The spermaceti organ is an organ that commonly appears in the heads of toothed whales of the family Physeteroidea, in particular the sperm whale. This organ contains a waxy liquid called spermaceti and is involved in the generation of sound. 
The spermaceti organ in sperm whales is shaped liked an elongated barrel and sits on top of the whale's melon. Historically, the liquid from this organ was used to produce sperm oil, providing the economic basis for the sperm whaling industry.
- http://www.britannica.com/EBchecked/topic/559404/spermaceti-organ Spermaceti Organ from Britannica