Vesiga is marrow taken from the spinal cord of the sturgeon fish (the European sturgeon, not North American ones also called by the same name.) It was dried whole and long, so that it looked like an opaque white ribbon, and was gelatinous. It was used in upper class Russian food, and was considered a delicacy. It was very expensive. Now it is seldom if ever used and rather difficult to find, if at all.
Vesiga was served as part of the last meal on the Titanic, used as a garnish on the bowls of Consommé Olga.