132 ESSENTIALS OF BACTERIOLOGY 



About 1889, Charrin and Roger observed in the serum of 

 immunized animals that the Bacillus pyocyaneus arranged 

 itself in little clumps. Other investigators reported the same 

 thing for other bacteria, and Metchnikoff added that motility 

 was destroyed. 



In 1895 Bordet showed that the serum of cholera-immunized 

 animals, when mixed with bouillon cultures of cholera spirilla, 

 affected their motility and caused them to form masses, or 

 "Klumpen," as the Germans call it. 



Fig. 69. The Widal agglutination reaction (Slater and Spitta). 



R. Pfeiffer, in the same year, showed that the introduction of 

 immune serum at the same time with virulent cholera spirilla 

 into the peritoneum of guinea-pigs, prevented infection from 

 taking place, and the spirilla were transformed into granular 

 masses. He likewise showed this reaction to be specific, the 

 serum of cholera-immune animals acting only on cholera 

 vibrio, and hence he suggested using the serum as a means 

 of diagnosis for the cholera vibrio and typhoid bacillus. Gru- 

 ber about the same time made some studies upon the use of 

 this serum property in differentiating bacteria, but it was con- 

 sidered as yet a property connected in some way with immunity. 



