Colonel Killigrew, Mr. Gascoigne and Mr. Medbourne are three main characters in the short story "Dr. Heidegger's Experiment" written by Nathaniel Hawthorne. They are three of Dr. Heidegger's four "venerable friends" who are volunteers for an experiment. "Venerable" would normally mean that they would be worthy of respect and honour, lived a good life with having achieved all their aims and reached everything they wanted. It would mean they had a good character and good manners.
But this is completely the opposite of what they did in former times. That is underlined by the narrator's explicit characterization, namely by saying that Dr. Heidegger's friends are "melancholy old creatures who had been unfortunate in life". This description shows that their behaviour in the past contrasts with the word "venerable" and they have a bad character in reality.
The reasons why they are so melancholy now are the consequences of their bad character traits. They failed their lives because they did not behave correctly in the past and because of a sinful way of life.
Colonel Killigrew
destroyed his life "in the persuit of sinful pleasures". In former times, he "had wasted his best years and his health substance". That means he ruined his health by drinking too much alcohol and probably having affairs with prostitutes. As a consequence, he now suffers from gout and other terrible physiological and psychological illnesses. This way of behaviour shows that Colonel Killigrew is given to risks, which means that he does not think about the consequences his actions could have and that is not very wise but careless.
Mr. Gascoigne
was a politician in former times who lost his reputation. Now he is insignificant instead of notorious, because he is not "up-to-date" in politics anymore, which means that he was probably corrupt and now suffers from the consequences.
Mr. Medbourne was a successful merchant when he was in his best years but then he lost all his properties because of an unsure speculation. That shows that he likes taking risks and does not hesitate to invest all he owns even if there is a great chance of losing it. Now Mr. Medbourne is hardly more than a beggar.
Besides, the three men were a bit aggressive and unreasonable in their youth. Colonel Killigrew's, Mr. Gascoigne's and Mr. Medbourne's condition is the reason why the three suffer from their lives and wish to be already dead. ( "(Their) greatest misfortune was it, that they were not long ago in their graves". ) Further an evidence for their age is that the three men are "white-bearded".
The three have once been lovers of the Widow Wicherly and that circumstance was the reason why they all wanted to "cut each other's throats for her sake", which means that they were in love with her and everyone wanted to be her "number one". So Colonel Killigrew, Mr. Gascoigne and Mr. Medbourne can all be described as being childish and disrespectful because they would even kill their friends in order to have the woman each for himself.
The narrator describes Colonel Killigrew, Mr. Gascoigne and Mr. Medbourne as being "a little beside themselves", which menas that hthey are certainly crazy, have a strange character and are a little bit confused, which is again the opposite of their description as being "venerable".
Then the narrator compares them to all the other old people, so they are sometimes confused about present troubles or because they are worried by unhappy memories.
Reasons why they should take part in the experiment
Dr. Heidegger wants them to take part in one of his experiments as guinea pigs and wants to convince them to drink some of the original water of the Fountain of Youth to see what may be the effect on a human being. But "they anticipate some similar nonsense, with wich he was constantly in the habit of pestering his intimates". That shows that Colonel Killigrew, Mr. Gascoigne and Mr. Medbourne are not interested in Dr. Heidegger's experiment and do not really like taking part in such a scene. It also shows that Dr. Heidegger's experiments are not very spectacular.
But they do it nevertheless, perhaps because they are his friendsand because he finally convinces them. He puts an old rose into this special liquid and soon it is young and beautiful again. But the three old men do not believe in this miracle and call it "a very pretty deception". They would rather say that a magician would be able to present them a better show.
Nina Kirstein, Verena Schäfer