PATHOGENIC BACTERIA 133 



In 1896 Widal and Griinbaum, working separately, devel- 

 oped what is now spoken of as the "Widal serum test," or 

 "Widal reaction." It consists in testing a drop of blood of a 

 patient suspected of having typhoid fever, by mixing a dilution 

 of it with a drop of a fresh bouillon culture of typhoid bacilli, 

 and examining the mixture in a hanging drop under the micro- 

 scope. Within fifteen minutes to an hour the motility of the 

 bacilli will cease, and they will have arranged themselves into 

 clusters, as if stuck or glued together. If this reaction occurs 

 within an hour, and with the proper dilution of the serum, the 

 case is one of typhoid. Widal first used the serum of the blood; 

 this has been modified so that even a drop of dried blood is suf- 

 ficient. The method as applied in city laboratories is as follows : 

 The physician is told to clean the finger of the patient with 

 water (no germicides), and with a needle draw a drop of blood 

 on to a piece of ordinary note-paper. This is then sent to the 

 laboratory; the paper with the dried blood is soaked for a few 

 minutes in a watch-glass containing 4 drops of clean water, thus 

 obtaining a dilution of i 15. One drop of this is then mixed 

 with one drop of a bouillon culture of typhoid bacilli of about 

 twenty-four-hours' growth, and examined under the microscope 

 in the hanging drop. Weaker dilutions of the serum have been 

 recommended (i 150), and this should be used in cases of 

 doubt. So far, about 95 per cent, of the cases examined, and 

 which clinically were considered typhoid fever, have given a 

 positive reaction. It is not often present until the fifth day of 

 the fever, and disappears usually within a year, though in some 

 individuals it has been found ten years after an attack of the 

 disease. 



The agglutinating properties have been found in nearly all 

 the secretions of the body tears, urine, milk, pleuritic effusions, 

 serous fluid from blisters, etc. 



There is no relation between the reaction and the bactericidal 

 power of the serum; the agglutination is not a destruction. The 

 agglutinating power is active, though the blood be dried and 

 sealed up for months. It seems to have no direct relation with 

 the question of immunity, since it occurs at the height of the 



