Book I chapter 5

Besides, quadrupeds have the organ of copulation, since it is possible for them to have it, but for birds and the footless animals it is not possible, because the former have their legs under the middle of the abdomen¹ and the latter have no legs at all; now the penis depends from that region and is situated² there. (Wherefore also the legs are strained in intercourse³, both the penis and the legs being sinewy⁴.) So that, since it is not possible for them to have this organ, they must necessarily either have no testes also, or at any rate not have them there, as those animals that have both penis and testes have them in the same situation.

Further, with those animals at any rate that have external testes, the semen is collected together before emission⁵, and emission is due to the penis being heated by its movement; it is not ready for emission at immediate⁶ contact as in fishes.

All the vivipira have their testes in front, internally or externally, except the hedgehog; he alone has them near the loin. This is for the same reason as with birds, because their union must be quick, for the hedgehog does not, like the other quadrupeds, mount upon the back of the female, but they conjugate⁷ standing⁸ upright because of their spines⁹.

So much for the reasons why those animals have testes which have them, and why they are sometimes external and sometimes internal.

1 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。

2 situated   

adj.坐落在...的，处于某种境地的

参考例句：

• The village is situated at the margin of a forest.村子位于森林的边缘。
• She is awkwardly situated.她的处境困难。

3 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。

4 sinewy   

adj.多腱的，强壮有力的

参考例句：

• When muscles are exercised often and properly,they keep the arms firm and sinewy.如果能经常正确地锻炼肌肉的话，双臂就会一直结实而强健。
• His hard hands and sinewy sunburned limbs told of labor and endurance.他粗糙的双手，被太阳哂得发黑的健壮四肢,均表明他十分辛勤，非常耐劳。

5 emission   

n.发出物，散发物；发出，散发

参考例句：

• Rigorous measures will be taken to reduce the total pollutant emission.采取严格有力措施，降低污染物排放总量。
• Finally,the way to effectively control particulate emission is pointed out.最后，指出有效降低颗粒排放的方向。

6 immediate   

adj.立即的；直接的，最接近的；紧靠的

参考例句：

• His immediate neighbours felt it their duty to call.他的近邻认为他们有责任去拜访。
• We declared ourselves for the immediate convocation of the meeting.我们主张立即召开这个会议。

7 conjugate   

vt.使成对，使结合；adj.共轭的，成对的

参考例句：

• A partition that is its own conjugate is ealled self-conjugate.一个分析如与其自身共轭称为自共轭。
• It is important to learn to conjugate irregular verbs.学会不规则动词的变化是相当重要的。

8 standing   

n.持续，地位；adj.永久的，不动的，直立的，不流动的

参考例句：

• After the earthquake only a few houses were left standing.地震过后只有几幢房屋还立着。
• They're standing out against any change in the law.他们坚决反对对法律做任何修改。

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》