526 
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 por- 
tions, never in its totality at once, and that no 
particle of it is capable of exhibiting an active 
contraction for more than agen of age 
The appearances presen y muscle that 
has Gao va tured “4 its own inordinate con- 
traction in fatal tetanus in the human subject 
will supply the link wanting to connect the 
foregoing phenomena with those occurring in 
healthy contraction during life: for tetanic 
spasm differs from sustained voluntary contrac- 
tion only in its amountand 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 con- 
traction itself. 
The muscles are so arranged in the body 
that no amount of contraction which the me- 
chanism of the bony and ligamentous frame- 
work will permit one of them to undergo, can 
by possibility occasion the rupture of a relaxed 
antagonist: to be ruptured the antagonist must 
be itself contracted. But a muscle, if contract- 
ing beyond its natural amount, may be so re- 
sisted by mechanical powers, in or out of the 
body, as to rupture itself. Hence, the contrac- 
tion of a muscle is a necessary condition, and 
enerally 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; this latter may be either the 
active or ive 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 ele- 
mentary fibres present numerous bulges of a 
fusiform shape, in which the transverse stripes 
are very close. These swellings or contracted 
parts are separated from one another by inter- 
vals of various lengths, in which the fibre has 
either entirely given si or is more or less 
stretched and disorganized. These appearances 
are met with after all contractility has departed ; 
they are the vestiges of the spasm during life. 
Yet in other muscles, which have been likewise 
convulsed, but not ruptured, they are not 
found. Their presence is, therefore, the result 
of the rupture. They admit only of the follow- 
ing explanation: the contractile force has o 
rated at the points contracted, and by its excess 
the intermediate portions have been stretched to 
laceration. Having once given way, the con- 
tracted parts have become isolated, and can no 
longer have been extended after the subsidence of 
their contractile force ; they consequently retain 
the form and appearances they possessed, when 
surprised, as it were, by the rupture they have 
themselves produced of the intervening parts. 
Supposing, for a moment, that active con- 
traction were a universal and equable act, and 
* Phil. Trans. 1841, p. 69. 
MUSCULAR MOTION. 
that by the superior power of an i: a 
weak muscle been ruptured, the appear- 
ances resulting would manifestly be entirely — 
different from those now detailed. The fibres — 
beyond their ruptured point would have pe 
transverse stripes uniformly approximated. ; 
From the preceding facts I conclude, 
that active contraction never occurs in the 
mass of a muscle at once, nor in the 
any one elementary fibre, but is always parti 
at any one instant of time; 2dly, that no active 
contraction of a muscle, however appa 
ge ge is more than instantaneous i 
one of its parts or particles; and therefore, 
3dly, that the sustained active contraction of a 
muscle is an act compounded of an 
number of partial and momentary contractic 
incessantly changing their place, and engaging 
new parts in succession; for every ae ee ts 
the Ans must take its due share in the act. 
Ar phenomena yet remain to be mentic 
which, by admitting of a satisfactory xplana- 
tion on this view of the subject, give stre : 
testimony to its correctness. The first he 
muscular sound heard on applying the ear to a 
muscle in action. It resembles, acce to 
Dr. Wollaston’s apt simile,* the distant ramb= 
ling of carriage wheels, or an exceedingly rapid 
and faint tremulous vibration, which, when well 
marked, has a metallic tone. It is the sound of 
friction, and appears to be occasioned by those 
movements of the neighbouring fibres upon one 
another, with which the partial contraction 
must be attended in their incessant oscil oni 
The other phenomenon is one, the existences 
which has been recently ascertained by MM. 
Becquerel and Breschet,t viz. that a 
during contraction augments in temperature. 
They have found this increase to be usually 
more than 1° Fahr., but sometimes, when 
exertion has been continued for five minut 
as in sawing a piece of wood, it has been double 
that amount. is development of heat ‘ 
to be in a great measure attributable to, a 
even a necessary consequence of, the frictic 
just alluded to. 
Thus it would appear that active contract 
consists in a disturbance of that state of equ 
brium ordinarily existing in muscles 
rest; that their different portions suce 
undergo momentary contractions, and that #l 
is always a considerable part of each fibre u 
contracted. This will account for the rema 
able fact that detached fragments of the ¥ 
tary fibre will contract by t irds of | 
length, though an entire muscle, in its ne 
situation, cannot shorten by more than 
third. This great capacity of contraction imt 
tissue would be without a purpose, if ity 
not that it only admits of momentary exer 
and therefore requires that in the ongan sui 
sive parts should take up the act, and by 
doing, render it, as a whole, continuous. Tn 
active fibre the contracting parts are conti ual 
Hing 
“ 
”* Phil. Trans. 1811. 
+ Recherches sur la chaleur animale, 
des appareils thermo-electriques ; par ' 
uerel et Breschet, Membres de I’Institut. Archiv 
u Museum, tom. i. p. 4U2. a 
x me 
