THE BBASON WHY. 247 



HP I !..- .!! -. !!! !! . . , . . ,^| 



1 Yet a little sleep, & little slumber, a little folding of the hands to sleep : So 

 shall thy poverty come as one that travelleth ; and thy want <*s an 

 armed man." PBOVEBBS xxr. 



the sleeper. He gives a sudden start, every muscle is tightened in an instant, 

 up goes the head, the eyes open, the ears listen, until a feeling of security and 

 composure returns ; the sleep again deepens, the nervous connection is again 

 withdrawn, and then down drops the head as before. 



1020. Why do we dream ? 



Dreams appear to arise from the excitement of the brain 

 during those hours when its connection with the other parts of 

 the living organism is suspended. For instance : a man dreams 

 that he is pursued by a furious animal, and the mind passes 

 through all the excitement of flying from danger j but the 

 connection between the moving power, and the machinery of motion 

 being suspended, no motion takes place. The same impressions 

 upon the brain, when the nerves were " strung" to the muscles, 

 would have caused a rapid flight, and a vigorous effort to escape 

 from the apprehended danger. 



1021. Why do suppers, when indigestible substances are 

 eaten, produce dreaming ? 



Probably because, as the digestive organs are oppressed, and 

 those parts of the nervous system which stimulate the organs of 

 digestion are excited by excessive action, those portions of the brain 

 which are not immediately employed by the digestive process are 

 disturbed by that sympathy which is observed to pievail between 

 the relative parts and functions of the body. 



1022. Why do we yawn ? 



Because, as we become weary, the nervous impulses which direct 

 the respiratory movements are enfeebled. It has been said that 

 those movements are involuntary, and that the parts engaged in 

 producing them are not subject to fatigue. But the operation of 

 breathing is, to some extent, voluntary, though when we cease to 

 direct it voluntarily, it is involuntarily continued by organs which 

 know no fatigue. 



When, therefore, we feel weary still controuling our breathing 

 in our efforts to move or to speak there frequently arrives a period 

 when, for a few seconds, the respiratory process is suspended. It 

 seems to be the point at which the voluntary nerves of respiration 

 are about to deliver their office over to the involuntary nerves ; but 



