TYPES AND MARKET CLASSES OF LIVE STOCK 257 



The peculiar structure of the wool fiber was first deter- 

 mined by Youatt, a famous English observer and writer. In 

 Merino wool, the scales or projections are very distinct and 

 sharply pointed, and it was by an examination of Merino wool 

 that Youatt determined the structure of the wool fiber. In 

 the medium-wool breeds, the scales are less distinct and sharp, 

 and in the long-wool breeds, they are rounded off and indistinct. 

 In Merino wool, about 2400 of these scale ends are found to the 

 inch; in the Southdown there are 2000 to 2080; and in the Lei- 

 cester, 1850 to 1860. Hence, 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 con- 

 ducted extensive investigations of wools for the U. S. Depart- 

 ment of Agriculture,* found the average diameter of the Merino 

 fiber to be 1/1194 of an inch, while the Southdown had an 

 average diameter of 1/865, the Hampshire Down 1/769, the 

 Lincoln 1/685, the Leicester 1/654, the Cotswold 1/605, 

 and the Oxford Down 1/581. In 1860, American Merino 

 fibers with a diameter of 1/1572, and American Saxon Merino 

 fibers measuring 1/1875 of an inch in diameter were exhibited 

 in London, showing the extreme fineness which may be secured 

 in wools. 



Secretion and composition of yolk. Opening into each 

 wool follicle are a couple of sebaceous or oil glands, furnishing 

 a profuse secretion of an oily or fatty material, called the yolk, 

 which is thrown out at the same time the fiber is formed. This 

 secretion consists largely of a soapy matter having a potassium 

 base, together with an animal oil which gives to the yolk its 

 peculiar odor. Yolk, then, is not strictly a grease or oil, but is 

 a soap with an excess of oil. This explains why it dissolves 

 freely in warm water and may be washed almost entirely out 

 of the fleece, and why it cleanses and whitens the hands as soap 

 does. The quantity and fluidity of the yolk vary greatly, being 

 greater when the sheep are healthy and well fed, and varying 

 also according to the breed. The yolk maintains the softness 

 and pliancy of the fibers, and protects the scaly surface from 

 injury such as might result from friction of the fibers against 

 one another during the movements of the animal. It also helps 



*U. S. Dept. Agr. Report, Examination of Wools and Other Animal 

 Fibers. 



