The extensive range of movement of the avian glenohumeral joint makes functional interpretation of any muscle that crosses the joint difficult. Multiple functional roles for the M. coracobrachialis posterior (CBP), an architecturally complex muscle that lies deep to the M. pectoralis, have been assigned on the basis of its anatomical position. The mechanical properties, neuromotor pattern during flight and the biochemical properties of the CBP in pigeons (Columba livia) were studied by in situ length/active tension and length/passive tension measurements, in vivo electromyography and muscle histochemistry. The action of the muscle was studied directly through in situ stimulation and measurement of humeral excursion in non-reduced preparations.
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