ontains 0.1 c.c. of the original
serum).

When dealing with fluids other than serum the diluent is usually
distilled water; whilst if the original substance is a solid the
instructions would read:

1 gram o.s. + 10 c.c. distilled water = 10 per cent. solution, etc.

SECOND DILUTION--II.

1 c.c. first dilution + 9 c.c. normal saline solution = 1 per cent.
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.

TABLES FOR PREPARING DILUTIONS.

-----------------------------------+----------------------------------
|
TABLE I | TABLE II
Using 10 % stock solution | Using 1% stock solution
First } | Second }
dilution } + Diluent | dilution } + Diluent
|
-----------------------------------+----------------------------------
|
1: 10 = 1 c.c. + 0 c.c. | 1: 100 = 1 c.c. + 0 c.c.
1: 15 = 1 c.c. + 0.5 c.c. | 1: 110 = 1 c.c. + 0.1 c.c.
1: 20 = 1 c.c. + 1.0 c.c. | 1: 120 = 1 c.c. + 0.2 c.c.
1: 25 = 1 c.c. + 1.5 c.c. | [1: 125 = 1 c.c. + 0.25 c.c.]
1: 30 = 1 c.c. + 2.0 c.c. | 1: 130 = 1 c.c. + 0.3 c.c.
1: 35 = 1 c.c. + 2.5 c.c. | 1: 140 = 1 c.c. + 0.4 c.c.
1: 40 = 1 c.c. + 3.0 c.c. | 1: 150 = 1 c.c. + 0.5 c.c.
1: 45 = 1 c.c. + 3.5 c.c. | 1: 160 = 1 c.c. + 0.6 c.c.
1: 50 = 1 c.c. + 4.0 c.c. | 1: 170 = 1 c.c. + 0.7 c.c.
1: 55 = 1 c.c. + 4.5 c.c. | [1: 175 = 1 c.c. + 0.75 c.c.]
1: 60 = 1 c.c. + 5.0 c.c. | 1: 180 = 1 c.c. + 0.8 c.c.
1: 65 = 1 c.c. + 5.5 c.c. | 1: 190 = 1 c.c. + 0.9 c.c.
1: 70 = 1 c.c. + 6.0 c.c. | 1: 200 = 1 c.c. + 1.0 c.c.
1: 75 = 1 c.c. + 6.5 c.c. +---------------------------------
1: 80 = 1 c.c. + 7.0 c.c. | 1: 200 = 1 c.c. + 1.0