288 A YEAR IN SCIENCE 



coast as a result of over fishing. The animal value of 

 the lobsters taken on the North Atlantic coast is about 

 $15,000,000. The oyster industry is even more profit- 

 able, aggregating over $50,000,000 a year. Every class 

 of vertebrates furnishes species used as food. The 

 total annual value of the fisheries of the United States 

 is over $50,000,000. Frogs and turtles are edible, but 

 are of minor importance for food. Many kinds of birds 

 are eaten, furnishing annually hundreds of millions of 

 dollars ' worth of food to man. To the mammals belong 

 the cow, the swine, and the sheep, the animals which 

 supply most of our meat. Besides meat, chickens fur- 

 nish eggs, and cows furnish milk, butter, and cheese. 

 Animals supplying' clothing. We derive most of the 

 materials from which our clothing is made from plants. 

 But the use of feathers, furs, skins, and wool of animals 

 for clothing materials is of considerable importance. 

 From the invertebrates only one product is obtained, 

 but that is of great value. When the caterpillar of the 

 silk worm moth goes into the resting stage, it forms 

 a cocoon made of silk secreted by glands in its body. 

 The worms are killed by putting the cocoons into hot 

 water, and then the silk is unwound. From these silk 

 threads one of our most expensive fabrics is made. The 

 silk industry is of much importance in China and Japan. 

 It has not proved profitable in the United States 

 because of the high cost of labor. Our principal source 

 of clothing is the vertebrate animals, more especially 

 the mammals. From these we obtain a great variety 



