250 



THE BIOLOGY OF DISEASE 



of quarantine will be extended. In addition to individuals 

 being quarantined in a dwelling, all the inhabitants of a 

 city or state may be quarantined in case of severe epi- 

 demics ; or the transportation of stock from one state to 

 another may be prohibited in the case of a serious com- 

 municable disease existing in cattle or sheep. The quar- 

 antine laws, for example, order from time to time that all 



dogs in the town or 

 county shall be muzzled 

 as a protective measure 

 against rabies. 



Immigrants suffering 

 from certain diseases are 

 prohibited from landing 

 in the United States. 

 This means that there 

 are national as well as 

 state and city quaran- 

 tine laws. The present quarantine laws are the most 

 effective protective measures against the spread of disease 

 known to man and are the product of a high degree of 

 civilization. 



191. Vaccination. — The success which has attended the 

 efforts of man to overcome disease is well illustrated hy 

 smallpox. For centuries this disease was responsible for 

 many deaths throughout the world. It is said to have 

 existed in China centuries before Christ. Later it swept 

 over Europe again and again. King Frederick William 

 III of Prussia stated, in 1803, that 40,000 people suc- 

 cumbed annually in his kingdom. A famous French 

 physician wrote in 1754 that every tenth death was due 

 to smallpox, and that one fourth of mankind was either 

 killed by it or disfigured for life. Smallpox was brought 

 into the Western Hemisphere soon after the discovery 



Figure 249. — Agar Plates. 



Where a house fly was allowed to walk 

 White patches are bacterial growths. 



