HARVEY'S WORK 51 



it becomes of a deeper blood-red colour. It thus seems 

 evident that during action the heart . . . becomes 

 erect, hard, and of diminished size. The movement is 

 plainly of the same nature as that of the muscles when 

 they contract." 



During contraction the heart diminishes in breadth and 

 increases in length. Owing to this increase in length, the 

 apex of the heart strikes the chest wall during contraction 

 of the organ on the left side. It can be easily felt and seen 

 to beat under the fifth rib. A new point has here been 

 raised. It had naturally been believed that it was during 

 expansion that the heart struck the chest wall. Harvey 

 showed that it was during contraction that this event took 

 place. The point raised by Harvey had been hinted 

 at, however, by Leonardo, who had made experiments 

 which, rightly interpreted, would have led to the same 

 conclusion. 



3. The contraction of the heart and the striking of 

 the apex of the heart against the chest wall are also 

 simultaneous, or almost simultaneous, with another 

 phenomenon, namely, the expansion of the arteries, 

 which may be felt as the pulse. The observation dis- 

 posed of the view, that had been held by many, that 

 the pulse was a result of the active expansion of the 

 arteries or even of the substance of the blood itself, co- 

 incident with the expansion of the heart. Those who held 

 this view thought that the expansion of the heart and the 

 expansion of the arteries was part of one and the same 

 event, an expansion extending right through the vascular 

 system. Harvey's new observation made it highly 

 probable that the contraction of the heart was the cause 

 of the expansion of the artery, and therefore the cause 

 of the pulse. 



4. This third conclusion is confirmed by the character 

 of the bleeding from an artery that has been cut. The 



