DR. MARTIN BARRY ON FIBRE. 
101 
52. A flattening of “ segments ” or “ particles ” in the contraction of muscle-}*, 
therefore, seems not to be required : and indeed I have in no instance met with seg- 
ments or particles, which could undergo this change in form. But fig. 66. affords 
proof that the change contended for really takes place ; this figure exhibiting the ap- 
pearance of two parts of the same fasciculus, that were actually seen ; the one, «, being 
in a contracted, and the other, (3, in a relaxed state : and the difference between these 
two conditions, was seen to result from a difference in the direction of the spirals. 
At one part, a, the fasciculus being shortened, the spaces (striae) between the curves 
of the spirals were made smaller, and the fasciculus was thick. At the part (3, the 
fasciculus being lengthened, the spaces (striae) between the curves of the spirals were 
made greater, and the fasciculus was thin. 
53. The edges of the flat filaments (“ fibrillae ”) in voluntary muscle being directed 
towards the observer, the flat surfaces of these filaments are in contact with one an- 
other (except where septa intervene, par. 42). And those parts of the spirals of two 
filaments, so in contact, fit together with the most perfect exactness and regularity, 
appearing to overlap one another, as viewed in situ. The adjacent parts of spirals 
thus glide harmoniously into a change of place. It will be seen that the view of a 
recent author, in regard to “ segments,” was of this kind ; but then he found it need- 
ful to suppose adhesion of the segments in some way to one another^. And he ap- 
pears to have figured as bead-like segments §, what I consider the overlapping parts 
of spiral threads. 
53^. Many of the drawings that accompany the memoir (figs. 58, 59, 65, 93 — 95) 
show that there are states of voluntary muscle, in which the longitudinal filaments 
( cc fibrillae ”) take no part in producing the transverse striae ; these striae being caused 
by the windings of spirals, within which very minute bundles of longitudinal filaments 
are contained and have their origin. The spirals are interlaced (fig. 64 a, (3, y). When 
mature, they are flat and grooved filaments, having the compound structure above de- 
scribed. With the shortening of the longitudinal filaments (“fibrillae”) in muscular 
contraction, the surrounding spirals — and of course the striae — become elongated and 
narrow: while in relaxation, these changes are reversed. The “convoluted fila- 
ments” regarded by Gerber as “ enigmatical ||,” were evidently no other than dis- 
torted spirals 5[- 
54. The spiral form of the ultimate threads of muscle, above described, will I think 
elucidate several facts already known, but as it appears to me, not satisfactorily ex- 
plained. Thus, for instance, combined as I find these spiral threads of muscle, and 
situated one within the other, there cannot well be much difference in their lengths, 
when the fasciculus is broken off. Hence in part, probably, it is that the fasciculus 
f Bowman, l. c., pp. 493, 494. J Ibid. 1. c., p. 470. § L. c., fig. 10 b, c, fig. 11. 
|| “ Elements of the General and Minute Anatomy of Man and the Mammalia.” Fig. 83. Explanation of 
the Plates, p. 35. 
If This paragraph was communicated to the Society as a Postscript, Jan. 11, 1842. 
