Chapter 7

It is clear then how locomotion¹ belongs to those animals only which make their changes of place by means of two or four points in their structure, or to such animals par² excellence³. Moreover, since this property belongs almost peculiarly to Sanguineous animals, we see that no Sanguineous animal can progress at more points than four, and that if it is the nature of anything so to progress at four points it must of necessity be Sanguineous.

What we observe in the animal world is in agreement with the above account. For no Sanguineous animal if it be divided into more parts can live for any appreciable⁴ length of time, nor can it enjoy the power of locomotion which it possessed⁵ while it was a continuous and undivided whole. But some bloodless animals and polypods can live a long time, if divided, in each of the severed⁶ parts, and can move in the same way as before they were dismembered. Examples are what is termed the centipede and other insects that are long in shape, for even the hinder portion of all these goes on progressing in the same direction as before when they are cut in two.

The explanation of their living when thus divided is that each of them is constructed like a continuous body of many separate living beings. It is plain, too, from what was said above why they are like this. Animals constructed most naturally are made to move at two or four points, and even limbless Sanguinea are no exception. They too move by dint⁸ of four points, whereby they achieve progression. They go forward by means of two flexions. For in each of their flexions there is a right and a left, both before and behind in their flat surface, in the part towards the head a right and a left front point, and in the part towards the tail the two hinder points. They look as if they moved at two points only, where they touch before and behind, but that is only because they are narrow in breadth. Even. in them the right is the sovereign part, and there is an alternate correspondence behind, exactly as in quadrupeds. The reason of their flexions is their great length, for just as tall men walk with their spines⁹ bellied¹⁰ (undulated) forward, and when their right shoulder is leading in a forward direction their left hip¹¹ rather inclined backwards¹², so that their middle becomes hollow and bellied (undulated), so we ought to conceive snakes as moving in concave curves (undulations) upon the ground. And this is evidence that they move themselves like the quadrupeds, for they make the concave in its turn convex and the convex concave. When in its turn the left of the forward parts is leading, the concavity is in its turn reversed, for the right becomes the inner. (Let the right front point be A, the left B, the right hind⁷ C, the left D.)

Among land animals this is the character of the movement of snakes, and among water animals of eels¹³, and conger-eels and also lampreys, in fact of all that have their form snakelike. However, some marine¹⁴ animals of this shape have no fin¹⁵, lampreys for example, but put the sea to the same use as snakes do both land and water (for snakes swim precisely¹⁶ as they move on the ground). Others have two fins¹⁷ only, for example conger-eels and eels and a kind of cestreus which breeds in the lake of Siphae. On this account too those that are accustomed to live on land, for example all the eels, move with fewer flexions in a fluid than on land, while the kind of cestreus which has two fins, by its flexion in a fluid makes up the remaining points.

1 locomotion   

n.运动，移动

参考例句：

• By land,air or sea,birds are masters of locomotion.无论是通过陆地，飞越空中还是穿过海洋，鸟应算是运动能手了。
• Food sources also elicit oriented locomotion and recognition behavior patterns in most insects.食物源也引诱大多数昆虫定向迁移和识别行为。

2 par   

n.标准，票面价值，平均数量；adj.票面的，平常的，标准的

参考例句：

• Sales of nylon have been below par in recent years.近年来尼龙织品的销售额一直不及以往。
• I don't think his ability is on a par with yours.我认为他的能力不能与你的能力相媲美。

3 excellence   

n.优秀，杰出，(pl.)优点，美德

参考例句：

• His art has reached a high degree of excellence.他的艺术已达到炉火纯青的地步。
• My performance is far below excellence.我的表演离优秀还差得远呢。

4 appreciable   

adj.明显的，可见的，可估量的，可觉察的

参考例句：

• There is no appreciable distinction between the twins.在这对孪生子之间看不出有什么明显的差别。
• We bought an appreciable piece of property.我们买下的资产有增值的潜力。

5 possessed   

adj.疯狂的；拥有的，占有的

参考例句：

• He flew out of the room like a man possessed.他像着了魔似地猛然冲出房门。
• He behaved like someone possessed.他行为举止像是魔怔了。

6 severed   

v.切断，断绝( sever的过去式和过去分词 )；断，裂

参考例句：

• The doctor said I'd severed a vessel in my leg. 医生说我割断了腿上的一根血管。 来自《简明英汉词典》
• We have severed diplomatic relations with that country. 我们与那个国家断绝了外交关系。 来自《简明英汉词典》

7 hind   

adj.后面的，后部的

参考例句：

• The animal is able to stand up on its hind limbs.这种动物能够用后肢站立。
• Don't hind her in her studies.不要在学业上扯她后腿。

8 dint   

n.由于，靠；凹坑

参考例句：

• He succeeded by dint of hard work.他靠苦干获得成功。
• He reached the top by dint of great effort.他费了很大的劲终于爬到了顶。

9 spines   

n.脊柱( spine的名词复数 )；脊椎；（动植物的）刺；书脊

参考例句：

• Porcupines use their spines to protect themselves. 豪猪用身上的刺毛来自卫。
• The cactus has spines. 仙人掌有刺。 来自《现代英汉综合大词典》

10 bellied   

adj.有腹的，大肚子的

参考例句：

• That big-bellied fellow was very cruel and greedy. 那个大腹便便的家伙既贪婪又残恶。 来自《现代汉英综合大词典》
• The ship's sails bellied in the wind. 船帆在风中鼓得大大的。 来自《现代汉英综合大词典》

11 hip   

n.臀部，髋；屋脊

参考例句：

• The thigh bone is connected to the hip bone.股骨连着髋骨。
• The new coats blouse gracefully above the hip line.新外套在臀围线上优美地打着褶皱。

12 backwards   

adv.往回地，向原处，倒，相反，前后倒置地

参考例句：

• He turned on the light and began to pace backwards and forwards.他打开电灯并开始走来走去。
• All the girls fell over backwards to get the party ready.姑娘们迫不及待地为聚会做准备。

13 eels   

abbr. 电子发射器定位系统（=electronic emitter location system）

参考例句：

• Eels have been on the feed in the Lower Thames. 鳗鱼在泰晤士河下游寻食。
• She bought some eels for dinner. 她买回一些鳗鱼做晚餐。

14 marine   

adj.海的；海生的；航海的；海事的；n.水兵

参考例句：

• Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
• When the war broke out,he volunteered for the Marine Corps.战争爆发时，他自愿参加了海军陆战队。

15 fin   

n.鳍；(飞机的)安定翼

参考例句：

• They swim using a small fin on their back.它们用背上的小鳍游动。
• The aircraft has a long tail fin.那架飞机有一个长长的尾翼。

16 precisely   

adv.恰好，正好，精确地，细致地

参考例句：

• It's precisely that sort of slick sales-talk that I mistrust.我不相信的正是那种油腔滑调的推销宣传。
• The man adjusted very precisely.那个人调得很准。

17 fins   

[医]散热片；鱼鳍；飞边；鸭掌

参考例句：

• The level of TNF-α positively correlated with BMI,FPG,HbA1C,TG,FINS and IRI,but not with SBP and DBP. TNF-α水平与BMI、FPG、HbA1C、TG、FINS和IRI呈显著正相关，与SBP、DBP无相关。 来自互联网
• Fins are a feature specific to fish. 鱼鳍是鱼类特有的特征。 来自辞典例句