Note 9 — Chapter VI · THE STUDY OF NATURE. FUNDAMENTAL POSITIONS.
Oswald J. (Oswald Joseph) Reichel translation
The same hypothesis was also used to explain the origin of the soul. One part of the soul was believed to be transmitted to the young in the seed.9 From the part so transmitted there arises, by development within the womb, first the soul of a plant; and this becomes the soul of a living creature after birth by the action of the outer air.10 This view led to the further hypothesis that the seat of the soul must be in the breast, not in the brain; since not only breath and warm blood, but also the voice, the immediate expression of thought, comes from the breast.11