MUSCULAR TISSUE. 18o 



This much is readily seen in a specimen of muscular 

 fibre taken from any part of the bod^-, 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 

 controvers}'. 



Quiescent muscular fibres fi'om the chela of the forceps 

 of a crayfish, examined while still living, without the 

 addition of any extraneous fiuid, and with magnifying 

 powers of not less ihan seven or eight hundred diameters, 

 exhibit the following ai:)i)earance. At intervals of about 

 l-4000th of an inch, ver}^ 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 1-30, 000th of an inch in diameter. These may be 

 termed tlie septal lines (fig. 52, D and E, a; C, 1 — 5 ; 

 fig. 53, s). On each side of every septal line there 

 is a very nari'ow perfect!}' transparent band, which may 

 be distinguished as the septal zone (fig. 53, sz). Upon 

 this follows a relativeh' broad band of a substance which 

 has a semi-transparent aspect, like verj' finely ground 

 glass, and hence appears somewhat dark relatively to the 

 sei)tal zone. Upon this inter-scptal zone {i s) follows 

 another septal zone, then a septal line, another septal 

 zone, an inter-septal zone, and so on throughout the 

 whole length of the fil)rt. 



