452 NERVOUS SYSTEM. 



few seconds. A peison is awakened by a certain impres- 

 sion, which undoubtedly gives rise to a dream that seems 

 to occupy hours or days, and yet the period of time between 

 the impression and the awakening is hardly more than a few 

 seconds ; and persons will drop asleep for a very few min- 

 utes, and yet have dreams, with the most elaborate details, 

 and apparently of great length. It is unnecessary to cite 

 the numerous accounts of literary compositions of merit, the 

 working out of difficult mathematical problems in dreams, 

 etc., some of which are undoubtedly accurate. If it be true, 

 that the mind is capable of forming consecutive ideas during 

 sleep, which can hardly be doubted, there is no good reason 

 why these phenomena should not occur, and the thoughts 

 should not be remembered and noted, immediately on awak- 

 ening. In most dreams, however, the mind is hardly in a 

 normal condition, and the brain generally loses the power 

 of concentration and of accurate reasoning. We sometimes 

 commit atrocious crimes in our dreams, without appreciating 

 their enormity, and are often placed in the most absurd 

 and impossible conditions, without any idea, at the time, of 

 their extraordinary and unnatural character. This is a fact 

 sufficiently familiar to every one, and is one which does not 

 admit of satisfactory explanation. 



We have made no attempt to offer an explanation of the 

 curious psychological phenomena presented during sleep, 

 and, indeed, we know little enough of the action of the 

 mind at any time ; but we have merely given the above as 

 examples of what we may call reflex mental phenomena. 

 Somnambulism, general ansesthesia, sleep from hypnotics, 

 the so-called magnetic sleep, ecstasy, catalepsy, trance, etc., 

 are abnormal conditions, which we will only consider in so 

 far as they resemble natural sleep. 



Condition of the Brain and Nervous System during Sleep. 



As we have already seen, during sleep, the brain may be 

 in a condition of absolute repose, at least, as far as we have 



