This section is from the book "The Human Body: An Elementary Text-Book Of Anatomy, Physiology, And Hygiene", by H. Newell Martin. Also available from Amazon: The Human Body.
The distinctive properties of muscle are everywhere the same ; it has the power of contracting; but the uses of different muscles are very varied by reason of the different parts to which they are attached. Some are muscles of respiration, others of swallowing ; some bend joints and are called flexors, others straighten them and are called extensors, and so on. The determination of the exact use of any particular muscle is known as its special physiology, as distinguished from its general physiology, or properties as a muscle, without reference to its use as a muscle in a particular place. We may here consider the special physiology of the muscles concerned in standing and walking.