So, summing up: the brain was the seat of the rational soul. It received vital spirit from the heart, mixed into the 'sanguine' humour (blood). The brain then separates the animal spirit out and stores it in the ventricles, distributing it throughout the body via the nerves. This fluid travelled, via the nerves, to muscles and organs to control all the bodies activities. The rational soul was considered responsible for imagination, reason and memory.

 

Commentary

It seems to me that we always use the stuff we generate about the world, in trying to understand the world; as a model from which we can gain greater and greater differentiation of the things being considered. The brain works by recognising the differences between sensory data, sameness drops away by being habituated out. The ideas of proportion and ratio, similarity of nature and process in things of different level (as expressed in the macrocosm / microcosm) provide the basis for metaphor and modelling to elucidate nature and thus allowing finer and finer differentiation between things. We use the projections and constructions of our minds to feedback upon ourselves. It is geometry which provides the data of these earliest models of human being.