MAURY ON SLEEP AND DREAMS. 383 



which most clearly expounds the relation of these phe- 

 nomena to the acts and changes of the waking state 

 a connexion which, however perplexed to our reason by 

 the question of personal consciousness, will be found 

 more intimate the closer we look into it. As in the 

 series of waking thoughts, sudden changes are often 

 made by impressions from without, so, as regards sleep 

 and dreams, we may presume that the breaches which 

 occur in their continuity depend on causes external 

 to the brain itself, though, from the nature of the case, 

 less open to observation. The links may escape ob- 

 servation, but we cannot hesitate in bringing these 

 phenomena under the general law of continuity, so 

 universal throughout nature, organic or inorganic, 

 living or lifeless. This law, scarcely recognised in 

 philosophy or science before the time of Leibnitz, is 

 now receiving confirmation from every new discovery, 

 and becoming the interpreter of endless phenomena 

 hitherto unexplained. Leibnitz himself applies it to 

 the question of the suspension of thinking in sleep ; 

 deeming it impossible, on this consideration, that such 

 entire suspension should ever really occur. 



We shall speak more explicitly hereafter on the 

 physiology of sleep as regards the physical changes 

 concerned in producing or modifying it. But there are 

 various other facts, natural or abnormal, belonging to 

 the physiology of this function of life, which require 

 previous notice : some of them indeed so strangely 

 anomalous as to have furnished food at once to sober 

 philosophy and to the wildest dreams of credulity. We 

 may best begin with what we may call the natural 



