340 



BIOLOGY AND HUMAN LIFE 



produced which counteracts, or neutralizes, the poison. Poisons 

 of this class are known as toxins (from a Greek word meaning 

 "poison"). The substance produced by the Hving cells as a re- 

 action to a toxin is called an antitoxin. An antitoxin is always 

 specific; it will neutralize the toxin that brought about its 

 formation, but no others. The best-known toxins are those pro- 

 duced by certain bacteria, especially those that cause lockjaw 



1890 

 1895 

 1900 

 1905 

 1910 

 1914 



110 Deaths out of every 100,000 of population 



38.0 % of cases 



106 In this year antitoxin was introduced 



18.8 



62 



15.2 



36 



31 



10.0 □ 

 9.7 □ 

 9.1 □ 



Fig. 



159. Reduction in deaths from diphtheria in New York City 

 (Manhattan and Bronx) 



The numbers and rectangles on the left show the number of deaths out of every hun- 

 dred thousand of the population. The numbers on the right show how many fatal- 

 ities there were for every hundred cases of the disease. Note the rapid falling off 

 both in the proportion and in the number of deaths after the year 1895, when anti- 

 toxin was first used. The great reduction in recent years is due to the use of the 

 Schick test for susceptibility with artificial immunization 



and diphtheria. When a quantity of toxin, not enough to kill, 

 is injected into the blood of an animal (for example, a horse), 

 the cells begin to throw off antitoxin. They will produce more 

 than enough antitoxin to neutralize the poison received, just as 

 you might strike at an annoying mosquito much harder than 

 was necessary to drive it away. After the poison has all been 

 destroyed, there will be a quantity of antitoxin left in the blood. 



