MOVEMENTS OF RESPIRATION. 109 



4. And are always moist internally. 



5. The pulmonary capillaries closely invest each air vesicle. 



6. The lungs are always expanded enough to fill all the 

 space in the chest not occupied by other organs, and 



7. Freely movable, except at the place of entrance of the 

 bronchi and blood tubes. 



8. The smooth, moist pleurae. 



The diaphragm is a thin muscle making a complete parti- 

 tion between the abdominal cavity and the chest cavity. It 

 is convex anteriorly, concave posteriorly ; its ventral border 

 is attached to the inside of the chest wall about opposite the 

 lower end of the breast-bone, thence obliquely along the bor- 

 der of the ribs (as felt in front), and the dorsal attachment is 

 posterior to the ventral attachment. Its general position is 

 shown in the ventral and lateral views, showing the action 

 of the diaphragm and chest wall during inspiration and ex- 

 piration. (See Figs. 40, 42, and 45.) 



APPARATUS ILLUSTRATING THE MOVEMENTS OF 

 RESPIRATION. 



To Show the Action of the Diaphragm and Lungs. 

 MATERIAL. Bell jar with stopper, sheet of rubber large 

 enough to cover the mouth of the jar, toy rubber balloon, 

 cork (rubber preferred), glass tube, strong rubber band (such 

 as boys use for slung-shots), marble. 



PREPARATION. Lay the marble on the center of the sheet 

 of rubber, double the rubber over it, stretching the rubber 

 strongly over the marble, and tie the marble firmly in its 

 place. Stretch the sheet of rubber over the mouth of the jar, 

 with the projection made by the marble on the outside, and 

 fasten with rubber band. Bore a hole in the cork, and fix the 

 glass tube snugly in it, so that the lower end of the tube will 



