This section is from the book "A Manual Of Physiology", by Gerald F. Yeo. Also available from Amazon: Manual Of Physiology.
The channels which carry the blood through the body form a closed system of elastic tubes, which may be divided into three varieties: -
1. Arteries.
2. Capillaries.
3. Veins.
The arteries and veins serve merely to conduct the blood to and from the capillaries, where the essential function of the blood, viz., its chemical interchange with the tissues, is carried on.
 
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