THE AGGLUTWISS. 161 



There have been proposed several hypotheses concerning the phe- 

 nomenon of a^latination- Graber su^ested that there most be 

 something in the immune serum which profonndlv alters its homolo- 

 gous bacterium. This alteration consists, in part at least, in in- 

 creased viscosity of the ceU membrane of the bacterium- The pro- 

 duction of ihe adhesive substance is supposed to be the chief fiictor 

 in the agglutination or clamping of the bacterial cells. When two 

 or more germs are brought together, either by active or passive move- 

 ment, they adhere one to the other, lose their individual motility and 

 form small mass^ which gradually subside in the culture medium. 

 According to XicoUe, the a^lutinin, which is furnished by the serum, 

 precipitates the agglutinable substance, which is formed within the 

 bacterial cell, from which it diffuses through the culture medium to 

 a greater or less extent. The a^lutinable substance is supposed to 

 be most abundant in the cell membrane, and by the union of the ag- 

 glutinin and the a^lntinable substance small coagula are formed and 

 surround the bacterial cells. The theory proposed by Paltauf varies 

 but slightly from that suggested by Xicolle. However, the former 

 supposes that the combination between the agglutinin and the agglu- 

 tinable substance occurs wholly outside of the bacterial cells and that 

 the microorganisms are involved in the floccules mechanically only. 

 The hypothesis of Dineur varies from that originally proposed hj 

 Gruber only by transferring the formation of the adhesive matter 

 from the bacterial cell walls to the ciha. Diminished motility and 

 subsequent a^lutination are explained on the supposition that the 

 cilia are so altered that they secrete an adhesive sul^tance. In 1896 

 Bordet suggested a hypothesis in which he attempted to explain the 

 phenomenon of agglutination wholly upon physical grounds. He 

 suggested that in homologous sera there is present a substance or 

 substances which change the relative molecular attraction between 

 the microbes and the ambient fluid. Later Bordet developed this 

 theory as we have already indicated in our discussion of the lysins. 

 In accordance vrith the general trend of French thought along these 

 lines, he has rejected the German idea of chemical reaction and thinks 

 that the problem is to be solved in accordance with the laws of 

 physics. As we have seen in a preceding chapter, Bordet supposes 

 that both in a^lutination and in bacteriolysis there is a substance in 

 the serum which renders the blood and bacterial cells sensitive to the 

 action of a ferment. This substance he calls the sensitizer, and he 

 states that the phenomenon of a^lutination is si mila r to that of co- 

 agulation, and in explaining the latter he endeavors to exclude the 

 necessity of the presence of bodies which have other than physical 

 action. 



11 



