MUSCLE. 
organization and properties, but that this simple 
method of procedure is the one most likely to 
lead to a true insight and conclusion regarding 
the anatomy, not only of this but of all elemen- 
tary structures, becomes every day more evi- 
dent. Various subsidiary means may doubtless 
be employed with advantage, such as injections 
and physical and chemical agencies; but the 
method which of all others is the least liable to 
admit of erroneous interpretations by the ad- 
mixture of artificial elements in which the mind 
of the inquirer has had a share, is that of em- 
loying a power capable of reaching the utmost 
imits of organization, on examples the most 
ne approaching to their natural state during 
e. 
There is perhaps no one line of inquiry in 
the whole range of minute anatomy so beset 
with difficulties and sources of error, and 
therefore so much demanding a cautious study 
and sagacious discrimination between conflict- 
ing appearances, as this of the structure of the 
striped fibre. The following description is 
substantially the same as that published by me 
in the Philosophical Transactions, 1840, and 
which all my subsequent observations have 
tended to confirm. To that paper I would 
venture to refer those who may desire to enter 
at greater length upon the grounds of the view 
here summarily given. 
1. Length.—This varies exceedingly in dif- 
ferent muscles. The sartorius, the longest in 
the body, often surpasses two feet in length, 
_ and the individual fibres are as long, extending 
_ in parallel bundles from end to end. In many 
others they do not exceed a quarter of an inch ; 
_ thus their greatest variety is presented in their 
length. 
\ 2. Thickness—This should be examined in 
_ the uncontracted state of the fibre, which for 
this purpose should be removed from the body 
after all contractility has departed. I have 
elsewhere* given a table of numerous compa- 
tative measurements in various animals, and 
subjoin the following abstract : — 
Diameter of the elementary fibres of striped 
muscle in fractions of an English inch. 
From to 
Human ...... gts is, average of males 555 
» females 4, 
‘ 
y 
Other Mammalia phy ts, average ...... shy 
ds ..seeeee hp Meh xdeeres ahr 
Re CHES o> ois.e.s Toy hoe ” eeeeee ht 
ee as a ” cescee ah 
Insects cans aes ae cee Rais rns a5 
oe Dy ” 
I believe that the fs diameter of the 
fibres in the human female is upwards of a 
fourth less than in the male, and that the ave- 
= of both together is greater than that of 
other Mammalia; but a more extensive exami- 
nation is requisite to establish this. Fish have 
fibres nearly four times thicker than those of 
_ Birds, which have the smallest of all animals. 
_ Next to Fish come Insects, then Reptiles, then 
Mammalia. In each of these different classes, 
however, an extensive range of bulk is observ- 
able, not only in the different genera, but in the 
me animal and the same muscle, some fibres 
ing occasionally three, four, or more times 
* Philosophical Transactions, 1840, p. 460. 
507 
the width of others. In general the fibres of 
the heart are smaller than those of other striped 
muscles. The varieties in the average bulk in 
different classes have a close connection with 
differences of nutrition and of their irritability, 
which will be reverted to. 
3. Figure.—This is subject to some variety, 
depending on their number and manner of 
package. Sometimes, as in some parts of In- 
sects, they are flattened; but when they are 
isolated, or loosely aggregated, they are more 
or less cylindrical. In all the cases, however, 
where many fibres are arranged side by side, 
as in the Vertebrata, the larger Insects, and 
Crustacea, they are irregularly polygonal, the 
contiguous sides being flattened, evidently from 
the effect of package. Yet some interspaces 
are always left for the passage of bloodvessels, 
nerves, and areolar tissue among and _be- 
tween them. Their form may be most readily 
displayed by a transverse section of a muscle 
that has been dried en masse, as long ago shown 
by Leeuwenhoeck (fig. 286). 
4. Colour——The colour of muscle depends 
partly on the colour of its elementary fibres, 
partly on the blood contained in its vessels, 
and there is strong reason to believe that the 
colouring matter of both is the same, or nearly 
so. That the fibres have always a colour of 
their own is at once evident on inspection 
under the microscope. It is generally more or 
less of a reddish-brown, but varies much in 
different animals and in different muscles, and 
even in the same muscle according to its state 
of development and activity. In Reptiles and 
Fish generally, and in Crustacea, the flesh is 
white, sometimes pinkish, but in some fishes, 
as the Gurnard, the gill-muscles are red. These 
varieties of colourare attended with none of struc- 
ture. In Birds the colour varies much, being 
often white and deep red in the same animal, but 
generally the pectoral muscles are very dark. 
Transverse sections of striped muscle that had been 
injected and dried, magnified 70 diameters. 
A, from the Frog. 
B, from the Dog. ; 
a, a, section of elementary fibres, shewing their 
angular form and various s:ze. 
b, b, sections of the injected capillaries, shewing 
the position they occupy among the fibres. 
These figures shew th greater vascularity of the 
muscle with the narrower elementary fibres. 
