solution or 1: 100 dilution.
THIRD DILUTION--III.
1 c.c. second dilution + 9 c.c. normal saline solution = 1 per mille solution or 1: 1000 dilution.
FOURTH DILUTION--IV.
1 c.c. second dilution + 9 c.c. normal saline solution = 0.1 per mille solution or 1: 10,000 dilution.
The following tables showing the secondary dilutions that can readily be prepared from each of these four primary dilutions for use in the subsequent determination of the exact _titre_ will probably be found of service by those who are not ready mathematicians.