TO THE ELEMENTAET EIBEES OE STEIPED MTJSCLE. 
897 
but these lines may often be seen to divide and subdivide into several very fine fibres, 
which may run with the prolongation of the dark-bordered fibre, or at once diverge 
from it (Plate XLIII. figs. 17, 18, & 19 ; Plate XLIV. fig. 31). 
Not imfrequently very fine fibres can be traced external to what appears to be the 
outline of the sheath of the nerve, and these form, with the fine fibres already described, 
a ‘ pale fibre.’ The band or pale fibre divides into smaller bundles, and the fibres com- 
posing them gradually become so fine as to be invisible. Nuclei exist in connexion with 
the finer fibres which I have described, as well as in connexion with the prolongations of 
the dark-bordered fibres (Plate XLII. figs. 13, 14, & 15). Here, as elsewhere, some fibres 
appear to be connected with the nucleus, while others pass round it on one side (Plate 
XLI. figs. 2, 3 c). Sometimes fibres pass on both sides of the nucleus. The pale bundles 
of very fine fibres often give off branches, and these again divide into finer bundles, pro- 
ducing the appearance of a network (Plates XLII. & XLIII. figs. 13, 14, 15, 16, & 17), 
the meshes of which vary much in diameter. Very often several nuclei are seen at 
the point where the dark-bordered fibre divides. A very confused appearance often 
results from the number of nuclei and fibres. As already stated, in specimens examined 
in aqueous fluids which do not refract highly, it is not possible to trace the course of 
the separate bundles of fibres and their connexion with the nuclei ; but in specimens 
mounted in glycerine, examined with high powers, the bundles of fine fibres can be 
separated from each other and followed (Plate XLIII. fig. 21). Some appear to come 
from the sheath, or are external to it; and others result from the division of the dark- 
bordered fibre (Plates XLII. & XLIII. figs. 15 & 17). The nuclei and fibres can be very 
readily demonstrated near the trunks of the dark-bordered fibres, and the network can 
often be seen in the same situation, but it is not easy to trace the course of the delicate 
fibres over the muscular fibres for any great distance. The large nerve-fibres prevent the 
finer ones from being ruptured; but at a distance from the coarse fibres, there being nothing 
to protect them, the very delicate fibres are generally destroyed by the necessary mani- 
pulation, or rendered invisible by the pressure of the thin glass. I have, however, seen 
such a network very distinctly on the side of some muscular fibres, upon which numerous 
branches Lorn an adjacent nerve could be traced at intervals for the distance of about 
one-hundredth of an inch. Indications of the existence of such a network (the nuclei 
being perfectly distinct) are not unfrequently seen in many parts of the same elementary 
fibre. Nuclei and fine fibres, resembling those which have been shown to be in connexion 
with nerve-fibres, can often be seen just at the edge of a muscular fibre, and very fre- 
quently a true nerve can be traced, running for some distance near a capillary, and giving 
off branches with nuclei which are gradually lost on the surface of the muscle or 
amongst the connective tissue. As these branches pursue the course described, they can 
hardly be vascular nerves ; and there are besides them other branches which lie closer to 
the vessel, which are probably of this nature. The distribution of very fine fibres can 
sometimes be traced by the course of the nuclei. In certain cases, in which no fibre 
connecting nuclei can be detected when the specimen is first prepared, a fibre afterwards 
MDCCCLXII. 6 G 
