Book II Chapter 8

In men, then, and in other kinds, as said before, such deficiency occurs sporadically¹, but the whole of the mule² kind is sterile³. The reason has not been rightly given by Empedocles and Democritus, of whom the former expresses himself obscurely, the latter more intelligibly⁴. For they offer their demonstration⁵ in the case of all these animals alike which unite against their affinities⁶. Democritus says that the genital passages of mules⁸ are spoilt in the mother’s uterus because the animals from the first are not produced from parents of the same kind. But we find that though this is so with other animals they are none the less able to generate; yet, if this were the reason, all others that unite in this manner ought to be barren. Empedocles assigns as his reason that the mixture of the ‘seeds’ becomes dense⁹, each of the two seminal¹⁰ fluids out of which it is made being soft, for the hollows in each fit into the densities¹¹ of the other, and in such cases a hard substance is formed out of soft ones, like bronze mingled¹² with tin. Now he does not give the correct reason in the case of bronze and tin —(we have spoken of them in the Problems)— nor, to take general ground, does he take his principles from the intelligible¹³. How do the ‘hollows’ and ‘solids’ fit into one another to make the mixing, e.g. in the case of wine and water? This saying is quite beyond us; for how we are to understand the ‘hollows’ of the wine and water is too far beyond our perception. Again, when, as a matter of fact, horse is born of horse, ass⁷ of ass, and mule of horse and ass in two ways according as the parents are stallion and she-ass or jackass and mare¹⁴, why in the last case does there result something so ‘dense’ that the offspring is sterile, whereas the offspring of male and female horse, male and female ass, is not sterile? And yet the generative fluid of the male and female horse is soft. But both sexes of the horse cross with both sexes of the ass, and the offspring of both crosses are barren, according to Empedocles, because from both is produced something ‘dense’, the ‘seeds’ being ‘soft’. If so, the offspring of stallion and mare ought also to be sterile. If one of them alone united with the ass, it might be said that the cause of the mule’s being unable to generate was the unlikeness of that one to the generative fluid of the ass; but, as it is, whatever be the character of that generative fluid with which it unites in the ass, such it is also in the animal of its own kind. Then, again, the argument is intended to apply to both male and female mules alike, but the male does generate at seven years of age, it is said; it is the female alone that is entirely¹⁵ sterile, and even she is so only because she does not complete the development of the embryo¹⁶, for a female mule has been known to conceive.

Perhaps an abstract proof might appear to be more plausible¹⁷ than those already given; I call it abstract because the more general it is the further is it removed from the special principles involved. It runs somewhat as follows. From male and female of the same species there are born in course of nature male and female of the same species as the parents, e.g. male and female puppies from male and female dog. From parents of different species is born a young one different in species; thus if a dog is different from a lion, the offspring of male dog and lioness or of lion and bitch will be different from both parents. If this is so, then since (1) mules are produced of both sexes and are not different in species from one another, and (2) a mule is born of horse and ass and these are different in species from mules, it is impossible that anything should be produced from mules. For (1) another kind cannot be, because the product of male and female of the same species is also of the same species, and (2) a mule cannot be, because that is the product of horse and ass which are different in form, [and it was laid down that from parents different in form is born a different animal]. Now this theory is too general and empty. For all theories not based on the special principles involved are empty; they only appear to be connected with the facts without being so really. As geometrical arguments must start from geometrical principles, so it is with the others; that which is empty may seem to be something, but is really nothing. Now the basis of this particular theory is not true, for many animals of different species are fertile with one another, as was said before. So we must not inquire into questions of natural science in this fashion any more than any other questions; we shall be more likely to find the reason by considering the facts peculiar¹⁸ to the two kinds concerned, horse and ass. In the first place, each of them, if mated with its own kind, bears only one young one; secondly¹⁹, the females are not always able to conceive from the male (wherefore breeders put the horse to the mare again at intervals). Indeed, both the mare is deficient²⁰ in catamenia, discharging less than any other quadruped, and the she-ass does not admit the impregnation, but ejects the semen with her urine, wherefore men follow flogging her after intercourse²¹. Again the ass is an animal of cold nature, and so is not wont²² to be produced in wintry regions because it cannot bear cold, as in Scythia and the neighbouring country and among the Celts beyond Iberia, for this country also is cold. For this cause they do not put the jackasses to the females at the equinox, as they do with horses, but about the summer solstice, in order that the ass-foals may be born in a warm season, for the mothers bear at the same season as that in which they are impregnated, the period of gestation²³ in both horse and ass being one year. The animal, then, being, as has been said of such a cold nature, its semen also must be cold. A proof of this is that if a horse mount a female already impregnated by an ass he does not destroy the impregnation of the ass, but if the ass be the second to mount her he does destroy that of the horse because of the coldness of his own semen. When, therefore, they unite with each other, the generative elements are preserved by the heat of the one of them, that contributed by the horse being the hotter; for in the ass both the semen of the male and the material contributed by the female are cold, and those of the horse, in both sexes, are hotter. Now when either hot is added to cold or cold to hot so as to mix, the result is that the embryo itself arising from these is preserved and thus these animals are fertile when crossed with one another, but the animal produced by them is no longer fertile but unable to produce perfect offspring.

