ee eee 
MUSCLE. 
—- 
View of the capillaries of muscle (part of the latis- 
simus dorsi of u mouse, where it consists of a single 
sheet of fibres ), 
4@, a, terminal twig of the artery. 
6, b, terminal twigs of two neighbouring venous 
Beeches, anastomosing, and carrying off blood 
the same capillary net-work c, c. 
¢, an elementary fibre, to show the relative size 
and direction of those to which the capillaries here 
represented are distributed. 
particles are compressed and elongated, some- 
times to a great extent, evidently by the nar- 
rowness of the canal which contains them. 
It may seem at first sight not doubtful that in 
the living creature these elastic blood-discs are 
similarly elongated in their passage through 
the vessels of muscle, but the admirable re- 
searches of Poiseuille will perhaps serve to 
explain this appearance without our being 
driven to suppose the presence of so formid- 
able an obstacle to the capillary circulation 
} et these organs. It is more probable 
that the contraction of the vessels and the com- 
pression of the blood-discs occur, on some of 
the contents of the vessels being permitted to 
escape by the severing of the fragment for 
microscopic examination. The coats of the 
capillaries of muscle consist of a simple diapha- 
nous membrane, in which a few irregular-shaped 
eytoblasts occur at infrequent intervals. 
or the nerves of muscle-—The distribution 
f the nerves through muscular structures has 
always been a subject of great interest with 
those who looked to this line of inquiry for 
some clue to the explanation, either of that 
wonderful active connexion subsisting between 
them, or of the nature of the contractile act 
itself. But though the anatomical results ac- 
cruing from this inquiry are of a highly satis- 
factory kind, considered in themselves alone, 
517 
= they cannot be said to have hitherto contri- 
uted, in any great degree, to the elucidation of 
these mysterious questions. The best mode of 
inspecting the arrangement of the ultimate ner-' 
vous twigs, is to select a very thin muscle, (as 
one of the abdominal muscles of any small 
animal, or one of the muscles of the eye of a 
small bird,) to steep it in weak acetic acid, and 
then thin it out under the compressorium. The 
primitive tubules of the nerve may then be 
readily distinguished with a power of 100 to” 
200 linear. They separate from one another, at 
first in sets, afterwards in twos, threes, or fours, 
and if these be followed they will be found 
ultimately separating from one another, form- 
ing arches, and returning either to the same 
bundle from which they set out or to some 
neighbouring one (fig. 300). In this loop- 
like course they accompany to some extent the 
minute bloodvessels, but do not accurately 
follow them in their last windings, since their 
distribution is in a different figure. They pass 
among the fibres of the muscle, and touch the 
sarcolemma as they pass; but as far as present 
researches have informed us, they are entirely 
precluded by this structure from all contact 
with the contractile material, and from all im- 
mediate intercourse with it. How then shall 
we explain the transmission of the nervous in- 
fluence to a material thus enclosed? If it 
were wise or safe to go a single step in advance 
of pure observation on so abstruse a question, 
we might suggest, resting on the seemingly 
sure ground of exact anatomy, that this in- 
fluence must be of a nature capable of ema- 
nating beyond the limits of the organ which 
furnishes it. But further than this, as to how, 
or to what extent this influence may so emanate, 
Fig. 300. 
L 
Loop-like termination of the nerves in voluntary muscle. 
After Burdach. 
or as to what may be its nature, it would, per- 
haps, in the present state of knowledge, be 
hardly warrantable even to speculate. 
d. Of the distribution of the striped and 
unstriped fibre in the body.—The striped fibre 
is met with in all the voluntary muscles, and 
in a few involuntary, as the constrictors of the. 
