908 
PEOFESSOE BEALE ON THE DISTEIBTJTION OE NEEYES 
specimen results from the slow action of acetic acid. This figure, and figures 
6, 8, & 9, show the relation of the fine fibres to the nuclei. X 1700. 
Fig. 8. Another terminal ‘ extremity ’ of a dark-bordered fibre. A similar fibre {a) is seen 
external to the dark-bordered fibre, as in the last and also in the next specimen. 
Four nuclei are seen, which exhibit their relation to the bundles of fine fibres, 
Fig. 9. Another terminal portion of a dark-bordered fibre. In figs. 7, 8, & 9 a nucleus 
is seen in the dark-bordered fibre as well as in connexion with the pale 
fibres. Figures 6, 7, 8, & 9 are from the bladder of the frog. 
Fig. 10. Portion of muscular fibre from the leg. Several dark-bordered fibres are seen 
enclosed in the same sheath ; and many of these are exceedingly thin, but evi- 
dently possess the same structure as the ordinary dark-bordered fibres. x700. 
PLATE XLII. 
Fig. 11. Dark-bordered fibres. The nucleated dark-bordered fibre a is seen to divide 
into two branches. The one passing in the division which diverges to the 
right, rapidly becomes so very fine that it can hardly be followed as it rmis 
parallel with another dark-bordered fibre and in the same sheath with it 
(under d). This very fine fibre, in direct continuity with the dark-bordered 
fibre, cannot be distinguished from the fine fibres seen in the sheath of the 
nerve on the left side of the specimen (at h), which leave the trunk and assist 
in forming a separate branch at c. From the pectoral. x700. 
Fig. 12. Division of dark-bordered fibre in the central part of the pectoral muscle of the 
frog. The fine fibres resulting from its subdivision may be followed for a 
considerable distance. Nuclei are connected with them at intervals, and the 
fibres are arranged to form a network. A more perfect example of this 
arrangement is represented in figure 43 (not published). This figure shows 
the course of the very fine fibre which is directly continuous with the dark- 
bordered fibre in certain cases. X 700. 
Fig. 13. Division of dark-bordered fibres on the surface of a muscular fibre, fi’om the 
central part of the pectoral muscle. The muscular tissue having been removed 
from the tube of the sarcolemma, the delicate nerve-fibres can be distinctly 
seen on the external surface of this transparent membrane. The pale granular' 
fibres, which are here and there connected by branches so as to form networks, 
are composed of the delicate fibres which are the immediate continuations of 
dark-bordered fibres {a and h), and of finer fibres which are derived fi'om those 
ramifying in the sheath or external to it. Nuclei are connected with these 
fibres. x700. 
Fig, 14. Division and subdivision of fine dark-bordered fibres on the sui’face of muscular 
fibre, showing numerous fine fibres arranged in the form of a network, and 
nuclei. Two or three of the delicate compound nerve-fibres may be traced 
quite to the edge of the muscle. Pectoral muscle. x700. 
