TO THE ELEMENTAET FIBEES OF STEIPED MUSCLE. 
895 
fibres and definite dark-bordered fibres has been demonstrated in many situations 
(tongue, heart, peritoneum, muscular fibre, and very clearly indeed in the bladder of the 
frog). I have convinced myself that in many of the ganglion-cells of the frog (abdominal 
cavity, ganghon on posterior roots of the nerves, heart, bladder) one fibre springs from 
the central part of the cell, while other fibres are in connexion with its circumference. 
The latter fibres very frequently are arranged spirally around the central fibre. As 
already stated, many of the finest fibres are less than the of an inch in diameter. 
It will be said that these fine fibres are composed of connective tissue ; but I shall show 
that the fibres resulting from the subdivision of those which are the direct continuations 
of the dark-bordered nerve-fibres exhibit the same characters, and can be distinguished 
from the fine fibres of yellow elastic tissue. Very many fine fibres which are undoubted 
nerve-fibres, and which form plexuses and networks, have altogether escaped observa- 
tion, and their nuclei have hitherto been considered as belonging to the connective tissue. 
The fine ner\"e-fibres I have described cannot be seen in specimens immersed in water, 
or in solutions which refract like water. 
The Division and Subdivision of the Darh-bordered Fibres. 
The numerous dmsions and subdivisions of the dark-bordered nerve-fibres have been 
described and figured by various observers ; but it is necessary to give new drawings of 
some of these fibres, as their arrangement has not been accurately delineated, and the 
presence of vefry fine nerve-fibres in the sheath external to the white substance has not been 
admitted. Fig. 11, Plate XLII. shows that the dark-bordered fibres, even in the trunks, 
may become so thin as scarcely to be visible as distinct fibres by the ^^th of an inch object- 
glass. One of the fibres resulting from the division of a may be traced towards the 
right, and at d becomes so thin that it might be easily overlooked, and if recognized 
would be regarded by most authorities as a fibre of connective tissue in the sheath of the 
ner\'e. 
Often a fibre resulting from the subdivision of a dark-bordered fibre is seen to pass 
towards another dark-bordered fibre, and run parallel with it for some distance. This 
arrangement, which exists in the larger fibres, and which is figured in my last paper, is 
also observed in the finer ramifications. The terminal dark-bordered fibre very gradually, 
or more or less abruptly, becomes finer, and divides into two fine fibres ; but there is no 
termination or cessation of the white substance, as described by Kuhne, who states that 
the white substance ceases at the sarcolemma, while the axis cylinder only is continued 
onwards as a pale fibre beneath the sarcolemma. Kollikee states that, “ besides the 
axis cylinder, they are furnished with a prolongation of the membranous sheath ; indeed 
I have seen this so clearly in a great many favourable instances, that I can have no doubt 
on the point But whilst it is easy in most cases to perceive the membranous 
sheath and its enclosed matter distinct from each other at the commencement of the 
pale fibres, yet in their further progress these structures coalesce together, and the 
terminal fibres then appear as uniform pale filaments.” 
