He goes through the whole multiplicity of possible causes, drawing up a list of all the partial determinisms that have been suggested regarding dementia: a hardening of the fibres, a dryness of the brain as in the theories of Bonet, a softness or serosity of the encephalum as in Hildanus, the use of henbane, stramonium, opium and saffron (according to the observations of Rey, Bautain, and Bar re), the presence of a tumour, of encephalitic worms, and malformations of the skull.