170 THE BORDET-GENGOU PHENOMENON 



patient, haemolysis occurred ; it followed, therefore, that the 

 patient's blood contained derivatives of the tubercle bacillus, or 

 (as we may fairly say) its toxins. 



The technique of these experiments is somewhat difficult, but 

 the results have been so important, and the method seems so 

 likely to play a part of importance in clinical diagnosis, that it will 

 be discussed in a further chapter. 



Gengou's phenomenon is similar to Bordet's. It requires a 

 little anticipation of facts to be discussed subsequently concerning 

 the precipitins. These are antibodies obtained by the injection 

 of proteid solutions, and having the power of uniting with these 

 proteids to form insoluble precipitates. Gengou showed that in 

 this combination of antigen and antibody the same absorption of 

 complement occurred as in the case of sensitized red corpuscles 

 or bacteria. The process is an extraordinarily delicate one, and 

 it has been shown to be demonstrable with as little as o-oooooi c.c. 

 of the antigen (in this case normal human serum), and may occur 

 when the serum used is so dilute that no visible precipitation 

 occurs. 



It appears, further, that this process of fixation of complement 

 is a general one, occurring whenever an antigen and its antibody 

 unite, whether the antigen occurs in solid or liquid form, and 

 whether the resulting compound forms a precipitate or remains in 

 solution. It has been shown by Nicolle and by Armand-Delille 

 to occur in the neutralization of tetanus and diphtheria toxins by 

 their appropriate antitoxins, and by Pozerski in the interaction of 

 papain and its antiferment. It has been shown by Guedini that 

 when hydatid fluid is mixed with the serum of an animal which 

 has been injected therewith a similar phenomenon occurs, and 

 this fact has been suggested and applied by Weinberg, Parvu, and 

 Lanbry to the diagnosis of hydatid cysts in man. 



The theoretical importance of this phenomenon arises from the 

 light which it throws on the difficult subject of complementoids 

 and anticomplements. We have seen that heated serum has no 

 complementary activity, but that its injection into suitable animals 

 appears to call forth the presence of anticomplements. A little 

 consideration will show that this apparent anticomplementary 

 action can be explained equally well by the absorption of the 

 complements in a specific precipitate. We will take a particular 

 case. 



Goat serum heated to 56 C., and therefore containing no active 



