ction of the medium mass; control the
result. Calculate the amount of soda solution required to make the
reaction of the medium mass + 10 (i. e., calculated for 1000 c.c.,
less the quantity used for the titrations).

8. Add the necessary amount of soda solution and replace in the steamer
for twenty minutes (to complete the precipitation of the phosphates,
etc.).

9. Allow the medium mass to cool to 60 deg. C. Well whip the whites of
two eggs, add to the contents of the flask, and replace in the steamer at
100 deg. C. for about _one hour_ (until the egg-albumen has coagulated
and formed large, firm masses floating on and in clear agar.)

10. Filter through papier Chardin, by the aid of a hot-water funnel, if
necessary (Fig. 101), into a sterile flask.

11. Tube in quantities of 10 c.c. or 15 c.c.

12. Sterilise in the steamer at 100 deg. C. for thirty minutes on each of
three consecutive days--i. e., by the discontinuous method.

~Blood-serum (Inspissated).~--

1. Sterilise cylindrical glass jar (Fig. 109) and its cover by dry heat,
or by washing first with ether and then with alcohol and drying.

2. Collect blood at the slaughter house from ox or sheep in the sterile
cylinder.

3. Allow the vessel to stand for fifteen minutes for the blood to
coagulate. (This must be done before leaving the slaughterhouse,
otherwise the serum will be stained with haemoglobin.)

4. Separate the clot from the sides of the vessel by means of a sterile
glass rod (the yield of serum is much smaller when this is not done),
and place the cylinder in the ice-chest for twenty-four hours.

5. Remove the serum with sterile pipettes, or syphon it off, and fill
into sterile tubes (5 c.c. in each) or flasks.

6. Heat tubes containing serum to 56 deg. C. in a water-bath for half an
hour on each of two successive days.

7. On the third day, heat the tubes, in a sloping position, in a serum
inspissator to about 72 deg. C. (A coagulum is formed at this temperature
which is fairly transparent; above 72 deg. C., a thick turbid coagulum is
formed.)

[Illustration: FIG. 109.--Blood-serum jar with wicker basket for
transport.]

The serum inspissator (Fig. 110) in its simplest form is a double-walled
rectangular copper box, closed in by a loose glass lid, and cased in
felt or asbestos--the space between the walls is filled with water. The
inspissator is supported on adjustable legs so that the serum may be
solidified at any desired "slant,