98 INFLUENCE OF NERVES 



other. That some conception may be formed of 

 their arrangement and distribution, the superficial 

 layer, or that which appears immediately on re- 

 moving the skin, is represented in the annexed 

 woodcut, taken from a little volume entitled " The 

 Physician," published by the Society for the Diffu- 

 sion of Useful Knowledge. To understand tl e uses 

 of the various muscles, the reader has only to bear 

 in mind that the object of muscular contraction is 

 simply to bring the two ends of the muscle and the 

 parts to which they are attached nearer to each 

 other, the more moveable being always carried to- 

 wards the more fixed point. Thus, when the sterna- 

 mastoid muscle f g contracts, its extremities approx- 

 imate, and the head being the moveable point, it is 

 pulled down and turned to one side. This may be 

 easily seen in the living subject, the muscle being 

 not less conspicuous than beautiful in its outline. 

 Again, when the powerful rectus or straight muscle 

 b on the front of the thigh contracts with force, as 

 in the act of kicking, its lower end attached to the 

 knee-pan and leg tends to approximate to the upper 

 or more fixed point, and pulls the leg strongly for- 

 wards. This occurs in walking. But when the 

 sartorius or tailors' muscle c is put in action, its 

 course being oblique, the movement of the leg is no 

 longer in the straight line, but in a cross direction 

 like that in which tailors sit, and hence the name 

 sartorius. 



Another variety of effect occurs when, as in the 

 rectus, or straight muscle of the belly i i, sometimes 

 one end and sometimes both are the fixed points. 

 When the lower end is fixed, the muscle bends the 

 body forward and pulls down the bones of the chest. 

 When, as more rarely happens, the lower end is the 

 moveable point, the effect is to bring forward and 

 raise the pelvis and inferior extremities ; and when 

 both ends are rendered immoveable, the contraction 

 of the muscle tends to compress and diminish the 



