MUSCULAR TISSUE. 183 
This much is readily seen in a specimen of muscular 
fibre taken from any part of the body, and whether alive 
or dead. But the results of the ultimate optical analysis 
of these appearances, and the conclusions respecting the 
normal structure of striped muscle which may be legiti- 
mately drawn from them, have been the subjects of much 
controversy. 
Quiescent muscular fibres from the chela of the forceps 
of a crayfish, examined while still living, without the 
addition of any extraneous fluid, and with magnifying 
powers of not less than seven or eight hundred diameters, 
exhibit the following appearance. At intervals of about 
1-4000th of an inch, very delicate but dark and well- 
defined transverse lines are visible ; and these, on careful 
focussing, appear beaded, as if they were made of a series 
of close-set minute granules not more than 1-20,000th 
to 1-80,000th of an inch in diameter. These may be 
termed the septal lines (fig. 52, D and E,a; C,1—5; 
fig. 58, s). On each side of every septal line there 
is a very narrow perfectly transparent band, which may 
be distinguished as the septal zone (fig. 58, sz). Upon 
this follows a relatively broad band of a substance which 
has a semi-transparent aspect, like very finely ground 
glass, and hence appears somewhat dark relatively to the 
septal zone. Upon this inter-septal zone (is) follows 
another septal zone, then a septal line, another septal 
zone, an inter-septal zone, and so on throughout the 
whole length of the fibre. 
