OF VITAL MOTION. 57 



state are related to each other, that the mode to 

 which the term irritability is applied, where the con- 

 traction is sudden and transitory, and the mode called 

 tonicity^ where the contraction is gradual and its 

 duration indeterminate, are but varieties of the same 

 state. This opinion has been gaining many sup- 

 porters of late, and it is advocated in one of the most 

 recent and important text-books of physiology.* 



The second and more important of these consi- 

 derations is, that the state opposed to muscular 

 contraction is something more than mere passive 

 relaxation. 



This view has been advocated by more than one 

 writer, and it is distinctly enunciated in the works of 

 Bichat. In regard to the voluntary muscles, how- 

 ever, the opinion of this physiologist is somewhat 

 obscure, for he speaks of these muscles being restored 

 to the state in which they were previous to con- 

 traction by the action of the antagonist muscles. 

 But at the same time, he cites some facts which show 

 the presence of a positive power of extension : thus, 

 he speaks of the contraction and subsequent dilatation 

 of a muscle after its removal from the body, when 

 there can be no extraneous traction, and of the con- 

 vulsive movements of a similar character which may 

 be seen in divided muscles when these have been 



* Physiological Anatomy and Physiology of Man: Todd and 

 Bowman, vol. ii. p. 172 1845. 



