4 INTRODUCTORY REMARKS. 



From another point of view, all animals and plants may be 

 divided into two large groups the useful and the injurious. 

 The useful animals are all those which man rears for his food, 

 for clothing, or for any other purpose. The ox which supplies 

 us with meat, leather, and bone, is a peculiarly useful animal ; 

 the field mouse which devours the crops is a peculiarly in- 

 jurious animal. Man must wage war with the latter, and he 

 is assisted by other animals, which are themselves great 

 enemies to injurious animals ; and, therefore, all these which 

 thus assist man, are called indirectly useful animals : the cat is 

 one of these, because it eats the mice, which destroy corn and 

 other stores. And as the greatest enemies of man are neither 

 lions nor wolves, nor even venomous serpents, but the insects 

 which eat his crops, it follows that all the animals which eat 

 insects, whether mammals, birds, reptiles, or insects themselves, 

 are useful to man. 



In order to have useful animals always at hand, man has 

 determined to make them live with him at home. The animal 

 is then said to be domesticated ; the horse, ox, sheep, dog, cat, 

 fowl, and duck, are domesticated animals. In other countries 

 the elephant and camel are also domestic animals. 



Plants, like animals, are also divided into the useful and the 

 injurious. They are injurious when they interfere with the 

 growth of cultivated plants, or when they are poisonous. But 

 at least man, with a little instruction, can always detect those and 

 destroy them. 



There are different kinds of useful plants. Some yield 

 valuable medicines, like the poppy which produces opium, or 

 the cinchona which cures fevers. These plants are called 

 medicinal. Other plants are esculent, and we sometimes eat their 

 roots, as the carrot, sometimes their leaves, as the salads ; but 

 most often their fruits. There are other plants which, without 

 being articles of food, yield what are called spices, such as 

 pepper, cinnamon, cloves, nutmeg, parsley, chervil, garlic ; 

 there is a considerable number of these plants. Lastly, there are 



