Preheat oven to 250° F.
In a medium bowl with mixer at high speed, beat egg whites and cream of tartar until soft peaks form.
Gradually sprinkle in sugar, 2 T. at a time, beating after each addition for about 2 mins. or until sugar is completely dissolved., about 15 mins. total. To test, rub meringue betweeen fingers; if grainy, continue beating.
Add vanilla, beating at high speed until mixture stands in stiff, glossy peaks.
Fill a large Ziploc baggie with meringue. Snip one corner of the bag so that opening measures about ½" across; alternatively use a frosting bag without a piping tip.
Onto a large cookie sheet lined with parchment paper, pipe mixture into strips about 3" long, and add a dollop at each end to shape the end of the "bone."
Bake 45 mins. until meringues are crisp; they should not brown. Turn off oven, let meringues stand in oven at least 2 hrs. longer, or overnight to dry.
Carefully peel bones from parchment paper, and store at room temperature.
Makes about 36 bones.