The changes in metabolic activity associated with endothermy and the change from gill to lung respiration has led to changes in vertebrate circulatory systems. Veins between two capillary networks are ...

The circulatory system is the heart and all the blood vessels in the body which carry cells and substances to all its parts. The heart is a large muscular organ which pumps blood to the lungs and ...

George Washington died after his physician treated his sore throat with bloodletting, but don't let that stop you from ...