1. Spermaceti is a waxy, tasteless, odorless substance separated from the oil of sperm whales that is used in cosmetics, ointments, and good-quality candles.

2. Whaling declined after 1850, when mineral oil and gas replaced spermaceti oil as a source of light.

3. Their heads also hold large quantities of a substance called spermaceti.

4. The toothed whale has a large square head with a cavity that contains the so - called spermaceti.

5. Whalers once believed that the oily fluid was sperm, but scientists still do not understand the function of spermaceti.

6. Photo Gallery: Whales Sperm whales'heads are filled with a mysterious substance called spermaceti.

7. Sperm whales' heads are filled with a mysterious substance called spermaceti .

8. Sperm whales' heads are filled with a mysterious substance called spermaceti. Scientists have yet to understand its function, but believe it may help the animal regulate its buoyancy.