Viridet distinguishes between them in accordance with the mechanism of the illness and its location: 'general vapours come into being throughout the body', 'particular vapours come into being in a particular part'; the former are the result of 'a suppressing of the free flow of animal spirits', while the latter are produced by 'a ferment in or near the nerves' or by 'a contraction of the nervous cavity, through which the animal spirits circulate'.