These include the feelings which arise in connection with the processes of digestion, respiration, and circulation, and the condition of various organs according to their state of nutrition, etc.

During our waking life these organic feelings coalesce for the most part, forming as the "vital sense" an obscure background for our clear discriminative consciousness, and only come forward into this region when very exceptional in character, as when respiration or digestion is impeded, or when we make a special effort of attention to single them out.[85] When we are asleep, however, and the avenues of external perception are closed, they assume greater prominence and distinctness.

The centres, no longer called upon to react on stimuli coming from without the organism, are free to react on stimuli coming from its hidden recesses.

So important a part, indeed, do these organic feelings take in the dream-drama, that some writers are disposed to regard them as the great, if not the exclusive, cause of dreams.

Thus, Schopenhauer held that the excitants of dreams are impressions received from the internal regions of the organism through the sympathetic nervous system.[86] It is hardly necessary, perhaps, to give many illustrations of the effect of such organic sensations on our dreams.