TISSUES AND ORGANS 59 



striated muscle, consists of elongated cells, 

 with no striation. It is found chiefly in the 

 wall of the stomach and bowel, in the ducts of 

 glands, in the walls of blood vessels, and in 

 the skin. 



Finally, we find the power of movement, 

 or contractility, manifested by many cells, 

 usually isolated in a fluid, or embedded in a 

 tissue. Thus the white blood corpuscles 

 (leucocytes of several varieties), cartilage 

 cells, the cells in bone, connective tissue cells, 

 the cilia (hair-like structures) found on some 

 epithelial cells, are all contractile and are 

 capable of changing their shape. All forms 

 of contractile tissues are for purposes of 

 movement. Thus the movements of the 

 limbs in locomotion, and the movements of 

 the chest Avail in respiration, are effected 

 by means of striated muscles. Again, the 

 slow contractions by which, during diges- 

 tion and absorption, the food stuffs are 

 propelled along the alimentary canal, are 

 effected by non-striated muscle. The heart 

 beats, the changes in the calibre of the 

 smaller arteries by which the quantity of 



