ELEMENTARY STRUCTURE OF ORGANIZED BODIES. 17 



mary muscular fibre. The fibre thus evolved is a hollow 



cylinder, in the cavity of which, cell-nuclei lie near to one 



another (fig. 6, a). 



From this it is , c A 



probable that the 



globules which 



compose the fibre 



were hollow, 



were cells, and 



that the nuclei, 









included in the 

 cylinder, are the 



nuclei belonging Fig. 6. a, b, c. Different stages in the evolution 

 to these primary of muscular fibre ; d, a muscular bundle imper- 

 cells. The earlier fectly developed, standing on its edge. 



process of evolution must therefore have been as follows : 

 the globules or primary cells arranged themselves in a row, 

 or coalesced into a cylinder, and then the septa, by which 

 this cylinder must have been divided, underwent absorption. 

 The nuclei are flat, and lie within the cylinder, not in its 

 axis, but on its walls. This cylinder, rounded and closed at 

 its ends, this secondary muscular cell, grows continually, like 

 a simple cell, but only in the direction of its length, for it either 

 gains nothing in point of breadth, or it becomes actually thinner. 

 The growth lengthwise, however, does not proceed from the 

 ends only, but through the entire extent of the cylinder, as is 

 obvious, from the fact of the nuclei, which at first lay close to 

 one another, getting more and more distant, and even themselves 

 elongating often in no inconsiderable degree. In this way, the 

 muscular bundle a, (fig. 6) is changed into the bundle 6. At 

 this period, the deposition of a new substance upon the inner 

 surface of the parietes of the cylinder, or cellular membrane of 

 the secondary muscular cell, takes place, by which its wall is 

 thickened (compare the fibre c with the fibre b, fig. 6). That 

 the thickening of the wall here, is no thickening of the cell- 

 membrane itself, as is in the case of cartilage, appears from 

 this, that the nuclei are not forced inwards, towards the hollow 

 of the cylinder, but outwards, and continue lying in front 'of 

 the secondary deposition, as is seen in d (fig. 6). The secon- 

 dary deposition in question, goes on until the cylinder is com- 

 pletely filled. The deposited substance changes into very 



c 



