HEART AND BLOOD. 2o 



filled and distended by the blood forced into them by the con- 

 traction of the ventricles ; the arteries, therefore, are distended, 

 because they are filled like sacs or bladders, and are not filled 

 because they expand like bellows. It is in virtue of one and 

 the same cause, therefore, that all the arteries of the body 

 pulsate, viz. the contraction of the left ventricle; in the same 

 way as the pulmonary artery pulsates by the contraction of the 

 right ventricle. 



Finally, that the pulses of the arteries are due to the impulses 

 of the blood from the left ventricle, may be illustrated by blow- 

 ing into a glove, when the whole of the fingers will be found 

 to become distended at one and the same time, and in their 

 tension to bear some resemblance to the pulse. For in the 

 ratio of the tension is the pulse of the heart, fuller, stronger, 

 more frequent as that acts more vigorously, still preserving the 

 rhythm and volume, and order of the heart's contractions. Nor 

 is it to be expected that because of the motion of the blood, the 

 time at which the contraction of the heart takes place, and that 

 at which the pulse in an artery (especially a distant one,) is 

 felt, shall be otherwise than simultaneous: it is here the same 

 as in blowing up a glove or bladder; for in a plenum, (as in a 

 drum, a long piece of timber, &c.) the stroke and the motion 

 occur at both extremities at the same time. Aristotle, 1 too, 

 has said, " the blood of all animals palpitates within their veins, 

 (meaning the arteries,) and by the pulse is sent everywhere 

 simultaneously/' And further, 2 " thus do all the veins pulsate 

 together and by successive strokes, because they all depend upon 

 the heart ; and, as it is always in motion, so are they likewise 

 always moving together, but by successive movements." It is 

 well to observe with Galen, in this place, that the old philoso- 

 phers called the arteries veins. 



I happened upon one occasion to have a particular case under 

 my care, which plainly satisfied me of this truth: A certain 

 person was affected with a large pulsating tumour on the right 

 side of the neck, called an aneurism, just at that part where 

 the artery descends into the axilla, produced by an erosion of 

 the artery itself, and daily increasing in size; this tumour was 

 visibly distended as it received the charge of blood brought to 



1 De Animal, iii, cap. 9. 2 De Respirat. cap. 20. 



