1 82 LOCOMOTION. [CHAP. vn. 



those from which it was receding is removed, and the appearances 

 of contraction remain. A distinction is required between the con- 

 tractile force and the contraction resulting from its exercise. The 

 latter will be permanent, if no force from without be exerted to 

 obliterate it by stretching ; for a contracted muscle has no power 

 of extending itself, there is no repellent force between its molecules. 

 From these phenomena, therefore, it is possible to eliminate the 

 appearances resulting from a subsided force, and to judge of the 

 mode and duration of action of the force itself. Thus sifted, they 

 prove that, even when directly stimulated by water after removal 

 from the body, a muscle contracts in successive portions, never in 

 its totality at once ; and that no particle of it is capable of exhibit- 

 ing an active contraction for more than an instant of time. 



The appearances presented by muscle that has been ruptured by 

 its own inordinate contraction in fatal tetanus, in the human sub- 

 ject, will supply the link wanting to connect the foregoing pheno- 

 mena with those occurring in healthy contraction during life : for 

 tetanic spasm differs from sustained voluntary contraction only in 

 its amount and protracted duration, and in its being independent 

 of the will ; none of which circumstances are of essential import- 

 ance in regard to the nature of the act of contraction itself. 



The muscles are so arranged in the body, that no amount of con- 

 traction which the mechanism of the bony and ligamentous frame- 

 work will permit one of them to undergo, can by possibility occasion 

 the rupture of an antagonist, provided it remain relaxed : to be 

 ruptured, the antagonist must be itself contracted. But a muscle, if 

 contracted beyond its natural amount, may be so resisted by me- 

 chanical powers, in or out of the body, as to rupture itself. Hence, 

 the contraction of a muscle is a necessary condition, and generally 

 the essential cause of its own rupture : the other condition being a 

 force greater than the tenacity of the ruptured part, holding its 

 ends asunder ; which latter may be either the active or passive 

 contraction of antagonists, or mere mechanical resistance : but it is 

 evident, that, for a muscle to be ruptured by its own contraction, 

 that contraction must be partial, as is shewn in the case of the 

 frog's muscle already mentioned. 



An examination of muscle ruptured in tetanus is found to bear 

 out these observations in the fullest manner.* The elementary fibres 

 present numerous bulges of a fusiform shape, in which the trans- 

 verse stripes are very close together. These swellings, or contracted 



* Phil. Trans. 1841, p. 69. 



