speak of the heavy, dull sleep which, without apparent dreams, results from plethora, accompanies an over-loaded stomach, is the result of over-exhaustion, or occasionally supervenes after protracted vigils, but of the sound sleep enjoyed by the working-classes when in health, or by vigorous children.
The most interesting question is, Can a theory of dreams be constructed which will explain them upon natural principles, without either the assumption of materialism, or an idealism akin to superstition? It is to be understood that no phenomena can be explained at the last analysis; but a theory which will, without violence, show the facts to be in harmony with natural laws, or so bring them within the range of things natural that they are seen to belong to a general class, and to the relations of antecedents and consequents, is an explanation. For example, electricity defies final analysis; but its modes of action are known, and even the greatest of mysteries, the form of induction which now surprises the world in the recently invented process of telegraphing from moving trains, is as susceptible of this kind of explanation as the action of steam in propelling a train.
We begin with analogies, and find these in the effect of drugs, such as opium, alcohol, nitrous-oxid gas, hashish, etc. De Quincey describes all the experiences of dreams, both before and after he entered into a state of sleep, as resulting from the use of opium; and the peculiar sleep produced by that drug is attended by dreams marked by all the characteristics of those which occur in natural sleep. The effect of alcohol in setting up a dream state in the mind while the senses are not locked in sleep is, unfortunately, too well known. When a certain point is reached in intoxication the will is weakened, the auto-
