466 
MR. BOWMAN ON THE MINUTE STRUCTURE AND 
dinal lines, taking the direction of the fasciculi, these lines being here and there ex- 
ceedingly strong and decided, and leaving but a very narrow light streak between 
them. In other parts they are fainter, but always parallel, unless the fibrillae are bent 
by violence from their course, in which case they seem to be easily disarranged, as 
though their lateral connexion with one another were but slight. The striae upon 
these fasciculi are very delicate, and quite regular, if the parallelism of the fibrillae be 
preserved ; but where this is disturbed, the striae are, as it were, broken to pieces, and 
the individual fibrillae which they crossed, bear upon them the disarranged fragments 
of the markings of which they consisted. Either the striae or these markings are 
everywhere clearly visible, except about the very thick longitudinal dark lines de- 
scribed, where they are always faint, sometimes undistinguishable ; a fact which 
seems sufficiently explained by the presence of those lines absorbing and obscuring 
by their depth the very delicate striae that cross them at right angles ; and except also 
where a slight and irregular obliquity of the fibrillae causes so complicated an inter- 
ference of the longitudinal lines among the cross markings of each, that these last, 
being the faintest, are only here and there apparent*. The fibrillae, however, are in 
general readily spread abroad at the extremity of a fasciculus, and there uniformly, 
when not too much injured or obliquely overlapping each other, present the markings 
well defined. Indeed, some of the most beautifully marked fibrillae that I have seen 
have been such as I now speak of, hanging out from the end of a fasciculus taken from 
one of these fishes. In these also, as in other animals, I have frequently by accident 
obtained a view of the interior of a fasciculus, and observed every fibrilla to be marked. 
By maceration it is not difficult to obtain the fibrillae entirely detached, and in these 
the correctness of Mr. Skey’s remark may seem at first sight to be partially borne 
out, for in many of them it is impossible to detect any appearance of a marked struc- 
ture. In many others, on the contrary, this structure is evident enough ; and by 
attention to the mode and degree of illumination, I have frequently succeeded in 
discerning the regular markings, though very faint, on fibrils which appeared before 
to be decidedly cylindrical. The fact seems to be, that in these fishes the distinction 
between the light and dark points is not so clear as in most other cases; and their 
colour being at the same time very light, the extreme tenuity of the ultimate fibrillae 
does not always allow of their showing individually the markings, which are visible 
enough when in juxtaposition with one another. It may therefore be concluded, 
that they form no exception to the general fact, that all the fibrillae of voluntary 
muscle possess the markings which we are now considering. 
Secondly, the fasciculi are not tubular, but consist of a true bundle of fibrillae. In 
the preceding observations a certain amount of proof has been offered in illustration 
of this point; it having been shown that accidental wounds frequently display the 
interior of the more bulky fasciculi, and demonstrate their composition by fibrillae ; 
* These appearances, though in a less degree, are not uncommonly seen in disturbed fasciculi of the muscles 
of other animals, and they are undoubtedly very deceptive. 
