CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TISSUE. 321 
But it may well be asked, What about the action of staining 
agents, such as logwood, which is stated to tint the dark stripe 
and Dobie’s line? Does this not show a difference of structure 
along the fibres ? 
Once having the clue it will be understood that just as the 
unstained fibre will modify and change the direction of rays 
passing through it, so will also a stained fibre produce what are 
apparently modifications of the staining effect. It is generally 
stated that the dark band and Dobie’s line are stained by log- 
wood and carmine, while the bright bands remain unaffected ; 
also that Hensen’s stripe in the centre of the dark stripe is 
stained only to a slight degree; whence it follows that if stain- 
ing action is to be the criterion, this stripe differs in structure 
from the dark stripe. 
We, however, affirm that the whole fibre is stained, and 
equally stained throughout. The bright band is undoubtedly 
stained, although it appears not of the deep blue of the dark 
stripe when coloured by logwood; and this conclusion is drawn 
not only from an examination of my own specimens, but also 
from some of great beauty shown to me by Dr. Klein. Why 
the bright band does not appear of so dark a blue is, that the 
apparent shading of the latter is added to the blue tint, pro- 
ducing a depth of colour. The most conclusive proof of this is, 
that one can often reverse the colouring on readjusting the 
focus, and that Hensen’s stripe or the bright part of the dark 
stripe is only of a faint light blue, like that of the bright stripe. 
Picric acid stains muscle very readily, and colours it through- 
out. The fibre to the naked eye is yellow and uniformly 
so, but when examined by the microscope, alternating yellow 
and shaded yellow bands are to be observed, which reverse 
their position on changing the focus. With a high focus— 
when the crests are bright in the unstained preparation—they 
are of a bright yellow, while the valleys are of a deeper yellow 
tint. 
To show the effects which a fibre of this shape can produce 
when transmitting monochromatic light, nothing can be more 
conclusive than the following experiment :—A slip of coloured 
blue glass is held obliquely between the reflector and the stage 
of the microscope, so that blue rays pass through the fibre. It 
does not appear of a uniform tint, but beautiful blue stripes ase 
seen corresponding with the crests and valleys, and varying with 
alterations of focus. If a piece of red glass be substituted for 
the blue slip, red cross stripes are seen in corresponding places. 
my explanation of the markings, they re-examined their specimens (which 
T have also seen), and found that when the stris were visible there, and 
only there, the fibre was ampullated, (See Fig. 5.) 
