430 APPLIED PHYSIOLOGY 



found in the cells of the brain, and in the saliva. It is caught from the 

 bite of dogs or cats which have the disease. It is spread mostly by 

 means of homeless animals. Dogs running loose should be muzzled, and 

 stray ones should be caught by a public dog catcher. If a person is bitten, 

 the animal should be securely shut up to see if it has the rabies. If it has 

 the disease it will soon die, but if it remains alive the wound is no more 

 serious than one made by a needle. The germs in a bite may be killed 

 by opening the wound and cauterizing it to the very bottom. In those 

 bitten by a rabid animal the disease may be prevented by injecting an 

 immunizing substance prepared from rabbits which have been given the 

 disease. This substance may be had by application to the boards of 

 health of the greater cities. 



749. The plague. The black plague is a pestilence 

 which has often appeared in Europe. It killed half the 

 inhabitants there in the fourteenth century. It still 

 exists in some parts of the world, and is as deadly as 

 ever when it is allowed to go unchecked. It is due to- 

 bacteria which produce swellings and abscesses in the 

 flesh. It seldom spreads from one person to another, but 

 the bacteria are carried from rats, which have the disease, 

 to persons by means of fleas. Its control and suppression 

 depend principally on the extermination of rats. 



750. Hook-worm disease. A kind of intestinal worm 

 called the hook worm produces a sickness in which there 

 is an intense feeling of lifelessness or laziness. The 

 worms lay eggs which hatch in the ground. The young 

 bore their way through the skin and finally fasten them- 

 selves by tiny hooks to the inside of the intestine and be- 

 come about a half an inch in length. They produce 

 their bad effects by sucking blood from the mucous mem- 

 brane. They may be killed by medicines which kill other 

 intestinal worms. The disease may be prevented by dis- 

 posing of all sewage so that the eggs and young worms 

 cannot reach the soil where people work. Cleanliness and 



