242 28 



Slill, Tables XXVIII and XXIX shew that the actual destruction of the acidified 

 immune-serum's agglutinating power is greater if bouillon-culture is employed for the 

 measurements than when an agar-culture suspension is used. 



If a bouillon-culture is made use of, one does nol observe an increase in the 

 serum's agglutinaling power, as may be the case when a suspension is made the 

 subject of the experimenl. As has already been pointed oui, this is because a 

 bouillon-culture is not readily agglutinated by an acid, so that the minute quantities 

 of acid that have come into play are unable to produce an apparent increase in 

 the serum's capacity for producing agglutination. 



The experiments suffice to shew (hat also in the case of bouillon-cultures, the 

 extent of the "zones of inhibition' observed does not depend upon the actual destruction 

 of the agglutinine that has taken place, the limits of the "zone" are determined by 

 the presence of jusl such an amount of acid in the luJ)es where il occurs as will 

 prevent the bacteria from coming together, and bear no relation to the slrenglh of 

 the acid to which the serum was exposed. 



In conclusion we shall give a l)rief account of the experimenis we have made 

 that illustrate : 



G. The action of alkalies upon the process 



of agglutination. 



We have never been able lo find that solutions of caustic soda {Na OH) have 

 any agglutinating influence upon our stocks of 13. coli or B. typhosus, whether 

 added in large quantities or in small. Like other experimenters however, we have 

 observed that even when added lo the bacterial emulsion in relatively small 

 quantities, the alkali renders it more translucent. It appears that B. coli suspen- 

 sions, to which regularly increasing amounts of caustic soda have been added just as 

 acid was added in experiments already described, lose much of their power of being 

 agglutinated by immune-serum: the agglutinability grows progressively less as in- 

 creasing quantities of the alkali are added. But such experiments as we have 

 made in this direction have failed lo bring lo our observation any such irregularities 

 in Ihe agglulinalion, or any of the "zones of inhibited agglutination" thai are of 

 such frequent occurrence when acid is here made use of. With the alkali, diminish- 

 ing amounts of the immune-serum always produce diminishing degrees of agglut- 

 ination. 



Acting upon the agglutinine of B. coli immune-serum, caustic soda is far more 

 destructive than is an equimolecular solution of hydrochloric acid. For example, HCl 



