DR. MARTIN BARRY ON FIBRE. 99 



blood : they become rings (fig. 48 a) ; the rings pass into coils ; and the coils unite, 

 thus forming spirals (y). The adjacent spirals interlace, from the peculiar arrange- 

 ment, in relation to one another, of the rows of rings (par. 23). In the space 

 circumscribed by the windings of these interlaced spirals, smaller spirals have their 

 origin ; these in turn give origin to others ; and so on. An example of this, in a later 

 stage, is afforded by fig. 58. Here, a represents the outer or larger spirals ; and (3 

 the situation of the inner or smaller ones. The outer spirals gradually disappear, by 

 entering into the formation of the common investing membrane discovered by SCHWANN, 

 and in its formed state well described by BOWMAN, who proposes to denominate it the 

 " sarcolemma-|-." This may perhaps explain the mode of origin of the darker of the 

 longitudinal striae, three of which are represented in fig. 63 (|8, /3, /3) : these being ap- 

 parently the situations of membranous partitions or septa (par. 53), passing into the 

 interior of the fasciculus from the common investing membrane. 



43. The process just mentioned, of smaller spirals arising in the space circumscribed 

 by the larger ones, with the gradual disappearance of the latter, seems to be conti- 

 nued in later stages^. The number of the spirals becomes continually greater, and 

 their size more and more minute (figs. 95, 58, 65), until they reach the number and 

 minuteness represented in figs. 96, 63 : and they attain even a smaller size. 



44. The outer spirals being formed of the outer or ring-like portions of the discs 

 (fig. 48 a), the inner spirals appear to have their origin in the inner part, or nucleus 

 of these discs : and when the inner spirals in their turn enlarge, and new ones form 

 in their interior, the origin of the new spirals, also, seems to take place in the line of 

 continually renovated nuclei ; and so on. 







45. Fig. 63. presents a state of the muscle-fasciculus, in which it contains what is 

 denominated the " fibril," of a very minute, though not the minutest size. This 

 " fibril " is no other than a state of the object which I have called a flat filament : 

 and which, as we have seen, is a compound structure. The figure (fig. 55) and de- 

 scription (par. 14) by which I have endeavoured to explain the structure of the fila- 

 ment, are especially applicable to the muscular " fibril." This " fibril " I find to be, 

 not round and beaded, as it has been supposed, but a flat and grooved filament, con- 

 sisting of two spiral threads, running in opposite directions, and interlacing at a cer- 

 tain point (a fig. 55) in every wind. A transverse section of this filament, as before 

 mentioned, is rudely represented by the figure 8 . 



t SCHWANN is the discoverer of this membrane ; but we are indebted to BOWMAN for the only complete de- 

 scription hitherto given of it in a formed state. Its mode of origin however, out of spirals, is for the first time 

 described in the present memoir. 



J In young fasciculi I have noticed a transverse space to extend far into the interior ; which is not the case 

 in those more advanced, the cause being the disappearance of the outer and larger spirals, and the continual 

 formation of inner and smaller ones. 



I "have often seen a filament (" fibril") becoming a fasciculus (par. 44). See figs. 56, 57, 84, 64 y. En- 

 larged filaments are well seen in the heart of the Turtle. 



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