STRUCTURE OF ORGANIC MUSCULAR TISSUE. 



193 



each layer, though they may pursue very different directions if 

 several layers be present. Where the fibres are united, not in 

 one, but in several directions, fasciculi of fibres are produced. 

 These vary in length and thickness, and either run parallel to 

 each other, or cross at a more or less acute angle, or, lastly, pre- 

 sent a plexiform arrangement, and frequently anastomose . It is 

 from these differences in the directions taken by the fibres, and 

 in their mode of union, that the irregularities observed in sec- 

 tion result. For if the section be carried transversely through 

 a portion of the tissue in which the muscular fibres run parallel, 

 round or subangular rings, lying in close proximity, are met 

 with, presenting a central or laterally situated transversely 

 divided nucleus ; whilst if the bundles of fibres run in various 



Fig. 32. 



280. 



Fig. 32. a, Transverse section of the longitudinal fibrous layer of the 

 intestine of a Frog ; b, transverse section of muscular bundles from the 

 uterus of a Sheep ; c, muscular trabeculae from the urinary bladder of 

 a Frog, treated with acetic acid. 



