148 Proceedings of Royal Society of Edinburgh. 
clear segment, is seen between Bowman’s element and the inter- 
mediate segment, when the uncontracted fibril is stretched to its full 
physiological length. It is almost quite clear, and appears to con- ! 
sist of a thin envelope containing a watery fluid, and a particle of 
myeloid substance belonging to the granule line described by Flogel 
as crossing the fibre in the light stripe. The whole fibril has a 
thin envelope. 
The first event of contraction consists in a shortening of the in- 
terval between the ends of Bowman’s elements, which in their 
approximation come close to the globule of Dobie’s line. The 
shortening appears to result from an active absorption of fluid from 
the clear and intermediate segments by Bowman’s elements. In 
the second stage of contraction the fibril seems " homogeneous,” 
unless it is suitably stained and sufficiently magnified. In this 
so-called “homogeneous” stage the ends of Bowman’s elements are 
in close proximity to the globule of Dobie’s line, which is now 
somewhat flattened ; the myeloid substance has not yet begun to 
shift its place in Bowman’s element. In the third stage of con- 
traction the myeloid substance moves away from the shaft on each 
side of the equatorial node in Bowman’s element, accumulates in 
its ends, and the element shortens, owing to a real contraction of 
its tissue. There is a “ reversal of the stripes” in the contracted 
fibre, as Flogel first pointed out. The dim stripe of the contracted 
fibril consists of the approximated ends of two Bowman’s elements 
with the myeloid globule of the intermediate segment between them, 
now much flattened, owing to lateral extension by the thickening 
of the contracted fibril. The light stripe of the contracted fibril 
consists of the shaft of Bowman’s element that has become clear, 
owing to shifting of the myeloid substance to the ends of the 
element. The myeloid substance appears to be completely moved 
to the ends of Bowman’s elements only when their shafts contract 
and squeeze it out ; but it begins to move out of the shafts before 
they contract. The fluid absorbed by the element probably passes 
into the interstices of the micellar network; the myeloid substance 
appears to be contained in a special set of spaces. The contraction 
of the micellar network does not express the absorbed fluid, which 
therefore does not leave Bowman’s element until its contraction is 
over. The elasticity of Bowman’s element and of the intermediate 
