wichita.edu
…same nature as that which lies in the spermatic production of the egg, necessarily, though applied externally, performs the same function as innate warmth, whether inherent in a bird, a human, or elemental heat, as long as it has acquired a temperament suitable for producing the effect. For that vital internal heat, as the craftsman of its own body, is…
https://www.wichita.edu/academics/fairmount_las/geology/wparcell/Kircher/IterII/indexII.php