508 
The most deeply coloured muscle I have seen 
was the great pectoral muscle of the Teal 
( Querquedula crecca), killed after migration. 
n 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 hematosine of the blood con- 
tained in it. A muscle, if hypertrophied, 
grows redder, and vice versi; 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 
rtion of the proper colouring matter of the 
bres, 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 
e 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 rallel 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 trachee 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 
pulled 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.) 
MUSCLE. 
Fragments of. stri elementary fibres ng 
camange in cnt dimieaal magnified 300 
A, longitudinal cleavage. 
At a the longitudinal and transverse lines 
both seen, Some longitudinal lines are darker 
wider than the rest, and are not continuous fro 
end to end, 
b, primitive fibrille, separated from one 
by violence at the broken end of the fibre, a1 
marked by transverse lines equal in width to tho 
at a. 
¢ represents two appearances commonly present 
by the separated single fibrilla. On the upper on 
bs 
the borders and transverse lines are all pe: 
rectilinear, and the included spaces perfect] 
angular. In the lower the borders are scallope 
the spaces bead-like. When most distinct and 
finite, the fibrilla presents the former of these a 
pearances. 
B, transverse cleavage. The longitudinal li 
are scarcely visible. 
a, incomplete fracture following the opp 
surfaces of a disc, which stretches across the in 
val and retains the two f. ents in connexi 
The edge and surface of this disc are seen | 
minutely granular, the granules pond; 
size to the thickness of the disc and to th 
between the faint longitudinal lines. 
6, another disc nearly detached. 
But again, it always happens that de 
dinal lines, more or less continuous and 
rallel, according to the integrity of the” 
and the strength and distinctness of the tre 
verse lines, are also to be discerned ; and 1 
the transverse ones, not on the surface only, 
throughout the whole of its interior. 
found that there is a remarkable pronenes 
the fibre to split in the direction indicate: 
these lines also; by which splitting it is re 
into a great number of fibrilla. These br 
like the discs, do not exist as such in th 1 
and to obtain them its structure must be 
sarily broken up to a certain extent, fo 
union which naturally subsists between 
parts must be destroyed. It is therefore 
correct to say that there is an indication i 
entire state of the fibre of a longitudina 
rangement of its parts, occasioning a cle 
in that direction on the application of vio 
( Fig. 287.) " 
Sometimes the fibre will split into ; 
only, more often into fibrille only, but 
are always present in it the transverse and 
longitudinal lines which mark the two 
ages. It is the most common to find a ch 
or fracture taking both directions irregulal 
running partly in the transverse dark lin 
