Red and Blue Blood.~--While in the arteries the blood is of a bright red color; but while it is passing through the capillaries the color changes to a bluish red or purple color.

The red blood is called _arterial blood_, because it is found in the arteries.

The purple blood is called _venous blood_, because it is found in the veins.

The loss of oxygen in the corpuscles causes the change of color.
~10.

Change of Blood in the Lungs.~--Exactly the opposite change occurs in the blood when it passes through the lungs.