THE AGGLUTININS 211 



and is probably a source of error often overlooked : the serum 

 clumps at a high dilution, and not at a low one. The author has 

 observed it three times in the last four years. Another explana- 

 tion, which is probably more often the true one, is that in the low 

 dilutions partial bacteriolysis takes place, and the partly dissolved 

 bacteria do not clump. The reason for this conclusion is that the 

 clumping may occur in low dilutions in the cold, when bacterio- 

 lysis does not take place. Yet other explanations have been 

 given. 



Certain non-specific substances may bring about clumping 

 which has a close superficial resemblance to that caused by 

 agglutinin. This was first showed by Malvoz in the case of the 

 action of chrysoidin on V. cholera. He also showed that certain 

 stains, such as fuchsin, vesuvin, and safranin, and some anti- 

 septics, such as formalin (in fairly large amounts), corrosive 

 sublimate, and peroxide of hydrogen, have this action. Mineral 

 acids also possess this property, and also certain salts. In the 

 case of cholera vibrios, Ruffer and Crendiropoulo found calcium 

 chloride to have a powerful action, sodium phosphate to have a 

 very slight one. This must not be confused with the effect of 

 salts in favouring the action of agglutinating serum. 



We are now in a position to discuss the mechanism of the 

 process. Numerous theories have been propounded. Thus 

 Gruber thought that the external membrane of the bacterium 

 became " sticky," so that organisms once brought into contact 

 remained adherent. But no visible alteration of the organisms 

 or red corpuscles can be seen. Further, it would not account for 

 the approach of two non-motile cells, which certainly appears to 

 take place in clumping, and would not explain why the cells or 

 bacteria were brought into contact in the first instance. Nicolle 

 propounded a similar theory. He, however, showed that when 

 inert and insoluble particles, such as of talc, were suspended in old 

 filtered cultures of typhoid bacilli (Kraus's fluid), and serum 

 added, they appeared to clump just as typhoid bacilli did, and it 

 is difficult to reconcile this with his theory. Dineur thought that 

 the flagella of the bacilli might have an adhesive material 

 deposited on them ; but many non -flagellated bacteria clump, to 

 say nothing of red corpuscles. Others have thought that Kraus's 

 reaction is the fundamental phenomenon, and that the bacteria, 

 etc., are entangled in it . like the particles of talc in Nicolle's 

 experiment. But no obvious precipitate can be seen in stained 



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