In the first place, then, when the chest of a living animal is laid open and the capsule that immediately surrounds the heart is slit2 up or removed, the organ is seen now to move, now to be at rest; there is a time when it moves, and a time when it is motionless.
These things are more obvious in the colder animals, such as toads3, frogs, serpents, small fishes, crabs4, shrimps5, snails6, and shell-fish. They also become more distinct in warm-blooded animals, such as the dog and hog7, if they be attentively8 noted9 when the heart begins to flag, to move more slowly, and, as it were, to die: the movements then become slower and rarer, the pauses longer, by which it is made much more easy to perceive and unravel10 what the motions really are, and how they are performed. In the pause, as in death, the heart is soft, flaccid, exhausted11, lying, as it were, at rest.
In the motion, and interval12 in which this is accomplished13, three principal circumstances are to be noted:
1. That the heart is erected15, and rises upwards16 to a point, so that at this time it strikes against the breast and the pulse is felt externally.
2. That it is everywhere contracted, but more especially towards the sides so that it looks narrower, relatively17 longer, more drawn18 together. The heart of an eel19 taken out of the body of the animal and placed upon the table or the hand, shows these particulars; but the same things are manifest in the hearts of all small fishes and of those colder animals where the organ is more conical or elongated20.
3. The heart being grasped in the hand, is felt to become harder during its action. Now this hardness proceeds from tension, precisely21 as when the forearm is grasped, its tendons are perceived to become tense and resilient when the fingers are moved.
4. It may further be observed in fishes, and the colder blooded animals, such as frogs, serpents, etc., that the heart, when it moves, becomes of a paler color, when quiescent22 of a deeper blood-red color.
From these particulars it appears evident to me that the motion of the heart consists in a certain universal tension — both contraction23 in the line of its fibres, and constriction24 in every sense. It becomes erect14, hard, and of diminished size during its action; the motion is plainly of the same nature as that of the muscles when they contract in the line of their sinews and fibres; for the muscles, when in action, acquire vigor25 and tenseness, and from soft become hard, prominent, and thickened: and in the same manner the heart.
We are therefore authorized26 to conclude that the heart, at the moment of its action, is at once constricted27 on all sides, rendered thicker in its parietes and smaller in its ventricles, and so made apt to project or expel its charge of blood. This, indeed, is made sufficiently28 manifest by the preceding fourth observation in which we have seen that the heart, by squeezing out the blood that it contains, becomes paler, and then when it sinks into repose29 and the ventricle is filled anew with blood, that the deeper crimson30 colour returns. But no one need remain in doubt of the fact, for if the ventricle be pierced the blood will be seen to be forcibly projected outwards31 upon each motion or pulsation32 when the heart is tense.
These things, therefore, happen together or at the same instant: the tension of the heart, the pulse of its apex33, which is felt externally by its striking against the chest, the thickening of its parietes, and the forcible expulsion of the blood it contains by the constriction of its ventricles.
Hence the very opposite of the opinions commonly received appears to be true; inasmuch as it is generally believed that when the heart strikes the breast and the pulse is felt without, the heart is dilated34 in its ventricles and is filled with blood; but the contrary of this is the fact, and the heart, when it contracts (and the impulse of the apex is conveyed through the chest wall), is emptied. Whence the motion which is generally regarded as the diastole of the heart, is in truth its systole. And in like manner the intrinsic motion of the heart is not the diastole but the systole; neither is it in the diastole that the heart grows firm and tense, but in the systole, for then only, when tense, is it moved and made vigorous.
Neither is it by any means to be allowed that the heart only moves in the lines of its straight fibres, although the great Vesalius giving this notion countenance36, quotes a bundle of osiers bound in a pyramidal heap in illustration; meaning, that as the apex is approached to the base, so are the sides made to bulge37 out in the fashion of arches, the cavities to dilate35, the ventricles to acquire the form of a cupping-glass and so to suck in the blood. But the true effect of every one of its fibres is to constringe the heart at the same time they render it tense; and this rather with the effect of thickening and amplifying38 the walls and substance of the organ than enlarging its ventricles. And, again, as the fibres run from the apex to the base, and draw the apex towards the base, they do not tend to make the walls of the heart bulge out in circles, but rather the contrary; inasmuch as every fibre that is circularly disposed, tends to become straight when it contracts; and is distended39 laterally40 and thickened, as in the case of muscular fibres in general, when they contract, that is, when they are shortened longitudinally, as we see them in the bellies41 of the muscles of the body at large. To all this let it be added, that not only are the ventricles contracted in virtue42 of the direction and condensation43 of their walls, but farther, that those fibres, or bands, styled nerves by Aristotle, which are so conspicuous44 in the ventricles of the larger animals, and contain all the straight fibres (the parietes of the heart containing only circular ones), when they contract simultaneously45 by an admirable adjustment all the internal surfaces are drawn together as if with cords, and so is the charge of blood expelled with force.
