6 ANIMALS OF LAND AND SEA 



tails, and become inert. If a sheep eats grass with these 

 things chnging to it they come to hfe again, plod their way to 

 the sheep's liver, and soon develop into full grown liver flukes. 

 The cost of wool production, and hence the price of woollen 

 cloth, has been greatly lessened by the discovery of the in- 

 tricate hfe history of this pernicious organism as a result of 

 which means have been devised for controlling it. 



The small holes in Wilhe's trousers just above the knee 

 were made by buffalo bugs which concentrated on some spots 

 of soup that Wilhe spilled one day. The lines nearby were 

 made by clothes moths. Before this summer these trousers 

 had been Willie's best, but they had been put away with 

 insufficient care. The thread used in sewing the trousers was 

 made from Sea Island cotton, a special t^-pe of cotton de- 

 veloped by many years of the most careful selection and grown 

 with every precaution to guard it against insect and fungus 

 pests each one of which had to be studied separately and 

 exhaustively and traced in all its stages to determine how best 

 it could be attacked. The buttons were attached with linen 

 thread made from flax from Flanders, grown with the same care 

 as the cotton and prepared on lines determined by long years 

 of investigation as the best. 



Willie's shirt was made from upland cotton, quite different 

 from Sea Island, just as carefully selected, and just as care- 

 fully protected from the pests, but with different ends in view. 

 Its sole remaining button, of white and shining pearl, came 

 from a river mussel in Iowa. When young these river mussels 

 attach themselves to fish and this is how these clumsy creatures 

 mainly get about. This simple biological observation is of the 

 greatest importance to the mussel industry. 



Willie doubtless did not appreciate the dangers of the mud 

 he walked across with his bare feet, for on mud lurk the young 

 of the dreaded hookworms which bore through the skin and, 

 entering the body, live within it and more or less seriously 

 incapacitate the victim. In the copper-head which lay be- 

 neath the log on which he sat, unknown to him, Willie would 



