CHAPTER XXVII 

 ECONOMIC ZOOLOGY 



499. Reference has already been made in the appropriate 

 places in the text to some of the most important ways in which 

 the various branches of animals are related to human welfare. 

 We are now in a position to look back over the economic bearings 

 of all animals and to get a broader view of the part .they play in 

 the life of man. This is a point at which Zoology touches the 

 interest of every citizen of the world, whether he has any other 

 interest in it or not. The economic aspect should therefore be 

 one of the features of the study of Zoology in our schools. 



500. An Analysis of the Ways in which Animals Affect the 

 Welfare of Man. — i. Helpfully: (a) as food; (b) for clothing; 

 (c) in the saving of labor; (d) in scientific experiment and 

 medicine ; (e) for pleasure, as companions and pets or in various 

 esthetic ways; (f) in minor miscellaneous ways. 



2. HurtfuUy : (a) directly hurtful or dangerous; (b) as causes 

 or conveyors of disease in man; (c) as enemies of our friends 

 among the animals; (d) as destructive to vegetation; (e) as 

 injurious to various manufactured products. 



These headings are by no means exhaustive nor of equal 

 merit, but they will give the student some conception of the 

 closeness of the bond between man and the rest of the animal 

 kingdom. 



501. Animals as a Food Supply. — The difficulties of human 

 life have been such at various places and times that man has 

 experimented with almost all kinds of food that have held out 

 any sort of promise of nutrition or pleasure. Notwithstanding 

 this, very few of the invertebrates have been given a wide place 

 in his bill-of-fare. The lowest forms eaten are the "trepangs" 

 (holothurians) which are used in great numbers by the Chinese. 

 In the Phylum of Mollusca the oyster is at the head in impor- 

 tance. There are also a number of marine and fresh-water 

 clams and mussels which are used in smaller numbers. Some 



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