Neither is it true, as vulgarly believed, that the heart by any dilatation or motion of its own, has the power of drawing the blood into the ventricles; for when it acts and becomes tense, the blood is expelled; when it relaxes and sinks together it receives the blood in the manner and wise which will by-and-by be explained.
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1 dissection | |
n.分析;解剖 | |
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2 slit | |
n.狭长的切口;裂缝;vt.切开,撕裂 | |
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3 toads | |
n.蟾蜍,癞蛤蟆( toad的名词复数 ) | |
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4 crabs | |
n.蟹( crab的名词复数 );阴虱寄生病;蟹肉v.捕蟹( crab的第三人称单数 ) | |
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5 shrimps | |
n.虾,小虾( shrimp的名词复数 );矮小的人 | |
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6 snails | |
n.蜗牛;迟钝的人;蜗牛( snail的名词复数 ) | |
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7 hog | |
n.猪;馋嘴贪吃的人;vt.把…占为己有,独占 | |
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8 attentively | |
adv.聚精会神地;周到地;谛;凝神 | |
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9 noted | |
adj.著名的,知名的 | |
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10 unravel | |
v.弄清楚(秘密);拆开,解开,松开 | |
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11 exhausted | |
adj.极其疲惫的,精疲力尽的 | |
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12 interval | |
n.间隔,间距;幕间休息,中场休息 | |
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13 accomplished | |
adj.有才艺的;有造诣的;达到了的 | |
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14 erect | |
n./v.树立,建立,使竖立;adj.直立的,垂直的 | |
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15 ERECTED | |
adj. 直立的,竖立的,笔直的 vt. 使 ... 直立,建立 | |
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16 upwards | |
adv.向上,在更高处...以上 | |
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17 relatively | |
adv.比较...地,相对地 | |
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18 drawn | |
v.拖,拉,拔出;adj.憔悴的,紧张的 | |
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19 eel | |
n.鳗鲡 | |
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20 elongated | |
v.延长,加长( elongate的过去式和过去分词 ) | |
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21 precisely | |
adv.恰好,正好,精确地,细致地 | |
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22 quiescent | |
adj.静止的,不活动的,寂静的 | |
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23 contraction | |
n.缩略词,缩写式,害病 | |
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24 constriction | |
压缩; 紧压的感觉; 束紧; 压缩物 | |
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25 vigor | |
n.活力,精力,元气 | |
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26 authorized | |
a.委任的,许可的 | |
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27 constricted | |
adj.抑制的,约束的 | |
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28 sufficiently | |
adv.足够地,充分地 | |
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29 repose | |
v.(使)休息;n.安息 | |
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30 crimson | |
n./adj.深(绯)红色(的);vi.脸变绯红色 | |
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31 outwards | |
adj.外面的,公开的,向外的;adv.向外;n.外形 | |
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32 pulsation | |
n.脉搏,悸动,脉动;搏动性 | |
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33 apex | |
n.顶点,最高点 | |
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34 dilated | |
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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35 dilate | |
vt.使膨胀,使扩大 | |
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36 countenance | |
n.脸色,面容;面部表情;vt.支持,赞同 | |
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37 bulge | |
n.突出,膨胀,激增;vt.突出,膨胀 | |
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38 amplifying | |
放大,扩大( amplify的现在分词 ); 增强; 详述 | |
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39 distended | |
v.(使)膨胀,肿胀( distend的过去式和过去分词 ) | |
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40 laterally | |
ad.横向地;侧面地;旁边地 | |
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41 bellies | |
n.肚子( belly的名词复数 );腹部;(物体的)圆形或凸起部份;腹部…形的 | |
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42 virtue | |
n.德行,美德;贞操;优点;功效,效力 | |
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43 condensation | |
n.压缩,浓缩;凝结的水珠 | |
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44 conspicuous | |
adj.明眼的,惹人注目的;炫耀的,摆阔气的 | |
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45 simultaneously | |
adv.同时发生地,同时进行地 | |
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