DR. MARTIN BARRY ON FIBRE. 103 



to be in operation in the blood-corpuscle at certain periods-}-, and in tables of the epi- 

 thelium J. To meet with a re-appearance of anything like this process, however, in 

 spiral fibres, I was not prepared. Yet here also, something of the kind is actually 

 seen. For, as above described, within the space circumscribed by the windings of a 

 larger spiral, there arise smaller ones, which are sometimes two in number. There 

 is, besides, another way in which the process just referred to re-appears. A spiral, 

 originally single, gives origin to others in the interior of its substance (fig. 70) an d 

 thus, by division and subdivision, gradually acquires considerable breadth (fig. 69), 

 or there may be thus formed several separated spirals (figs. 73, 113 a a). 



57. It will be seen, from the account above given of the formation of the muscular 

 fasciculus, that the young fasciculi have the largest and fewest spirals. In the very 

 young Tadpole, I found a great many fasciculi of this kind: while in the older 

 Tadpole, such fasciculi were less numerous. The fasciculi here presented, generally, 

 an increased number of spirals, with a diminution in their size. 



58. I cannot doubt that the larger spirals perform contraction, as well as the 

 smaller. It is probable that the difference between the contractile force of muscles 

 in childhood and in adult age, is connected with the above-mentioned difference in 

 the number of the spirals. Nor is this supposition inconsistent with the fact, that 

 muscle by constant exercise increases in its bulk. 



59. My observations on the form of the ultimate threads in voluntary muscle, 

 first made on the larva of a Batrachian Reptile, have been confirmed by an examina- 

 tion of this structure in each class of vertebrated animals, including the scaled Am- 

 phibia, and Cartilaginous as well as Osseous Fishes. Such of the Invertebrata, also, 

 as happened to be easily obtainable, were examined, and afforded ample confirmation 

 of those observations. They included animals in the Crustacea (Crab), Mollusca 

 (Limpet, Clam, Cockle, Mussel, Garden Snail, Periwinkle, Whelk), Annelida (Earth- 

 worm), and Insecta (a kind of Caterpillar). 



Facts observed in the Formation and Structure of the Crystalline Lens. 



60. In the Philosophical Transactions for 1841 , I delineated cells, first arranged, 

 like the beads of a necklace, in a line ; and then, by the disappearance of the inter- 

 vening septa, forming a tube, the foundation of the fibres of the Crystalline Lens||. 



61. I have now to state, that within this tube there are formed, in the first place 

 discs (fig. 129), and then filaments (fig. 130 a), having precisely the same structure 

 as the filaments of other parts. Nowhere have I obtained more satisfactory evidence, 

 than in the lens, that these filaments are composed of two spiral threads (fig. 131 (3, y), 

 and that the spirals give origin within their winds to other filaments. 



62. The toothed fibre discovered by Sir DAVID BREWSTER in the lens^[, is formed 



t Philosophical Transactions, 1841, p. 204. J Ibid., 1841, pp. 223, 224. 



Plate XXV. figs. 157, 158. 



|| I find that this observation was previously made by VALENTIN. See WAGNER'S Physiologic : erste Ab- 

 theilung, p. 138. ^ Philosophical Transactions, 1833. 



