Galen talks about tension, tonos, in a physiological sense, which seems to be related to either the innate heat
of the living being, the good mixture of its humors, or the body's pneuma.
The discovery that her death was due to a loss of innate heat
sets him "on a road of scientific inquiry" and self-discovery.
Galen's views, which remained in vogue for the next millennium, represented a further evolutionary development, which stated that a 'pneuma-like substance' absorbed in the lungs reached the heart where, under influence of 'innate heat
', it converted to 'vital pneuma', which passed to all organs via the arteries.