288 AGEICULTUEAL AND INDUSTBIAL BAGTEEIOLOGY 



The standardized antitoxin is now filtered through por- 

 celain filters and placed in suitable small containers. It 

 may be used in prevention or curing of the disease diph- 

 theria by injection subcutaneously by means of a hypo- 

 dermic needle. 



Preparation and Utilization of Other Antitoxins.— 

 Antitoxins may be prepared in a somewhat similar manner 

 for the prevention and treatment of tetanus or lockjaw, 

 certain types of gaseous edema and for botulism. Anti- 

 toxins have also been prepared for the toxins of the venoms 

 of various snakes. 



Agglutinins and Precipitins 



Two men working independently, Gruber and Widal, dis- 

 covered almost simultaneously that when certain kinds of 

 bacteria were present in the body, as in certain diseases 

 such as typhoid, the blood serum came to contain some sub- 

 stance which would cause agglutination or flocculation of 

 bacteria of this particular type. For example, when a drop 

 of blood serum from a person who has typhoid fever is 

 placed in a broth culture of typhoid bacilli and allowed to 

 stand for a time, the bacteria gradually lose their power 

 of motion, begin to clump together in masses which grow in 

 size until finally they settle out, and the medium which was 

 originally cloudy and turbid becomes clear with a fiocculent 

 sediment. Serum from normal individuals usually does not 

 show this power. The substances developed in the blood 

 capable of flocculating bacteria in this fashion were termed 

 agglutinins. 



Somewhat later the independent observation was made 

 that whenever foreign proteins of any kind were injected 

 into an animal, eventually the blood of that animal acquired 

 the property of precipitating the corresponding or homol- 

 ogous protein. For example, if a dilute solution of egg white 

 be injected into the blood stream of a rabbit at suitable 



