9 223 



The culture — B. coli for example — mentioned at the head of the several 

 columns, is the culture used in that vertical series of experiments; the agglutinating 

 serum used is the corresponding one — a B. coli immune-serum in the above case — 

 in every instance. 



B. The age of the bacterial culture. 



The length of time for which the culture has grown in the incubator at 37° 

 has considerable influence upon the results obtained when it is agglutinated. 

 BossAERT was the first to concern himself with the influence of its age upon the 

 agglutinability of the bacterial culture. Our own researches shew that the age of 

 the culture is of the greatest importance when a bouillon-culture is used, but that it 

 has comparatively little influence upon the agglutinability of agar-culture suspensions. 

 Thus the figures given in Table I, Series 1 to 5, shew that the suspensions made 

 from agar-cultures of different ages are more or less equally agglutinable (see 

 Series 1, column R. A.), while bouillon-cultures become very considerably less so as 

 they grow older; for example, a 12-day bouillon growth is only one sixteenth as 

 agglutinable as a 24-hour culture (see Series 3, column R. A.), the former requiring 

 16 times as much serum to produce a given degree of agglutination as the latter. 

 This diminution in agglutinability seems to be mainly if not exclusively due to the 

 development , during the growth of the bacteria in the bouillon , of certain sub- 

 stances (the "toxine") which can unite with the agglutinine of the serum and so 

 prevent it from uniting with the agglutinable substance of the bacteria; when large 

 quantities of agglutinine are present, the "toxine" can be precipitated. That sub- 

 stances with the above properties are formed in old cultures of B. coli communis 

 and B. typhosus was first observed by Kraus in 1897, and they have been described 

 since then by Radziewsky, Wassermann, and others. 



The proportions in which the bacterial toxine and the agglutinine of the 

 immune-serum combine together, on the other hand, have not yet, to the best of 

 our knowledge, been subjected to investigation. 



It is quite otherwise with the combinations between bacteria and agglutinines, 

 since these have been the objects of the very extensive and illuminating inv£.stig- 

 ations of Eisenberg «& Volk. These authors have shewn that if increasing quanti- 

 ties of an agglutinine are added to a constant amount of bacterial emulsion, the 

 absolute absorption of agglutinine increases while the coefficient of absorption — 

 that is to say the relation between the quantity of agglutinine that is absorbed and 

 the quantity that was originally present — diminishes. The figures given by Eisen- 

 berg & Volk have been made use of by Arrhrnius, who finds that the relation 



1). K. 1) Vidensk. Selsk. Ski-., 7. R^ukke. nutiiiviilL-nsU- o;,' m;illiuin. Al'il. ] i. 30 



