THE CHEMISTRY OF SLEEP. 235 



"afferent" impulses from without, are still fulfilled. The nerves 

 which govern the muscles of the iris must be so affected by the 

 imagination (or by some unknown agent acting only during sleep) 

 as to contract, as if light still fell upon them. This does not 

 seem, however, to concur with the generally accepted view that 

 the muscular fibers that control the iris are involuntary. Until 

 these extraordinary phenomena are understood, we shall doubt- 

 less not arrive at a complete theory of sleep. The study of dream 

 phenomena will in this connection (in spite of Prof. Foster) con- 

 stitute an essential aid. 



The collateral phenomena accompanying and related to sleep, 

 though not confined to natural sleep or, for that matter, to any 

 kind of sleep that suspends the bodily functions are several. 

 Dreams are the most important and significant ; but we can give 

 space only to some partial consideration of the two species of 

 dreams namely, sleeping and waking dreams. Our encyclopaedia 

 of 1778 discusses several views then entertained regarding dreams ; 

 among them the curious one presented by the famous Richard 

 Baxter, in his book on the Immateriality of the Human Soul, to 

 the effect that dreams are due " to the action of some immaterial 

 beings upon our souls." Objection is made to this on the ground 

 that the existence of such immaterial beings is incapable of proof. 

 This spiritualistic side of the discussion we must omit. 



The most important suggestion regarding dreams made by 

 this encyclopedist of 1778 is that mania and hypochondriasis are 

 conditions under which the subjects dream while otherwise wide 

 awake. That this is so appears incontrovertible, and we learn 

 thence that the dream state does not necessarily arise from sleep, 

 of the body at least. Mania may probably be defined as a dreamy 

 slumber of the mind, without the participation of the body. Simi- 

 lar conditions are abundantly brought on temporarily by the 

 abuse of certain powerful agents that destroy the rule of the will 

 and reason over the mental functions, leaving the individual to 

 be swayed altogether by the animal emotions. When the mania is 

 chronic, accounts agree that in time the demoralization becomes, 

 in most cases, so complete as to really give color to the views in 

 ancient books, including our scriptural writings (and, moreover, 

 in the works of some modern writers), that many if not most 

 maniacs are under demoniacal possession. Waking dreams and 

 reveries are known also to attack many persons in whose minds 

 imagination is a predominating element. And even such as do 

 not belong to this class, may become, when under the influence of 

 great distress, fear, privation, or hardship, subject to such waking 

 visions. Starvation or thirst, or both, have often produced the 

 most remarkable illusions. One interesting example may be cited 

 which is historical. It is found in the Journal of Strain's Ex- 



