Blood is the vital animating fluid that courses through our bodies, sustaining us by performing a plethora of roles. A functionally similar fluid exists in invertebrates while the sap of plants can carry out comparable duties. The different functions of blood, its constituents, physiological role and colour are, amongst other things, all explored in this book. The nature of blood in various vertebrates such as camels and frogs; invertebrates – including crustaceans and molluscs – and insects are also looked at. Pathological blood conditions such as porphyria, haemophilia and sickle cell disease are alluded to, as are the uses of blood products and the age-old practices of bloodletting, leeching and cupping.

Also discussed are the myths and beliefs, together with the religious and linguistic connotations surrounding blood. In addition, hematophagous behaviour, vampirism and heart transplants, together with some of its implications, are also considered. Finally, given the ever-increasing need for donated blood, the subject of blood substitutes is examined at length.

There are roughly 100,000 miles of blood vessels in the human body, blood accounting for nearly 7 percent of our body weight. Red blood cells –more numerous in men compared to women – live for almost 120 days, being replaced at the staggering rate of between 2 to 3 million erythrocytes per second! It is truly amazing that our tiny, bean-shaped kidneys – a mere 4 inches long, 2.5 inches wide and weighing a paltry 5 ounces each – filter an astonishing 50 gallons of blood daily.