478 
MR. BOWMAN ON THE MINUTE STRUCTURE AND 
to form transverse lines, are yet deranged with so much regularity of gradation, 
that other series of lines are produced, of very beautiful curvatures, not unlike, in 
general characters, the appearance of engine-turned chasing, though less uniform, 
and undergoing the most varied changes with every alteration of the focus. These 
elegant curves are seen all through the protruding mass, and clearly demonstrate the 
manner in which the true striae are composed. The mode in which the sarcolemma 
gives way is worthy of particular attention. The rupture having taken place, does 
not extend in any one direction more readily than in another, but only enlarges so 
much as to give a bare passage to such fibrillae as force their escape, and generally 
remains so small as considerably to constrict the base of the hernia. The hernise 
are usually, therefore, several in number, each consisting only of a few fibrillae, and 
the opening in the sheath assumes a round or oval figure. From this circumstance, 
no small degree of toughness may be attributed to the sarcolemma. So extreme is 
the thinness and transparency of this membrane, that it is difficult to form any de- 
cided opinion as to its structure ; but it would seem not improbably to consist of a 
very close and intricate interweaving of threads, far too minute for separate recogni- 
tion. Having at least sometimes discerned in it an appearance not unlike what would 
result from such a texture, I am induced to conjecture so, but the matter is very 
doubtful. Its external surface seems to be quite smooth and free, being in contact 
with the capillary and cellular network of the organ, which embraces each fasciculus, 
in more or less profusion, according to the animal, and the particular muscle. I have 
never as yet seen any appearance which could give countenance to the opinion that 
either nerves or vessels penetrate among the fibrillae, and 1 am induced to believe 
that no capillary vessel ever perforates the sarcolemma, which seems to constitute 
an effectual barrier between the parts within and those without. The inner surface 
of the sarcolemma often presents irregularities, as if some attachment of the fibrillae 
to it had existed ; but it never bears upon it the smallest mark of the transverse striae, 
or of any regular marking, unless, as does occasionally happen, some few fibrillae, or 
parts of them, remain adherent to it. But this very rarely happens, the whole of the 
fibrillae usually evincing a greater facility of separation from the sheath than from 
one another. A few are seen thus adhering in fig. 75. 
The inner surface of the sarcolemma, however, is naturally adherent to the outer- 
most fibrillae, and most probably in a particular manner*. From some appearances 
frequently presented by the fasciculi of insects at their margins, and of which an ex- 
ample is given in fig. 70 . a, it would appear that this adhesion takes place to the most 
prominent parts of the fibrillae, or, in other words, to the rims of the transverse discs 
which result from their union. The outer scolloped line in similar cases has no doubt 
been often mistaken for the outer margin of the fibrillae. It is, in fact, indicative of 
the bulging sarcolemma, which is bound down to the prominent extremities of the 
* [Schwann seems to regard the sheath as unadherent to the proper muscular tissue (Untersuchungen, 
p. 166.), an opinion which the following considerations show to be erroneous.] 
