CHAPTER IX 



MUSCLE TISSUE 



/While protoplasm in general possesses the property of contrac- 

 tility, it is in muscle tissue that this property reaches its highest de- 

 velopment. IMoreover, in muscle this contractiUty is along definite 



Fig. 54.— Isolated Smooth Muscle Cells from Human Small Intestine. X4oo- 

 (Technic i, p. i20-) Rod-shaped nucleus surrounded by area of finely granular pro- 

 toplasm; longitudinal striations of cytoplasm. 



directions, and is capable of causing motion, not only in the cell itself, 

 but in structures outside the cell. 



Muscle may be classified as: (i) Involuntary smooth muscle; (2) 

 voluntary striated muscle; (3) involuntary striated muscle or heart' 

 muscle. 



Involuntary Smooth Muscle. — This is the simplest form 

 of muscle tissue and consists of long spindle-shaped cells (Fig. 



a b 





'^^^^^ 



A B 



Fig. 55. — .\pparent Intercellular Bridges of Smooth Muscle. A, From longitudinal 

 section of intestine of guinea-pig ; B, from transverse section of intestine of rabbit. X 420. 

 a, Nerve cell; b, end of muscle cell. (Stohr.) 



54) which are prismatic on transverse section (Fig. 55). The length 

 of the smooth muscle cell varies usually from 30 to 2ooijl, its width 

 from 3 to 8m, ^ except in the pregnant uterus where the cells fre- 

 quently attain a much greater size. Less commonly the smooth 



^ In the walls of very small blood-vessels smooth muscle cells 15 to 20yu are found. 

 (Apathy). 



115 



