882 H. R. Seddon: 



Conclusio/is to be drawn from ((bore. 



1.— Using the same quantity of emulsion in eacli tube, tube^ 

 2^ossessurg the same ddvtion {but different quantities) of serum do 

 uot furnish parallel results. (Compare Set la. with Set Ila., Set 

 lb. and Set lib., etc.) 



2. — Using the same quantity of emulsion in each tube, tubes 

 containing/ the same qtiantit/j of serum do furnish parallel results. 



3. — The agglutination titre varies with the quantity of emul- 

 sion used, for, as is evident in the table (I.) — - 



(a) With 0.05 c.c. of concentrated emulsion (10 X), the 



minimum amount of this serum which will produce 

 agglutination is 0.006 c.c. 



(b) Witli 0.1 c.c. of concentrated emulsion (10 X), the mini- 



mum quantity of serum required is 0.02 c.c. 

 Experiments were then carried out to test the effect of dilution 

 on an agglutination system. 



Tubes were put up, containing : — 



Test 1. — Volume of fluid in each tube made up with carbolised 

 saline to 1 c.c. 



Test 2. — Volume of fluid in each tube made up to 2.5 c.c. 

 Results, both tests : — 



A and B, agglutination and clearing. 



C, agglutination. 



D, no agglutination. 



Test 3. — A tube was put up, containing 0.02 c.c. pure serum 

 and 0.05 c.c. emulsion (10 X), and carbolised saline added tip to 

 20 c.c. 



Result : — Agglutination. 



These tests show that the dominating factor is the quantity of 

 serum in each tube, and not the degree of dilution. Of course, if 

 equal quantities of each dilution be taken for testing, the quantity 

 of serum in the tube will vary as the dilution (as is shoAvn in Set 

 la.). On the other hand, in the practical application of the agglu- 

 tination test the important figure is what may be termed the " end- 

 point " — i.e., the smallest quantity of serum which will produce 

 agglutination witli n standard quantity of emulsion. The neces- 

 sity, therefore, arises for taking for all tests an exactly similar 



