In "Dr. Heidegger's Experiment," what happens to the vase?
You asked two questions. According to enotes regulations, I have had to cut this down to one as you are only allowed to ask one question. The vase containing the elixir of life which Dr. Heidegger's guests have so eagerly quaffed meets a sad end as the guests, in their first flush of youth once more, argue and fight over the attention of the Widow Wycherley:
Still keeping hold of the fair prize, they grappled fiercely at one another's throats. As they struggled to and fro, the table was overturned, and the vase dashed into a thousand fragments. The precious Water of Youth flowed into a bright stream across the floor, moistening the wings of a butterfly, which, grown old in the decline of summer, had alighted their to die. The insect fluttered lightly through the chamber, and settled on the snowy head of Dr. Heidegger.
The symbolic overturning of the table and the shattering of the vase containing the Water of Youth seems to suggest and also highlight how the four guests have again wasted their youth in exactly the same way as they wasted it the first time. Even though they have had a "second chance," they have not learnt anything from age. This highlights the message of the story as summed up by Dr. Heidegger, whose more mature and wiser approach to ageing is summed up in his rejection of the Water of Youth.