Page:Defensive Ferments of the Animal Organism (3rd edition).djvu/201

 It is sufficient to use 15 to 20 c.c. of blood. For sending away, only serum should be used which has been centrifuged completely. The latter must in any case be centrifuged again. The serum should not be more than twelve hours old, even though it has been collected and preserved in a really sterile way. The taking of the blood, its collection, and its manipulation must be done aseptically. In carrying out a dialysation test the following fundamental rules must be obeyed, of which not one is unimportant:—

(1) Extreme cleanliness is the first condition for ensuring success in the experiment. This applies to the surroundings, and to all the utensils employed. Pipettes, test-tubes, Erlenmeyer flasks, &c., must be thoroughly cleansed and absolutely dry.

(2) The water used must be thoroughly sterilized distilled water. So-called distilled water often proves to contain numerous germs of every description. If one uses water like this as the outer fluid in dialysis, then the way is laid open for all kinds of mistakes.

(3) The work is performed, as far as possible, aseptically and antiseptically.

(4) In the room in which the experiments are in progress neither bacteriological nor chemical work should be allowed. Above all, an incubator must be