Hematology is the science that investigates blood-forming tissues, blood, and diseases associated with these tissues and ’uids [1]. Blood has three essential functions: transportation (i.e., exchange of oxygen and carbon dioxide between cells and the lungs), regulation (e.g., pH and body temperature), and protection (e.g., clotting factors and antibodies against invading pathogens). The average temperature of blood is approximately 38°C (100.4°F) and it has a slightly alkaline pH of about 7.4 (a normal range is between 7.35 and 7.45). Blood constitutes about 8% of the total body weight. The average adult male has a total blood volume of 5-6 L (1.5 gal), compared to a volume of 4-5 L (1.2 gal) for adult females.