That this may the more clearly appear to everyone, I have here to cite certain experiments, from which it seems obvious that the blood enters a limb by the arteries1, and returns from it by the veins3; that the arteries are the vessels4 carrying the blood from the heart, and the veins the returning channels of the blood to the heart; that in the limbs and extreme parts of the body the blood passes either immediately by anastomosis from the arteries into the veins, or mediately6 by the porosities of the flesh, or in both ways, as has already been said in speaking of the passage of the blood through the lungs whence it appears manifest that in the circuit the blood moves from that place to this place, and from that point to this one; from the centre to the extremities7, to wit; and from the extreme parts back to the centre. Finally, upon grounds of calculation, with the same elements as before, it will be obvious that the quantity can neither be accounted for by the ingeata, 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 indeed from any other cause yet thought of; it will also explain the uses and advantages to be derived9 from ligatures in medicine, the principle upon which they either suppress or occasion hemorrhage; how they induce sloughing10 and more extensive mortification11 in extremities; and how they act in the castration of animals and the removal of warts12 and fleshy tumours13. But it has come to pass, from no one having duly weighed and understood the cause 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 derive8 any real assistance from them in effecting cures.
Ligatures are either very tight or of medium tightness. A ligature I designate as tight or perfect when it so constricts15 an extremity16 that no vessel5 can be felt pulsating17 beyond it. Such a ligature we use in amputations to control the flow of blood; and such also are employed in the castration of animals and the ablation 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 dwindle18, die, and finally fall off.
Ligatures of medium tightness I regard as those which compress a limb firmly all round, but short of pain, and in such a way as still suffers a certain degree of pulsation19 to be felt in the artery20 beyond them. Such a ligature is in use in blood-letting, an operation in which the fillet applied21 above the elbow is not drawn22 so tight but that the arteries at the wrist may still be felt beating under the finger.
Now let anyone make an experiment upon the arm of a man, either using such a fillet as is employed in blood-letting, or grasping the limb lightly with his hand, the best subject for it being one who is lean, and who has large veins, and the best time after exercise, when the body is warm, the pulse is full, and the blood carried in larger quantity to the extremities, for all then is more conspicuous23; under such circumstances let a ligature be thrown about the extremity, and drawn as tightly as can be borne, it will first be perceived that beyond the ligature, neither in the wrist nor anywhere else, do the arteries pulsate24, at the same time that immediately above the ligature the artery begins to rise higher at each diastole, to throb25 mere26 violently, and to swell27 in its vicinity with a kind of tide, as if it strove to break through and overcome the obstacle to its current; the artery here, in short, appears as if it were preternaturally full. The hand under such circumstances retains its natural colour and appearance; in the course of time it begins to fall somewhat in temperature, indeed, but nothing is drawn into it.
After the bandage has been kept on for some short time in this way, let it be slackened a little, brought to that state or term of medium tightness which is used in bleeding, and it will be seen that the whole hand and arm will instantly become deeply coloured and distended28, and the veins show themselves tumid and knotted; after ten or twelve pulses of the artery, the hand will be perceived excessively distended, injected, gorged29 with blood, drawn, as it is said, by this medium ligature, without pain, or heat, or any horror of a vacuum, or any other cause yet indicated.
If the finger be applied over the artery as it is pulsating by the edge of the fillet, at the moment of slackening it, the blood will be felt to glide30 through, as it were, underneath31 the finger; and he, too, upon whose arm the experiment is made, when the ligature is slackened, is distinctly conscious of a sensation of warmth, and of something, viz., a stream of blood suddenly making its way along the course of the vessels and diffusing32 itself through the hand, which at the same time begins to feel hot, and becomes distended.
As we had noted33, in connexion with the tight ligature, that the artery above the bandage was distended and pulsated34, not below it, so, in the case of the moderately tight bandage, on the contrary, do we find that the veins below, never above, the fillet, swell, and become dilated35, whilst the arteries shrink; and such is the degree of distension36 of the veins here, that it is only very strong pressure that will force the blood beyond the fillet, and cause any of the veins in the upper part of the arm to rise.
From these facts it is easy for every careful observer to learn that the blood enters an extremity by the arteries; for when they are effectually compressed nothing is drawn to the member; the hand preserves its colour; nothing flows into it, neither is it distended; but when the pressure is diminished, as it is with the bleeding fillet, it is manifest that the blood is instantly thrown in with force, for then the hand begins to swell; which is as much as to say, that when the arteries pulsate the blood is flowing through them, as it is when the moderately tight ligature is applied; but where they do not pulsate, as, when a tight ligature is used, they cease from transmitting anything, they are only distended above the part where the ligature is applied. The veins again being compressed, nothing can flow through them; the certain indication of which is, that below the ligature they are much more tumid than above it, and than they usually appear when there is no bandage upon the arm.
