Kitap 7
1.158
We hear when the air between the sonant body and the organ of hearing suffers concussion, a vibration which spreads spherically and then forms waves and strikes upon the ears, just as the water in a reservoir forms wavy circles when a stone is thrown into it. Sleep is caused, they say, by the slackening of the tension in our senses, which affects the ruling part of the soul. They consider that the passions are caused by the variations of the vital breath.
1.158
Semen is by them defined as that which is capable of generating offspring like the parent. And the human semen which is emitted by a human parent in a moist vehicle is mingled with parts of the soul, blended in the same ratio in which they are present in the parent.
1.159
Chrysippus in the second book of his Physics declares it to be in substance identical with vital breath or spirit. This, he thinks, can be seen from the seeds cast into the earth, which, if kept till they are old, do not germinate, plainly because their fertility has evaporated. Sphaerus and his followers also maintain that semen derives its origin from the whole of the body; at all events every part of the body can be reproduced from it. That of the female is according to them sterile, being, as Sphaerus says, without tension, scanty, and watery. By ruling part of the soul is meant that which is most truly soul proper, in which arise presentations and impulses and from which issues rational speech. And it has its seat in the heart.
