Sperm whale . Myoglobin, which stores oxygen in muscle tissue, is much more abundant than in terrestrial animals. The blood has a high density of red blood cells, which contain oxygen-carrying haemoglobin. The oxygenated blood can be directed towards only the brain and other essential organs when oxygen levels deplete. The spermaceti organ may also play a role by adjusting buoyancy (see below). The arterial retia mirabilia are extraordinarily well-developed. The complex arterial retia mirabilia of the sperm whale are more extensive and larger than those of any other cetacean. Atop the whale's skull is positioned a large complex of organs filled
The Brain of Morbius the ruins. Morbius attacks the Doctor, but is knocked out by Solon's tranquilliser. As they carry the creature back to the castle, the Doctor tells Solon that Morbius's brain will be detached and returned to the Time Lords. The body of the dead Sister is brought back to Maren. Ohica reports that witnesses saw a creature and then the Doctor and Solon hunting for it. Maren realises that Solon has succeeded in his experiments and resurrected their ancient enemy. But Maren is too old and weak to leave the shrine, and she gives Ohica permission to lead the Sisters to