396 Dr Martin Barry on Fibre. 
brane discovered by Schwann, but for the only complete description of 
which, in a formed state, we are indebted to Mr Bowman. The inner 
spirals constitute what are denominated the fibrille. The fibril appears 
to the author to be no other than a state of the object which he designates 
a flat filament ; and which, as he shews, is a compound structure. The 
fibril he finds to be, not round and beaded, as it has been supposed, but 
a flat and grooved filament ; the description above given of the structure 
of the filament being especially applicable here. This flat filament is so 
situated in the fasciculus of voluntary muscle, as to present its edge to 
the observer. It seems to have been the appearance presented by the 
edge of this filament, that is to say, by the curves of a spiral thread, that 
suggested the idea of longitudinal bead-like enlargements of the fibril, 
as producing strize in the fasciculus of voluntary muscle. In the au- 
thor’s opinion, the dark longitudinal strize are spaces (probably occupied 
by a lubricating fluid) between the edges of flat filaments, each filament 
being composed of two spiral threads, and the dark transverse strize rows 
of spaces between the curves of these spiral threads. The filament now 
mentioned, or its edge, seems to correspond to the primitive marked thread 
or cylinder of Fontana—to the primitive jibre of Valentin and Schwann— 
to the marked filament of Skey—to the elementary fibre of Mandl—to the 
beaded fibril of Schwann, Miiller, Lauth, and Bowman—and to the gran- 
ular fibre of Gerber. The changes known to be produced by the alter- 
nate shortening and lengthening of a single spiral are exhibited in the 
microscope by a fasciculus of spirals, not only in its length and thick- 
ness, but in the width of the spaces (stri@) between the eurves of the 
spirals. And a muscle being no other than a vast bundle of spirals, it is 
in contraction short and thick ; while in relaxation it is long and thin ; 
and thus there occurs no flattening of bead-like segments in contraction. 
The author has found no segments that could undergo this change. These 
observations on the form of the ultimate threads in voluntary muscle, 
were first made on the larva of a Batrachian reptile ; and have been con- 
firmed by an examination of this structure in each class of vertebrated 
animals, as well as in the Crustacea, Mollusca, Annelida, and Insects. 
He finds that the toothed fibre, discovered by Sir David Brewster in 
the crystalline lens, is formed out of an enlarged filament ; the projecting 
portions of the spiral thread in the filament, that is, the apparent seg- 
ments, becoming the teeth of that fibre. 
The compound filaments are seen with peculiar distinctness in the 
blood-vessels of the arachnoid membrane. In connexion with the spiral 
direction of the outer filament in these vessels, the author refers to the 
rouleaux in which the red blood-dises are seen to arrange themselves, in the 
microscope, as probably indicating a tendency to produce spiral filaments. 
To form rouleaux, corpuscle joins itself to corpuscle, that is to say, ring 
to ring: and rings pass into coils. The union of such coils, end to end, 
would form a spiral. But the formation by the blood-corpuscles of these 
rouleaux is interesting in connexion with some facts recorded by the au- 
