l^_' Tin: NKUvm s S^STKM \\i> ITS CONSKHVATION 



I- then- any scientific basis for the old teaching, "Karly 

 to bed and early to rise"? It would seem at first as 

 though sleep at one time should have as much virtue as at 

 another. Still the ancient maxim may have a certain 

 foundation. To be up early and to go "early to bed" 

 means that the use of artificial light will be reduced to a 

 minimum. It is not likely that any substitute for day- 

 light can be found which will not impose a severer tax 

 upon the eyes than does their natural form of stimula- 

 tion. Whatever tires the eyes has a widespread and de- 

 pressing influence upon the whole nervous system. Again, 

 lying abed late in the morning has the disadvantage that 

 the sleeper is likely to be affected by light and noises which 

 may deprive his rest of some of its potency for good, even 

 though they do not interrupt it. 



Neuron Theories of Sleep. We have regarded sleep as 

 a state induced indirectly by fatigue substances acting 

 upon the system and directly by the failure of an adequate 

 cerebral circulation. Other aspects of the condition may 

 be selected for emphasis. All the facts of sleep might be 

 explained by the conception of varying synaptic resistance. 

 The establishing of gaps in the motor paths would remove 

 the muscles from central control. Similar gaps anywhere 

 along t he paths which conduct impulses from the receptors 

 would cause sensory paralysis for the time. Thought, in 

 the absence of the means of present guidance from the 

 external world and deprived of the power to express itself 

 through the neuromusciilar mechanism, must be limited 

 to a rehearsal of memories and should take on the character 

 of dreaming. We should expect that a further impairment 

 of intercourse among the various regions of the cerebrum 

 must suspend even this kind of psychic activity. 



Reasoning along the lines just indicated, certain physiol- 

 ogists have pictured the passage from waking to sleeping 

 as due to the interposition of extra resistance at the 

 synapses. The idea wa- fir-t expres-cd as a literal snapping 

 of connections between the discharging and receptive 

 proce--e- of the neuron-, but this has come to seem 



