aspects of human physiology and assorted matters such as the greatness of Julius Caesar, outstanding people such as Hippocrates and Asclepiades, happiness and fortune. Zoology Zoology is discussed in Books VIII to XI. The encyclopedia mentions different sources of purple dye, particularly the murex snail, the highly prized source of Tyrian purple. It describes the elephant and hippopotamus in detail, as well as the value and origin of the pearl and the invention of fish farming and oyster farming. The keeping of aquariums was a popular pastime of the rich, and Pliny provides anecdotes of the problems of owners becoming too closely attached to their fish. Pliny correctly identifies the origin of amber as the fossilised resin of pine trees. Evidence cited includes the fact that some samples exhibit encapsulated insects, a feature readily explained by the presence of a viscous resin. Pliny refers to the way in which it exerts a charge when rubbed, a property well known to Theophrastus. He devotes considerable space to bees, which he admires for their industry, organisation, and honey, discussing the significance of the queen bee and the use of smoke by beekeepers at the hive to collect honeycomb. He praises the song of the nightingale. Botany Botany is handled in Books XII to XVIII, with Theophrastus as one of Pliny's sources. The manufacture of papyrus and the various grades of papyrus available to Romans are described. Different types of trees and the properties of their wood are explained in Books XII to XIII. The vine, viticulture and varieties of grape are discussed in Book XIV, while Book XV covers the olive tree in detail, followed by other trees including the apple and pear, fig, cherry, myrtle and laurel, among others. Pliny gives special attention to spices, such as pepper, ginger, and cane sugar. He mentions different varieties of pepper, whose values are comparable with that of gold and silver, while sugar is noted only for its medicinal value. He is critical of perfumes: "Perfumes are the most pointless of luxuries, for pearls and jewels are at least passed on to one's heirs, and clothes last for a time, but perfumes lose their fragrance and perish as soon as they are used." He gives a summary of their ingredients, such as attar of roses, which he says is the most widely used base. Other substances added include myrrh, cinnamon, and balsam gum. Drugs,