325 



the body rests on the articulation of the foot with the leg. In standing 

 on tip-toe, the muscles of the calf of the leg become prodigiously fatigued, 

 though their action is assisted by the most favourable lever*, adapted to 

 the greatest resistance which Nature can oppose to herself. Lastly, the 

 foot moves as a lever of the third kind, when we bend it on the leg. 



CXLVIII. What is called the fixed point, in the action of muscular 

 organs, does not always deserve that name. Thus, though it may bo said, 

 very correctly, that the greatest part of the muscles of the thigh have 

 their fixed points in the bones of the pelvis, to which their upper extre- 

 mity is attached, and though they move the femur on th. 1 ilia which are 

 less moveable ; when the thigh is fixed by the action of other muscles, 

 these move the pelvis on the thigh, and that which was the fix?d point, 

 becomes moveable. The same applies to the other muscles of the body, 

 so that the fixed point is merely that which, generally, is a fulcrum to 

 the muscular action. This necessary fixed state of one of the bones, to 

 which is attached one of the extremities of a muscle which we wish to 

 contract, renders it necessary, in performing the slightest motion, thai 

 several muscles should be called into action, which implies a very com- 

 plicated mechanism. Nothing is easier to prove. Suppose a man stretched 

 on the ground or lying on his back; if he wish to raise his head, it will 

 be necessary that this chest become the fixed point of action of thesterno 

 cleido mastoidei, whose office it is to perform this motion. Now, in order 

 that the pieces forming this osseous structure may remain motionless, it 

 will be required, that the chest should be fixed by the action of the abdo- 

 minal muscles which, on the other hand, have their fixed point in the 

 pelvis that is itself fixed in its place, by the contraction of the glutaei 

 muscles. It was on this principle that Winslovv first suggested, that in 

 reducing a hernia, the patient should be laid in an horizontal posture^, 

 with injunctions not to raise his head, that the abdominal muscles being 

 relaxed, their different openings might yield more easily to the reduction 

 of the parts. 



In case the two opposite points to which the extremities of a muscle 

 are attached, are equally moveable, they approach towards each other, 

 during the contraction of the muscle, by making them move through 

 equal spaces. These spaces would not be equal, if the mobility were 

 different. Each muscle has its antagonist, that is, another muscle whose 

 action is directly opposed to it. Thus, the flexors balance the action of 

 the extensors, the adductors perform motions different from those of the 

 abductors. When two antagonizing muscles of equal power act, at the 

 same time, on a part equally moveable, in every direction on the oppo- 

 site powers, neutralize each other, and the part remains motionless. If 

 there is a difference in the degree of contraction, the part is directed to- 

 wards the muscle whose contraction is the most powerful : if the opposi- 

 tion is not direct, the part follows a middle direction, between the two 

 powers which move it. Thus, the rectus externus muscle of the eye is 

 not antagonized by the rectus inferior ; hence when these two muscles 

 come to contract, at the same time, the eye is not carried downward or 

 outward, but at once downward and outward ; it is then said to mote in 



* Of levers with arms of unequal length, that of the second kind is the most favoura^ 

 ble, since the arm of the power is uniformly longer than that of the resistance. Cop- 

 land. 



