Book I chapter 12

Why is the uterus always internal, but the testes sometimes internal, sometimes external? The reason for the uterus always being internal is that in this is contained the egg or foetus, which needs guarding, shelter, and maturation by concoction¹, while the outer surface of the body is easily injured and cold. The testes vary in position because they also need shelter and a covering to preserve them and to mature the semen; for it would be impossible for them, if chilled and stiffened², to be drawn³ up and discharge it. Therefore, whenever the testes are visible, they have a cuticular⁴ covering known as the scrotum. If the nature of the skin is opposed to this, being too hard to be adapted for enclosing them or for being soft like a true ‘skin’, as with the scaly⁵ integument⁶ of fish and reptiles⁷, then the testes must needs be internal. Therefore they are so in dolphins and all the cetacea which have them, and in the oviparous quadrupeds among the scaly animals. The skin of birds also is hard so that it will not conform to the size of anything and enclose it neatly⁸. (This is another reason with all these animals for their testes being internal besides those previously⁹ mentioned as arising necessarily from the details of copulation.) For the same reason they are internal in the elephant and hedgehog, for the skin of these, too, is not well suited to keep the protective part separate.

[The position of the uterus differs in animals viviparous within themselves and those externally oviparous, and in the latter class again it differs in those which have the uterus low and those which have it near the hypozoma, as in fishes compared with birds and oviparous quadrupeds. And it is different again in those which produce young in both ways, being oviparous internally and viviparous externally. For those which are viviparous both internally and externally have the uterus placed on the abdomen¹⁰, as men, cattle, dogs, and the like, since it is expedient¹¹ for the safety and growth of the foetus that no weight should be upon the uterus.]

1 concoction   

n.调配(物)；谎言

参考例句：

• She enjoyed the concoction of foreign dishes.她喜欢调制外国菜。
• His story was a sheer concoction.他的故事实在是一纯属捏造之事。

2 stiffened   

加强的

参考例句：

• He leaned towards her and she stiffened at this invasion of her personal space. 他向她俯过身去，这种侵犯她个人空间的举动让她绷紧了身子。
• She stiffened with fear. 她吓呆了。

3 drawn   

v.拖，拉，拔出；adj.憔悴的，紧张的

参考例句：

• All the characters in the story are drawn from life.故事中的所有人物都取材于生活。
• Her gaze was drawn irresistibly to the scene outside.她的目光禁不住被外面的风景所吸引。

4 cuticular   

adj.表皮的

参考例句：

• Commonly bacterium of gules and cuticular tinea waits. 常见的有红色表皮癣菌等。 来自互联网
• Cuticular cell organization and embedded material call the skin to protect wet organization jointly. 表皮细胞组织与内含物质共同称为皮肤保湿机构。 来自互联网

5 scaly   

adj.鱼鳞状的；干燥粗糙的

参考例句：

• Reptiles possess a scaly,dry skin.爬行类具有覆盖着鳞片的干燥皮肤。
• The iron pipe is scaly with rust.铁管子因为生锈一片片剥落了。

6 integument   

n.皮肤

参考例句：

• The first protector against the entry of microorganisms is the integument.抗御微生物进入体内的第一道防线是皮肤。
• The cells of the integument and nucellus of some plants form perfectly normal embryos.某些植物的珠被和珠心细胞形成完全正常的胚。

7 reptiles   

n.爬行动物，爬虫( reptile的名词复数 )

参考例句：

• Snakes and crocodiles are both reptiles. 蛇和鳄鱼都是爬行动物。 来自《简明英汉词典》
• Birds, reptiles and insects come from eggs. 鸟类、爬虫及昆虫是卵生的。 来自《现代汉英综合大词典》

8 neatly   

adv.整洁地，干净地，灵巧地，熟练地

参考例句：

• Sailors know how to wind up a long rope neatly.水手们知道怎样把一条大绳利落地缠好。
• The child's dress is neatly gathered at the neck.那孩子的衣服在领口处打着整齐的皱褶。

9 previously   

adv.以前，先前（地）

参考例句：

• The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
• Let me digress for a moment and explain what had happened previously.让我岔开一会儿，解释原先发生了什么。

10 abdomen   

n.腹，下腹(胸部到腿部的部分)

参考例句：

• How to know to there is ascarid inside abdomen?怎样知道肚子里面有蛔虫？
• He was anxious about an off-and-on pain the abdomen.他因时隐时现的腹痛而焦虑。

11 expedient   

adj.有用的，有利的；n.紧急的办法，权宜之计

参考例句：

• The government found it expedient to relax censorship a little.政府发现略微放宽审查是可取的。
• Every kind of expedient was devised by our friends.我们的朋友想出了各种各样的应急办法。