And in general each of these animals naturally tends towards sterility²⁴. The ass has all the disadvantages already mentioned, and if it should not begin to generate after the first shedding of teeth, it no longer generates at all; so near is the constitution of the ass to being sterile. The horse is much the same; it tends naturally towards sterility, and to make it entirely so it is only necessary that its generative secretion²⁵ should become colder; now this is what happens to it when mixed with the corresponding secretion of the ass. The ass in like manner comes very near generating a sterile animal when mated with its own species. Thus when the difficulty of a cross contrary to nature is added, (when too even in the other case when united with their own species they with difficulty produce a single young one), the result of the cross, being still more sterile and contrary to nature, will need nothing further to make it sterile, but will be so of necessity.

We find also that the bodies of female mules grow large because the matter which is secreted²⁶ in other animals to form the catamenia is diverted to growth. But since the period of gestation in such animals is a year, the mule must not only conceive, if she is to be fertile, but must also nourish the embryo till birth, and this is impossible if there are no catamenia. But there are none in the mule; the useless part of the nutriment is discharged with the excretion from the bladder — this is why male mules do not smell to the pudenda of the females, as do the other solid-hoofed ungulates, but only to the evacuation itself — and the rest of the nutriment is used up to increase the size of the body. Hence it is sometimes possible for the female to conceive, as has been known to happen before now, but it is impossible for her to complete the process of nourishing the embryo and bringing it to birth.

The male, again, may sometimes generate, both because the male sex is naturally hotter than the female and because it does not contribute any material substance to the mixture. The result in such cases is a ‘ginnus’, that is to say, a dwarf²⁷ mule; for ‘ginni’ are produced also from the crossing of horse and ass when the embryo is diseased in the uterus. The ginnus is in fact like the so-called ‘metachoera’ in swine, for a ‘metachoerum’ also is a pig injured in the uterus; this may happen to any pig. The origin of human dwarfs²⁸ is similar, for these also have their parts and their whole development injured during gestation, and resemble ginni and metachoera.

1 sporadically   

adv.偶发地，零星地

参考例句：

• There are some trees sporadically around his house. 他的房子周围零星地有点树木。 来自辞典例句
• As for other aspects, we will sporadically hand out questionnaires. 在其他方面，我们会偶尔发送调查问卷。 来自互联网

2 mule   

n.骡子，杂种，执拗的人

参考例句：

• A mule is a cross between a mare and a donkey.骡子是母马和公驴的杂交后代。
• He is an old mule.他是个老顽固。

3 sterile   

adj.不毛的，不孕的，无菌的，枯燥的，贫瘠的

参考例句：

• This top fits over the bottle and keeps the teat sterile.这个盖子严实地盖在奶瓶上，保持奶嘴无菌。
• The farmers turned the sterile land into high fields.农民们把不毛之地变成了高产田。

4 intelligibly   

adv.可理解地，明了地，清晰地

参考例句：

• The foreigner spoke to us quite intelligibly. 这个外国人对我们讲的话理解很好。 来自《简明英汉词典》
• Logically or intelligibly ordered or presented; coherent. 有逻辑或理性地排列或表现的；协调的。 来自互联网

5 demonstration   

n.表明，示范，论证，示威

参考例句：

• His new book is a demonstration of his patriotism.他写的新书是他的爱国精神的证明。
• He gave a demonstration of the new technique then and there.他当场表演了这种新的操作方法。

6 affinities   

n.密切关系( affinity的名词复数 )；亲近；（生性）喜爱；类同

参考例句：

• Cubism had affinities with the new European interest in Jazz. 主体派和欧洲新近的爵士音乐热有密切关系。 来自辞典例句
• The different isozymes bind calcium ions with different affinities. 不同的同功酶以不同的亲和力与钙离子相结合。 来自辞典例句

7 ass   

n.驴；傻瓜，蠢笨的人

参考例句：

• He is not an ass as they make him.他不象大家猜想的那样笨。
• An ass endures his burden but not more than his burden.驴能负重但不能超过它能力所负担的。

8 mules   

骡( mule的名词复数 )； 拖鞋； 顽固的人； 越境运毒者

参考例句：

• The cart was pulled by two mules. 两匹骡子拉这辆大车。
• She wore tight trousers and high-heeled mules. 她穿紧身裤和拖鞋式高跟鞋。

