Sprinkle gelatin over the vinegar in a small saucepan.
Dice cucumber and liquify in a blender or grate by hand.
Soften cream cheese with a fork; add cucumber, and mix together well.
Place softened gelatin over low heat and stir constantly until gelatin dissolves, about 3-5 minutes.
Remove from heat and add to the cream cheese.
Whip egg whites until fluffy and fold into mixture.
Add salt and pepper.
To garnish, place very thin cucumber slices in the bottom of a large mold or 6 individual ones; then pour in a small amount of additional dissolved gelatin and allow to set before pouring in the mixture.
Chill 3-4 hours before unmolding.
This is a very pretty and refreshing salad.