It therefore plainly appears that the ligature prevents the return of the blood through the veins to the parts above it, and maintains those beneath it in a state of permanent distension. But the arteries, in spite of its pressure, and under the force and impulse of the heart, send on the blood from the internal parts of the body to the parts beyond the ligature. And herein consists the difference between the tight and the medium ligature, that the former not only prevents the passage of the blood in the veins, but in the arteries also; the latter, however, whilst it does not prevent the force of the pulse from extending beyond it, and so propelling the blood to the extremities of the body, compresses the veins, and greatly or altogether impedes37 the return of the blood through them.
Seeing, therefore, that the moderately tight ligature renders the veins turgid and distended, and the whole hand full of blood, I ask, whence is this? Does the blood accumulate below the ligature coming through the veins, or through the arteries, or passing by certain hidden porosities? Through the veins it cannot come; still less can it come through invisible channels; it must needs, then, arrive by the arteries, in conformity38 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 unless the ligature be removed; when this is done suddenly all the veins collapse39, and disgorge themselves of their contents into the superior parts, the hand at the same time resumes its natural pale colour, the tumefaction and the stagnating40 blood having 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 swollen41 and livid but cold, when the fillet is undone42 is aware of something cold making its way upwards43 along with 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 blood-letting: fainting frequently supervenes even in robust44 subjects, and mostly at the moment of undoing45 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 arteries 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 porosities in the flesh and solid parts generally that are permeable to the blood It is farther an indication that the veins have frequent communications with one another, because they all become turgid together, whilst under the medium ligature applied above the elbow; and if any single small vein2 be pricked46 with a lancet, they all speedily shrink, and disburthening themselves into this they subside47 almost simultaneously48.
These considerations will enable anyone to understand the nature of the attraction that is exerted by ligatures, and perchance of fluxes49 generally; how, for example, when the veins are compressed by a bandage of medium tightness applied above the elbow, the blood cannot escape, whilst it still continues to be driven in, 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 a vacuum draw, indeed; but in such wise only that parts are filled, not preternaturally distended or gorged, and not so suddenly and violently overwhelmed with the charge of blood forced in upon them, that the flesh is lacerated and the vessels ruptured50. Nothing of the kind as an effect of heat, or pain, or the vacuum force, is either credible51 or demonstrable.
Besides, the ligature is competent to occasion the afflux in question without either pain, or heat, or a vacuum. Were pain in any way the cause, how should it happen that, with the arm bound above the elbow, the hand and fingers should swell being the bandage, and their veins become distended? The pressure of the bandage certainly prevents the blood from getting there by the veins. And then, wherefore is there neither swelling52 nor repletion53 of the veins, nor any sign or symptom of attraction or afflux, above the ligature? But this is the obvious cause of the preternatural attraction and swelling below the bandage, and in the hand and fingers, that the blood is entering abundantly, and with force, but cannot pass out again.
Now is not this the cause of all tumefaction, as indeed Avicenna has it, and of all oppressive redundancy in parts, that the access to them is open, but the egress54 from them is. closed? Whence it comes that they are gorged and tumefied. And may not the same thing happen in local inflammations, where, so long as the swelling is on the increase, and has not reached its extreme term, a full pulse is felt in the part, especially when the disease is of the more acute kind, and the swelling usually takes place most rapidly. But these are matters for after discussion. Or does this, which occurred in my own case, happen from the same cause? Thrown from a carriage upon one occasion, I struck my forehead a blow upon the place where a twig55 of the artery advances from the temple, and immediately, within the time in which twenty beats could have been made I felt a tumour14 the size of an egg developed, without either heat or any great pain: the near vicinity of the artery had caused the blood to be effused into the bruised56 part with unusual force and velocity57.
And now, too, we understand why in phlebotomy we apply our ligature above the part that is punctured58, not below it; did the flow come from above, not from below, the constriction59 in this case would not only be of no service, but would prove a positive hindrance60; it would have to be applied below the orifice, in order to have the flow more free, did the blood descend61 by the veins from superior to inferior parts; but as it is elsewhere forced through the extreme arteries into the extreme veins, and the return in these last is opposed by the ligature, so do they fill and swell, and being thus filled and distended, they are made capable of projecting their charge with force, and to a distance, when any one of them is suddenly punctured; but the ligature being slackened, and the returning channels thus left open, the blood forthwith no longer escapes, save by drops; and, as all the world knows, if in performing phlebotomy the bandage be either slackened too much or the limb be bound too tightly, the blood escapes without force, because in the one case the returning channels are not adequately obstructed62; in other the channels of influx63, the arteries, are impeded64.
