308 



OF THE PRIMARY TISSUES OF THE HUMAN BODY. 



sented by Muscular Fibre, when spontaneously passing into that state of contrac- 

 tion' which is termed the rigor mortis ( 333) ; but there can be no reasonable 



Fig. 97. 



I 





Muscular Fibre of Skate, in a state of rest (A), and in three different stages of contraction (B, c, D). 



doubt, that the phenomena of contraction, excited by the agency of the nerves, 

 are precisely similar. Mr. Bowman has remarked, that stimuli of various 

 kinds, directly applied to them, produce corresponding effects, although, in the 

 case of galvanism, the change is too rapid for its steps to be followed ; and that, 

 from the appearances presented by muscles which have been affected with tetanic 

 spasms, the contraction produced by nervous agency may be inferred to cor- 

 respond in character. The zigzag arrangement which is so often seen in the 

 fibres, may be easily produced, by approximating the ends of a fasciculus, after 

 the irritability of its fibres has ceased; 1 and seems to be that into which fibres 

 are naturally thrown, if, on elongation following contraction, they are not at 

 once stretched by antagonist muscles. Many facts support the opinion, that, 

 when an entire muscle is contracting, all its fasciculi are not in contraction at 

 once ; but that there is a continual interchange in the parts by which the ten- 

 sion is effected, some relaxing whilst others are shortening. On examining a 

 muscle of which some fasciculi present the zigzag arrangement, others will be 

 seen (if the two extremities have not been purposely approximated) to be quite 

 straight, and in a state of contraction ; and the former appearance seems to be 

 presented by bundles of fibres, which have either not yet entered into contrac- 

 tion, or which have relaxed after undergoing it, but of which the extremities 

 are still approximated by the agency of other contracting fibres. Again, the 

 sound emitted by a muscle in vigorous contraction, indicates a continual move- 

 ment among its particles ( 330). And the great excess of force put forth, 

 when from any cause an unusual amount of nervous power is determined to a 

 muscle (as in violent passion or mania, or in those peculiar states of abstraction 

 in which the attention can be entirely concentrated upon any one part), above 

 that which an ordinary voluntary effort can evoke, clearly indicates that, in the 

 latter case, only a part of the muscle can be in action at once, which seems to be 

 attributable to this constant movement of its substance. The result of various 

 experiments made for the purpose, leads to the conclusion, that the total bulk 

 of a muscle in contraction is not less than when it is in a relaxed state ; or that 

 the difference, if any exist, is extremely trifling. 



304. Every Muscular Fibre, of the striated kind at least, is attached at its 

 extremities to white fibrous tissue; through the medium of which it exerts its 

 contractile power on the bone or other substance which it is destined to move. 

 The whole fasciculus of fibrillse sometimes ends abruptly in a perfect disk; but 

 not unfrequently the extremities of the fibres become rounded or conical, in con- 



1 Mr. Bowman's conclusions have been since confirmed by Prof. E. Weber ("Archives 

 d' Anatomic Gdnerale," Jan. 1846), and by other observers. 



