94 THK NERVOUS SYSTEM AM) ITS CONSERVATION 



more stable the part- of the skeleton which must be held 

 as a iixcil anchorage with relation to the parts in motion. 



Particular attention must be directed to the inhibitory 

 phenomena which are known to accompany most move- 

 ments. Sherrington, of Liverpool, holds the foremost 

 place among those whose researches have served to reveal 

 the importance of this matter. When a muscle is selected 

 at random and its mechanical relations are observed, we 

 can usually find one or more other muscles which can be 

 recogni/ed as adapted to pull against it. \Ye say that 

 these muscles are the antagonists of the first. So in the 

 ca-e of the biceps huineri, already mentioned as applying 

 its force to raise the forearm and to bend the elbow, we 

 see that the triceps, on the back of the upper arm, must 

 have the opposite effect. Technically speaking, the bicep- 

 is a flexor and the triceps an extensor. 



In other parts of the body we find muscles which are 

 less clearly arranged to act as antagonists, but the prin- 

 ciple is, notwithstanding, a general one. Certain muscles 

 rais", while others depress, the ribs. The analysis of such 

 effect- becomes more difficult when we consider examples 

 like the bending and straightening of the back in which 

 many muscles participate. The diaphragm offers a curious 

 illustration; when its center is drawn downward by the 

 contraction of its marginal portions the viscera are 

 crowded aside and must be accommodated by the stretch- 

 ing of the muscular abdominal walls. Hence, the ab- 

 dominal muscles are collectively antagonists of the dia- 

 phragm, but the transmission of pressure is through the 

 contents of the cavity. Sometimes opposing mu-cle< 

 are of very unequal strength. It is plain thai those 

 which raise the lower jaw and set the teeth are incom- 

 parably more powerful than those which make the counter- 

 movement , and there i- little occasion for a strong mechan- 

 i-m in the second ca.-e. 



Often we contract antagonistic muscles simultaneously 

 and with balanced force. This is done when the object is 

 to -ecu re firmness in any part ---to resist the tendency to 



