416 A YEAR IN SCIENCE 



in the destruction of the disease germs in the 

 person. 



One of the most recent and valuable discoveries in 

 medicine is the method of production and the use of 

 serums called antitoxins which normally are produced 

 in the blood of a person who has an infectious disease. 

 The immediate stimulus for their production is the 

 presence of toxins. Sometimes these are not produced 

 rapidly enough and the disease cannot be checked. For 

 a few diseases, such as diphtheria and lock jaw, it has 

 been found possible to produce artificial antitoxins to 

 inject into the human body. The method for producing 

 the antitoxin for diphtheria is as follows: Bacteria 

 which produce diphtheria are grown in blood serum in 

 the laboratory. These bacteria produce toxins, which are 

 then separated from the live germs. A number of doses 

 of this toxin are then injected into the blood of a horse. 

 This is done at intervals for several months, during 

 which time large quantities of antitoxin are being pro- 

 duced in the horse's blood. Finally blood is taken from 

 the horse and from it antitoxin is extracted. This is 

 injected into the body of a person who has diphtheria 

 and often causes a cure. If it is injected into the body 

 of a person who has been exposed to the disease, it pre- 

 vents its development. 



Vaccines. The term vaccine is familiar to most of 

 us because of its long use in connection with vaccina- 

 tion for smallpox. In order to stimulate the body to 

 produce substances to destroy a disease, dead or weak- 



