RELATION OF ANIMALS TO MAN 289 



of furs, the choicest of which come from the ermine, 

 the seal, the sable, the beaver, the mink, the fox, the 

 squirrel, and the skunk. Cheaper furs are obtained 

 from the cat, the dog, the raccoon, and the rabbit. From 

 the skin of the coarser haired animals, such as the cow, 

 the sheep, and the horse, leathers are made. 



Animals injurious to man. Animals are injurious to 

 man directly or indirectly in many ways. We will 

 consider only those forms (1) which produce or carry 

 human diseases, and (2) which are injurious to crops. 



Diseases produced and carried by animals. Within 

 recent years we have learned that yellow fever, malaria, 

 smallpox, sleeping sickness, and some other diseases are 

 caused by the presence and growth of one celled animals 

 (protozoa) in the human body. Long ago it was dis- 

 covered that various parasitic worms, such as the tape- 

 worm and the trichina, lived in our bodies and were the 

 causes of pain and injury to the body. More recently the 

 hook-worm has been found to be responsible for much of 

 the laziness and shiftlessness of "the poor whites" of the 

 South. The entire South undoubtedly has been 

 retarded in its development by this parasite. Not only 

 are some diseases produced by animals, but some dis- 

 eases are spread by them. The mosquito and fly carry 

 malarial fever and typhoid fever, the tse-tse fly carries 

 sleeping sickness, and the flea carries bubonic plague 

 from rats to man. 



Animals injurious to crops. Insects do the greatest 

 damage to crops. Experts estimate that insects rob 



