Book I chapter 15

Since, then, we have talked sufficient nonsense — not willingly, but because we were forced, as the proverb says, “to behave madly among madmen”— let us return again to the subject of urinary secretion¹. Here let us forget the absurdities² of Asclepiades, and, in company with those who are persuaded that the urine does pass through the kidneys, let us consider what is the character of this function. For, most assuredly, either the urine is conveyed by its own motion to the kidneys, considering this the better course (as do we when we go off to market!), or, if this be impossible, then some other reason for its conveyance³ must be found. What, then, is this? If we are not going to grant the kidneys a faculty⁴ for attracting this particular quality, as Hippocrates held, we shall discover no other reason. For, surely everyone sees that either the kidneys must attract the urine, or the veins⁵ must propel it — if, that is, it does not move of itself. But if the veins did exert a propulsive⁷ action when they contract, they would squeeze out into the kidneys not merely the urine, but along with it the whole of the blood which they contain. And if this is impossible, as we shall show, the remaining explanation is that the kidneys do exert traction⁸.

And how is propulsion by the veins impossible? The situation of the kidneys is against it. They do not occupy a position beneath the hollow vein⁶ [vena cava] as does the sieve-like [ethmoid] passage in the nose and palate in relation to the surplus matter from the brain; they are situated⁹ on both sides of it. Besides, if the kidneys are like sieves¹⁰, and readily let the thinner serous [whey-like] portion through, and keep out the thicker portion, then the whole of the blood contained in the vena cava must go to them, just as the whole of the wine is thrown into the filters. Further, the example of milk being made into cheese will show clearly what I mean. For this, too, although it is all thrown into the wicker strainers, does not all percolate¹¹ through; such part of it as is too fine in proportion to the width of the meshes¹² passes downwards¹³, and this is called whey [serum]; the remaining thick portion which is destined¹⁴ to become cheese cannot get down, since the pores of the strainers will not admit it. Thus it is that, if the blood-serum has similarly to percolate through the kidneys, the whole of the blood must come to them, and not merely one part of it.

What, then, is the appearance as found on dissection¹⁵?

One division of the vena cava is carried upwards¹⁶ to the heart, and the other mounts upon the spine¹⁷ and extends along its whole length as far as the legs; thus one division does not even come near the kidneys, while the other approaches them but is certainly not inserted into them. Now, if the blood were destined to be purified by them as if they were sieves, the whole of it would have to fall into them, the thin part being and the thick part retained above. But, as a matter of fact, this is not so. For the kidneys lie on either side of the vena cava. They therefore do not act like sieves, filtering fluid sent to them by the vena cava, and themselves contributing no force. They obviously exert traction; for this is the only remaining alternative.

How, then, do they exert this traction? If, as Epicurus thinks, all attraction takes place by virtue¹⁸ of the rebounds¹⁹ and entanglements²⁰ of atoms, it would be certainly better to maintain that the kidneys have no attractive action at all; for his theory, when examined, would be found as it stands to be much more ridiculous even than the theory of the lodestone, mentioned a little while ago. Attraction occurs in the way that Hippocrates laid down; this will be stated more clearly as the discussion proceeds; for the present our task is not to demonstrate this, but to point out that no other cause of the secretion of urine can be given except that of attraction by the kidneys, and that this attraction does not take place in the way imagined by people who do not allow Nature a faculty of her own.

For if it be granted that there is any attractive faculty at all in those things which are governed by Nature, a person who attempted to say anything else about the absorption of nutriment would be considered a fool.

1 secretion   

n.分泌

参考例句：

• Is there much secretion from your eyes?你眼里的分泌物多吗？
• In addition,excessive secretion of oil,water scarcity are also major factors.除此之外，油脂分泌过盛、缺水也都是主要因素。

2 absurdities   

n.极端无理性( absurdity的名词复数 )；荒谬；谬论；荒谬的行为

参考例句：

• She has a sharp eye for social absurdities, and compassion for the victims of social change. 她独具慧眼，能够看到社会上荒唐的事情，对于社会变革的受害者寄以同情。 来自辞典例句
• The absurdities he uttered at the dinner party landed his wife in an awkward situation. 他在宴会上讲的荒唐话使他太太陷入窘境。 来自辞典例句

3 conveyance   

n.(不动产等的)转让，让与；转让证书；传送；运送；表达；（正）运输工具

参考例句：

• Bicycles have become the most popular conveyance for Chinese people.自行车已成为中国人最流行的代步工具。
• Its another,older,usage is a synonym for conveyance.它的另一个更古老的习惯用法是作为财产转让的同义词使用。

