilage to about the 

 ilio-pectineal eminences, completing the division, which may he 

 tabulated as follows : — 



The portion of the alimentary canal contained in the abdomen 

 comprises the stomach and intestines. 



