The function of the physiological processes in brain and nervous system is to keep up that process of "enjoyment" which is the contemplating of such sections. The physiological conditions which generate some sensa would therefore be somewhere in the mass of somatic sensa. Now, visual and auditory sensa are not in the least like somatic sensa. It is held that all sensations have originative and productive conditions, even though the sensation is "hallucinatory". Whether all sensations have transmissive conditions is uncertain. It is certain that most of them have, and probably the difference between those which obviously do, and those which apparently do not, is a difference of degree rather than one of kind. The inside of the body is quite dark; so that, whatever be the internal conditions which originate the visual experiences of dreams, they must be extremely different from the luminous events which are the originative conditions of normal visual sensations.