146 WILLIAM HARVEY 



which is broken by the great distance at which it is given. 

 Add to this that the impulse of the heart exerted upon the 

 mass of blood, which must needs fill the trunks and branches 

 of the arteries, is diverted, divided, as it were, and diminished 

 at every subdivision, so that the ultimate capillary divisions of 

 the arteries look like veins, and this not merely in constitu- 

 tion, but in function. They have either no perceptible pulse, 

 or they rarely exhibit one, and never except where the heart 

 beats more violently than usual, or at a part where the minute 

 vessel is more dilated or open than elsewhere. It, therefore, 

 happens that at times we are aware of a pulse in the teeth, 

 in inflammatory tumours, and in the fingers ; at another time 

 we feel nothing of the sort. By this single symptom I have 

 ascertained for certain that young persons whose pulses are 

 naturally rapid were labouring under fever; and in like man- 

 ner, on compressing the fingers in youthful and delicate sub- 

 jects during a febrile paroxysm, I have readily perceived 

 the pulse there. On the other hand, when the heart pul- 

 sates more languidly, it is often impossible to feel the pulse 

 not merely in the fingers, but the wrist, and even at the 

 temple, as in persons afflicted with lipothymiae asphyxia, or 

 hysterical symptoms, and in the debilitated and moribund. 



Here surgeons are to be advised that, when the blood 

 escapes with force in the amputation of limbs, in the removal 

 of tumours, and in wounds, it constantly comes from an 

 artery; not always indeed per saltum, because the smaller 

 arteries do not pulsate, especially if a tourniquet has been 

 applied. 



For the same reason the pulmonary artery not only has the 

 structure of an artery, but it does not differ so widely from 

 the veins in the thickness of its walls as does the aorta. The 

 aorta sustains a more powerful shock from the left than the 

 pulmonary artery does from the right ventricle, and the 

 walls of this last vessel are thinner and softer than those of 

 the aorta in the same proportion as the walls of the right 

 ventricle of the heart are weaker and thinner than those of 

 the left ventricle. In like manner the lungs are softer and 

 laxer in structure than the flesh and other constituents of 

 the body, and in a similar way the walls of the branches of 

 the pulmonary artery differ from those of the vessels derived 





