心血运动论
他证明血液沿着一条无尽的回路循环——而心脏，就是驱动它的泵。
一千四百年来，医生们都相信身体在不停地造出新血、再把它烧掉用尽。一道仔细的算术，证明了这绝无可能。
核心思想
在哈维之前，医学遵循古希腊医师盖伦：血在肝脏里造出，流向全身，像燃料一样被用尽——一股单向的潮水，造出来，又被耗掉。哈维却证明，血是沿着一条回路行进的。心脏是一台泵；它把同一份血经动脉推出去，又经静脉收回来，一圈又一圈，永不停息。
他一锤定音的一着，不是什么新仪器——而是算术。他算出心脏每跳一次推出多少血，再乘以仅仅半小时里的心跳次数，得到的血量，远远大于全身所有的血。身体绝无可能在这么短的时间里造出这么多。所以，那必是同一份血，在循环。
它是怎么来的
哈维曾在意大利伟大的解剖学重镇帕多瓦求学，师从法布里修斯——后者注意到静脉里有一些小小的瓣膜，却始终没弄明白它们是做什么的。回到伦敦、成为两代国王御医的哈维，花了多年解剖活体动物，看着一颗颗心脏跳动、变慢、停下，感觉着脉搏与那一次次挤压合着拍子。
他看到那些瓣膜全都朝着一个方向——朝向心脏。他按压自己手臂上的静脉，看着它拒绝从错误的方向重新充盈。然后，他算了那道账。1628 年，他把它写进一本薄薄的拉丁文小书《心血运动论》。它被攻击了许多年；有些同行认为他「脑子坏了」。但他活着看到它被接受。
它为什么重要
一旦知道血在循环，下游的一切便成为可能：测量血压，理解休克与心力衰竭，输血，心脏直视手术，人工心肺机。但更深的革命，在于方法。哈维不是靠引用更古老的权威取胜的；他靠的是测量，让数字推翻了十五个世纪的成见。现代医学，正是这样学会了思考。
可以这样想象
想象一座城市的供水。盖伦设想的是一眼泉水，被全城喝干——水在源头造出、在龙头用尽，永远需要更多。哈维看到的是真相：那是一套闭合的管路，心脏是它的泵，同一股水循环着流过每一户人家，再流回来。那些单向的瓣膜，就是防止水倒流的止回阀。
它在知识谱系中的位置
哈维这本书（1628）站在近代科学革命的开端，比牛顿的《自然哲学的数学原理》（1687，亦在本馆）早了一代人——后者在物理学里做了同样的一步：以测量与机制，取代承袭来的权威。在医学里，它开启了一条贯穿巴斯德与弗莱明（其青霉素亦在本馆）的脉络——治病这件事，被缓缓地变成一门科学。哈维自己那条回路的最后一块——毛细血管——则由马尔比基在 1661 年用新生的显微镜找到。
献词 · 致查理一世
The heart of animals is the foundation of their life, the sovereign of everything within them, the sun of their microcosm, that upon which all growth depends, from which all power proceeds.
第八章 · 如环之运动
I began to think whether there might not be a motion, as it were, in a circle. Now this I afterwards found to be true; and I finally saw that the blood, forced by the action of the left ventricle into the arteries, was distributed to the body at large, and its several parts, in the same manner as it is sent through the lungs, impelled by the right ventricle into the pulmonary artery, and that it then passed through the veins and along the vena cava, and so round to the left ventricle in the manner already indicated.
第九章 · 数量的论证
Whence it is to be inferred, that if at one stroke the heart in man, the ox or the sheep, ejects but a single drachm of blood, and there are one thousand strokes in half an hour, in this interval there will have been ten pounds five ounces expelled: were there with each stroke two drachms expelled, the quantity would of course amount to twenty pounds and ten ounces; were there half an ounce, the quantity would come to forty-one pounds and eight ounces; and were there one ounce it would be as much as eighty-three pounds and four ounces; the whole of which, in the course of one half hour, would have been transfused from the veins to the arteries.
第十四章 · 结论
It is absolutely necessary to conclude that the blood in the animal body is impelled in a circle, and is in a state of ceaseless motion; that this is the act or function which the heart performs by means of its pulse; and that it is the sole and only end of the motion and contraction of the heart.