THE MUSCULAR SYSTEM. 251 



the siijrar of muscles or inosit, and tlic coloring matter, ^vllich substances, 

 even the last-named, are lodged partly in the fibrils themselves, partly 

 and chiefly, and this is the case especially with the albumen, in the in- 

 terstitial substance, by which the fibrils are connected together. The 

 16-83 parts of insoluble residue belong in part to the elastic tissue in 

 the vessels and pgr/wi^/smw, and to the smooth muscle in the vessels, but 

 principally to the muscular fibrils themselves, which, as we have before 

 seen (§ 27), consist of a substance allied to fibrin. The sarcoJemma is 

 less afi'ected by alkalies and acids than the fibrils, and approaches in its 

 nature more nearly to the memhrana propria of the glands, the walls of 

 the capillaries, and the membrane of many cells. The coloring matter 

 of the muscles (and the muscles themselves), like the blood, becomes 

 bright red in the air, or still more in oxygen gas, and is rendered dark 

 by sulphuretted hydrogen. It is extracted, and indeed readily, by water, 

 but not by salts, in which circumstance, that is to say, in an altera- 

 tion in the degree of concentration of the plasma with which the muscle 

 is imbued, is perhaps to be sought the principal reason for the readiness 

 with which the color of the muscles is altered in disease. 



The muscles, although softer and more easily torn than the tendons, 

 possess, nevertheless, considerable tenacity, particularly during life, and 

 they have a certain degree of elasticity. During life, as has been cor- 

 rectly remarked by E. Weber, even when not under the influence of 

 the nerves, they are not for the most part in their natural form, but 

 stretched, or in a state of tension, and like harp-strings in the same 

 condition, exert an elastic force. This is satisfactorily shown when the 

 tendons of the extensor muscles in an animal's limb which is strongly 

 flexed, are cut through, the nerves having been previously divided, 

 whereupon the tendons are very considerably retracted (E. Weber). 

 This tension of the muscles varies very much, according to the position 

 of the limbs. It is very slight when the body is at rest with the limbs 

 semiflexed, still less or even wholly absent when a muscle falls into a 

 state of repose after it has acted powerfully upon the limb ; greater, 

 and manifested in the greatest degree, when the antagonists of a muscle 

 are acting with all their force. According to Weber, the living muscle, 

 when in a state of inactivity, may be compared with caoutchouc, seeing 

 that, like that substance, they possess a very great elastic extensibility ; 

 or, in other words, a slight but very jyerfect elasticity, as may be readily 

 perceived in the muscles even of dead animals, which may be alternately 

 stretched and allowed to retract. Owing to their elasticity, the muscles 

 offer scarcely any hindrance to the movements of the limbs, and in con- 

 sequence of its perfect nature, they recover their previous form and 

 length even after the greatest possible extension. This is exemplified 

 in the stretching of the abdominal muscles in pregnancy and in certain 

 pathological conditions. When the muscles are in a state of activity, 



