ANIMAL FIBERS 



121 



American silkworm. 



reached their full growth they eat only three or four times a day. 

 When the worm is thirty-two days old, it is about two inches long 

 and a little larger than a common lead pencil. At this time it 

 stops feeding entirely and begins to spin the silk fiber from its 

 mouth, which it continues until 

 its whole body is completely 

 encased. This process requires 

 from two to five days. Then 

 the worms are placed over a 

 slow fire of charcoal or wood 

 and are killed by heating. Next 



the cocoons are placed in boiling water in order to soften the 

 gummy substance which holds the threads together. Then the 

 silk is unwound from the cocoons and reeled into skeins ready 

 for shipping. When the silk reaches the manufacturer in this 

 country, it is put through a process of twisting or spinning called 



throwing. When this process is 

 completed, the silk is ready for 

 weaving and the loom. The 

 United States consumes about 

 one third of all the raw silk pro- 

 duced in the world. Nearly all 

 of our large silk mills are in 

 New Jersey, New York, and 

 Pennsylvania, but smaller 

 plants are found in nineteen 

 different States. 



Products. Our various silk 

 and satin goods, ribbons, and 

 Chinese silkworms. thread are the most important 



products of silk fiber. 



Woolen Fibers. The best grade of wool fiber is furnished by 

 the wool of merino sheep, a species brought to this country from 

 Spain. It is estimated that three fourths of the sheep of the 

 United States are of pure or mixed merino descent. In fineness of 

 fleece and length of fiber it is excelled by no other breed in this 

 country. About five hundred million pounds of wool is required 

 annually for manufacturing purposes, and of this amount about 