4 faculty   

n.才能；学院，系；(学院或系的)全体教学人员

参考例句：

• He has a great faculty for learning foreign languages.他有学习外语的天赋。
• He has the faculty of saying the right thing at the right time.他有在恰当的时候说恰当的话的才智。

5 veins   

n.纹理；矿脉( vein的名词复数 )；静脉；叶脉；纹理

参考例句：

• The blood flows from the capillaries back into the veins. 血从毛细血管流回静脉。 来自《简明英汉词典》
• I felt a pleasant glow in all my veins from the wine. 喝过酒后我浑身的血都热烘烘的，感到很舒服。 来自《简明英汉词典》

6 vein   

n.血管，静脉；叶脉，纹理；情绪；vt.使成脉络

参考例句：

• The girl is not in the vein for singing today.那女孩今天没有心情唱歌。
• The doctor injects glucose into the patient's vein.医生把葡萄糖注射入病人的静脉。

7 propulsive   

adj.推进的

参考例句：

• The fish uses its tail fins for propulsive force throgh the water.鱼靠尾鳍在水中前进。
• Interest in jet propulsive force was now growing at the Air Ministry.航空部对喷气推进的兴趣正在增加。

8 traction   

n.牵引；附着摩擦力

参考例句：

• I'll show you how the traction is applied.我会让你看如何做这种牵引。
• She's injured her back and is in traction for a month.她背部受伤，正在作一个月的牵引治疗。

9 situated   

adj.坐落在...的，处于某种境地的

参考例句：

• The village is situated at the margin of a forest.村子位于森林的边缘。
• She is awkwardly situated.她的处境困难。

10 sieves   

筛，漏勺( sieve的名词复数 )

参考例句：

• This thesis emphasized on the preparation of mesoporous molecular sieves MSU. 中孔分子筛MSU是当今认为在稳定性方面很有发展前途的一种催化新材料。
• The mesoporous silica molecular sieves Zr-MCM-41 were synthesized in ethylenediamine. 以乙二胺为碱性介质合成了Zr-MCM-41介孔分子筛。

11 percolate   

v.过滤，渗透

参考例句：

• The rain will percolate through the soil.雨水渗入土中。
• New fashions took a long time to percolate down.新时尚要很长时间才能在大众中流行起来。

12 meshes   

网孔( mesh的名词复数 )； 网状物； 陷阱； 困境

参考例句：

• The net of Heaven has large meshes, but it lets nothing through. 天网恢恢，疏而不漏。
• This net has half-inch meshes. 这个网有半英寸见方的网孔。

13 downwards   

adj./adv.向下的（地），下行的（地）

参考例句：

• He lay face downwards on his bed.他脸向下伏在床上。
• As the river flows downwards,it widens.这条河愈到下游愈宽。

14 destined   

adj.命中注定的；(for)以…为目的地的

参考例句：

• It was destined that they would marry.他们结婚是缘分。
• The shipment is destined for America.这批货物将运往美国。

15 dissection   

n.分析；解剖

参考例句：

• A dissection of your argument shows several inconsistencies.对你论点作仔细分析后发现一些前后矛盾之处。
• Researchers need a growing supply of corpses for dissection.研究人员需要更多的供解剖用的尸体。

16 upwards   

adv.向上，在更高处...以上

参考例句：

• The trend of prices is still upwards.物价的趋向是仍在上涨。
• The smoke rose straight upwards.烟一直向上升。

17 spine   

n.脊柱，脊椎；(动植物的)刺；书脊

参考例句：

• He broke his spine in a fall from a horse.他从马上跌下摔断了脊梁骨。
• His spine developed a slight curve.他的脊柱有点弯曲。

18 virtue   

n.德行，美德；贞操；优点；功效，效力

参考例句：

• He was considered to be a paragon of virtue.他被认为是品德尽善尽美的典范。
• You need to decorate your mind with virtue.你应该用德行美化心灵。

19 rebounds   

反弹球( rebound的名词复数 )； 回弹球； 抢断篮板球； 复兴

参考例句：

• V is the velocity after the gas particle rebounds from the wall. V是粒子从壁上弹开后的速度。
• In the former case, the first body rebounds with practically its original velocity. 在前一种情况下，第一个物体实际上以原来的速度弹回。

20 entanglements   

n.瓜葛( entanglement的名词复数 )；牵连；纠缠；缠住

参考例句：

• Mr. White threaded his way through the legal entanglements. 怀特先生成功地解决了这些法律纠纷。 来自《简明英汉词典》
• At dawn we broke through the barbed wire entanglements under the city wall. 拂晓我们突破了城墙的铁丝网。 来自《简明英汉词典》