252 PHARMACEUTICAL BACTERIOLOGY 



It is known that tissue cells react more or less specifically with bacterial 

 toxins and these reactions are used for making certain diagnostic tests, 

 such as the skin reaction tests for tuberculosis, glanders, syphilis, diph- 

 theria and typhoid fever. 



d. Antitoxins. The antitoxins are the substances found in the body 

 cells and in the blood plasm which neutralize or destroy the toxins and 

 toxoids of pathogenic bacteria. As has already been explained, when a 

 pathogenic organism is introduced into the body, the lysins destroy the 

 cell membrane, setting free the endotoxins which by their presence stimu- 

 late the formation of the antitoxins. The antitoxins are specific in nature. 

 Tha,t is, the antitoxin against the diphtheric endotoxin is not active 

 against the toxin of typhoid, or of plague. 



e. Anti-antitoxins. It is known that the normal bodily resistance 

 to disease varies from time to time and that the artificial immunity due 

 to the introduction of specific antibodies gradually wanes and finally 

 disappears. This variability in the action of antibodies is supposed to 

 be due to substances, again specific in character, in the body cells and in 

 the blood plasm, which destroy the antibodies. 



/. Agglutinins. Agglutinins are specific cellular products which cause 

 bacteria to clump or gather into groups, preceded by a cessation in motion 

 in those organisms which possess motility. The Widal typhoid fever 

 test is based upon this phenomenon. 



Agglutinins are produced artificially by injecting bacteria into the 

 circulation of various animals. The serum of such animals contains the 

 bodies which give rise to the agglutinating phenomena. Sera can be 

 so highly agglutinative as to produce this reaction in dilutions of 1-100,000 

 or more. In typhoid patients the agglutinins generally appear after 

 the fifth day and may persist for a long time (several years) after con- 

 valescence. By some it is supposed that the phenomenon of agglutination 

 is a preliminary stage in the development of lysins. It is however a fact, 

 that while the bactericidal action of serum is destroyed at a temperature 

 of s6C., the agglutinating power survives until 62C. is reached. Bacteri- 

 cidal sera do not interfere with the agglutinating power. These and other 

 observations appear to indicate that the agglutinins are specific bodies 

 independent of the other immunizing agents. 



g. Precipitins. Precipitins are specific bodies which occur in the 

 blood of an immunized animal, as rabbit or guinea pig. If, for example, 

 a rabbit is immunized against human blood (through repeated injections 

 of human blood directly into the circulation of the animal) and the serum 

 of such immunized blood be mixed with a trace of human blood, a precipi- 

 tate is formed. The reaction is strictly specific, excepting that the blood 

 immunized against a sheep will form precipitate with the blood from the 



