CHAPTER IV. 

 Muscular Tissue. 



THE essential element of muscular tissue, i.e. the 

 contractile element, presents, in its intimate structure, 

 both cells and fibres. The cell is a transitory ele- 

 ment, or rather is found only in those organs in which 

 an incomplete stage of development is persistent. 

 The fibre, in two distinct forms, constitutes the bulk 

 of all recognised muscles. The two varieties are 

 known as the striped, and the smooth or unstriped 

 muscular fibre. 



Smooth, or unstriped muscle. When a small por- structure of 



smooth muscu- 



tion of certain muscular organs, the muscular wall of larfU)re - 

 the intestine, or of the bladder, for example, is placed 

 beneath the microscope, it is found to consist appa- 

 rently of long, pale, spindle-shaped bodies, each one 

 of which is provided with an elongated nucleus 

 having a clear and distinctly marked outline, and 

 surrounded by a substance so finely granular as to 

 appear almost amorphous. More attentive exami- 

 nation, however, reveals the real nature of these 

 nucleated bodies the essential contractile elements ; 

 in place of a spindle-shaped cell, it is soon recognised 

 as a true fibre, presenting, as we trace it in the direc- 

 tion of its length, a regular succession of contractions 

 and enlargements. These fibres, instead of running 

 parallel with each other, cross at very acute angles, 

 and in such a manner that their points of intersection 



