48 



MUSCLES. 



* 



Development of 

 unstriped muscu- 

 lar fibre. 





as generally supposed, to a turgescence, or erection, 

 similar to that of the corpora cavernosa. 



Smooth, or unstriped muscular fibres are developed 

 from formative cells, which at first elongate, and then 

 become attached by their extremities. In some organs 

 and localities this mode of development is incom- 

 plete ; the metamorphoses of the formative cells are 

 arrested in their earlier stages, and thus the exist- 

 ence of the contractile fusiform corpuscle the fibre- 

 cell of Kolliker, is explained. Hereafter we shall 

 see that the true striped muscular fibre passes through 

 the two stages we have just described before it 

 assumes its ultimate and definite form, so that, in a 

 general histological survey of the entire muscular 

 tissue of the body, it may be considered as repre- 

 senting, in its several constituent portions, different 

 and progressive degrees of development of the same 

 formative element of which the striped fibre is the 

 last and most perfect form. 



In the muscular tissue of the uterus during preg- 

 nancy we recognise the development of new muscular 

 fibre of the smooth variety. According to Kol- 

 liker this takes place only during the first six months 

 of gestation. In its deeper strata an immense num- 

 ber of cells is recognisable, measuring from T^orth to 

 sVth of a line, and we can trace them through the 

 several phases of their development into smooth mus- 

 cular fibres. After delivery, and whilst the uterus is 

 diminishing in bulk, the larger proportion of these 

 muscular fibres become infiltrated with fat, break 

 down, and disappear entirely by absorption ; it is by 

 this process of fatty atrophy that the uterus returns, 

 after child-birth, to its original dimensions. 



