338 



HEALTH AND DISEASE 



Hiatus Aorticus gives passage to the posterior aorta, the vena azygos, and 

 the thoracic duct. It is situated immediately beneath the spine, and is 

 formed by the separation of the two muscuhxr pillars. 



Action. — When the diaphragm contracts it passes in a backward direc- 

 tion, and in so doing enlarges the chest so that the lungs may be filled with 

 It is, therefore, a muscle of inspiration. 



air 



THE ABDOMINAL CAVITY, OR CAVITY OF 

 THE BELLY 



Placed behind the chest, from which it is separated by the diaphragm, 

 the abdominal cavity passes backward and becomes continuous with the 

 pelvis. It is the largest cavity of the body, bounded above by the ioms or 

 lumbar division of the spine, below and at the sides by muscles, tendons, 

 and elastic tissue, already described. Contained within it are the stomach 

 and bowels, the liver, pancreas, spleen, kidneys, and numerous vessels, 

 nerves, and lymphatic glands. In the female it also contains the ovaries 

 and the horns of the uterus. 



For convenience of description of the position of parts within it the 

 abdomen is arbitrarily divided into nine portions, of which three are 

 situated in front, three in the middle, and three behind. This division 

 is effected by cutting the body across by two imaginary vertical planes, one 

 passing through the lower extremity of the fifteenth rib, the other trans- 

 versely through the external angle of the haunch-bone. The three divisions 

 thus made are subdivided by two longitudinal planes which fall through 

 the centre of Poupart's ligament on the right and left side respectively, and 

 cut each of the three primary divisions into a central and two lateral 

 portions. As a result of this we get the nine parts described and figured 

 below. 



