256 TYPES AND MARKET CLASSES OF LIVE STOCK 



of irregular, overlapping scales, apparent only under the micro- 

 scope, forming the wool cuticle, there being from 1200 to 3000 

 exposed points of these scales to an inch. The scales open or 

 point toward the tip of the fiber, like shingles put on the wrong 

 way. Beneath the covering of scales is the cortex or body of 

 the fiber, made up of greatly elongated cells united into bundles, 

 and in the center of the fiber there is sometimes a cavity or 

 canal which may contain granules of pigment. 



Hair and wool are very similar in growth and structure, 

 but wool is crimped, has more scales, the points of the scales 

 are more open or projecting, and the entire fiber is more soft 



Fig. 81. Cross-Section of a Wool Fiber. 



a, Central canal, which is not present in most wools; b, cortex or body 

 of fiber, composed of long, spindle-shaped cells which here appear oval be- 

 cause they are cut transversely; c, wool cuticle, composed of scales. (After 

 McMurtrie.) 



and flexible than hair. These small differences give to wool 

 its special commercial values. Hair will not retain the twisted 

 state given to it in spinning, but the crimp of wool causes the 

 fibers to become entangled, and the minute scales hook to- 

 gether and hold the fibers in position when wool is spun into 

 yarn. Thus wool has a thread-forming quality which hair has 

 not, preventing slipping and separation of the fibers in the 

 yarn. The entanglement and locking of the fibers is referred 

 to as the felting quality of wool. 



