510 
gularly one in front of the other, as a little 
Somalia will shew. Hence the latter 
seldom seem so definite or regular as the 
former. Nevertheless their union, seen on the 
surface of a detached disc, often presents much 
regularity, and forms curved or straight lines, 
such as result when a number of balls of equal 
size are huddled together on a level. 
It may be concluded from what has now 
been advanced, that the discs and fibrille, (or, 
in other words, the general mass of the fibre,) 
are made up of a number of particles, which 
I have termed primitive particles, or sarcous 
elements, and which would be obtained ina 
detached form by a general separation occur- 
ring along the transverse and longitudinal lines 
visible in the fibre. The existence of these 
particles, as well as their form and size, is in- 
dicated in the structure of the fibre, while yet 
entire; but they are united together, and have 
no independent existence, each being by its 
very nature a part of the mass, which is ren- 
dered incomplete by the removal of a single 
element. It results also from this descrip- 
tion that these particles have no definite 
outline on all their aspects, being united 
together; and that they only obtain such an 
outline on being severed; on which account 
it is perhaps impossible to say whether, in 
the perfect fibre, they be rounded, square, or 
polygonal. 
An example of the strong lateral union of 
these particles to one another was presented b 
the specimen from which the following skete 
was taken. It consisted of two or three ele- 
mentary fibres from the leg of a newly-born 
rabbit, which had been kept for some months 
in weak spirit. They were lying in a curved 
form on the field of the microscope, and pre- 
sented on the convex edge transverse series of 
Fig. 289. 
the particles, which, hav- 
ing lost their longitudinal 
while they retained their 
lateral union, stood out in 
relief, as represented in 
fig. 289, a, a, a. 
It sometimes happens 
that a linear series of them 
(a fibrilla) is separated, 
which has the appearance 
of a necklace of beads, 
with constricted intervals, 
while at other times the 
intervals, though dark, are 
of equal width with the 
light or highly refracting 
particles. Again, it is pos- 
sible, by steeping in acid 
a transverse section of a 
dried muscle, to separate 
cles, , oe ies the particles considerably 
come from one another, and to 
see that they are granules 
acting as lenses, being much more refractive 
than the material connecting them. Such 
transverse sections are an artificial division 
into discs, and the intervals between the Pe 
ticles widen out most in specimens taken from 
birds (fig. 290). 
MUSCLE. 
sepa from an 
ther. The cut edge of th 
tubular sheath of each fibre 
is also seen, : 
It is in these sarcous elements that the ¢ 
tractile power resides, and, as they are apt 
retain after death the varying effects of the con- 
traction they have undergone during the rigo 
mortis, it is not easy to give an exact measu 
ment of their size or shape. An average dr 
from very numerous observations shews, how 
ever, that they are very nearly alike in thes 
respects in all animals and at all periods of lif 
Their diameter in the longitudinal directior 
the fibre, as indicated by the distance bet 
the transverse lines, is thus shown to be :* — 
No. 
Eng.Inch. Obse 
In the Human subject.. shy +. 27 
In Mammalia generally qbgy - ‘ 
In Binds. 6) 040i 590% Wis +e ? 
In Reptiles..... cocee tikes | ee 
In Fish. .....<+000 » yee s ee 
In Insects .....006.- gdp oe f 
Their diameter in the opposite directic 
that marked by the distance between the lo 
itudinal lines is less, often by a half, | 
liable to variety from the cause already sf 
cified. 2 
In a paper, entitled “ On Fibre,” read be 
the Royal Society, on the 16th December 
the 6th January last,+ Dr. Barry describes” 
Jibrilla to be a flat filament rounded at 
edges, and deeply grooved along the m 
line on both its surfaces. He states that | 
flat filament consists of two spiral th 
placed side by side, with their coils interlacé 
that it “ is so situated in the fasciculus ( 
mentary fibre) of voluntary muscle, as to] 
sent its edge to the observer;” and tha 
curves of the spiral thread, then seen, 
have been the appearance that “ suggeste 
idea of longitudinal bead-like enlarg 
producing the strie.” In Dr. Barry’s op 
“the dark longitudinal strie are spaces | 
bably occupied by a lubricating fluid) be 
the edges of flat filaments, and the dark t 
verse strie, rows of spaces between the ci 
of the spiral threads,” of which each fla 
ment consists. ‘“ In a postscript, the a 
observes, that there are states of vol 
muscle in which the” (doubly-spiral, flat,) 
gitudinal filaments have no concern in 
peosucyes of the transverse strie, these 
ing occasioned by the windings of sp 
within which very minute bundles of k 
eS 
* Auct. loc. cit. p. 474. ae 
+ Proceedings of the Royal Society, No. 
