S14 
indications of a regular arrangement in gra- 
nules are usually to be met with. It is com- 
mon for the longitudinal lines to become well- 
defined before the transverse ones. When 
both are strongly marked, as is always the case 
at birth, the nuclei of the cells, which were 
before visible, disappear, being shrouded from 
view by the dark shadows caused by the mul- 
titudinous refractions of the light transmitted 
through the mass of granules; but, as before 
stated, they can still be shown to exist by im- 
mersion ina weak acid, which, while it swells 
the fibrinous material of the granules and 
obliterates their intervening lines, has no action 
upon the nuclei. 
6. Of the unstriped elementary fibres.—This 
variety possesses far less interest than the other 
in consequence of its apparent simplicity of 
structure. The fibres consist of flattened bands, 
generally of a pale colour, bulged at frequent 
intervals by elongated corpuscles similar to 
those of striped muscle, and capable of being 
displayed by the same process (fig. 298). The 
texture of these fibres seems to be homoge- 
neous. By transmitted light they have usually 
a soft, very finely mottled aspect, and without 
a darkly-shaded border. Sometimes the mot- 
tling is so decided as to appear granular, and 
occasionally these granules are arranged ina 
linear series for some distance. This condition 
is probably an approximation towards the struc- 
ture of the striped fibre, for I have observed 
the granules to be about the size of the sarcous 
elements already described. It is generally to 
be seen more or less distinctly in the gizzard 
of Birds, and I have now and then met with it in 
the fresh muscle of the stomach, intestinal 
canal, urinary bladder, and uterus of Mam- 
malia. The ordinary diameter of the unstriped 
Fig. 298. 
nstriped bres the human colon. 
a, treated with acetic acid, and shewing the cor- 
puscles. 
b, fragment of a detached fibre, not touched with 
acid. ; 
MUSCLE. 
fibre is from gpsoth to gahsth of an inch. m 
this account oie appearance of these fibre: 
might be expected that their discrimination 
from ane tissues would be often difficult. 
And, in fact, it is so to an inexperienced eye. 
The peculiar texture, however, the size, the oft 
margin, and, above all, the presence of nume: 
rous elongated oval corpuscles, with two 
three granules in their centre, are characters 
which, taken together, L believe to be decisive 
As a number of fibres usually take a paral 
course together, the bulgings occasioned 
the corpuscles give rise to partial longitud 
shadows, extending for some way it 
corpuscles, in the intervals of the fibres. Aj 
these irregular longitudinal shadows occ 
ec uniformly throughout an g 
bres, and as some are necessarily out ¢ 
while others are in focus, the whole mass co 
monly presents a very confused reticul: 
pearance, which has given rise to an alm 
universal notion that these fibres do, in reali 
interlace one with another, and do not r 
parallel. This notion, however, is, in @ 
cases, erroneous. It is doubtful whether 
fibres are invested in a sarcolemma: none 
hitherto been detected in an unequivocal n 
ner. It is also still a matter of specu 
how they terminate, or whether they in 
instances have a termination. In the cas 
the more or less circular set of fibres, in lc 
the small intestine, for example, it is uncet 
whether each fibre surrounds the ca 
returning into itself as a ring, or, me 
once, as a spiral, or whether it only 
tially pts § it, the rest of the circle b 
completed by others. Whether the are 
tissue (the representative of the fibrous) 
is always found in connection with these 
serves to give them an attachment by u 
with their extremities, or by involving the 
its meshes, 1s also altogether unknown. 
the gizzard of Birds the ends of the fibres 
united to white fibrous tissue, thus m : 
approximation to the striped fibre, as th 
in colour. But I have not been able, 
diligent search, to detect the true trans 
stripes, which Ficinus describes to exist i 
organ. 1 
Of the mode of aggregation of the 
tary fibres—The two kinds of fibre 
structure has now been described, are 
gated into masses of very various sh 
bulk, and supplied with areolar tissue, 
and nerves, so as together to form the 
termed muscles. But if we trace these 
downwards through the animal scale, we 
to examples in which solitary fibres exi: 
out any such appendages, and yet e€ 
performing the office of, and truly con: 
a perfect muscle. And even many f 
found, so far smaller than the usual 
sions as to consist of only one or tw 
series of sarcous elements, and these 
only visibly present near the centre of th 
where developement is most advai e 
the contractile energy greatest. In sucht 
and simple forms we may ea tr 
from the striped towards the unstr 
Vic 
iverecalic 
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