Types and Market Classes of Live Stock 28d 



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 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 together 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 



Fig. 107. — 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 because they are cut transversely; c, wool cuticle, composed of scales. 



entanglement and locking of the fibers is referred to as the "felting 

 quality" of wool. 



In Merino wool, the scales or projections are very distinct and 

 sharply pointed. In the medium- wool breeds, the scales are less dis- 

 tinct and sharp, and in the long-wool breeds, they are rounded off and 

 indistinct. In Merino wool, about 2,400 of these scale-ends are found 

 to the inch; in the Southdown there are 2,000 to 2,080; and in the 

 Leicester, 1,850 to 1,860. Merino wool is superior in felting quality, 

 the others standing in a relation proportional to the figures given. 



Fineness of fiber. — Dr. William McMurtrie, who conducted exten- 

 sive investigations of wools for the U. S. Department of Agriculture, > 



^U. S. Dept. Agr. Rpt., Examination of Wools and Other Animal Fibers. 



