58 QUARTERLY CHRONICLE. 
at the same time the spiral arrangement of the cross bands 
allows of their elongation and contraction upon themselves 
A A, Longitudinal bands; BB, Transverse spiral bands (both coloured by 
carmine); C C, Interspaces with dark border from shade cast by transverse 
bands. 
without any stretching or pulling of the delicate substance of 
which they are composed. 
‘That there are open spaces between the horizontal bands 
appears to me certain from the appearance of the parts, and 
from the fact that the contractile tissue—and, in fact, all the 
structures of the body—may be stained with carmine, but 
these interspaces never show the slightest appearance of any 
colour, their hue in many specimens being exactly similar to 
that of the field of the microscope where no tissue intervenes 
between it and the lamp used for illuminating the object. 
What, then, is the meaning of the perpendicular and _ hori- 
zontal lines noticed in a specimen of muscular fibre when 
examined by a quarter or twelfth of an inch glass? The per- 
pendicular lines may be produced either from the line of union 
of two primitive fibres or from the creasing of the sarcolemma 
or the fibrous case, which encloses a bundle of fibres; but an 
isolated primitive fibre, when examined under a high power, 
presents no appearance of longitudinal striation, provided its 
fibrous case and sarcolemma have been destroyed or rendered 
too transparent to be seen. ‘The dark cross lines are caused 
by the shadows cast upon the open spaces, or by the approxi- 
mation of two horizontal bars; under a high power these 
dark spaces may be resolved into two dark lines bordering the 
horizontal bands and an interspace of a very much lighter 
