MOVEMENTS OF VOLUNTARY MUSCLE. 
493 
vation, and made to undergo contraction, which, when excited by galvanism, is a mo- 
mentary act, and difficult of inspection, the return to a straight line, on relaxation, 
is not brought about by an antagonist force ; the ends remain approximated, but 
the fasciculi being actually elongated fall into zigzags. A phenomenon, the cause 
of which has frequently been speculated on, may serve yet further to elucidate this 
hitherto obscure question, I mean that of the sounds heard by applying the ear to a 
muscle in vigorous action. These sounds have been compared to an exceedingly 
rapid faint silvery vibration, and they seem to me to be explicable by supposing the 
several fasciculi to be in rapid and constant motion, one against the other, by varying 
amounts of contraction in different fasciculi and parts of fasciculi. It has been al- 
ready shown that a part of a fasciculus may act independently of the rest; that a 
contraction may oscillate to and fro along a fasciculus, or travel from one end of it 
towards the other. These phenomena are not imaginary, but may be readily observed 
by any one in contracting fasciculi removed from the body ; and though I do not 
mean to assert their occurrence in voluntary and healthy contraction, there would 
appear to be no difficulty in the present state of our knowledge, in concluding that 
such is actually the normal condition during life. 
The chief results of the above inquiry may be thus briefly recapitulated : 
1. The primitive fasciculi of voluntary muscle consist of elongated polygonal masses 
of primitive component particles, or sarcous elements, arranged and united together end- 
ways and sideways, so as to constitute in these directions respectively, Jibrillus and 
discs, either of which may, in certain cases, be detached as such, and both of which, 
in the unmutilated organ, always exist together. It is the assemblage of these 
particles, which may most properly be styled “ Sarcous tissue.” 
The dark longitudinal striae are shadows between fibrillae, the dark transverse striae, 
shadows between discs. 
2. Every primitive fasciculus is invested by a highly delicate, transparent, and 
probably elastic membrane, the sarcolemma, which is adherent to its surface, and 
isolates the sarcous tissue from every other part. 
3. Every primitive fasciculus contains upon or among its primitive particles, num- 
bers of corpuscles, which either actually are, or are analogous to, the nuclei of the 
original cells of development; and it is certain, that during growth, these corpuscles 
increase in number. 
4. The extremities of the primitive fasciculi, in certain cases at least, are directly 
continuous with tendinous structure, and are not taper, but obliquely or transversely 
truncated. This is at variance with the common opinion that the tendon embraces 
each fasciculus, and is continued along it from end to end, constituting its cellular 
sheath. 
5. In contraction of the fasciculi, observed after death, the primitive particles are 
