Mr Yeltsin, who had his finest hour atop a tank resisting a hardline coup attempt in 1991, thrives on situations where he has to fight. He is not a man to let mere illness get him down.
And we can only hope that the relative glasnost of post-Communist Russia is our guarantee that when we are told officially he has "acute laryngotracheitis", he really does have a sore throat or something similiar and not some life- threatening illness. Leonid Brezhnev, after all, was still described as having a cold when he lay on his death bed.
Still, since he underwent a heart bypass operation in November 1996, the Russian President's health has been a cause for worry throughout the world. Under pressure from the press, Mr Yeltsin has had to learn to be more honest about it.
He first disappeared into hospital without any explanation after Mikhail Gorbachev, then leader of the Soviet Union, sacked him from the ruling Communist Party Politburo in 1987. In retrospect, it seems this shock may have marked the start of his heart problems. But Mr Gorbachev unwittingly helped his career by making him a martyr and, when he came out of hospital, he went on to become the most popular opposition politician in Russia. He was elected Russian President in June 1991 and took over from Mr Gorbachev as Kremlin leader when the Soviet Union collapsed later that year.
The heavy-drinking Yeltsin tried to keep fit by playing tennis. But heart problems continued to dog him, bursting out into the open just after he had won a second term as Russian President in the summer of 1996. At first, as yesterday, aides said he had a sore throat; but his continued absence from public view so soon after he had won a stunning election victory against all the odds looked suspicious. Soon ,they were forced to admit that the blood supply to his heart was deficient.
Mr Yelsin then came clean to the Russian people himself, saying the life of an invalid was not for him and he had decided to undergo a heart bypass, a relatively routine operation in the West, so that he could return to politics with renewed vigour.
The operation, carried out by a team of Russian doctors with the Texas heart specialist Michael De Bakey hovering in the background, was described in surprising detail to the press. Dr De Bakey declared Mr Yeltsin's operation a complete success, saying it would give him 10 more years of life if he controlled his drinking and resisted his favourite fatty foods, such as Russian sausage. But unfortunately, straight after the operation, the Kremlin leader caught a cold and fell ill with pneumonia in the freezing January of 1997. His return to politics was delayed until last spring.
Since then he has been active both on the international stage and at home. He takes more holidays than a younger leader might do - his fishing and skiing trips are televised to assure us of his continuing robustness. He is clearly ageing, and yet, though his enemies say it, he is not like Brezhnev, just a corpse being propped up for show. He is still mentally alert and, when the spadework has been done by his underlings, he is still the man who takes the ultimate decisions.
BORIS AND THE BOTTLE
Does Boris Yeltsin drink? Is the Pope a Catholic? Before he underwent heart surgery in November 1996, it would hardly have occurred to vodka- loving Russians to doubt that their President drank. They would not have respected him if he had abstained. Does Boris Yeltsin drink now? There is no real evidence of any hard drinking nowadays.
DADDY'S LITTLE GIRL
Whether Mr Yeltsin retires with dignity or tries to extend what his enemies call his "Tsar-like rule" into the next century may depend on the advice he receives from his eldest daughter, Tatyana Dyachenko. He trusts her so much that last year he made her an official presidential aide, responsible for his image. Tatyana, 38, a former rocket scientist, apparently plays a stronger role behind the throne than Mr Yeltsin's wife, Naina, who is said to like baking cakes and looking after the grandchildren.
The great constitutional question of the moment is not who would replace Mr Yeltsin in the immediate aftermath of his death, but rather, could Mr Yeltsin stand for a third term as President? Recently he commented that the best guarantee of good relations between Moscow and Kiev was not to change the presidents of Russia and Ukraine.