BREATHING HABITS 



145 



called cartilage lies between the ends of the ribs and 

 the backbone and between each false rib and the one 

 above it. Between the ribs are the intercostal 

 muscles. We can also observe that the ribs slope 

 slightly downward from the backbone to the point 

 where they are attached in 

 front, and that the dia- 

 phragm, which is a very 

 elastic muscle, is somewhat 

 the shape of an open um- 

 brella. Its top or convex 

 side is toward the chest, 

 reaching upward to about 



the fifth rib, and its under a b 



or concave side is toward showing positions of the dia- 



phragm, sternum, and walls of 



the abdomen. the abdomen in inspiration and 



~ . , . expiration (Zuppke). 



Curiously enough, it is 



the sloping position of these ribs and the umbrella 

 shape of the elastic diaphragm that enable our bodies 

 to be easily supplied with air. The position of the 

 ribs and diaphragm, as seen in the cut, is as they 

 appear just after the air is breathed out. When we 

 breathe in, the intercostal muscles draw the front of 

 the ribs upward and the diaphragm goes downward, 

 becoming less convex. This pushes the lower ribs 

 outward and crowds the abdominal organs down, both 

 movements naturally enlarging the chest cavity, thus 

 enabling the elastic lungs to expand, so that air rushes 

 in to fill the space. 



