Introduction:
The song "Pumking of Blood" by Heart is referred to as double circulation because it portrays the concept of blood circulation in the body, which involves two separate pathways - the pulmonary circulation and the systemic circulation. This arrangement allows for efficient oxygenation of blood and delivery of oxygen to all body tissues.

Pulmonary Circulation:
The first part of the double circulation system is the pulmonary circulation. In this pathway, deoxygenated blood from the body is pumped by the right side of the heart to the lungs. The blood is then oxygenated in the lungs and returns to the left side of the heart.

Systemic Circulation:
The oxygenated blood from the left side of the heart is then pumped to the rest of the body through the systemic circulation. This pathway delivers oxygen and nutrients to all body tissues. After supplying oxygen, the blood returns to the right side of the heart through the veins, ready to be pumped to the lungs for oxygenation again.

Efficiency of Double Circulation:
The double circulation system is highly efficient because it allows for separation of oxygenated and deoxygenated blood. This ensures that oxygen-rich blood is delivered to body tissues that require it, while deoxygenated blood is directed to the lungs for oxygenation.

Benefits of Double Circulation:
1. Efficient Oxygenation: Separation of the pulmonary and systemic circuits allows for efficient oxygenation of blood, ensuring that the body receives an adequate supply of oxygen.
2. Enhanced Performance: Double circulation enables animals, including humans, to have higher metabolic rates, as the oxygen demand of active tissues can be met more effectively.
3. Improved Stamina: The continuous circulation of oxygenated blood to working muscles allows for sustained activity and increased endurance.
4. Adaptation to Different Environments: The double circulation system allows animals to adapt to different environments by regulating blood flow to specific areas. For example, during exercise, blood flow is directed to the working muscles, while during rest, blood flow is reduced to conserve energy.

Conclusion:
The song "Pumking of Blood" by Heart refers to double circulation because it highlights the importance and efficiency of the two pathways involved in blood circulation. The concept of double circulation is crucial for understanding how oxygen is transported throughout the body and how the cardiovascular system supports overall health and performance.