4 6 



ELEMENTARY PHYSIOLOGY 



If we steep a piece of beef for a very long time in cold water, a 

 large proportion of the blood oozes out and tinges the water, 

 leaving the flesh or muscle of a pale whitish colour. We notice 

 also that it is composed si fibres. A large number of these mus- 

 cular fibres, arranged side by side, and bound together by a skin 

 or membrane, form a muscle ; and the various muscles of the 



body make up the muscular 

 system. 



There are two kinds of 

 muscles, voluntary and in- 

 voluntary. The former, 

 being under the control of 

 the will; are those which 

 give us the power of volun- 

 tary motion and of loco- 

 motion ; and these form the 

 great bulk of the muscular 

 system. The latter kind are 

 to be found distributed in 

 the substance of various in- 

 ternal organs, and in the 

 walls of blood-vessels ; and 

 are concerned in producing 

 those movements over which 

 the will has no control, such 

 as the beating of the heart, 

 and the motions of the sto- 

 mach and intestines. Both 

 voluntary and involuntary 

 muscles are composed of 

 fibres, but there is a distinct 

 difference in the form of the 

 fibres, as will be shown pre- 

 sently. 



Most of the voluntary 

 muscles are connected with 

 bones at one or both ends, 

 and every fibre composing 

 them has the power, under 

 the influence of the will, of 

 contracting in length. One end of such a muscle is generally fas- 

 tened by means of a tendon to a fixed bone, and the other end to 

 the bone to be moved ; so that when the muscular fibres contract, 

 the whole muscle shortens, becoming consequently thicker in the 

 middle, and causing one of the bones to be moved. 



Fig. 49. Front View of the Muscles of 

 the Trunk. 



