上句见：Day319
The Story of Philosophy《哲学的故事》第1章Plato第6节VI. The Psychological Problem第3段第3句：

Human behavior, says Plato, flows from three main sources: desire, emotion, and knowledge. Desire, appetite, impulse, instinct — these are one; emotion, spirit, ambition, courage — these are one; knowledge, thought, intellect, reason — these are one. Desire has its seat in the loins; it is bursting reservoir of energy, fundamentally sexual. Emotion has its seat in the heart, in the flow and force of the blood; it is the organic resonance of experience and desire. Knowledge has its seat in the head; it is the eye of desire, and can become the pilot of the soul.
浙江大学译本：欲望发端于腰部；从根本上说，它是性欲迸发的能量储备池。

解析

1、Desire has its seat in the loins;
欲望位于腰部；
have one’s seat in：“位于；在什么地方”；
The heart has its seat in the chest.
loins: the area of a person's body that includes the sexual organs腰
The general disapprovingly shook his head, and, rubbing his loins, went to the reception room, where the artist awaited him with the answer of Jeanne D'Arc.将军不以为然地摇了摇头，揉了揉腰，便朝接待室走去。在那里，那位艺术家正拿着圣女贞德所给的启示等着他。《复活》
2、 it is bursting reservoir of energy, fundamentally sexual.
它是能量的爆发库，本质上跟性相关。
reservoir: a place (such as a part of a machine) where a liquid is stored蓄水池
Drop by precious drop， this miracle water is channelled to a reservoir.一滴水接着一滴水，奇迹般地流入蓄水池。《人类星球》

这句开始解析欲望。

欲望位于腰部；它是能量的爆发库，本质上跟性相关。