314 MAN --AN ADAPTIVE MECHANISM 



metabolism, diminished rate of pulse and respiration 

 and lowered temperature and blood-pressure are 

 all phenomena of diminished consciousness. (Fig. 79.) 

 That sleep only partially suspends the brain function 

 is indicated by the fact that during sleep there may 

 be a partial response to stimuli, such as is indicated 

 by the shifting of posture and by moving in response 

 to a call. It is particularly the function of the special 

 senses which is suspended ; and it is in response to 

 stimulation of the special senses, as we have shown, 

 that most of the energy of the body is expended. 

 Nevertheless, even while the function of the special 

 senses is suspended, there may continue in the brain a 

 symbolic train of action in the form of word pictures 

 or dreams which, if sleep be light, are recorded on the 

 feeble consciousness of the sleeper and may be recalled 

 on awakening. The subconscious memory of some 

 dominating experience of the day may break through 

 light sleep and cause a muscular response. 



That the maintenance of consciousness requires a 

 transformation of energy by the kinetic system is 

 evidenced by the histologic changes produced by pro- 

 longed continuous loss of sleep in the organs of the 

 kinetic system of rabbits, and in the fact that these 

 lesions can be restored only during sleep ; during un- 

 consciousness produced by nitrous oxid anesthesia ; or 

 to some extent, when consciousness is depressed by 

 morphia. Our experiments indicate that the lesions 

 of the kinetic system produced by emotion, by exertion, 

 by infection, like the lesions due to prolonged con- 

 sciousness, are repaired only during sleep. During 

 sleep, activating stimuli are apparently grounded. 



