Body fluid is extracellular fluid which has one name in animals with open vasculature
but has two or three names in animals with closed vasculature. In other words，in
vertebrata as the body fluid is separated by the blood capillary and lymph capillary
walls，it is termed as blood，tissue fluid and lymph fluid according to the site concerned. Therefore，although there is quantitative difference among the components of these three body fluids， there is no qualitative difference. Further，similar quantitative differences can also be noted in venous blood and lymph fluid in the various parts of the body.