MOVEMENTS OF VOLUNTARY MUSCLE. 
475 
composed of a coil of filamentous tissue ; but such a structure is entirely imaginary. 
Mr. Skey also speaks of the “tube of the fibre,” but without any reference to the true 
sheath*. Muller alludes to it, however, in the following terms. “Each primi- 
tive fasciculus has a very delicate sh'eath, which can often be perceived, forming 
a transparent border to the fasciculus^.” And I have lately met with a passage from 
an unpublished letter by M. Turpin, quoted by Mandl^:, in which the author de- 
scribes it as “ a membranous aponeurotic tube, of extreme thinness, white, transparent, 
and finely puckered or folded crosswise, these folds being rigorously comparable to 
those, likewise transverse, which exist on the surface of the skin of leeches, when con- 
tracted.” These folds are afterwards said to be removed by immersion for some days 
in water, as those of a piece of finely plaited linen would be. From which it seems 
probable, that the author considers this sheath to be concerned in the production of 
the transverse striae. The illustrative sketch confirms this, for the striae are not 
seen except where the sheath holds together the primitive filaments, and these are 
not represented as beaded, where they project as a brush from the extremity §. It 
will be immediately perceived that the true structure about to be described has no 
analogy whatever with the cellular membrane of muscle, and that it is not in any 
way concerned in the production of the transverse striae ; but that, on the contrary, 
it seems to be a texture sui generis , fulfilling a distinct function, peculiar to muscle. 
It seems advisable, therefore, to call it by a distinct name, and I have been in the 
habit of styling it Sarcolemma\\ , a term descriptive of its nature. As, however, in 
what follows, no allusion whatever is intended to be made to the cellular sheath of 
muscle, the word sheath, to avoid repetition, will be employed as synonymous with 
sarcolemma^[. 
* Philosophical Transactions, 1837, p. 377. f Physiology, translated by Baly, p. 882. 
% Read before the Academy of Sciences, December 12, 1831. 
§ [Since this paper was read, my attention has been directed to a passage in the 4th edition of Dr. Jones 
Quain’s Elements of Anatomy, 1837, (p. 104-5,) where the author speaks of a “ Myolema” as having been 
observed by himself. The following short extracts comprise all that is said by him concerning it. “ The fibre 
(primitive fasciculus) is not homogeneous or gelatinous, but consists of a tube, the myolema, filled with minute 
globules, as represented in fig. 26.” And a little before, speaking of the “ minute extremely close transverse 
bars (transverse strise), these appear to be in the myolema, and to be owing to its being thrown into plicse, 
as they disappear if the fibre is stretched. And again, in p. 81, where a “ speculation as to the mechanism 
of muscular contraction is offered, “ we can hardly suppose it (the nervous influence) to act on the myolema, 
which is but a delicate or slightly modified cellular tissue.” Mr. W. J. E. Wilson', who prepared the spe- 
cimens examined by Dr. Quain, also describes the sheath of the primitive fasciculi as consisting of cellular 
membrane.] 
|| This term (from er«p£, caro, and Xe/uya, cortex) seems preferable to that of myolema, derived from yvs, the 
whole organ, musculus. 
H [While these pages are going through the press, I learn that Professor Schwann, in his recent work 
(Mikroskopische Untersuchungen fiber die Uebereinstimmung in der Struktur u. dem Waehsthum der Thiere 
1 The Anatomist’s Vade Mecum, published in the present year. 
3 p 2 
