228 FARM ANIMALS 
is manufactured from the finer and shorter wools, but 
for some purposes longer wools are superior, and for one 
purpose or another every grade and length can be used. 
5. How wool grows.—The wool of sheep grows con- 
tinuously throughout the year. If the feed is uniform 
and nutritious, a uniform quality of wool 
will be produced according to the breed 
of sheep. Anything which affects the 
health of the animal also affects the 
quality of the wool. During a period of 
sickness or scant rations, the wool may 
temporarily stop growing. When the 
animal recovers, or when better rations 
are fed, the wool begins growth again. 
However, as a result of this interruption, 
a weak spot is produced in the wool, 
Examining Woo. For Which greatly decreases its strength and 
LENGTH ANPDENSITY Value for manufacturing perposes. 
Like a chain which is no stronger than its weakest link, 
so the strength of a wool fiber is determined by its weak 
spot. 
6. Yolk—By yolk in the wool is meant the natural 
grease or oil secreted by the skin. Under normal con- 
ditions the yolk gives the fleece a kind of creamy ap- 
pearance. In healthy sheep the yolk constitutes about 
one-third of the weight of the fleece. At the factory, the 
fleeces are scoured and the yolk washed out before the 
wool is used in manufacture. The secretion of yolk is’ 
favored by nitrogenous and fatty foods. The yolk is 
of great importance, as it keeps the fleece soit and com- 
pact, clean and bright on the inside, and is a protection 
to sheep in turning water. Sheep in poor health or un- 
derfed show a lack of yolk, while overfeeding may induce 
an excess. 
