MUSCULAR CONTRACTION. 469 



The most striking of the phenomena accompanying mus- 

 cular action is shortening and hardening of the fibres. It is 

 only necessary to observe the action of any well-developed 

 muscle to appreciate these changes. The active shortening 

 is shown by the approximation of the points of attachment, 

 and the hardening is sufficiently palpable. The latter phe- 

 nomenon is marked in proportion to the development. of the 

 true muscular tissue and its freedom from inert matter, such 

 as fat. "We have already seen that it is the muscular sub- 

 stance alone that has the property of contraction ; and we 

 have shown that this action increases the consumption of 

 oxygen and probably of other matters, the production of 

 carbonic acid and some other excrementitious principles, and 

 develops heat. 



Notwithstanding the marked and constant changes in the 

 form and consistence of the muscles during contraction, the 

 actual volume is unchanged, or it undergoes modifications so 

 slight that they may practically be disregarded. Experi- 

 ments on this point have been so uniform in their results, 

 that it is hardly necessary to refer to them in detail. All 

 modern observers accept the results of the older experiments 

 in which muscles have been made to contract in a vessel of 

 water connected with a small upright tube, showing that 

 when the muscles are in active contraction as the result of 

 a galvanic stimulus, the elevation of the liquid in the tube 

 is unchanged. These old experiments have been recently 

 repeated by Marey 1 and others, with more delicate and sen- 

 sitive apparatus, and have been followed by the same results. 

 It is evident, therefore, that a muscle, while it hardens and 

 changes in form during contraction, does not sensibly change 

 in its actual volume. 



1 MAREY, Du mouvement dans ksfondions de la vie, Paris, 1868, p. 269. The 

 earlier experiments of this kind were made by Glisson, Elaine, Carlisle, Barzel- 

 lotti, Prevost, and Dumas, and some others. Prevost and Dumas used several 

 large pieces of muscle, and their results were very satisfactory. (Memoire sur 

 les phenomenes qui accompagnent la contraction de la fibre musculaire. Journal 

 de physiologic, Paris, 1823, tome iii., p. 310.) 



