38a 
B. MELLAND. 
The contracted part of the fibre is widened out transversely 
and the distance between the transverse networks diminished. 
The series of haloes round the rows of dots extends to the 
whole of the now diminished interval between the successive 
rows. There is consequently a bright band in the position 
usually occupied by the dim band. Traversing this bright 
band longitudinally are seen fine lines joining the dots of 
adjacent networks. Between this fully contracted and the 
relaxed part of the fibre is the portion showing the “ homo- 
geneous stage ” of Engelmann. The transverse marking is 
here to a large extent lost, and this can be easily understood, 
when we consider that at the onset of contraction the trans- 
verse network would be probably more or less pulled out of 
shape. The individual dots would no longer lie in the same 
transverse plane, and hence the haloes would not blend into a 
continuous bright transverse disc. This agrees with the fact 
mentioned by Schafer, 1 that mechanical shifting of the elements 
of a fibre causes a disappearance of the transverse striations. 
Another point often observed in osmic acid preparations is 
a caving in of the sarcolemma between each transverse net- 
work, that is opposite the dim stripe. In other preparations 
usually the sarcolemma bulges at these points, and appears to 
be contracted at its attachment to the transverse network or 
Krause’s membrane. This may be explained if it be supposed 
that in osmic acid preparations there is a certain amount of 
contraction of the matrix or sarcous substance, by exosmosis 
for instance. The sarcolemma will follow this decrease in bulk 
but will be prevented from doing so at those points where it is 
held outwards by the more rigid transverse networks. 
IY. The Living Fibre. 
The fibres from the leg of Dytiscus, or the bee, mounted 
without the addition of any fluid, and examined whilst fresh 
or living, give the appearances seen in figs. 19 and 20. Most 
of the fibres are seen to present the appearance of alternate 
dim and bright bauds, the dim bauds being the thicker. Each 
1 ‘ Quaia’s Anat.,’ vol. ii, 9th edition, p. 129. 
