Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 3: Ins-Pla
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit29464/516/
508 
MUSCLE, 
The most deeply coloured muscle I have seen 
was the great pectoral muscle of the Teal 
( Querquedula crecca), killed after migration. 
In Mammalia the colour is ordinarily red, 
being deeper in the Carnivora than in the vege¬ 
table feeders. Among the domestic animals 
many varieties exist, which need not be spe¬ 
cially enumerated. A considerable part of the 
colouring matter is extracted by repeated wash¬ 
ing of a muscle, which then becomes pale, but 
not quite colourless ; some part of the loss of 
colour here sustained is doubtless owing to the 
solution of the hæmatosine of the blood con¬ 
tained in it. A muscle, if hypertrophied, 
grows redder, and vice versa; and probably 
the practice of bleeding calves some days 
before they are killed, makes their flesh more 
pale and tender, by causing the absorption of a 
portion of the proper colouring matter of the 
fibres, as well as by abstracting the blood 
circulating among them. 
5. Internal structure.—Though the elemen¬ 
tary fibres of all animals are visible to the 
naked eye, and in some animals, as the Skate 
(Raia Batus), are often as thick as a small pin, 
nothing of their internal organization can be 
distinguished without the aid of a powerful 
lens. There is indeed, in certain lights, a 
splendid pearly iridescence, resulting from 
the arrangement of their structure, and quite 
characteristic among the soft tissues ; but this is 
not explained till a high power of the micro¬ 
scope is brought to bear upon the fibres. They 
are then seen, when viewed on the side, to be 
marked by innumerable alternate light and dark 
lines, whose delicacy and regularity nothing can 
surpass, and which take a parallel direction 
across them; and if the focus be altered so as 
to penetrate the fibre, they are found to be pre¬ 
sent within it just as on its surface, thus differ¬ 
ing from those on the tracheæ of insects, which 
exist only at the surface. At the extreme border 
of the fibre the light lines are sometimes seen to 
project a trifling degree more than the dark 
ones, thus giving a slight scallop, or regular 
indentation, to the edge. If often happens, in 
tearing the fibres roughly with needles before 
examination, that they crack across, or give way 
entirely, along one or several of these dark lines, 
the line of fracture or cleavage running more or 
less completely through the fibre in a plane at 
right angles with its axis; and occasionally two 
or more of such complete cleavages will occur 
close together, the result of which is the separa¬ 
tion of so many plates or discs (fig. 287, B), of 
which the light lines at the surface are the edges, 
and the corresponding light lines seen within 
are what may be termed the focal sections. 
Thus it is evident that there is a tendency in 
the mass of the fibre to separate, when torn or 
nulled, after death, along the transverse planes, of 
which the dark transverse stripes are the edges. 
When such a separation takes place, a series 
of discs result, but to say that the fibre is a 
mere pile of discs is incorrect, for the discs are 
only formed by its disintegration. Neverthe¬ 
less they are marked out, and their number 
and form are imprinted, in the very structure 
of the fibre, in its perfect state. (Figs. 287 
and 288.) 
Fig. 287. 
Fragments of striped elementary fibres, shewing a 
cleavage in opposite directions, magnified 300 diam. 
A, longitudinal cleavage. 
At a the longitudinal and transverse lines are 
both seen. Some longitudinal lines are darker and 
wider than the rest, and are not continuous from 
end to end. 
b, primitive fibrillæ, separated from one another 
by violence at the broken end of the fibre, and 
marked by transverse lines equal in width to those 
at a. 
c represents two appearances commonly presented 
by the separated single fibrillæ. On the upper one 
the borders and transverse lines are all perfectly 
rectilinear, and the included spaces perfectly rect¬ 
angular. In the lower the borders are scalloped, 
the spaces bead-like. When most distinct and de¬ 
finite, the fibrilla presents the former of these ap¬ 
pearances. 
B, transverse cleavage. The longitudinal lines 
are scarcely visible. 
a, incomplete fracture following the opposite 
surfaces of a disc, which stretches across the inter¬ 
val and retains the two fragments in connexion. 
The edge and surface of this disc are seen to be 
minutely granular, the granules corresponding in 
size to the thickness of the disc and to the distance 
between the faint longitudinal lines. 
b, another disc nearly detached. 
But again, it always happens that longitu¬ 
dinal lines, more or less continuous and pa¬ 
rallel, according to the integrity of the fibre 
and the strength and distinctness of the trans¬ 
verse lines, are also to be discerned ; and like 
the transverse ones, not on the surface only, but 
throughout the whole of its interior. And it is 
found that there is a remarkable proneness in 
the fibre to split in the direction indicated by 
these lines also; by which splitting it is resolved 
into a great number of fibrillæ. These fibrillæ, 
like the discs, do not exist as such in the fibre, 
and to obtain them its structure must be neces¬ 
sarily broken up to a certain extent, for the 
union which naturally subsists between these 
parts must be destroyed. It is therefore most 
correct to say that there is an indication in the 
entire state of the fibre of a longitudinal ar¬ 
rangement of its parts, occasioning a cleavage 
in that direction on the application of violence. 
( Fig. 287.) 
Sometimes the fibre will split into discs 
only, more often into fibrillæ only, but there 
are always present in it the transverse and the 
longitudinal lines which mark the two cleav¬ 
ages. It is the most common to find a crack 
or fracture taking both directions irregularly, 
running partly in the transverse dark lines,
        

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