58 MOTION OF THE 



arteries, then, in conformity with all that has been already said. 

 That it cannot flow in by the veins appears plainly enough from 

 the fact that the blood cannot be forced towards the heart un- 

 less the ligature be removed ; when on a sudden all the veins 

 collapse, and disgorge themselves of their contents into the 

 superior parts, the hand at the same time resuming its natural 

 pale colour, the tumefaction and the stagnating blood have 

 disappeared. 



Moreover, he whose arm or wrist has thus been bound for 

 some little time with the medium bandage, so that it has not 

 only got swollen and livid but cold, when the fillet is undone 

 is aware of something cold making its way upwards along \vith 

 the returning blood, and reaching the elbow or the axilla. 

 And I have myself been inclined to think that this cold blood 

 rising upwards to the heart was the cause of the fainting that 

 often occurs after bloodletting : fainting frequently supervenes 

 even in robust subjects, and mostly at the moment of undoing 

 the fillet, as the vulgar say, from the turning of the blood. 



Farther, when we see the veins below the ligature instantly 

 swell up and become gorged, when from extreme tightness it is 

 somewhat relaxed, the arteries meantime continuing unaffected, 

 this is an obvious indication that the blood passes from the ar- 

 teries into the veins, and not from the veins into the arteries, and 

 that there is either an anastomosis of the two orders of vessels, 

 or pores in the flesh and solid parts generally that are permeable 

 to the blood. It is farther an indication that the veins have fre- 

 quent communications with one another, because they all become 

 turgid together, whilst under the medium ligature applied above 

 the elbow ; and if any single small vein be pricked with a lancet, 

 they all speedily shrink, and disburthening themselves into this 

 they subside almost simultaneously. 



These considerations will enable any one to understand the 

 nature of the attraction that is exerted by ligatures, and per- 

 chance of fluxes generally; how, for example, the veins when 

 compressed by a bandage of medium tightness applied above 

 the elbow, the blood cannot escape, whilst it still continues 

 to be driven in, to wit, by the forcing power of the heart, by 

 which the parts are of necessity filled, gorged with blood. And 

 how should it be otherwise ? Heat and pain and the vis vacui 

 draw, indeed; but in such wise only that parts are filled, not pre- 



