CHAPTER VIII. 



THE AOGLUTININS. 



In 1889 Oharrin and Soger* in studying tbe action of the serum 

 of sick and immunized animals on homologous bacteria, observed 

 that the bacillus pyocyaneus behaved pecuiiaily when placed in the 

 serum of an animal which had been immunized to this organism. 

 In the serum of a normal rabbit, this germ was found to grow as it 

 does in beef tea, or other liquid nutritive medium, forming an 

 opaque culture, while in the serum of an immunized rabbit these 

 microbes were found to form small floating floccules which soon sub- 

 sided, leaving a clear, supernatant fluid. It was furthermore ob- 

 served that the germ grown in its homologous serum does not pro- 

 duce pyocyanin, while in the serum of normal animals this coloring 

 matter is formed by the growth of the bacillus. The sera of ani- 

 mals sick from inoculation with the bacillus pyocyaneus, and of 

 those immunized against this germ, were observed to have the same 

 effect on its growth. This early observation indicated, as has been 

 subsequently more clearly shown, that the phenomenon of aggluti- 

 nation is a reaction of infection as well as of immunization. 



In his studies on immunity, Metchnikoff,^ found that the vibrio 

 which bears his own name behaves in a manner similar to that ob- 

 served by Charrin and Roger with the bacillus pyocyaneus. On 

 this point Metschnikoff makes the following statement : " In the 

 blood and serum of non-vaccinated guinea-pigs the vibrio develops 

 as it does in ordinary liquid media, the individual organisms retain- 

 ing their motility and remaining distinct one from the other. On 

 the other hand in the blood and serum of vaccinated animals the 

 vibrios become immobile, and form smaller or larger floccules which 

 float in the liquid." 



In 1893 Issaeff"^ observed a like phenomenon when the pneumo- 

 coccus was placed in its homologous serum, and this observation was 

 repeated later in the studies on immunity prosecuted by the same 

 author in conjunction with Ivanoff".* In the last-mentioned com- 

 munication there is found the following statement : " In the blood 

 serum of healthy, non-immunized guinea-pigs the vibrio develops 

 rapidly, and after from four to five hours at 37° there is a uniform 



' Omipteg Rendus de VAcademie cfes Seienees, 109. 

 ^Annales de VInaiUvi Pastewr, 5, 1891. 

 ' Annaki de V InstUut Paatew, 7. 

 * Zeitschrift fur Hygiene, 17. 



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