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1
arteries
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| n.动脉( artery的名词复数 )；干线，要道 | |
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vein
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| n.血管，静脉；叶脉，纹理；情绪；vt.使成脉络 | |
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veins
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| n.纹理；矿脉( vein的名词复数 )；静脉；叶脉；纹理 | |
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vessels
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| n.血管( vessel的名词复数 )；船；容器；（具有特殊品质或接受特殊品质的）人 | |
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5
vessel
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| n.船舶；容器，器皿；管，导管，血管 | |
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6
mediately
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| 在中间，间接 | |
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extremities
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| n.端点( extremity的名词复数 )；尽头；手和足；极窘迫的境地 | |
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8
derive
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| v.取得；导出；引申；来自；源自；出自 | |
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9
derived
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| vi.起源；由来；衍生；导出v.得到( derive的过去式和过去分词 )；（从…中）得到获得；源于；（从…中）提取 | |
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10
sloughing
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| v.使蜕下或脱落( slough的现在分词 )；舍弃；除掉；摒弃 | |
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11
mortification
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| n.耻辱，屈辱 | |
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12
warts
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| n.疣( wart的名词复数 )；肉赘；树瘤；缺点 | |
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13
tumours
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| 肿瘤( tumour的名词复数 ) | |
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tumour
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| n.(tumor)(肿)瘤，肿块 | |
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15
constricts
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| 压缩，压紧，使收缩( constrict的名词复数 ) | |
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extremity
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| n.末端，尽头；尽力；终极；极度 | |
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17
pulsating
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| adj.搏动的，脉冲的v.有节奏地舒张及收缩( pulsate的现在分词 )；跳动；脉动；受（激情）震动 | |
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18
dwindle
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| v.逐渐变小（或减少） | |
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pulsation
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| n.脉搏，悸动，脉动；搏动性 | |
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artery
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| n.干线，要道；动脉 | |
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applied
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| adj.应用的；v.应用，适用 | |
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drawn
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| v.拖，拉，拔出；adj.憔悴的，紧张的 | |
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conspicuous
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| adj.明眼的，惹人注目的；炫耀的，摆阔气的 | |
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pulsate
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| v.有规律的跳动 | |
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throb
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| v.震颤，颤动；(急速强烈地)跳动，搏动 | |
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26
mere
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| adj.纯粹的；仅仅，只不过 | |
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swell
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| vi.膨胀，肿胀；增长，增强 | |
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distended
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| v.（使）膨胀，肿胀( distend的过去式和过去分词 ) | |
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29
gorged
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| v.（用食物把自己）塞饱，填饱( gorge的过去式和过去分词 )；作呕 | |
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30
glide
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| n./v.溜，滑行；(时间)消逝 | |
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underneath
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| adj.在...下面，在...底下；adv.在下面 | |
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32
diffusing
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| （使光）模糊，漫射，漫散( diffuse的现在分词 )； （使）扩散； （使）弥漫； （使）传播 | |
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noted
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| adj.著名的，知名的 | |
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pulsated
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| v.有节奏地舒张及收缩( pulsate的过去式和过去分词 )；跳动；脉动；受（激情）震动 | |
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35
dilated
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| adj.加宽的，扩大的v.（使某物）扩大，膨胀，张大( dilate的过去式和过去分词 ) | |
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distension
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| n.扩张，膨胀(distention) | |
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impedes
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| 阻碍，妨碍，阻止( impede的第三人称单数 ) | |
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conformity
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| n.一致，遵从，顺从 | |
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39
collapse
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| vi.累倒；昏倒；倒塌；塌陷 | |
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40
stagnating
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| v.停滞，不流动，不发展( stagnate的现在分词 ) | |
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41
swollen
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| adj.肿大的，水涨的；v.使变大，肿胀 | |
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42
undone
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| a.未做完的，未完成的 | |
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43
upwards
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| adv.向上，在更高处...以上 | |
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44
robust
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| adj.强壮的，强健的，粗野的，需要体力的，浓的 | |
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45
undoing
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| n.毁灭的原因，祸根；破坏，毁灭 | |
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46
pricked
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| 刺，扎，戳( prick的过去式和过去分词 )； 刺伤； 刺痛； 使剧痛 | |
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47
subside
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| vi.平静，平息；下沉，塌陷，沉降 | |
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48
simultaneously
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| adv.同时发生地，同时进行地 | |
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49
fluxes
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| 连续的改变( flux的名词复数 )； 不稳定的状态； 不停的变化； 通量 | |
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50
ruptured
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| v.（使）破裂( rupture的过去式和过去分词 )；（使体内组织等）断裂；使（友好关系）破裂；使绝交 | |
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51
credible
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| adj.可信任的，可靠的 | |
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52
swelling
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| n.肿胀 | |
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53
repletion
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| n.充满，吃饱 | |
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54
egress
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| n.出去；出口 | |
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55
twig
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| n.小树枝，嫩枝；v.理解 | |
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56
bruised
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| [医]青肿的，瘀紫的 | |
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57
velocity
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| n.速度，速率 | |
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58
punctured
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| v.在（某物）上穿孔( puncture的过去式和过去分词 )；刺穿（某物）；削弱（某人的傲气、信心等）；泄某人的气 | |
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59
constriction
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| 压缩； 紧压的感觉； 束紧； 压缩物 | |
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60
hindrance
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| n.妨碍，障碍 | |
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61
descend
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| vt./vi.传下来，下来，下降 | |
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62
obstructed
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| 阻塞( obstruct的过去式和过去分词 )； 堵塞； 阻碍； 阻止 | |
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63
influx
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| n.流入，注入 | |
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impeded
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| 阻碍，妨碍，阻止( impede的过去式和过去分词 ) | |
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