330 OF THE PRIMARY TISSUES OF THE HUMAN BODY. 



tion," which he has experimentally studied under a great variety of conditions, 

 are sufficient to " demonstrate the production of an electrical disequilibrium in 

 the act of muscular contraction/' 1 This production of Electric disturbance in 

 muscular contraction may be attributed to either or all of the causes which have 

 been suggested for the development of heat ; but that it is specially connected 

 with the chemical changes which then take place, seems probable from the fact 

 that a contraction in the muscles of the galvanoscopic frog is seen, when its 

 nerve is simply introduced into an incision made in the muscle of a living or a 

 recently-killed animal, in such a manner that the extremity is applied to the 

 deepest part of the wound, and another portion to its lips or to the surface of 

 the muscle. As this contraction takes place when the muscle is completely pas- 

 sive, it is obvious that the source of the electric current which determines it 

 must lie in the molecular changes taking place in the course of the nutrition of 

 the muscle ; and the explanation of its constant direction from the interior to 

 the exterior of the muscle seems to lie in the difference in the rate of these 

 changes, which will go on more energetically in its interior than they will do 

 nearer its surface, where the proper muscular fibres are mingled with a larger pro- 

 portion of areolar and tendinous substance. 3 Muscular contraction also gives 

 rise to the production of Soung, as was first noticed by Dr. Wollaston. 3 When 

 the ear is applied to a muscle in action, a sound is heard resembling the distant 

 rumbling of carriage-wheels, or an exceedingly rapid and faint tremulous vibra- 

 tion, which, when well marked, has an almost metallic tone. This sound may 

 be readily made audible in the manner suggested by Dr. Wollaston ; namely, 

 by placing the tip of the little finger in the ear, and then making some muscles 

 contract (as those of the ball of the thumb), whose sound may be conducted to 

 the ear through the substance of the hand and finger. The continuity of this 

 sound through the whole period during which contraction is maintained, is an 

 important confirmation of the view which is based on other foundations, that 

 there is a continual alternation of contractions and relaxations among the indi- 

 vidual fibres of any Muscle which is putting forth its contractile power, as a 

 whole, for any length of time ( 303). The sound may be readily conceived 

 to depend upon the friction of the elements of the muscle, one upon another; 

 which must thus be perpetually taking place, so long as it continues in a state 

 of activity. There can be little question that the first sound of the Heart, 

 which accompanies the ventricular systole, is partly attributable to muscular 

 contraction. 



331. Of Muscular Tonicity. We have now to consider the other form of 

 Contractility, which produces a constant tendency to contraction (varying, how- 

 ever, as to its degree) in the Muscular fibre ; but which is so far different from 

 simple Elasticity, that it abates after death, before decomposition has taken 

 place. This Tonicity is to be distinguished from the Muscular " tension," which 

 is the result of the "reflex" operation of the nervous centres (CHAP. xiv. 

 SECT. 2) ; being manifested as well when the muscle is altogether removed from 



increased by alternately contracting the muscles, first of one arm, and then of the other, 

 in time with the oscillations of the needle. Nevertheless, Prof. Matteucci (whose authority 

 on this subject stands most deservedly high), after pointing out various sources of error in 

 the use of the galvanometer, states that he has tried a great number of experiments after 

 M. Du Bois Reymond's method, increasing the number of elements which contract at the 

 same time (as by operating on a circle of thirty or forty individuals, who all contracted the 

 same arm at once) without ever succeeding in obtaining an evident and constant develop- 

 ment of electricity by muscular contraction. (See "Phil. Trans.," 1850, p. 646.) 



1 "Philosophical Transactions," 1850, p. 649. See also Prof. Matteucci's previous 

 researches on "induced contraction," in the "Phil. Trans." for 1845 and 1847. 



2 See Prof. Matteucci's "Lectures on the Physical Phenomena of Living Beings," 

 Lects. ix. and x. 



3 "Philosophical Transactions," 1811. 



