830. THAT THERE ARE SPIRITS WHO RELATE TO THE GREAT VENTRICLES OF THE CEREBRUM It is known that the great ventricles of the cerebrum are the places into which flow the serosities from the interstices between the fibers and from elsewhere, so that they are, as it were, the urinary bladders of the brain where the serum or lymph is mixed with the [animal] spirit, and from which, in their order, the [animal] spirit and better parts are again separated.