456 GENERAL ANATOMY. 



that of the plexus of a limb, or only by that of an isolated 

 nerve. 



734. The contraction of the external muscles, through 

 causes which act upon the muscular tissue, or upon the nerves, 

 or upon the nervous centre, sometimes becomes feeble and un- 

 certain (in trembling;) impossible (in paralysis;) permanent 

 (in tonic spasm or contraction, tetanus;) involuntary and irre- 

 gular (in convulsions, clonic spasm, or contraction.) 



