84 MOTION OF THE 



and the testicles, the two orders of vessels are so much alike 

 that it is impossible to distinguish between them with the eye. 

 Now this is for the following very sufficient reasons : for the 

 more remote vessels are from the heart, with so much the less 

 force are they impinged upon by the stroke of the heart, 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 constitution but 

 in function ; for they have either no perceptible pulse, or they 

 rarely exhibit one, and never save where the heart beats more 

 violently than wont, or at a part where the minute vessel is more 

 dilated or open than elsewhere. Hence it 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. Hence, too, by this single symptom I have ascertained 

 for certain that young persons, whose pulses are naturally 

 rapid, were labouring under fever; in like manner, on com- 

 pressing the fingers in youthful and delicate subjects during 

 a febrile paroxysm, I have readily perceived the pulse there. 

 On the other hand, when the heart pulsates more languidly, 

 it is often impossible to feel the pulse not merely in the fingers, 

 but at the wrist, and even at the temple; this is the case in 

 persons afflicted with Iipothymia3 and asphyxia, and hysterical 

 symptoms, as also in persons of very weak constitution and in 

 the moribund. 



And 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 per saltum, however, because the smaller arteries 

 do not pulsate, especially if a tourniquet has been applied. 



And then the reason is the same wherefore the pulmonary 

 artery has not only the structure of an artery, but wherefore it 

 does not differ so widely in the thickness of its tunics from the 

 veins as the aorta : the aorta sustains a more powerful shock from 

 the left ventricle than the pulmonary artery does from the right ; 

 and the tunics of this last vessel are thinner and softer than 

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



