Book III chapter 8

It is not every animal that has a bladder; those only being apparently¹ intended by nature to have one, whose lung contains blood. To such it was but reasonable that she should give this part. For the superabundance in their lung of its natural constituents² causes them to be the thirstiest of animals, and makes them require a more than ordinary quantity not merely of solid but also of liquid nutriment. This increased consumption necessarily entails³ the production of an increased amount of residue⁴; which thus becomes too abundant to be concocted⁵ by the stomach and excreted with its own residual⁶ matter. The residual fluid must therefore of necessity have a receptacle of its own; and thus it comes to pass that all animals whose lung contains blood are provided with a bladder. Those animals, on the other hand, that are without a lung of this character, and that either drink but sparingly owing to their lung being of a spongy texture⁷, or never imbibe⁸ fluid at all for drinking’s sake but only as nutriment, insects for instance and fishes, and that are moreover clad with feathers or scales or scaly⁹ plates-all these animals, owing to the small amount of fluid which they imbibe, and owing also to such residue as there may be being converted into feathers and the like, are invariably without a bladder. The Tortoises, which are comprised among animals with scaly plates, form the only exception; and this is merely due to the imperfect development of their natural conformation; the explanation of the matter being that in the sea-tortoises the lung is flesh-like and contains blood, resembling the lung of the ox, and that in the land-tortoises it is of disproportionately large size. Moreover, inasmuch as the covering which invests them is dense¹⁰ and shell-like, so that the moisture cannot exhale¹¹ through the porous¹² flesh, as it does in birds and in snakes and other animals with scaly plates, such an amount of secretion¹³ is formed that some special part is required to receive and hold it. This then is the reason why these animals, alone of their kind, have a bladder, the sea-tortoise a large one, the land-tortoises an extremely small one.

1 apparently   

adv.显然地；表面上，似乎

参考例句：

• An apparently blind alley leads suddenly into an open space.山穷水尽，豁然开朗。
• He was apparently much surprised at the news.他对那个消息显然感到十分惊异。

2 constituents   

n.选民( constituent的名词复数 )；成分；构成部分；要素

参考例句：

• She has the full support of her constituents. 她得到本区选民的全力支持。
• Hydrogen and oxygen are the constituents of water. 氢和氧是水的主要成分。 来自《简明英汉词典》

3 entails   

使…成为必要( entail的第三人称单数 )； 需要； 限定继承； 使必需

参考例句：

• The job entails a lot of hard work. 这工作需要十分艰苦的努力。
• This job entails a lot of hard work. 这项工作需要十分努力。

4 residue   

n.残余，剩余，残渣

参考例句：

• Mary scraped the residue of food from the plates before putting them under water.玛丽在把盘子放入水之前先刮去上面的食物残渣。
• Pesticide persistence beyond the critical period for control leads to residue problems.农药一旦超过控制的临界期，就会导致残留问题。

5 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》

6 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。

7 texture   

n.(织物)质地；(材料)构造；结构；肌理

参考例句：

• We could feel the smooth texture of silk.我们能感觉出丝绸的光滑质地。
• Her skin has a fine texture.她的皮肤细腻。

8 imbibe   

v.喝，饮；吸入，吸收

参考例句：

• Plants imbibe nourishment usually through their leaves and roots.植物通常经过叶和根吸收养分。
• I always imbibe fresh air in the woods.我经常在树林里呼吸新鲜空气。

9 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。

10 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。

11 exhale   

v.呼气，散出，吐出，蒸发

参考例句：

• Sweet odours exhale from flowers.花儿散发出花香。
• Wade exhaled a cloud of smoke and coughed.韦德吐出一口烟，然后咳嗽起来。

12 porous   

adj.可渗透的，多孔的

参考例句：

• He added sand to the soil to make it more porous.他往土里掺沙子以提高渗水性能。
• The shell has to be slightly porous to enable oxygen to pass in.外壳不得不有些细小的孔以便能使氧气通过。

13 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。