Book v chapter 4

But as to their colour, it is the nature of the skin that is the cause of this in other animals and also of their being uni-coloured or vari-coloured); but in man it is not the cause, except of the hair going grey through disease (not through old age), for in what is called leprosy the hairs become white; on the contrary, if the hairs are white the whiteness does not invade the skin. The reason is that the hairs grow out of skin; if, then, the skin is diseased and white the hair becomes diseased with it, and the disease of hair is greyness. But the greyness of hair which is due to age results from weakness and deficiency of heat. For as the body declines in vigour¹ we tend to cold at every time of life, and especially in old age, this age being cold and dry. We must remember that the nutriment coming to each part of the body is concocted³ by the heat appropriate to the part; if the heat is inadequate⁴ the part loses its efficiency, and destruction or disease results. (We shall speak more in detail of causes in the treatise⁵ on growth and nutrition.) Whenever, then, the hair in man has naturally little heat and too much moisture enters it, its own proper heat is unable to concoct² the moisture and so it is decayed by the heat in the environing air. All decay is caused by heat, not the innate⁶ heat but external heat, as has been stated elsewhere. And as there is a decay of water, of earth, and all such material bodies, so there is also of the earthy vapour, for instance what is called mould (for mould is a decay of earthy vapour). Thus also the liquid nutriment in the hair decays because it is not concocted, and what is called greyness results. It is white because mould also, practically alone among decayed things, is white. The reason of this is that it has much air in it, all earthy vapour being equivalent to thick air. For mould is, as it were, the antithesis⁷ of hoar-frost; if the ascending⁸ vapour be frozen it becomes hoar-frost, if it be decayed, mould. Hence both are on the surface of things, for vapour is superficial. And so the comic poets make a good metaphor⁹ in jest when they call grey hairs ‘mould of old age’ and For the one is generically¹⁰ the same as greyness, the other specifically; hoar-frost generically (for both are a vapour), mould specifically (for both are a form of decay). A proof that this is so is this: grey hairs have often grown on men in consequence of disease, and later on dark hairs instead of them after restoration to health. The reason is that in sickness the whole body is deficient¹¹ in natural heat and so the parts besides, even the very small ones, participate in this weakness; and again, much residual¹² matter is formed in the body and all its parts in illness, wherefore the incapacity in the flesh to concoct the nutriment causes the grey hairs. But when men have recovered health and strength again they change, becoming as it were young again instead of old; in consequence the states change also. Indeed, we may rightly call disease an acquired old age, old age a natural disease; at any rate, some diseases produce the same effects as old age.

Men go grey on the temples first, because the back of the head is empty of moisture owing to its containing no brain, and the ‘bregma’ has a great deal of moisture, a large quantity not being liable to decay; the hair on the temples however has neither so little that it can concoct it nor so much that it cannot decay, for this region of the head being between the two extremes is exempt¹³ from both states. The cause of greyness in man has now been stated.

1 vigour   

（=vigor）n.智力，体力，精力

参考例句：

• She is full of vigour and enthusiasm.她有热情，有朝气。
• At 40,he was in his prime and full of vigour.他40岁时正年富力强。

2 concoct   

v.调合，制造

参考例句：

• I gave her a tip on how to concoct a new kind of soup.我教她配制一种新汤的诀窍。
• I began to concoct explanations of my own.我开始思考自己的解释。

3 concocted   

v.将（尤指通常不相配合的）成分混合成某物( concoct的过去式和过去分词 )；调制；编造；捏造

参考例句：

• The soup was concocted from up to a dozen different kinds of fish. 这种汤是用多达十几种不同的鱼熬制而成的。
• Between them they concocted a letter. 他们共同策划写了一封信。 来自《简明英汉词典》

4 inadequate   

adj.(for,to)不充足的，不适当的

参考例句：

• The supply is inadequate to meet the demand.供不应求。
• She was inadequate to the demands that were made on her.她还无力满足对她提出的各项要求。

5 treatise   

n.专著；(专题)论文

参考例句：

• The doctor wrote a treatise on alcoholism.那位医生写了一篇关于酗酒问题的论文。
• This is not a treatise on statistical theory.这不是一篇有关统计理论的论文。

6 innate   

adj.天生的，固有的，天赋的

参考例句：

• You obviously have an innate talent for music.你显然有天生的音乐才能。
• Correct ideas are not innate in the mind.人的正确思想不是自己头脑中固有的。

7 antithesis   

n.对立；相对

参考例句：

• The style of his speech was in complete antithesis to mine.他和我的讲话方式完全相反。
• His creation was an antithesis to academic dogmatism of the time.他的创作与当时学院派的教条相对立。

8 ascending   

adj.上升的，向上的

参考例句：

• Now draw or trace ten dinosaurs in ascending order of size.现在按照体型由小到大的顺序画出或是临摹出10只恐龙。

9 metaphor   

n.隐喻，暗喻

参考例句：

• Using metaphor,we say that computers have senses and a memory.打个比方，我们可以说计算机有感觉和记忆力。
• In poetry the rose is often a metaphor for love.玫瑰在诗中通常作为爱的象征。

10 generically   

adv.一般地

参考例句：

• The so-called critics are generically mentioned, but not individually mentioned. 当所谓的批评提及时总是一笔带过，从不指名道姓。 来自互联网
• We market these drugs generically. 我们推广的这些药是未经注册的。 来自互联网

11 deficient   

adj.不足的，不充份的，有缺陷的

参考例句：

• The crops are suffering from deficient rain.庄稼因雨量不足而遭受损害。
• I always have been deficient in selfconfidence and decision.我向来缺乏自信和果断。

12 residual   

adj.复播复映追加时间；存留下来的，剩余的

参考例句：

• There are still a few residual problems with the computer program.电脑程序还有一些残留问题。
• The resulting residual chromatism is known as secondary spectrum.所得到的剩余色差叫做二次光谱。

13 exempt   

adj.免除的；v.使免除；n.免税者，被免除义务者

参考例句：

• These goods are exempt from customs duties.这些货物免征关税。
• He is exempt from punishment about this thing.关于此事对他已免于处分。