PHYSIOLOGY OF MOVEMENT. 



703 



The striated appearance of muscular tissue is due to the arrange- 

 ment of the sarcous substance in alternate light and dark layers or disks. 



Each muscular fibre is made up of a large number of primitive 

 fibrillse placed side by side and united by a semi-fluid cement substance, 

 the fibrillse being so arranged that the transverse markings lie at the 

 same level. 



The muscular corpuscles in the muscular fibres of man and most 



FIG. 272.-UNSTKIPED MUSCULAR TISSUE. FIG. 273.-MUSCUI.AK CELLS FROM : THE 

 imipnhernpr \ MUSCULAR COAT OF THE (STOMACH, 



(Jiuenoerger, ) Enlarged Two Hundred and Fifty 



A and B, fetal cells; C. H, fully formed fibre; I. nraipTFi?! t KllpllberaerA 



bundle of fibres ; K, cross-section of bundle of pale muscular DIAMETERS. ( ILUenom yvr.) 



fibres. Aj elongated nucleus ; B, pointed ends of the cells. 



vertebrates, with the exception of the tissue of the heart, are situated on 

 the surface of the muscular substance, but in invertebrates they are 

 usually found in the central part of the fibres. The muscular fibres are 

 united in bundles by connective tissue and terminate in tendons which 

 are composed of connective-tissue fibrillse. 



The unstriped muscular fibres are composed of elongated spindle- 

 shaped nucleated cells, which are contractile in one direction. These 



