Thanks all, for your kind words.  

Well, the condensed version is that Sparky, our tuxedo cat, turned out to be diabetic.  About three weeks ago we noticed he had lost a lot of weight in a short amount of time.  We figured it was a tape worm but after a deworming the weight did not come back.  At that time he was still eating and drinking normally.  A visit to our vet's office (but not our usual doctor) ruled out feline aids and leukemia.  Then a few days later Sparky lost all appetite.  On Sunday morning, the 31st, we called for an emergency visit and were referred to the covering vet, who turned out to be a wonderful person.  (--If we ever needed to change vets, she would get my vote.)  She did an exam, ran some blood tests and diagnosed Sparky as being in a diabetic state.  Normal blood "sugar" for felines is in the low 100's --110, 115, something like that.  Sparky's was 440.  We agreed for her to put him on iv fluids (and insulin) to (a) bring down his sugar level and (b) to stablize him to the point of eating on his own.  

By Monday morning Sparky's blood sugar had only dropped to the 300's and he was still not eating or drinking.  Even if the vet had been able to stablize his condition (we're not sure she could have done so), this poor cat's life would have been miserable.  This guy would be the first one out the door every morning and the last one to come in at night.  --And there were nights when he did not come home at all!  There was no way we could have retrained him to abide by the regulations of a diabetic lifestyle.  His quality of life would have been crap, if you'll pardon my french.  We won't even go into the expense of such a regimine.  

And so we decided to let him go on to heaven.  He's buried in the far corner of the back yard, under a nice shade tree.  Sparky was 6 years old and enjoyed life to the fullest.  He was always our "problem child", wandering the farthest, eating god-knows-what, sometimes disappearing for days on end.  We were always fearful that he would either get run over by a car (part of our farm borders a busy highway) or killed by a coyote.  At least now we always know where he is!