Of Limbs, Wings and Fins

Abstract

Muscles are the engines of life, necessary for all needs of mechanical actuation of limbs, wings, fins, and any animal body parts. All animals, from invertebrates to the highest vertebrates, have developed for this function a highly specialised fibrous material, characterised by a complex molecular structure, capable of performing contraction and relaxation movements with high rapidity, under an electrical and chemical stimulation. The structure of muscle cells is remarkably conserved across the evolution, to the point that the elementary bricks of any muscle are identical, ranging from an beetle to an elephant. Insects are taken as example of extreme specialisation of muscular functions, and some secrets of their complex flight dynamics are discussed. In the second half of this chapter, dimensional analysis is introduced as a tool of paramount importance. This method allows to check the consistency of a set of variables, and to formulate interesting deductions about animal behaviour, even prior to performing any quantitative measurement.