A (jglvtf nation Test in Abortion. 379 



3. Quantitative Factors in the Agglutination 

 Reaction. 



(rt) Not simply a matter of dilution, but a quantitative reaction^ 

 An unfortunate terminology has crept into descriptions of agglu- 

 tination methods — probably a relic from the descriptions of the 

 so-called Widal reactions with the serum of typhoid patients — in 

 which frequent use is made of the term " dilution," to express 

 the amounts of serum (or other diagnostic fluid) necessary to bring 

 about agglutination. 



The following experiments show that the sensitiveness of the re- 

 action is to be measured by accurate determination of the minimal 

 quantity of serum employed; in other words, it is not simply a 

 matter of dilution, but a quantitative reaction. 

 Experiments. — To determine whether — 



1. The relation of the quantity of pure serum to the quantity 



of fluid in a tube (i.e., degree of dilution), or 



2. The amount of pure serum in the tube, 



is the determining factor in agglutination of a particular serum. 



Serum collected from a cow thirteen days previously was used, a 

 basal dilution of 1 of serum to 49 of carbolised saline being made 

 (1 in 50). 



The emulsion was standardised in accordance with the usual 

 method, and found to lie of a standard " 10 X." 



Set la. 

 Ten tubes were put up, as follows : — 



A. B. C. 0. K. F. G. H. J. K. 



Serum (1 in 50) - 1.0 1.0 1.0 1.0 1.0 0.5 0.5 0.5 0.5 0.25 c.c. 



Carbolised saline - 0.0 0.5 1.0 1.5 2.0 1.25 1.5 2.0 2.5 1.75 c.c. 



Total volume - - 1.0 1.5 2.0 2.5 3.0 1.75 2.0 2.5 3.0 2.0 c.c. 

 Eelationship of serum 



to fluid- - lin 50 75 100 125 150 175 2(X) 250 300 400 



Of each of these dilutions 1 c.c. was put in a tube, and the tubes 

 similarly lettered so tliat the amounts of pure serum in these tubes 

 were : — 



A. B. C. I). K. K. U. H. .1. K. 



0.02 0.012 0.01 O.OOS O.OOG 0.0056 005 0.004 0.0(J3 0.0025 c.c. 



Emulsion (0.05 c.c. Standard 10 X) was then added to each tube 

 and tlie tubes incubated till next day, when readings were taken. 