9 dense   

a.密集的，稠密的，浓密的；密度大的

参考例句：

• The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
• The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。

10 seminal   

adj.影响深远的；种子的

参考例句：

• The reforms have been a seminal event in the history of the NHS.这些改革已成为英国国民保健制度史上影响深远的一件大事。
• The emperor's importance as a seminal figure of history won't be diminished.做为一个开创性历史人物的重要性是不会减弱的。

11 densities   

密集( density的名词复数 )； 稠密； 密度（固体、液体或气体单位体积的质量）； 密度（磁盘存贮数据的可用空间）

参考例句：

• The range of densities of interest is about 3.5. 有用的密度范围为3．5左右。
• Densities presumably can be probed by radar. 利用雷达也许还能探测出气体的密度。

12 mingled   

混合，混入( mingle的过去式和过去分词 )； 混进，与…交往[联系]

参考例句：

• The sounds of laughter and singing mingled in the evening air. 笑声和歌声交织在夜空中。
• The man and the woman mingled as everyone started to relax. 当大家开始放松的时候，这一男一女就开始交往了。

13 intelligible   

adj.可理解的，明白易懂的，清楚的

参考例句：

• This report would be intelligible only to an expert in computing.只有计算机运算专家才能看懂这份报告。
• His argument was barely intelligible.他的论点不易理解。

14 mare   

n.母马，母驴

参考例句：

• The mare has just thrown a foal in the stable.那匹母马刚刚在马厩里产下了一只小马驹。
• The mare foundered under the heavy load and collapsed in the road.那母马因负载过重而倒在路上。

15 entirely   

ad.全部地，完整地；完全地，彻底地

参考例句：

• The fire was entirely caused by their neglect of duty. 那场火灾完全是由于他们失职而引起的。
• His life was entirely given up to the educational work. 他的一生统统献给了教育工作。

16 embryo   

n.胚胎，萌芽的事物

参考例句：

• They are engaging in an embryo research.他们正在进行一项胚胎研究。
• The project was barely in embryo.该计划只是个雏形。

17 plausible   

adj.似真实的，似乎有理的，似乎可信的

参考例句：

• His story sounded plausible.他说的那番话似乎是真实的。
• Her story sounded perfectly plausible.她的说辞听起来言之有理。

18 peculiar   

adj.古怪的，异常的；特殊的，特有的

参考例句：

• He walks in a peculiar fashion.他走路的样子很奇特。
• He looked at me with a very peculiar expression.他用一种很奇怪的表情看着我。

19 secondly   

adv.第二，其次

参考例句：

• Secondly,use your own head and present your point of view.第二，动脑筋提出自己的见解。
• Secondly it is necessary to define the applied load.其次，需要确定所作用的载荷。

20 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。

21 intercourse   

n.性交；交流，交往，交际

参考例句：

• The magazine becomes a cultural medium of intercourse between the two peoples.该杂志成为两民族间文化交流的媒介。
• There was close intercourse between them.他们过往很密。

22 wont   

adj.习惯于；v.习惯；n.习惯

参考例句：

• He was wont to say that children are lazy.他常常说小孩子们懒惰。
• It is his wont to get up early.早起是他的习惯。

23 gestation   

n.怀孕；酝酿

参考例句：

• The gestation period can be anything between 95 and 150 days.妊娠期从95天至150天不等。
• This film was two years in gestation.这部电影酝酿了两年。

24 sterility   

n.不生育，不结果，贫瘠，消毒，无菌

参考例句：

• A major barrier to interspecific hybridization is sterility in the F1 progeny.种间杂交的主要障碍是F1代的不育性。
• Sterility is some permanent factor preventing procreation.不育是阻碍生殖的一种永久性因素。

25 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。

26 secreted   

v.（尤指动物或植物器官）分泌( secrete的过去式和过去分词 )；隐匿，隐藏

参考例句：

• Insulin is secreted by the pancreas. 胰岛素是胰腺分泌的。
• He secreted his winnings in a drawer. 他把赢来的钱藏在抽届里。 来自《简明英汉词典》

27 dwarf   

n.矮子，侏儒，矮小的动植物；vt.使…矮小

参考例句：

• The dwarf's long arms were not proportional to his height.那侏儒的长臂与他的身高不成比例。
• The dwarf shrugged his shoulders and shook his head. 矮子耸耸肩膀，摇摇头。

28 dwarfs   

n.侏儒，矮子（dwarf的复数形式）vt.（使）显得矮小（dwarf的第三人称单数形式）

参考例句：

• Shakespeare dwarfs other dramatists. 莎士比亚使其他剧作家相形见绌。 来自《简明英汉词典》
• The new building dwarfs all the other buildings in the town. 新大楼使城里所有其他建筑物都显得矮小了。 来自辞典例句