892 
PEOFESSOE BEAEE ON THE DISTEIBUTION OE NEEVES 
very long course, gradually become finer by division, and at last terminate in a lax net- 
work of fine fibres which pass in and out between the muscular fibres ; while some of 
the subdivisions are distributed to the elementary muscular fibres, like the set of fibres 
first alluded to. It appears, therefore, that in various parts of the muscle, not merely 
near its centre, but also on some of the fibres near their insertions, branches of dark- 
bordered fibres can be seen to become suddenly attenuated and give ofi“ very fine fibres 
which divide and subdivide on the surface of the sarcolemma, becaming gradually finer 
until lost, or they leave the surface of the elementary fibre and are lost in the inter- 
muscular connective tissue — and other fibres, which gradually become attenuated and, 
after very numerous divisions, terminate in a network of fine fibres which may be traced 
for a long distance amongst the fibres of connective tissue, between or upon the ele- 
mentary fibres. Many of the bundles of dark-bordered fibres above alluded to can 
only be detected in well-prepared specimens which have been soaked for some time in 
glycerine, so that the muscular fibres may be separated if om each other without rupture 
of the nerve-fibres or capillaries. 
Again, numerous branches of nerve-fibres, composed of two, three, or four dark-bordered 
fibres, may be seen ramifying and dividing near the tendinous extremities of the muscular 
fibres of the mylo-hyoid muscle of the frog. Several branches can be followed from 
the central tendon as far as the central part of the fibres ; and often very fine fibres can 
be seen passing amongst the fibres for some distance and forming networks or plexuses. 
But there is another fact against the view that the nerves are distributed to only a 
very small portion of the elementary muscular fibres of the frog. In certain parts of 
the pectoral muscle new muscular fibres are being developed, as Kollikee has men- 
tioned, and here in a comparatively small space may be seen elementary fibres varying 
very much in length and diameter. The thickest of these narrow fibres, according to 
my measurements, are often not more than the 2W^th of an inch in T^fidth, and the 
thinnest not more than the th of an inch in diameter : some are as loner as the 
other muscular fibres ; but often single spindle-shaped fibres with two or three nuclei, or 
more elongated fibres the nuclei of which have divided so as to form a row of perhaps 
ten or more, may be found. A large nerve-fibre, generally composed of two large daik- 
b ordered nerve-fibres in the same sheath, with finer fibres, can be followed to the oval 
swelling situated amongst the ordinary muscular fibres ; and one or two dark-bordered 
fibres leave the swelling to be distributed on more distant muscular fibres. The dark- 
bordered fibres divide, and their branches pursue a very tortuous course in the oval 
swelling, so that one cannot be followed for any great distance ; but fine fibres may be 
seen passing in either direction, and running parallel with the thin growing muscular 
fibres. Not unfrequently I have seen these nerve-fibres become so fine that they cannot be 
followed far ; but their course can be traced by their nuclei for a considerable distance. 
In many instances branches of other nerve-fibres pass to these narrow muscular fibres at 
a point between the oval swelling and the points of insertion of the fibres. The oval 
swelling itself consists of very young muscular fibres in various stages of development, 
