CHAPTER II 



MECHANICS OF LOCOMOTOR APPARATUS 



CONTENTS. 1. General remarks on the structure of the bones and their 

 articulations. 2. Form, attachments, and mechanics of muscles in relation to 

 bones. 3. Line and centre of gravity of the body in different postures. 

 4. Mechanics of equilibration in different postures. 5. Movements of the body 

 in walking. 6. Movements of the body in running. 7. Movements of the body 

 in swimming. Bibliography. 



THE muscles are the active organs the bones, cartilages, ligaments, 

 etc., which build up the skeleton to which the muscles are attached 

 represent the passive organs of a highly complex system to which 

 Marey correctly applied the term animal machine. In industrial 

 machines also it is usual to distinguish between the active parts 

 which are the seat of the production or development of the energy 

 destined to be transformed into useful work, and the passive parts 

 which transmit it, and which consist as in the animal machine 

 of levers, pulleys, inclined planes, pumps, etc. 



Our principal task in this chapter will be to study the complex 

 motor apparatus, consisting of an elaborate system of skeletal 

 muscles, on the co-ordinated action of which depend the loco- 

 motor movements, i.e. the different forms of displacement of the 

 body as a whole. These are distinguished from the partial move- 

 ments or displacements of the limbs, by which the relations of the 

 different mobile parts of the body are altered. In the former the 

 base of the body is displaced ; in the latter it may remain immobile. 



In the study of these motor functions the physiologist's task is 

 to a large extent linked with that of the anatomist. It is, in fact, 

 impossible to form a clear conception of the mechanism of a move- 

 ment carried out by the active participation of many different 

 muscles without first knowing the points of attachment of each 

 muscle as well as the form and articulation of the bones, which act 

 passively as the levers. But while the anatomist is occupied more 

 particularly with the mechanical action of each muscular unit, the 

 physiologist supplements this by the synthetic study of the co- 

 ordination of the various muscular forces which combine in the 

 accomplishment of each separate motor act. 



96 



