and that of _Hyperoodon_, whence it has been extracted for commercial purposes, is said to offer no differences of importance from the spermaceti of the {364} Sperm Whale. Spermaceti as a drug appears to have been first mentioned in the pharmacopoeias of the famous medical school of Salerno towards the year 1100. But it was confounded with a totally distinct substance, viz. ambergris. The confusion was also made by the famous alchemist Albertus Magnus, and by the observant Archbishop of Upsala, Olaus Magnus, in his work _De gentibus septentrionalibus_. It was supposed in fact by these writers to be the liberated sperm of the Whale, hence obviously the name. Later on, the substance in question was regarded as the brain of the Cachalot, in fact as late as the middle of the eighteenth century. It was Hunter and Camper who really discovered the true nature of the substance, oil of course, in the cavities of the skull.[248] The huge skull of _Physeter_ "is perhaps the most modified from the ordinary type" of skull in the whole mammalian class. The top of the skull rises into a huge crest lying transversely, and from it slope forward two lateral crests formed from the maxillary bones; in this great basin lies the spermaceti already referred to. The skull, as in Toothed Whales generally, is exceedingly asymmetrical. The right premaxillary and the left nasal bones are much larger than their fellows; indeed the right nasal is hardly present as a separate bone. The parietal if present is fused with the supra-occipital. The jugal is large, and is not divided into two pieces as it is in the Ziphioids. The pterygoids meet below for a considerable distance, as in many Dolphins, and in the Edentata among other mammals. The symphysis of the lower jaw is very long, but the bones do not appear to be ankylosed. The length of the symphysis recalls that of the Gangetic Dolphin, _Platanista_. In the vertebral column the atlas alone is free, the remaining cervicals being fused. There are only eleven dorsal vertebrae, eight lumbars, and twenty-four caudals. The breastbone of this Whale is a roughly-triangular bone made up of three pieces. Four cartilaginous sternal ribs are attached to this bone. The scapula is remarkable for the fact that it is concave on the outer and convex on the inner surface; otherwise it is quite typically Cetacean in form. The shortness of the pectoral limb is shown by the phalangeal formula, which is as follows:--I 1, II 5, III 5, IV 4, V 3. {365} One of the reasons for the pursuit of the Sperm Whale is the desire to obtain that extremely valuable product ambergris. This substance has long been known; but its true nature was for centuries in dispute. In Dr. Johnson's _Dictionary_ (so recently as the edition of 1818!) ambergris is provided with alternative definitions; it is either the excrement of birds washed off rocks, or honeycombs that have fallen into the sea!