DR. MARTIN BARRY ON FIBRE. 101 



52. A flattening of " segments " or " particles " in the contraction of muscle-f-, 

 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, a, 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 J. And he ap- 

 pears to have figured as bead-like segments , what I consider the overlapping parts 

 of spiral threads. 



585. 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 

 (" 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, j3, 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 ^f. 



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 



t BOWMAN, /. c., pp. 493, 494. J Ibid. /. c., p. 470. L. c., fig. 10 b, e.fig. 11. 



|| " Elements of the General and Minute Anatomy of Man and the Mammalia." Fig. 83. Explanation of 

 the Plates, p. 35. 



^f This paragraph was communicated to the Society as a Postscript, Jan. 11, 1842. 



