The influx is imprinted on the native" makes me think Morin alludes about ether rather than air.

That would be perfectly consistent with his thinking.

That being said, there are close connections between the air we breathe and the higher mind (identified with the being), so that might be the reason why, in the end (if this wasn't taken for granted since a long time ago), someone saw "the first breath" the Infant takes as the birth astrologicaly speaking.
Conjecture.