HEART AND BLOOD. 55 



the flesh, or in both ways, as has already been said in speaking 

 of the passage of the blood through the lungs; whence it ap- 

 pears manifest that in the circuit the blood moves from thence 

 hither, and from hence thither ; from the centre to the extremi- 

 ties, to wit ; and from the extreme parts back again to the centre. 

 Finally, upon grounds of calculation, with the same elements as 

 before, it will be obvious that the quantity can neither be ac- 

 counted for by the ingesta, nor yet be held necessary to nutrition. 



The same thing will also appear in regard to ligatures, and 

 wherefore they are said to draw ; though this is neither from 

 the heat, nor the pain, nor the vacuum they occasion, nor in- 

 deed from any other cause yet thought of; it will also explain 

 the uses and advantages to be derived from ligatures in medi- 

 cine, the principle upon which they either suppress or occasion 

 hemorrhage ; how they induce sloughing and more extensive 

 mortification in extremities ; and how they act in the castration 

 of animals and the removal of warts and fleshy tumours. But 

 it has come to pass, from no one having duly weighed and un- 

 derstood the causes and rationale of these various effects, that 

 though almost all, upon the faith of the old writers, recommend 

 ligatures in the treatment of disease, yet very few comprehend 

 their proper employment, or derive any real assistance from 

 them in effecting cures. 



Ligatures are either very tight or of middling tightness. A 

 ligature I designate as tight or perfect when it is drawn so close 

 about an extremity that no vessel can be felt pulsating beyond 

 it. Such a ligature we use in amputations to control the flow 

 of blood ; and such also are employed in the castration of ani- 

 mals and the removal of tumours. In the latter instances, all 

 afflux of nutriment and heat being prevented by the ligature, 

 we see the testes and large fleshy tumours dwindle, and die, and 

 finally fall off. 



Ligatures of middling tightness I regard as those which com- 

 press a limb firmly all around, but short of pain, and in such 

 a way as still suffers a certain degree of pulsation to be felt in 

 the artery beyond them. Such a ligature is in use in blood- 

 letting, an operation in which the fillet applied above the elbow 

 is not drawn so tight but that the arteries at the wrist may still 

 be felt beating under the finger. 



Now let any one make an experiment upon the arm of a man, 



