MOTION OF THE HEART AND BLOOD 



the lungs and ventricles of the heart, from the veins, 

 it must be accomplished in a circuit, since the 

 amount involved is much more than can be fur- 

 nished from the food consumed, or than is needed for 

 the nourishment of the parts. 



It is further to be observed that this truth is often 

 demonstrated in blood-letting. Though you prop- 

 erly bandage the arm, and puncture the vein 

 correctly with a lancet, if a fainting state of mind 

 comes on through fear or any other cause, and the 

 heart beats more sluggishly, blood will escape only 

 a drop at a time, especially if the ligature be made 

 a little more tight. The reason is that the feeble 

 beat in the compressed artery, with the weaker 

 propelling power, cannot force the blood under 

 the bandage.^ For the same reason the feeble and 

 languid heart cannot force the normal amount 

 of blood through the lungs or transfer it from the 

 veins to the arteries. In the same way and for the 

 same reasons, it happens that the menses of women 

 and all types of hemorrhages are checked. If the 

 opposite occurs, the patient recovering his mind, 

 and losing his fear, you will see the arteries at once 

 beat more powerfully, even in the bound-off part, 

 so the blood gushes from the opening and flows 

 steadily. 



^ A characteristic example of Harvey's clear reasoning. It is 

 easily inferred that the obvious factor in maintaining blood pressure 

 is the pumping action of the heart. 



[95] 



