BACTERIA AND DISEASE 387 



contain the antitoxin, and if injected into a man suffering with diphthe- 

 ria, will tend to overcome the germs and to cure the disease. 



Cows sometimes have a disease which seems to be a modified form 

 of smallpox. By vaccination, the same disease can be transmitted to a 

 man in whom it causes but slight inconvenience, but yet protects him 

 against smallpox almost as thoroughly as an attack of the disease it- 

 self. Universal vaccination has destroyed the terrors of smallpox, so 

 that from being one of the most common and deadly of diseases it is 

 now one of the rarest. 



689. Destruction of germs outside the body. The sun is 



one of the most efficient agents in destroying bacteria of disease. It 

 acts partly by drying the food upon which they live and partly by 

 means of its own chemical power. An abundance of sunshine in a 

 place renders it almost surely free from disease. In some hot and dry 

 climates decay is almost unknown, for bodies become dried before 

 the germs can grow. On the other hand, darkness, decay, and disease 

 go together. 



The wind drives away the germs. In the open air it is almost im- 

 possible to transmit disease. In closed rooms, germs which are given 

 off from a diseased body may collect in great numbers, and in sick 

 rooms may reenter the sick person and so prolong his sickness. Good 

 ventilation is one of the best means of preventing diseases. 



The soil destroys germs of disease. In it are special germs whose 

 work is to oxidize all organic matter, including other kinds of germs. 

 It also filters out the germs from dirty water which soaks into it. Burial 

 will destroy the disease germs on all kinds of substances and dead bodies. 



690. Antiseptics. Man uses three principal means to 

 destroy disease germs which may threaten him. In the 

 first place, he may wash them away with soap and water. 

 He can thus get rid of most germs. 



Secondly. A boiling heat applied for fifteen minutes 

 will kill all kinds of germs. A substance freed from germs 

 is said to be sterilized or disinfected. Clothes and utensils 

 used in a sick room can be made safe for future use by 

 boiling, Before a surgical operation, the instruments and 

 dressings are thoroughly sterilized by boiling. 



