INFLUENCE OF THE RESPIRATION ON THE HEART. 



113 



vessels of the lungs become filled with blood, and thus partly occupy 

 the lung-space. Much less blood is driven out of the left heart, so that 

 the pulse may disappear. Hence, the heart is distended with blood, 

 and the lungs are congested, while the aortic system contains a small 

 amount of blood i.e., the systemic circulation is comparatively empty, 

 while the heart and the pulmonary vessels are engorged with blood. 



In normal respiration, the air in the lungs during inspiration is 

 under slight pressure, while during expiration the pressure is higher, 

 so that these conditions favour the circulation ; inspiration favours the 

 supply of blood (and lymph) through the vena? cavae, and favours the 

 occurrence of diastole. In operations where the axillary or jugular 

 vein is cut, air may be sucked into the circulation during inspiration, 

 and cause death. Expiration favours the flow of blood in the aorta 

 and its branches, and aids the systolic emptying of the heart. The 

 arrangement of the valves of the heart causes the blood to move in a 

 definite direction through it. 



a 



II 



Fte .37. 



Apparatus for demonstrating the action of inspiration, II, and expiration, I, on 

 the heart and on the blood-stream P, p, lungs ; H, h, heart ; L, /, closed 

 glottis ; M, m, manometers ; E, e, ingoing blood-stream, vein ; A, a, outgoing 

 blood-stream, artery ; D, diaphragm during expiration ; d, during inspiration. 



8 



