MO MUSCLE. 



tivc fibres (fibrils) of muscle. These longitudinal fibres do not 

 appear to represent the original condition of the secondary 

 deposit, but the latter is structureless at first, and its trans- 

 formation into fibres takes place subsequently. The change 

 seems, however, to commence at a very early period, and 

 indeed before the cavity is completely filled. The transverse 

 Btriae of the muscular fasciculi, which, according to my mode of 

 explanation, are produced by the peculiar form of the primitive 

 fibres, likewise make their appearance before the complete 

 filling up of the cell-cavity, as pi. IV, fig. 3, c, exhibits. 



According to the observations of Meyen on the formation 

 of the cells of the liber, after the coalescence of the cells and 

 absorption of the septa, a secondary deposit also takes place 

 upon the common cell-membrane in the same way that we 

 have observed to take place in muscle ; but I know of nothing 

 amongst vegetables analogous to a secondary deposit consisting 

 of longitudinal fibres. On the contrary, according to Valentin, 

 such deposits appear to take place in plants universally in 

 spiral lines. The beaded appearance which the primitive mus- 

 cular fibres here and there present, might perhaps be regarded 

 as the result of this tendency to a spiral formation, the intu- 

 mescences (beads) being so placed, as to produce the transverse 

 strise, and the latter may perhaps be spiral and not circular. 

 This is, however, a mere conjecture, and requires further re- 

 search. 



The involuntary muscles, such as do not present the trans- 

 verse striae, appear to originate in a manner similar to that 

 just described. They differ, however, from the voluntary or 

 striated muscles, in their fibres being generally shorter than 

 those of the latter; probably, therefore, fewer primary cells 

 arrange themselves together to form a secondary cell, and 

 their fibres are commonlv thinner and flat. T found in a 

 human uterus, which contained a mature foetus, some long 

 muscular fibres of the breadth of the common primitive fasci- 

 culi of voluntary muscles, which were so flat as scarcely to 

 amount to 0-0010 to 0-0015 of a line in thickness. The 

 involuntary muscles, likewise, have cell-nuclei, proving that 

 the fibres composing them do not correspond to the primitive 

 fibres (fibrils), but to the primitive fasciculi of the voluntary 

 muscles. An opposite view of the matter might be taken 



