440 



MANUAL OF PHYSIOLOGY. 



FIG. 178. 



elastic substance, so that their tapering extremities fit closely 

 together and form commonly a dense mass or sheet. Sometimes 

 they branch more or less regularly, and then are arranged in 

 networks. 



These cells vary greatly in size as well as in the relation of 

 their length to their width, in some places deserving the name 

 fibres, or fibre-cells, and in others being only elongated cells. 



The striated muscle tissue is that which is found in the volun- 

 tary skeletal muscles and in the tissue of the heart, and therefore 



forms the large proportion of the ani- 

 mal, and is known as the flesh. The 

 flesh can by judicious dissection easily 

 be divided into single parts called 

 muscles, each of which contains many 

 other tissues and is so attached as to 

 carry on certain movements, and may, 

 therefore, be regarded as an organ. 



Such a muscle is inclosed in a sheath 

 of connective tissue, from which sheet- 

 like partitions or septa pass into the 

 mass of the muscle and divide it into 

 bundles of fibres, which they inclose. 

 These septa also act as the bed in 

 which the vessels and nerves lie. 



The bundles of fibres of skeletal 

 heart muscle, separated one mugc i e vary much in siz6) giving a 



showing the truncated (a), , . . j.,*. 



, coarse or fane grain m different 

 or divided (c) ends, and 



lininchcs (6). muscles; they are composed of a 



greater or less number of fibres, which 



lying side by side run parallel one to the other. The single fibres 

 of striated muscle vary in length, sometimes reaching 4-5 cm. 

 (2 inches), but being on an average much shorter, so that they 

 only extend the entire length of a muscle in the case of very 

 short muscles. In long muscles their tapering points are made 

 to correspond with those of other fibres to which they are firmly 

 attached. The soft fibres are pressed by juxtaposition into pris- 

 matic forms, so that in a fresh condition they appear polygonal 



Short striated cells of the 



