On Sleep

At the end of a long day at work, I feel 
as if I could fall asleep on my feet, drop 
like a rock on the couch or plant my face 
on my dinner plate. How much more 
for those who are the third shift, the ones 
who pull all-nighters—nurses, road construction 
workers, practically everyone in a service position? 
Sure, now we know that certain animals can go 
for long periods of time without sleep. Has anyone 
asked if they are therefore perennially exhausted, 
and what they do to alleviate that? Dolphins
and great frigatebirds experience 
unihemispheric sleep—which means half 
their brain stays awake at all times while 
the other rests, so they are never
completely unconscious. The common
swift, only seven inches long, has a small, 
pale bib under its chin and a wingspan of nearly
sixteen inches. As the days shorten, it begins
its intercontinental migration, staying airborne 
for ten whole months without stopping. 
The half of my brain that's still awake can't
even comprehend how that's possible. 
And when I'm really tired, it's like half my brain 
really wants to fall asleep but the other half 
is still cycling furiously from one thought to another, 
worrying about how I'm going to meet my deadlines 
or when I'll ever finish paying off my mortgage;
worrying about my working daughters—if they're 
happy, have enough sleep, have enough to eat.